Leptochela hawaiiensis Chace 1976

Leptochela (Leptochela) hawaiiensis

Leptochela robusta.—Rathbun, 1906:929. [Not L. robusta Stimpson, 1860.]

DIAGNOSIS.—Rostrum with dorsal margin variable, straight, convex, concave, or sinuous. Carapace with 3 longitudinal dorsal ridges in breeding females only. Orbital margin minutely serrate dorsolaterally, without mesially directed tooth on ventral portion; suborbital angle unarmed. Fifth abdominal somite entire, without dorsal elevations or posterior tooth. Telson with 1 pair of dorsolateral spines in addition to anterior mesial pair; posterior margin usually with pair (frequently fused) of minute mesial spines in addition to usual 5 pairs of prominent spines. Antennal scale more than ½ but less than 2/3 as long as carapace. First pereopod with 21 to 30 spines on opposable margin of movable finger. Second pereopod with 25 to 36 spines on opposable margin of movable finger. Third pereopod with exopod not nearly reaching distal end of ischium. Endopod of 1st pleopod of male faintly obtuse but not flared distolaterally. Appendix masculina, not including spines, not overreaching appendix interna. Maximum carapace length 3.0 mm.

DESCRIPTION.—Rostrum (Figure 11a,b) with dorsal margin variable, straight, convex, concave, or sinuous, rarely overreaching eyes. Carapace usually without median or dorsolateral carinae in males and nonbreeding females, dorsally tricarinate over most of length in breeding females. Orbital margin (Figure 13a,b) minutely serrate dorsolaterally, ventral portion without mesially directed tooth; suborbital angle rounded.

Abdomen (Figure 11c) usually rounded dorsally on all somites, rarely with suggestion of blunt carina on 5th somite. Fifth somite entire, without dorsal prominences or posterodorsal tooth. Sixth somite fully twice as long as high, bearing usual transverse swelling near anterior end of dorsal surface, slender slightly curved spine on ventrol-lateral surface, and distinct acute tooth on posterodorsal margin of posterolateral lobe (Figure 11d). Telson (Figure 11e) about 1½ times as long as 6th somite, about 2 2/3 times as long as wide, armed with 1 pair of dorsolateral spines slightly posterior to midlength, in addition to anteriormesial pair; posterior margin (Figures 11f, 13c) bearing pair (frequently fused, very rarely absent) of minute mesial spines (Figures 11g, 13d, i) between bases of mesial pair of usual 5 pairs of prominent spines.

Eye (Figure 13a) with papilla on mesial surface of stalk at juncture with cornea, cornea little if at all wider than stalk.

Antennular peduncle (Figure 11h) with stylocerite not reaching so far as distolateral margin of basal segment; 2nd segment about as long as distal segment in ventromesial aspect but much shorter in dorsal aspect.

Antennal scale (Figure 11i) 0.5 to 0.6 as long as carapace, 3.6 to 4.6 times as long as wide, lateral margin concave at about midlength, blade forming rather distinct shoulder at base of distal tooth. Distal segments of antennal peduncle about 4/5 as wide as scale, falling considerably short of midlength of scale; ventral tooth on basal segment neither prominent nor very sharp.

Mouthparts as illustrated (Figure 12a–f). Third maxilliped (Figure 12f) rarely reaching as far as distal end of antennal scale, distal segment nearly 2/5 as long as penultimate segment.

First pereopod (Figure 12g) rarely overreaching antennal scale by more than length of fingers; fingers 1.2 to 1.5 times as long as palm; dactyl (Figure 12h) armed with 21 to 30 spines on opposable margin. Second pereopod (Figure 12i) rarely overreaching antennal scale by as much as length of fingers; fingers 1.4 to 2.0 times as long as palm; dactyl (Figure 12j) armed with 25 to 36 spines on opposable margin. Third pereopod (Figure 12k) overreaching extreme anterior margin of carapace by length of dactyl and about 2/3 of propodus; exopod not nearly reaching distal end of ischium; ischium bearing row of stout setae near extensor margin and 3 slender spines near flexor margin; merus armed with about 5 slender spines near flexor margin; dactyl distinctly shorter than propodus. Fourth pereopod (Figure 12l) reaching nearly to distal end of ischium of 2nd pereopod when both extended anteriorly; dactyl usually shorter than propodus. Fifth pereopod (Figure 12m) similar to and little shorter than 4th, reaching to about midlength of ischium of 2nd pereopod when both extended anteriorly; dactyl usually shorter than propodus.

Endopod of 1st pleopod of male (Figure 13e,f) faintly obtuse but not flared distolaterally. Appendix masculina (Figure 13g,h) bearing 5 long spines and not overreaching appendix interna, without including spines. Lateral branch of uropod (Figure 11e) armed with 5 to 11 movable spines, in addition to setae.

SIZE.—Carapace lengths of males, 2.6–3.0 mm; of nonbreeding females, 2.5–2.8 mm; of nonovigerous breeding females, 2.2, 2.4 mm; of ovigerous females, 2.4, 2.7 mm.

MATERIAL.—HAWAII. South coast of Oahu; Diamond Head Light, S 63°, E 1.3′; 12 m; coral and coral sand; 23.3°C (surface); 27 March 1902; 7:30 p.m.; electric light and dip net at surface at night anchorage; Albatross Sta. 3812: 4 (2.6–2.8) 1 (2.7). Same; Diamond Head Light, S 62°, E 3.9′; 24 m; coral sand and broken shell; 24°C (surface); 6 May 1902; 8:45 p.m.; electrical light and dip net at surface; Albatross Sta. 3921: 36 (2.6–3.0) 17 (25–2.8) (2 ovig. (2.4–2.7)), 1 (2.2) is holotype. South coast of Molokai; Avalu Point, Lanai, S 3/4′; 37 m; hard sand; 24°C (surface); 1 April 1902; 7:40–8:10 p.m.; electric light and dip net or surface tow net; Albatross Sta. 3829: 2 (2.6, 2.7).

HABITAT.—All of the specimens were taken at the surface in early evening over bottoms of coral, coral sand, broken shell, or hard sand in depths of 12 to 37 meters.

TYPE-LOCALITY.—Off Honolulu Harbor entrance, Oahu, Hawaii; surface at night over 24 meters.

DISPOSITION OF TYPES.—The female holotype (USNM 30750) 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.—Known only from the type-series collected at the surface at night south of Oahu and south of Molokai, Hawaii, over depths of 12 to 37 meters.

ETYMOLOGY.—From Hawaii + -ensis (L., denoting locality).