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Leptochela (Leptochela) irrobusta

Comprehensive Description

provided by Smithsonian Contributions to Zoology
Leptochela (Leptochela) irrobusta

Leptochela robusta.—Balss, 1915:17.—De Man, 1916:148 [part]; 1920:19 [part], pl. 4: fig. 7x —Balss, 1921:7—Kemp, 1925:252— Estampador, 1937:491.—Holthuis, 1953:52 —Chace, 1955:5. [Not L. robusta Stimpson, 1860.]

?Leptochela robusta.—De Man, 1902:902.—Borradaile, 1917: 398.—Calman, 1939:188.—Armstrong, 1941:1.—George and Paulinosc, 1973:196, figs. 1–5.

DIAGNOSIS.—Rostrum with dorsal margin usually straight or concave. Carapace with 3 longitudinal dorsal ridges in breeding females only. Orbital margin entire, rarely minutely serrate, with mesially directed tooth on ventral portion; suborbital angle unarmed. Fifth abdominal somite entire, without dorsal elevations or posterior tooth. Telson with 2 pairs of dorsolateral spines in addition to anterior mesial pair; posterior margin without pair of minute mesial spines in addition to usual 5 pairs of prominent spines in adults. Antennal scale nearly 2/3 as long as carapace. First pereopod with 12 to 40 spines on opposable margin of movable ringer. Second pereopod with 16 to 45 spines on opposable margin of movable finger. Third pereopod with exopod not nearly reaching distal end of ischium. Endopod of 1st pleopod of male rounded distolaterally, not flared. Appendix masculina, not including spines, falling slightly short of or barely overreaching appendix interna. Maximum carapace length 5.1 mm.

DESCRIPTION.—Rostrum (Figure 14a,b) variable, dorsal margin usually straight or concave, rarely slightly sinuous or convex, frequently overreaching eyes, rarely extending to level of distal margin of basal segment of antennular peduncle. Carapace with or without obscure median dorsal carina on anterior to 1/3 of length in males and nonbreeding females, tricarinate in breeding females, but lateral carinae often rounded in posterior half of length. Orbital margin (Figure 17a) usually entire, rarely microscopically serrate, especially in juveniles (Figure 16a); suborbital angle rounded, but ventral margin of orbit armed with mesially directed tooth visible only in dorsolateral view (Figure 14c).

Abdomen (Figure 14c) regularly rounded dorsally on 4 anterior somites. Fifth somite rounded or obscurely carinate, rarely distinctly so; dorsal margin entire, without elevations of any kind; posterior margin unarmed. Pleura of 5 anterior somites rounded in adults, those of 3rd, 4th, and 5th somites bearing small tooth in juveniles (Figure 16b). Sixth somite about 1.9 times as long as high, with usual transverse swelling and carina near anterior end of dorsal surface, curved slender spine posteriorly on ventrolateral surface, and distinct acute tooth on posterodorsal margin of posterolateral lobe (Figure 14e). Telson (Figure 14f), not including posterior spines, about 11½times as long as 6th somite, about 3 1/3 times as long as wide, normally armed with 2 pairs of dorsolateral spines varying slightly in size and position, in addition to anterior dorsomesial pair; posterior margin (Figure 14g) without minute pair of mesial spines between bases of mesial pair of usual 5 pairs of prominent spines, except occasionally in juveniles (Figure 16c,d).

Eye (Figure 17a) with papilla on mesial surface of stalk proximal to cornea, cornea slightly wider than stalk, increasing in relative diameter with size.

Antennular peduncle (Figure 14h) with stylocerite reaching nearly as far as distolateral margin of basal segment; 2nd segment subequal in len n ½ as long in dorsal aspect. Dorsolateral flagellum at least 3 times as long as carapace; ventromesial flagellum about 1 1/3 times as long as carapace.

Antennal scale (Figure 14i) slightly more than 0.6 as long as carapace, 3.5 to 4.6 times as long as wide, lateral margin sinuous, distal tooth obscurely separated from mesial margin of blade. Distal segments of antennal peduncle about 2/3 as wide as scale, not reaching midlength of scale. Flagellum at least 3 times as long as carapace.

Mouthparts as illustrated (Figure 15a–f). Third maxilliped (Figure 15f) very rarely overreaching antennal scale, distal segment to 2/5 as long as penultimate segment.

