Cherax nigli n. sp.

Figures 29–34.

Material examined. Holotype: male (MZB Cru), under rocks, wood, and among roots and in debris along banks of an unnamed river in the southeast of the Kaimana Regency, West Papua, Indonesia. Coll. local people, December 2024. Crayfish were sent to us by KKCrayfish Farm in Jakarta. Allotype: female (MZB Cru), same data as holotype. Paratypes: one male (MZB Cru); two males and one female (ZMB 34714); same data as holotype.

Diagnosis. Carapace surface smooth with numerous small tubercles posterior to cervical groove on lateral carapace. Eyes large, pigmented. Cornea slightly broader than eyestalk. Rostrum lanceolate in shape with excavated margins. Rostral margins with two prominent teeth. Rostral carinae prominent. Postorbital ridges prominent with one acute tubercle at anterior terminus. Prominent uncalcified patch on lateral margin of chelae of adult male white, translucent. Propodal cutting edge with row of small granules and two slightly larger tubercle. Chelipeds blue and white with white joints and a red spot right posterior to the joints. Fingers with hooked tips. Other walking legs creamy white with some reddish and blueish spots. Pleon dark blue with light blue and creamy transverse bands. Lateral pleura becoming creamy.

Description of male holotype (Figures 29–31). Body and eyes pigmented (Figure 29). Eyes not reduced, darkly pigmented. Cornea slightly broader than eyestalk, as long as its eyestalk. Body subovate, slightly compressed laterally. Pleon narrower than cephalothorax (width 26.3 mm and 29.3 mm, respectively). Rostrum (Figure 31C) broad in shape, reaching middle of first antennular peduncle and about 1.5 times as long as wide (width 8.9 mm at base, length 13.5 mm). Margins slightly elevated, continuing in rostral carinae on carapace, almost straight in basal part. Acumen with anteriorly orientated spine. Rostral margins with two spines on each side on anterior third of rostrum. Few scattered hairs present on anterior third of rostrum. Rostrum surface with numerous tiny granules. 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. Surface between rostral carinae heavily pitted. Postorbital ridges about 1/4 of CL. Cervical and branchiocardiac grooves distinct, not setose; 4–5 small granules present at middle part behind cervical groove on lateral sides of carapace. Carapace (59.4 mm) surface smooth; numerous granules posterior to cervical groove on lateral carapace present. Anterior margin strongly produced; rounded upper margin directed inward. Areola smooth, pitted, small granules present in the posterior quarter of the areola; length, 18.4 mm; narrowest width, 9.4 mm. Length of areola 31.0% of total length of carapace (59.4 mm). Scaphocerite, 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 14.1 mm long and 6 mm wide. Proximal margins setose. Antennulae and antennae typical for genus. Antennae slightly longer than body. 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 3–4 very small tubercles separated by a smooth region. Central part smooth, not pitted, excavate. First pereopods (Figure 31A,B) equal in form, chela slightly gaping. Left cheliped 59.6 mm long, 12.6 mm high, and 26.5 mm wide. Right chelae 59.1 mm long and 11.8 mm high, 25.2 mm wide, strongly compressed. Fingers shorter than palm (left dactylus 25.1 mm long). Dactylus broad at base (4.4 mm), tapering slightly toward tip. Tip with sharp, corneous, hooked tooth pointing outwards at an angle of 45 ◦. Cutting edge of dactyl with continuous row of small granular teeth posteriorly and one slightly larger granule. Ventral and dorsal surface of movable finger smooth with scattered punctuation. Ventral posterior third of cutting edge with scattered setae reaching from base to slightly larger granule. 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 broader than dactyl at base (11.2 mm). Scattered, short setae present in posterior ventral part of fixed finger, reaching from palm to about one-third of cutting edge. Cutting edge of fixed finger with row of rather small granular teeth at posterior half.

