Cherax acherontis Patoka, Bláha and Kouba, 2017

Patoka, Jiří, Bláha, Martin & Kouba, Antonín, 2017, Cherax acherontis (Decapoda: Parastacidae), the first cave crayfish from the Southern Hemisphere (Papua Province, Indonesia), Zootaxa 4363 (1), pp. 137-144 : 138-142

Cherax acherontis Patoka, Bláha and Kouba , n. sp.

Figs 1–3 , 6

Diagnosis. Carapace surface smooth except for numerous small, blunt, indistinct, tubercles posterior and ventrolateral to the cervical groove. Eyes small, reduced, and pigmented with eyestalk prominently broader than cornea. Rostrum lanceolate in shape, setose with lateral margins elevated. Rostral length/width ratio range 2.0–3.5. Rostral margins with 2–4 prominent teeth. Rostral carinae developed. Postorbital ridges prominent with one very short acute tubercle at anterior terminus. Median carina present but very indistinct. Very broad semicircular scaphocerite broadest at midlength with a single distinct spine at terminus of apex. Antennular peduncle more or less reaching behind acumen, antennal peduncle reaching behind apex of scaphocerite. Antennae longer than body. Lateral margins of epistome separated by narrow row of small tubercles. Third maxillipeds long and covered by dense long setae. Areola length/width ratio range 2.2–3.7. Uncalcified patch on lateral margin of chelae of adult male absents. Chelae length/width ratio range 2.3–5.3, width/depth ratio range 1.3–2.5. Cutting edge of dactyl with row of very small granules, while cutting edge of opposite propodus with one prominent tubercle. Fingers slightly gaping, in distal part with hooked tips, cutting edges setose. Entire inner lateral margin of palm covered with two or three rows of numerous bluntly topped teeth with short setose hairs. Outer margin of palm with small teeth near its basal part. Colouration of body and appendages mostly ochre and body surface slightly marbled. Gonopores of both sexes normal in shape and position. Terminal half of caudal fan soft and membranous.

Description of holotypic male. ( Fig 1–3 ). Eyes pigmented and reduced. Body subovate, slightly compressed laterally, pigment reduced. Cephalothorax 1.1 times broader than pleon. Rostrum ( Fig. 3A, B ) 2.2 times as long as wide, reaching beyond the end of second segment of antennular peduncle. Upper rostral surface smooth and setose. Acumen with anteriorly oriented spine at terminus. Median carina present but only slightly prominent on the cephalon, on the rostrum absents. Lateral rostral margins elevated, anteriorly convergent throughout length to acumen, posteriorly continuing in prominent carinae ending indistinctly behind the level of postorbital ridge spines. Lateral rostral margins bearing three pairs of teeth distally, distal part and upper surface of rostrum covered with dense setose hairs. Postorbital ridges ( Fig. 3A, B ) prominent, strongly elevated, posteriorly fading and in the last third of the cephalon indistinct. Anterior terminus of postorbital ridges with slightly upturned short spiniform tubercle. Eyes ( Fig. 3A ) very small; cornea globular, darkly pigmented, eyestalk prominently broader than cornea. Antennulae and antennae normal in shape. Antennae longer than body. Antennular peduncle reaching behind acumen, antennal peduncle reaching behind apex of scaphocerite. Coxicerite of antennal peduncle with blunt tubercle anteriorly. Scaphocerite ( Fig. 3F ) flat and horizontal, broad semicircular in shape, narrower in basal part, with lamina 1.8 times as long as broad, broadest at midlength; not reaching behind antennular peduncle; short prominent acute spiniform tubercle at apex reaching distinctly beyond the lamina; rounded inner margin strongly covered by setae. Third maxillipeds reaching 0.7 of CTL, covered by dense and long setae ( Fig. 3G ); epistome ( Fig. 3E ) with subcordiform cephalis lobe anteriorly bearing rounded cephalomedian projection constricted at base; each side covered with two groups of small tubercles separated by a smooth area; central part smooth with fovea, not pitted; lateral margins separated by narrow row of small tubercles; posterior margin of cephalomedian projection with short setose hairs, not pitted; epistomal zygoma prominent and thick, moderately arched with oblique arms.

