Socarnella delectabilis, Hughes, L. E. & Lowry, J. K., 2015

Hughes, L. E. & Lowry, J. K., 2015, Two new species of Lysianassidae Dana, 1849 from Australia: Riwo zeidleri and Socarnella delectabilis (Crustacea: Peracarida: Amphipoda), Zootaxa 3936 (1) : -

Socarnella delectabilis sp. nov. (Lys 161)

( Figs 4 , 5 )

Type material. Holotype male, 8.8 mm, dissected, 3 slides, AM P.69075, north-west of Port Hedland, North West Shelf, Western Australia, eastern Indian Ocean (19°59.0'S 117°51.4'E to 19°59.4'S 117°50.4'E), 42 m, epibenthic sled, 18 February 1983, FRV Soela ( CSIRO stn NWS 01.B1.S); paratype male, AM P.69076, north-west of Port Hedland, North West Shelf, Western Australia, eastern Indian Ocean (19°28.6'S 118°55.0'E to 19°28.2'S 118°55.3'E), 39 m, epibenthic sled, 28 June 1983, FRV Soela ( CSIRO stn NWS 03.B9.S); paratype male, AM P.69077, north-west of Port Hedland, North West Shelf, Western Australia, eastern Indian Ocean (19°29.6'S 118°52.2'E to 19°29.4'S 118°52.8'E), 38 m, epibenthic sled, 30 August 1983, FRV Soela ( CSIRO stn NWS 04.B8.S).

Additional material examined. 2 specimens (1 female dissected, 3 slides and 1 male dissected, 4 slides), NMV J68198 , between Port Hedland and Dampier, Northwest Shelf, Western Australia (19°58’00”S- 19°59’00”S 118°19’00”E- 118°18’00”E), 24 m, trawl, 1 June 1983, coll. Gary Poore & Helen Lew-Ton, RV Soela (NWA-2); 1?immature female, dissected, 3 slides, AM P.69079, north west end, McCluer Island, Northern Territory (11°02'S 132°58'E), 8 m, coral Acropora sp. bases at bommies, 16 October 1982, coll. P. Horner (NT-37); 1 juvenile, AM P.69080, south end of McCluer Island, Northern Territory (11°06'S 133°00'E), 8 m, coral Seriatopora hystrix , 17 October 1982, coll. J.K. Lowry (NT-61); 1 juvenile, AM P.69078, Lee Point, Darwin, Northern Territory (approx. 12°20’S 130°53’48”E), 1 m, old calcareous green alga Halimeda sp. on rock, 2 September 1984, coll. J. Just (NT- 111); 1 juvenile, NTM Cr. 010866, Orontes Reef, Port Essington, Northern Territory (11°4.5’S 132°4.8’E), 10 m, from coral Stylophora pistillata , 16 September 1985, coll. R. Williams (CP 177).

Type locality. North-west of Port Hedland, North West Shelf, Western Australia, eastern Indian Ocean (19°59.0'S 117°51.4'E to 19°59.4'S 117°50.4'E).

Etymology. Latin for delightful, agreeable.

Description. Holotype male, 8.8 mm, AM P.69075.

Head as deep as long; lateral cephalic lobe large, produced anteriorly; rostrum small; eyes subovate, black. Antenna 1 medium length, 0.3 × body; peduncular article 1 length 1.1 × width; article 2 length 0.5 × article 1; article 3 length 0.25 × article 1; accessory flagellum long, 0.6 × primary flagellum, 4-articulate, article 1 subequal to article 2 length; flagellum 6-articulate, callynophore absent, with posterodistal slender setae, without flagellar robust setae, calceoli absent. Antenna 2 subequal in length to antenna 1; peduncle with brush setae absent; article 3 short, 0.4 × article 4; peduncular articles 4–5 not enlarged; flagellum 5-articulate, calceoli absent. Labrum fused with epistome, produced away from posterior margin, rounded. Mandible incisors symmetrical, large, with convex margins; lacinia mobilis absent; accessory setal row without distal setal tuft, left and right rows each with 3 long, slender, multiserrate robust setae; molar developed as small, smooth setose flap; mandibular palp attached proximally, article 1 short, subequal to width; article 2 elongate, slender, length 4.1 × width, 1.8 × article 3, with 4 posterodistal A2-setae; article 3 slender, blade-like, long, length 3.1 × width, without A3-, B3- or D3- setae, with 3 apical E3-setae. Maxilla 1 inner plate narrow with 2 plumose apical seta; outer plate with 11 setalteeth in modified 6/5 arrangement; palp large, 2-articulate, with 6 short terminal conate setae and 1 long subterminal setae, distomedial margin serrate. Maxilla 2 inner and outer plates broad, subequal in length.

