Phylladiorhynchus zetes, 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 : 139-144

Phylladiorhynchus zetes n. sp.

( Figs. 50L , 53 , 56C )

Type material. Holotype. French Polynesia, Marquesas Islands, Nuku Hiva, Ohotea Point, W side of Taiohae Bay , 08.9309°S, 140.0978°W, 36 m, 28 November 2012: M parasitized 2.1 mm ( UF30059 ).

Paratypes: French Polynesia. Marquesas Islands. PAKAIHI I TE MOANA Stn MQ 2-GR-B, 08.9371°S, 140.1206°W, 20–23 m, 7 January 2012: 4 M 1.2–1.6 mm, 1 ov. F 2.3 mm, 3 F 1.2–1.7 mm (MNHN-IU-2019- 2639) .

Other material. French Polynesia. Marquesas Islands. PAKAIHI I TE MOANA Stn MQ 11-GRS, 10.0140°S, 139. 10°00.845’S, 139°07.345’W 1224°W, 6–12 m, 15 January 2012: 1 F 1.7 mm (MNHN- IU-2019-2602).— Stn MQ 15-GR-B, 10.4718°S, 138.6780°W, 0–28 m, 17 June 2012: 2 M 2.0– 2.2 mm (MNHN-IU-2019-2593).— Stn MQ 19-B, 09.7612°S, 138.8449°W, 10–25 m, 21 January 2012: 2 M 1.8–2.3 mm (MNHN-IU-2019-2600).— Stn MQ 27-GR-B, 08.6781°S, 140.6205°W, 5–22 m, 25 January 2012: 1 M 1.5 mm (MNHN-IU-2019-2589) .

French Polynesia. BENTHAUS Stn DW1926 , 24.6360°S, 146.0136°W, 50–90 m 13 November 2002: 1 F parasitized 2.4 mm (MNHN-IU-2014-13873).— Society Islands. Moorea Islands . 17.5044°S, 149.7584°W, 65–66 m, 26 January 2012: 1 M 1.5 mm ( UF33537 ) .— 17.5044°S, 149.7584°W, 65–66 m, 26 January 2012: ov. F 1.4 mm ( UF33536 ) .— 17.5526°S, 149.7735°W, 57 m, 27 January 2012: 1 M 1.5 mm ( UF33636 ) .

French Polynesia. Marquesas Islands. MUSORSTOM 9 Stn DW 1203,09.8783°S, 139.0366°W, 60 m, 28August 1997: 1 M 1.8 mm (MNHN-IU-2014-13874).— Stn CP 1264, 09.3550°S, 140.1283°W, 53–57 m, 03 September 1997: 1 M 2.6 mm (MNHN-IU-2019-2640) .

Etymology. From the name Zetes, an Argonaut, son of Boreas and Oreithyia. The name is considered a substantive in apposition.

Description. Carapace: As long as or slightly wider than long; transverse ridges with dense short setae and few long and thick iridescent setae. Gastric region slightly convex with 4 transverse ridges: epigastric ridge indistinct with 2 median spines and some, and several lateral short scales; anterior protogastric ridge not medially interrupted, nearly extending laterally to carapace margin; anterior mesogastric ridge not medially interrupted, laterally continuing to first branchial spine; anterior metagastric scale-like, often followed by small scale. Midtransverse ridge not interrupted, medially slightly depressed, preceeded by shallow or indistinct cervical groove, followed by 2 not interrupted or laterally interrupted ridges, interspersed with 1 short lateral ridge and few short scales. Lateral margins straight or slightly convex, with 6 distinct spines: first anterolateral spine well-developed, reaching anteriorly to level of lateral orbital spine, second spine (hepatic) small, slightly dorsomesial from lateral margin, and followed by 3–4 branchial spines (3 anterior and 0–1 posterior). Rostrum leaf-like, horizontal, dorsally convex, 1.3–[1.5] × as long as broad, length 0.4 and breadth 0.3 that of carapace; lateral margins minutely serrated and convex, with well-developed supraocular basal spines and subapical spines small. Pterygostomian flap with anterior spine, upper margin smooth.

