Cherax rayko, Lukhaup & Eprilurahman & von Rintelen, 2024

Lukhaup, Christian, Eprilurahman, Rury & von Rintelen, Thomas, 2024, Two New Species of Crayfish of the Genus Cherax (Crustacea, Decapoda, Parastacidae) from Western and Eastern Indonesian New Guinea, Arthropoda 2 (4), pp. 264-293 : 267-279

Cherax rayko n. sp.

Figures 1–5 .

Material examined. Holotype: male ( MZB Cru 5792 ), under rocks and among roots and in debris along banks of unnamed creek of the Bian River drainage basin in the Muting District, South Papua, Indonesia. Coll. local people. January 2015. Crayfish were sent to us by KKCrayfish Farm in Jakarta. Allotype: female ( MZB Cru 5793 ), same data as holotype. Paratypes: 5 males and 4 females ( MZB Cru 5794 ); 4 males and 2 females ( ZMB 33408 ); same data as holotype .

Diagnosis. Carapace surface smooth; one small spine and two granules posterior to cervical groove on lateral carapace present. Eyes large, pigmented. Cornea as broad as eyestalk. Rostrum triangular in shape with elevated, thickened margins, non-setose. Rostral margins with two prominent teeth. Rostral carinae prominent. Postorbital ridges prominent with one acute spine at anterior terminus. Propodal cutting edge with short setae in posterior part and one large tubercle. Chelipeds white and blueish, sometimes blue. Other walking legs blue-gray. Carapace usually blue and orange to yellow; pleon with orange-yellowish lateral stripes on a dark green or blackish background.

Description of male holotype ( Figures 1A,B , 2 , 3 , and 4A,B). Body and eyes pigmented. Eyes not reduced. Body subovate, slightly compressed laterally. Pleon narrower than cephalothorax (width 23.3 mm and 26.2 mm, respectively). Rostrum ( Figure 4A ) broad in shape, reaching the end of ultimate antennular peduncle and about 2.5 times as long as wide (width 6.9 mm at base, length 15.7 mm). Margins slightly elevated continuing in rostral carinae on carapace, almost straight in basal part, distal third, pointing upwards at angle of approximately 45 ◦. Acumen with anteriorly orientated spine. A few scattered hairs present on anterior third of rostrum.

Rostral carinae extending as slight elevations posteriorly on carapace terminating at half of postorbital ridges. Postorbital ridges well developed, terminating in spiniform tubercle anteriorly, fading at half of occipital carapace length, posteriorly. Postorbital ridges about 2/3 of CL. Cervical and branchiocardiac grooves distinct, non-setose; 1 small spine and 2–3 granules present at middle part behind cervical groove on lateral sides of carapace. Carapace (57.9 mm) surface smooth; anterior margin strongly produced; rounded upper margin directed inward.

Areola smooth; length, 19.5 mm; narrowest width, 8.1 mm. Length of areola 33.6% of total length of carapace (57.9 mm).

Scaphocerite ( Figure 4B ), broadest at posterior third, convex in distal part becoming narrower in basal part; thickened lateral margin terminating in corneous spine, slightly overreaching ultimate segment of antennular peduncle. Left scaphocerite 12.4 mm long and 4.1 mm wide. Proximal margins setose. Antennulae and antennae typical for genus. Antennae slightly longer than body. Antennular peduncle reaching acumen; antennal peduncle slightly overreaching apex of scaphocerite. Antennal protopodite smooth, without spine, with row of hairs on inner margin; basicerite with one lateral and one ventral spine.

Mouthparts typical for genus. Epistome with subcordiform cephalic lobe anteriorly bearing lanceolate cephalomedian projection constricted at base. Lateral margins of lobe not thickened; each lateral margin with a group of very small tubercles separated by a smooth region. Central part smooth, not pitted, excavate. Eyes rather large; cornea globular, darkly pigmented, nearly as long as eyestalk; eyestalk slightly narrower than cornea.

