STUDIES OF THE COASTAL MARINE FAUNNA OF SOUTHERN SINALOA, MEXICO. II. THE DECAPOD CRUSTACEANS OF ESTERO EL VERDE

Trabajo recibido el 3 de septiembre de 1982 y aceptado para su publicación el 24 de marzo de 1983.

RESUMEN

INTRODUCCIÓN

When compared to the rest of the Gulf of California, the invertebrate fauna of the coastal area extending from Guaymas, Sonora, to Mazatlan, Sinaloa, is poorly known. In particular, the fauna inhabiting the littoral bodies of water (coastal lagoons, esteros and estuaries), has been studied from only a selective point of view, priority being given to commercially important species only. A similar situation is to be found south of Mazatlán which has long been considered the southern biogeographic mainland limit of the Gulf by various authors (Glassell, 1934; Garth, 1960; Thomson et al.1979; Brusca, 1980) . Regarding this last point, it should be stressed that in the present study, the Gulf of California region has been considered as the area extending north of a line drawn between Cabo San Lucas, Baja California Sur, and Cabo Corrientes, Jalisco, thus, following a pattern based on the tectonical structure of western Mexico continental shelf (Parker, 1963; van Andel, 1964) . This is due to the fact that, in the author's opinion, the theory of the existence of a biogeographic barrier located at the latitude of Mazatlan is based on too inconsistent information regarding the distribution of decapod crustaceans fauna in the southeastern Gulf area, i.e. from Guaymas, Sonora to Cabo Corrientes, Jalisco.

From Mazatlán south to the State of Chiapas,the coastal climate progressively becomes more humid than in the Gulf and large coastal lagoons (e.g. Agua Brava) are to be found, the invertebrates fauna of which is almost unknown. Together with the continuous series of coastal lagoons and small river deltas extending southward from Guaymas to Mazatlán, thesse large lagoonal system have often been reported as supporting a little diversified invertebrate fauna (Chipa and Soto, 1969; Findley, 1976; Edwards, 1978). In some cases, however, this seems to be due fundamentally to the lack of attention paid to the local fauna, particularly the fauna associated with mangrove forest.

Because the development of marine biological research on the Pacific coast of Mexico is relatively recent, the occurrence and the distribution of almost all species of decapod crustaceans in the area is poorly known and all too often, very common species are referred to only at generic or family level and are sometimes misidentified.

To improve our knowledge of the crustaceans of the area of Mazatlán (van der Heiden and Hendrickx, 1982; Hendrickx, and van der Heiden, in press a survey of a small coastal lagoon (Estero EI Verde) located approximately 30 kilometers north of Mazatlán was undertaken in 1978. A list of decapod crustaceans occurring in the area is presented herein with some notes on their ecology and keys for their identif ication.

This is the second of a series of publications dealing with the study of the marine and brackish fauna of the area of southern Sinaloa, México.

In order to obtain environmental information of the study area, monthly field trips were made to Estero EI Verde for a period of approximately two years (1978-1980) and occasional visits were also made between 1980 and 1983. Special attention was given to features such as the dominant flora, the tidal movements and the variety of habitats available to the local fauna. Thus, a brief description of the area was realized by comparing the personal observations obtained during the survey with studies made in other areas (Macnae, 1968; Phleger, 1969; Rollet, 1974; CarIton, 1975; Correll and Correll, 1975; Crane, 1975; Abele, 1976; Findley, 1976).

The decapod crustaceans reported in the present paper were all collected in the Estero EI Verde system between january 1978 and july 1980. Sampling was usually done by hand, with the help of shovels and a hand net, but a small bottom dredge was occasionally used in the channels (Schlieper, 1972). Specimens were fixed in the field and identified in the laboratory, although with increasing knowledge of the species collected, many organisms were identified upon capture and released at their point of capture.

Identification of the animals was done using the basic literature available for each group of decapod crustaceans (Rathbun, 1918, 1930; Holthuis, 1952; Pérez-Farfante, 1970; Williams, 1974; Crane, 1975; Brusca, 1980) and when necessary, by comparing the species obtained with those of the crustacean collection of the Allan Hancock Foundation, University of Southern California, Los Angeles.

Specimens of all collected species have been incorporated into the reference collection of marine and brackish water invertebrates of the Marine Station of Mazatlán, Instituto de Ciencias del Mar y Limnologia, Universidad Nacional Autónoma de México, in Mazatlán, Sinaloa, México.

The estero EI Verde is located about 30 kilometers north of Mazatlán. Although its total area is only about 2 km², it has the typical structure of a coastal lagoon as described by Phleger (1969). In a preliminary review of the common marine invertebrate fauna of southern Sinaloa, Hendrickx and van der Heiden (in press, a), underlined the fact that there exist some confusion in the utilization of the term "estero". In Sinaloa, "estero" is often used as a local name for coastal lagoons (e.g. Estero EI Verde) or a par of a coastal lagoon system (e.g. estero de Lechuguilla, Topolobampo). In some cases, though, it designates a channel which connects a coastal lagoon to a river (e. g. estero Agua Dulce in the HuizacheCaimanero Lagoon). In the present paper, the name "Estero EI Verde" has been kept as a designation for the study area in order to avoid confusion. It should be kept in mind, however, that the system is a coastal lagoon.

The Estero EI Verde is composed of one small inlet and two main channels running parallel to the coast line. It is almost entirely bordered by mangroves. In its middle part, almost opposite the inlet, the rio Quelite constitutes the river channel of the system (Fig. 1 and Plate 1, A-B-C-D).

The two main channels are cut by two wood en made "tapos" (some type of weirs) which are completely closed after penacid shrimp postlarvae have entered the system (see Plate 1, A), thus preventing grown organisms to escape (Menz, 1976; Edwards, 1978).

The most extensive mangrove stands are found in the area where the river meets the southern lateral channel and the whole system is widely dominated byLaguncularia racemosa(L.) with only a few scattered patches of Rhizophora mangleL., andConocarpus erecta L.

