Acanthaxius polyacantha Miyake and Sakai, 1967

Ngoc-Ho, Nguyen, 2006, Three species of Acanthaxius Sakai & de Saint Laurent, 1989, including two new to science, from the Solomon Islands and New Caledonia (Crustacea, Thalassinidea, Axiidae), Zootaxa 1240, pp. 57-68 : 66-68

Acanthaxius polyacantha Miyake and Sakai, 1967

( Fig. 4 )

Acanthaxius polyacantha Miyake and Sakai, 1967: 303 , fig. 1.

Material examined

Solomon Islands, Alis, Salomon 1, St. 1761, 191– 290 m, Ph. Bouchet, B. Dayrat/A. Warren, B. Richer de Forges coll., 27 Sept 2001: 1 female, cl. 9 mm, tl. 24.5 mm (figured) ( MNHN Th 1498).

Description

Carapace ( Fig 4 A) with triangular pointed rostrum slightly shorter than eyestalks, lateral border with two spines and a suborbital spine. Median carina of gastric region extending to cervical groove, with four spines anterior to faint tubercle, six spines posterior to it; lateral carina with large anterior spine and seven smaller posteriorly; two submedian carinae, each with six or seven spines; lateral sides of carapace and postcervical region bearing numerous spinules. Telson ( Fig. 4 B) slightly longer than broad with four dorsal spines, lateral border with two spinules, two posterolateral spines and median spine on convex posterior border.

Antennal peduncle ( Fig. 4 A) longer than that of antennule, article 1, 3 and 4 with one, one and two lower spines respectively as figured for the type (Miyake & Sakai, 1967: fig. 1C), acicle slender nearly reaching the distal border of article 4. Maxilliped 3 with lower spine on coxa and basis, two lower spines on ischium, four on merus and one lower distal spinule on carpus.

Pereopods 1 subequal, larger ( Fig. 4 C) with dactylus about 1.3 times length of propodal palm; smaller pereopod 1 with more slender dactylus nearly 1.8 times as long as palm; similar spinulation for both appendages: ischium with two lower spines; merus with three upper distal spines, eight lower spines, several spines and spinules on anterior lateral surface; carpus with two or three upper spines and two lower spines, propodus with spinules on lateral surface, four upper spines and row of 11–12 lower submarginal spines; cutting edge of fixed finger, as well as dactylus, with small acute teeth, latter with curved tip and seven or eight large upper spines. Pereopod 2, 3 and 4 each with three lower spines on merus, one of them distal. Uropod exopod ( Fig.4 B) ovoid, bearing seven spines on lateral external border and large distal spine near suture, external carina with four spinules; endopod with four spines on lateral external border and four spines on median carina.

Remarks

The holotype and only known specimen of the species is an ovigerous female from the East China Sea (27°16’N, 125°34.5’E) (off East Taiwan), measuring 15 mm in carapace length and 51 mm in total length. The present specimen from the Solomon Islands is smaller but agrees with the type (Miyake & Sakai, 1967) in the morphology of the rostrum and carapace, the pereopods, the telson and uropods. Some minor differences are found, i.e. fewer upper spines on the merus of both pereopds 1, four dorsal spines on the telson (instead of six in the type) which are probably related to its smaller size and younger age.

Figures

FIGURE 4. Acanthaxius polyacantha Miyake and Sakai, female (MNHN Th 1498). A, anterior part of carapace; B, telson and uropods; C, large pereopod 1. Scale line: 1 mm.