Euastacus morgani sp. n., a new spiny crayfish (Crustacea, Decapoda, Parastacidae) from the highland rainforests of eastern New South Wales, Australia

Abstract Euastacus morgani sp. n., is described from a highland, rainforest site in Bindarri National Park, in eastern New South Wales, Australia. Euastacus morgani is found living sympatrically with two more common species, Euastacus dangadi Morgan, 1997 and Euastacus neohirsutus Riek, 1956. Systematically, the species belongs in the ‘simplex’ complex of the genus that includes Euastacus simplex Riek, 1956, Euastacus clarkae Morgan, 1997, Euastacus maccai McCormack and Coughran 2008 and E. morgani. This new species differs from its nearest congenor, Euastacus simplex, in having three mesial carpal spines. A key to the ‘simplex’ complex is presented.


Introduction
Th e Australian spiny crayfi sh genus Euastacus Clark, 1936 is the most species-rich of all genera in the family Parastacidae, the southern hemisphere freshwater crayfi shes. Clark (1936) erected the genus based on the type species Cancer serratus Shaw, 1794, a junior homonym later corrected to Astacoides spinifer Heller, 1865 (see Morgan 1986). Although Clark (1936) initially recognized six species, subsequent work would clarify that there were seven species contained within the material at that time, each of which had been recognized by a diff erent authority at varying times over the preceding century. Clark (1941) also revised the genus, in the process describing two new species. Notable taxonomic contributions were later made by Riek (1951Riek ( , 1956Riek ( , 1969, who described 14 of the currently recognized species, and shortly thereafter a single species was described from far north Queensland by Monroe (1977). More recently, a revision of the genus was undertaken by Morgan (1983Morgan ( , 1986Morgan ( , 1988Morgan ( , 1989Morgan ( , 1997, whose comprehensive works resulted in the description of 17 new species, and was followed by a dramatic increase in research on the taxonomy, biology and ecology of the genus. Since then, eight additional species have been discovered and described, all from restricted highland areas of eastern and northern Australia (Short and Davie 1993;Coughran 2002Coughran , 2005Coughran and Leckie 2007;McCormack and Coughran 2008).
In this paper, we describe a further new species from a highland, rainforest site in central eastern Australia. In 2003, a single specimen of this new species of Euastacus was discovered during a fi eld survey in Bindarri National Park near Lowanna, New South Wales. Although photographs were taken, the specimen itself was subsequently lost. After many attempts to obtain further specimens from the original site and in the surrounding area, survey eff orts fi nally yielded new specimens in 2008. We now present a formal description for E. morgani sp. n.

Methods
Morphological terminology, character descriptions, size references and ratios follow those described by Morgan (1986). Orbital or ocular carapace length (OCL) is the standard index measurement for this genus, and extends obliquely from the eye socket to the dorsal posterior of the carapace (Morgan 1986 Diagnosis. Male cuticle partition present. Rostrum with 3 or 4 small marginal spines per side, extending to midlength. Suborbital spine of medium size. Th orax with 10-20 very small to small thoracic spines per side. Abdominal somites with tiny to small, moderately sharp to sharp Li and Lii spines. D-L and D abdominal spines present on somites 2-3 of some large specimens. Apical propodal spines absent. Ventral lateral propodal spine row moderately developed, usually with 4-5 centrally located spines. Spines above propodal cutting edge absent. Dactylus with 1 apical mesial spine and 1 dorsal mesial basal spine. Marginal dactylar basal spines absent. Dactylar fi nger with 1 or 2 tiny apical spines above cutting edge. Carpus with 3 mesial and 2 lateral spines. Ventromesial carpal spines smaller than ventral carpal spine. Setation light. Size. Th e maximum size of specimens collected was 39.9 mm OCL. Description. Rostrum. Rostrum short, usually reaching base of third antennal segment (occasionally not quite reaching base, and rarely extending as far as midlength of segment). Rostral sides slightly convergent to convergent, rostral bases divergent. Rostrum with 3 or 4 small marginal spines, extending to approximately rostral midlength, Cephalon. Numerous bumps and protrusions in cephalic region, with 1 (occasionally 2) on each side developed into more prominent, but small and blunt cephalic spine. First post-orbital ridge spine distinct but small. Second post-orbital ridge spine barely discernible to small; posterior to spine each ridge poorly developed initially, with large and swollen bump at posterior end. Suborbital spine medium in size, and acute.
