Phylladiorhynchus koumac, Rodríguez-Flores & Macpherson & Machordom, 2021

Rodríguez-Flores, Paula C., Macpherson, Enrique & Machordom, Annie, 2021, Revision of the squat lobsters of the genus Phylladiorhynchus Baba, 1969 (Crustacea, Decapoda, Galatheidae) with the description of 41 new species, Zootaxa 5008 (1), pp. 1-159 : 67-74

Phylladiorhynchus koumac n. sp.

( Figs. 21L , 25 , 54I )

Type material. Holotype. New Caledonia, Koumac 2.3 Stn KB 629, 20.59121°S, 164.21503°E, 10 m, 7 November 2019: F 1.6 mm (MNHN-IU-2019-3427).

Paratypes. New Caledonia. LIFOU Stn 1436, 20.9250°S, 167.0700°E, 10–20 m, 10 November 2000: 1 F 1.8 mm (MNHN-IU-2014-13847) .

New Caledonia. Koumac 2.3 Stn KL 07, 20.64605°S, 164.18498°E, 82 m, 15 November 2019: 1 M 1.5 mm (MNHN-IU-2014-20121).— Stn KL 22, 20.4459°S, 163.97176°E, 47 m, 19 November 2019: 1 F 1.4 mm (MNHN- IU-2014-20170) parasitized.— Stn KL 25, 20.75421°S, 164.22986°E, 65 m, 10 November 2019: 1 F 1.8 mm (MNHN-IU-2014-20035).— Stn KL 03, 20.67485°S, 164.214266°E, 50 m, 11 November 2019: 1 F 1.8mm (MNHN- IU-2014-20069) .

Etymology. Named after the expedition KOUMAC aimed to catalogue the marine biodiversity of the lagoons of Koumac, New Caledonia. The name is considered as a substantive in apposition.

Description. Carapace: Robust or massive, [0.9]–1.1 × as long as broad; transverse ridges elevated, serrated, with few short setae, and few scattered long thick iridescent setae. Gastric region convex (upraised dorsally), with some transverse ridges: epigastric ridge indistinct, with 5 spines (1 median and 2 pairs of small spines laterally); anterior protogastric ridge not medially interrupted, laterally with some scales, posterior protogastric region often with a few scales; anterior mesogastric ridge scale-like, laterally interrupted by anterior branch of cervical groove; anterior metagastric ridge scale-like, followed by few scales on posterior metagastric area. Mid-transverse ridge uninterrupted or minutely interruped, medially depressed, preceded by distinct cervical groove, followed by 1–2 uninterrupted or minutely interrupted ridges, interspersed with 2 short lateral ridges and scattered short scales. Lateral margins clearly convex, with 7 spines: first anterolateral spine well-developed, reaching end of lateral orbital spine, second spine (hepatic) well-developed, slightly dorsomesially from lateral margin, and followed by 5 branchial spines (3 anterior and 2 posterior). Rostrum leaf-like, horizontal, dorsally flattish or slightly concave, 1.3–[1.4] × as long as broad, length 0.4 and breadth 0.3 that of carapace; lateral margins serrated and convex, with well-developed supraocular spines, subapical spines well-developed. Pterygostomian flap ending in blunt tooth, upper margin serrated, with series of uprised striae.

Thoracic sternum: As wide as or slightly wider than long, lateral margins of posterior half slightly divergent. Sternite 3 moderately broad, 2.5–[2.8] × as wide as long, anterior margin concave. Sternite 4 widely contiguous to sternite 3; surface flattened, smooth; greatest width 2.7–[2.9] × that of sternite 3, 2.6 × as wide as long.

Pleon: Elevated ridges upraised dorsally, with a few scattered short setae. Tergites 2–3 with anterior and posterior transverse elevated ridges; tergite 4 with anterior transverse ridge; tergites 5–6 smooth.

Eye: Eyestalk length about 1.4–[1.6] × broader than long, peduncle distally setose, not distinctly expanded proximally; maximum corneal diameter 1.1 × rostrum width, as wide as eyestalk.

Antennule: Article 1 slightly longer than wide, with 4 spines: distomesial spine well-developed; proximal lateral spine absent.

Antenna: Article 1 with prominent mesial process distally clearly not reaching lateral antennular spine. Article 2 with small distal spines laterally and mesially. Article 3 often with a minute mesial spine. Article 4 unarmed.

Mxp3: Ischium with distinct distal spines on flexor and extensor margins. Merus 0.6 × length of ischium at midlength, with 0–1 median and 1 well-developed distal spines on extensor margin and 1 strong spine on flexor margin.

P1: [2.5]–3.0 (males) × carapace length, not known in females, subcylindrical, spiny and with scattered long stiff setae; merus, carpus and palm with spines along mesial, dorsal and lateral surfaces, distal and mesial spines usually stronger than others. Merus [1.0]–1.1 length of carapace, [2.1]–2.7 × as long as carpus. Carpus [2.2] × as long as wide. Palm [1.3]–1.4 × carpus length, 2.1–[2.8] × as long as broad. Fingers unarmed, [0.7]–0.8 × palm length.

