Leptochela robusta Stimpson 1860

Leptochela (Leptochela) robusta Stimpson

Leptochela robusta Stimpson, 1860:43.—De Man, 1916:148 [part]; 1920:20 [part], pls. 3, 4 [except fig. 7x].

DIAGNOSIS.—Rostrum variable, dorsal margin usually straight, concave, or sinuous. Carapace wits 3 longitudinal dorsal ridges in breeding females only. Orbital margin entire, not 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. Antennal scale about 2/3 as long as carapace. First pereopod with 25 to 44 spines on opposable margin of movable finger. Second pereopod with 28 to 47 spines on opposable margin of movable finger. Third pereopod with exopod not nearly reaching distal end of ischium. Endopod of 1st pleopod of male not flared distolaterally. Appendix masculina, not including spines, distinctly overreaching appendix interna. Maximum carapace length 6.4 mm.

DESCRIPTION.—Rostrum variable, dorsal margin usually straight, concave, or sinuous, rarely overreaching eyes. Carapace without median dorsal carina in males and nonbreeding females, tricarinate in breeding females. Orbital margin entire, not minutely serrate; suborbital angle rounded, but ventral margin of orbit armed with mesially directed tooth visible only in dorsolateral view (Figure 28a).

Abdomen regularly rounded dorsally on 3 anterior somites and usually on 4th. Fifth somite rounded or obscurely carinate, rarely distinctly so; dorsal margin entire, without elevations of any kind; posterior margin unarmed. Sixth somite about 1.8 times as long as high, with usual tranverse swelling and carina near anterior end of dorsal surface, relatively short and obscure sharp spine on ventrolateral surface, and distinct acute tooth on posterodorsal margin of posterolateral lobe. Telson, not including posterior spines, less than 1½ times as long as 6th somite, about 3 1/3 times as long as wide, armed with 2 pairs of dorsolateral, spines, spaced almost equidistantly, in addition to anterior mesial pair; posterior margin without minute pair of spines between bases of mesial pair of usual 5 pairs of prominent spines.

Eye with papilla on mesial surface of stalk proximal to cornea, cornea distinctly wider than stalk.

Antennular peduncle with stylocerite reaching nearly as far as distolateral margin of basal segment; 2nd segment subequal in length to distal segment in mesial aspect, no more than ½ as long in dorsal aspect. Dorsolateral flagellum about 3 1/3 times as long as carapace; ventromesial flagellum fully 1 1/3 times as long as carapace.

Antennal scale 0.5 to 0.7 as long as carapace, 2.8 to 4.2 times as long as wide, lateral margin faintly sinuous, distal tooth obscurely separated from mesial margin of blade. Distal segments of antennal peduncle nearly 2/3 as wide as scale, reaching to about midlength of scale. Flagellum slightly more than 3 times as long as carapace.

Mouthparts typical of genus. Third maxilliped not nearly reaching distal end of antennal scale, distal segment about 2/5 as long as penultimate segment.

First pereopod overreaching antennal scale by less than length of fingers; fingers 1.5 to 1.7 times as long as palm; dactyl armed with 25 to 44 spines on opposable margin. Second pereopod overreaching antennal scale by less than length of fingers; fingers 1.8 to 2.1 times as long as palm; dactyl armed with 28 to 47 spines on opposable margin. Third pereopod 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 4 stout spines near flexor margin; merus with 6 or 7 longer stout spines near flexor margin; dactyl variable, usually longer than propodus. Fourth pereopod reaching nearly to distal end of ischium of 2nd pereopod when both extended anteriorly; dactyl usually longer, occasionally slightly shorter than propodus. Fifth pereopod similar to and about as long as 4th, reaching at least to midlength of ischium of 2nd pereopod when both extended anteriorly; dactyl slightly shorter than propodus.