Dorsal surface of carapace smooth, with exception of numerous small blunt and indistinct tubercles posterior and ventrolateral cervical groove. Areola three times as long as wide at the narrowest part. Length of areola 39% of TCL; surface smooth, slightly pitted, formed by two parts in first third. Cervical groove distinct, non-setose.

Chelipeds and chelae ( Figs. 3C, D ) equal in form and size; 4.3 times as long as broad and 6.7 times as long as deep; chela surface smooth, pitted; fingers 1.3 times longer than palm; chela equally long as carapace; fingers slightly gaping; slightly convex dactyl tapering to the tip; cutting edge setose with five rather small granular teeth over the full length, one larger tooth at basal third. Fixed finger narrow and 1.4 times broader than dactyl at base; cutting edge setose with 7 to 11 rather small granular teeth in two rows. Tips of fingers with acute, hooked spines slightly crossing when fingers clasp. Entire inner lateral margin of palm covered with two or three rows of numerous bluntly topped teeth with short setose hairs. Outer margin of palm with eight small teeth near its basal part. Carpus smooth and pitted; with one well-developed acute and hooked spiniform tubercle in the middle of dorsolateral inner margin (mentioned tubercle is characteristic for genus Cherax ) and numerous smaller tubercles; terminated with one spiniform tubercle oriented anteriorly. Ventral carpal surface non-setose, with fovea. Merus strongly laterally depressed in basal part; surface smooth and pitted; one prominent anteriorly oriented tooth and row of small anteriorly oriented tubercles (serrate carina) present on dorsal surface; one prominent anteriorly oriented tooth and row of small tubercles present on ventral surface; two prominent anteriorly oriented teeth and row of small tubercles on entire inner ventrolateral margin. Second pereiopod reaching behind apex of scaphocerite. Palm equally long as fingers; fingers and palm sparsely setose; tip of dactylus hooked; cutting edges of both fingers densely setose. Carpus 1.4 times longer than palm. Merus 1.6 times longer than carpus and 2.3 times longer than ischium. Third pereiopod 1.3 times longer than second pereiopod, palm 1.2 times longer than fingers; fingers and palm sparsely setose; tip of dactylus hooked; cutting edges of both fingers densely setose. Carpus 1.1 times longer than palm. Merus 1.6 times longer than carpus and 2.6 times longer than ischium. Fourth pereiopod reaching behind the end of antennal peduncle. Propodus and dactyl strongly setose. Dactyl slightly hooked and densely setose on cutting edge. Propodus 1.4 times longer than carpus. Merus 2.2 times longer than carpus and 2.4 times longer than ischium. Fifth pereiopod reaching midlength of scaphocerite. Propodus and dactyl strongly setose. Dactyl slightly hooked and densely setose on cutting edge. Propodus 1.7 times longer than carpus. Merus 2.1 times longer than carpus and 2.6 times longer than ischium.

Dorsal surface of pleon smooth in median region and sparsely setose; pleura smooth, pitted. Each pleomere strongly setose with short hairs on ventral posterior margin. Telson with two posteriorly directed spiniform tubercles in caudolateral corners. Protopod of uropod with single posteriorly directed spiniform tubercle on distal margin. Endopod of uropod with two posteriorly directed spiniform tubercles in the middle and outer margin of mesial lobe. Exopod of uropods with transverse row of posteriorly directed diminutive spiniform tubercles ending in posteriorly directed spiniform tubercles on outer margin of mesial lobe. Terminal half of caudal fan soft, membranous, setose on the posterior margin.

Description of allotypic female. ( Fig 4 ). Differing from the holotype in the following respects: the chelae 5.0 times as long as broad and 8.3 times as long as deep; carapace 1.4 times longer than chela. Pleon equally broad as cephalothorax; areola 2.2 times long as wide at the narrowest part.

Remarks. The single, well-developed, acute and hooked spiniform tubercle in the middle of the dorsolateral inner carpus margin is characteristic of Cherax . Right cheliped of holotype was autotomized during the transport. The allotype was without any visible damages.

