Cherax arguni n. sp. Figures 1–9. Material examined. Holotype: male (MZB Cru), under rocks, wood, and among roots and in debris along banks of an unnamed tributary close to Rafa village in the northern part of the Kaimana Regency, West Papua, Indonesia. Coll. by local people, November 2024. Crayfish were sent to Aquarium Dietzenbach by KKCrayfish Farm in Jakarta. Allotype: female (MZB Cru), same data as holotype. Paratypes: one male (MZB Cru); one male and two females (ZMB 34709)—all the same data as the holotype. Diagnosis. Carapace surface smooth with numerous tiny tubercles posterior to cervical groove on lateral carapace. Eyes large, cornea globular, darkly pigmented. Rostrum lanceolate in shape with excavated margins. Rostral margins with two prominent teeth on each side. Rostral carinae prominent. Postorbital ridges prominent with one acute tubercle at anterior terminus. Prominent uncalcified patch on outer lateral margin of chelae of adult male, white, translucent. Chelipeds dark blue and white with white joints. Fingers with hooked tips. Carapace dark blue with white translucent patch on lateral anterior part. Other walking legs dark blue. Pleon dark blue with thin, light, creamy transverse bands. Lateral pleura becoming lighter blue. Description of male holotype (Figures 1A, 2 and 3A–C). Body and eyes pigmented (Figure 1A). Eyes not reduced. Cornea slightly broader than eyestalk. Body subovate, slightly compressed laterally. Pleon narrower than cephalothorax (width 23.0 mm and 27.3 mm, respectively). Rostrum (Figure 3C) broad in shape, pitted, reaching middle of the first antennular peduncle and about 2.2 times as long as wide (width 6.6 mm at base, length 14.6 mm). Margins slightly elevated continuing in rostral carinae on carapace, almost straight in basal part. Acumen with anteriorly orientated spine. Rostral margins with 2 spines on each side on anterior third of rostrum. Few scattered tiny 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 the 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 small spines present at middle part behind cervical groove on lateral sides of carapace. Carapace (60.9 mm) surface smooth; numerous tiny granules posterior to cervical groove on lateral carapace present. Anterior margin strongly produced; rounded upper margin directed inward. Areola smooth, pitted; length 17.3 mm; narrowest width 9.7 mm. Length of areola 28.3% of total length of carapace (60.9 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 16.4 mm long and 5.6 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 thickened; each lateral margin with a group of 6–7 very small tubercles separated by smooth region. Central part smooth, not pitted, excavate. First pereopods (Figure 3A,B) equal in form, chela slightly gaping. Left cheliped 58.4 mm long, 9.7 mm high, and 21.2 mm wide. Right chelae 58.2 mm long (tip missing), 10.7 mm high, and 21.6 mm wide, strongly compressed. Fingers shorter than palm (left dactylus 21.4 mm long). Dactylus broad at base (8.2 mm), tapering slightly toward tip. Tip with sharp, corneous, hooked tooth pointing outwards at an angle of 45 ◦. Cutting edge of dactyl with a continuous row of small granular teeth and one slightly larger granule at mid-length. Ventral and dorsal surface of movable finger smooth with scattered punctuation. Ventral posterior half of cutting edge with scattered setae reaching from base to 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 (9.8 mm). Dense short setae present in the posterior ventral part of fixed finger, reaching from palm to about one-third of cutting edge. Cutting edge of fixed finger with row of seven rather small granular teeth and one bigger one after first third. Outer lateral margin of chelae smooth with a white, translucent patch covering about half of lateral margin. Row of 23–24 slightly elevated mesial propodal granules at dorsolateral margin. Dorsolateral margins slightly elevated in posterior third. Scattered, short hairs present on posterior half of lateral margin. Dorsal surface of carpus (17.3 mm) smooth, with slight excavation in middle part and with two well-developed mesial carpal spines. Ventral carpal surface margins slightly elevated, setose, with fovea; inner margin with well-developed ventral carpal spine and prominent ventromesial carpal spine oriented at an angle of approximately 45 ◦. Merus (27.8 mm) laterally depressed in basal part; surface smooth, pitted; 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 (15.9 mm) smooth with three small granules at ventrolateral inner margin. Second pereopods reaching anteriorly to approximately mid-length of scaphocerite. Propodus (14.0 mm) and dactylus (7.0 mm) slightly longer than fixed finger (5.8 mm), of same height. Few scattered, short setae present on posterior part of dactyl and fixed finger. Cutting edge of dactyl and propodus with row of dense, short setae. Carpus (11.2 mm), smooth, slightly pitted. Merus 18.4 mm. Ischium (8.7 mm) about half as long as merus. Third pereopods overreaching second pereopods to mid-length of carpus. Fingers shorter than palm. Dactylus (6.7 mm) with corneous tip; short, scattered hairs present in posterior half. Propodus (17.0 mm) about three times as long as dactylus, somewhat flattened. Carpus (15.1 mm) more than twice as long as dactylus. Merus 21.6 mm. Fourth pereopods reaching distal margin of scaphocerite. Dactylus (5.7 mm) with corneous tip; short, scattered setae present. Propodus (13.8 mm) about 2.5 times as long as dactylus, somewhat flattened, carrying scattered stiff setae on lower margin. Carpus (9.0 mm) about twice as long as dactylus. Merus 16.3 mm. Fifth pereopods similar to fourth, shorter. Dorsal surface of pleon smooth, heavily pitted; abdominal segments (1–5) with short, creamy colored setae present on caudal margins of segment. Pleon length 69.1 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 130.0 mm. Description of female allotype (Figure 4). Chela of first pereopods equal, three times as long as broad (46.3 mm and 15.1 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, one slightly bigger. Small scattered, short setae visible along ventral cutting edges of chelae, denser and longer in ventral posterior half. Tips of fingers slightly cross when fingers clasp, slightly gaping. No soft patch present. Pleon slightly narrower than cephalothorax (width 28.5 mm and 28.9 mm, respectively). Rostrum broad in shape, reaching middle of first antennular peduncle and about 2.4 times as long as wide (width 7.8 mm at base, length 18.8 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 ◦. Rostral margins with three spines on each side on anterior third of rostrum. Acumen with anteriorly orientated spine. 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; four well-developed spines present at middle part behind cervical groove on lateral sides of one side of carapace and three on the other. Carapace surface smooth; numerous tiny granules posterior to cervical groove on lateral carapace present. Anterior margin strongly produced; rounded upper margin directed inward. Areola smooth, pitted; length, 19.5 mm; narrowest width, 11.8 mm. Length of areola 29.1% of total length of carapace (66.8 mm). Same color pattern as in males. Pleon length 76.7 mm. Total length 143.5 mm. Size. The variation in size in the studied sample of C. arguni n. sp. is given in Table 2, which also provides comparisons with all other newly described species. Color. The living animals (Figure 1A,B) are colored as follows. Individuals of Cherax arguni n. sp. usually have dark blue and white chelipeds with white joints. Carapace dark blue with a creamy patch on lateral anterior part. The other walking legs are dark blue. Pleon dark blue with thin, light, creamy transverse bands. Lateral pleura becoming lighter blue. Females: same color as males with smaller chelae. Females do not show the white translucent soft patch. Molecular phylogenetic results. Cherax arguni n. sp. forms a highly supported, distinct clade that is the well-supported sister species to C. bomberai n. sp.; both species are, in