Cherax snowden, Lukhaup, Christian, Panteleit, Joern & Schrimpf, Anne, 2015

Lukhaup, Christian, Panteleit, Joern & Schrimpf, Anne, 2015, Cheraxsnowden, a new species of crayfish (Crustacea, Decapoda, Parastacidae) from the Kepala Burung (Vogelkop) Peninsula in Irian Jaya (West Papua), Indonesia, ZooKeys 518, pp. 1-14 : 3-9

Taxon classification Animalia Decapoda Parastacidae

Cherax snowden sp. n. Figs 1, 2, 3, 4, 5

Type material.

Holotype: male (TL 96 mm) (MZB Cru 4291), Oinsok River Drainage, Sawiat District, Kepala Burung (Vogelkop) Peninsula, West Papua, Indonesia, collected by Irianto Wahid on 14 January 2015, exported through Aquazone Aquarium, Jakarta, Indonesia. Paratype: 1 male (TL 101 mm) (MZB Cru 4292), 1 allotype female (TL 77 mm) (MZB Cru 4293), same data as holotype.

Non-type material.

3 males (TL 69-84 mm) (MZB Cru 4294), same data as holotype.

Description of male holotype

(Figs 2-5). Body and eyes pigmented. Eyes not reduced.

Body subovate, slightly compressed laterally. Pleon narrower then cephalothorax (width 18 mm and 20 mm respectively). Rostrum (Fig. 3A) slender, reaching about to end of ultimate antennular peduncle and one third as long as wide (width 6 mm at base, length 9 mm). Upper surface smooth, pitted, few scattered setae present at tip of rostrum; lateral margins of rostrum almost straight in basal part, distally rather moderatly tapering towards apex. Margins slightly elevated continuing in rostral carinae on carapax. Lateral rostral margins bearing each 2 blunt spines in distal third, few short hairs present on base of rostral margins, punctaded at base. Rostral carinae extending as slight elevation posteriorly on carapace, fading shortly after beginning of postorbital ridges. Postorbital ridges well developed terminating in slightly upturned corneous spines anteriorly, fading posteriorly at two-thirds of occipital carapace length. Dorsal surface of carapace smooth, pitted, cervical and branchiocardiac grooves distinct, non-setose. Short setae present on caudal margin. Areola length 17 mm narrowest width 6 mm. Length of areola 36.95% of total length of carapace (46 mm).

Ventrolateral parts smooth with scattered pitts; anterior margin strongly produced, rounded upper margin directed inward. Dorsal surface of pleon smooth, with scattered pits; abdominal segments with short seate present on caudal margins.

Eyes rather large; cornea globular, darkly pigmented, about as long as eyestalk; eyestalk slightly narrower than cornea.

Antennulae and antennae typical for the genus. Antennae about as long as body. Antennular peduncle reaching slightly beyond acumen, antennal peduncle reaching slightly beyond apex of scaphocerite. Scaphocerite (Fig. 3B) broadest at midlength, convex in distal part becoming narrower in basal part; thickened lateral margin terminating in large corneous spine, almost reaching distal margin of ultimate segment of antennular peduncle. Right scaphocerite 8 mm long and 3,5 mm wide. Proximal margins setose. Coxicerite of antennal peduncle with spinuous tubercle anteriorly; basicerite with one lateral and one ventral spine and hooked tubercles.

Epistome broadly triangular becoming lance-shaped,with corneous spine at anterior tip, lateral surface with small tubercles; central surface smooth, excavate. Mouthparts typical for the genus.

First pereopods equal in form, chelae not gaping. subequal in size, left cheliped largest (48 mm long, 18 mm wide, 10 mm high), probably replaced. Right chelae (Fig. 3 C–D) 46 mm long, 20 mm wide, 11 mm high) strongly compressed. Fingers shorter than palm (dactylus 19 mm long). Dactylus broad at base, tapering slightly towards tip, becoming about 1/2 as broad as at base. Tip with sharp, corneous, hooked tooth pointing outwards at an angle of 45°. Cutting edge of dactyl with a continuous row of rather small granular teeth and one prominent larger tooth at about middle of cutting edge. Ventral and dorsal surface of movable finger with scattered punctuation. three rows of short setae present at posterior half of the cutting edge. Fixed finger triangular, merging gradually into palm, ending in sharp, corneous, hooked tooth, standing almost perpendicular to axis of finger. Upper surface of palm practically smooth, slightly pitted, more densely pitted at margins. Five rows of short setae present in posterior part. Mesial margin of palm with a row of 23-24 tubercles. Dorsal surface of carpus (14 mm) smooth and pitted, with slight excavation in middle part. Ventral carpal surface margins slightly elevated; inner margin with set of 6-7 small granules and one acute spiniform tubercle oriented in an angle of approx 45°.

