Mocallichirus mocambiquensis ( Sakai, 2004 )

Poore, Gary C. B., 2023, New records and one new species of Callichiridae (Crustacea, Axiidea) from the Indo-West Pacific, with keys to species of Corallianassa, Lepidophthalmus and Neocallichirus, Memoirs of Museum Victoria (Mem. Mus. Vic.) 82, pp. 71-95 : 77-79

Mocallichirus mocambiquensis ( Sakai, 2004)

Figure 5

Callianassa mocambiquensis Sakai, 2004: 585–592 , figs 15–

17.— Sakai, 2005: 93. Trypaea mocambiquensis .— Sakai, 2011: 404. Mocallichirus mocambiquensis .— Poore et al., 2019: 146.—

Robles et al., 2020.

Material examined. Holotype. Mozambique Channel , 26–28 m, MNHN Th1452 (male [somewhat shrivelled], 3.3 mm) . Paratypes. Collected with holotype, MNHN Th1453 (3 males, 3.0 mm) .

Madagascar. Nosy Bé , across bay from CNRO complex, off Lokobe Reserve, 13.4139° S, 48.3056° E, 1–3 m, seagrass (stn MGNW-23), UF 14337 * (female, 4.2 mm). Nosy Bé, E of Hellville, at CNRO complex, 13.4069° S, 48.2917° E, 0–3 m (stn MGNW-26), UF 13903 (female, 4.5 mm); (stn MGNW-49), UF 13986 (male, 4.5 mm); (stn MGNW-26), UF 14462 (female, 4.5 mm). Nosy Bé, Plante stn NM2, MNHN IU-2016-8087 (male, 7.5 mm). Nosy Bé, Faubert, 10 m, MNHN IU-2016-8088 (male, 9.8 mm) .

Supplementary description. Male. Carapace quarter length of total; cervical groove at 0.8 length of carapace, well incised on dorsum; dorsal oval weak; cardiac pore present, without cardiac prominence. Rostrum broadly triangular, exceeding anterolateral lobes. Pleonite 1 with sclerified tergite not extending laterally, with shallow transverse groove; pleonite 2 1.3 times as long as pleonite 1 tergite; pleonites 3–5 expanded laterally with dense setose areas; pleonite 6 waisted posteriorly.

Eyestalk broader than long, basal height two-thirds length, lateral margin evenly convex, mesiodistal apex produced as acute lobe; cornea about 0.2 width, distolateral. Antennule 1.8 times basal width of both eyestalks, article 3 setose ventrolaterally. Antenna 2.1 times basal width of both eyestalks; scaphocerite absent. Maxilliped 1 with disc-like endopod, broad exopod, epipod with attenuated anterior lobe beyond lateral shoulder.

Major pereopod 1 (cheliped) ischium denticulate, distal tooth strongest; merus with 3 angled teeth over second quarter of lower margin; carpus waisted proximally; propodus upper margin carinate, 1.1 times as long as greatest width, with mesial edge produced and a tubercle at base of dactylus; fixed finger 0.6 times palm upper margin, cutting edge with denticulate lateral margin; dactylus as long as fixed finger, cutting edge with weakly crenellate lateral margin.

Minor pereopod 1 (cheliped) 0.7 times length of major; ischium weakly denticulate; merus lower margin smooth; carpus waisted proximally; propodus upper margin 0.85 times as long as greatest width, with mesial edge slightly produced at base of dactylus; fixed finger 1.3 times palm upper margin, cutting edge smooth; dactylus as long as fixed finger, cutting edge with weak tooth.

Pleopod 1 uniarticulate, curved, with oblique curved apical notch. Pleopod 2 uniarticulate, shorter than pleopod 1, tapering beyond greatest width at midpoint to oblique truncate apex, without appendices.

Uropod endopod 1.8 times as long as wide, with marginal setae, cluster of distal setae on upper face; exopod 1.5 times as wide as anterior margin, dorsal plate almost semicircular, well distinguished from distal margin, with few spiniform setae, posterodistal angle rounded.

Telson dorsally convex, 1.1 times as long as wide, lateral margins almost parallel over most of length, tapering over distal third to broadly rounded apex, with pair of clusters of distolateral setae but otherwise with few setae.

Female. Major pereopod 1 (cheliped) ischium as in male; merus with 2 angled teeth over second quarter of lower margin; carpus as in male; propodus upper margin carinate, 1.3 times as long as greatest width, with mesial edge produced and a tubercle at base of dactylus; fixed finger 0.3 times upper margin, cutting edge with strong step on lateral margin; dactylus as long as fixed finger, cutting edge with blunt basal tooth, notch, triangular tooth. Minor pereopod 1 essentially as in male.

Pleopod 1 with 2 articles, curved, article 2 with rounded apex. Pleopod 2 biramous; endopod 1.1 times length of peduncle, 5 times as long as wide, tapering to simple rounded apex, without appendix interna; exopod half as long as endopod.

Size. Cl. to 9.8 mm. Distribution. Western Indian Ocean ( Mozambique Channel [type locality], Madagascar); 1–28 m.

Remarks. Sakai (2011) included the species in Trypaea , a genus of Callianassidae s.s., in which he included more than 50 species. The epipod on maxilliped 1 (fig. 5g) and pleopods (fig. 5j, k, n, o) confirm its placement in Callichiridae , consistent with genetic affinities ( Robles et al., 2020).

The species is immediately recognisable from the shape of the telson, appearing almost pentagonal, the lateral margins almost parallel over most of length and the posterior third tapering to a rounded obtuse apex, and convex in lateral view (fig. 4). Sakai’s figure (2004, fig. 17E) of the telson of the somewhat shrivelled holotype is distorted and the chelipeds ( Sakai, 2004: fig. 16A, B) are of a juvenile form. Sakai (2004) reported that the male holotype possessed a “two-segmented” pleopod 1 and lacked pleopod 2. A re-examination of the holotype revealed simple pleopods 1 and 2. Two of the three paratype males examined had no pleopods. All these are smaller (3.5 mm) than the male collected at Madagascar (4.5 mm), which has a 1-articled pleopod 1 with a distal notch (fig. 5j) and a simple pleopod 2 with a truncate apex (fig. 5k).