Paracallisoma zivianii, Kilgallen & Lowry, 2015

Kilgallen, Niamh M. & Lowry, James K., 2015, A review of the scopelocheirid amphipods (Crustacea, Amphipoda, Lysianassoidea), with the description of new taxa from Australian waters, Zoosystematics and Evolution 91 (1), pp. 1-43 : 17-19

Paracallisoma zivianii sp. n. Figures 31, 32, 33, 34

Type material.

Holotype, male, 12.0 mm, AM P.69091, east of Flynn Reef, Queensland, Australia (16°37.82'S, 146°23.08'E), 1000 m, baited trap, 7-8 June 1993, coll. J.K. Lowry, P. Freewater & W. Vader, RV Sunbird [QLD-950/SEAS]. Paratype, 1 specimen, 0.8 mm, AM P.69092, east of Flynn Reef, Queensland, Australia (16°37.82'S, 146°23.08'E), 1000 m, baited trap, 6-7 June 1993, coll. J.K. Lowry, P. Freewater & W. Vader, RV Sunbird [QLD-931/SEAS].

Other Australian material examined.

New South Wales: 3 specimens, AM P.48103, [NSW-862]; 4 specimens, AM P.48127, [NSW-863] north-east of Coffs Harbour (30°10.93'S, 153°32.26'E), 963 m, baited trap, 11-12 August 1993, coll. P.B. Berents, R.T. Springthorpe & W. Vader, MV Cheryl Lee. 1 specimen, AM P.49817, [NSW-876]; 4 specimens, AM P.49831, north-east of Coffs Harbour (30°10.89'S, 153°32.22'E), 1000 m, baited trap, 12-13 August 1993, coll. P.B. Berents, R.T. Springthorpe & W. Vader, MV Cheryl Lee [NSW-877].

Queensland: 6 specimens, AM P.50236, [QLD-931/SEAS]; 3 specimens, AM P.50245, [QLD-932/SEAS] east of Flynn Reef (16°37.82'S, 146°23.08'E), 1000 m, baited trap, 6-7 June 1993, coll. J.K. Lowry, P. Freewater & W. Vader, RV Sunbird.

Diagnosis.

Gnathopod 1 coxa margins subparallel. Gnathopod 2 propodus palm transverse, with slightly concave, minutely serrate margin; dactylus reaching corner of palm. Pereopod 5 basis much longer than broad; basis slightly to moderately expanded posteriorly, posterior margin straight. Epimeron 3 posteroventral corner produced into a weak spine. Telson deeply cleft.

Description.

Based on holotype, male, 12.0 mm, AM P.69091.

Lateral cephalic lobe large, down-turned, narrowly rounded apically. Rostrum absent. Eyes apparently absent. Antenna 1 short; accessory flagellum long, 3-articulate, forming cap covering callynophore; primary flagellum 7-articulate, with strong 2-field callynophore; calceoli present. Antenna 2 longer than antenna 1; peduncle with weak brush setae, article 1 greatly enlarged, not covering article 2; flagellum 19-articulate, calceoli present.

Labrum, epistome slightly produced, rounded; upper lip slightly produced, straight. Mandible incisor with slightly convex margins; lacinia mobilis a stemmed, distally expanded, irregularly cusped blade; molar flap-like; palp attached midway, article 2 slender. Maxilla 1 palp 2-articulate. Maxilla 2 inner plate slightly shorter than outer plate; outer plate without long, distally barbed slender setae. Maxilliped outer plate small; palp large, 4-articulate.

Gnathopods 1-4 coxae without setal fringe along ventral margin. Gnathopod 1 coxa large, about as long as coxa 2, margins subparallel; basis slender; ischium long, length 2.2 × width; carpus long, length × 2.0 width, shorter than propodus; propodus margins slightly tapering distally; anterodistal margin with row of long, slender setae, without robust setae just above dactylus; dactylus small, simple, well developed, posterior margin without setae, with two cusps along posterior margin. Gnathopod 2 minutely subchelate; carpus long, length 3.4 × width; propodus long, length 2.5 × width, palm transverse, with slightly concave, minutely serrate margin; dactylus reaching corner of palm. Pereopod 3 weakly prehensile; propodus without posterodistal locking setae; dactylus short, slender. Pereopod 4 weakly prehensile; coxa wider than deep, with subacutely produced posteroventral lobe; propodus without posterodistal locking setae; dactylus short, slender. Pereopod 5 simple; coxa equilobate; basis much longer than broad; basis slightly to moderately expanded posteriorly, posterior margin straight, posteroventral lobe moderately broadened, extending beyond ischium, without row of long pappose setae medially; dactylus short, slender. Pereopod 6 simple; basis expanded posteroproximally, posterior margin tapering distally, with excavate posteroproximal margin, with rounded, moderately broadened posteroventral lobe, produced into merus; dactylus short, slender. Pereopod 7 simple; basis expanded posteriorly, slightly rounded proximally, minutely crenate, posteroventral corner excavate; propodus without anterodistal locking setae; dactylus short, slender.

Epimeron 1 anteroventral corner rounded. Epimeron 3 posteroventral corner produced into a weak spine. Urosomite 1 with dorsally smooth. Uropod 1 peduncle 1.2 × rami length; rami subequal in length. Uropod 2 rami inner ramus slightly shorter than outer ramus. Uropod 3 peduncle short; rami lanceolate, subequal in length, outer ramus 2-articulate, with plumose setae. Telson longer than broad, length 1.5 × breadth, deeply cleft (to 75%).

Etymology.

The species is named for Bert Ziviani, skipper of the RV Sunbird.

Distribution.

Australia: east of Flynn Reef, Queensland, to north-east of Coffs Harbour, New South Wales.

Ecology.

A scavenger, taken in baited traps.

Discussion.

With its strongly developed pereopod 4 posteroventral lobe and relatively narrow and posterodistally lobate pereopod 5 basis, this species is most similar to Paracallisoma alberti , Paracallisoma platepistomum , and Paracallisoma coecum . It can be differentiated from the latter two species by the shape of the gnathopod 1 coxa, which is short with subparallel margins (longer than broad and tapering distally in Paracallisoma platepistomum and Paracallisoma coecum ) and the shape of the pereopod 7 basis (more distinctly excavate posteriorly in Paracallisoma zivianii sp. n.). It differs from Paracallisoma alberti in the shape of the gnathopod 2 palm, which is transverse, and the dactylus, which fits the palm (palm acute, dactylus distinctly shorter than the palm in Paracallisoma alberti ).