Other typical vegetation includes the salts crubs Salicornia asp., and Batis maritima L., which grow on uncovered flats during the dry season together with the very typical circularshaped patches ofTrianthema portulacastrum L. The submerged vegetation of the channels includesRuppia maritimaL., andEnteromorpha intestinalis (L.) which are both abundant in the inlet delta when the water level reaches its minimum at the end of the dry season.Enteromorpha intestinalis also grows on the muddysand bottom of the channels.

The system is connected to the sea by means of a single inlet which is closed by a sand bar for most of the year. During the rainy season (June to October) the combined effects of the river flow and the tides (which reach their maximum amplitude in the rainy season) destroy the sand bar and keep the inlet open for a period of approximately between 2 and 4 months. For several years, however, the opening through the sand bar has been artificially initiated by the local fishermen (Briseño-Dueñas, 1980). As a consequence of this annual opening of the sand bar, the system has two drastically different periods:

Fig. 1. Map of the estero EI Verde (23° 25´30" N-106°33´ 30" W) showing the main parts of the system angrove stands.

1.A period of open bar, between the end of June to the end of October, when the rio Quelite swollen by the rain, washes open the sand bar and flows directly into the sea. The occurrence of extremely high tides during this short period, gives the system characteristics of an estuary.

2.A long period of closed bar, corresponding roughly to the dry season and during which evaporation is the only factor affecting the water level which falls gradually until the period of May-June when the water level increases rapidly due to heavy rains in the Sierra.

A total of 12 different habitats has been considered for the study area, their definitions being partly based on those of Crane (1947, 1975): (1) Unprotected sandy beach extending seawards, all along the estero; (2) Dunes and shaded dunes; (3) A narrow discontinuous line of mangrove bordering the channel; (4) Mud in full shade of mangrove; (5) Muddy sand to mud, partly shaded by mangrove; (6) Open mud flat near mangrove; (7) Muddy stream banks or flats, distributed unevenly along the estero, bordered by mangrove or other vegetation; (8) Same as 7 but with steep banks; (9) Same as 7 and 8 but upstream, away from mangroves; (10) Muddy sand banks, unshade, bordering the inlet delta water; (11) Channel waters, shallow to 4 meters depth; (12) Inlet delta water: shallow muddy sand bottom.

A total of 31 species of decapod crustaceans has been found inhabiting the area, occupying all habitats previously listed. These species are reported below in taxonomic order (classification of Borradaile modified by van der Heiden and Hendrickx in accordance to Glaessner) (Glaessner, 1969; I.C.Z.N., 1964; van der Heiden and Hendrickx, 1982), together with information on their habitats, ecology and known geographical distribution. Generic-level identification keys are provided for the Natantia and Brachyura. In addition, keys to the species are provided whenever a genus comprises of two or more species in the area.

TABLE 1 CHECKLIST OF THE SPECIES OD DECAPOD CRUSTACEANS OCCURRING IN THE ESTEREO EL VERDE

TABLE 2 DATES OF COLLECTION OF OVIGEROUS FEMALES OF DECAPOD CRUSTACEANS IN THE ESTEREO EL VERDE

A checklist of all species recorded is given in Table 1, while ovigerous females that have been collected or observed during this survey have been listed in Table 2 with respective dates of capture. Several new size records have also been reported and will be found in Table 3. The abbreviations c.l. and c.w. used in this text refer to carapace length and carapace width respectively.

DECAPODA NATANTIA KEY TO THE GENERA OF NATANTIA IN THE ESTERO EL VERDE

1. Lateral portion of the second abdominal segment overlapping the first one2

Lateral portion of the second abdominal segment not overlapping the first onePenaeus

2. Eyes completely covered by carapaceAlpheus

Eyes fully exposed3

3. Hepatic spine absent. Mandible without a palpPalaemonetes

Hepatic spine present. Mandible with a 3 jointed palpMacrobrachium

Palaemonetes (Palaemonetes) hiltoni Schmitt, 1916 Glass shrimp; moya. (Fig. 2, B)

A total of 11 specimens ofPalaemonetes (P.) hiltonihas been collected in the estero, including 9 ovigerous females. Specimens were captured among seagrass in the inlet delta water (habitat 12) and in the river channel and the north channel (habitat 11), in 0.4 to about 1 meter of water. Salinity ranged from 20 to 22 ppt.

The reference collection also includes a series of specimens collected in 1978 by A. Menz in one of the esteros of Caimanero Lagoon, located south of Mazatlan. This rare caridean shrimp was reported by Holthuis (1952) as occurring in estuaries of the State of Sinaloa, México.

Type locality: San Pedro, Los Angeles, California (Holthuis, 1952).

Range: San Pedro, Los Angeles, California, to Sinaloa, México (Holthuis, 1952). Range on the mainland side of the Gulf of California is now defined more accurately as Guaymas, Sonora, south to Caimanero Lagoon, Sinaloa.

Macrobrachium tenellum(Smith, 1869) Fresh-water shrimp; langostino; cauque. (Fig. 2, A)

Several small size specimens were collected in july 1979 in the same habitats as Palaemonetes hiltoni. Although no fully mature males (maximum carapace length: 24 mm) or ovigerous females were obtained, individuals were abundant in the area and collected in habitat 12. The species is reported by Holthuis (1952) as a fresh-water species, but was presently collected in water with a salinity slightly higher than 22 ppt.Macrobrachium tenellum is the only species of fresh-water shrimp found in the Estero EI Verde, although four other species (M.americanum Bate; M. digueti(Bouvier); M. occidentale Holthuis; and.M. acanthochirusVillalobos) occur in other esteros and estuaries in southern Sinaloa (Hendrickxet al., 1983). Type locality: Polvón, western Nicaragua (Holthuis, 1952).

Range: Lower California, Mexico to northern Perú (Holthuis, 1958).

Fig. 2. Lateral view of carapace of the species of Palaemonidae. A: Macrobrachium tenellum (female; c.l. 35.0 mm); B: Palaemonetes Hiltoni (ovigerous female; c.l. 10.8 mm).

