Peronia okinawensis Dayrat & Goulding, 2020

Dayrat, Benoit, Goulding, Tricia C., Apte, Deepak, Aslam, Sadar, Bourke, Adam, Comendador, Joseph, Khalil, Munawar, Ngo, Xuan Qu ảng, Tan, Siong Kiat & Tan, Shau Hwai, 2020, Systematic revision of the genus Peronia Fleming, 1822 (Gastropoda, Euthyneura, Pulmonata, Onchidiidae), ZooKeys 972, pp. 1-224 : 1

Peronia okinawensis Dayrat & Goulding sp. nov. Figs 17 , 18 , 19 , 20

Type material.

Holotype. Japan • holotype, hereby designated, 27/25 mm [696-4 H]; Okinawa, Kunigami, Bay just SE of Cape Hedo; 26°51.803'N, 128°15.863'E; 3 Jul 2004; G Paulay, J Jeller, M Malay & Y Hiratsuka leg.; reef flat; UF 352288.

Additional material examined.

Japan • 2 specimens 25/20 mm [696-3] and 20/17 mm [696-2]; same collection data as for the holotype; UF 352288.

Distribution

(Fig. 6 ). Endemic to Okinawa, Japan.

Etymology.

Peronia okinawensis is named after its type locality: okinawensis is a latinized adjective that agrees in gender (feminine) with the generic name ( ICZN 1999: Article 31.2).

Habitat.

The only specimens known were found on a reef flat. Peronia okinawensis seems to be rare compared to P. verruculata (unit #1) but may be more abundant at some other sites in Okinawa. It would be interesting, in the future, to map in detail at what exact sites the three Peronia species that are sympatric in Okinawa ( P. okinawensis , P. peronii , and P. verruculata ) overlap or not, in Okinawa and possibly in the rest of the Ryukyu Islands.

Color and morphology.

No picture of live animals is available. The color of preserved specimens is beige mottled with darker areas dorsally and whitish ventrally. The dorsal notum of live animals is covered by dozens of papillae of various sizes. Some papillae bear black dorsal eyes at their tip. The number of papillae with dorsal eyes is variable (8-15). The largest specimens are 27 mm long.

Digestive system

(Figs 17A , 18 ). Examples of radular formulae are presented in Table 5 . The median cusp of the rachidian teeth is approximately 45 μm long. The hook of the lateral teeth is approximately 110 μm long. The intestinal loops are of type I, with a transitional loop oriented between 12 to 3 o’clock.

Reproductive system

(Figs 17B, C , 19 , 20 ). In the anterior (male) parts, the muscular sac of the accessory penial gland is less than 15 mm long. The hollow spine of the accessory penial gland is narrow, elongated, and straight or slightly curved, and its shape (including at its tip) varies between individuals. Its length ranges from 1.8 mm ([696-3] UF 352288) to 2.3 mm ([696-4 H] UF 352288). Its diameter at the conical base ranges from 240 to 300 μm. Its diameter at the tip ranges from 115 to 150 μm. The retractor muscle is shorter or longer than the penial sheath and inserts near the heart. Inside the penial sheath, the penis is a narrow, elongated, soft, hollow tube. Its distal end bears conical hooks which are less than 35 μm long.

Diagnostic features

(Table 4 ). Peronia okinawensis is characterized by a unique combination of anatomical traits: muscular sac shorter than 15 mm, intestinal loops of type I (with a transitional loop oriented between 12 and 3 o’clock), retractor muscle inserting near the heart.

Remarks.

A new species name is needed because no existing name applies to the species described here. The specimen [696-2] was tentatively identified as Peronia cf. verruculata by Dayrat et al. (2011). This identification should be disregarded because the specimen [696-2] belongs to the species described here (Figs 2 - 4 ). Peronia okinawensis is one of the four Peronia species in Japanese waters (Fig. 6 ). For a comparison of their geographic range, see remarks on P. setoensis . For their identification, see the identification key as well as Table 4 . It is possible that P. okinawensis is not strictly endemic to Okinawa.

Figures

Figure 2. Phylogenetic relationships between Peronia species based on concatenated mitochondrial COI and 16 S DNA sequences. Numbers by the branches are the bootstrap values (maximum likelihood analysis) and the posterior probabilities (Bayesian analysis). Only the values> 50 % (ML) and> 0.9 (Bayesian) are indicated. Numbers for each individual correspond to unique identifiers for DNA extraction. Information on specimens can be found in the lists of material examined and in Table 2. The color used for each species or mitochondrial unit is the same as the color used in Figs 3 - 6.

Figure 4. Maximum parsimony consensus tree within Peronia based on concatenated nuclear ITS 2 and 28 S sequences. Numbers by the branches are the bootstrap values. Only the values> 50 % are indicated. Numbers for each individual correspond to unique identifiers for DNA extraction. Information on specimens can be found in the lists of material examined and in Table 2. The color used for each species or mitochondrial unit is the same as the color used in Figs 2, 3, 5, 6.

Figure 6. Geographical distribution of the Peronia species A distribution of all Peronia species except for P. peronii B distribution of P. peronii. The colors are the same as those used in Figs 2 - 5. Colored areas correspond to hypothetical geographical ranges based on confirmed records only. Distinct colors are used for each unit of P. verruculata. The distribution of P. verruculata in the Indo-West Pacific is actually continuous. However, because it is unclear which units are present in regions from where we have no fresh material of P. verruculata (red areas), no unit of P. verruculata is shown there. For P. peronii, black dots correspond to material identified based on anatomical characters and blue dots correspond to material with DNA sequences. Details on species distribution can be found in each species description.

Figure 17. Peronia okinawensis, Japan, Okinawa, holotype [696 - 4 H] (UF 352288) A digestive system, dorsal view, the arrow indicates the orientation of the transitional loop B posterior, hermaphroditic (female) reproductive system C anterior, male, copulatory apparatus. Scale bars: 3 mm (A-C). Abbreviations: ag accessory penial gland, dd deferent duct, ddg dorsal digestive gland, fgm female gland mass, hg hermaphroditic gland, i intestine, ms muscular sac, ov oviduct, pdg posterior digestive gland, ps penial sheath, rm retractor muscle, rs receptaculum seminis, sp spermatheca, st stomach, v vestibule.

Figure 18. Radula, Peronia okinawensis, Japan, Okinawa A, B holotype [696 - 4 H] (UF 352288) C-F [696 - 2] (UF 352288) A left half rows of teeth B rachidian and innermost lateral teeth C rachidian and innermost lateral teeth D rachidian and lateral teeth E lateral teeth F outermost lateral teeth. Scale bars: 200 μm (A), 80 μm (B), 20 μm (C, F), 60 μm (D), 100 μm (E).

Figure 19. Penial hooks, Peronia okinawensis, Japan, Okinawa A, B holotype [696 - 4] (UF 352288) C, D [696 - 3] (UF 352288). Scale bars: 4 μm (A, C, D), 2 μm (B).

Figure 20. Accessory penial gland spine, Peronia okinawensis, Japan, Okinawa A holotype [696 - 4] (UF 352288) B [696 - 3] (UF 352288) C [696 - 2] (UF 352288) D same as A; E same as B; F same as C. Scale bars: 400 μm (A-C), 40 μm (D-F).