Size. Holotype: ♂, TL = 128 mm, TCL = 62 mm, PCL = 48 mm, RW = 5 mm, RL = 14 mm, AW = 8 mm, AL = 24 mm, ChW = 14 mm, ChL = 60 mm, ChD = 9 mm. Allotype: ♀, TL = 81 mm, TCL = 36 mm, PCL = 27 mm, RW = 4 mm, RL = 9 mm, AW = 6 mm, AL = 13 mm, ChW = 5 mm, ChL = 25 mm, ChD = 3 mm. Paratypes: ♂ (n = 23), TL = 50–140 mm (x̄= 78 mm, SD = 21.6 mm), TCL = 24–66 mm (x̄= 36 mm, SD = 10.2 mm), PCL = 18–52 mm (x̄= 28 mm, SD = 8.3 mm), RW = 2–6 mm (x̄= 3 mm, SD = 0.9 mm), RL = 6–14 mm (x̄= 8 mm, SD = 3.0 mm), AW = 3–8 mm (x̄= 5 mm, SD = 1.3 mm), AL = 9–27 mm (x̄= 14 mm, SD = 4.3 mm), ChW = 3–19 mm (x̄= 7 mm, SD = 3.7 mm), ChL = 16–58 mm (x̄= 28 mm, SD = 12.0 mm), ChD = 2–11 mm (x̄= 4 mm, SD = 2.2 mm); ♀ (n = 7), TL = 63–105 mm (x̄= 78 mm, SD = 21.6 mm), TCL = 29–49 mm (x̄= 36 mm, SD = 10.2 mm), PCL = 22–38 mm (x̄= 28 mm, SD = 8.3 mm), RW = 3–5 mm (x̄= 3 mm, SD = 1.0 mm), RL = 7–11 mm (x̄= 8 mm, SD = 3.0 mm), AW = 4–6 mm (x̄= 5 mm, SD = 1.3 mm), AL = 11–19 mm (x̄= 14 mm, SD = 4.3 mm), ChW = 4–7 mm (x̄= 5.75 mm, SD = 1.1 mm), ChL = 20–25 mm (x̄= 23 mm, SD = 1.9 mm), ChD = 3–4 mm (x̄= 3.5 mm, SD = 0.5 mm).

Colouration of live specimens. Colouration of body and appendages mostly ochre, rarely pink or blueish. Body surface slightly marbled, legs paler than body. Ventral side of palm of chelae coloured as dorsal side. Fingers and joints of the dactyls rarely blueish.

Deposition of types. Holotype ( MZB Cru 4678) , allotype ( MZB Cru 4679) and seven paratypes ( MZB Cru 4680) deposited in The Zoological Museum of Bogor (Museum Zoologicum Bogoriense, Indonesia) ; 10 paratypes ( RMNH. CRUS.D.57252 until RMNH. CRUS.D.57261) are deposited in Naturalis Biodiversity Center, Leiden, the Netherlands ; 13 paratypes (Y2017JP/01 until Y2017JP/13) deposited in the Collection of Aquatic Crustaceans at the Department of Zoology and Fisheries, Czech University of Life Sciences Prague, Czech Republic .

Systematic position. In regard to energy economy, low food availability and due to the lack of photostimuli, the troglobitic crayfish are characterised by morphological traits such as long and slender claws, reduced eyes, loss of body pigmentation, and long antennae. We found these characteristics also in C. acherontis . A special feeding adaptation is known in one of the North American crayfish, Troglocambarus maclanei , which has long and thickened third maxillipeds provided with dense and usually filtrating setae ( Hobbs et al. 1977). The same characteristic was found in C. acherontis . It is obvious that the environmental pressures created by cave habitats influenced the convergent evolution of such species despite their phylogenetic and zoogeographical origin and divergence of epigean congeners.

