Phylladiorhynchus medea, 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 : 92-94

Phylladiorhynchus medea n. sp.

( Figs. 33E , 35 , 55C )

Type material. Holotype. French Polynesia. Rapa , Stn 30, 27.6366°S, 144.3033°W, 16–20 m, 16/ 18 November 2002: M 2.2 mm (MNHN-IU-2016-493).

Paratypes. French Polynesia. Rapa , Stn 30, 27.6366°S, 144.3033°W, 16–20 m, 16/ 18 November 2002: 1 M 2.2 mm (MNHN-IU-2016-493), 6 M 2.0– 2.5 mm (MNHN-IU-2016-509), 1 M broken (MNHN-IU-2016-494), 1 M 2.0 mm, 5 ov. F 2.1–2.7 mm (MNHN-IU-2014-13905).— Stn 32, 27.5966°S, 144.3833°W, 15–20 m, 18/ 23 November 2002: 4 M 2.0– 2.5 mm, 8 ov. F 2.2–2.7 mm (MNHN-IU-2019-2603), 1 M 2.8 mm, 2 ov. F 1.8–2.1 mm, 1 F 2.0 mm (MNHN-IU-2016-1493).— Stn 33, 27.5800°S, 144.3466°W, 30 m, 19 November 2002: 4 M 2.0–3.0 mm, 2 ov. F 2.1–2.5 mm, 1 F 2.0 mm (MNHN-IU-2019-2607).— Stn 36, 27.5583°S, 144.3466°W, 27 m, 21 November 2002: 1 M, 2.5 mm, 4 ov. F 2.0– 2.6 mm (MNHN-IU-2019-2606) .

New Caledonia. Lagon Nord. Stn DW 1097, 19.8616°S, 163.7083°E, 33–34 m, 24 October 1989: 1 M 2.1 mm (MNHN-IU-2014-13795) .

Other material. South China Sea. Macclesfield Bank. Stn 24, 15.4416°N, 114.2333°E, 24–63 m, May 1892: 1 ov. F 2.4 mm (MNHN-IU-2016-9639) .

Chesterfield Islands . CORAIL 2 Stn CP 25, 20.4166°S, 161.0833°E, 67–70 m, 22 July 1988: 1 M 1.6 mm (MNHN-IU-2016-472 (Ga-2050)) .

New Caledonia.Touho. September 1993: 1 ov. F 2.4 mm (MNHN-IU-2019-2616).— Koumac 2.3 Stn KL 25, 20.75421°S, 164.22986°E, 65 m, 10 November 2019: 1 M 1.4 mm (MNHN-IU-2014-20045).— Stn KL 03, 20.67485°S, 164.214266°E, 50 m, 11 November 2019: 2 ov. F 2.0– 2.3 mm (MNHN-IU-2014-20052), 1 F parasitized 1.9 mm (MNHN-IU-2014-20063).— Stn KB 642, 20.7093°S, 164.25715°E, 28 m, 14 November 2019: 2 M 1.7–broken (MNHN-IU-2014-20109).— Stn KB 647, 20.664116°S, 164.189983°E, 38 m, 16 November 2019: 2 M 1.5–2.0 mm (MNHN-IU-2014-20140).— Stn KL 22, 20.4459°S, 163.97176°E, 47 m, 19 November 2019: 2 M 1.9–2.0 mm (MNHN-IU-2014-20158). 2 M 1.5–1.7 mm, 2 ov. F 1.9–2.0 mm, 3 postlarvae 0.9–1.0 mm (MNHN- IU-2014-20169) .

