Chaceon affinis (A. Milne-Edwards & Bouvier, 1894)

Landeria, José M. & Tamura, Hiroaki, 2018, Morphology of the first zoea of Chaceon affinis (A. Milne-Edwards & Bouvier, 1894) and occurrence of Chaceon spp. larvae (Decapoda: Brachyura: Gerynonidae) in the Canary Islands waters, Northeastern Atlantic, Zootaxa 4413 (3), pp. 579-585 : 581

Chaceon affinis (A. Milne-Edwards & Bouvier, 1894)

( Fig. 1 )

Description of zoea I. Carapace ( Fig. 1a, b ): Well developed dorsal, rostral, and lateral spines; dorsal spine slightly curved distally; rostral spine longer than antenna and shorter than dorsal spine. A pair of simple setae on posterior base of dorsal spine. Latero-ventral carapace margin with small protuberances, lacking setae. Eyes sessile.

Antennule ( Fig. 1c ): Unsegmented, with 3 terminal aesthetes (2 long thick + 1 shorter thin), and 2 terminal, simple setae (1 long + 1 short). Endopod absent.

Antenna ( Fig. 1d ): Protopodal process longer than exopod with two distal rows of spinous denticules along its 2/3–3/4 length. Exopod with one slender, subterminal seta with small setula on the middle part, and one process lacking ornamentation. Endopod absent.

Mandible: Palp absent, incisor and molar processes well developed.

Maxillule ( Fig. 1e ): Coxal endite with 8 sparsely, plumodenticulate setae (1 sublateral + 2 subterminal + 5 marginal). Basial endite with 3 cuspidate + 3 subterminal, sparsely, plumodenticulate setae, and covered with microtrichia on the proximally. Endopod 2-segmented; the proximal segment with one long, sparsely, plumodenticulate seta, and the distal segment with 2+4 subterminal, sparsely, plumodenticulate setae. Exopodal setae absent.

Maxilla ( Fig. 1f ): Coxal endite bilobed with 3+4 sparsely, plumodenticulate setae. Basial endite bilobed with 5+5 sparsely, plumodenticulate setae. Endopod unsegmented and bilobed with 3+5 sparsely, plumodenticulate setae. Scaphognathite with 7 plumose setae (sometimes 5 or 6), and 1 plumose, stout process. Each endite lobe covered with microtrichia.

Maxilliped I ( Fig. 1g ): Coxa with 1 long, sparsely, plumodenticulate seta. Basis with 10 plumodenticulate setae (arranged 2+2+3+3). Endopod 5-segmented with 2, 2, 1, 2, 1+4 setae. Exopod 2-segmented, with 4 natatory, plumose setae on the distal segment.

Maxilliped II ( Fig. 1h ): Coxa without seta. Basis with 4 plumodenticulate setae (arranged 1+1+1+1). Endopod 3-segmented, with 1, 1, 5 setae. Exopod 2-segmented, 4 terminal, natatory, plumose setae on the distal segment.

Maxilliped III and pereiopods: Represented as unsegmented buds. Sometimes absent.

Pleon ( Fig. 1i , i’): 5-segmented, somites 2–5 with a pair of setae on the postero-dorsal margin. A pair of dorsolateral processes on the somites 2 (outward and anteriorly curved), 3 (smaller posteriorly curved), and 4 (as a minute protuberance, sometimes absent). Postero-lateral processes decreasing in size from somites 3 to 5.

Pleopods: Absent.

Telson ( Fig. 1i , i’): Long furca, slightly curved dorsally. The tip of each furca curved inward. Each furca with 2 lateral spines (1 long, and 1 small) and 1 dorsal spine. Inner margin of telson with 3 pairs of serrate setae; the innermost pair with long setules in the middle section.

Figures

FIGURE1. Chaceonaffinis. ZoeaI. a, carapacefrontalview; b, carapace ventral margin; c,antennule;d, antenna; e, maxillule; f, maxilla; g, maxilliped I; h, maxilliped II; i, dorsal and i’ lateral view of pleon and telson. Scale bars: a = 0.5 mm; b–f = 0.2 mm.