Only one specimen ofAlpheus mazatlanicus has been collected in the Estero EI Verde, but this species is reported as common in coastal lagoons of southern Sinaloa (Hendrickxet al. 1983; Wicksten, 1983), where it lives on flat banks and shallow muddy sand bottoms. The specimen found in the estero EI Verde was caught with a bottom dredge at about 1 m.

Type locality: Laguna Caimanero, Sinaloa.

Range: The species is presently known only from southern Sinaloa, in coastal lagoons, from Estero et Verde south to Laguna Caimanero (22° 55´ N). Two paratypes are from estero de Urias, Mazatlán (Wicksten, 1983).

TABLE 3 NEW SIZE RECORDS FOR SPECIMENS OF THE GENUS UCA FOUND IN THE STEREO EL VERDE

PenaeusWeber

Four species of the genusPenaeus are reported from the Gulf of California, three of which occur in Estero EI Verde and in other esteros and coastal lagoons of southern Sinaloa. The fourth species,P. brevirostrisKingsley (the red or crystal shrimp), is predominantly an offshore species (Soto, 1969) .

The fishery for penaeid shrimps in the study area is presently supervised by the J. M. Canizalez Cooperative. The capture for the period 1979-1980, however, has apparently been insignificant.

KEY TO THE SPECIES OF PENAEUS FROM ESTERO EL VERDE

1. Rostrum continued backward as a short carina which stops at about the level of the epigastric tooth. Rostrum with 2-5 ventral teeth and 8-10 dorsal teeth. (Litopenaeus) .........2

2 Rostrum continued backward as a long carina extending posteriorly much further than the epigastric tooth.

Rostrum with 2-3 ventral teeth and 8-11 dorsal teeth , four of which sit on the carapace proper.......... P. californiensis

2. Rostrum with 2 ventral teeth and 8-9 dorsal teeth, four of which sit on the carapace proper ..........P. vannamei

Rostrum with 4-5 ventral teeth (occasionally 3-8) and 8-9 dorsal teeth (occasionally 5-10), three of which sit on the carapace proper.......... P. stylirostris

Penaeus (Litopenaeus) vannameiBoone, 1931 White shrimp; camarón blanco.

Penaeus vannamei constitutes up to 90% of the catch of the shrimp fishery in continental waters of southern Sinaloa (Soto, 1969) . As for other species of penaeid shrimps which occur in Estero EI Verde, migration is prevented by means of two barriers (known as "tapos") which close the northern and southern channels (see Fig. 1). The shrimps are fished when they reach market size. juveniles and adults have both been collected on several occasions on the northern side of the northern tapo (habitat 12).

Type locality: Panama (Rodriguez de la Cruz, 1976).

Range: From the northern port of the Gulf of California to Tumbes, Peru (Pérez-Farfante, 1970).

Penaeus (Farfantepenaeus) californiensis Holmes, 1900 Brown shrimp; camarón cafe.

Penaeus californiensis is the dominant species of the trawl fishery on the continental shelf of the Gulf of California (Edwards, 1978). Juveniles of this species have been found only once in Estero EI Verde, together with P. vannmei (habitat 12).

Type locality: Bay of San Francisco, California (Holmes, 1900).

Range: San Francisco Bay, California, USA, south to Bahia de Sechura, Piura, Peru, and the Galapagos Islands, Ecuador. Occurs throughout the Gulf of California (Rodriguez de la Cruz, 1976).

Penaeus (Litopenaeus) stylirostris Stimpson, 1871 Blue shrimp; amarón azul

Although Penaeus stylirostris has not been captured during the present study, it is reported from Estero EI Verde by the regional office of the Fishery Department (personal communication). This species is also of major importance for local fishery, and constitutes a considerable part of the fishing stock on the continental shelf of the northern Gulf of California (Edwards, 1978).

Type locality: Bay of Panamá (Rodriguez de la Cruz, 1976).

Range: Punta Abreojos, Baja California Sur, south to the area of Tumbes, Peril, including the entire Gulf of California (Rodriguez de la Cruz, 1976).

Family Callianassidae CallianassaLeach, 1814 Mud-shrimp; ghost shrimp.

The Callianassidae are represented in the Gulf of California by the generaCallianassa and Upogebia. The Callianassidae are burrowing decapods and their presence is intimately related to the presence of soft substrates.

The Thalassinoidea group (which in America also includes the family Axiidae) is presently in confused state of knowledge. In the case of Callianassa, in particular, there is no serious taxonomic work that can be used with enough confidence to permit a reliable identification at specific level.

Brusca (1980) reported 3 (or maybe 4) species ofCallianassa for the Gulf of California. In Estero EI Verde, two species of this genus have been found occupying the sandy mud banks of the inlet delta (habitat 10) .

KEY TO THE HERMIT CRABS OF ESTERO EL VERDE

Chelipeds equal. Eyestalk round in cross section ..........Clibanarius Panamensis

Chelipeds unequal. Eyestalk laterally compressed ..........Coenobita compressus

Coenobita compressus H. Milne Edwards, 1837 Tropical land hermit crab; cangrejo ermitano; chololo.

This species, which is terrestrial, has been collected and observed on several occasions in the estero. As it has been emphasized by Haig et al(1970), these hermit crabs are not very active during day-time. They were commonly found under dead logs and among grasses in the dune (habitat 12) and occasionally on small flats and banks in the delta area (habitat 10) . It is the only species of the genus and of the entire family to be found in the Gulf of California area. They were occasionally observed feeding on decaying fishes.

Type locality: Paita, Perú (Rodriguez de la Cruz, 1976).

Range: Santa Rosalia, Gulf of California, south to the Estrecho de Magallanes. Also reported on Islas Revillagigedo, Isla del Coco and Archipiélago de Galapagos (Haig et al,1970).

Clibanarius panamensis Stimpson, 1859 Hermit crab; cangrejo, ermitaño.

