Hydrocoryne iemanja (Cnidaria) - Instituto de Biociências - USP

Journal of the Marine Biological Association of the United Kingdom, 2009, 89(1), 67–76. 

doi:10.1017/S0025315408002968 Printed in the United Kingdom 

#2009 Marine Biological Association of the United Kingdom 

Hydrocoryne iemanja (Cnidaria), 

a new species of Hydrozoa with unusual 

mode of asexual reproduction 

andre c. morandini 1 ,sergio n. stampar 2 , alvaro e. migotto 3 and antonio c. marques 2 

1 Grupo de Sistemática e Biologia Evolutiva (GSE), Núcleo em Ecologia e Desenvolvimento Sócio-Ambiental de Macaé (NUPEM/ 

UFRJ), Universidade Federal do Rio de Janeiro, C.P. 119331, Macaé, RJ, 27910-970, Brazil, 2 Departamento de Zoologia, Instituto de 

Biociências (IB-USP), Universidade de São Paulo, R. Matão, trav. 14, 101, São Paulo, SP, 05508-900, Brazil, 3 Centro de Biologia 

Marinha (CEBIMar-USP), Universidade de São Paulo, Avenida Manoel H. do Rego km 131,5, São Sebastião, SP, 11600-000, Brazil 

Hydrocoryne iemanja sp. nov. was found in an aquarium, growing on rhodoliths of coralline algae collected on the southeastern 

coast of Brazil (20840 0 S4082 0 W). The colonies were reared through maturity in the laboratory. Each colony had up to 

7 sessile, long and thin monomorphic zooids, very extensible and flexible, arising from a chitinous, hard dark-brown plate 

with minute spines. Medusae budded from near the basal part of hydrocaulus, and were released in immature condition, 

acquiring fully developed interradial gonads 5–7 days after release. Asexual reproduction by longitudinal fission was observed 

on the hydrocaulus of the polyps, both for those in normal condition and those with injuries. Fission started at the oral region, 

extending aborally, with a new hard plate formed in the basal part of hydrocaulus. When fission reached the new hard plate, 

the new polyp detached, becoming free and sinking to the bottom, starting a new colony. Detached polyps were morphologically 

indistinguishable from other polyps, being able to produce medusae. Mother and daughter polyps undertook subsequent 

fissions. This mode of longitudinal fission is distinct from other modes of longitudinal fission, a process known for a few species 

of cnidarians. Further studies of this process may shed light on the understanding of the evolutionary pathways in Cnidaria 

and animals. Hydrocoryne iemanja sp. nov. is distinguishable from its two congeners by the distinct marginal tentacles of the 

medusae—short and with a median nematocyst knob—an unambiguous character useful even for the identification of newly 

liberated medusae. 

Keywords: Anthoathecata, Hydrocorynidae, medusa, polyp, life cycle, cnidome, fission, Brazil 

Submitted 18 January 2008; accepted 4 March 2008 

INTRODUCTION 

Hydrozoans are common and widespread invertebrates on 

shallow water. Yet, as they are mostly represented by species 

with small body dimensions and cryptic life habits, their 

study is neglected and the knowledge on their biodiversity is 

far from satisfactory. In general, accumulated knowledge is 

geographically concentrated, with some areas almost 

unknown. This is particularly true for the Brazilian coast, in 

which just a few localities of its south-eastern region are relatively 

well-known (Migotto et al., 2002; Marques et al., 2003; 

Migotto & Marques, 2006). New species of hydroids continue 

to be described every year worldwide, even in relatively wellknown 

regions, with the discovery of inconspicuous specimens 

and re-evaluation of morphological variation. 

Among hydrozoans, the poorly-known family Hydrocorynidae 

Rees, 1957 (Cnidaria: Hydrozoa: ‘Anthoathecata’) comprises two 

valid genera (Kubota, 1988; Mangin, 1991): Hydrocoryne 

Stechow, 1907, and Samuraia Mangin, 1991. The three species 

of the group so far described are restricted to Pacific waters 

(Kubota, 1988; Mangin, 1991), with only one unidentified 

Corresponding author: 

A.C. Morandini 

Email: andre.morandini@gmail.com 

record (Hydrocoryne sp.) for the Atlantic Ocean (Wedler & 

Larson, 1986). 

A hydroid belonging to the family Hydrocorynidae was 

never reported in the southern hemisphere, including the 

Atlantic Ocean. Species such as Hydrocoryne, which are inconspicuous 

and difficult to collect individually by hand, are usually 

found after examining substrata—larger organisms such as algae 

and invertebrates with hard skeletons, and pebbles and biogenic 

nodules—in the laboratory. Nevertheless, delicate specimens 

usually get damaged during or after collecting procedures (e.g. 

manual, trawling, dredging or grabbing techniques) and their 

soft parts may shrink, degrade or be resorbed, making their 

remains indistinguishable or simply hard or impossible to see, 

even under a microscope. However, when pieces of substrata 

such as pebbles, broken shells and calcareous nodules are kept 

in the laboratory under favourable conditions, the shrunk 

polyps or the regressed or dormant tissues may become active 

or give rise to new polyps. Many species of hydroids were 

described employing intentionally this technique or just by 

chance, as was the species described here. 

