Alpheus malleator Dana, 1852

Pasinatto, Karmine, Mantelatto, Fernando L. & Terossi, Mariana, 2020, First zoeal stage of the snapping shrimps Alpheus formosus Gibbes, 1850 and Alpheus malleator Dana, 1852 (Caridea: Alpheidae), with new characters to the genus, Zootaxa 4820 (3), pp. 540-550 : 542-546

Alpheus malleator Dana, 1852

Zoea I

Carapace length: 0.52 ± 0.03 mm (n = 10 larvae)

Cephalothorax ( Fig. 2A, 2B ): rostrum absent; pterygostomian spine present; eyes sessile.

Antennule ( Fig. 2C ): peduncle 2-segmented; endopod as a plumose seta; exopod with 4 terminal aesthetascs (1 more robust) and 1 terminal plumose seta.

Antenna ( Fig. 2D ): peduncle 2-segmented with 1 medial distal spiniform projection near the endopod; endopod with 1 terminal plumose seta and 1 medial distal spiniform projection; exopod (scaphocerite) 6-segmented with 11 plumose setae (2, 1, 2, 1, 1, 4), plus a medial tubercle in the proximal segment and 1 simple seta in the distal segment.

Mandible: palp absent.

Maxillule ( Fig. 2E ): coxa with 6 (1 medial simple, 3 terminal simple, 1 terminal serrulate plumose, larger in proximal region, 1 lateral simple) setae; base with 2 spiniform projections and 1 lateral simple seta; endopod with 1 terminal plumoserrulate and 1 lateral simple setae; exopod absent.

Maxilla ( Fig. 2F ): coxa with 2 medial simple setae; base bilobed, each lobe with 5 medial simple setae (median seta shorter); endopod with 3 medial (1 proximal and 2 distal) simple setae and 2 terminal long (1 simple and 1 plumose) setae, with microtrichia; exopod (scaphognathite) with 5 plumose setae, with microtrichia.

First maxilliped ( Fig. 2G ): coxa with 1 medial distal simple seta; base with 7 medial simple setae arranged 2+2+2+1; endopod 2-segmented with 1 medial distal simple seta, 5 [4 simple (1 medial + 1 lateral + 2 terminal) and 1 terminal serrulate] setae; exopod 4-segmented with 0, 0, 2, 2 terminal natatory plumose setae plus 1 lateral proximal simple seta on third segment.

Second maxilliped ( Fig. 2H ): coxa without setae; base with 4 medial simple setae arranged 1+2+1; endopod 4-segmented with 1 medial distal simple, 0, 1 medial distal serrulate seta, 5 (1 medial simple, 3 lateral simple and 1 terminal serrulate) setae; exopod 4-segmented with 0, 1, 2, 2 terminal natatory plumose setae plus 1 terminal simple seta on second segment.

Third maxilliped ( Fig. 2I ): coxa with 1 medial distal simple seta; base with 1 medial simple seta; endopod 4segmented with 0, 0, 3 (2 medial proximal and 1 lateral distal), 3 (2 lateral and 1 terminal) simple setae; exopod 4-segmented with 0, 2, 2, 2 terminal natatory plumose setae plus 2 (1 medial and 1 lateral) simple setae on second segment.

Pereopod ( Fig. 2J ): first as a biramous bud.

Pleon ( Fig. 2A, 2K ): with 5 somites, presence of simple dorsal setae on the somites ( Figs. 2L , 3A, 3D, 3E, 3F ); lateral spines absent; pleopods absent; anal spine present ( Fig. 2M ).

Telson ( Fig. 2M ): triangular, with 7+7 (5 inners plumose, 2 outers plumose laterally) setae, 4 inner setae with shorter setules in the proximal region, inner pair shorter; 6 inner pairs with a row of denticles in the distal margin, 4 innermost pairs with marginal spines.

Figures

FIGURE 2. Alpheus malleator Dana, 1852. Zoea I. A. Lateral view; B. Carapace; C. Left antennule; D. Left antenna; E. Left maxillule; F. Left maxilla; G. Left first maxilliped; H. Left second maxilliped; I. Left third maxilliped; J. Left first pereopod; K. Pleon, lateral view; L. Fourth somite of pleon, lateral view; M. Telson, dorsal view. Scale bars: A, L, K. 0.15mm; B–D, G–J, M. 0.07 mm; E, F. 0.04 mm.

FIGURE 3. Alpheus formosus Gibbes, 1850 (B, C, G, H) and Alpheus malleator Dana, 1852 (A, D–F). Zoea I. Light microscopy (A), Scanning electron microscopy (B–H).A–F. Simple dorsal setae on the pleon (white arrows). G–H. Denticles (black arrows) and spines (black arrowheads) in the posterior margin of the telson. Scale bars: A. 100 µm; B–D, F–H. 10 µm; E. 20 µm.