Boasaxius princeps ( Boas, 1880 )

Marin, Ivan, 2015, Complete morphological re-description of mud-dwelling axiid Leonardsaxius amurensis (Kobjakova, 1937) with remarks on Axiidae (Crustacea: Decapoda: Axiidea) from the Russian coast of the Sea of Japan, Zootaxa 3937 (3), pp. 549-563 : 557-558

Boasaxius princeps ( Boas, 1880)

( Figures 6 , 7 , 8 a–e)

Axius princeps Boas, 1880: 98 , pl. 7 figs. 214-217; Balss, 1914: 88.

Axiopsis princeps . — Borradaile, 1903: 538; Makarov, 1938: 48, fig. 15; Vinogradov, 1950: 223;. Axiopsis (Axiopsis) princeps .—de Man, 1925: 6 (list), 69 (key); Miyake, 1982: 90, pl. 30, fig. 4. Allaxius princeps .— Sakai & de Saint Laurent, 1989: 74.

Boasaxius princeps .— Sakai, 2011: 76

Brief description. Body strong sclerotized segments, covered with tufts of plumose setae. Rostrum ( Fig. 6 a, b) well developed, reaching to the distal margin of second antennular segment, triangular and upturned anteriorly, bearing smooth median carina dorsally and 2–3 teeth on each of lateral margins extend onto gastric region. Gastric region bearing deep inverted U-shape surrounded by smooth lateral carinae extending posteriorly to near cervical groove ( Fig. 6 b). Median and dorsal carinae feebly marked, consists of rounded denticles, reaching almost to cervical groove. Basal antennal segment with sharp distodorsal and smaller distoventral teeth, scaphocerite hornshaped. Third maxilliped with meral segment armed with 3 horn-like teeth along lateral margin. Telson ( Fig. 6 c) about 1.5 times longer than wide, proximal lobe with spine followed by 1–2 spines on lateral margin, with several stout spines along lateral margin, with sharp apex, dorsal surface with ridges and several spines. First pereiopods (chelipeds) unequal, deeply covered with plumose setae; distal segments covered with numerous denticles, especially in major chela ( Fig. 6 d), palm of major cheliped with strong distodorsal tooth, palm of minor cheliped ( Fig. 6 e) with 4–5 strong curved teeth along dorsal margin, ventral margin in both chelipeds unarmed, fingers unarmed along dorsal margins, more stout in major cheliped, with stout rounded teeth in major cheliped and sharp triangular teeth in minor, especially along cutting margin of fixed finger (polex). Second pereiopod chelate, fingers about as long as palm. Third pereiopod with rectangular propodus armed with transverse rows of spines on ventrolateral surface, dactylus paddle-shaped, with row of spines on lateral surface. First pleopod in male uniramous, unsegmented, and sinuate, terminating in narrow distal protrusion; second pleopod in male biramous, endopod with appendix interna and appendix masculina. Uropodal endopod with distinct spines laterally, bearing median carina with spines dorsally. Uropodal exopod armed with sharp teeth laterally and distinct, movable spine at posterolateral angle, bearing transverse suture with spinules (or spiniform setae), and distal flap with distinct spine; with median carina with spines on dorsal surface.

Measurements. Large crustaceans. TL reaching to 200 mm, CL up to 70-80 mm

Coloration. Coloration change during life. Small immature animals ( Fig. 7 c–e) generally reddish or violet, with whitish ventral part of body and appendages, sometimes with wide dorsal light band on along carapace and abdomen, large animals became uniformly red or bricky red. Large mature animals ( Fig. 7 a, b) generally uniformly red. Orbits white. Antenna red or violet. Distal segments of chelipeds white, with white teeth and tips of fingers. Setae on body and especially chelipeds grey or sandy-grey.

Habitats. The species is found living inside deep burrows made in sand, rocky, gravel or shelly limestone substrates, under large stones or at the base of boulders or rocks; rarely observed on muddy bottom. Usually, burrows of Boasaxius princeps it can be recognized by long blue-red colored antenna and chelipeds of the species sticking out of the burrow; it can be found crawling on a bottom during the night time (pers. observ.).

Distribution. Sea of Japan: Russia: the Peter the Great Bay from Vostok to Posjet Bays, 5–30 meters, possibly deeper ( Vinogradov, 1950; the present paper); Japan: Hokkaido: off Yoichi (Sakai & de Saint Laurent, 1989), Honsu: Oga Peninsula ( Miyake, 1982); Niigata Prefecture, Sado Island ( Honma & Kitami, 1995); South Korea: Ulreung and Dokdo Islands ( Kim et al, 1993; Hong et al, 2006). Pacific: Japan, Honsu: Okirai, Ohfunato-city, Iwate Prefecture ( Sakai, 2011), Sagami Bay (Sakai & de Saint Laurent, 1989).

Taxonomic position. Originally described as Axius princeps Boas, 1880 the species was included in Axiopsis Borradaile, 1903 by Borradaile (1903) and Allaxius Sakai & de Saint Laurent, 1989 by Sakai & de Saint Laurent (1989). Sakai (2011) mentioned that the species “ does not belong in Allaxius either , because Axius princeps is clearly different from the type species of Allaxius , A. aethiopicus (Nobili, 1904) by the presence of male Plp1, which are conspicuously sinuate in shape, whereas in Allaxius aethiopicus it is absent ” and suggested the new genus — Boasaxius Sakai, 2011 ( Sakai, 2011); the genus is presently monotypic.

Figures

FIGURE 6. Boasaxius princeps (Boas, 1880), male (LEMMI), general lateral view.

FIGURE 7. Boasaxius princeps (Boas, 1880), male (LEMMI): a — front of carapace, lateral view; b — front of carapace, dorsal view; c — sixth pleomere, telson and uropods, dorsal view; d — major first pereiopod (cheliped); e — minor first pereiopod (cheliped).

FIGURE 8. Alive coloration of Boasaxius princeps (Boas, 1880) (a – e) and Leonardsaxius amurensis (Kobjakova, 1937) (f, g).