First pereopod (Figure 15g) overreaching antennal scale, occasionally by as much as length of fingers; fingers 1.3 to 2.0 times as long as palm; dactyl (Figure 15h) armed with 12 to 40 spines on opposable margin. Second pereopod (Figure 15i) rarely overreaching antennal scale by more than length of fingers; fingers 1.5 to 2.2 times as long as palm; dactyl (Figure 15j) armed with 16 to 45 spines on opposable margin. Third pereopod (Figure 15k) overreaching extreme anterior margin of carapace by about length of dactyl; exopod falling far short of distal end of ischium; ischium armed with row of about 4 stout spines near flexor margin; merus with about 5 longer stout spines near flexor margin; dactyl variable in length and shape, usually shorter than propodus. Fourth pereopod (Figure 15l) reaching to about distal 1/5 of ischium of second pereopod when both extended anteriorly; dactyl usually longer, occasionally slightly shorter than propodus. Fifth pereopod (Figure 15m) similar to and nearly as long as 4th, reaching at least midlength of ischium of 2nd pereopod when both extended anteriorly; dactyl usually slightly shorter than propodus.

Endopod of first pleopod of male (Figure 17b, c) subelliptical, fully 3 times as long as wide. Appendix masculina (Figures 17d,e, 18a,b) bearing 3 to 7 long spines, usually in distal half, falling slightly short of or extending very little beyond end of appendix interna, not including spines. Lateral branch of uropod (Figure 14f) armed with 8 to 16 movable spines, in addition to setae.

SIZE.—Carapace lengths of males, 1.8–5.1 mm; of nonbreeding females, 2.0–5.1 mm; of nonovigerous breeding females, 3.2–4.3 mm; of ovigerous females, 2.7–4.6 mm. The smallest male has a rudimentary appendix masculina, but appendices masculinae may be less than fully developed in some males with a carapace length up to 3.0 mm.

MATERIAL.—PERSIAN GULF. About 200 m off southwest end of Juraid Island; 27°10′N, 49°51′E; 9 m; massive coral formations interspersed with patches of coral sand; 5 October 1956; 7:45 a.m.; Petersen sample; C. E. Dawson Sta. 7: 1 (2.9).

VIETNAM. Bay of Nha Trang; 1 January to 10 April 1960; Ariel Gallardo Sta. 220a: I (4.3). Same; Sta. 317: 1 (3.6).

PHILIPPINE ISLANDS. Sablayan Anchorage, Mindoro; electric light; 13 December 1908; Albatross: 1 (3.1). Batan Island, Lagonoy Gulf; electric light; 5 June 1909; Albatross: 1 ovig. (4.0). Port Cataingan, Masbate; electric light; 19 April 1908; Albatross: 1 (2.8). Nogas Point, Panay; electric light; 3 February 1908; Albatross: 10 (3.1–3.7) 9 (2.8– 3.8) 4 juv. (1.7–2.3). Mahinog Anchorage, Camiguin Island; electric light; 3 August 1909; Albatross: 2 (2.5, 2.6) 9 (3.0–3.9). Sulu Sea off Panabutan Point, Mindanao; 49 m; green mud, coral sand; 6 February 1908; 9:27 a.m.; 9-foot Tanner beam trawl, mud bag; Albatross Sta. 5131: 1 (5.0). Same; 70 m; green mud, sand; 6 February 1908; 10:40 a.m.; 9-foot Tanner beam trawl, mud bag; Albatross Sta. 5133: 4 (4.7–5.1) 10 (4.2–5.1) (7 ovlg. (4.2–4.6)). Off Balukbaluk Island, near Basilan Island, Sulu Archipelago; 6°44′45″ N, 121°48′ E; 46 m; fine sand; 7 February 1908; 7:22 a.m.; 9-foot Tanner beam trawl, mud bag; Albatross Sta. 5134: 1 (5.0). Off Jolo Island, Sulu Archipelago; 6°06′N, 120°58′50″ E; 35 m; sand, coral; 14 February 1908; 10:55 a.m.; 12-foot Agassiz beam trawl two mud bags; Albatross Sta. 5138: 1 ovig. (4.4).

INDONESIA. Labuan Blanda Island, Selat Butung, Celebes; electric light; 13 December 1909; Albatross: 1 (3.6) 2 (3.6, 3.7).