Distinction between species of the genus Hydrocoryne is 

based on the medusa stage, thus development and life cycle 

observations are essential for identification. In rearing the 

species, we gathered data of not only its sexual phase but 

also of an unusual mode of asexual reproduction within 

Hydrozoa—longitudinal fission. 

67

68 andre c.morandiniet al. 

Asexual reproduction is a poorly known reproductive trait in 

several cnidarian groups. Although hydrozoans present a wide 

variety of asexual processes, fission seems restricted to a few 

species, and may be considered a rare phenomenon within the 

Hydrozoa (Shostak, 1993). Longitudinal fission, in particular, 

is reported for a few hydromedusae (e.g. Stretch & King, 1980) 

and hydropolyps (Shostak, 1993; Bouillon et al., 2004). 

The uniqueness of the process of longitudinal fission 

among the hydrozoans highlights the importance of the new 

finding, which may shed light on the understanding of the 

evolutionary pathways in Cnidaria and animals. Therefore, 

the goal of this study is to describe a new species of 

Hydrocorynidae, from the tropical waters of the south-eastern 

Brazilian coast, and its unusual mode of asexual reproduction. 

MATERIALS AND METHODS 

The hydroids were found growing on rhodoliths of coralline 

algae (called ‘living stones or rocks’ by Brazilian aquarists) 

in an aquarium in August 2005. Rhodoliths were collected 

from the Guarapari county region (20840 0 S 040829 0 W), state 

of Espírito Santo, Brazil (Figure 1). Certainty concerning the 

original location of the species was possible because the 

aquarium contained only artificial seawater and recently collected 

rhodoliths from the same place. Two colonies were isolated 

from the substratum and transferred to a small glass 

aquarium (500 ml) with constant air bubbling. 

The hydroids were reared in the laboratory at the 

Departamento de Zoologia of the Universidade de São Paulo. 

The colonies were kept in natural seawater from the São 

Sebastião Channel. The aquarium was kept under a natural daylight 

regime at room temperature (20–258C). The seawater of 

the cultures was changed every week and the polyps were fed 

every other day with Artemia nauplii (method adapted from 

Jarms et al., 2002). 

After the medusae were released from the polyp, they were 

kept in glass Erlenmeyer flasks of different sizes (250 and 

500 ml) with gentle air bubbling to provide water current (see 

a fuller description of the method in Stampar et al., 2006). 

Seawater was changed three times per week, and Artemia 

nauplii and gonad macerate of the clam Perna perna 

(Linnaeus, 1767) were offered daily as food. The medusae were 

also kept under natural light and room temperature at 20–258C. 

Morphological, morphometric, and cnidome studies were 

recorded from fresh and preserved material. Measurements 

were carried out under a dissection microscope. Preserved and 

fresh materials were used in squash preparations, with distilled 

water and saliva, for cnidome observations under interferencecontrast 

light microscopy (cf. Migotto, 1996). The terminology 

for the cnidome is that of Weill (1930, 1934) and Mariscal (1974). 

Type material was deposited in the cnidarian collection of 

the Museu de Zoologia da Universidade de São Paulo 

(MZUSP). 

RESULTS 

SYSTEMATICS 

Class HYDROZOA Huxley, 1856 

Subclass ANTHOATHECATA Cornelius, 1992 

Order CAPITATA Kühn, 1913 

Family HYDROCORYNIDAE Rees, 1957 

Hydrocorynidae Rees, 1957: 525; Petersen, 1990: 134–135; 

Bouillon & Boero, 2000: 124. 

AMENDED DESCRIPTION 

Colonies unbranched, hydranths monomorphic spindleshaped 

not well demarcated from hydrocaulus, oral tentacles 

capitate, long, hollow, in 5–6 close sets of whorls around 

conical hypostome, hydrocaulus long, highly extensible, 

naked, with thickened mesolamella issuing from hard hydrorhizal 

stolonal plate; medusa buds in clusters on basal part of 

hydrocaulus. Medusae bell-shaped; with or without gastric 

peduncle; four marginal tentacles with scattered cnidae and 

median knob; clasping tentacular bulbs with ocelli; manubrium 

broadly flask-shaped or tubular, quadrate or cruciform 

in cross-section; mouth cruciform, with or without cnidocyst 

clusters; gonads interradial without longitudinal groove, 

almost totally surrounding manubrium. 

