Schizotrema zimmeri, Petrescu, 2018

Petrescu, Iorgu, 2018, On the Family Nannastacidae (Crustacea, Cumacea) from the Australian Museum Collection, Records of the Australian Museum 70 (1), pp. 1-111 : 47

Schizotrema zimmeri sp. nov.

Fig. 53

Schizotrema sordidum .— Zimmer, 1952: 20–21, figs. 32–38. Nec Schizotrema sordidum Calman, 1911: 341 , 363–364,

pl. 34, fig. 22–24.

Holotype ♀, P.64770, Coral Sea, Portlock Reef, reef slope, -9.643° 144.828°, 30 m, scuba, Halimeda , 29 Jan 1993, S. J. Keable, QLD 778 , in AM . Paratype 1♂, Gulf of Thailand (Siam), ZMHB (Zoologisches Museum der Humboldt- Universität, Berlin), lost after examination by the author .

Etymology. The species is dedicated to Carl Zimmer, Director of the Zoologisches Museum der Humboldt- Universität, Berlin, who described the male and noticed some differences between his specimen and Calman’s specimens of Schizotrema sordidum . Zimmer’s specimen is redescribed and elevated to species rank in this paper.

Diagnosis. Carapace 1.3 longer than high, 1.1 longer than large; divided ocular lobe; separate siphons; pseudorostrum 0.5 carapace length; massive anterolateral corner; ventral serrate margin; maxilliped 3 basis 0.9 rest of article’s length, merus as long as carpus and propodus; pereopod 1 propodus 1.08 carpus length; pereopod 2 basis 0.8 rest of article’s length, pereopod 2 dactylus 3 propodus length; uropod peduncle 0.5 pleonite 6 length, exopod 0.8 uropod peduncle length, endopod 3.07 peduncle length.

Description of female. Carapace 0.35 body length, bulky, 1.3 longer than high, 1.1 longer than large; divided ocular lobe; separate siphons; pseudorostrum 0.5 carapace length, upturned; large pair of elevations on posterior part; large antennal notch; prominent blunt anterolateral corner; serrate ventral margin; a few dorsal hairs. ( Fig. 53 A, B ). — Antenna 1 peduncle article 1 0.9 rest of article’s length, with 3 simple setae; article 2 0.9 article 3 length, with process and 2 pedunculate setae; article 3 with 3 pedunculate setae; main flagellum as long as article 3; accessory flagellum with 1 article; aesthetascs 2.4 main flagellum length ( Fig. 53 C ). — Maxilliped 3 basis 0.79 rest of article’s length, its lateral process reaches mero-carpal articulation, with 4 plumose setae; merus 2.8 ischium length, with 2 plumose setae; carpus 1.1 merus length, with 1 simple and 2 plumose setae; propodus as long as merus, with 2 pappose setae; dactylus 0.64 propodus length, with 4 simple setae; with exopod ( Fig. 53 D ). — Pereopod 1 basis 0.4 rest of article’s length, with hyaline fringe and 1 simple seta; merus 1.5 ischium length, with 3 simple setae; carpus 1.8 merus length, with 3 simple setae; propodus 0.9 carpus length, with 6 simple setae; dactylus 0.6 propodus length, with 4 simple setae; with exopod ( Fig. 53 E ). — Pereopod 2 basis 0.8 rest of article’s length, with hyaline fringe; merus 4.5 ischium length, with 1 simple seta; carpus 1.6 merus length, with 1 simple seta; dactylus 3.5 propodus length, with 5 simple setae; with exopod ( Fig. 53 F ). — Pereopods 3–5 with decreasing basis and increasing carpus length; dactylus fused with terminal robust simple seta ( Fig. 53 G–I ). — Uropod peduncle 0.54 pleonite 6 length; exopod 0.78 uropod peduncle length, terminal seta 2.6 exopod length; endopod 3.07 peduncle length, endopod 3.58 exopod length, with scales covered with setulae medially, 1 subterminal and 1 terminal simple seta ( Fig. 53 J–K ).

Remarks. Zimmer (1952) published the description of S. sordidum Calman from Indochina ( Vietnam), and illustrated the anterior part of carapace, cephalothorax in dorsal view, antenna 1, pereopods 1, 2 and 5 and uropod. He stated: “It is not easy to explain the differences in the length of the uropodal exopod, which is only half the length of the endopod according to Calman’s description, however, in the present males it is less 1/3 that length! Despite of these last-mentioned differences, I do not doubt, that these males belong to S. sordidum . ” This is an additional description of a female that matches the Zimmer male, justifying it as a new species. Schizotrema zimmeri sp. nov. is closely related to S. nudum Tafe & Greenwood, 1996 , with similar carapace.

Distribution. Portlock Reef in the Coral Sea, at 30 m depth, and Gulf of Thailand (formerly Gulf of Siam).

Figures

Figure 53. Schizotrema zimmeri sp. nov. Paratype female (A), body, lateral view; (B) carapace, dorsal view; (C) antenna 1: (D) maxilliped 3; (E) pereopod 1; (F) pereopod 2; (G) pereopod 3; (H) pereopod 4; (I) pereopod 5; (J) uropod; (K) uropodal endopod medial margin, detail. Scales: A,B 0.25 mm; C,D, 0.1 mm; E–I, 0.2 mm; J, 0.2 mm; K 0.1.