One adult and one young were observed in the estero. They were collected in habitat 11, on the edge of tlie northern channel in about 20 cm of water, and in habitat 12, respectively. Habitat 11 has been found to be typical habitat for C.panamensis in Estero de Urias, Mazatlán, where large numbers occur among submerged roots and dead logs on the side of the estero. Easy to recognize by the longitudinal dark and light stripes on the walking legs, the species is common in the esteros, estuaries and coastal lagoons within its range.

Type locality: Bay of Panama (Stimpson, 1859).

Range: Santa Rosalía, Gulf of California to Isla de la Correa, Peru, and north to Bahía de Santa María on the outer Baja California Peninsula (Ball and Haig, 1974).

With 21 species, the brachyuran crabs constitute by far the most varied group of decapod crustaceans inhabiting the estero system.

KEY TO THE GENERA OF BRACHYURA OF ESTERO EL VERDE

1. Fifth pair of legs flattened and paddelike (Fig. 3-A) ..........Callinectes

Fifth pair of legs not flattened and paddelike..........2

2. Anterolateral border entire, except for outer orbital angle which is sometimes produced into acute tooth.......... 3

Anterolateral border cut into at least two teeth (second tooth small and not very acute inCardiosoma), including outer orbital one ..........7

3. Fronto-orbital width half or less that half width of carapace.......... 4

Fronto-orbital width equal or almost equal to width of carapace ..........5

4. Carapace much wider than long. Eyes reduced. Third ambulatory leg largest. Hand of cheliped compressed. Small crabs..........Pinnixa

Carapace transversaly oval. Eyes not reduced. Ambulatory legs subequal, the second largest. Large land crabs, with hand of cheliped swollen ..........Gecarcinus

5. Lower border of front a curved lobe in frontal view (Fig. 7, A-B).......... 6

Lower border of front almost straight in frontal view.......... Sesarma

6. Eye shorter than half length of eyestalk..........Uca

Eye longer than half length of eyestalk..........Ocypode

7. Only one tooth posterior to outer orbital one ..........8

More than one tooth posterior to outer orbital one ..........10

8. Anterolateral border of carapace rounded. Carapace transversaly oval ..........Cardisoma

Anterolateral border of carapace almost straight. Carapace squarish.......... 9

9. An hairy oblique ridge on exposed surface of the merus of the third maxilliped (Fig 3-B) ..........Sesarma

No hairy oblique ridge on exposed surface of the merus of the third maxilliped ..........Goniopsis

10. Five anterolateral teeth, the second being partly fused with outer orbital tooth ..........11

Anterolateral border cut into less than five teeth.......... Malacoplax

11. Carapace with transverse, broken, raised lines of granules on anterior half ..........Panopeus

Carapace without transverse raised lines of granules on anterior half ..........Eurytium

Goniopsis Pulchra (Lockington, 1876) Mangrove crab (Plate II, A)

Probably the most abundant grapsid of the system, it occupies the banks of the channels where it makes its burrow. Medium-size specimens have been found frequently sharing the same flats (habitat 7) with the three species of Uca typical for this habitat. Burrows are often made among roots of Laguncularia racemosa, or in steep little elevated banks bordered by other vegetation, Goniopsis pulchra is reported by Brusca (1980) as abundant in mangrove swamps of the Gulf of California and as being the only species of the genus to be found on the Pacific side of America. Specimen of G.Pulchraare distinguished from other members of the family occurring in the estero (Sesarma species) by the absence of an oblique hairy ridge on the exposed surface of the third maxilliped (Subfamily Grapsinae). G.pulchra has been recorded from habitats 3, 5, 7, 8, 9 and occassionally 4.

Fig. 3. A: Right fifth leg of Callinectes sp., with flattened last two segments. B: Left part of the third maxilliped of Sesarmarhizophorae, showing the hairy oblique ridge on the exposed surface of the merus (arrow).

Type locality: Bahia Magdalena, Baja California Sur (Rathbun, 1918).

Range: Bahia Magdalena, Baja California Sur and Bahia Kino, Sonora, Mexico, south to Peril. Also reported between Santa Rosalia and Cabo San Lucas, Baja California Sur (Brusca, 1980).

Commonly called marsh crab. The species of the genusSesarma inhabit mangroves of the tropical and subtropical zones, and are often found on banks of estuaries and freshwater coastal streams (Abele, 1972 and 1977).

Until recently, only one species of Sesarma (S. sulcatum Smith) was reported as inhabiting the Gulf of California, its typical habitat being esteros, estuaries and coastal lagoons banks. In Estero EI Verde, however, three species of the genus have been found includingSesarma rhizophoraeRathbun,S. magdalenense Rathbun, andS. sulcatumSmith.

KEY TO THE SPECIES OF SESARMA OCCURRING IN ESTERO EL VERDE (AND IN THE GULF OF CALIFORNIA)

I. Carapace with lateral tooth behind outer orbital tooth ..........2

Carapace without lateral tooth behind outer orbital tooth ..........magdalenense

2.Carapace deeply grooved. Surface of carapace covered with tufts of coarse black hair. Last three segments of walking legs with longitudinal rows of black hair. Width of merus of fourth leg about half its length ..........sulcatum

Carapace slightly grooved. No black hair on carapace or walking legs. Width of merus of fourth leg distinctly less than half its length ..........rhizophorae

Sesarma sulcatum Smith, 1870 Marsh crab; mangrove crab; speckled crab (Plate III, E-F)

An abundant species in the area, it is usually found on the banks of the estero, close to man groves. Specimens were also collected on a narrow soft mud flat shared by Uca vocator ecuadoriensis andUca zacae,and on the sides of the river channel (habitats 3, 7, 8 and 9).S. sulcatum is by far the largest member of the genus in the Gulf of California area.

Type locality: Corinto, west coast of Nicaragua (Rathbun, 1918).

Range: Bahía Magdalena, and Puerto Lobos, Baja California to Panamá (Brusca, 1980).

