Tryphosella betka, Lowry & Stoddart, 2011

Lowry, J. K. & Stoddart, H. E., 2011, The tryphosine genera Photosella gen. nov. and Tryphosella Bonnier, 1893 (Crustacea: Amphipoda: Lysianassoidea: Lysianassidae: Tryphosinae) in Australian waters 2956, Zootaxa 2956 (1), pp. 1-76 : 18-21

Tryphosella betka sp. nov.

( Figs 7–9 )

Tryphosella sp. 368. — Lowry & Smith, 2003: 56.

Type material. HOLOTYPE, female, ovigerous (2 eggs), 4.4 mm, AM P.69292, off Betka Beach , Mallacoota, Victoria, Australia, 37°35.3'S 149°45'E, 8 m, baited trap, clean sand and algal detritus in trap, set 1600 hrs, retrieved 1015 hrs, 29–30 November 1988, J.K. Lowry & S.J. Keable, stn NSW-401 . PARATYPES: 1 male, 5.0 mm, AM P.69293 ; 47 females, 28 males, AM P.69294; same data as Holotype . 207 specimens, AM P.69296, close in to Bastion Point , Mallacoota, Victoria, Australia, 37°35'S 149°46.5'E, 12 m, baited trap, set 1600 hrs, retrieved 1015 hrs, 29–30 November 1988, J.K. Lowry & S.J. Keable, stn NSW-396 . 1 male, 4.5 mm, MV J62288 and 6 males, MV J62289 , Crib Point , Western Port, Victoria, Australia, 38°20.67’S 145°14.74’E, 9 m, sand, Smith-McIntyre grab, 4 March 1965, Marine Studies Group, Fisheries and Wildlife Department, Ministry for Conservation, Victoria, CPBS stn 24N ; 1 male, MV J62287 , same locality and collector, 38°21.35’S 145°13.36’E, 10 m, muddy sand, Smith-McIntyre grab, 9 March 1965, CPBS stn 21S ; 1 male, MV J3510 , same locality and collector, 38°21.63’S 145°15.08’E, 9 m, sand, Smith- McIntyre grab, 23 February 1965, CPBS stn 25S .

Type locality. Off Betka Beach , Mallacoota, Victoria, Australia, 37°35.3'S 149°45'E, 8 m depth .

Etymology. The species is named for its type locality.

Diagnostic description. Head lateral cephalic lobe subtriangular, apically rounded; eyes apparently absent. Antenna 1 peduncular articles 1 and 2 without anterodistal lobe; accessory flagellum not forming cap, terminal article not offset; flagellum with strong 2-field callynophore, robust setae absent from proximal articles; calceoli absent. Antenna 2 peduncular article 3 short; articles 4 and 5 not enlarged; flagellum short, calceoli absent. Epistome/Upper lip separate; epistome produced beyond upper lip, broadly rounded; upper lip produced, rounded apically. Mandible molar with asymmetrically reduced column, proximally setose, distally triturating; palp attached about midway, article 3 with proximal A3-seta. Maxilla 1 outer plate setal-tooth 7 left and right very slightly asymmetrical, left cuspidate along most of sinusoidal inner margin, right cuspidate along most of curved inner margin; palp distal margin with apical robust setae. Maxilliped basis without recurved hook; outer plate with 1 long apical robust seta.

Gnathopod 1 subchelate; coxa small (length 1.2 x breadth), subtriangular, tapering distally; basis sparsely setose along anterior margin; ischium short; carpus short, subequal in length to propodus, without posterior lobe; propodus small, margins subparallel, sparsely setose along posterior margin, palm transverse, entire, convex. Gnathopod 2 palm moderately obtuse. Pereopod 4 coxa without distinct lateral ridge, with a well-developed posteroventral lobe. Pereopod 5 coxa without distinct lateral ridge, without umbo; basis about as long as broad, without photophore, not posteroproximally excavate, posterior margin weakly serrate. Pereopod 7 basis posterodistally produced less than halfway along merus, not posterodistally excavate.

Pleonites 1–3 without mid-dorsal carina, not produced dorsodistally. Epimeron 3 posterior margin smooth, posteroventral corner narrowly rounded. Urosomite 1 not projecting over urosomite 2, with anterodorsal notch and slightly rounded boss. Uropods 1 and 2 outer rami without stout striated robust setae. Uropod 2 inner ramus without constriction. Uropod 3 peduncle without dorsolateral flange, with 2 short apicomedial robust setae; inner and outer rami well developed, outer ramus article 2 short, without plumose setae on rami. Telson deeply cleft, with dorsal robust setae, with 1 apical robust seta on each lobe.

Male (sexually dimorphic characters). Antenna 1 calceoli present, proximal calceoli very large. Antenna 2 peduncular articles 4 and 5 enlarged, calceoli present, proximal calceoli larger than distal calceoli. Gnathopod 1 simple; propodus margins tapering distally, palm absent. Gnathopod 2 propodus palm slightly obtuse.

Remarks. Tryphosella betka belongs to a group of 13 Indo-West Pacific species that have a significantly reduced coxa 1. It also belongs to a small group of four Australian species ( T. betka , T. martrudan , T. toowoomba and T. wangaratta ) that have a simple first gnathopod in the male. Tryphosella betka is distinguished from T. wangaratta by the size of coxa 1 ( T. betka , T. martrudan and T. toowoomba all have a small coxa 1). Tryphosella betka differs from T. martrudan in having a slightly rounded boss on urosomite 1 (a posteriorly-directed elongate rounded boss in T. martrudan ) and a narrowly rounded posteroventral corner on epimeron 3 (produced and acute in T. martrudan ). The males of T. betka differ from those of T. martrudan in having the proximal calceoli on antennae 1 and 2 much larger than the distal calceoli. In both species the adult male antenna 2 is short, an unusual character in the genus Tryphosella . Tryphosella betka differs from T. toowoomba in the shape of the epistome and upper lip, the length of the apical robust setae on the maxilliped outer plate (long in T. betka , short in T. toowoomba ), the shape of epimeron 3 posteroventral corner (narrowly rounded in T. betka , produced and acute in T. toowoomba ) and the number of apical robust setae on the telson (one on each lobe in T. betka , two in T. toowoomba ). Adult males of T. betka also differ from T. toowoomba in not having any plumose setae on the rami of uropod 3, another unusual character in the genus Tryphosella which also occurs in T. chinchilla and T. tuckanarra .

Tryphosella betka appears to be a common shallow-water scavenger in south-eastern Australia, south of Mallacoota.

Distribution. South-eastern Australia, 8–12 m depth.

Figures

FIGURE 7. Tryphosella betka sp. nov. Paratype, male, 4.5 mm, MV J62288, Crib Point, Western Port, Victoria; holotype, female, 4.4 mm, AM P.69292, Mallacoota Inlet, Victoria. Scales represent 0.1 mm.

FIGURE 8. Tryphosella betka sp. nov. Paratype, male, 4.5 mm, MV J62288, Crib Point, Western Port, Victoria; holotype, female, 4.4 mm, AM P.69292, Mallacoota Inlet, Victoria. Scales represent 0.2 mm.

FIGURE 9. Tryphosella betka sp. nov. Paratype, male, 4.5 mm, MV J62288, Crib Point, Western Port, Victoria; holotype, female, 4.4 mm, AM P.69292, Mallacoota Inlet, Victoria. Scales represent 0.2 mm.