First pereopods ( Figure 3A,B ) equal in form, chela, gaping. Right cheliped 63.0 mm long, 13.5 mm high, and 24.0 mm wide. Left chelae 63.2 mm long and 13.8 mm high, 23.8 mm wide, strongly compressed. Fingers shorter than palm (right dactylus 29.9 mm long). Dactylus broad at base (10.2 mm), tapering slightly towards tip.

Tip with sharp, corneous, hooked tooth pointing outwards at an angle of 10 ◦. Cutting edge of dactyl with continuous row of small granular teeth posteriorly and one prominent larger tooth at middle of cutting edge. Ventral and dorsal surface of movable finger smooth with scattered punctuation. Ventral posterior half of cutting edge with dense setae reaching from base to prominent larger tooth. Fixed finger smooth, scattered punctuation, triangular, merging gradually into palm, ending in sharp, corneous, hooked tooth, parallel to x -axis of finger. Tips of fingers slightly cross when fingers clasp. Upper surface of palm practically smooth, slightly pitted, more densely pitted at margins. Fixed finger slightly broader than dactyl at base (11.3 mm). Dense, short setae present in posterior ventral part of fixed finger, reaching from palm to about half of cutting edge. Cutting edge of fixed finger with row of rather small granular teeth at posterior half and one prominent larger one at first third. Outer lateral margin of chelae smooth. Row of 23–24 mesial probodal granules at dorsolateral margin. Dorsolateral margins elevated.

Dorsal surface of carpus (17.1 mm) smooth, with slight excavation in middle part and with a well-developed mesial carpal spine. Ventral carpal surface margins slightly elevated, non-setose, and with fovea; inner margin with well-developed ventral carpal spine and a prominent ventromesial carpal spine oriented at an angle of approx. 45 ◦.

Merus (25.5 mm) laterally depressed in basal part; surface smooth; small dorsal meral spine present. Inner ventrolateral margin densely covered with small granules; three ventral meral spines present, one at mid-length, other in middle of anterior part, and third on distal ventrolateral inner margin.

Ischium (16.1 mm) smooth with two small spines at ventrolateral inner margin.

Second pereopods reaching anteriorly to approximately mid-length of scaphocerite. Propodus (13.7 mm) and dactylus (6.9 mm) slightly longer than fixed finger (6.5 mm), of same height. A few scattered short setae present on dactyl and fixed finger. Cutting edge of dactyl and propodus with row of dense, short setae. Carpus (10.7 mm), smooth, slightly pitted. Merus (28.3 mm); ischium (8.5 mm) about one-third as long as merus.

Third pereopods overreaching second pereopods by length of finger of second pereopods. Fingers shorter than palm.

Fourth pereopods reaching distal margin of scaphocerite. Dactylus (5.2 mm) with corneous tip. Short, scattered setae present. Propodus (11.1 mm) more than twice as long as dactylus, somewhat flattened, carrying many stiff setae on lower margin. Merus (14.7 mm) slightly longer than propodus.

Fifth pereopods similar to fourth, slightly shorter.

Dorsal surface of pleon smooth, with scattered pits; abdominal segments (1–5) with short setae present on caudal margins of segment. Pleon length 65.9 mm.

Telson with posterolateral spines; dense short setae present in posterior third. Posterior margins setose. Uropodal protopod with two distal spines on mesial lobe. Exopod of uropod with transverse row of posteriorly directed diminutive spines ending in one more prominent spine, posteriorly directed on outer margin of mesial lobe. Terminal half of exopod with small spines and short hairs, slightly corrugated. Endopod of uropod smooth. Short, scattered hairs present on posterior third of dorsal exopod. Posterolateral spine on outer margin present. Second spine on medial dorsal surface present, directed posteriorly.

