Elasmopus piikoi J. L. Barnard 1970

Elasmopus piikoi

DIAGNOSIS OF MALE.—Accessory flagellum about 3-articulate; eyes medium in size, not as dark as in K. pocillimanus, with occasional central ommatidium visible, pigment in alcohol often turning to dark purple or brownish purple; mandibular palp normally falcate; article 5 of gnathopod 1 about 87 percent as long as article 6; anterodistal end of article 2 on gnathopod 2 with pendant lobe on medial and lateral side, slight anterior protrusion above lobe, article 3 broadly lobate, article 5 short, bearing narrow but relatively short, setose posterior lobe, article 6 elongate and strongly tapering, palm very oblique and much longer than posterior margin of article 6, defined by small cusp, distal end with truncate or slightly bilobate process bearing a few spines, midpalmar margin with large truncatoconiform process, dactyl slightly overriding palm and fitting facial recess defined by spine, inner margin of dactyl with large process, margin thus bisinuate, dactyl tending to be stout; posterodistal end of article 6 on pereopods 1–2 with 1 irregularly shaped chisel spine, slightly bifid apically or with small point, other locking spine small, slightly sabre-shaped, dactyl subapically constricted and bearing one stout free spine and 1–2 weak setules; locking spines of pereopods 3–5 normal; pereopods 3–5 bearing several long setae on articles 3–5 and on article 2 of pereopods (3) 4–5, posterior margin of article 2 of regular dimensions and weakly serrate; coxa 6 with unusually broad and slightly truncate anterior lobe; pleonal epimera 1–2 with lateral ridge, posteroventral corners sharply produced, posterior margins sparsely serrate, epimeron 3 with evenly quadrate posteroventral corner, ventral margins of epimera bearing pairs of short spines, no setae; urosomal segments simple; rami of uropods 1–2 with elongate terminal spines but not unusually so; inner ramus of uropod 3 about three-fourths as long as outer ramus, apex of inner ramus slightly tapering and bearing 1 small seta or several spines (right and left differing on same animal occasionally), apex of outer ramus spinose and bearing small article 2; telson elongate, lobes apically excavate and bearing 3 terminal spines each.

FEMALE.—Gnathopod 2 like that of E. molokai; pleonal epimeron 3 like that of young male; inner ramus of uropod 3 broadly truncate and spinose; pereopods 3–5 lacking setae (no female at hand nearly as large as males).

YOUNG MALE.—Gnathopod 2 with more spines on middle and distal palmar processes than in adult but processes smaller, dactyl weakly sinuate; pleonal epimeron 3 with posteroventral tooth like epimera 1–2, spines on ventral margin occurring singly in each set; inner ramus of uropod 3 with strongly spinose apex; telson with 2 spines on each lobe.

JUVENILE.—Pleonal epimera like young male but often lacking spines; inner ramus of uropod 3 like adult male, tapering and bearing one apical seta or one seta and one spine; telson with 2 spines on each apex.

HOLOTYPE.—Bishop Museum collections, catalog number 7272, male, 5.0 mm.

TYPE-LOCALITY.—JLB Hawaii 13, Kaneohe Bay, Oahu, 3–4 m, corals, algae, corallines, 8 April 1967.

MATERIAL.—JLB Hawaii 2(32), 3(1), 12(12), 13(14), 14(25), 17(2).

RELATIONSHIP.—A sympatric resemblance occurs with E. pocillimanus (Bate) and E. molokai, new species, and differentiation of juveniles from similar stages of the latter species is difficult, except for the short telson of E. molokai. A judgment of this character is difficult to make without dissection until considerable experience with the material has been obtained. Gnathopods of the adult male arc clearly different, and the presence of epimeral setae on adult female E. molokai is characteristic. The pair of sabre-spines on pereopods 1–2 of E. pocillimanus is definitive of that species in all stages.

Elasmopus piikoi gnathopod 2 of the young male resembles that of E. calliactis Edmondson, but the eyes devoid of black pigment distinguish all stages of the latter species.

Adult males of E. piikoi differ from E. rapax Costa (J. L. Barnard, 1962b) in the absence of the fourth palmar process on gnathopod 2 that forms a long conical lateral tooth. Males, females, and large juveniles of E. rapax have several sharp serrations on epimeron 3. The telson of E. rapax has spines only on the apicolateral notch, and the medial projecting portion is smooth. Article 2 on the outer ramus of uropod 3 is absent in E. rapax.

Elasmopus holgurus J. L. Barnard (1962b) from California differs from E. piikoi in the absence of a defining tooth on the palm of male gnathopod 2, although the facial ridge and spine into which the dactylar apex fits are present in both species.

DISTRIBUTION.—Hawaiian Islands.