Maxilliped inner plate large, subrectangular, apically serrate, with 1 apical robust seta, oblique setal row reduced with 2 setae; outer plate small, subovate, without apical slender or robust setae, 10 vestigial medial robust setae; palp large, 4-articulate; article 2 length 2.8 × width, 1.4 × article 3; article 3 long, slender, length 2 × width; dactylus reduced, subtriangular without subterminal setae, unguis present.

Pereon. Gnathopod 1 simple; coxa large, 0.8 × coxa 2, anterior margin straight, anteroventral rounded, posterior margin straight; basis long, slender, length 2.5 × width, anterior margin smooth, with slender setae; ischium short, length 1.4 × width; merus, posterior margin with a few simple slender setae; carpus subrectangular, short, length 1.1 × width, 0.9 × propodus length, without denticulate patch near posterodistal margin; propodus, subrectangular, length 1.9 × width, tapering distally, posterior margin smooth, straight, posterior margin lined with short robust setae, without long robust setae, palm absent; dactylus weakly recurved, without subterminal spine. Gnathopod 2 subchelate; coxa large, 0.9 times coxa 3 length; ischium length 2.5 × width; carpus long, length 3 × width, posterior margin straight; propodus subovate, short, length 1.8 × width, palm subacute, excavate, 0.5 × propodus posterior margin, defined by posterodistal corner without robust setae; dactylus reaching corner of palm, posterior margin smooth. Pereopod 3 coxa large; merus weakly expanded anteriorly; merus and carpus posterior margin lined with slender setae; propodus with 3 long slender setae and 2 distal locking setae along posterior margin; dactylus weakly recurved. Pereopod 4 coxa deeper than wide, with large posteroventral lobe, anterior margin subquadrate, posterior margin straight; merus weakly expanded anteriorly; merus and carpus posterior margin lined with slender setae; propodus with 1 distal locking seta along posterior margin; dactylus weakly recurved. Pereopod 5 coxa equilobate; basis expanded with posterior margin smooth. Pereopod 6 coxa small, not lobate posteriorly; basis expanded posteriorly with posterior margin weakly concave, smooth; merus expanded; propodus with 1 distal locking seta; dactylus weakly recurved. Pereopod 7 basis expanded posteriorly, posterior margin weakly tapering distally, smooth, posteroventral corner rounded.

Pleon. Pleonites 1–3 dorsally smooth. Epimeron 1–2 subquadrate. Epimeron 3 broadly rounded. Urosomites 1–3 dorsally smooth. Uropod 1 without long fine setae; peduncle with 7 dorsolateral and 2 apicomedial robust setae; outer ramus subequal to inner ramus length; outer ramus with 4 lateral robust seta; inner ramus with 2 robust setae. Uropod 2 without fine setae; peduncle with 1 dorsolateral and 2 apicomedial robust setae; rami subequal in length, outer ramus with 4 dorsal robust setae; inner ramus with 1 robust setae, without constriction. Uropod 3 peduncle long, length 2 × width, with 3 robust setae, without dorsolateral flange; rami lanceolate, inner ramus reduced, 0.7 × outer ramus; outer ramus 1-articulate; outer ramus with 1 dorsolateral robust seta, inner rami without robust setae. Telson length 1.4 × width, cleft (40%), lobes divergent, with 2 apical robust setae, 2 short dorsal slender setae, and 2 marginal penicillate setae.

Remarks. Socarnella delectabilis sp. nov. has a 4-articluate accessory flagellum on antenna 1 and a 40% cleft in the telson while S. bonnieri and S. cavipalmata both have a 5-articulate accessory flagellum and a telson which is apically notched to only 10%. Socarnella delectabilis is most similar to S. cavipalmata with both species having subacute gnathopod 2 propodus with an excavate palm while in S. bonnieri the palm is parachelate and entire. The palm margin is 50% of the propodus posterior margin in S. delectabilis with the propodus 1.8 times as long as broad, while in S. cavipalmata the palm is only 33% with a much longer propodus, being 2.5 times as long as broad.

Distribution. Western Australia: North West Shelf. Northern Territory: Port Essington, Lee Point and McCluer Island (current study).

Figures

FIGURE 4. Socarnella delectabilis sp. nov., holotype male 8.8 mm, AM P. 69075, north-west of Port Hedland, North West Shelf, Western Australia. Scales Head and Antenna 0.2 mm, all other parts 0.1 mm.

FIGURE 5. Socarnella delectabilis sp. nov., holotype male 8.8 mm, AM P. 69075, north-west of Port Hedland, North West Shelf, Western Australia. Scale 0.2 mm.