turn, sister to a moderately supported clade comprising C. kaimana n. sp. and C. farhadii n. sp. (Figure 5). The clade comprising these four species is highly supported and very distinct; it is sister group to a clade comprising ten species, including, e.g., C. veritas n. sp. and C. pulcher, but this relationship is only partially supported. Cherax arguni n. sp. is well isolated from C. bomberai n. sp. and C. kaimana n. sp. / C. farhadii n. sp., with a sequence divergence (p-distance) of 1.7–1.9% (16S)/7.8% (COI) and 3.0–3.8% (16S)/11.4% (COI; C. kaimana n. sp. only), respectively, supporting the morphology-based description of C. arguni as a new species. Systematic position. Cherax arguni n. sp. belongs to the northern species group lineage, now consisting of 35 species (please see the respective section for C. nigli n. sp. below for details). Systematic remarks. In comparison to all species of the northern group, the new species, Cherax arguni n. sp., is morphologically and genetically most similar to C. bomberai n. sp., to C. farhadii n. sp., and to C. kaimana n. sp. Cherax arguni n. sp. may be easily distinguished from these three species by the coloration and pattern of live individuals (Figure 6), by the shape of the chelae (Figure 7), by the shape of the rostrum (Figure 8), and by DNA barcoding (Figure 5). Coloration comparison (Figure 6A–D). Individuals of Cherax arguni n. sp. (Figure 6A) usually have dark blue and white chelipeds with white joints. Carapace dark blue with a creamy patch on the lateral anterior part. Other walking legs dark blue. Pleon dark blue with thin, light, creamy transverse bands. Lateral pleura becoming lighter blue. C. bomberai n. sp. (Figure 6B) usually has blue and white chelipeds with white joints. Prominent uncalcified patch on lateral margin of chelae of adult male, white, translucent. Carapace dark blue with orange and greenish stains on the anterior carapace. Fingers with hooked tips. Other walking legs light blue to dark blue. Pleon dark blue with light greenish-blue and creamy transverse bands. Lateral pleura becoming lighter blue-green. C. farhadii n. sp. (Figure 6C) usually has blue chelipeds with white joints. Uncalcified patch on lateral margin of chelae, white, translucent. Fingers with hooked tips. Carapace dark blue or greenish blue, becoming lighter laterally. Numerous creamy to white small spots on lateral and dorsal carapace. Walking legs light blue to dark blue. Pleon dark blue with creamy transverse bands. Lateral pleura becoming lighter green or blue to creamy. Some animals with a pink lateral dot on five segments, others with a yellowish to greenish dot. C. kaimana n. sp. (Figure 6D) usually has blue-greenish and white chelipeds with white joints. Fingers dark blue with orange-yellowish hooked tips. Carpus same color as chela. Body is usually green on top, becoming creamy orange ventrally. Walking legs greyish-blue, sometimes greenish-blue. Pleon dark green to orange, creamy, with creamy transverse bands. Lateral pleura becoming creamy orange with some green. Bright orange lengthwise narrow band from the first segment of the pleon to the fifth segment. Chelae comparison (Figure 7A–F). In C. arguni n. sp., the dorsolateral margins have a row of 23–24 slightly elevated mesial propodal granules at the dorsolateral margin, while 11–12 in C. bomberai n. sp., 11–12 in C. farhadii n. sp., and 19–20 in C. kaimana n. sp. In C. arguni n. sp., the chelae are 2.9 times longer than the movable finger, while in C. bomberai n. sp., the chelae are 2.7 times longer, in C. farhadii n. sp., 2.7 times longer, and in C. kaimana n. sp., they are 2.6 times longer than the movable finger. In C. arguni n. sp., the chelae are 2.6 times as long as broad, in C. bomberai n. sp. 2.3 times, in C. farhadii n. sp. 2.6 times, and in C. kaimana n. sp. 2.7 times as long as broad. In C. arguni n. sp., the claw is not gapping, with longer dense setae in the ventral third, in C. bomberai n. sp., the claw is slightly gapping, with dense short setae in the ventral third