Antenna. Basipodite spines small to medium. Coxopodite without distinct spines but with large, rounded development of coxopodal plate at mesial end. Interantennal spine of medium width and usually with slightly scalloped margins. Antennal squame lacking marginal spines, with near triangular infl ation at midlength. Scale Length/ OCL: 0.09-0.12.
Th orax. Th orax with 1-3 barely discernible to small cervical spines on each side, fl attened and triangular in shape with moderate to sharp point. Dorsal thoracic spines present and numbering 10-20 on each side. Dorsal thoracic spines very small to small but distinct, and larger than general tubercles; spines highlighted against the carapace by profi le (raised, but blunt) and/or colour (yellow-brown, grey-brown, grey or blue-grey). General tubercles small to medium in size (very small on specimens <25 mm OCL), and of moderate density. Areola Length/OCL: Abdomen. Abdominal somite 1 lacking spines. Somite 2 with 3-5 tiny to small, moderately sharp to sharp Li spines. Somites 3-6 with 1 Li spine, decreasing in size posteriorly to be barely discernible on somite 6 (absent on some specimens <25 mm OCL). Frequently 1 or 2 small Lii spines on somites 3-6 of specimens > 20 mm OCL. Propodus. Dorsal lateral propodal spine row extending from apex to base of propodus. Ventral lateral propodal spine row less developed, with 1-6 (usually 4 or 5) more or less centrally located spines. Numerous bumps and protrusions lateral to dactylar base dorsally, of which 1 or 2 are usually distinctly larger. Bumps and protrusions also present on ventral surface of propodus lateral to dactylar base, often including 1-4 more prominently developed spines extending along propodal fi nger. Propodus with 5-7 mesial spines. Dorsal apical propodal spines absent. Two blunt spines at dactylar articulation. Propodal surface posterior to dactylar articulation lacking spines, with 2 or 3 distinctly deep punctuations. Pre-carpal area lacking spines, with occasional distinct punctuations. Spines above propodal cutting edge absent on both dorsal and ventral surfaces (2 barely discernible apical spines on dorsal surface of one specimen ACP1099). Prominent tooth near dactylar articulation. Propodus Length/OCL: 0.81-0.90 (male), 0.80-0.94 (female). Propodus Width/PropL:0.46-0.50. Propodus Depth/Propodus Length: 0.26-0.31.
Carpus. Carpus with 3 mesial spines, decreasing in size posteriorly; generally produced to sharp point. Lateral margin of carpus with 2 spines. Ventral surface of carpus with large, sharp ventral spine and 1 or 2 tiny to medium, blunt ventromesial spines. Dorsal surface with deep groove; bearing 1-3 large, bluish-green, blunt bumps or spines (occasionally merging to eff ectively form raised ridge or boss) on dorsal surface mesial to groove.
Merus. Merus with 6 or 7 small to medium dorsal spines, and a barely discernible or small distolateral spine.
Th ird Maxilliped. Laterodistal corner of ischium produced to a distinct point. Exopodite shorter than or about as long as ischium (average 0.93 × ischium length).
Gastric Mill. Gastric mills were carefully extracted and examined for three specimens ranging in size from 29.94 to 39.87 mm OCL. Zygocardiac ossicle with 1.0-1.5 teeth anterior to ossicle ear (TAA), and 4.0-4.5 teeth anterior to posterior margin of ear (TAP), with tooth spread of 2.5-3.0. Urocardiac ossicle with 6 or 7 ridges.