Fig. 4. Outer view of the chelae of adult specimens of Sesarma rhizophorae. A: Right chelae of male; B: Right chelae of female.

Sesarma rhizophoraeRathbun, 1906 Mangrove crab. (Plate III, C-D; Fig. 4, A-B)

Sesarma rhizophorae is a small size species, reported as abundant in the Pacific mangrove habitats of Panamá (Abele, 1972). In Estero EI Verde, it was captured along steeps banks in burrows also occupied byGoniopsis pulchra. Burrows open well above the water line. Habitat 8.

Type locality: Boca del Jeús Maria, Costa Rica (Rathbun, 1918).

Range: Estero EI Verde, Sinaloa, México, south to Panamá (Hendrickx and van der Heiden, 1984).

Sesarma magdalenense Rathbun, 1918 Mangrove crab. (Plate III, A-B; Fig. 5, A-B)

Like the other species ofSesarmafound in the study area, S. magdalenense occurs close to mangroves, in burrows along the banks of the channels, on mud flat along the sides of the river channel but was also collected under a dead log, about 20 m away from water, with Uca zacae (habitats 7, 8 and 9) .

Type locality: Isla Mangle, Bahia Magdalena, Baja California Sur (Rathbun, 1918).

Range: Including the present record, this species has so far been reported only from three localities: Bahia Magdalena and Cabo San Lucas, Baja California Sur; and Estero EI Verde, Sinaloa, México (Paulet al., 1981).

Gecarcinus quadratus de Saussure, 1895 Land crab; white spot crab. (Plate II, B)

Although there are two species ofGecarcinus reported for the area, G.quadratus and G. planatus Stimpson, 1860, only the former has been found to be a common member of the crustacean community of the estero. It is a land crab whose life history is closely related to the presence of the water of the estero for reproductive reasons only. It is abundant in the system, being found principally in the sand dunes (habitat 2). Gecarcinus quadratus represents the most common land crab of southern Sinaloa.

Type locality: Mazatlán, Sinaloa (Rathbun, 1918).

Range: Upper Gulf of California south to Colombia (Brusca, 1980).

Cardisoma crassumSmith, 1870 Mouthless crab: cangrejo moro; cajo. (Plate II, C)

Cardisoma crassum is by far the largest brachyuran to be found in the estero system. Although its gigantic claws make its Atlantic analog,C. guanhumi Latreille, a favourite dish on the Atlantic coast of America (Taissoun, 1974),C. crassum is left almost depreciated on the Pacific coast of Mexico. Garth (1948) reported the species as being offered for sale in the market at Tumaco, Colombia, along withCallinectes toxotes Ordway and Calappa convexa de Saussure.Cardisoma crassum is common among mangrove roots, where it builds its burrow (habitat 4). It also occasionally occurs on the driest part of the channel banks and flats (habitats 5, 7 and 8), and has been collected once in a burrow on the edge of the muddy sand bank in the inlet area (habitat 10) .

Type locality: Golfo de Fonseca, Honduras (Rathbun, 1918).

Range: Bahia Agua Verde, Baja California Sur and EI Mezcal (Navolato) Sinaloa, south to Rio Tubes, Perú (Rathbun, 1923; Holthuis, 1954; Rodriguez de la Cruz, 1976). Also found in mangrove of Bahia Colorada (Guamuchil), Sinaloa (R. Paul, pers. comm.), and in the area of Guaymas, Sonora (Manrique, 1981).

Pinnixa valerii Rathbun, 1931 Pea crab; cangrejo guisante. (Plate VI, A-B)

The type locality for Pinnixa valevii is Isla San Lucas, Costa Rica, and represents the only locality where this specimens has yet been reported (Schmitt et al., 1973). Two males were collected in the southern channel (habitat 11) using a small bottom dredge. Sampling conditions were soft mud locally covered by grasses. Although there are only a few species of bivalves inhabiting the estero, the host is still unknown.

Type locality: Isla San Lucas, Costa Rica (Rathbun, 1931).

Range: Isla San Lucas, west coast of Costa Rica (Schmitt et al., 1973) and Estero EI Verde, Sinaloa, México, are the only reported localities.

A female specimen of Pinnotheridae, tentatively identified as Scleroplax granulata Rath bun, 1893 was also collected in the inlet area.

Malacoplax californiensis(Lockington, 1876) (Plate 11, E-F)

Only a single specimen of Malacoplax californiensishas been collected. It was captured with a small bottom dredge in the southern channel (habitat 11) . Salinity at the time of capture was of about 22 ppt. This species is reported in earlier literature asSpeocarcinus californiensis(Guinot, 1969).

Type locality: San Diego, California (Rathbun, 1930).

Range: Marina del Rey, Los Angeles, California (Wicksten, pers. comm.) south to Golfo Dulce, Costa Rica (Garth, 1961); in the Gulf of California, north to Bahia de San Luis Gonzaga, Baja California Norte and to Rocky Point, Sonora, (Garth, 1960).

Fig. 5. Outer view of the chelae of adult specimens of Sesarma magdalenense. A:Left chelae of male; B: Left chelae of female.

Ocypode occidentalis Stimpson, 1860 Ghost crab; sand crab; cangrejo de playa. (Plate II, D)

In southern Sinaloa, the ghost crabOcypode occidentalis is omnipresent, although population density is never very high. It typically makes burrows in the sandy beach (habitat 1), and is also occasionally found closer to the inlet area (habitat 10). It feeds on decaying fishes and crustaceans and is a devastating predator of eggs of the ridley turtle Lepidochelys olivacea(Eschscholtz) which oviposits in the area (BrisefloDueñas), 1980).

Type locality: Cabo San Lucas, Baja California Sur (Rathbun, 1918).

Range: Upper Gulf of California and west coast of Baja California, Mexico south to Peru (Brusca 1980).

UcaLeach

As mentioned previously, the hydrography features of the Estero EI Verde make it peculiar in the sense that the system is effectively cut off from the sea most of the year. Indeed, during about two thirds of the year, there is virtually no tidal movement in the entire system and the characteristic rhythm display behavior of the species ofUca occurring in the estero is strongly affected by the absence of the periodic tidal inundations which usually act as an environmental regulator (Crane, 1975).

