Neocallichirus nagoi, Poore, 2023

Poore, Gary C. B., 2023, New records and one new species of Callichiridae (Crustacea, Axiidea) from the Indo-West Pacific, with keys to species of Corallianassa, Lepidophthalmus and Neocallichirus, Memoirs of Museum Victoria (Mem. Mus. Vic.) 82, pp. 71-95 : 87-90

Neocallichirus nagoi sp. nov.

https://zoobank.org/urn:lsid:zoobank.org:act:5B5DF4DF-D589-

45E6-8042-BAC8949A91F5

Figures 10, 11

Neocallichirus PNG-1589.—Robles et. al., 2020: figs 1, 4, 7.

Material examined. Holotype. Papua New Guinea. New Ireland, Nago I. wharf, 0–1 m, 02° 36.2'S, 150° 46.1'E, 6 Oct 2014 (KAVIENG 2014 stn KM03 ), MNHN IU-2014-10052 (male, 6.6 mm).

Paratypes, collected with holotype, MNHN IU-2014- 10417 * (female, 6.2 mm); MNHN IU-2016-8148 * (male, 7.9 mm); MNHN IU-2016-8149 * (male, 5.5 mm); MNHN IU-2014-10418 (3 males, 5.2–6.0 mm); 3–12 m, sand (KAVIENG 2014 stn KR06), MNHN IU-2014-1157 * (male, 5.8 mm). NMV J62087 (3 males, 5.2– 6.0 mm) .

Diagnosis. Antenna peduncle exceeding antennule peduncle by half of article 5. Eyestalk distal lobes triangular, rounded, diverging. Major cheliped merus lower margin evenly convex, denticulate; gape simple; fixed finger cutting edge concave, denticulate over proximal half; dactylus cutting edge entire. Uropodal endopod posterior margin convex-oblique, angle with anterior margin rounded. Telson scarcely tapering from subproximal width to broadly rounded posterolateral corner.

Description. Carapace c. 0.25 total length; with distinct linea thalassinica, with defined dorsal oval marked posteriorly by deep transverse cervical groove extending anteroventrally to each side above linea thalassinica as shallow groove demarcating posterior half of dorsal oval; frontal margin continued ventrolaterally beyond anterolateral lobe as soft ridge towards linea thalassinica. Branchiostegite with oblique ridge terminating at anterior end of prominent rounded hepatic boss; anterior branchiostegal lobe articulating at junction of oblique ridge and linea thalassinica. Rostrum slightly convex in lateral view, broadly triangular, reaching almost to cornea; anterolateral lobe flat, rounded in dorsal view, sometimes with small tubercle. Pleon with approximate ratio of pleonites 1–6 (along midline) 1: 1: 1: 1: 1.2: 1.3; pleonites 3–5 with lateral tufts of setae; pleonite 6 with submarginal transverse grooves.

Eyestalk 1.5 times as long as wide, parallel-sided over proximal half, tapering beyond dorsally prominent hemispherical cornea, distal lobes flat, subtriangular, diverging distally, reaching end of antennal article 1. Antennular peduncle 0.4 times carapace length, article 3 1.5 times as long as article 2, with ventromesial and ventrolateral rows of long setae. Antennal peduncle exceeding antennular peduncle by half article 5, articles 4 and 5 subequal in length; scaphocerite semicircular. Maxilliped 3 setation typical of genus; ischium wider distally, extensor margin slightly concave, 1.5 times distal margin, flexor margin convex, crista dentata curved, of c. 22 uneven short sharp spines; merus subtriangular, slightly wider than long, flexor margin broadly rounded; carpus subtriangular, 1.5 times as long as wide, with lobe on flexor margin; propodus slightly wider than long, free distal margin slightly oblique; dactylus slightly arcuate, shorter than propodus.

Pereopods 1 (chelipeds) unequal, dissimilar, scarcely sexually dimorphic, relatively smaller in female. Major cheliped (male) carpus–dactylus 1.2 times carapace length; ischium slender, lower (flexor) margin with denticles over distal half; merus twice as long as wide, upper margin arcuate, lower margin curved, with c. 10 denticles over proximal two-thirds; carpus as long as wide, lower proximal margin regularly curved; propodus upper margin slightly longer than carpus, as long as greatest width, widest subproximally, upper margin carinate over proximal two-thirds, lower margin with submarginal mesial denticles extending on to base of fixed finger; palm distomesial margin with 2 tubercles at base of fixed finger; fixed finger 0.4 length of lower margin, twice as long as width at base, cutting edge with c. 9 triangular blunt teeth over proximal two-thirds, smooth beyond; dactylus as long as upper margin of palm, cutting edge with irregular blade over proximal half, with acute hooked tip. Minor cheliped (male) barely shorter than major, palm 0.6 width of major palm; ischium narrow, unarmed, as long as merus; merus 3 times as long as wide, margins curved, unarmed; carpus almost as long as merus, 1.7 times as long as wide, widest near midpoint; palm upper margin half as long as carpus, 0.9 times as long as wide, lower margin 1.2 times as long as carpus; fixed finger evenly tapering, half length of lower margin, cutting edge with 5 well spaced denticles over middle third; dactylus 1.6 times as long as upper margin of palm, curved, cutting edge unarmed.