Description of female allotype ( Figure 5 ). Chela of first pereopods equal, 2.4 times as long as broad (33.7 mm and 13.7 mm, respectively). Mesial margin of palm slightly elevated, forming slender serrated ridge with row of 15–16 small granular teeth. Cutting edge of dactylus with 10–11 rather small granular teeth. Cutting edge of fixed finger with 11–12 small granules. Small scattered short setae visible along ventral cutting edges of chelae, denser and longer in ventral posterior area. Tips of fingers slightly cross when fingers clasp, not gaping. Rostrum broad in shape, reaching the end of ultimate antennular peduncle. Margins slightly elevated continuing in rostral carinae on carapace, almost straight in basal part, distal third, pointing upwards at angle of approximately 45 ◦. Acumen with anteriorly orientated spine. A few scattered hairs present on anterior third of rostrum. Cervical groove distinct, non-setose; three small granules present. Cephalothorax just slightly wider than pleon (widths 17.7 mm and 18.0 mm, respectively). Same color pattern as in males. Size 90 mm.

Size. The biggest male examined is the holotype, and it has a carapace length of 57.9 mm and a total length of 123.8 mm. The other males have a total length of between 82.1 mm and 122.9 mm; the allotype has a carapace length of 56.6 mm and a total length of 90.0 mm. The other females have a total length of between 96.4 mm and 79.2 mm (n = 11).

Color. The living animals ( Figure 1A–C ) are colored as follows. Individuals of Cherax rayko sp.nov. usually have white to creamy and sometimes blueish-white chelae; the cephalon is blueish fading to creamy-white ventrolaterally. Rostral margins are usually orange. The thorax is usually orange to yellow, fading to a creamy-yellow ventrolaterally. Chelae are creamy with blue becoming blueish-gray to the outer lateral margin. In some individuals, the chelae can be bright blue or grayish-blue. The pleon is usually dark green or blackish-green with broad orange to yellowish stripes. Females: same color as males, sometimes less intense with smaller chelae.

Molecular phylogenetic results. Cherax rayko n. sp. forms a highly supported, distinct clade that is the sister species to C. alyciae with moderate support; both species are in turn sister to C. peknyi ( Figure 6 ). The clade comprising these three species is highly supported and very distinct; its next relatives are C. communis and C. panaicus (which are sister groups with high support) and C. monticola and C. misolicus . The relationship of these four species to the clade containing Cherax rayko n. sp. is unresolved. Cherax rayko n. sp. is well isolated from C. alyciae and C. peknyi with a sequence divergence (p -distance, 16S) of 1.3–1.5% and 2.4–2.9%, respectively, supporting the morphology-based description of C. rayko as a new species. Cherax rayko n. sp. is genetically and morphologically most similar to C. alyciae Lukhaup et al., 2018 [ 1], endemic to creeks in the Digul River drainage basin in the eastern part of the Boven Digoel Regency, Papua, Indonesia, and to Cherax peknyi from the Fly River drainage basin, in the Western Province of Papua New Guinea.

Systematic position. Holthuis [ 1] in his publication on the New Guinea Cherax considered that the species should be placed into two groups, one with the rostral and median carinae absent or weakly developed and referred to as the Cherax group following the characteristics of the type species, C. preissii (Erichson, 1846) [ 31] from southwest Australia, and the other group containing species that have the rostral and sometimes the median carina well developed and referred to as the Astaconephrops group with Nobili’s (1899) [ 32] Astaconephrops albertisii as the type. Newly described species have been placed into one or the other of the two subgenera [ 6, 7, 9, 11, 14]. Munasinghe et al. [ 33, 34], Austin [ 35], and Austin and Knott [ 36], however, identified three lineages with different geographic ranges within Cherax based on molecular genetics and phylogenetic studies. These consist of a southwestern group, an eastern group, and a northern group. While support for the latter group, however, was based on only very limited sampling (e.g., single samples of C. quadricarinatus , C. rhynchotus , and C. peknyi in the Munasinghe et al. study [ 23]), a later study by Blaha et al. [ 20] confirmed these results based on a more extensive dataset. These findings suggest that the division of Cherax into two subgenera, as conceived by Holthuis and subsequent authors dealing with New Guinea crayfish, has to be reconsidered, as pointed out by Crandall and De Grave [ 37]. Based on these studies [ 20, 23, 32, 33], Cherax rayko n. sp. clearly belongs to the northern species group lineage, now consisting of 28 species.