P2–4 (lost in most specimens): Stout, subcylindrical, moderately setose and spinose, with few scattered plumose setae. Meri successively shorter posteriorly: P3 merus [0.6] × length of P2 merus, P4 merus [0.9] × length of P3 merus; P2 merus, [0.6] × carapace length, [5] × as long as broad, [1.1] × as long as P2 propodus; P3 merus [4.4] × as long as broad, [0.9] × as long as P3 propodus; P4 merus [3.3] × as long as broad, [0.8] × as long as P4 propodus; extensor margin of P2 and P3 with row of spines, proximally diminishing, with prominent distal spine; P4 extensor margin irregular, with small distal spine; flexor margins of P2–4 irregular, each with distal spine. Carpi with 1 or 2 spines on extensor margin on P2–3, unarmed on P4; row of small spines below extensor margin on lateral surface of P2–3, unarmed on P4; flexor margins with distal spine. Propodi moderately slender, 6–7 × as long as broad; extensor margin irregular, usually armed with 1–3 well-developed spines on P2–4; flexor margin with 2–5 slender movable spines in addition to distal pair. Dactyli 0.7–0.8 × length of propodi, ending in incurved, strong, sharp spine; flexor margin with 5–6 movable spines.

Eggs. No data.

Live colour. Body grey or red, with median pale band. P2–4 whitish, with brownish-grey bands.

Genetic data. COI and 16S, Table 1.

Distribution. New Caledonia, Koumac, between 10 and 82 m.

Remarks. Phylladiorhynchus koumac belongs to the species group that has 5 epigastric spines, 3 spines on the anterior branchial margin, gastric region strongly convex, the leaf-like rostrum (margins clearly convex and subapical spines present), and elevated ridges upraised dorsally. The new species closely resembles P. pulchrus , from French Polynesia, the Philippines, and Vanuatu (see the differences under the Remarks of this species).

The specimens of P. koumac range from 1.4 to 1.8 mm postorbital carapace length. The four sequences of P. koumac from New Caledonia diverged 0–0.5% for COI and 0% for 16S.

Figures

FIGURE 21. Rostrum, dorsal view. A, Phylladiorhynchus euryalus n. sp., paratype male 1.8 mm (UF34732). B, P. gustavi n. sp., paratype male 1.7 mm (UF9756). C, P. heptacanthus n. sp., holotype female 2.1 mm (MNHN-IU-2017-2534). D, P. hylas n. sp., paratype female 1.6 mm (MNHN-IU-2016-495). E, P. integrirostris (Dana, 1852), male 1.6 mm (UF15285). F, P. integrus (Benedict, 1902), ovigerous female 3.2 mm (MNHN-IU-2014-13853). G, P. iphiclus n. sp., holotype ovigerous female 2.3 mm (MNHN-IU-2019-2662). H, P. janiqueae n. sp., paratype male 1.8 mm (MNHN-IU-2016-482). I, P. jeffkinchi n. sp., paratype male 2.7 mm (MNHN-IU-2014-13565). J, P. joannotae n. sp., paratype male 2.1 mm (MNHN-IU-2014-20055). K, P. joannotae n. sp., holotype ovigerous female 2.1 mm (MNHN-IU-2014-13805). L, P. koumac n. sp., paratype male 1.5 mm (MNHN-IU- 2014-20121). Scale bars: 1 mm.

FIGURE 25. Phylladiorhynchus koumac n. sp., holotype female 1.6 mm (MNHN-IU-2019-3427): A, carapace and pleon, dorsal view. B, thoracic sternites 3 and 4. C, right cephalic region, showing antennular and antennal peduncles, ventral view. D, right Mxp3, lateral view. E, left P1, dorsal view. F, right P2, lateral view. G, left P3, lateral view. H, left P4, lateral view. I, dactylus of right P2, lateral view. Scale bar: A, E–H = 1.0 mm; B–D, I = 0.6 mm.

FIGURE 54. Colour in life, dorsal view. A. Phylladiorhynchus acastus n. sp. Papua New Guinea, male 2.5 mm (MNHN-IU- 2014-10017). B, Phylladiorhynhus barbeae n. sp. Papua New Guinea, paratype male 1.6 mm (MNHN-IU-2014-13810). C, Phylladiorhynhus barbeae n. sp. Papua New Guinea, male 2.5 mm (MNHN-IU-2014-13813). D, Phylladiorhynchus gustavi n. sp. French Polynesia, male 2.3 mm (UF16338). E, Phylladiorhynchus janiqueae n. sp. Walter shoal, male 1.8 mm (MNHN-IU- 2014-13840). F, Phylladiorhynchus jeffkinchi n. sp. Papua New Guinea, ovigerous female 2.2 mm (MNHN-IU-2014-2176). G, Phylladiorhynchus joannotae n. sp. French Polynesia, ovigerous female 2.2 mm (UF15544). H, Phylladiorhynchus joannotae n. sp. New Caledonia, female 1.0 mm (MNHN-IU-2014-20147). I, Phylladiorhynchus koumac n. sp. New Caledonia, male 1.5 mm (MNHN-IU-2014-20121).