Setation and Punctation. Setae sparse and short. Sparse to moderate and fi ne punctation on body. Chelae with occasional deep punctuations.
Colouration. Dorsally brown or green-brown with pale cream cephalic and cervical spines. Th oracic spines usually distinct from thorax background, and varying in colour (cream, grey, grey-brown or blue-grey). Abdominal somites marked heavily with blue laterally, with cream Li spines. First chelae mesially blue, with cream-tipped mesial propodal spines. Dorsal carpal bumps blue (often forming a raised, blue ridge). Walking legs blue-grey. Lateral propodal spines cream. Ventrally, a varying wash of pale blue-green, pink and orange, with a dull grey abdomen and tailfan. Merus of fi rst cheliped and antennal bases vivid orange.
Sexes. Males with cuticle partition. Female specimens without fully mature gonopores. All female specimens have calcifi ed gonopores that lack marginal setation. Gonopores of four largest female specimens (29.9-39.9 mm OCL) with slightly incised rims, those of largest specimen appear to be in state of decalcifi cation, being partially membranous on mesial margins. Th us, it would seem that female maturity occurs close to 40 mm OCL.

Discussion
Euastacus morgani sp. n. is known only from the type locality, a highland (~600 m a.s.l.), rainforest site at the northern margin of Bindarri National Park, in a tributary to the Little Nymboida River (Figure 3). Two comparatively widespread species of Euastacus occur in the area, including a site in Little Nymboida River proximal to the type locality, E. dangadi Morgan, 1997 andE. neohirsutus Riek, 1956. We have surveyed numerous sites in the area, but our eff orts yielded only these two more common species.
Th e species constructs a more or less horizontal burrow entrance from the water's edge back into the stream banks. Th e specimens were collected by probing these bank burrow systems by hand until the crayfi sh attempted to exit via another entrance hole, typically located 1-2 m further back from the creek on the adjacent forest fl oor. Th e successful sampling was undertaken at night.
Although the precise locality is uncertain, Gary Morgan collected juvenile Euastacus specimens at a nearby site ('Brimbin Creek', near Lowanna) that were too small for taxonomic determination, although they appeared to be diff erent to all local species (Morgan 1983). Morgan (1983) collected these specimens in sympatry with E. neohirsutus, and observed diff erences to that species on the following taxonomic features: larger rostral carinae; larger antennal basipodite spine; better developed ventral lateral propodal spine row of the cheliped; lacking dorsal apical propodal spines; lacking spines above the cutting edge of the propodus. All of these characters are also true of E. morgani, and thus it is likely that the small specimens observed by Gary Morgan were juveniles of this new species.
Euastacus morgani appears most similar in morphology to E. simplex Riek, 1956. It can be distinguished among other characters by having: 3 instead of 2 mesial carpal spines on the cheliped; no spines above the propodal cutting edge of the cheliped; medium instead of barely discernible or small suborbital spines; poor development of the ventral lateral propodal spine row; a proportionally shorter interantennal scale; and a proportionally shorter exopodite and more pointed anterior terminus to the ischium of the third maxilliped. Systematically, the species thus fi ts within the 'simplex' complex (Morgan 1997), which includes E. simplex, E. clarkae Morgan, 1997, E. maccai Mc-Cormack andCoughran, 2008, andE. morgani. A key is provided below to distinguish Euastacus morgani from other species in the 'simplex' complex.
Th e description of E. morgani increases the number of described species in this charismatic genus to 50 (Table 1). Th ere are further taxa still awaiting formal description, and large areas of potentially suitable habitat that have yet to be surveyed. Unfortunately, 80% of Euastacus are considered to be threatened Furse and Coughran in press a, b, c;IUCN 2010), and there is thus a sense of urgency for continued fi eld surveys and taxonomic work on this genus. It would appear that E. morgani has a severely restricted, highland distribution, and may be susceptible to similar threats facing other species in the genus, particularly those relating to overcollection, exotic species and climate change (Furse and Coughran in press a, b, c). Further research into its ecology is warranted.