Phylladiorhynchus poeas, 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 : 113-115

Phylladiorhynchus poeas n. sp.

( Figs. 43 , 50B , 56A )

Type material. Holotype. French Polynesia. BENTHAUS Stn DW 1866, 28.9833°S, 140.2475°W, 50–100 m, 4 November 2002: M 2.8 mm (IU-2014-13736).

Paratypes. French Polynesia. BENTHAUS Stn DW 1866, 28.9833°S, 140.2475°W, 50–120 m, 4 November 2002: 5 M 2.2–3.5 mm, 5; ov. F 2.1–3.4 mm 2 F 3.0– 3.4 mm, 1 M 3.4 mm (MNHN-IU-2016-9658), 1 M 2.5 mm (MNHN-IU-2014-13859).— Stn DW 1867, 28.9833°S, 140.2333°W, 127–170 m, 4 November 2002: 2 M 2.0– 2.2 mm (MNHN-IU-2019-2681).— Stn DW 1876, 28.9833°S, 140.2500°W, 150–160 m, 4 November 2002: 2 M 2.1–2.8 mm (MNHN-IU-2019-2693).— Stn DW 1898, 27.5666°S, 144.4500°W, 580–820 m, 8 November 2002: 1 M 3.3 mm (MNHN-IU-2014-13737) .

Other material. French Polynesia. BENTHAUS Stn DW 1877, 28.9833°S, 140.2500°W, 59–150 m, 4 November 2002: 1 M 2.8 mm (MNHN-IU-2014-13904), 8 M 2.3–3.7 mm, 5 ov. F 2.5–3.4 mm, 3 F 2.5–2.8 mm (MNHN-IU-2014-13738), 1 M 3.6 mm (MNHN-IU-2014-13731), 9 M 1.7–4.0 mm, 8 F 2.0- 3.1 mm (MNHN-IU- 2019-2677), 1 M 3.4 mm, 1 ov. F 2.8 mm (MNHN-IU-2016-9634).— Stn DW 1880, 27.9133°S, 143.4908°W, 90–94 m, 6 November 2002: 2 M 2.0- 2.3 mm, 4 ov. F 1.8–2.8 mm (MNHN-IU-2019-2682), 3 M 2.1–2.8 mm, 1 ov. F 2.0 mm (MNHN-IU-2014-13857).— Stn DW 1881, 27.9166°S, 143.4833°W, 112-121 m, 6 November 2002: 1 M 2.2 mm (MNHN-IU-2019-2684), 1 ov. F 2.6 mm (MNHN-IU-2019-2680).— Stn DW 1894, 27.6688°S, 144.3585°W, 100 m, 8 November 2002: 2 M 1.8-2.2 mm (MNHN-IU-2019-2664), 1 ov. F 2.4 mm (MNHN-IU-2019-2661).— Stn CP 1908, 27.4166°S, 144.0166°W, 100–118 m, 9 November 2002: 3 M 2.3–3.4 mm, 1 ov. F 2.5 mm, 2 F 2.0– 2.2 mm (MNHN-IU-2019-2683).— Stn CP 1918, 27.0500°S, 146.0666°W, 130–140 m, 12 November 2002: 1 M 2.3 mm (MNHN-IU-2019-2685).— Stn DW 1936, 24.6616°S, 145.9515°W, 80-100 m, 14 November 2002: 1 ov. F 2.0 mm (MNHN-IU-2019-2663).— Stn DW 1939, 23.8278°S, 147.6936°W, 100 m, 15 November 2002: 1 M 2.0 mm (MNHN-IU-2019-2679).— Stn DW 2013, 22.6428°S, 152.8288°W, 80–93 m, 25 November 2002: 1 M 2.3 mm (MNHN-IU-2019-2678) .

Etymology. From the name Poeas, an Argonaut, son of Thaumacus and father of Philoctetes. The name is considered a substantive in apposition.