Merus (23 mm) laterally depressed in basal part; surface smooth and pitted; row of 6-7 tubercles present and a prominent spine at anterior part. Dorsolateral margin with one corneous tubercle; row of small granules on entire inner ventrolateral margin with 3 prominent spines at the anterior part. Ischium (12 mm) smooth with single granule on ventral surface.

Second pereopod reaching about to apex of scaphocerite. Finger as long as palm, of same height. Short setae present on dactyl and fixed finger, getting more dense anteriorly. Cutting edge of fixed finger and carpus with row of short setae. Carpus slightly longer than palm. Merus (15 mm) about 1.7 times longer than carpus (9 mm). Ischium (7 mm) about half as long as merus.

Third pereopod overreaching second. Fingers shorter than palm.

Fourth pereopod reaching distal margin of scaphocerite. Dactylus with corneous tip. Short setae present. Propodus more than twice as long as dactylus, about 1.5 times as long as carpus; somewhat flattened, carrying stiff setae on lower margin. Merus just slightly longer than propodus.

Fifth pereopod similar to fourth, slightly shorter.

Dorsal surface of pleon smooth in median region; pleura smooth, slightly pitted, becoming densely pitted on sixth somite and telson. Telson with posterolateral spines, dense short setae present in the posterior third. Posterior margines setose. Uropodal protopod with distal spine on mesial lobe. Exopod of uropod with two well defined spines. One distal spine on mesial lobe, with prominent median rib ending in a spine in middle of uropod. Posterior margin of proximal segment of exopod of uropod with row of small spines overlapping diaresis. Short seata present on posterior third of dorsal surface of endopod and exopod.Ventral surface of telson, endopod and exopod smooth, not pitted. Margines of exopod setose.

Description of paratype female

(Fig. 6). Chela of first pereiopods equal, about 2 times as long as broad (24 mm and 11 mm respectively). Mesial margin of palm slightly elevated, forming slender serrated ridge with row of 13-14 small granular teeth. Cutting edge of dactyl with rather small granular teeth in posterior part and one slightly larger tooth in about middle. Cutting edge of fixed finger with small granules and one slightly larger granules. Small scattered short setae visible along ventral cutting edge of chelae, more dense in posterior area. Cervical groove distinct, non setose. Cephalothorax just slightly narrower than pleon (widths 14 mm and 16 mm respectively).

Size.

The males examined have a carapace length of 31-43 mm, and a total length of 69-101 mm (n = 5); the female has a carapace length of 34 mm and a total length of 77 mm (n = 1).

Colouration.

The living animals (Fig. 1 A–C) are coloured as follows. Chelae dark green to light green or greenish gray, distal part of the lower margin cream to orange. Tips of chelae orange.

Cephalothorax dark green, light green, brown green, sometimes blueish green fading ventrally to cream, beige or orange. Pleon same colour as cephalothorax with transverse orange bands, pleura creamy to orange with a black, brown or dark green band. Walking legs from dark green to blueish gray or creamy yellow, sometimes brown yellow. Distal margin of tail-fan cream to orange.

Systematic position.

Cherax snowden sp. n. differs from Cherax holthuisi in the shape of the rostrum, number of rostral teeth, the shape of the chelae and coloration. While Cherax holthuisi has just two indentations on each side in the distal part of the rostrum and no spines present, Cherax snowden sp. n. has 2 rostral teeth on each side near the apex. Cherax holthuisi usually is orange to pale, creamy or light brown, rarerly light blue, while the new species is dark green to light green or greenish gray. Tips of the chelae in the new species are striking orange. Eyes in Cherax holthuisi rather small compared to the eyes of Cherax snowden sp. n.

