Peronia griffithsi 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 griffithsi Dayrat & Goulding sp. nov. Figs 39 , 40 , 41 , 42 , 43 , 44 , 45 , 46 , 47 , 48

Type material.

Holotype. Mauritius • holotype, hereby designated, 15/10 mm [3157 H]; Mahebourg, waterfront; 20°24.317'S, 57°42.605'E; 13 Jun 2014; TC Goulding leg.; st 178, rocky intertidal, with algae, just before sunrise; MNHN-IM-2000-35265.

Additional material examined.

Mauritius • 7 specimens 8/5 mm [3606], 20/15 mm [3153], 22/17 mm [3154], 17/15 mm [3155], 20/14 mm [3156], 7/4 mm [3607], and 6/4 mm [3608]; same collection data as for the holotype; MNHN-IM-2019-1608.

Indonesia • 1 specimen 17/12 mm [2936]; Kei Islands, Fiditan; 05°35.957'S, 132°45.112'E; 28 Feb 2014; M Khalil and field party leg.; st 144, rocks behind muddy Rhizophora mangrove; UMIZ 00176. • 2 specimens 18/10 mm [2934] and 25/16 mm [3566]; same collection data as for the preceding; UMIZ 00177.

Papua New Guinea • 1 specimen 6/3 mm [6095]; New Ireland, east coast, Povalval; 02°41'S, 150°57'E; 11 & 13 Jun 2014; MNHN Expedition Kavieng 2014 leg.; st KM05, mixed hard platform and seagrass bed at outlet of rivulet; MNHN-IM-2013-53535.

Additional material examined

(historical museum collections). Indonesia • 161 specimens from 2/2 to 23/14 mm; Kei Islands, Toeal; 18 Mar 1922; T Mortensen leg.; NHMD 635303.

Distribution

(Fig. 6 ). Indo-West Pacific: Mauritius (type locality), Indonesia (Kei Islands), and Papua New Guinea (New Ireland).

Etymology.

Peronia griffithsi is named after Owen Griffiths, who kindly and generously hosted and guided one of us (Tricia Goulding) in Mauritius.

Habitat

(Fig. 39 ). Peronia griffithsi is found in the rocky intertidal, like most other Peronia slugs. Our specimens from Mauritius were collected just before sunrise, suggesting that P. griffithsi is, at least partly, a nocturnal species.

Color and morphology of live animals

(Figs 40 , 41 ). No picture of live animals was available for specimens from Kavieng. The description of the color of live animals is based on Mauritius and Kei individuals. The dorsal notum is greenish brown, light to dark, mottled with darker and lighter areas. The color of the dorsal papillae varies as that of the background itself, but dorsal papillae can also be yellowish-greenish. The ventral surface (foot and hyponotum) varies from whitish to yellowish and can change rapidly in any given individual. The ocular tentacles are brown-grey, like the head. 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 (from 6 to 10). The largest specimens are 25 mm long.

Digestive system

(Figs 42 - 44 ). Examples of radular formulae are presented in Table 5 . The median cusp of the rachidian teeth is approximately 35 μm long. The hook of the lateral teeth is approximately 70 μm long. The intestinal loops are of type V.

Reproductive system

(Figs 45 - 48 ). In the anterior (male) parts, the muscular sac of the accessory penial gland is less than 5 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 is 0.62 mm ([2934] UMIZ 00177) in unit Kei and ranges from 0.5 mm ([3157 H] MNHN-IM-2000-35265) to 0.61 mm ([3153] MNHN-IM-2019-1608) in Mauritius. Its diameter at the conical base ranges from 60 to 65 μm. Its diameter at the tip ranges from 15 to 20 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 25 μm long.

Diagnostic features

(Table 4 ). Peronia griffithsi is characterized by a unique combination of anatomical traits: intestinal loops of type V, muscular sac of the accessory penial gland less than 5 mm long, spine of the accessory penial gland less than 0.62 mm long. In P. platei and P. setoensis , which are anatomically similar to P. griffithsi , the spine of the accessory penial gland is longer than 0.7 mm ( P. platei ) and 0.9 mm ( P. setoensis ).

Remarks.