REMARKS 

Fig. 1. Map of Brazil, showing the type locality (Guarapari) of Hydrocoryne 

iemanja sp. nov. 

In a review of the capitate hydroids, Petersen (1990) established 

the suborder Sphaerocorynida including two superfamilies, 

Sphaerocorynoidea (with three families: Paragotoeidae Ralph, 

1959, Sphaerocorynidae Prévot, 1959 and Zancleopsidae, 

Bouillon, 1978) and Hydrocorynoidea (encompassing exclusively 

the family Hydrocorynidae). The genus Paragotoea 

Kramp, 1942 is considered presently among the 

Corymorphidae Allman, 1872 (cf. Bouillon et al., 2004). 

The family Hydrocorynidae was proposed by Rees (1957) to 

accommodate the Japanese hydroid Hydrocoryne miurensis 

Stechow, 1907. Polyps of this species are notable for their 

length when fully expanded, reaching up to 6 cm long or more 

(Rees et al., 1976). Nevertheless, the polyps have quite simple 

morphologies, and the systematics of the genus is based on 

differences of the medusae stage (cf. Kramp, 1961). The family

hydrocoryne iemanja sp. nov., a new hydroid with longitudinal fission 69 

comprises only two genera (Hydrocoryne Stechow, 1907 and 

Samuraia Mangin, 1991) and three species have been described 

so far (Hydrocoryne bodegensis Rees, Hand & Mills, 1976; 

Hydrocoryne miurensis and Samuraia tabularasa Mangin, 

1991) (see Rees et al., 1976; Mangin, 1991). In addition, 

Hydrocoryne sp., possibly representing a new species, is referred 

to Puerto Rico by Wedler & Larson (1986: 79) and Panama by 

Calder & Kirkendale (2005: 481). The genera are differentiated 

by the production and release of medusae (as in Hydrocoryne) 

or eumedusoids that are either retained or not on the polyps (as 

in Samuraia) (Kubota, 1988; Mangin, 1991). 

Genus Hydrocoryne Stechow, 1907 

Hydrocoryne iemanja sp. nov. 

(Figures 2–7) 

TYPE MATERIAL 

Holotype: female medusa from polyp culture, 0.9 mm high, 

0.7 mm wide, preserved in 4% formaldehyde solution in seawater 

(Guarapari, state of Espírito Santo, Brazil, 20840 0 S 

040829 0 W), reared in the laboratory for 7 days, 12 September 

2005 [MZUSP 1972]. 

Paratypes: one 7-day-old male medusa, preserved in 4% 

formaldehyde solution in seawater (same locality as holotype), 

12 September 2005 [MZUSP 1973]; five recently released 

medusae, preserved in 70% ethanol (same locality as holotype), 

5 September 2005 [MZUSP 1974]; two polyps reared 

in the laboratory, preserved in 4% formaldehyde solution in 

seawater, 5 January 2005 [MZUSP 1975]. 

ETYMOLOGY 

The specific name iemanja is derived from the name of the 

queen of the waters and seas (Iemanjá in Portuguese) of the 

African–Brazilian religions, derived from the Yoruba 

language expression Yèyé ȯmȯ ėjá (‘mother which sons are 

little fishes’). Iemanjá is the daughter of the God or Goddess 

of the Sea (Olóòkun), and also the name attributed by the 

Yoruba ethnic nation in Nigeria of a river (Yemȯja) (Verger, 

1981; Walker, 1990). 

DIAGNOSIS 

Hydrocoryne species with hydrorhiza embedded in chitinous 

dark-brown hard-plate with minute spines; asexual reproduction 

by longitudinal fission, and hydrorhizal plate 

arising from column. Tentacle of medusa filiform, except 

for a large, adaxial nematocyst cluster on its middle 

(Figure 2). 

DESCRIPTION 

Colonies with up to 7 sessile polyps (usually 2–3) (Figure 3A), 

arising from hydrorhiza embedded in chitinous hard darkbrown 

plate up to 2.5 cm in diameter, with minute spines 

(Figure 3A). Living polyps 7.0–8.5 cm high, 1–2 mm wide, 

whitish (or slightly orange tinted because of Artemia diet), 

Fig. 2. Hydrocoryne iemanja sp. nov. (A) Basal half of a medusa with tentacles; 

(B) detail of the tentacle knob and contracted tentacle, note that in the tentacle 

there are nematocysts only in the knob. 