The phylogenetic tree revealed that Cherax snowden sp. n. forms a strong supported clade with an undescribed Cherax sp. individual that was collected in Sorong West Papua, Indonesia (GenBank accession number: KM501043). The two sequences in this clade differ by only 9 base pair substitutions (1.5%). The low genetic divergence of the undescribed Cherax sp. and the close geographic sampling origin indicate that this individual is the same species as the here new described species. The Cherax snowden sp. n. and Cherax sp. clade group next to the clade which includes Cherax sp. nov. A and Cherax holthuisi . The species of these two neighbouring clades differ by 9.2% ( Cherax sp. to Cherax sp. nov. A) to 9.7% ( Cherax snowden sp. n. to Cherax holthuisi ), respectively. The strong genetic divergence of Cherax snowden sp. n. to the next related described Cherax species indicates that Cherax snowden sp. n. is indeed a new species.

Holthuis (1949) in his publication on the New Guinea Cherax considered species should be placed into two groups. One with the rostral and median carine absent or weakly developed and refered to as the Cherax group following the characteristics of the type species, Cherax preissii (Erichson, 1846) from southwest Australia. The other group contains species that have rostral and sometimes the median carina well developed and refered to as the Astaconephrops group with Nobili’s (1899) Astaconephrops albertisii as the type. Newly described species have been placed into one or other of the two subgenera ( Lukhaup and Pekny 2006, 2008; Lukhaup and Herbert 2008; Lukhaup 2015; Patoka et al. 2015). Munasinghe et al. (2004b) and Austin (1996) and Austin and Knott (1996) however identified three geographically-based lineages within Cherax based on molecular phylogenetic studies: a southwestern group, an eastern group and a northern group. Support for the latter group however was based on only very limited sampling (e.g. single samples of Cherax quadricarinatus , Cherax rhynchotus Riek, 1951 and Cherax peknyi in Munasinghe et al.'s study) ( Munasinghe et al. 2004b) indicate that the division of Cherax into two subgenera, as conceived by Holthuis and subsequent authors dealing with New Guinea crayfish has to be reconsidered. Based on Munasinghe et al. (2004b) and Austin (1996) and Austin and Knott (1996) Cherax snowden sp. n. belongs to the northern species group lineage consisting of 21 species:

Cherax albertisii ; Cherax boesemani ; Cherax boschmai Holthuis, 1949; Cherax buitendijkae Holthuis, 1949; Cherax communis ; Cherax divergens Holthuis, 1950; Cherax gherardii Patoka, Bláha & Kouba, 2015; Cherax holthuisi ; Cherax longipes Holthuis, 1949; Cherax lorentzi lorentzi Roux, 1911; Cherax lorentzi aruanus Roux, 1911; Cherax minor Holthuis, 1996; Cherax misolicus Holthuis, 1949; Cherax monticola Holthuis, 1950; Cherax murido Holthuis, 1949; Cherax pallidus Holthuis, 1949; Cherax paniaicus Holthuis, 1949; Cherax papuanus Holthuis, 1949; Cherax peknyi ; Cherax pulcher Lukhaup, 2015; Cherax solus Holthuis, 1949.

Etymology.

The new species is named after the american freedom fighter Edward Joseph Snowden. He is honored due to of his extraordinary achievements in defense of justice, and freedom. The name is used as a noun in apposition.

Ecology.

Known only from tributary creeks to the Oinsok River, Sawiat District in the central part of the Kepala Burung (Vogelkop) Peninsula. The creeks from where these crayfish have been collected are shallow (20-60 cm) with a moderate flow, the water is clear, and has a pH of approx. 6.5. In most of the parts no water plants are present. The substrate of the creek is rocky, mostly covered with silt, stones and larger rocks..To improve the knowledge of the distribution of the species more collecting trips are necessary.

It is also necessary to briefly comment on the possible threats faced by the new species. As Cherax snowden sp. n. is collected in large numbers for the global aquarium trade, as well as for food for the growing local population, the crayfish population will invariably be adversely impacted. According to local collectors, the populations of the species have been decreasing in the last few years. Clearly, the continued collectiing of these crayfish for the trade is not a sustainable practice, and if the popularity of the species continues, a conservation management plan will have to be developed, potentially including a captive breeding program.