3. Systematic Remarks

In comparison to all species of the northern group, the new species, C. rayko n. sp., is most similar to C. peknyi and C. alyciae . Cherax rayko n. sp. may be easily distinguished from both species by using sequence divergence, by the coloration and pattern of live individuals, by the shape of the chelae, and by the shape of the rostrum.

Cherax rayko n. sp. differs from C. peknyi in the following characters: the size, shape of the chelae, shape of the body, and coloration. Catchers also presented some other color forms that are genetically and morphologically very close to Cherax rayko n. sp., claiming they are from the Wanggo, Bian, and Kumbe Rivers in the Merauke Regency.

Size comparison. In C. rayko n. sp., the biggest males reach up to 130 mm (n = 300); the biggest male in C. peknyi is the holotype with 92 mm (n = 120), while the biggest males in C. alyciae reach 123 mm (n = 124).

Coloration comparison. C. rayko n. sp., C. peknyi , and C. alyciae ( Figure 7 ). Individuals of Cherax rayko n. sp. from the Bian River drainage basin in the Muting District usually have white to creamy and sometimes blueish-white chelae; the cephalon is blueish fading to creamy-white ventrolaterally. The rostral margins are usually orange. The thorax is usually orange to yellow, fading to a creamy-yellow ventrolaterally. The chelae are creamy with blue, becoming blueish-gray to the outer lateral margin. In some individuals the chelae can be bright blue or grayish-blue. The pleon is usually dark green or blackish-green with broad orange to yellowish stripes.

The coloration of C. peknyi is as follows. The chelae are red to orange, fading to pinkish-white anteriorly; the distal tip is blueish-gray. The legs (except for first pair) are greenish-gray with orange joints. The cephalic region is greenish-gray, fading to a yellowish-green laterally; the dorsal thoracic region is brown-orange, fading to yellow laterally and becoming cream ventrolaterally. The pleon is green with broad yellow bands. The telson is green, becoming yellow to orange mesolaterally. The distal margin of the tail fan is pale orange.

In C. alyciae , the chelae are light to dark blue with white margins and a white patch. The anterior part is usually dark blue, more intensely colored. The corneous tooth on the tip of the fingers is orange. The cephalothorax is bright blue, dorsally more intense from purple to greenish-blue, fading ventrally to light blue. The joints between the propodus and carpus and between the carpus and merus are bright orange-red. Segments of the pleon are dark blue to black; the lateral pleura is lighter, becoming blueish-green. There are light blue transverse bands in the posterior part of each pleonary somite. The walking legs are light blue with orange joints. The distal margin of the tail fan is creamy-orange to orange. Some animals are darker and differ in the coloration of the chelae. The chelae are dark blue to black, becoming orange-red at the outer lateral margin. The dorsolateral margins are light blue. These males usually also have orange or yellow rostral margins.

Chelae comparison ( Figure 8A–F ). In C. rayko n. sp., the movable finger is usually as long as the dorsolateral margin of the palm. No soft patch is present on the outer margin. In total, 23–24 mesial probodal granules are present at the dorsolateral margin. Dense, short setae are present on the ventral part of the fixed finger and palm. In C. alyciae , the movable finger is about one-third shorter than the dorsolateral margin of the palm. A soft patch at the outer margin of the palm is present in males. The dorsolateral margins of the palm are just slightly elevated, with a row of 12–15 rather weakly developed granules present. Scattered, short setae are present on the ventral part of the fixed finger and palm. In C. peknyi , the carpus with the mesiolateral part is slightly elevated to form a slender serrated ridge with row of 16–18 small, blunt spines. The movable finger is about one-third longer than the dorsolateral margin of the palm. Dense, long setae are present on the ventral part of the fixed finger and palm.