A new species name is needed because no existing name applies to the species described here. A large population (161 specimens) from Kei Islands and identified by Hoffmann as Onchidium verruculatum was found in the collections of the Copenhagen Museum (NHMD 635303). Those specimens most likely belong to P. griffithsi because their intestinal loops are of type V (only a few individuals were dissected). Also, the retractor muscle of the few individuals dissected inserts near the end of the visceral cavity, as in specimens from Mauritius, suggesting that an insertion near the heart is not as common. Interestingly, Hoffmann (1928: 44) did not include those specimens in his list of material for O. verruculatum , possibly because he realized that they were different from O. verruculatum , with intestinal loops of type I.

Figures

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 39. Habitats, Peronia griffithsi A Indonesia, Kei Islands, rocks behind muddy Rhizophora mangrove (st 144) B Papua New Guinea, New Ireland, mixed hard platform and seagrass bed at outlet of rivulet (st KM 05).

Figure 40. Live animals, Peronia griffithsi, Mauritius A dorsal view, 20 mm long [3153] (MNHN-IM- 2019 - 1608) B dorsal view, 17 mm long [3155] (MNHN-IM- 2019 - 1608) C dorsal view, 8 mm long [3606] (MNHN-IM- 2019 - 1608) D holotype, ventral view, 15 mm long [3157 H] (MNHN-IM- 2000 - 35265) E ventral view, 22 mm long [3154] (MNHN-IM- 2019 - 1608).

Figure 41. Live animals, Peronia griffithsi, Indonesia, Kei Islands A dorsal view, 18 mm long [2934] (UMIZ 00177) B dorsal view, 17 mm long [2936] (UMIZ 00176) C dorsal view, 25 mm long [3566] (UMIZ 00177) D ventral view, same as A.

Figure 42. Digestive system, dorsal view, Peronia griffithsi, with intestinal loops of type V A holotype, Mauritius [3157 H] (MNHN-IM- 2000 - 35265) B Mauritius [3153] (MNHN-IM- 2019 - 1608) C Indonesia, Kei Islands [2936] (UMIZ 00176). Scale bars: 2 mm (A-C). Abbreviations: ddg dorsal digestive gland, i intestine, pdg posterior digestive gland, st stomach.

Figure 43. Radula, Peronia griffithsi, Indonesia, Kei Islands, [3566] (UMIZ 00177) A rachidian and innermost lateral teeth B rachidian and lateral teeth C lateral teeth D outermost lateral teeth. Scale bars: 20 μm (A), 30 μm (B), 40 μm (C), 10 μm (D).

Figure 44. Radula, Peronia griffithsi, Mauritius A holotype [3157 H] (MNHN-IM- 2000 - 35265) B-D [3153] (MNHN-IM- 2019 - 1608) A right half rows of teeth B rachidian and lateral teeth C lateral teeth D outermost lateral teeth. Scale bars: 100 μm (A), 10 μm (B, D), 60 μm (D).

Figure 45. Posterior, hermaphroditic (female) reproductive system, Peronia griffithsi A holotype, Mauritius [3157 H] (MNHN-IM- 2000 - 35265) B Indonesia, Kei Islands [2936] (UMIZ 00176). Scale bars: 1 mm (A), 2 mm (B). Abbreviations: dd deferent duct, fgm female gland mass, hg hermaphroditic gland, ov oviduct, rs receptaculum seminis, sp spermatheca.

Figure 46. Anterior, male, copulatory apparatus, Peronia griffithsi A holotype, Mauritius [3157 H] (MNHN-IM- 2000 - 35265) B Indonesia, Kei Islands [2936] (UMIZ 00176). Scale bars: 1 mm (A, B). Abbreviations: ag accessory penial gland, dd deferent duct, ms muscular sac, ps penial sheath, rm retractor muscle, v vestibule.

Figure 47. Penis and penial hooks, Peronia griffithsi A-D Indonesia, Kei Islands [2936] (UMIZ 00176) E, G holotype, Mauritius [3157 H] (MNHN-IM- 2000 - 35265) F Mauritius [3156] (MNHN-IM- 2019 - 1608) H [3153] (MNHN-IM- 2019 - 1608). Scale bars: 3 μm (A), 2 μm (B, H), 20 μm (C, F), 10 μm (D), 40 μm (E), 4 μm (G).

Figure 48. Accessory penial gland spine, Peronia griffithsi A holotype, Mauritius [3157 H] (MNHN-IM- 2000 - 35265) B Mauritius [3153] (MNHN-IM- 2019 - 1608) C Indonesia, Kei [2934] (UMIZ 00177) D same as A; E Mauritius [3156] (MNHN-IM- 2019 - 1608) F same as C. Scale bars: 100 μm (A-C), 5 μm (D-F).