Elasmopus shepherdi, Hughes & Lowry, 2011

Hughes, L. E. & Lowry, J. K., 2011, The genus Elasmopus (Crustacea: Amphipoda: Maeridae) in Australian waters, Journal of Natural History 45 (9 - 10), pp. 579-628 : 613-616

Elasmopus shepherdi sp. nov.

( Figures 14 , 15 )

Type locality

Cape Northumberland , South Australia (38 ◦ 3 ′ 29 ′′ S, 140 ◦ 39 ′ 43 ′′ E), 1300 m offshore .

Type material

Holotype, dissected male specimen, 10.9 mm, 3 slides, SAM C6675 , 1300 m offshore, Cape Northumberland (38 ◦ 3 ′ 29 ′′ S, 140 ◦ 39 ′ 43 ′′ E), 15 m, red alga community, July 1976, coll. S.A. Shepherd.

Etymology

Named for Dr Scoresby Shepherd, a scientist who has made a significant contribution to marine research, including here as collector of the type material.

Description

Based on holotype male, 10.9 mm, SAM C6675 .

Head. Eyes subovoid; lateral cephalic lobe broad, truncated, anteroventral margin with notch / slit. Antenna 1 longer than antenna 2; flagellum with nine articles; accessory flagellum short, with four articles. Antenna 2 peduncular article 2 cone gland reaching beyond end of peduncular article 3; article 4 shorter in length than article 5. Mandible molar well developed, triturative, accessory setal row with three setae; palp tri-articulate; article 1 twice as long as broad, shorter than article 2; article 2 shorter than article 3, with several slender setae; article 3 strongly falcate, long (four times as long as broad), longer than article 1, with comb of short robust setae along anterodistal margin and three apical setae. Lower lip outer lobes with two pair of ducts; mandibular lobes apically rounded. Maxilla 1 inner plate subrectangular, with three apical plumose setae.

Pereon. Gnathopod 1 coxa anterior margin concave, anteroventral corner produced, rounded; merus with sharp posterodistal tooth; carpus 1.25 times as long as broad, shorter than propodus; propodus anterior margin without setae, medial surface with setal comb, palm acute, convex, entire, defined by posterodistal corner, with posterodistal robust setae. Gnathopod 2 subchelate; basis slender; merus acutely produced distoventrally; carpus compressed, lobate, projecting between merus and propodus; propodus expanded, convex, smooth, anterior margin with rows of long slender setae, posterior margin and medial surface with long slender setal bunches, palm acute, one-third the length of the propodus, without posteroventral corner, subtriangular distomedial shelf with group of robust setae, margin lined with robust setae, subpalmar surface smooth; dactylus with posteroproximal shelf, closing along and reaching end of palm, apically subacute. Pereopod 4 coxa posteroventral lobe with acute posteromedial corner. Pereopods 5–7 narrow distally; basis posterior margin without long slender setae; merus and carpus not broadened; propodus not expanded posterodistally; dactylar ungues simple. Pereopods 5–6 basis posterior margin pectinate, straight,

posteroventral corner broadly rounded. Pereopod 7 basis posterior margin convex, castelloserrate, posteroventral corner broadly rounded.

Pleon. Epimera 1–2 posteroventral corner with small subacute tooth. Epimeron 3 ventral and posteroventral margin smooth, posteroventral corner with small acute tooth. Urosomite 1 with single subtriangular carina. Uropod 1 peduncle with one basofacial robust seta. Uropod 2 outer ramus longer than peduncle, longer than inner ramus. Uropod 3 rami distally truncated, apical robust setae short; inner ramus long (length 2.1 times breadth), subequal in length to outer ramus); outer ramus longer than peduncle. Telson deeply cleft (more than 66%), as long as broad, apical margins concave, with longer outer and shorter inner acute apices, each lobe with three long and two short apical robust setae, with pair of lateral plumose setae.

Remarks

A unicarinate urosomite 1 character is present in only four of the 99 described species of Elasmopus : E. japonicus Stephensen, 1932 from Japan; E. neglectus from New Zealand, E. shepherdi sp. nov. and E. woodjonesi sp. nov. both from southern Australia. Barnard (1974) also listed E. menurte from southern Australia as part of the unicarinate group; however, in this species the carination is extremely subtle, with a more rounded appearance.

Elasmopus shepherdi sp. nov. is very closely related to the southern New Zealand species E. neglectus . Both of these species have a long mandibular palp article 3, male gnathopod 2 propodus smooth, acute palm with dense setal brush and the telson shape and apical setation. Elasmopus shepherdi sp. nov. can be separated from E. neglectus by the male gnathopod 2 propodus palm which is lined with short robust setae, pereopod 6 basis posterior margin which is crenulated not pectinate, the pereopod 7 basis convex posterior margin and the telson without lateral robust setae. The form of the gnathopod 2 palm also separates E. shepherdi sp. nov. from E. woodjonesi sp. nov. (see this species for further remarks).

Distribution

Australia. South Australia: Cape Northumberland (current study).

Figures

Figure 14. Elasmopus shepherdi sp. nov., holotype male, 10.0 mm SAM C6675, off Cape Northumberland, South Australia.

Figure 15. Elasmopus shepherdi sp. nov., holotype male, 10.0 mm, SAM C6675, off Cape Northumberland, South Australia.