Thoracic sternum: As wide as long. Sternite 3 moderately broad, 1.9–[2.0] × as wide as long, anterior margin convex. Sternite 4 widely contiguous to sternite 3; anterolaterally smooth, surface depressed in midline, smooth; greatest width 2.5–[2.7] × that of sternite 3, [2.7]–2.8 × 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; tergite 3 with anterior transverse ridge, posterior transverse ridge interrupted; tergite 4 with anterior transverse ridge; tergites 5–6 smooth.

Eye: Eyestalk length about [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 0.7–[1.0] × 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. Article 2 with well-developed distomesial and distolateral spines. Articles 3 and 4 unarmed.

Mxp3: Ischium with distinct distal spines on flexor and extensor margins. Merus 0.6–[0.8]× length of ischium, with well-developed distal spine on extensor and flexor margins.

P1: [2.6]–3.0 (males), 2.3–2.4 (females) × carapace length; subcylindrical, spiny and with long stiff setae; merus, carpus and palm with spines along mesial, dorsal and lateral surfaces, distal and mesial spines stronger than others. Merus 0.8–[1.0] length of carapace, 1.6–[2.0] × as long as carpus. Carpus [1.7]–2.5 × as long as wide. Palm 1.0–[1.2] × carpus length, [1.8]1.8 × as long as broad. Fingers 0.7–[0.8] × 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–[0.9] × length of P2 merus, P4 merus 0.8–[0.9] × length of P3 merus. P2 merus, 0.6–[0.7] × carapace length, 3.0–[3.5] × as long as broad, 1.1–[1.4] × as long as P2 propodus; P3 merus 3.6–[3.7] × as long as broad, 1.0–[1.3] × as long as P3 propodus; P4 merus 3.5–[3.8] × as long as broad, 0.9–[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 P2–4. Carpi with 1–2 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 stout, [3.5–3.7]3.1–3.9 × as long as broad; extensor margin irregular, armed with 0–3 spines; flexor margin with 3–4 slender movable spines in addition to distal pair. Dactyli 0.6–[0.7] × length of propodi, ending in incurved, strong, sharp spine; flexor margin with 5–6 movable spines.

Eggs: Ov. F carried approximately 12– 20 eggs of 0.2–0.3 mm diameter.

Live colour. Body light orange, with small orange spots and wittish patches and bands. P1 whitish, palm and fingers orange, distal tip finger darker. P2–4 light whitish-translucent.

Genetic data. COI and 16S, Table 1.

Distribution. French Polynesia, 20 to 23 m.

Remarks. Phylladiorhynchus zetes 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 posterior ridge interrupted. Phylladiorhynchus zetes closely resembles P. tiphys from New Caledonia but they can be distinguished by the following characters:

- One scale with thick setae between the epigastric spines in P. tiphys , whereas this scale is absent in P. zetes .

- Thoracic sternite 3 is quadrangular (less than twice as long as wide) in P. tiphys , whereas this sternite is moderately broad (more than twice as long as broad) in P. zetes .

- The P2–4 propodi are usually stout in P. zetes (3.1–3.9 × as long as broad), whereas they are more slender in P. tiphys (3.5–4.5 as long as broad).

Phylladiorhynchus zetes is also highly similar to P. medea , also found in French Polynesia and New Caledonia. Both species can be distinguished by the following characters:

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

- Pleonal tergite 3 has a posterior ridge in P. zetes , whereas this ridge is absent in P. medea .

- The P2–4 propodi are usually stout in P. zetes (3.1–3.9 × as long as broad), whereas they are more slender in P. medea (3.5–4.5 as long as broad).

The genetic divergences among P. zetes , P. tiphys and P. medea ranged from 7–11% (COI) and 3–6% (16S). The two sequences of P. zetes from French Polynesia diverged by 0.2% (COI) and 0% (16S). The specimens of P. zetes range from 1.2 to 2.6 mm postorbital carapace length.

Figures

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 53. Phylladiorhynchus zetes n. sp., A–D, G–H, holotype male 2.1 mm (UF30059):A, carapace and pleon, dorsal view. B, thoracic sternites 3 and 4. C, left cephalic region, showing antennular and antennal peduncles, ventral view. D, left Mxp3, lateral view. E, left P1, dorsal view. F, left P2, lateral view. G, right P3, lateral view. H, left P4, lateral view. I, dactylus of right P3, lateral view. Scale bars: 1.0 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.