Outer lateral margin of chelae smooth with white, translucent patch covering about two-thirds of lateral margin. Row of 7–8 small mesial propodal granules with 4 more prominent spiny granules at dorsolateral margin. Dorsolateral margins slightly elevated in posterior half. Dorsal surface of carpus (14.4 mm) smooth, with slight excavation in middle part and with two well-developed mesial carpal spines. Ventral carpal surface margins slightly elevated, setose, and with fovea; inner margin with well-developed ventral carpal spine and prominent ventromesial carpal spine oriented at an angle of approximately 45 ◦. Merus (35.2 mm) laterally depressed in basal part; surface smooth; prominent dorsal meral spine present. Inner ventrolateral margin smooth; four ventral meral spines present: one at first third, one at mid-length, other at tip of anterior part, and fourth on distal ventrolateral inner margin. Ischium (17.4 mm) smooth with two small spines at ventrolateral inner margin.

Second pereopods reaching anteriorly to approximately mid-length of scaphocerite. Propodus (15.5 mm) and dactylus (7.5 mm) slightly longer than fixed finger (6.8 mm), of same height. Few scattered, short setae present on dactyl and fixed finger. Cutting edge of dactyl and propodus with row of dense, short setae. Carpus (12.3 mm), smooth, slightly pitted. Merus 20.9 mm. Ischium (7.0 mm) about one-third as long as merus.

Third pereopods overreaching second pereopods to mid-length of carpus. Fingers shorter than palm. Fourth pereopods reaching distal margin of scaphocerite. Dactylus (4.5 mm) with corneous tip; no setae present. Propodus (16.0 mm) more than three times as long as dactylus, somewhat flattened, carrying many stiff setae on lower margin. Carpus (9.8 mm) about twice as long as dactylus. Merus (14.3 mm). 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 68.6 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. Total length 128.9 mm.

Description of female allotype (Figure 32). Chela of first pereopods equal, 2.5 times as long as broad (31.8 mm and 12.4 mm, respectively). Mesial margin of palm slightly elevated, forming slender serrated ridge with row of 10–11 small granular teeth, of which 6 are a bit bigger and spinier. Cutting edge of dactylus with 10–11 rather small granular teeth, 1 slightly bigger. Cutting edge of fixed finger with 10–11 small granules, 1 slightly bigger. 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. No soft patch present. Pleon narrower than cephalothorax (width 22.4 mm and 24.1 mm, respectively). Rostrum broad in shape, reaching middle of first antennular peduncle and about 1.5 times as long as wide (width 7.7 mm at base, length 11.8 mm). Margins slightly elevated continuing in rostral carinae on carapace, almost straight in basal part, distal third, pointing upwards at an angle of approximately 45 ◦. Acumen with anteriorly orientated spine. Rostral margins with two spines on each side on anterior third. 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 1/4 of CL. Cervical and branchiocardiac grooves distinct, not setose; 4–5 small granules present at middle part behind cervical groove on lateral sides of carapace. Carapace surface smooth; numerous granules posterior to cervical groove on lateral carapace present. Anterior margin strongly produced; rounded upper margin directed inward. Areola smooth, pitted, small granules present in posterior quarter of areola; length, 15.6 mm; narrowest width 9.4 mm. Length of areola 31.4% of total length of carapace (49.7 mm). Same color pattern as in males. Total length 111.0 mm.

Size. The variation in size in the studied sample of C. nigli n. sp. is given in Table 2, which also provides comparisons with all other newly described species.

Color. The living animals (Figure 29A–D) are colored as follows. Individuals of C.nigli n. sp. usually have blue and white chelipeds with white joints and a red spot right posterior to the joints (Figure 29A). Fingers dark blue with orange yellowish hooked tips. Carpus often red and black. In the blue color variation (Figure 29B), the carpus is often also dark blue. Body is creamy or yellowish with dark green pattern on the dorsal carapax, becoming creamy ventrally. Some individuals have light blue coloration with dark blue pattern or more greenish with a dark green pattern on the dorsal carapace (Figure 29C). Walking legs creamy white with some reddish and blueish spots. Some individuals have blueish walking legs. Pleon dark blue with light blue and creamy transverse bands. Lateral pleura becoming creamy. Females (Figure 29D): same color as males with smaller chelae. Females do not show the creamy white soft patch.

