Trischizostoma costai, Freire, Pablo R. & Serejo, Cristiana S., 2004

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 : 12-14

Trischizostoma costai sp. nov. ( Fig. 6 )

Material examined. REVIZEE Program, N. O. Thalassa col., stn. E­0540, 21º 12.293' S, 040º 00.884' W to 21º 09.576' S, 040º 00.461' W, 1364m, 04/07/2000; 1 female with oostegites, 34 mm, MNRJ 15144.

Etymology. The name of this species is dedicated in honor to Dr. Paulo Costa, head of the Brazilian Fisheries REVIZEE program — Central Campaign, who always encourages the research on the material obtained in this scientific program.

Diagnosis. Maxilliped palp longer than outer plate. Propodus of gnathopod 1 oval and with 11 short and long stout setae on its extension and 3 pairs of long stout setae distally. Coxa 2 with anterior margin rounded. Carpus of gnathopod 2 longer than ischium. Basis of pereopod 3 3 X propodus length. Telson entire, triangular.

Description. Female, 34 mm ( Fig. 6 A). Rostrum reaching the end of article 1 of peduncle of antenna 1. Eyes well developed. Antenna 1, article 1 of peduncle longer than articles 2–3; callynophore present. Antenna 2, article 5 of peduncle as long as article 4. Mandibles with distal incisors; palp 3­articulate with lateral setae. Maxilla 1, outer plate with 8 distal setae. Maxilla 2, inner and outer plates subequal in length; outer plate with 3 lateral setae. Maxilliped, outer plate longer than inner plate; palp with 4 articles, longer than outer plate.

Gnathopod 1 ( Fig. 6 B) strongly subchelate; coxa reduced and partially covered by coxa 2; propodus inverted, robust, oval; palm with 11 short and long stout setae in its extension and 3 pairs of long stout setae distally. Gnathopod 2 ( Fig. 6 C), coxa with anterior margin rounded; carpus slightly longer than ischium; merus shorter than ischium; propodus shorter than half of carpus; dactylus reduced. Pereopod 3 ( Fig. 6 D), coxa longer than broad; basis 3 X length of propodus; carpus as long as merus, with stout setae on anterior and posterior margins; propodus more than twice length of dactylus, with stout setae on posterior margin; propodus and carpus covered with minute setae on posterior margin. Pereopod 4, coxa posteriorly excavated; basis more than 2 X length of merus; carpus as long as merus and longer than propodus; dactylus with half length of propodus. Pereopod 5, coxa broader than long; basis with posterior lobe; merus as long as carpus and shorter than propodus; dactylus 1/3 of propodus. Pereopods 6 and 7, coxa broader than long; basis with posterior lobe; merus as long as carpus and longer than propodus; dactylus 3 X shorter than propodus.

Uropods 1 and 2, peduncle subequal to outer ramus; inner ramus slightly longer than outer ramus. Uropod 3, peduncle slightly less than half of outer ramus; inner and outer rami subequal in length; outer ramus 2­articulate, with basal article 5 X length of distal article. Telson entire, triangular ( Fig. 6 E).

Remarks. Trischizostoma costai sp. nov. is similar to T. richeri in the shape of the propodus of gnathopod 1, and shape of coxa 2. However, there is a conspicuous distinction in the size of the eyes, much larger in T. richeri , and in the number of stout setae on the palm of gnathopod 1, with 11 setae on T. costai sp. nov., and 19 setae on T. richeri . According to observations on juveniles of T. raschi , it seems that all the setae on the palm appears at the same time and not gradually by each molt. Also, T. costai sp. nov. presents oostegites, indicating that this specimen is a mature female and not a possible juvenile of T. richeri .

Figures

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.