Description. Carapace: as long as or slightly longer than broad; transverse ridges with dense short setae and few scattered long and thick setae. Gastric region slightly convex with 4 transverse ridges: epigastric ridge distinct with 1, 2 or 3 (in largest specimens) pairs of spines in transverse row, innermost pair always the largest, outer pairs (when present) smaller, sometimes indicated by granules; anterior protogastric ridge non interrupted medially, nearly extending laterally to carapace margin; anterior mesogastric ridge not medially interrupted, laterally interrupted by cervical groove, laterally continuing to first branchial spine; anterior metagastric ridge scale-like. Mid-transverse ridge uninterrupted, preceded by distinct cervical groove, followed by 2 uninterrupted or minutely interrupted ridges, interspersed with 1 short lateral ridge. Lateral margins convex, with 6–7 spines: first anterolateral spine well-developed, reaching anteriorly to level of lateral orbital spine, second spine (hepatic) small to obsolescent, slightly dorsomesially from lateral margin, and followed by 4–5 branchial spines behind distinct anterior cervical groove (3 anterior and 1–2 posterior). Rostrum leaf-like, horizontal, dorsally flattish or slightly concave, [1.6]–1.8 × as long as broad, length [0.4]–0.5 and breadth [0.2]–0.3 that of carapace; lateral margins serrated and convex, with well-developed supraocular basal spines and small subapical spines. Pterygostomian flap with anterior spine; upper margin smooth.

Thoracic sternum: As wide as long. Sternite 3 moderately broad, 1.5–[2.2] × as wide as long, anterior margin convex, often serrated, moderately produced anterolaterally. Sternite 4 widely contiguous to sternite 3; surface depressed in midline, smooth; greatest width 2.7–[2.8] × that of sternite 3, 2.4–[2.7] × as wide as long.

Pleon: Elevated ridges with short setae and a few scattered long setae. Tergite 2 with anterior and posterior transverse elevated ridges; tergites 3–4 with anterior transverse ridge only; tergites 5–6 smooth.

Eye: Eyestalk length about 0.8 × broader than long, peduncle distally setose, not distinctly expanded proximally; maximum corneal diameter 0.9 × rostrum width, as wide as eyestalk.

Antennule: Article 1 slightly longer than wide, with 5 distal spines: distomesial spine well-developed; proximal lateral spine small, always present.

Antenna: Article 1 with prominent mesial process, distally falling well short of lateralmost antennular spine. Article 2 with well-developed distomesial and distolateral spines. Article 3 with distomesial spine. Article 4 unarmed.

Mxp3: Ischium with distinct distal spines on flexor and extensor margins. Merus [0.6]–0.7 × length of ischium, with well-developed distal spine on extensor and flexor margins.

P1 (lost in holotype): 2.8–3.1 (males), 2.4–2.5 (females) × carapace length; subcylindrical, spiny and with dense 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, 1.7–1.9 × as long as carpus. Carpus 1.4–1.8 × as long as wide. Palm 1.2–1.3 × carpus length, 1.8–2.4 × as long as broad. Fingers 0.7–0.8 × palm length; fixed finger with several proximal spines; movable finger with 1 well-developed basal spine and several small spines or granules along dorsal margin.

P2–4: Densely setose and spinose. Meri successively shorter posteriorly: P3 merus 0.8 × length of P2 merus, P4 merus 0.9–1.0 × length of P3 merus. P2 merus, 0.6 × carapace length, [4.0]–4.4 × as long as broad, [1.2]–1.6 × as long as P2 propodus; P3 merus 3.6–4.0 × as long as broad, 1.3–1.4 × as long as P3 propodus; P4 merus 2.7–[3.8] × as long as broad, [1.1]–1.2 × 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, unarmed; flexor margin irregular, with distal spine on P2–3, distal spine absent in P4. Carpi with 0–2 prominent spines on extensor margin on P2–3, unarmed on P4; distal spine prominent on P2–3, smaller on P4; row of small spines below extensor margin on lateral surface of P2–3, unarmed on P4; flexor margin unarmed. Propodi moderately stout, [5.0–5.5]4.5–6.0 × as long as broad; extensor margin irregular, armed with 1–4 distinct well-developed spines; flexor margin with 3-4 slender movable spines in addition to distal pair. Dactyli [0.6]–0.8 × length of propodi, ending in incurved, strong, sharp spine; flexor margin with 4–6 movable spines.

Eggs: Ov. F carried approximately 10– 30 eggs of 0.3 mm diameter.

Live colour. Body light orange to dark orange, covered by orange spots. P1 dark orange, covered by light orange setae. P2–4 light orange, darker on extensor and flexor margins.