French Polynesia. BENTHAUS Stn CP 1918, 27.0500°S, 146.0666°W, 130–140 m, 12 November 2002: 3 M 2.5 mm, 5 ov. F 2.5–3.4 mm (MNHN-IU-2019-2591).— Stn CP 1922, 27.0667°S, 146.0667°W, 150–163 m, 12 November 2002: 1 ov. F 2.1 mm (MNHN-IU-2019-2597).—Rapa. Stn 4, 27.5716°S, 144.3683°W, 18 m, 4 November 2002: 7 M 2.0– 3.4 mm, 3 ov. F 2.6–3.0 mm, 5 F 1.5–2.0 mm (MNHN-IU-2019-2585, MNHN-IU-2014- 13908).—Stn 5, 27.0933°S, 144.3083°W, 8 m, 4 November 2002: 4 M 2.6–3.4 mm, 3 ov. F 2.5–3.6 mm (MNHN- IU-2019-2587).—Stn 9, 27.6216°S, 144.3700°W, 3–24 m, 6 November 2002: 1 M 2.2 mm (MNHN-IU-2014- 13907), 1 ov. F 2.2 mm (MNHN-IU-2014-13901).—Stn 10, 27.5800°S, 144.3800°W, 16–18 m, 7 November 2002: 1 ov. F 2.5 mm (MNHN-IU-2019-2584).—Stn 11, 27.6200°S, 144.3033°W, 2 m, 7 November 2002: 1 ov. F 2.2 mm (MNHN-IU-2019-2605).—Stn 14, 27.5966°S, 144.2266°W, 2 m, 8 November 2002: 1 M 2.1 mm, 1 ov. F 2.3 mm (MNHN-IU-2019-2586).—Stn 16, 27.6050°S, 144.3066°W, 5 m, 8 November 2002: 1 ov. F 2.1 mm (MNHN-IU- 2014-13906).—Stn 20, 27.5900°S, 144.3883°W, 5 m, 12 November 2002: 4 ov. F 2.2–2.8 mm (MNHN-IU-2019- 2588).—Stn 25, 27.6400°S, 144.3150°W, 3 m, 13 November 2002: 1, ov. F, 1.8 mm (MNHN-IU-2014-13902).—Stn 27, 27.6450°S, 144.3116°W, 6 m, 14 November 2002: 1 M 2.3 mm (MNHN-IU-2014-13910).—Stn 29, 27.5716°S, 144.3500°W, 2–4 m, 15 November 2002: 1 M 2.7 mm, 4 ov. F, 2.0– 2.6 mm (MNHN-IU-2019-2636), 1 ov. F 2.2 mm (MNHN-IU-2014-13903) .

Etymology. From the name Medea, daughter of Aeetes, joined the Argo when the Fleece was recovered. 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 iridescent setae. Gastric region slightly convex with 4 transverse ridges: epigastric ridge distinct with 2 median spines and some lateral short scales, often followed by some short scales; anterior protogastric ridge not medially interrupted, extending laterally to carapace margin followed by some short scales posteriorly; anterior mesogastric ridge not medially interrupted, laterally interrupted by cervical groove; anterior metagastric scale-like, often followed by some short scales. Mid-transverse ridge uninterrupted, medially slightly depressed, cervical groove distinct, followed by 2 not interrupted or minutely interrupted ridges, interspersed with 1 short lateral ridge and some short scales. Lateral margins nearly straight, with 6 distinct spines: first anterolateral spine well-developed, reaching anteriorly to level of lateral orbital spine, second spine (hepatic) small, slightly dorsomesially from lateral margin, and followed by 4 branchial spines (3 anterior and 1 posterior). Rostrum leaf-like, horizontal, dorsally convex,

1.3–[1.5] × as long as broad, length 0.3–[0.4] and breadth [0.2]–0.3 that of carapace; lateral margins serrated and convex, with well-developed basal supraocular spines, subapical spines absent or obsolescent. Pterygostomian flap with anterior spine, upper margin serrated.

Thoracic sternum: As wide as long. Sternite 3 moderately broad, [1.5]–2.9 × as wide as long, anterior margin convex, anterolaterally rounded. Sternite 4 widely contiguous to sternite 3; anterolaterally serrated, surface depressed in midline, smooth; greatest width 2.2–[3.5] × that of sternite 3, 2.3–[3.0] × 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; tergites 5–6 smooth.

Eye: Eyestalk length about 1.0–[1.1] × broader than long, peduncle distally setose, not distinctly expanded proximally, with few short transverse striae on lateral surfaces; cornea expanded distally, maximum corneal diameter 0.8–[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 not reaching lateralmost antennular spine. Article 2 with well-developed distomesial and distolateral spines. Article 3 and 4 unarmed.

Mxp3: Ischium with distinct distal spines on flexor and extensor margins. Merus 0.7–[0.8] × length of ischium, with well-developed distal spine on extensor and flexor margins.

P1 (lost in holotype): 2.5–3.8 (males), 2.6 (females) × carapace length, subcylindrical, spiny and with long stiff setae; merus, carpus and pam with spines along mesial, dorsal and lateral surfaces, distal and mesial spines usually stronger than others. Merus 0.8 length of carapace, 2.2 × as long as carpus. Carpus 1.8 × as long as wide. Palm 1.6 × carpus length, 3.4 × as long as broad. Fingers 0.5 × palm length, fixed finger with 2 basal spines; movable finger with 1–2 basal spines.

P2–4: stout, setose and spinose. Meri successively shorter posteriorly: P3 merus 0.9 × length of P2 merus, P4 merus [0.8]–0.9 × length of P3 merus. P2 merus, 0.6–[0.7] × carapace length, [4.0]–4.5 × as long as broad, [1.2]–1.3 × as long as P2 propodus; P3 merus [3.5]–4.1 × as long as broad, 1.1–[1.2] × as long as P3 propodus; P4 merus 3.6–[3.7] × as long as broad, 0.9–[1.0] × 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, absent on P4. Carpi with 2 spines on extensor margin on P2–3, unarmed on P4; distal spine prominent on P2–3, absent on P4; granules below extensor margin on lateral surface of P2–4; flexor margin unarmed. Propodi moderately stout, [4.5–5.5]4.5–6.3 × as long as broad; extensor margin irregular; flexor margin with 3–6 slender movable spines in addition to distal pair. Dactyli 0.5–0.7 × length of propodi, ending in incurved, strong, sharp spine; flexor margin with 5–6 movable spines.

