Rhynchothorax architectus Child, 1979

Rhynchothorax architectus Child, 1979 View in CoL

Fig. 65 View FIGURE 65

Rhynchothorax architectus Child 1979: 68 View in CoL . Child 1982: 374. Stock 1986: 405. Stock 1989: 95 (text).

Material: 3.— 1 fem., 1 juv. ( INVEMAR), under stone blocks on sandy bottom, ca. 0.5 m, 30.XII.1985 .

9.—3 fem. ( ZMA 3378), under stone blocks on sandy bottom, 0.5–1 m, 29.XII.1985. 3 males, 2 fem., 2 juv. ( SMF 1534 View Materials ), under stone blocks on sandy bottom, 0–0.5 m, 31.XII.1985 . 3 males (1 ov.) ( SMF 1535 View Materials ), under stone blocks on sandy bottom, 0–1 m, 28.I.1986 .

22.— 3 males (ov.), 14 fem. ( SMF 1536 View Materials ), on Halimeda on reef top, mesolittoral, 14.IV.1986 .

31.— 1 male, 1 fem. ( SMF 1537 View Materials ), under rocks on sandy bottom, mesolittoral, 9.IV.1986 .

Description of male: Trunk outline dorsally oval and robust, all segments separated; crurigers close together, separated by slightly more than 1/5 of their diameter; crurigers 1 and 2 with short, often ramified postero-lateral tubercle. Segments 1–4 dorsally either without or each with 1–2 bulbous tubercles, very variably developed (see Child 1979: 70, Fig. 24 View FIGURE 24 ). No eyes; ocular process with two peaks, broader than long. First trunk segment with processes directed obliquely to the anterior and serve as origins to palps; these processes are longer than broad, some of them bearing a small tubercle near their distal edge. Abdomen directed horizontally, more than half its length overtopping coxae 1 of fourth leg. Proboscis oval, robust, about 1/2 trunk length.

Palp 4-articled; all articles bearing small tubercles, those on terminal article mostly branched; first article the longest, 3.2 times as long as second; third article almost twice longer than second, bearing dorsally at midlength a robust process with short spines, which is almost as long as the length and the diameter of second article; fourth article directed dorsally, its anterior (= ventral) face densely covered with mostly branched tubercles, each of them with several short spines; fourth article almost as long as third. Oviger 10-articled, typical for the genus; articles 1–3, 5 and 7–10 short and robust, of similar lengths; articles 4 and 6 of similar diameter, but slightly longer; articles 7–10 on their inner face with some short and mostly forked spines; terminal article almost round, with a robust curved claw and on its inner margin a finely dentated membrane.

Legs rather robust, but proportions of articles conspicuously variable (comp. Child 1979: 71; Figs. 25a, e View FIGURE 25 ); coxa 1 as long as broad or a trifle broader than long, antero- and postero-laterally almost exclusively with a branched tubercle in different size; coxa 2 the longest of all coxae, 1.3 times as long as coxa 3; coxa 2 in ventral or ventro-lateral position with a robust process, shorter than diameter of article; femur and tibiae of almost equal length, femur most robust article; the tibiae with a dorso-distal long seta; cement gland ducts ventro-lateral on femur, a slender tube, shorter than diameter of femur; tarsus as long as broad, with 2 short ventral setae; propodus feebly curved, relatively slender; sole without heel, with about 8 short setae; main claw robust and feebly curved, 1/3 length of propodus; auxiliary claw slender and feebly curved, of about 2/3 length of main claw.

Measurements: Length of trunk 0.98; width across first crurigers 0.52; length of abdomen 0.23; length of proboscis 0.48. Lengths of articles of leg 3: coxa 1—0.09; coxa 2—0.12; coxa 3—0.09; femur 0.22; tibia 1— 0.21; tibia 2—0.20; tarsus 0.04; propodus 0.20; main claw 0.07; auxiliary claw 0.04.

Female: In habitus similar to male, but the tubercles on trunk segments and on coxa 1 generally weaker or even absent. Females mostly larger than males, on average measuring ca. 1.2.

Remarks: R. architectus shows close similarities to Rhynchothorax alcicornis Krapp, 1973 from the European Mediterranean and Rhynchothorax arenicolus Stock, 1989 from Curaçao. The first of these species is distinguished from R. architectus by its significantly shorter terminal palp article, which is adorned with fewer and higher tubercles (comp. Krapp 1973: 124, Fig. 1 View FIGURE 1 ; Arnaud & Krapp 1990: 3, Fig. 2 View FIGURE 2 ). R. arenicolus apparently has a 5-articled palp, and the palp and leg articles are adorned with more numerous small round tubercles. The cement gland duct in R. arenicolus is shorter than in R. architectus (comp. Stock 1989: 91, Figs. 19–30 View FIGURE 19 View FIGURE 20 View FIGURE 21 View FIGURE 22 View FIGURE 23 View FIGURE 24 View FIGURE 25 View FIGURE 26 View FIGURE 27 View FIGURE 28 View FIGURE 29 View FIGURE 30 ).

Owing to the considerable variability of characters, the distinction of various Rhynchothorax species is problematic. The development of the tubercles on the trunk segments and proboscis in Colombian material of R. architectus is feebler than Child (1979) reported for specimens from Panamá. In contrast the lateral tubercles on coxa 1 of the legs are larger and frequently branched. The cement gland duct in males from Colombia is distinctly shorter than in material from Panamá. Stock had only 3 specimens of R. arenicolus , two of them males, which are close to R. architectus , but the range of variability of that species is not yet sufficiently known.

As far as known, R. architectus is a psammophilous species of the uppermost shallow waters. In the Santa Marta region it was collected with a specific sampling method: flat-lying rocks were abruptly lifted from the sandy bottom, and the resulting suction raised organisms and the uppermost layers of sand into the water column where they could be caught in a fine-meshed net.

Distribution: Pacific and Caribbean coasts of Panamá ( Child 1979: 68), Belize (Child 1982: 374) and Caribbean coast of Colombia.