Rostrum comparison ( Figure 9A–C ). The rostrum of C. rayko n. sp. is broad at the base, and at about one-third of the length, it bends inwards. The rostrum of C. alyciae is rather straight and triangular-shaped, while the rostrum of C. peknyi is clearly bent outwards at the middle part.

C. rayko n. sp. has 4–5 small granules at the middle part behind the cervical groove on the lateral side of the carapace, while C. peknyi has 3–4 anteriorly directed spines present, and C. alyciae has six tiny and weakly developed tubercles there.

Cherax rayko n. sp. is found in the Bian River drainage basin in the Muting District in South Papua, Indonesia, while C. peknyi is known to be present in the Fly River floodplain and in the foothills of the mountains near the provincial capital of Kiunga, Western Province, Papua New Guinea. C. alyciae is found in creeks and rivers of the Digul River drainage basin in the eastern part of the Boven Digoel Regency, Papua, Indonesia ( Figure 10 ).

Etymology. Cherax rayko n. sp. is named after Rayko Eloy Lukhaup, the son of the first author. Rayko was very present in the process of the description, providing love and understanding.

Ecology. It is endemic to the Bian River drainage basin and its tributaries. One of the creeks harboring these crayfish is shallow (20–100 cm) with a moderate flow. The temperature is around 25–26 ◦ C. In most parts, no water plants are present. The substrate of the creek is silt or sand and soil mostly covered with silt and detritus. Crayfish hide in short burrows in the riverbank, under larger rocks, or in detritus that is present in all the parts of the creek. The creek is surrounded by forest. To improve the knowledge of the distribution of this species, more field surveys will be necessary.

Common name. As the common name for this crayfish, we propose the Tiger Crayfish, as it is already available under this name in the pet trade.

Figures

Figure 1. Cherax rayko n. sp. (A) Holotype male (MZB Cru 5792), Bian River drainage basin in the Muting District, West Papua, Indonesia. (B) Idem, side view. (C) Female, same data as holotype.

Figure 2. Cherax rayko n. sp., holotype male (MZB Cru 5792). Scale bar: 10 mm.

Figure 3. Right chela of Cherax rayko n. sp., holotype male (MZB Cru 5792). (A) Dorsal view. (B) Ventral view. Scale bar: 10 mm.

Figure 4. Cherax rayko n. sp., holotype male (MZB Cru 5792). (A) Dorsal view of cephalothorax. Scale bar: 10 mm. (B) Scaphocerite. Scale bar: 10 mm.

Figure 5. Cherax rayko n. sp., allotype female (MZB Cru 5793). Scale bar: 10 mm.

Figure 6. Phylogenetic relationships of C. phing n. sp. and C. rayko n. sp. within the northern New Guinea Cherax lineage, reconstructed by BI analyses of the 16S rRNA mitochondrial gene fragment. Numbers on branches show, from top, Bayesian posterior probabilities (>0.7) and ML/MP bootstrap values (>50). An asterisk indicates nodes with full support (1/100/100) in all analyses. The scale bar indicates the substitution rate. See Table 1 for information on the sequenced specimens.

Figure 7. Coloration comparison of Cherax rayko n. sp. with C. peknyi and C. alyciae. (A) Cherax rayko n. sp. from Muting. (B) C. peknyi from the type locality close to Kiunga, PNG. (C,D) C. alyciae from Boven Digoel Regency, West Papua, Indonesia.

Figure 8. Chelae comparison of C. rayko n. sp. (A,F) with C. peknyi (C,D) and C. alyciae (B,E).

Figure 9. Rostrum comparison of C. rayko n. sp. (A) with C. peknyi (C) and C. alyciae (B).

Figure 10. New Guinea with the distribution of C. rayko sp.nov, C. alyciae, and C. peknyi.