Endopod of 1st pleopod of male (Figure 28b,c) subelliptical, little more than 2½ times as long as wide. Appendix masculina (Figure 28d–h) bearing 8 to 11 long spines, longest arising from proximal half of length, distinctly overreaching appendix interna, not including spines. Lateral branch of uropod armed with 9 to 13 movable spines, in addition to setae.

SIZE.—Carapace lengths of males, 3.0–6.0 mm; of nonbreeding females, 3.7–6.2 mm. De Man’s (1920) description of the Siboga material indicates that ovigerous females have a carapace length of about 6.4 mm.

MATERIAL—PHILIPPINE ISLANDS. Cebu; stomach of cardinal fish, Archamia lineolata; 26 June 1970; Y Haneda and F. Tsuji: 1 (4.4) 1 (4.5). Off Zamboanga, Mindanao; 6°54′00″N, 122°04′30″E; surface over depth of 17 m; 10 October 1909; 6:00 p.m.; 10-foot plankton net (ship at anchor); Albatross Sta. 5596: 2 (3.0,6.0)4 (3.7–6.2). Off Tinagta Island, Tawitawi Group, Sulu Archipelago; 5°11′50″N, 119°54′E; 18 m; coral sand; 21 February 1908; 10:08 a.m.; 9-foot Johnston oyster dredge; Albatross Sta. 5159: 1 (4.8). Off Sibutu Island. Sulu Archipelago; 4°32′15″N, 119°22′45″E; 18 m; coral sand; 27 February 1908; 8:36 a.m.; 9-foot Johnston oyster dredge; Albatross Sta. 5169: 1 (5.1).

HABITAT.—Six of the 10 specimens examined were taken at the surface over a depth of 17 meters. Two were found in the stomach of a cardinal fish, and the remaining two were taken on coral sand in 18 meters with a dredge modified from a beam trawl by bolting a rake bar to the heel. The lot of 61 Siboga specimens (De Man, 1920) that almost certainly belong to this species were taken on a bottom of fine and coarse sand with dead shells in 141 meters.

TYPE-LOCALITY.—“Mari Sinensi, prof. 20 org.” It seems reasonably safe to assume that Stimpson’s “Mari Sinensi” refers to what is currently called the South China Sea, because of references in parts of his “Prodromus descriptionis” to “In mari Sinensi Boreali, lat. bor. 23°.” On the same page with his preliminary description of L. (L.) robusta, however, Stimpson records specimens of Sicyonia ocellata “In mari Sinensi quoque, lat. bor. 24°,” a locality in Formosa Strait which connects the South China Sea and the East China Sea, so a shadow of doubt must remain.

DISTRIBUTION.—Known with reasonable certainty only from the “China Sea” off Cebu and the Sulu Archipelago in the Philippine Islands; and north of Pulau Waigeo, Indonesia; at the surface and to a depth of 141 meters.

Whether either L. (L.) robusta or L. (L.) irrobusta live in Japanese waters is uncertain at the present time. The following passage is extracted from remarks kindly translated by Keiji Baba from Kubo (1955:98):

Four species of this genus occur in Japan, including the two reported here for the first time, but one of them, L. robusta, is unavailable to me. Leptochela robusta was first reported by Stimpson (1860) from the East China Sea and it has been recorded subsequently from various localities in the Pacific and Indian oceans. From Japanese waters, it was collected from Toyama-wan by Kikuchi (1932) and from Tanabe-wan (7–27 m), Matoya-wan (7 m), Gokasho-wan (13 m). Ago-wan (10–21 m), and Nanao-wan by Miyadi (1940, 1941). All of Miyadi’s specimens were identified by me at Prof. Miyadi’s request, but recently a question arose about that identification, and I again examined those from Tanabe-wan and Ago-wan. This examination verified that those reported as L. robusta are L. pugnax. Those from Matoya-wan, Gokasho-wan, and Nanao-wan have not been re-examined as yet. The Toyama-wan record by Kikuchi was merely extracted from a list, so it cannot be accepted as a reliable record of L. robusta.