Leptochela gracilis Stimpson 1860

Leptochela (Leptochela) gracilis Stimpson

Figures 8–10

Leptochela gracilis Stimpson, 1860:42.—Bate, 1888:860, pl. 139: fig. 2.—Balss, 1914:19.—Kemp, 1915: 310.—Urita, 1921:216.—Kemp, 1925:251.—Urita, 1926:424.—Yokoya, 1933:13, 212.—Yu, 1936:86, 99—Yokoya, 1939:263.—Miyadi, 1940a:7, 8, 11.—Yoshida, 1941:21, pl. 4: fig. 4.—Kubo, 1955:99, figs. 1–3.—Liu, 1955:23, pl. 8: figs. 6–14.—Fujino and Miyake, 1970:242.

Leptochela pellucida Boone, 1935:105, pls. 26, 27.

DIAGNOSIS.—Rostrum with dorsal margin straight or sinuous, rarely convex throughout. Carapace without dorsolateral ridges in either males or females. Orbital margin entire, not serrate, without mesially directed tooth on ventral portion; suborbital angle unarmed. Fifth abdominal somite entire, without dorsal elevations but with sharp posterior tooth. Telson with 1 pair 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 47 to 60 spines on opposable margin of movable finger. Second pereopod with 48 to 76 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 distally, not flared distolaterally. Appendix masculina, not including spines, not overreaching appendix interna. Maximum carapace length 9.6 mm.

DESCRIPTION.—Rostrum (Figure 8a) with dorsal margin straight or sinuous, rarely convex throughout, usually reaching to or beyond level of distal end of basal segment of antennular peduncle. Carapace with median dorsal carina on anterior to 2/3 of length, not tricarinate in either males or females. Orbital margin entire, not serrate, without mesially directed tooth on ventral portion; suborbital angle rounded.

Abdomen (Figure 8b) regularly rounded dorsally on 3 anterior somites, usually carinate on posterior part of 4th. Fifth somite carinate, without dorsal prominences but with sharp median tooth projecting from posterior margin. Sixth somite with dorsal tranverse swelling near anterior end pronounced and produced slightly posteriorly, posterolateral lobe (Figure 8c) with distinct acute tooth on posterodorsal margin. Telson (Figure 8d), not including posterior spines, about 1.4 times as long as 6th somite, about 3.3 times as long as wide, margins somewhat sinuous anteriorly, armed with 1 pair of dorsolateral spines near midlength, in addition to anterior mesial pair; posterior margin (Figure 8e) without pair of minute spines between bases of mesial pair of usual 5 pairs of prominent spines (Figure 8f).

Eye with rather slender papilla on mesial surface of stalk, proximal to cornea, cornea slightly wider than stalk.

Antennular peduncle (Figure 8g) with stylocerite reaching nearly as far as distolateral margin of basal segment; 2nd segment nearly as long as distal segment in mesial aspect but distinctly shorter

in dorsal aspect in spite of pronounced lobe on distal margin.

Antennal scale (Figure 8h) 0.6 to 0.7 as long as carapace, 4.4 to 5.0 times as long as wide; lateral margin noticeably sinuous, distal tooth continuous with mesial margin of blade, with barely discernible convexity suggesting subdistal shoulder in latter. Distal segments of antennal peduncle slightly more than ½ as wide as scale, reaching to middle 1/5 of scale; basal segment with distinct ventral spine.

Mouthparts as illustrated (Figure 9a–f). Third maxilliped (Figure 9f) not overreaching antennal scale, distal segment about 2.3 times as long as penultimate segment.

First pereopod (Figure 9g) overreaching antennal scale by no more than length of fingers; fingers 0.9 to 1.3 times as long as palm; dactyl (Figure 9h) armed with 47 to 60 spines on opposable margin. Second pereopod (Figure 9i) overreaching antennal scale by no more than length of fingers; fingers 1.1 to 1.4 times as long as palm; dactyl (Figure 9j) armed with 48 to 76 spines on opposable margin. Third pereopod (Figure 9k) overreaching extreme anterior margin of carapace by about length of dactyl; exopod falling considerably short of distal end of ischium; ischium with row of setae but no spines near extensor margin but with about 5 spines near flexor margin; merus with row of about 6 similar spines near flexor margin; dactyl shorter than propodus. Fourth pereopod (Figure 9l) reaching nearly to distal end of ischium of 2nd pereopod when both extended anteriorly; dactyl longer than propodus. Fifth pereopod (Figure 9m) similar to and little shorter than 4th, reaching nearly to midlength of ischium of 2nd pereopod when both extended anteriorly; dactyl longer than propodus.

Endopod of 1st pleopod of male (Figure 10a,b) subsymmetrically rounded distally, lateral margin slightly concave but not flared distally. Appendix masculina (Figure 10c,d) bearing 7 long spines, not overreaching appendix interna, not including spines. Lateral branch of uropod (Figure 8d) armed with 8 to 15 movable spines (some not visible in figure).

SIZE.—Carapace lengths of males, 7.1–8.8 mm; of nonovigerous females, 8.6, 8.8 mm; of ovigerous females, 8.0–9.6 mm.

MATERIAL.—CHINA. Ch’ingtao, Shantung: 1924; C. T. Urita: 1 (7.1). Fukien; S. F. Light: 4 (7.8–8.8) 17 (8.0–9.6) (15 ovig. (8.0–9.6)).

HABITAT.—Although L. (L.) gracilis is of economic importance in parts of its range and has been mentioned in the literature more frequently than any of the other species of the genus, I am unaware of any discussion of its habits or ecological relationships. This may be due to the fact that much of the important literature is in Japanese or Chinese. It seems to have been taken most commonly on or near the bottom in depths of about 30 to 194 meters, and no record of its occurrence at the surface is known to me.

TYPE-LOCALITY.—Kagoshima Wan, Kyushu, Japan.

DISTRIBUTION.—Off the coasts of China, Korea, and the Japanese islands of Kyushu, Shikoku, and Honshu, except northern end of latter, to a depth of 194 meters. The occurrence of this species in 25 meters southeast of Singapore (Boone, 1935) seems to be considerably beyond its usual range.