monomorphic, variable in shape, generally elongate, spindleshaped; 

hypostome prominent, nipple-shaped when relaxed, 

proboscis-like when extended, up to 2 mm high. Capitate tentacles 

(Figure 3B–D) up to 20 in number, 0.2–0.4 mm long, in 

4–5 closely arranged whorls at suboral region; capitulum 

0.08–0.12 mm in diameter. Stalked medusa buds on lateral 

branches, closely and alternately arranged at basal third of hydrocaulus; 

up to 9 lateral branches per hydranth and up to 7 medusa 

buds on each branch (Figure 3F). Asexual reproduction by longitudinal 

fission and production of a chitinous hard plate at basal 

1/3 of parental hydrocaulus; fission process starts from oral end 

towards new hard plate; polyp becomes free and starts a new 

colony (Figures 3C–E & 5A–D). Nematocysts (Figure 7A–J): 

tentacles—heterotrichous microbasic euryteles with inclusion 

13.7–14.7 4.9–5.8 mm (N¼ 10, mean ¼ 14.4 5.19 mm, 

SD + 0.47 0.47 mm), and stenoteles 14.7–16.6 9.8– 

10.7 mm (N¼ 10, mean ¼ 15.4 9.9 mm, SD + 0.9 

0.41 mm); column—heterotrichous microbasic euryteles 10.7– 

12.7 4.9–6.8 mm (N¼ 10, mean ¼ 11.5 5.9 mm, 

SD + 0.77 0.55 mm), smaller stenoteles 11.7–14.7 

5.8–8.8 mm (N¼ 10, mean ¼ 12.9 7.4 mm, SD + 1.2 

1.0 mm), and larger stenoteles 17.6–19.6 11.7–13.7 mm 

(N ¼ 5, mean ¼ 18.6 13.1 mm, SD + 0.98 0.87 mm). 

Newly-released medusa is released in immature condition, 

transparent, slightly flattened on top, higher than wide 

(0.57 mm high; 0.51 mm in diameter) (Figure 4A–B). 

Mesoglea thin, without apical process and apical canal. 

Exumbrella with scattered nematocyst clusters; 3–4 nematocysts 

per cluster. Radial canals four, simple and straight; circular canal 

narrow. Velum narrow; velar opening 1/3 of total diameter at 

margin (0.32 mm). Four perradial marginal bulbs, each with a 

short tentacle (0.16 mm long, 0.032 mm wide) and a large 

abaxial red ocellus (Figure 4A–B & F). Tentacles hollow, filiform, 

except for a large, adaxial nematocyst cluster on its middle. 

Manubrium quadratic, 0.24 mm high, with simple mouth; 

peduncle lacking. Gonad rudiments not visible on release. 

Nematocysts (Figure 7K–T): tentacles—smaller stenoteles 

6.8–9.8 4.9–5.8 mm (N¼ 10, mean ¼ 8.2 4.9 mm, 

SD + 0.82 0.3 mm) with shaft length 9.8 mm, spines 

length 4.9 mm, and larger stenoteles 12.7–15.6 8.8–10.7 mm 

(N ¼ 10, mean ¼ 14.5 9.9 mm, SD + 0.77 0.61 mm)


Fig. 3. Hydrocoryne iemanja, sp. nov. (A) Polyp colony base with hard plate and five zooids partly laid on the bottom; (B) detail of a zooid with gonophores at the 

basal region of hydrocaulus; (C–D) zooid undergoing longitudinal fission; (E) hard plate formation at middle of hydrocaulus; (F) reproductive branch arising from 

the hydrocaulus, with stalked medusae in different stages of development. 

with shaft length 11.7 mm, spines length 5.8 mm; tentacular 

bulbs—microbasic mastigophores 9.8–10.7 8.8–9.8 mm 

(N ¼ 10, mean ¼ 10.3 9.2 mm, SD + 0.5 0.5 mm) and 

desmonemes 6.8–7.8 3.9–5.8 (N ¼ 10, mean ¼ 7.4 

4.9 mm, SD + 0.5 0.46 mm); exumbrella–holotrichous 

isorhizae in scattered pads with 2–6 nematocysts 7.8–9.8 

4.9 mm (N¼ 10, mean ¼ 8.4 4.9 mm, SD + 0.68 0 mm). 

Mature medusa bell-shaped (Figure 4C–D); bell 1.2–1.4 mm 

high, 0.9–1.1 mm in diameter at median part; umbrellar margin 

diameter up to 1.2 mm. Velum large; velar opening 1/5 of total 

aboral diameter. Four radial canals, ring canal present. Four perradial 

tentacular bulbs with one marginal tentacle and one red 

adaxial ocellus each (Figure 4C–D). Tentacles short, contractile, 

with a large, adaxial nematocyst knob at middle of tentacle. 