Molecular phylogenetic results. Cherax nigli n. sp. forms a highly supported, distinct clade that is a sister species to a highly supported clade comprising C. communis and C. paniaicus. The clade comprising these three species is moderately (16S; Figure 5) or highly supported (16S and COI combined; Figure S1), respectively, and its relationship to the other species in the northern group is unresolved. Cherax nigli n. sp. is well isolated from C. communis and C. paniaicus, with a sequence divergence (p-distance) of 4.1–4.5% (16S) and 3.8–4.2% (16S)/11.0–11.2% (COI), respectively, supporting the morphology-based description of C. nigli as a new species.

Systematic remarks. In comparison to all species of the northern group, the new species Cherax nigli n. sp. is morphologically and genetically most similar to C. paniaicus and C. communis. Cherax nigli n. sp. may be easily distinguished from both species by the coloration and pattern of live individuals, by the shape of the chelae (Figure 33), by the shape of the rostrum (Figure 34), and by DNA barcoding (Figures 5 and S 1).

Color comparison. Individuals of Cherax nigli n. sp. usually have blue and white chelipeds with white joints and a red spot right posterior to the joints. Fingers dark blue with orange yellowish hooked tips. Carpus often red and black. In the blue color variation, the carpus is often also dark blue. Body is creamy or yellowish with dark green pattern on the dorsal carapace becoming creamy ventrally. C. communis has azure-blue chelae, sometimes greenish-blue. Body usually greenish-blue with some brown. The chelae in C. paniaicus are usually blueish-grey, the body is dark grey to almost black dorsally.

Chelae comparison (Figure 33A–C). In Cherax nigli n. sp. (Figure 33A), the movable finger is usually 1/6 shorter than the dorsolateral margin of the palm. Soft patch is present in the males covering about two-thirds of the lateral margin. Row of 7–8 small mesial propodal granules with 4 more prominent spiny granules at dorsolateral margin. In C. communis (Figure 33B), the movable finger is about as long as the dorsolateral margin of the palm. No 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 10–11 rather weakly developed granules present. Scattered, short setae are present on the ventral part of the fixed finger and palm. In C. paniaicus (Figure 33C), the movable finger is about one-third longer than the dorsolateral margin of the palm. No setae are present on the ventral part of the fixed finger and palm. No soft patch at the outer margin of the palm is present in males.

Rostrum comparison (Figure 34A–C). The rostral margins of C herax nigli n. sp. (Figure 34A) have two spines on each side on anterior third of rostrum, while the rostrum of C. communis (Figure 34B) has 5–6 spiny granules and the rostrum of C. paniaicus (Figure 34C) 6–8 spiny granules on each side of the rostrum. In Cherax nigli n. sp., the rostrum is 1.4 times as long as broad, in C. communis 1.3 times, and in C. paniaicus 1.5 times as long as broad.

Systematic position. Molecular work in particular has shown that the traditional classification of Cherax into two subgenera is not justified, supporting rather a division into three lineages, dubbed the southwestern group, eastern group, and northern group [30,33] (see a short overview by Lukhaup et al. 2024 [14] for more details). Our molecular phylogenetic results (Figure 5), as well as the morphological data [20,23,32,33], clearly showed that Cherax nigli n. sp. belongs to the northern species group lineage, now consisting of 35 species.

Ecology. Cherax nigli n. sp. is endemic to creeks and rivers in the southern part of Kaimana Regency. To protect the species, we will not reveal the exact location. One of the creeks harboring these crayfish is clear, shallow (20–120 cm), with a moderate flow. The temperature is around 23–25 ◦ C. In most parts, no water plants are present. The substrate of the creek is soil, mostly covered with silt and detritus. Crayfish hide in short burrows in the riverbank, under larger rocks or wood, 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.

Distribution (Figure 9). Southeast of Kaimana Regency, West Papua, Indonesia.

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

Etymology. Cherax nigli n. sp. is named in honor of Herbert Nigl, an aquarium wholesaler who for the last 25 years supported us by helping to obtain new crayfish species from Papua. His continuing effort is essential for achieving a better understanding of the crayfish of this region.