Euastacus mirangudjin, Coughran, 2002

Coughran, Jason, 2002, A New Species of the Freshwater Crayfish Genus Euastacus (Decapoda: Parastacidae) from Northeastern New South Wales, Australia, Records of the Australian Museum 54 (1), pp. 25-30 : 26-29

Euastacus mirangudjin n.sp.

Fig. 2– 4

Type material. HOLOTYPE: female (30 mm OCL); Iron Pot Creek , Toonumbar National Park, rainforest; 28°28'30"S 152°45'E; elevation 560 m; 6 September 2000; collected by Jason Coughran and Benjamin Black, lodged with the Australian Museum ( AM P61072) . PARATYPE: male (34.5 mm OCL), lodged with the Australian Museum ( AM P61073) .

Type locality. The type locality is in Iron Pot Creek , an upper tributary of the Richmond River , approximately 30 km NW of Kyogle (28°28'30"S 152°45'E). The site is approximately 500m upstream of the junction of Murray Scrub Management Trail and Iron Pot Creek . The site is in the rainforest of Toonumbar National Park , at an elevation of 560m. The stream where the specimens were collected was up to 10 metres in width and 1 metre in depth. Water temperature was 9°C and pH 6.65 (recorded at 3:00 PM on 6 September 2000) .

Other specimens examined. Two other specimens (26 mm OCL ♀; 37 mm OCL ♀) caught at the type locality were also examined before being released. Ratios used in the description are based on the retained specimens only.

Diagnosis. Male cuticle partition present. Rostrum short, just reaching base of third antennal segment. 3 rostral spines per side, extending beyond midlength of rostrum. Antennal squame without marginal spines. Suborbital spine small to medium. Dorsal thoracic spines absent/barely discernible. Cervical spines barely discernible or small. 1–5 small and sharp Li spines on somite 2, 1 barely discernible or absent on other somites. D spines and abdominal boss absent. Telsonic and uropodal marginal spines absent. 4–7 spines above the propodal cutting edges extending to base of chela gape, and 3–4 spines above the dactylar cutting edges. 3–

4 dorsal apical propodal spines. 1 apical mesial dactylar spine. Dactylar basal spines absent. Ventrolateral propodal spine row either absent or poorly developed into a single, blunt spine at midlength. Usually 3 mesial carpal spines. 1 poorly developed lateral carpal spine at distal edge of carpus (rarely two spines). Ventral carpal spine large. One ventromesial carpal spine.

Description. Maximum OCL 37 mm. Rostrum —short, just reaching base of third antennal segment, with a distinct and deep longitudinal groove; rostral margins parallel at sides and divergent at base; rostral carinae short; 3 marginal rostral spines per side, extending beyond midlength of rostrum (paratype with 2 spines on one side); acumen spine similar in size to marginal spines; OCL/carapace length = 0.88; rostral width/OCL = 0.14–0.17. Cephalon —weakly spinose; antennal squame marginal spines absent; 1st postorbital ridge spine small to medium, 2nd postorbital ridge spine barely discernible (ridge reduced to a subtle bump on carapace); numerous small to medium, blunt cephalic spines ventral to postorbital ridges; suborbital spine small to medium in size; interantennal scale of medium width and scalloped; basipodite spine absent or small; coxopodite spine small to medium and occasionally bifid; interantennal scale length/OCL = 0.09–0.1. Thorax —1–5 cervical spines per side, barely discernible or very small; thoracic spines absent or barely discernible; general tubercles dense and small; areola length/OCL = 0.35; areola width/OCL = 0.13–0.14; carapace width/OCL = 0.53–0.55; carapace depth/OCL = 0.47–0.54. Abdomen —1–5 Li spines

on somite 2, 1 barely discernible or absent on other somites; 2 Lii spines on somite 2 of large female specimen (released) (OCL 37 mm); D-L spines absent on most specimens, although present and minute on large female; D spines and abdominal boss absent; abdomen width/OCL = 0.5–0.52; OCL/total length = 0.42. Tailfan —telsonic and uropodal marginal spines absent; telson length/OCL = 0.33. Chelae —elongate. Dactylus —dactylar basal spines absent;