Manubrium tubular, about 1/2–4/5 of subumbrellar height, 

without concentrations of nematocysts on lips. Males with 

shorter manubrium than females (Figure 4C–D). Gonads interradial, 

covering nearly whole manubrium, light orange to deep 

orange in male specimens and deep orange to red in female 

living specimens (Figure 4C–D & E). Eggs (0.05–0.06 mm) 

visible by transparence through thin manubrial epithelium 

(Figure 4D–E). Nematocysts (Figure 7K–R): tentacular 

bulbs—microbasic mastigophores 12.7–15.6 9.8–11.7 mm 

(N ¼ 10, mean ¼ 13.5 10.9 mm, SD + 1 0.77 mm); tentacles—smaller 

stenoteles 8.8–10.7 5.8–6.8 mm (N¼ 10, 

mean ¼ 9.9 6 mm, SD + 0.61 0.41 mm) and larger stenoteles 

13.7–15.6 9.8–12.7 mm (N¼ 10, mean ¼ 15 11 mm, 

SD + 0.68 0.8 mm). Exumbrella without nematocysts. 

LIFE CYCLE AND BIOLOGICAL DATA 

The long and thin polyps of Hydrocoryne iemanja sp. nov. 

are very extensible and flexible. They preferably stay 

upwards, moving back and forth, when subjected to strong 

water circulation in the aquarium; not being able to maintain 

an erect position, they lay on the bottom in quiet 

water. Polyps that stayed longer periods laid on the


food passed to the common cavity from either end, as could 

be clearly seen by transparence. Meanwhile, a new hard plate 

of epidermal origin and involving soft tissues gradually appeared 

in the middle of hydrocaulus, being globular (0.25–0.3 mm) and 

flexible when well developed (Figures 3E & 5C). When the 

fission process reached the new hard plate—which keeps its 

globular shape or becomes dish-like in recumbent polyps—the 

hydrocaulus separated from each other and the new hard plate 

gradually detached from the other hydrocaulus. Subsequently, 

one of the polyps detached from the other, becoming free and 

sinking to the bottom, where its hard plate attached, forming a 

new colony (Figure 5D). The whole fission process took about 

48 hours. After detachment, the original polyp remained alive 

and functional, without scars on its hydrocaulus. Soon after 

release, the new polyp was about half the length of the remaining 

one, being morphologically indistinguishable from other polyps; 

it was able to bud off medusae and soon attained the size of fully 

developed polyps. Mother and daughter polyps might undertake 

subsequent fissions. 

The species is metagenetic (Figure 6). Polyps released 

medusae during the period of cultivation (from August 2005 

to September 2007); the medusae were easily reared through 

maturity. Since the first visual indication of the formation of 

the gonophores, it took about 24 hours for the medusae to 

start to be released; polyps released medusae for about a week. 

Medusae production was triggered by intense feeding of 

polyps. Newly-liberated and mature medusae exhibited positive 

phototaxis, swimming more intensely during light hours. 

Medusae became mature, with fully developed gonads 

(Figure 4C–D), 5–7 days after release. Eight to fourteen days 

after release, the medusae shed their gametes on the water 

column (at night), where fertilization occurred. Some planulae 

attached to the bottom of the culture dishes, but further development 

was not obtained. Medusae degenerated after spawning. 

Fig. 4. Hydrocoryne iemanja, sp. nov. (A) Newly released medusa; (B) newly 

released medusa just after feeding with Artemia; (C) mature male medusa 

(7 days old); (D) mature female medusa (7 days old), showing eggs on the 

sides of the manubrium; (E) detail of the manubrium of a female medusa, 

showing eggs; (F) detail of the umbrellar margin of a newly released 

medusa, showing a tentacle bulb with nematocysts and an ocellus. 

bottom had fewer and less developed tentacles. Polyps that 

were overgrown by filamentous algae reduced the number 

and length of their tentacles, and their basal chitinous hardplate 

started to produce new hydranths, functioning as a 

stolon-like structure. 

Asexual reproduction by longitudinal fission was commonly 

observed (Figures 3E & 5). Although this process 

occurred in normal condition polyps, it was also initiated 

when the polyp remained lying on the bottom for extended 

periods or presented some kind of injury in their column. 

Fission started at the oral region (Figures 3C & 5A), extending 

aborally (Figures 3D & 5B, C). The hypostome expanded laterally 

and the division proceeded along the oral–aboral axis of 

the polyp, resulting in a polyp with two oral ends well-defined, 

each with a hypostome and a half crown of tentacles, which 

gradually formed new tentacles, completely encircling the 

hypostome. At this point, the dividing polyp looked like a Y, 

both oral ends being able to catch food independently; their individual 

gastrodermal cavity merged at the point of fission, and 

DISCUSSION 

Species of the genus Hydrocoryne were recorded only in four 

locations hitherto: Japan, California (USA) and Russia (Peter 

the Great Bay, Japan Sea) (Margulis & Karlsen, 1980; 