of the movable and fixed fingers, in C. farhadii n. sp. there is a moderate wide gap and scattered, short setae present in the ventral third of the movable and fixed fingers, while it is slightly gapping in C. kaimana n. sp., with scattered, short hairs present in the ventral third of the movable and fixed fingers. Rostrum comparison (Figure 8A–C). The rostrum of Cherax arguni n. sp. is well developed and 2.4 times longer than broad, slightly bending outwards, and the rostrum of C. bomberai n. sp. is 2.3 times longer than broad, rather straight, and triangular shaped. The rostrum of C. farhadii n. sp. is 2.2 times as long as broad, while the rostrum of C. kaimana n. sp. is rather straight and triangular shaped and 2.7 times as long as broad.C. arguniC. bomberaiC. doberaiC. farhadiiCharactersMale (n = 3) Female (n = 3) Male (n = 3)Female (n = 2)Male (n = 6)Female(n = 3)Chela length 58.7±0.9 (57.7–59.9) 43.4±2.9 (39.3–46.3) 38.2±8.5 (28.2–49.0) 33±5.6 (27.4–38.6) 25.8 n/a 40.9±9.5 (30.8–59.6) 28.5±0.4 (28.1–29.1) Chela width 20.5±0.8 (19.4–21.2) 14.3±0.6 (13.5–15.1) 15.8±3.5 (12.4–20.7) 12.2±1.1 (11.1–13.3) 11.2 n/a 16.2±4.8 (12.3–26.5) 9.8±0.1 (9.7–10.0) Chela height 7.4±2.9 (3.3–9.7) 6.6±0.5 (6.0–7.3) 8.7±1.8 (6.3–10.8) 7.1±0.5 (6.6–7.6) 7.0 n/a 7.9±2.3 (5.4–12.6) 5.4±0.3 (5.0–5.8) Dactylus 21.1±0.4 (20.6–21.4) 18.9±1.7 (17.7–20.5) 14.9±3.4 (11.1–19.4) 15±2.8 (12.2–17.8) 10.6 n/a 14.7±2.3 (12.2–18.4) 13.3±0.1 (13.2–13.4) Ratio of chela length/width 2.8±0.1 (2.7–3.0) 3.0±0.1 (2.9–3.1) 2.4±0.1 (2.3–2.6) 2.7±0.3 (2.4–2.9) 2.3 n/a 2.6±0.3 (2.2–3.0) 2.8±0.0 (2.8–2.9) Ratio of chela length/dactylus 2.8±0.0 (2.7–2.8) 2.3±0.2 (2.1–2.5) 2.5±0.0 (2.5–2.6) 2.2±0.1 (2.1–2.2) 2.4 n/a 2.7±0.3 (2.3–3.2) 2.1±0.0 (2.1) Rostrum length 15.7±0.9 (14.6–16.7) 16.6±1.7 (14.6–18.8) 12.4±1.5 (10.9–14.5) 13.1±2.5 (10.6–15.6) 5.2 n/a 13.5±2.0 (9.5–15.9) 12.6±0.8 (12.0–13.8) Rostrum width 6.7±0.1 (6.6–6.8) 7.3±0.5 (6.6–7.8) 5.2±0.4 (4.7–5.6) 5.8±0.9 (4.9–6.7) 3.6 n/a 6.2±0.8 (5.2–6.9) 5.8±0.4 (5.3–6.3) Ratio of rostrum length/width 2.3±0.1 (2.2–2.4) 2.2±0.1 (2.1–2.4) 2.3±0.2 (2.0–2.5) 2.2±0.1 (2.1–2.3) 1.4 n/a 2.1±0.2 (1.8–2.4) 2.1±0.1 (2.0–2.2) Areola width middle 9.8±0.3 (9.6–10.2) 11.6±0.1 (11.5–11.8) 8.0±1.2 (6.6–9.6) 9.4±1.3 (8.1–10.7) 4.5 n/a 9.3±1.0 (7.7–10.8) 8.8±0.4 (8.4–9.3) Areola length 18.6±1.1 (17.3–19.9) 19.4±0.3 (19.0–19.8) 15.0±2.1 (13.3–17.9) 16.2±1.9 (14.2–18.1) 10.3 n/a 16.7±1.8 (14.1–18.8) 15.1±0.2 (14.8–15.2) Pleon width 24.4±1.3 (23.0–26.2) 28.4±0.1 (28.3–28.5) 18.8±3.2 (16.3–23.3) 22.05±3.0 (19.0–25.1) 11.7 n/a 21.03±2.3 (17.2–23.1) 20.03±1.5 (18.7–22.4) Pleon length 70.9±1.6 (69.1–73.0) 76.7±0.2 (76.6–77) 57.0±8.6 (50.4–69.1) 65.3±9.3 (56.0–74.5) 36.1 n/a 62.9±6.4 (52.5–69.7) 58.4±3.3 (54.5–62.6) Carapace width 27.8±1.0 (27.0–29.2) 28.4±0.4 (28.1–28.9) 21.2±3.1 (18.7–25.6) 21.8±3.3 (18.5–25.0) 12.3 n/a 23.5±2.9 (18.5–26.2) 21.0±1.1 (19.5–21.7) Carapace length 62.8±2.7 (60.9–66.6) 64.1±2.1 (61.8–66.8) 48.0±7.4 (42.5–58.4) 52.1±8.6 (43.5–60.6) 28.6 n/a 54.3±6.1 (43.0–59.9) 48.0±1.8 (45.8–50.3) Total length 133.7±4.1 (130.0–139.4) 140.8±2.1 (138.4–143.5) 105.0±15.9 (92.9–127.5) 117.3±17.8 (99.5–135.1) 64.7 n/a 117.2±12.3 (95.5–127.7) 106.3±5.2 (100.3–112.9)MaleFemale Distribution (Figure 9). Cherax arguni n. sp. has so far only been found in creeks close to the village of Rafa in the northern part of Kaimana Regency, together with C. kaimana n. sp. It likely occurs at least throughout the entire catchment. Common name. As the common name for this crayfish, we propose the Arguni Creamy Blue Crayfish. Etymology. Arguni is an endangered indigenous language of Indonesia and is spoken on the Bomberai Peninsula, where the species is endemic. It is proposed as a noun in apposition.

Published as part of Lukhaup, Christian, Eprilurahman, Rury & Rintelen, Thomas von, 2025, Seven New Species of Crayfish of the Genus Cherax (Crustacea, Decapoda, Parastacidae) from Western New Guinea, Indonesia, pp. 1-55 in arthropoda 3 (2) on pages 5-16, DOI: 10.3390/arthropoda3020010, http://zenodo.org/record/18484894