Apart from the absence of a tidal flooding, the Estero EI Verde corresponds in many aspects to the habitat most characteristic forUcapopulations,i.e., presence of a siltladen stream, ample mangrove fringes and protected beaches of sandy mud and muddy sand (Crane, 1975).

Nontidal populations of fiddler crabs have been studied on several occasions (Powers, 1975), and major differences in display time, loss of tidal rhythmicity and multiplication of the number of burrows per crab have been observed in these conditions. Information available from the study area is not sufficient to permit a more comprehensive comparison with otherUca populations from other nontidal environments.

Preliminary observations, however, clearly demonstrate the existence of an annual migration of populations of fiddler towards the vegetation bordering the system simultaneously with the rapid increase of water level in the channels, immediately after the start of the rainy season.

Six species of Uca have been recorded from Estero EI Verde (Hendrickx, 1979), and although such a variety of fiddler crabs can be considered as relatively high, the population of each are rather reduced in number. Indeed, there are no dense concentrations of Uca to be observed in the area and small populations, physically separated by natural barriers (steep banks, mangrove trees, lateral channels) always occur on narrow stretches of flats or banks.

Fig. 6. Dorsal view of carapace of specimens of the genus Uca. A: U zacae, male (c. w. 13.3 mm); B: U. vocator ecuadoriensis, male (c.w. 18.9 mm).

The main factor limiting the population size could be the lack of periodic humidification of the substrate, hence limting the total surface of flats and banks suitable for colonization. Another factor, although not examined, might be the presence of an abundant bird fauna includ ing whimbrels and heron, two types of birds reported as predators of Uca tangeri (Eydoux) in Gambia (Crane, 1975).

KEY TO THE SPECIES AND SUBSPECIES OF UCA IN ESTERO EL VERDE

1. Front narrow, spatuliform. (Fig. 7, A) ..........princeps princeps

Front wider, not spatuliform. (Fig. 7, B) ..........2

2. Cape of small chelae wide, much wider than adjacent part of the dactyl (Fig. 7, C) ..........3

Gape of small chelae narrow, at the most equal in its middle part to adjacent part of the dactyl (Fig. 7, C) ..........4

3. Major cheliped with fingers not longer than manus Oblique ridge of major cheliped obsolescent to absent. First ambulatory leg without anterior tubercle. Anterior margin of front distinct..........latimanus

Major cheliped with fingers much longer than manus. Oblique ridge of major cheliped well marked. Anterior tubercles on merus and carpus of first ambulatory leg. Anterior margin of front obsolescent.......... musica musica

4. Orbits strongly oblique (Fig. 6, A). No oblique ridge on palm of major cheliped ..........zacae

Orbits straight to slightly oblique (Fig. 6, B). Palm of major cheliped with oblique ridge present and tuberculate ..........5

5. Profuse pile present on carapace. Upper postero-lateral striae of carapace long and strong. Oblique ridge of manus of major cheliped low and blunt; tubercles not in a single row ..........vocator ecuadoriensis

No pile on carapace. Upper postero-lateral striae of carapace not particularly strong (some times absent). Oblique ridge of manus of major cheliped with tubercles close set and si milar in size; tubercles in a single row..........crenulata crenulata

Uca (Uca) princeps princeps(Smith, 1870) Fiddler crab; cangrejo violinista. (Plate IV, A-B)

This is the only member of the subgenusUca to be reported north of EI Salvador. It is represented in the Gulf of California by two distinct subspecies of whichUca princeps moniliferaRathbun is endemic to the northern part (Crane, 1975).

The very narrow front, and large size, makesU. princeps the easiest species ofUca to be recognized. In Estero EI Verde, it occupies in an irregular manner the mud flats (habitats 5 and 6) and the upper part of the banks along the channels (habitat 7 and 8).

Sympatric associates include U. (Minuca) zacaeCrane and U. (Minuca)vocator ecuadoriensis Maccagno, although adults ofU. princeps always occupies the section of the banks or flats the furthest from the water line.

Type locality: Corinto, Nicaragua (Crane, 1975).

Range: Bahia de San Bartolomé, Baja California, south to Peru, including the southern half of the Gulf of California (Crane, 1975).

Uca (Leptuca) latimanus(Rathbun, 1893) Fiddler crab; cangrejo violinista; señoritas. (Plate IV, C-D)

Although Uca latimanus has been reported from a wide variety of habitats (Crane, 1975), in Estero EI Verde this species seems to be res tricted to the muddy sand flats located on either side of the inlet area (habitat 10).

The only sympatric association observed for the area is U.(Leptuca) musica musicaRathbun.

Type locality: La Paz, Baja California Sur (Crane, 1975).

Range: La Paz, Baja California Sur, México, south to Puerto Bolívar, Ecuador, including the Gulf of California (Crane, 1975; Hendrickx, 1979).

Fig. 7. A: Frontal view of Uca princeps princeps; B: Frontal view of Uca crenulata crenulata; C: Minor chelae of male of Uca musica musica; D: Minor chelae of male of Uca zacae.

Uca (Leptuca) musica musica Rathbun, 1914 Sand fiddler crab; cangrejo violinista; señorita. (Plate V, A-B)

Uca musica,a second species of the subgenusLeptuca to be found in the estero, occupies the same habitat as does U. latimanus(habitat 10). U. musica is relatively rare in the area of Mazatlán and it has been so far observed at only one other locality (entrance of Rio Presidio), south of Mazatlán.

Type locality: Bahia de Pichilingue, Baja California Sur (Crane, 1975).

Range: West coast of Baja California north to Bahia de la Magdalena. Present on the Gulf of California mainland from San Blas, Nayarit north to San Felipe, Baja California Norte (Crane, 1975).