1 apical mesial dactylar spine; 3–4 medium to large and blunt spines above dactylar cutting edge, extending to midlength of chela gape (apical on paratype); dactylar length/propodal length = 0.55. Propodus —5 mesial propodal spines; ventrolateral propodal spines absent or poorly developed into a single blunt spine at midlength of propodus; dorsolateral propodal spines reaching apex but not base of propodus; 3–4 apical propodal spines; 4–7 small to large and blunt spines above propodal cutting edge, extending to base of chela gape; few to numerous protuberances lateral to dactylar base dorsally, two specimens also with 1 or 2 spines (on one chela only); usually 1 (rarely 2) spines lateral to dactylar base ventrally; 2 spines ventral to propodal cutting edge proximal to midlength; spines posterior to dactylar articulation absent; 2 spines at dactylar articulation both dorsally and ventrally; propodal length/OCL = 1.0–1.03; propodal width/propodal length = 0.42; propodal depth/propodal length = 0.27– 0.28. Carpus —dorsal groove deep; lateral carpal spination poorly developed into a single blunt spine at distal edge of carpus (one specimen with two discernible spines on one chela); usually 3 mesial carpal spines, paratype with 4 large and distinct spines on one chela and 2 large and 2 small (but distinct) spines on other chela ( Fig. 3 ); dorsal carpal spines absent; ventral carpal spine large; ventromesial carpal spine as large as, or larger than, ventral spine on specimens> 30 mm OCL, smaller than ventral spine on specimens 30 mm OCL and smaller; dorsal carpal groove present. Merus —7–8 small to large dorsal spines. Keel Pr.1, close and parallel; Pr.2, apart and parallel to slightly closed; Pr.3, apart and of narrow to moderate breadth, scoops absent; Pr.4, apart and very broad, anterior margin rounded, posterior margin convex. Setation —moderate.

Punctation —moderate on cephalon, denser on thorax.

Colouration —body dorsally red-brown to green-brown; ventrally orange, with orange colouration extending up onto lateral branchiostegites on larger animals; abdominal pleura blue, brown on one specimen; abdominal spines yellow; cervical and cephalic spines yellow, orange, or orange with yellow tips; carpus dark brown dorsally, ventrally orange tinged mesially with blue-brown; dorsal surface of propodus mottled green-brown; propodus ventrally orange, mesially brown. Mesial propodal spines blue; lateral propodal spine ridge blue to green-brown, with yellow or light brown spines; fingers dark brown with paler or yellow tips. Sexes —males possess a cuticle partition; a berried female was caught with an OCL of 37 mm; the eggs carried were bright red in colour; the holotype, a 30 mm OCL female, has proportionally similar abdomen width (relative to OCL) to the slightly larger male paratype, suggesting an immature sexual state (see Honan & Mitchell, 1995). Further biological research is required to better ascertain size at onset of sexual maturity. The species would appear to have a winter/spring breeding season, which has also been recorded for other Euastacus species ( Clark, 1937; Turvey & Merrick, 1997; Borsboom, 1998; Honan, 1998).

Biology. The species is known only from one site, in Iron Pot Creek. The specimens were caught during the dry season (in September), which appears to coincide with the breeding season.

Etymology. From the Bundjalung Aboriginal language “miran”, meaning belly or chest ( Holmer, 1971; Smythe, 1978) and gujihn [gudji:n, gudi:n], meaning ochre, red or orange ( Crowley, 1978; Smythe, 1978; Sharpe, 1985). The species could be colloquially referred to as the “ochrebellied crayfish” or “orange-bellied crayfish”. The specific epithet is used as a noun in apposition. The species is bright orange ventrally like E. gumar , although the orange colouration is more striking, remaining vivid as it extends ventrally over the walking legs, and extending well up onto the lateral branchiostegites of the carapace on larger specimens. The larger specimens in particular appear to glow orange from underneath.

Remarks. Euastacus mirangudjin is morphologically similar to E. reductus , from further south in the Port Macquarie region, and the species forming the setosus complex in southeastern Queensland ( E. jagara Morgan 1988 , E. maidae Riek 1956 , E. setosus Riek 1956 and E. urospinosus Riek 1956 ). Table 1 outlines morphological traits which can be used to distinguish E. mirangudjin from these species. The distinguishing spination of the chelae of E. mirangudjin is shown in Figure 4 .

Figures

Figure 2. Euastacus mirangudjin n.sp. Dorsal view, holotype. Photograph by Max Egan.

Figure 3. Euastacus mirangudjin n.sp. Dorsal view of chela (paratype) showing 4 mesial carpal spines. All other specimens examined bore 3 mesial carpal spines. Photograph by Max Egan.

Figure 4. Distinguishing features of the chela of Euastacus mirangudjin n.sp. Dorsal view (A, B) and ventral view (C, D) of chela of holotype (A, C) and paratype (B, D). ad, apical mesial dactylar spine (1 spine); ap, dorsal apical propodal spine row (3–4 spin es); dce, spine row above dactylar cutting edge (3–4 spines); ldb, bumps and protuberanceslateral to dactylar base; mc, mesial carpal sp ines (usually 3, paratype with 4); mp, mesial propodal spines (5); pce, spine row above propodal cutting edge (4–7 spines, extending to base of chela gape); v, ventral carpal spine (large); vm, ventromesal carpal spine (1 spine, smaller than or as large as ventral carpal spine). Photographs by Max Egan.