Dilocarcinus septemdentatus ( Herbst, 1783 )

Dilocarcinus septemdentatus ( Herbst, 1783) View in CoL

Description of the first juvenile stage.

Carapace ( Fig. 1A View Figure 1 ) slightly wider than long, subquadrangular, posterior margin wider than anterior one, convex in anteroposterior direction; front bilobed, slightly deflected. Dorsal region convex with simple and plumose setae sparsely; early differentiation of the gastric, cardiac, intestinal and branchial regions. Anterolateral margin with minute spine. Small red and brown spots over the entire dorsal region of carapace. Sternum ( Fig. 1B View Figure 1 ) without setae.

Abdomen ( Fig. 1C View Figure 1 ) attached to sternum, with six somites wider than long, extending beyond transverse suture of fourth sternite. Ventrally with four pairs of pleopodal buds from second to fifth somite.

Telson subtriangular, with small simple and plumose setae scattered on dorsal region.

Antennule ( Fig. 2 View Figure 2 ) with the basal segment welldeveloped with 8–11 simple and 12–15 plumose setae. Peduncle two-segmented, first segment smooth, second segment with 4 simple setae. Endopod (ventral flagellum) two-segmented, proximal segment with 1 subterminal simple seta, distal segment with 4 simple setae (2 subterminal and 2 terminal). Exopod (dorsal flagellum) 3-segmented; first segment smooth; second segment with 1 simple seta and 4 aesthetascs ending in a globose tip with a sharp point; third segment with 2 simple setae and 4 aesthetascs ending in a globose tip with a sharp point.

Antenna ( Fig. 3 View Figure 3 ) with peduncle three-segmented; first segment with 2 simple and 1 plumose setae; second segment with 3 simple setae; third segment with 1 simple seta. Antennal flagellum with 5 segments bearing 0, 0, 3, 2, 3,simple setae, one of which extremely long.

Mandible ( Fig. 4 View Figure 4 ) with cutting blade and three segmented palp with 0, 2, 10 plumose setae.

Maxillule ( Fig. 5) with coxal endite with 10–13 plumose setae.Basal endite with 1–2 simple and19–23 plumose setae. Endopod unsegmented, with 2 terminal plumose setae. Protopod with 2 long plumose setae.

Maxilla ( Fig. 6 View Figure 6 ) with coxal endite bilobed, proximal lobe without setae and distal lobe with 1 plumose seta. Basal endite bilobed with 3–4 simple and 8 plumose setae on the proximal lobe; distal lobe with 4–6 simple and 5 plumose setae. Endopod unsegmented with 1 plumose seta. Exopod (scaphognathite) with 82–90 marginal plumose setae and 8–12 simple setae on the dorsal surface.

First maxilliped ( Fig. 7) with coxal endite with 14–17 plumose setae. Basal endite with 28–34 plumose setae. Endopod unsegmented with 0–1 proximal plumose seta and 6–8 distal plumose setae. Exopod two-segmented with 6–13 plumose setae on the proximal segment and 4 long terminal plumose setae on the distal segment. Epipod with 8–12 proximal plumose setae, and 16–24 median and terminal plumose setae. No gills present.

Second maxilliped ( Fig. 8 View Figure 8 ) with protopod smooth. Endopod with five segments. Ischium with 1–2 simple and 5–9 plumose setae. Merus with 1–2 simple and 3–4 plumose setae. Carpus with 0–1 plumose seta. Propodus with 2 simple and 8–10 plumose setae. Dactylus with 10–14 plumose setae. Exopod two-segmented, proximal segment with 12–16 plumose setae; distal segment with 4 long terminal plumose setae. Epipod with 9–14 plumose setae. Podobranch rudimentary.

Third maxilliped ( Fig. 9) protopod with 6–9 simple and 22–31 plumose setae. Endopod five-segmented. Ischium with 12–17 simple and 12–11 plumose setae. Merus with 7–9 simple and 5–7 plumose setae. Carpus with 3–4 simple and 3–4 plumose setae. Propodus with 2–4 simple and 4–6 plumose setae. Dactylus with 5–7 plumose setae. Exopod two-segmented with 3–5 plumose setae on proximal segment and 4 long terminal plumose setae on distal segment. Epipod with 24–34 plumose setae. Arthrobranch rudimentary.

Chelipeds ( Fig. 1A, B View Figure 1 ) symmetrical, covered with simple and plumose setae. Presence of small red and brown dorsal spots on all chelipeds segments. Ischium with conspicuous dark pigmentation in ring format. Merus with prominent spine on anterolateral region. Carpus with distal spine on dorsolateral inner portion, near articulation with propodus. Pereopods 2–5 ( Fig. 1A, B View Figure 1 ) similar, with simple and plumose setae. Presence of small red and brown dorsal spots along pereopods. Ischium of all pereopods with conspicuous dark pigmentation in ring format.