Uca. (Leptuca) crenulata crenulata (Lockington, 1877) Fiddler crab; cangrejo violinista; señorita (Plate IV, E-F)

U. crenulata, the third species of the subgenusLeptuca to be found in the estero, is not abundant at all and few specimens have been collected (habitat 6). This species, however, has been found to be the dominant fiddler crab on the flats of Estero de Urias, in the Mazatlán Harbour, only 30 kilometers south of Estero EI Verde.

Type locality: Bahia de Todos Santos, Baja California (Crane, 1975).

Range: From San Felipe, Baja California Norte and Guaymas, Sonora, south to La Paz, Baja California Sur and Bahia de Tenacatita, Jalisco; also reported from Bahia de Todos Santos, BajaCalifornia Norte, north to Newport Beach, California (Crane, 1975).

Uca (Minuca) zacaeCrane, 1941 Fiddler crab; cangrejo violinista; señoritas. (Plate V, ET)

One of the most abundant species of fiddler crab in the estero, Uca zacae occurs on muddy banks and small flats all along the channels (habitats 5, 7 and 8) together withU. (minuca) vocator ecuadoriensisMaccagno which is almost invariably found associated with it. It has also been occasionally collected on the edge of the largest flats of the system, close to water line (habitat 6) .

Sympatric associates include U. vocator ecuadortensis and occasionally U. Princeps.

Type locality: Golfito, Costa Rica (Crane, 1975).

Range: Estero EI Verde, Sinaloa, México south to Golfito, Costa Rica (Crane, 1975; Hendrickx, 1979).

Uca (Minuca) vocator ecuadoriensisMaccagno, 1928 Fiddler crab; cangrejo violinista. (Plate V, C-D)

The second species of the subgenusMinucacollected in the system,U. vocator is the dominant fiddler and is represented by the subspeciesU. vocator ecuadoriensis. It occurs in the same habitats as does U. zacae (habitat 5, 7 and 8), its common sympatric associate.

Type locality: Esmeraldas, Ecuador (Crane, 1975).

Range: Bahia de Kino, Sonora, México, south to Puerto Pizarro, Peru (Crane, 1975; Hendrickx, 1979).

CallinectesStimpson, 1860

Of the three species ofCallinectesreported from the Gulf of California, only two have been found to occurre in Estero EI Verde, although these three species include the study area in their range of distribution (Hendrickx, 1984).

Members of the genusCallinectesare probably the only swimming crabs which are used as sea food in the Gulf of California area. This utilization, however, is restricted to the local markets and a major effort is presently being exerted with a view to develop a large-scale fishery of the genus on the Pacific coast of México (Paul, 1979).

KEY TO THE SPECIES OF CALLINECTES OF ESTERO EL VERDE

Outer pair of frontal teeth lobulate. Sixth abdominal segment of male with lateral side narrowest in its proximal third; proximal end almost straight ..........toxotes

Outer pair of frontal teeth triangular. Lateral side of sixth abdominal segment of male diverging and widest proximally; lateral portion of proximal end with rounded tips ..........arcuatus

Callinectes arcuatus Ordway, 1863 Swimming crab; jaiba. (Plate VI, F)

This is by far the most abundant species to be found in the esteros and coastal lagoons of southern Sinaloa. Being a migrating species which spawns in open sea,Callinectes arcautus is also commonly caught during trawling operations made on the continental shelf.

Like other members of the Family Portunidae, it is a fully aquatic species and it has been collected and observed frequently in habitat 11 and 12.

Type locality: Cabo San Lucas, Baja California Sur (Rathbun, 1930).

Range: Los Angeles Harbour, California south to Mollenda, Perú and the Galapagos Islands (Williams, 1974). Also commonly found throughout the Gulf of California (Brusca, 1980).

Callinectes toxotesOrdway, 1863 Swimming crab; jaiba

The second species of the genusCallinectes occurring in Estero EI Verde, C. toxotes is apparently not very abundant and was not collected during the present study. However, it has been reported by N. Salazar (pers. comm.) as occurring in the system and has since been collected successively in other esteros and lagoons of southern Sinaloa (Paul, 1982).

Type locality: Cabo San Lucas, Baja California Sur (Rathbun, 1930).

Range: From northern Peru (Williams, 1974) north to Rio PiaxtIa (Rio Verde), Sinaloa, México, on the mainland side of the Gulf of California (Paul, 1982).

PanopeusMilne Edwards, 1834

Three species ofPanopeushave been reported for the southern part of Sinaloa (van der Hei den and Hendrickx, 1982), two of which have been collected in Estero EI Verde. Commonly called mud-crabs, these xanthid crabs are also commonly found on oyster beds, rocks and coral reefs.

KEY TO THE SPECIES OF PANOPEUS FROM ESTERO EL VERDE

Color of fixed finger of cheliped continued on palm. Chelae of major chepiled of male about twice as high as minor cheliped (Plate VI, D) ..........bermudendis

Color of fixed finger of cheliped not continued on palm. Chelae of major cheliped of male mucho less than twice height of minor cheliped ..........purpureus

Panopeus bermudensisBenedict and Rathbun, 1891 Mud crab; oyster crab. (Plate VI, C-D)

A large population ofPanopeus bermudensis is found on medium size stones colonized by oysters (Crassostrea iridescens(Hanley)) on the southern side of the northern tapo. Presence of these stones is probably due to artificial introduction by fishermen during the construction of the tapo. P. bermudensis has also been occasionally collected on submerged roots of Rhizophora mangle L., colonized by the same species of oyster. So as not to lenghten unnecesarily the list of habitats considered in the present paper, P. bermudensis will be refered to simply as an occupant of habitat 11.

Type locality: Bermuda (Rathbun, 1930).

Range: Cabo San Lucas, Baja California Sur and Estero EI Verde (present paper), Sinaloa, Mexico south to Matapalo, Peru (Rathbun, 1930).

Panopeus purpureus Lockington, 1876 Mud crab. (Plate VI, E)

Only two male specimens of P. Purpureushave been collected in Estero EI Verde. Both were found on a submerged rock at the northern edge of the inlet area (habitat 12).