MARSHALL ISLANDS. Eniwetok Atoll; lagoon; subtidal; 6 June 1946; M. W. Johnson: 1 (3.5). Eniwetok Atoll; lagoon off Eniwetok Island at Bowditch anchorage; surface light at night; 23 May 1946; L. P. Schultz: 2 (2.3) 3 (2.2–2.3) 4 juv. (1.8–2.0). Eniwetok Atoll; Southwest Passage, leeward side of reef 3.7 km south of Rigili Island; surface light at night; 24 May 1946; L. P. Schultz: 10 (2.1–3.1) 18 (2.0–3.3) 10 juv. (1.6–1.9). Bikini Atoll; northeast end of lagoon at Bowditch anchorage; surface light at night; 30 March 1946; L. P. Schultz and V. E. Brock: 42 (2.0–3.2) 83 (2.0–3.4) (8 ovig. (2.7–3.2)) 16 juv. (1.7–2.0). Same; 23 April 1946; L. P. Schultz and J. P. E. Morrison: 46 (2.0–3.1) 46 (2.1–3.7) 8 juv. (1.8–2.0) + 452, 5, & juv. (1 ovig.). Same; 24 April 1946; L. P. Schultz: 47 (1.8–3.4) 46 (2.2–3.4) (5 ovig. (2.9–3.2)) 7 juv. (1.7–2.1) + 1,731 , & juv. (13 ovig.), 1 ovig. (3.0) is holotypc. Same; 25 April 1946; L. P. Schultz: 40 (2.0–3.4) 51 (2.0–3.5) 9 juv. (1.4–1.9) + 1,0053, . & juv. (4 ovig.). Bikini Atoll; lagoon, 7.4 km south of west end of Bikini Island; about 45 m; sand and Halimeda; 26 August 1947; J. P. E. Morrison: I (2.8). Rongelap Atoll; lagoon, 0.9 km off Yugui Island; 24 m; surface light at night; 30 July 1946; E. S. Herald: 20 (2.0–3.0) 36 (2.0–3.0) 74 juv. (1.4–2.0). Rongelap Atoll; lagoon, 0.9 km off I.omuilal Island; 24 m; surface light at night; 31 July 1946; E. S. Herald: 2 (2.3) 3 (2.1–2.9). Rongerik Atoll; lagoon, 183 m off Fniwetak Island; surface light at night; 28 June 1946; L, P. Schultz and E. S. Herald: 12 (2.4–3.4) 5 (2.5–3.1). Ujae Atoll; 60 m outside Ujae Passage; surface at stern of ship under lights; 1951–1952; F. S. MacNeil: 5 (2.7–3.0) 3 (2.0–3.1).

HABITAT.—It will be noted that 2/3 of the lots and all but 24 of the 3876 specimens listed above were taken at surface lights at night. That the species sometimes occurs on or near the bottom, however, is indicated by the 14 specimens trawled at Albatross station 5133 and, especially, by the single male taken in a Petersen grab in the Persian Gulf. The trawled specimens were found in depths of 35 to 70 meters on bottoms of mud or sand, sometimes with fragments of coral or calcareous algae.

TYPE-LOCALITY.—Lagoon of Bikini Atoll, Marshall Islands; surface at night.

DISPOSITION OF TYPES.—The ovigerous female holotype (TJSNM 94729) and the rest of the type-series are deposited in the National Museum of Natural History, Smithsonian Institution, under the catalog numbers of the United States National Museum (USNM).

DISTRIBUTION.—Red Sea and Persian Gulf, Laccadive, Maldive, Andaman, and Nicobar islands, Burma, Western Australia, Indonesia, and Philippine Islands eastward to the Marshall and Samoa islands, at the surface and to depths of 118 and possibly 275 meters. (See L. (L.) robusta.)

ETYMOLOGY.—From ir- (L., = not) + robusta.

DISTRIBUTION.—Korea Strait; northeast of Twiwan; Gulf of Thailand; and Queensland, Australia; 45–111 meters.
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bibliographic citation
Chace, Fenner Albert, Jr. 1976. "Shrimps of the pasiphaeid genus Leptochela with descriptions of three new species (Crustacea: Decapoda: Caridea)." Smithsonian Contributions to Zoology. 1-51. https://doi.org/10.5479/si.00810282.222