Major cheliped (female) carpus–dactylus 0.8 times carapace length; ischium slender, lower (flexor) margin with minute denticles; merus twice as long as wide, upper margin arcuate, lower margin curved, with c. 10 denticles over proximal two-thirds; carpus 1.2 times as long as wide, lower proximal margin regularly curved; propodus upper margin as long as carpus, little longer than greatest width, widest subproximally, upper margin of palm forming unserrated keel in proximal half, lower margin with submarginal mesial denticles extending on to base of fixed finger; palm distomesial margin unarmed; fixed finger 0.4 length of lower margin, twice as long as width at base, cutting edge with c. 9 triangular blunt teeth over proximal two-thirds, smooth beyond; dactylus as long as upper margin of palm, cutting edge with irregular blade over proximal half, with acute hooked tip. Minor cheliped (female) barely shorter than major, palm 0.6 width of major palm; ischium narrow, unarmed, as long as merus; merus 2.5 times as long as wide, margins curved, unarmed; carpus almost as long as merus, 1.7 times as long as wide, widest near midpoint; palm upper margin half as long as carpus, 1.1 times as long as wide, lower margin 0.8 times as long as carpus; fixed finger evenly tapering, half length of lower margin, cutting edge with 7 well-spaced denticles over middle third; dactylus 1.5 times as long as upper margin of palm, exceeding fixed finger, curved, cutting edge unarmed.

Pereopod 2 merus 3 times as long as wide; carpus 1.8 times as long as wide; chela almost as long as carpus, 1.6 times as long as wide; dactylus 0.7 of chela. Pereopod 3 merus 3 times as long as wide; carpus twice as long as wide; propodus with proximally directed lobe of lower margin aligned with lower margin of carpus, with subsquare proximal angle, with rounded margin leading to straight lower margin, upper margin convex; dactylus teardrop-shaped, 1.8 times as long as wide. Pereopod 4 linear, merus 4.5 times as long as wide; subchela poorly developed. Pereopod 5 fully chelate, fixed finger depressed.

Male pleopod 1 of 2 articles (in juveniles of 1 article or absent); article 2 0.7 time length of article 1, with lateral constriction at about midpoint, with linear appendix interna embedded in distal half of mesial margin, without hooks. Male pleopod 2 peduncle twice as long as wide; endopod slightly shorter than exopod, with subdistal appendix interna reaching end of endopod; without appendix masculina. Female pleopod 1 simple, of 2 articles; article 2 half length of article 1, simple. Female pleopod 2 essentially similar to male. Pleopods 3–5 with short, stubby appendix interna embedded into mesial margin of endopod.

Uropodal endopod as long as wide, anterior margin convex, with rounded corner to distal margin, distal and posterior margins continuous with slightly more exaggerated curvature between, dorsal surface with soft longitudinal carina; exopod 1.5 times as wide as anterior margin, anterior margin almost straight, distal and posterior margins evenly curved, dorsal plate ending submarginally, extending half width of exopod. Telson 1.35 times as wide as long, broadest at lateral lobes in anterior third, tapering at about 10°, posterior margin weakly sinuous, posterolateral corners broadly rounded, each bearing tuft of long setae; dorsal surface elevated anteromedially, with shallow median groove over posterior half.

Size. Cl. males 5.2–7.9 mm, female 6.2 mm.

Etymology. Nagoi is a contraction of Nago Island, the type locality, a noun in apposition.

Distribution. Eastern Coral Triangle (known only from type locality, Papua New Guinea).

Remarks. All specimens from this collection are similar in size; all except one is a male with open gonopores on the coxae of pereopod 5. The second article of the male pleopod 1 does not have two sharp curved apices typical of the genus, and that of the female is relatively short. These appear immature compared with those of most other species of Neocallichirus . The lower margin of the cheliped merus lacks a toothed blade, having instead a row of tubercles, a condition found in N. darwinensis , N. horneri and N. moluccensis . These species differ as follows. Neocallichirus darwinensis has reduced cornea, a more tapered telson, narrower minor cheliped and distally excavate propodus on maxilliped 3. Neocallichirus horneri has a more tapered telson, a more prominent lobe on the propodus of pereopod 3 and a shorter lower margin on the merus of maxilliped 3. The cornea of N. moluccensis is dorsally prominent as in the new species, but the distal eyestalk lobes are more truncate and the telson more tapered.

Robles et al. (2020) found N. nagoi (as N. PNG-1589) to be sister to a clade containing specimens of N. calmani from the Philippines and French Polynesia, a species from which it differs in many ways.