Hirohito, 1988; Kubota, 1988), all in the North Pacific 

Ocean, and in the Caribbean (Wedler & Larson, 1986; Calder 

& Kirkendale, 2005). Kubota (1988) suggested that the validity 

of the species H. bodegensis and H. miurensis is doubtful, 

because both are sympatric or partially sympatric (see also 

Stepanjants, 1994). The Caribbean Hydrocoryne sp. is only 

known from its polyp stage and newly-released medusae 

(Wedler & Larson, 1986). Although Wedler & Larson’s 

(1986) brief description does not mention tentacle features of 

the newly-released medusa, we believe that the tentacles of 

the Caribbean Hydrocoryne sp. is distinct from Hydrocoryne 

iemanja sp. nov. based on the unique nematocyst knob, 

which could hardly pass unnoticed. We therefore conclude 

that Hydrocoryne sp. from the Caribbean is not conspecific 

with H. iemanja sp. nov., being possibly a distinct and 

undescribed species, as supposed by Calder & Kirkendale 

(2005). 

Hydrocoryne iemanja sp. nov. represents the first record of 

the family Hydrocorynidae for the South Atlantic. Its known distributional 

range is restricted to the type locality on the southeastern 

coast of Brazil. The knowledge on the hydrozoan 

fauna of the Brazilian coast is heterogeneous, the south-eastern


Fig. 5. Asexual reproduction of polyp of Hydrocoryne iemanja, sp. nov. Diagram showing the sequence of a zooid undergoing longitudinal fission from its oral tip 

(A), branching (B), forming a hard plate at the basal part of hydrocaulus (C), and the new, asexually produced zooid (D). 

region being the best-known (Migotto et al., 2002; Marques 

et al., 2003; Migotto & Marques, 2006). This region includes 

the states of São Paulo, Rio de Janeiro, and Espírito Santo, the 

last one by far with the less known fauna among the three 

(cf. Marques & Lamas, 2006). Specifically concerning hydroids, 

72 species were recorded so far for the state, 21 anthoathecates 

and 51 leptothecates (Migotto et al., 2002; Grohmann et al., 

2003; Marques et al.,2003). 

Fig. 6. Hydrocoryne iemanja, sp. nov. Diagram showing the sequence of stages in the life cycle of the species: polyp; polyp with budding medusae arising from 

hydrocaulus; young medusa; mature male and female medusae; and planula larva. Drawings are not to scale.


Fig. 7. Hydrocoryne iemanja, sp. nov. Cnidome (A–D polyp tentacle; E–J polyp hydrocaulus; O–P young medusa; K–N and Q–R mature medusa). (A–B) 

Undischarged and discharged heterotrichous microbasic euryteles with inclusion; (C–D) undischarged and discharged stenoteles; (E–F) undischarged and 

discharged heterotrichous microbasic euryteles; (G–H) undischarged and discharged small stenoteles; (I–J) undischarged discharged large stenoteles; (K–L) 

undischarged and discharged small stenoteles; (M–N) undischarged discharged large stenoteles; (O–P) undischarged and discharged holotrichous isorhizae 

(from exumbrella of recently released medusae); (Q–R) undischarged and discharged microbasic mastigophores; (S–T) undischarged and discharged 

desmonemes. Scale bar ¼ 15 mm. 

The differences among the previously described species of 

Hydrocoryne are well defined, although polyps and young 

medusae of H. bodegensis and H. miurensis are morphologically 

indistinguishable from each other (see Kubota, 1988). Indeed, 

polyps of Hydrocoryne iemanja sp. nov. have fewer tentacles 

than the two other species of the genus, but we believe that presently, 

before variation may be better known, polypoid characters 

are not conclusive to distinguish among the congeners. As 

with the two other species of Hydrocoryne, thediagnosticfeatures 

are present in the medusa phase. Hydrocoryne iemanja 

sp. nov. may be clearly set aside from the two other species by 

the distinct marginal tentacles of the medusae—short, with a 

large adaxial nematocyst cluster—an unambiguous character 

useful even for the identification of newly liberated medusae 

(Figure 2). Hydrocoryne iemanja sp. nov. also lacks nematocyst 

clusters on the manubrial lips of mature medusae, and its 

cnidome is distinct, lacking desmonemes only on the hydroid 

phase. 

The presence of desmonemes in the medusae and absence 

in the polyp have been used to include the family 

Hydrocorynidae in the Corynoidea, though Petersen (1990: 

134–135) considered Hydrocorynidae assigned to the 

Sphaerocorynida because of the quadrate manubrium and 

interradial gonads in the medusae, and the absence of a 

whorl of oral tentacles in the hydroids. 

We tentatively considered the longitudinal reproduction as 

a diagnostic character of Hydrocoryne iemanja sp. nov. 

However, the asexual process of longitudinal fission and


Table 1. Compilation of hydrozoan species where fission is already known, and taxonomic arrangements including these species. 