Type locality: Bahia Magdalena, Baja California Sur (Rathbun, 1930).

Range: Bahia Magdalena, Baja California Sur and Guaymas, Sonora, México, south to Perú (Rathbun, 1930).

Eurytium albidigitumRathbun, 1933 Mud crab.

A single male has been found on a mud bank bordered by the white mangroveLaguncularia racemosa. (L.) (habitat 7).

Type locality: San Felipe, Baja California Norte (Rathbun, 1933).

Range: Known from the upper Gulf of California down to San Felipe, Baja California Norte, on the western coast of the Gulf and to Estero EI Verde, Sinaloa, on the mainland coast (Hendrickx and van der Heiden, 1984).

Coastal lagoons in the southeastern Gulf of California represent the most typical ecosystem in this area. To a greater or lesser extent, they are all associated with the presence of mangrove which provide them with habitats rich in vascular plants detritus and protection from the sun, factors which favourize the presence and development of large populations of terrestrial and semi-terres trial detrivorous decapod crustaceans (Crane, 1947; Mann, 1972). The aquatic fauna, in turn, will find both protection and large amount of food in the calm waters of the numerous channels dissecting the lagoon complexes.

In many cases, however, the crab populations are restricted to the seaward portions of these lagoon system, in areas where channels are the most numerous, water level remains adequate all year round and dense stands ofRhizophora mangle and Laguncularia racemosaare found. In addition to these three factors, which are commonly related, one could add the existence of tidal movements which are greatest in the inlet area and the seaward portions of the lagoons. Although the Estero EI Verde is no exception to this, the impact that these features have on the distribution of the decapod crustacean fauna is not so striking. Indeed, because of its small size, which results basically from the absence of large tidal flats, and the presence of two deep permanent channels, most potential habitats are rapidly recolonized when environmental conditions are adequate (i. e., when the system behaves like a tidal estuary) by individuals originating from the permanents populations of crabs inhabiting the system (e.g., Uca, Sesarma and Goniopsis).

As it has been pointed out previously, the absence of a tidal flooding during most of the year probably affects drastically the populations of fiddler crabs and their success towards the occupation of the area. Observations made in October and November 1980 confirmed this hypothesis. In October 1980, unusually heavy rainfall which lasted three days, washed open the sand bar that had almost completely closed the inlet. The result of this was a prolongation of the period of open mouth and hence of tidal influence in the system. As a direct consequence, flats which are normally submerged at this time of the year were still subjetc to rhythmical tidal flooding and were therefore suitable for colonization by fiddler crabs. Indeed, dense populations of young Uca princeps princeps and U. vocator ecuadoriensiswere observed on long narrow flats at the entrance of the southern channel in November.

Among all species of decapod crustaceans collected in the system, only Sesarma magdalenense. seems to have a restricted geographic distribution. However, it is almost certain that future collections along the Pacific coast of México will reveal a much more ample distribution of this species.

Several species of brachyuran crabs collected in the Estero EI Verde had been recently found to occur at much higher latitudes that previously thought (Hendrickx, 1979; Hendrickx and van der Heiden, 1984). Indeed, S. rhizophorae, Uca zacae and Pinnixa valerii are now all known from the Gulf of California area, near the Tropic of Cancer. Range extensions reported for these species were of 2,300 kilometers or more, northwards. This fact, particularly in case of such easily detectable animals, is of significance and demonstrate the poor state of knowledge of estuarine and lagoon brachyuran fauna in the area comprised roughly between the northern Gulf of California and Panamá.

ACKNOWLEDGEMENTS

The author wish to thank R. K. G. Paul, A. van der Heiden, M. K. Wicksten and R. C. Brusca for their critical review of the manus cript. M. K. Wicksten is also to be thanked for the help provided with the identification of several specimens.

Plate 1. Aerial photographs of the Estero EI Verde, Sinaloa. A: Part of the northwestern channel (foreground), inlet área (arrow) and beginning of the southeastern channel; B: View of the inlet área looking northward, the mouth of the lagoon being closed (arrow); C: View of the mangrove stands at the end of the northwestern channel. D: View of the rio Quelite at its junction with the inlet área (foreground).

Plate II. Dorsal and frontal views of species of Brachyura. A: Goniopsis pulchra, male, dorsal view (c.l. 34.9 mm); B: Gecarcinus quadratus, male, dorsal view (c.l. 49.3 mm); C: Cardisoma crassum, female, dorsal view (c.l. 55.6 mm); D: Ocypode occidentalis, male, dorsal view (c.l. 29.2 mm); E-F: Malacoplax californiensis, male, dorsal and frontal views (c.l. 9.2 mm).

Plate III. Dorsal view of specimens of the genus Sesarma. A: S. magdalenense, male (c.l. 11.1 mm); B: S. magdalenense, male (c.l. 10.0 mm); C: S. rhizophorae, male (c.l. 11.7 mm); D: S. rhizophorae, female (c.l. 14.9 ram); E: S. sulcatum, female (c.l. 16.9 mm); F: S. sulcatum, male (c.l. 16.7 mm).

Plate IV. Outer and inner views of the major claw of males of the genus Uca. Number in brackets refers to total length of the claw (manus + pollex). A-B:U.rinceps princeps (81.01 mm); C-D; U. latimanus (12.8 mm); E-F: U. crenulata crenulata (29.7 mm).

Plata V. Outer and inner views of the major claw of males of the genus Uca. Number in brackets refers to total length of the claw (manus + pollex); A-B: U. musica musica (18.1 mm); C-D; U. vocator ecuadoriensis (31.6 mm); E-F; U. zacae (20.2 mm).

Plate VI. Dorsal and ventral views of species of Brachyura. A-B: Pinnixa valerii, male (c.l. 6.3 mm); C-D: Panopeus bermudensis, male (c.l. 9.6 mm); E: Panopeus purpureus, male (c.l. 23.3 mm); Callinectes arcuatus, female (c.l. 41.9 mm).

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