Phylladiorhynchus paula, 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 : 100-102

Phylladiorhynchus paula n. sp.

( Figs. 33P , 38 , 55E )

Type material. Holotype. Mayotte and Comores Islands, BIOMAGLO Stn DW 4800, 11.4500°S, 47.3166°E, 240– 255 m, 24 January 2017: M 3.7 mm (MNHN-IU-2016-7002).

Paratypes. Reunion Island. MD32 Stn DC 2, 21.2066°S, 55.8233°E, 160–190 m, 12 August 1982: 1 M 2.7 mm (MNHN-IU-2019-2691).— Stn CP 177, no data: 1 M 2.3 mm (MNHN-IU-2019-2699) .

Mayotte and Comores Islands. BIOMAGLO Stn DW 4800, 11.4500°S, 47.3166°E, 240–255 m, 24 January 2017: 1 F 3.3 mm (MNHN-IU-2016-7003).— Stn DW 4838, 11.9833°S, 43.5166°E, 185–267 m, 29 January 2017: 1 ov. F 3.4 mm (MNHN-IU-2017-428) .

Etymology. Named after our colleague Paula Martin-Lefèvre, Collection Manager in the Muséum national d’Histoire naturelle, Paris. The name is considered a substantive in apposition.

Description. Carapace: as long as or slightly longer than broad; transverse ridges with few short setae. Gastric region flattened with 4 transverse ridges: epigastric ridge indistinct, with 5 spines (1 median and 2 pairs of spines laterally); anterior protogastric ridge not medially interrupted or minutely medially interrupted, nearly extending laterally to carapace margin; anterior mesogastric ridge not medially interrupted, laterally interrupted by anterior branch of cervical groove, continuing to first branchial spine; anterior metagastric ridge scale-like. Mid-transverse ridge not interrupted, medially depressed, preceded by shallow to distinct cervical groove, followed by 2 not interrupted or minutely interrupted ridges, interspersed with 1–2 short lateral ridges and sometimes few, short scattered scales. Lateral margins slightly convex, with 7 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 5 branchial spines (3 anterior and 2 posterior). Rostrum triangular, horizontal, dorsally flattish or slightly concave, [1.2]–1.8 × as long as broad, length 0.3–[0.4] and breadth 0.2–[0.3] that of carapace; lateral margins smooth and straight or slightly concave, with well-developed supraocular spines, subapical spines absent. Pterygostomian flap ending in blunt tooth, upper margin smooth.

Thoracic sternum: 1.2 as wide as long. Sternite 3 moderately broad, [2.3]2.0–3.0 × as wide as long, anterior margin straight or with a median feeble excavation, moderately produced anterolaterally.Sternite 4 widely contiguous to sternite 3; surface not depressed in midline, smooth; greatest width 2.0–[3.0] × that of sternite 3, [2.5]2.0–3.0 × as wide as long.

Pleon: Transverse elevated ridges with short setae. Tergite 2 with anterior and posterior transverse elevated ridges; tergites 3 and 4 with anterior transverse ridge; tergites 5–6 smooth.

Eye: Eyestalk length about 1.0–[1.2] × broader than long, peduncle distally setose, not distinctly expanded proximally; maximum corneal diameter 1.0 × rostrum width, as wide as eyestalk.

Antennule: Article 1 1.5 × longer than wide, with 5 spines: distomesial spine small; 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 distal spines, distomesial larger than distolateral. Article 3 with often with a small to distinct distomesial spine. Article 4 unarmed.

Mxp3: Ischium with distinct distal spines on flexor and extensor margins. Merus [0.6]0.6 × length of ischium, with well-developed distal spine on extensor margin and 2 strong spines on flexor margin.

P1: 2.8–[3.5] (males), 2.8–3.0 (females) × carapace length; 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–[1.3] length of carapace, [1.8]–2.5 × as long as carpus. Carpus [2.0]–2.4 × as long as wide. Palm [1.1]–1.4 × carpus length, [1.5]–2 × as long as broad. Fingers [0.9]–1.0 × longer than palm; fixed finger unarmed or with basal spine; movable finger with well-developed basal spine.

P2–4: Slender, subcylindrical, moderately setose and spinose. Meri successively shorter posteriorly: P3 merus [0.7]–0.8 × length of P2 merus, P4 merus [0.8]–0.9 × length of P3 merus. P2 merus, [0.8]–0.9 × carapace length, 5.6–[6.0] × as long as broad, 1.4 × as long as P2 propodus; P3 merus [6.5]–7.1 × as long as broad, [1.2]–1.4 × as long as P3 propodus; P4 merus [5.0]–5.4 × as long as broad, 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, withdistal spine; flexor margins of P2–4 irregular, each with distal spine; P4 lateral surface with median row 4 small spines, absent in others. Carpi with 3 or 4 spines on extensor margin on P2–3, unarmed on P4; distal spine prominent on P2–3, minute on P4; row of small spines below extensor margin on lateral surface of P2–3, unarmed on P4; flexor margin unarmed. Propodi slender, [7.2–7.3]7.0–7.5 × as long as broad; extensor margin irregular, usually unarmed; flexor margin with 3–4 movable spines in addition to distal pair. Dactyli 0.5–[0.6] × length of propodi, ending in incurved, strong, sharp spine; flexor margin with [7–8]6–8 movable spines.

Eggs: Ov. F (MNHN-IU-2017-428) carried 18 eggs of 0.3–0.4 mm diameter.

Live colour. Body pale orange, with golden-yellow spots. P1 orange, with whitish. P2–4 light orange, with dark bands.

Genetic data. COI and 16S, Table 1.

Distribution. Mayotte and Comores Islands, Reunion Island, between 160 and 267 m.

Remarks. Phylladiorhynchus paula belongs to the group of species that present 5 epigastric spines, the rostrum margin straight, the subapical spines of the rostrum absent, 3 spines on the anterior branchial margin, and the Mxp3 merus with two prominent spines along the flexor margin. Phylladiorhynchus paula closely resembles to P. acastus , from the Philippines, Papua New Guinea, Vanuatu, Chesterfield Islands and New Caledonia, and P. argus , from French Polynesia, New Caledonia and Chesterfield Islands, however, they can be distinguished by the following characters:

- The dorsal carapace ridges have scattered long thick iridescent setae in P. acastus , whereas these setae are absent in P. paula and they are short in P. argus .

- The anterior mesogastric ridge is medially interrupted in P. argus , whereas it is not medially interrupted in P. acastus and P. paula .

- Pleonal tergite 3 has 2 ridges (anterior and posterior) in P. acastus , whereas there is only one anterior ridge in P. argus and P. paula .

- The shape of thoracic sternite 3 is broad in P. argus , being more than 4 × as wide as long, compared to moderately broad in P. acastus and P. paula (2–3 × as wide as long).

- Antennal article 3 has a small to well-developed distomesial spine in P. paula and P. acastus , whereas this article is unarmed in P. argus .

The genetic distances between these species were always quite large: P. paula diverged 10–12% (COI) and 3– 5% (16S) from P. argus and P. acastus . The two sequences of P. paula from Mayotte and Comores Islands diverged 0.6% for COI and 0% for 16S. The specimens of P. paula range from 2.3 to 3.7 mm postorbital carapace length.

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 38. Phylladiorhynchus paula n. sp., holotype male 3.7 mm (MNHN-IU-2016-7002): 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, right P1, dorsal view. F, left P2, lateral view. G, right P3, lateral view. H, dactylus of left P2, lateral view. Scale bar: A, E–G = 1.0 mm; B–D, H = 0.5 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).