Photosella, 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 : 5

Photosella gen. nov.

Diagnostic description. Body not expanded to form a lateral bulge, without dorsal carina.

Antenna 1 accessory flagellum not forming cap, terminal article not offset. Antenna 2 peduncular article 3 short; peduncular article 4 or articles 4 and 5 enlarged in male. Mandible molar with asymmetrically reduced column, proximally setose, distally triturating; palp attached distally. Maxilla 1 setal-tooth 7, left and right symmetrical, cuspidate along most of straight inner margin.

Gnathopod 1 subchelate; coxa large, nearly twice as long as broad, subrectangular, distally subovate; carpus short; propodus margins subparallel. Pereopod 4 with a well-developed posteroventral lobe. Pereopod 5 coxa with or without distinct lateral ridge; basis with photophore, posterior margin without mid-central spine, posteroventral lobe or spine.

Urosomite 1 not projecting over urosomite 2. Uropod 2 inner ramus without constriction. Uropod 3 peduncle without dorsolateral flange; inner and outer rami well developed; plumose setae present on rami in male and female. Telson deeply cleft (more than 64%).

Type species. Tryphosella charlotteae Lowry & Stoddart, 2009 .

Etymology. The name Photosella refers to the photophore on pereopod 5 basis and means ‘little light’.

Included species. Photosella includes 3 species: P. charlotteae ( Lowry & Stoddart, 2009) ; P. miersi ( Stebbing, 1888) ; P. mucronata ( Pirlot, 1936) .

Remarks. The slightly shortened first coxa with a subovate distal margin and the basis of pereopod 5 with a well-developed photophore are both autapomorphies for this genus. Photosella also differs from other tryphosine genera in having strongly developed robust setae along the inner margin of the maxilliped outer plate and densely plumose setae on both rami of the third uropods in both males and females.

Based on other characters such as a distally attached mandibular palp, an asymmetrical, triturating molar and a deeply cleft telson, Photosella is most similar to tryphosine genera such as Cedrosella Barnard & Karaman, 1987 , Coximedon Barnard & Karaman, 1991 and Orenoqueia Bellan-Santini, 1997 . Photosella differs from these genera in having a large first coxa, which is only slightly shorter than coxa 2 and is distally subovate.

Species of Photosella apparently have a true photophore on the basis of pereopod 5. Although the photophore has never been observed emitting light it has all of the external morphological features of a photophore (Eldon Ball, pers. comm.)

Distribution. The genus is currently known from Indonesia ( Pirlot 1936) and Australia ( Stebbing 1888; Lowry & Stoddart 2009 and current study).