There are various characteristics such as shape of scaphocerite and absence of soft uncalcified patch on outer margin of adult male claws which class the new species to subgenus Cherax ; nevertheless, there are some other characteristics such as shape of rostrum, presence of prominent rostral teeth and well developed rostral and postorbital carinae which class the new species to the subgenus Astaconephrops . In accordance to a recent phylogenetic study ( Bláha et al. 2016), the validity of the subgenera suggested by Holthuis (1950) is controversial and therefore we do not use any subgenus to describe the new species.

In comparison to all New-Guinean species from the genus Cherax , the new species is most similar to C. monticola and differs from this species in the following characters: body and chelae colouration of live individuals, length and width of rostrum, lateral carapace surface behind the cervical groove, longer and narrower chelae, absence of soft uncalcified margin of chela in adult males, and the longer third maxilliped and second pereiopod. Rostrum reaches the end of antennular peduncle in C. monticola while this peduncle more or less terminates behind the acumen in the new species. Rostrum of adult individuals 1.8 to 1.9 times as long as broad at base in C. monticola while it is 2.25 to 2.8 in the new species. Third maxillipeds covered by longer setae and 1.2 times longer in C. acherontis than in C. monticola . Numerous rather widely separated tubercles are present on the lateral carapace behind the cervical groove in C. monticola while the carapace is smooth in the new species. Row of small blunt tubercles posteriorly cervical groove laterally in C. monticola while ventrolaterally in the new species. Chela of adult males 2.3 to 2.7 times as long as broad in C. monticola while 2.3 to 5.3 times in the new species. The fingers are longer in the new species. One or two decalcified spots present on the outer margin of chela of adult males and sometimes also females of C. monticola while always absent in the new species. Base of outer margin of chela without tubercles in C. monticola while small teeth are present in the new species. The legs of second pair reach to the end of the scaphocerite in C. monticola while reaching behind the end of the scaphocerite in the new species.

Although we conducted a preliminary study of the phylogenetic position of the new species, the results were ambiguous and require further analysis. Nevertheless, the results showed a close relationship with C. monticola .

Etymology. The specific name corresponds to the Latin genitive singular of Acherōn, one of the mystic rivers in the underworld in ancient Greek mythology.

Common name. Since the crayfish were captured in the submerged river Yumugima, we propose the name Yumugima Crayfish as a common name for the new species, Cherax acherontis n. sp.

Distribution. The karst cave with rich dripstone decoration is located in the New Guinea Highlands, Jayawijaya Regency, Papua Province, GPS coordinates: S 04°01.933’ E 139°00.221’ ( Fig 5 , 6 ). There are three entrances to the cave, Hagepma and two others are both named Jugurama. Close to the Hagepma entrance is situated Palimoro village inhabited by one family of local Dani people. The cave was formed by the submerged Yumugima river. The river flows out from the mountains in Baliem Valley as a tributary of Baliem river. There are both fast flowing shallow riffles (depth about 0.5 m) and pools (deeper than 1 m), water temperature was 15.0 °C and pH 7–8. Based on information from local people, the water level increases up to two meters during the rainy season. On the bottom of the river, there are large and small boulders, rock, clay, sand deposits, and sporadically wood debris ( Fig 6B ) inhabited with a few benthic invertebrates such as mayfly larvae and oligochaetes. No crayfish burrows were recorded. Since there was some garbage observed, such as plastic bags, we assumed that the river flows on the surface somewhere upstream, but local Dani people have no information in this regard.

Figures

FIGURE 1. Cherax acherontis n. sp., holotypic male, side view.

FIGURE 2. Cherax acherontis n. sp., holotypic male, dorsal view. Scale bar: 20 mm.

FIGURE 3. Cherax acherontis n. sp., from holotype. A, lateral view of carapace; B, dorsal view of carapace; C, ventral view of right chela; D, dorsal view of right chela; E, epistome; F, dorsal view of right scaphocerite;G, third maxilliped.

FIGURE 4. Cherax acherontis n. sp., allotypicfemale, dorsal view.

FIGURE 5. Map of Papua Province, Indonesia. The position of the cave near city of Wamena indicated by red triangle. The photo shows a typical terrain inthe vicinity of the cave.

FIGURE 6. A, Hagepma entrance into the cave; B, wood debris in the river in the cave; C, dripstone decoration in the cave.