Eggs: Ov. F carried approximately 10– 25 eggs of 0.3–0.4 mm diameter.

Live colour. Base colour of body light orange-yellow, with small dark orange spots. P1 whitish, distal tip finger orange. P2–4 light whitish-translucent, covered by whitish spots and dark orange stripes.

Genetic data. COI and 16S, Table 1.

Distribution. South China Sea (Macclesfield Bank), New Caledonia and French Polynesia, between 2 and 163 m.

Remarks. Phylladiorhynchus medea belongs to the group of species having 2 epigastric spines, 1 hepatic spine, 3 spines on the anterior branchial margin and the pleonal tergite 3 with the anterior ridge only. The new species closely resembles P. janiqueae , but both species can be distinguished by the following characters:

- The rostrum has small subapical spines in P. janiqueae , whereas these spines are absent or obsolescent in P. medea .

- The anterior upper margin of the pterygostomian flap is smooth in P. janiqueae , whereas this margin is usually serrated in P. medea .

- The antennal article 3 has a small distomesial spine in P. janiqueae , whereas this spine is absent in P. medea .

Phylladiorhynchus medea is also close to P. zetes from the French Polynesia (see the differences under the Remarks of this species).

The specimens of P. medea range from 0.9 to 3.4 mm postorbital carapace length. The genetic divergences between P. medea and P. janiqueae were 11% (COI) and 6% (16S). The six sequences of P. medea from New Caledonia and French Polynesia diverged 0.6% (COI) and 0.3% (16S).

Figures

FIGURE 33. Rostrum, dorsal view. A, Phylladiorhynchus laureae n. sp., paratype female 1.7 mm (MNHN-IU-2019-2635). B, P. lini n. sp., holotype female 2.2 mm. C, P. lynceus n. sp., holotype ovigerous female 2.0 mm (MNHN-IU-2019-2593). D, P. marina n. sp., male 1.5 mm (MNHN-IU-2019-2653). E, P. medea n. sp., paratype male 2.1 mm (MNHN-IU-2014-13795). F, P. nudus Macpherson, 2008, ovigerous female 2.4 mm (WAM C46587). G, P. nui Schnabel & Ahyong, 2019, male 6.5 mm (MNHN-IU-2019-2595). H, P. orpheus n. sp., paratype male 1.9 mm (UF33962). I, P. paula n. sp., paratype male 2.3 mm (MNHN-IU-2019-2699). J, P. penelos n. sp., paratype male 3.3 mm (UF1224). K, P. pepei n. sp., holotype male 3,2 mm (MNHN-IU-2016-486). L, P. phanus n. sp., paratype male 2.1 mm (MNHN-IU-2019-2687). Scale bars = 1 mm.

FIGURE 35. Phylladiorhynchus medea n. sp., A–D, F–I, holotype male 2.2 mm (MNHN-IU-2016-493); E, paratype male 2.8 mm (MNHN-IU-2016-1493): A, carapace and pleon, dorsal view. B, thoracic sternites 3 and 4. C, left cephalic region, showing antennular and antennal peduncles, ventral view. D, right Mxp3, lateral view. E, left P1, dorsal view. F, left P2, lateral view. G, left P3, lateral view. H, right P4, lateral view. I, dactylus of left P2, lateral view. Scale bar: A, E–H = 1.0 mm; B–D, I = 0.6 mm.

FIGURE 55. Colour in life, dorsal view.A, Phylladiorhynchus lini n. sp. Taiwan, holotype female 2.2 mm (NMMBCD5596). B, Phylladiorhynchus marina n. sp. Vanuatu, ovigerous female 2.0 mm (MNHN-IU-2014-13887). C, Phylladiorhynchus medea n. sp. New Caledonia, female 1.9 mm (MNHN-IU-2014-20063). D, Phylladiorhynchus orpheus n. sp. French Polynesia, ovigerous female 2.0 mm (UF9732). E, Phylladiorhynchus paula n. sp. îles de Mayotte. des Glorieuses et des Comores, female 3.3 mm (MNHN-IU-2016-7003). F, Phylladiorhynchus peneleos n. sp. French Polynesia, male 2.0 mm (UF16078). G, Phylladiorhynhus pepei n. sp. Madagascar, male 3.2 mm (MNHN-IU-2016-486). H, Phylladiorhynchus phanus n. sp. Papua New Guinea, ovigerous female 2.5 mm (MNHN-IU-2014-2893). I. Phylladiorhynchus phlias n. sp. Papua New Guinea, ovigerous female 1.3 mm (MNHN-IU-2013-703).