Trischizostoma

Freire, Pablo R. & Serejo, Cristiana S., 2004, The genus Trischizostoma (Crustacea: Amphipoda: Trischizostomidae) from the Southwest Atlantic, collected by the REVIZEE Program, Zootaxa 645, pp. 1-15 : 2-3

Key to Brazilian Trischizostoma species (all from entire telson group)

1. Coxa 2 subtriangular and with sharp anterior margin .................................................. 2

­ Coxa 2 subquadrate and with rounded anterior margin ............................................... 3

2. Eyes present; gnathopod 1 propodus subtriangular, telson distally emarginate ( Fig. 4 ) ...................................................................................................... Trischizostoma raschi

­ Eyes absent; gnathopod 1 propodus subquadrate and with anterior lobe, telson distally rounded ( Fig. 2 ) ................................................................. Trischizostoma denticulatum

3. Gnathopod 1 propodus quadrate; pereopod 3 basis 2 X length of propodus, telson distally truncate ( Fig. 3 )........................................................ Trischizostoma longirostrum

­ Gnathopod 1 propodus oval; pereopod 3 basis 3 X length of propodus, telson distally subacute......................................................................................................................... 4

4. Eyes very large, covering almost the entire head; gnathopod 1 palm with 19 short robust setae and 3 pairs of long robust setae distally (Fig. 5) ... Trischizostoma richeri

­ Eyes large, covering half­length of head; gnathopod 1 palm with 11 short and long robust setae and 3 pairs of long stout setae distally ( Fig. 6 ) .......................................... ......................................................................................... Trischizostoma costai sp. nov.

Figures

FIGURE 2. Trischizostoma denticulatum Ledoyer, 1978, female, 32 mm, MNRJ 13702. A, habitus; B, gnathopod 1; C, gnathopod 2; D, pereopod 3; E, telson. Scales bars: A, 5 mm; B – E, 1 mm.

FIGURE 3. Trischizostoma longirostrum Chevreux, 1919, female, 47 mm, MNRJ 15141. A, habitus; B, gnathopod 1; C, gnathopod 2; D, pereopod 3; E, telson. Scales bars: A, 5 mm; B – D, 1 mm; E, 0.5 mm.

FIGURE 4. Trischizostoma raschi Boeck, 1861, female, 39 mm, MNRJ 151439. A, habitus; B, gnathopod 1; C, gnathopod 2; D, pereopod 3; E, telson; F, gnathopod 1 of juvenile, 4 mm, MNRJ 15143. Scales bars: A, 5 mm; B – D, 1 mm; E – F, 0.5 mm.

FIGURE 6. Trischizostoma costai sp. nov., female, 34 mm, MNRJ 15144. A, habitus; B, gnathopod 1; C, gnathopod 2; D, pereopod 3; E, telson. Scales bars: A, 5 mm; B, 1 mm; C, 2 mm; D – E, 1 mm.