Species Transversal fission Longitudinal fission Classification (Petersen, 1990) 

(only for Capitata) 

Classification 

(Bouillon, 1994) 

Hydrocoryne 

iemanja 

– this work Sphaearocorynida 

Hydrocorynoidea 

Hydrocorynidae 

Corynoidea 

Hydrocorynidae 

Polypodium 

hydriforme 

Bouillon (1985) Bouillon (1985) Not included in the Capitata Narcomedusae 

Polypodiidae 

Hydractinia 

pruvoti 

Bavestrello et al. (2000a) Not included in the Capitata Filifera 

Hydractiniidae 

Unindentified Bavestrello et al. (2000b) Not included in the Capitata Filifera 

Bougainvilloidea 

Staurocladia spp. Hirano et al. (2000) Corynoidea Cladonematidae Tubulariida 

Cladonematidae 

Hydra spp. Hyman (1928) Parke (1900) Moerisiida 

Moerisioidea Hydridae 

Moerisioidea 

Hydridae 

Moerisia lyonsi Ritchie (1915) – Moerisiida 

Moerisioidea Moerisiidae 

Moerisioidea 

Moerisiidae 

Acauloides ilonae Brinckmann-Voss (1967) Brinckmann-Voss (1967) Tubulariida 

Corymorphoidea Acaulidae 

Acauloidea 

Acaulidae 

Boreohydra 

simplex 

Leloup (1952) – Tubulariida 

Corymorphoidea Acaulidae 

Tubularioidea 

Boreohydridae 

Ectopleura larynx Tardent (1963) – Tubulariida Tubularioidea 

Tubulariidae 


Tubulariidae 

Euphysa sp. Brinckmann-Voss (1967) – Tubulariida Corymorphoidea 

Corymorphidae 


Euphysidae 

Protohydra 

leuckarti 

Leloup (1952) – Not included in the study Moerisioidea 

Protohydridae 

Psammohydra 

nana 

Schulz (1950) – Not included in the study Tubularioidea 

Boreohydridae 

Zelounies 

estrambordi 

Gravier-Bonnet (1992) – Not included in the study Not included in the study 

production of the hard plate on the column may exist in other 

species of Hydrocoryne. From laboratory cultures, Kubota 

(1988: 4) found a polyp of Hydrocoryne miurensis ‘bifurcated 

at the lowest portion of hydrocaulus’, but he neither recorded 

a new hard plate nor that the bifurcation apparently had given 

rise to a new, independent polyp. 

The asexual reproduction observed for Hydrocoryne 

iemanja sp. nov. suggests that its hydroid generation may disperse 

and successfully colonize new and favourable habitats. 

However, once the hard plate of the new free-living polyp generated 

by asexual reproduction is negative buoyant, it tends to 

sink fast and, therefore, its dispersal is probably limited to the 

surroundings of the mother colony. The chances of survival of 

the new colony are probably high, because the propagules 

derived by longitudinal fission are large and provided with 

nematocysts, which probably makes them less vulnerable to 

predation than the sexually produced ones (planulae). Also, 

the new large polyp is capable to feed just after settlement, 

enhancing the chance to establish a new colony. Furthermore, 

keeping settlement near the parental colony increases the 

chance of the new hydroid to stay within the ecological tolerance 

limits of the species. 

Besides the possible occurrence of longitudinal fission in other 

species of Hydrocoryne, the universality of this reproductive type 

is restricted in other cnidarians. In general, some kind of longitudinal 

fission occurs in polyps of a few species of Scyphozoa 

(e.g. Aurelia aurita and Catostylus mosaicus; Pérez, 1920; Pitt, 

2000), in which the fission begins at base and runs to the oral 

disc. This kind of reproduction also represents a common 

mode of vegetative proliferation among certain Anthozoa 

(Actiniaria, Scleractinia, Corallimorpharia and Zoanthidae) 

(Cairns, 1988; Ryland, 1997; Fautin, 2002; Geller et al., 2005), 

in which the fission also proceeds from the base towards the 

oral disc (Geller et al., 2005). A detailed analysis on these processes, 

however, indicates that they are not homologous, even 

in less inclusive groups (cf. Daly et al., 2003). The uniqueness 

of the process among the hydrozoans highlights the importance 

of the new finding. 

The Hydrozoa has a vast repertoire of asexual processes, 

which usually includes budding (almost universal and plesiomorphic 

for the species of the group), and the formation of 

different types of propagules (podocysts, frustules), more 

restricted to some specific groups. Fission seems to be rare 

in Hydrozoa, being only reported in a few species (Table 1). 

Fissiparity (either longitudinal or transversal) is an interesting 

character to be investigated concerning its phylogenetic significance. 