Genetic data. COI and 16S, Table 1.

Distribution. French Polynesia, almost all specimens were found between 50 and 160 m. A single specimen was found in a station of 580–820 m depth (MNHN-IU-2014-13737) that we consider as an anomaly.

Remarks. Phylladiorhynchus poeas is morphologically undistinguishable from P. pusillus from Australia, Tasmania and New Zealand and they can be considered as cryptic species. However, genetically they are very different for mitochondrial genes. Schnabel & Ahyong (2019) revised the type material and numerous topotypic specimens of P. pusillus and found that one of the diagnostic characters of the species (4 spines on the epigastric ridge) showed a certain variability. After examination of a large amount of material from Australia, Tasmania and New Zealand, Schnabel & Ahyong (2019) reported a variation in the number and size of the epigastric spines, from 1 to 3 pairs of epigastric spines, with the lateralmost being granules in small specimens. The new species from French Polynesia has a similar variation in this character, with specimens having 2 to 6 spines and/or granules, recommending caution when using this character for species delimitation. Unfortunately, we don’t know the colour pattern of P. pusillus to compare with the colouration of the new species. Therefore, future studies will confirm the existence of additional differences to separate morphologically both species. A subtle character useful to distinguish both species might be the thoracic sternite 3 moderately produced anterolaterally in P. poeas ; whereas with broad granule or square in P. pusillus ( Schnabel & Ahyong 2019) .

The genetic divergences between P. poeas and P. pusillus were 8% (COI) and 2% (16S). No intraspecific divergence was observed in both genes. The specimens of P. poeas range from 1.8 to 3.5 mm postorbital carapace length.

Figures

FIGURE 43. Phylladiorhynchus poeas n. sp., holotype male 2.8 mm (MNHN-IU-2014-13736); C: paratype male 3.3 mm (MNHN-IU-2016-9658): A, carapace and pleon, dorsal view. B, C, thoracic sternites 3 and 4. D, left cephalic region, showing antennular and antennal peduncles, ventral view. E, right Mxp3, lateral view. F, right P1, dorsal view. G left P2, lateral view. H, left P4, lateral view. I, dactylus of right P2, lateral view. Scale bar: A, F–H = 1.0 mm; B–D, I = 0.5 mm.

FIGURE 50. Rostrum, dorsal view. A, Phylladiorhynchus phlias n. sp., paratype male 1.4 mm (MNHN-IU-2014-13881). B, P. poeas n. sp., paratype male 3.3 mm (MNHN-IU-2014-13737). C, P. pollux n. sp., holotype ovigerous female 3.5 mm (MNHN-IU-2014-13797). D, P. porteri n. sp., paratype female 2.4 mm (MNHN-IU-2014-23831). E, P. priasus n. sp., paratype ovigerous female 2.1 mm (UF54422). F, P. pulchrus n. sp., paratype male 1.8 mm (MNHN-IU-2019-2675). G, P. punctatus n. sp., paratype male 1.7 mm (MNHN-IU-2019-20101). H, P. serrirostris (Melin, 1939), paralectotype male 2.3 mm (UPSTY2531). I, P. spinosus Schnabel & Ahyong, 2019, male 3.3 mm (MNHN-IU-2016-492). J, P. talaus n. sp., paratype ovigerous female 2.4 mm (WAM C43997). K, P. tiphys n. sp., holotype male 2.4 mm (MNHN-IU-2014-13794). L, P. zetes n. sp., holotype male 2.1 mm (UF30059). Scale bars: 1 mm.

FIGURE 56. Colour in life, dorsal view. A, Phylladiorhynchus poeas n. sp. French Polynesia, male 2.5 mm (MNHN-IU-2014- 13859). B, Phylladiorhynchus punctatus n. sp. New Caledonia, male 1.7 mm (MNHN-IU-2014-20101). C, Phylladiorhynchus zetes n. sp., French Polynesia, ovigerous female 1.5 mm (UF33536). Colour variability. Phylladiorhynchus lini n. sp. Taiwan. D, paratype ovigerous female 2.5 mm (MNHN-IU-2016-1490). E, paratype ovigerous female 2.7 mm. F, paratype male 2.2 mm. G, paratype ovigerous female 3.0 mm. H, paratype ovigerous female 2.5 mm. I, paratype male 3.0 mm.