Eocyzicus parooensis, Richter & Timms, 2005

Richter, Stefan & Timms, Brian V., 2005, A List of the Recent Clam Shrimps (Crustacea: Laevicaudata, Spinicaudata, Cyclestherida) of Australia, Including a Description of a New Species of Eocyzicus, Records of the Australian Museum 57 (3), pp. 341-354 : 343

Eocyzicus parooensis n.sp.

Figs. 1–3

Eocyzicus sp. a, Timms & Richter, 2002.

Limnadia sp. b, Timms, 1993.

Type material. HOLOTYPE 3, formalin-fixed AM P68156, carapace 7.8 × 4.5 mm . PARATYPES formalin-fixed: 13 slide AM P68157 , 1♀ slide AM P68158 ; 833, 9♀♀, AM P68159 , all collected by B. V. Timms from Gidgee Lake, 17 November 1999 .

Type locality. Gidgee Lake on Bells Creek , Bloodwood Station, 130 km NW of Bourke, NSW, Australia, 29°33'S 144°52'E .

Etymology. This species is named after the Paroo area where it occurs commonly in hyposaline waters.

Description. Male carapace 7.2 to 7.8 mm length, 4.2 to 4.5 mm height (n = 10). Female carapace 6.4 to 6.7 mm length, 3.9. to 4.1 mm height, smallest and largest female both ovigerous (n = 10). Carapace in both sexes oval, with 10 to 11 growth lines in males, and 9 to 10 in females. Dorsal margin of carapace with prominent umbo, posterior of umbo straight. Male head region with prominent rectangular (hatchet-like) rostrum in lateral view ( Fig. 2A), including bilateral anterior margins, a ventral margin and a posterior margin. Anterior margins together form a V-shape in the dorsal view, continuing into the fornices of both sides ( Fig. 2B). Nauplius eye triangular shaped, with sharp end pointing to the compound eye. Central dorsal part of the head defined anteriorly by prominent compound eye chamber and posteriorly by rounded occipital condylus. Compound eye chamber opening via a small pore anteriorly, slightly above anterior margins of rostrum ( Fig. 2A, arrowhead). Central head region filled by mid-gut diverticula. Dorsal organ located close to posterior margin of occipital condyle ( Fig. 2B, arrowhead). Female head region differing in particular by shape of rostrum which is more triangular because of less distinct posterior margin ( Fig. 3A ). Antennule extending to about fourth (females) or sixth (males) segment of posterior antennal flagellum, and distinctly lobate with each lobe bearing short sensilla ( Fig. 2C). Antenna with peduncle of about eight segments, anterior densely covered with setae ( Fig. 3C ), and with about 11 to 14 segments on both anterior and posterior flagellum. Each flagellum segment bearing about six short spines on anterior side, and a number of longer natatory setae at the posterior side. Trunk consisting of 22 (in a few cases 23) leg-bearing segments, the last (two) segments not entirely separated from telson ( Figs. 2G, 3B ). More posterior trunk segments (between 10 and 15) carrying single dorsal spine at posterior end of segment ( Fig. 2F). First and second thoracopod of male modified as claspers, not differing general characters from each other. Movable finger smoothly curving to the apical club (i.e. expanded apex). Surface of movable finger adjacent to apical club covered with scales; apical club with stout flat-tipped spines opposite to scales of movable finger ( Fig. 2D). Tip of movable finger with about six (specimen studied might be broken in this area) more elongated “hairy” scales, directed away from apical club ( Fig. 2E). Two palps originating from palm, the larger (threesegmented) palp behind movable finger, smaller (onesegmented) palp at apical club base. In females, eggs carried by projections of exopod of the ninth and tenth pairs of thoracopods ( Fig. 3D ). Telson covered dorsally by numerous spines, with caudal furcae originating at its posterior end. Dorsal part of telson formed like a “U”, with connecting part anteriorly and the two parallel margins ending in strong, upwards curved apexes ( Fig. 2G,H,K). Margins carrying about 10 to 13 spines each in males and about 15 to 20 in females, excluding the apex ( Figs. 2G, 3B ). Two telsonal setae originating from a common plate at anterior end, at inner side of “U” ( Fig. 2K). Caudal furcae articulated with telson; each carrying many (about 15) long plumose setae on inner margin ( Fig. 2G,K). Tips of caudal furcae covered by very small spinules ( Fig. 2 I). Eggs round and smooth, not showing any specialized surface structures ( Fig. 3D ).

Remarks. This species has been recorded from several other localities in the Paroo area ( Timms & Richter, 2002). Some of the characters differ from those described herein, e.g., the number of growth lines, number of telson spines, and the carapace length and height. Nevertheless, we believe that all these records (referred to in Timms & Richter, 2002 as Eocyzicus sp. a) are of E. parooensis n.sp. Most remarkable from an ecological point of view is that all these records are from hyposaline water bodies (see Timms & Richter, 2002 for more details). There is probably a second undescribed Eocyzicus species common in the Paroo area, which prefers turbid fresh water habitats (referred to Eocyzicus sp. b by Timms & Richter, 2002).

Figures

Fig. 1. Eocyzicus parooensis n.sp. (A) holotype (AM P68156) thoracopods, except the first two pairs (claspers), not drawn. (B–E) Paratype male (AM P68157): (B) head, left antennae removed; (C) first left clasper; (D) second left clasper; (E) telson. (F–G) Paratype female (AM P68158); (F) head, left antenna removed; (G) telson. Scales: 1 mm (A,B), 0.2 mm (C), 0.5 mm (D–G).

Fig. 3. Eocyzicus parooensis n.sp. SEM images of female characters: (A) head, left antenna reduced; (B) telson; (C) antenna base; (D) cysts. Scales: 200 µm (A, B), 100 µm (D), 40 µm (C).