Presently, a simple optimization of fissiparity on hydrozoan 

phylogenies is impossible, because of the lack of 

consistent and broad phylogenetic frameworks for the hydrozoansasawhole.However,someinteresting 

taxonomic significance 

inthegroupmaybedepicted.Longitudinal fission is taxonomically 

scattered among Hydrozoa and, most probably, arose 

several independent times in its evolutionary history, while transverse 

fission is characteristic of somewhat taxonomically (though 

still considering classical taxonomy) related groups (Table 1). 

The existence of transverse fission seems to be restricted to the 

Capitata, although this is probably not a monophyletic group 

(cf. Collins et al., 2005, 2006). Many groups presenting transverse 

fission belong to the Aplanulata (a group supported by mitochondrial 

16S and 28S rDNA analyses, and consisting of a putative


clade uniting Hydridae with Candelabridae, Corymorphidae, and 

Tubulariidae; Collins et al., 2005, 2006). However, as noticed by 

Collins et al. (2006: 111), to confirm the monophyly of 

Aplanulata and understand the relationship among their families, 

many taxa have yet to be sampled, for instance Acaulidae, 

Margelopsidae, Paracorynidae and Tricyclusidae. 

Compilatory literature studies overlooked the process of 

longitudinal fission (e.g. Boero et al., 2002), although it has 

already been described. In Hydrozoa, the most similar phenomenon 

occurs in the model organism genus Hydra (Parke, 1900; 

Hyman, 1928). However, longitudinal fission is not an ordinary 

type of asexual reproduction in Hydra, and apparently occurs in 

damaged, regenerating, or abnormal specimens (Hyman, 1928; 

Shostak, 1993). The sequence of the process is the same as we 

found in Hydrocoryne iemanja sp. nov., beginning at the hypostome, 

and requiring several days to reach the basal disc. 

Polypodium hydriforme Ussow, 1887 is a specialized parasitic 

species of sturgeon ova (Raikova, 1994) and, besides its 

odd morphology and life cycle, has been considered by 

some authors as a Hydrozoa (e.g. Smothers et al., 1994), 

though some others have proposed a new class to accommodate 

the species (Raikova, 1988). The free-living, creeping, 

non-sexual stage of this species multiplies by longitudinal 

fission, but this fission begins at the aboral pole and progresses 

towards mouth (Raikova, 2002). 

Cnidarians are a key early diverging lineage among metazoans 

and, therefore, phenomena observed in the group may be 

precursors to derived key characteristics in evolution of 

animals, including traits of reproduction and body plans (e.g. 

Galliot & Schmid, 2002). The data shown above indicates 

that the longitudinal fission in Hydrocoryne iemanja sp. nov. 

is a process distinct from the longitudinal fission exhibited 

by other cnidarians. Therefore, the importance in the understanding 

of this asexual process may be in the investigation 

of regulatory genes in lower metazoans and their significance 

in the production of clonal organisms and evolutionary trends. 

The asexual reproduction is also a divergent point to 

understand the evolution of polarity processes within 

Cnidaria (for more detailed accounts see Geller et al., 2005; 

Collins et al., 2006). The hypothesis of a new method of reproduction, 

the longitudinal fission in the Hydrocoryne iemanja 

sp. nov., may shed light on the understanding of the evolutionary 

pathways in Cnidaria and animals. 

ACKNOWLEDGEMENTS 

We thank F.L. da Silveira (IBUSP) for providing laboratory 

facilities and commenting on the manuscript; Ricardo 

Miyazaki and Augusto A. Tinfre (Água e Estilo) for providing 

aquarium facilities; and H.M. Pacca for the line-art drawings. 

A.C. Morandini was supported by a FAPESP (2003/02433-0) 

postdoctoral scholarship, CEPG/UFRJ–FUJB (ALV 0 2006 

13126-1), CNPq (481399/2007-0) and FAPERJ (E-26/ 

171.150/2006); S.N.S. was supported by CAPES MSc scholarship 

from ‘Programa de Pós-Graduação em Ciências 

Biológicas, Área Zoologia, IBUSP’; A.E.M. is supported by 

CNPq (300194/1994-3) and FAPESP (2006/05821-9); 

A.C. Marquer has financial support from CNPq (55.7333/ 

2005-9, 490348/2006-8, 305735/2006-3), FAPESP (2003/ 

02432-3; 2004/09961-4) and NSF (AToL-EF-0531779). The 

experiments herein performed (cultivation) comply with the 

current laws of Brazil. 

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Correspondence should be addressed to: 

André C. Morandini 

Departamento de Zoologia 

Instituto de Biociênciàs (IB-USP) 

Universidade de São Paulo 

Rua do Matão, trav. 14, n. 101 

São Paulo, SP, 05508-900 

Brazil 

email: andre.morandini@gmail.com

Hydrocoryne iemanja (Cnidaria) - Instituto de Biociências - USP

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