Phylladiorhynchus serrirostris ( Melin, 1939 )

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 : 129-133

Phylladiorhynchus serrirostris ( Melin, 1939)

( Figs. 49 , 50H )

Galathea serrirostris Melin, 1939: 72 : figs 43–47 (type locality: Port Lloyd, Tokinoura, Hatsume, E of Chichijima (Bonin Islands), shallow to 128 m).— Miyake & Baba, 1965: 590, figs 5, 6 (Bonin Islands).

Records requiring verification:

Galathea serrirostris . — Miyake & Baba, 1966 a: 67, fig. 8 (Amami-oshima, Ryukyu Islands, Japan, intertidal).

Phylladiorhynchus serrirostris .— Baba, 1969: 4 (W of Tanegashima, S Kyushu, Japan, 35–40 m).— Baba, 1977: 251 ( Ternate, 2–4 m).— Baba, 1979: 644 (Marsegu Island, subtidal).— Tirmizi & Javed, 1980: 260, fig. 3 ( Mozambique Channel, off South Africa, off Somalia Republic, and Andaman Sea, 38–138 m).— Baba, 1989: 61 ( Palau Islands, subtidal).—Peyrot- Clausade, 1989: 112 (Tuamotu Archipelago, 5–30 m).— Baba, 1990: 969 ( Madagascar, 60 m).— Poupin, 1996 a: 20 (compilation of French Polynesia records).

Type material. Lectotype. Japan, Bonin Islands (Ogasawara), Port Loyd, Dr. Sixten Bocks Japan exp. 1914, 23/7, Djup (depth): dykare (diver), Botten (bottom): korall (coral), det. G. Melin: ov. F 2.9 mm ( UPSZTY 183822 ).

Paralectotypes. Dr. Sixten Bocks Japan exp. 1914. Bonin Islands (Ogasawara), Port Loyd. 23/7. Djup: dykare. Botten: korall. Det. G. Melin: 12 M 1.9–3.0 mm, 11 ov. F 2.1–3.0 mm, 1 F parasitized 1.9 mm, 1 broken ( UPSZTY 2531 ) .

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 some transverse ridges: epigastric ridge distinct with 2 median spines, often followed by few short scales; anterior protogastric ridge not medially interrupted, nearly extending laterally to carapace margin, followed by a posterior protogastric scale-like ridge; anterior mesogastric ridge not medially interrupted, often followed by some scales on posterior mesogastric area; anterior metagastric ridge entire or minutely medially interrupted, followed by a short median scale. Mid-transverse ridge not interrupted, cervical groove indistinct, followed by 2–3 not interrupted or minutely interrupted ridges, interspersed with 1–2 interrupted ridges. Lateral margins distinctly convex, with 4 distinct spines: first anterolateral spine well-developed, reaching anteriorly to level of lateral orbital spine, hepatic margin unarmed; anterolateral spine followed by 3 branchial spines (2 anterior and 1 posterior). Rostrum leaf-like, horizontal, dorsally concave, [1.4]1.2–1.7 × as long as broad, length [0.3]–0.4 and breadth [0.2]–0.3 that of carapace; lateral margins serrated and slightly convex, with well-developed supraocular basal spines and small subapical spines. Pterygostomian flap ending in acute tooth, upper margin often slightly serrated.

Thoracic sternum: As wide as long. Sternite 3 moderately broad, [2.0]–2.1 × as wide as long, anterior margin serrated and convex, slightly produced anterolaterally. Sternite 4 widely contiguous to sternite 3; anterolaterally serrated, surface depressed in midline, smooth; greatest width 2–[3] × that of sternite 3, [2.7] × as wide as long.

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

Eye: Eyestalk length about [0.8]–0.9 × broader than long, peduncle distally setose, not distinctly expanded proximally; maximum corneal diameter [0.6] × 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 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: 2.4–3.0 (males), [2.4]–3.0 (females) × carapace length; subcylindrical, densely spiny and densely with long stiff setae; merus, carpus and palm with several rows of spines along mesial, dorsal and lateral surfaces, distal and mesial spines usually stronger than others. Merus 0.6–[0.9] length of carapace, 1.6–[2.0] × as long as carpus. Carpus 1.4–[1.6] × as long as wide. Palm [1.1]–1.4 × carpus length, 1.4–[1.6] × as long as broad. Fingers [0.8]–0.9 × palm length fixed finger with 2 basal spines; movable finger with 1 basal spines and spine at mid-length.

P2–4: Stout, setose and spinose. Meri successively shorter posteriorly: P3 merus 0.7 × length of P2 merus, P4 merus 0.8 × length of P3 merus. P2 merus, 0.4–[0.6] × carapace length, [4.2]3.5–4.5 × as long as broad, [1.2]0.9–1.3 × as long as P2 propodus; P3 merus [3.1]–4 × as long as broad, [1.2]0.9–1.3 × as long as P3 propodus; P4 merus [3.8] × as long as broad, [0.9] × 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 1–2 spines,; flexor margin irregular, with distal spine on P2–4; P4 lateral surface with 2–3 spines. Carpi with 2–4 well-developed spines on extensor margin on P2–3, unarmed on P4; distal spine prominent on P2–3, smaller on P4; flexor margin unarmed. Propodi stout, [4.0–5.0]3.6–5.0 × as long as broad; extensor margin irregular, armed with 1–4 spines on P2–P4; flexor margin with 3–4 slender movable spines in addition to distal pair. Dactyli [0.5–0.6]0.5–0.8 × length of propodi, ending in incurved, strong, sharp spine; flexor margin with 4–6 movable spines.

Eggs: Ov. F carried approximately 10– 50 eggs of 0.2–0.4 mm diameter.

Live colour. Unknown.

Genetic data. No data.

Distribution. Japan: Bonin Islands, Ryukyu Islands, intertidal to 128 m.

Remarks. Phylladiorhynchus serrirostris was described as Galathea serrirostris by Melin (1939), from specimens collected in Bonin Islands, Japan. Tirmizi (1966) considered G. serrirostris identical to G. pusilla , but Miyake & Baba (1965, 1967) considered G. pusilla and G. serrirostris as close, but not identical, species. After, Baba (1991) included P. serrirostris as a junior synonym of P. integrirostris . The study of the type material of P. serrirostris and its comparison with the numerous specimens of P. integrirostris suggests that they can be considered as different species. Therefore, we have considered P. serrirostris as a valid species. The 2 species belong to the group of species having 2 epigastric spines, hepatic margin unarmed and 2 spines on the anterior branchial margin. Phylladiorhynchus serrirostris is easily differentiable from P. integrirostris by the following characters:

- The anterior metagastric ridge is not medially interrupted in P. serrirostris , whereas it is medially interrupted in P. integrirostris .

- The posterior gastric ridges (posterior protogastric, mesogastric and metagastric) are usually present in P. serrirostris , whereas they are absent in P. integrirostris .

- The pleonal tergite 3 has 2 ridges (anterior and posterior) in P. serrirostris , whereas there is only the anterior ridge in P. integrirostris .

- The P1 is densely spinose in P. serrirostris , whereas they are scarcely spinose in P. integrirostris .

The specimens of P. serrirostris range in size from 1.9 to 3.0 mm postorbital carapace length.

Figures

FIGURE 49. Phylladiorhynchus serrirostris (Melin, 1939), lectotype ovigerous female 2.9 mm (UPSZTY 183822):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, 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 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.