Platevindex coriaceus darwinensis Goulding & Dayrat, 2021

Goulding, Tricia C., Bourke, Adam J., Comendador, Joseph, Khalil, Munawar, Quang, Ngo Xuan, Tan, Shau Hwai, Tan, Siong Kiat & Dayrat, Benoît, 2021, Systematic revision of Platevindex Baker, 1938 (Gastropoda: Euthyneura: Onchidiidae), European Journal of Taxonomy 737 (1), pp. 1-133 : 56-60

Platevindex coriaceus darwinensis Goulding & Dayrat subsp. nov.

urn:lsid:zoobank.org:act:A609EB85-101E-467E-AFD5-812043EDAFFE

Figs 16B , 18D , 19D , 22–25

Etymology

Platevindex coriaceus darwinensis subsp. nov. is named after Darwin, Northern Territory, Australia, which is the type locality.

Material examined

Type material

AUSTRALIA • holotype (28/26 [1700] mm); Northern Territory, Darwin , close to Tiger Brenan Rd; 12°28.782′ S, 130°54.750′ E; 19 Aug. 2012; station 69; high tidal Ceriops mangrove by small service road; NTM P.57601 .

Other material

AUSTRALIA – Northern Territory • 3 specs (40/25 [1674], 29/21 [1663] and 20/14 [1672] mm); Darwin , Talc Head ; 12°28.765′ S, 130°46.297′ E; 15 Aug. 2012; station 62; open forest of large Sonneratia alba with mud saturated with water; NTM P.57602 • 1 spec. (29/16 [1677] mm); Darwin , Near Berrimah; 12°28.786′ S, 130°54.750′ E; 16 Aug. 2012; station 63; Sonneratia , Rhizophora and Ceriops mangrove forest; NTM P.57603 • 1 spec. (32/17 [1633] mm); Darwin , near Channel Island Rd; 12°33.557′ S, 130°52.889′ E; 16 Aug. 2012; station 64; Sonneratia , Rhizophora and Ceriops mangrove forest; NTM P.57604 • 1 spec. (27/19 [1690] mm); Darwin , end of Channel Island Rd; 12°33.557′ S, 130°52.894′ E; 17 Aug. 2012; station 66; Sonneratia , Rhizophora and Ceriops mangrove forest; NTM P.57606 • 1 spec. (33/25 [1701] mm); Darwin , close to Tiger Brenan Rd; 12°28.782′ S, 130°54.750′ E; 19 Aug. 2012; station 69; high tidal Ceriops mangrove by small service road; NTM P.57608 . Queensland • 1 spec. (31/26 [2549] mm); Cairns; 16°52.972′ S, 145°45.665′ E; 15 Jun. 2013; station 98; Rhizophora , Bruguiera and Ceriops , not many dead logs; MTQ • 1 spec. (50/27 [no DNA] mm); Flying Fish Point ; 17°30.001′ S, 146°04.295′ E; 20 Jun. 2013; station 104; mangrove by creek with sandy mud; MTQ • 1 spec. (24/18 [2590] mm); Magnetic Island ; 19°10.096′ S, 146°49.366′ E; 23 Jun. 2013; station 106; mostly Avicennia mangrove with mounds of mud; MTQ • 1 spec. (34/25 [2679] mm); Campwin Beach; 21°22.455′ S, 149°18.753′ E; 5 Jul. 2013; station 121; narrow Rhizophora mangrove with watery mud and large rocks by creek; MTQ • 2 specs (48/34 [no DNA] and 23/17 [2689] mm); Armstrong Beach; 21°27.129′ S, 149°17.084′ E; 6 Jul. 2013; station 123; margin of Rhizophora and Avicennia mangrove with open mudflat; MTQ • 1 spec. (48/29 [no DNA] mm); Queensland, Pioneer River; 21°08.511′ S, 149°12.076′ E; 8 Jul. 2013; station 125; Avicennia & Rhizophora mangrove; MTQ.

INDONESIA – Halmahera • 2 specs (36/24 [5071] and 28/18 [5021] mm); Dodinga ; 00°51.348′ N, 127°38.504′ E; 9 Mar. 2015; station 206; high intertidal back of mangrove with Acrostichum sp. and mounds of mud; UMIZ 00080 • 4 specs (34/19 [5112], 34/18 [5109], 22/17 [5111] and 19/13 [5110] mm); Buli ; 00°55.446′ N, 128°20.612′ E; 16 Mar. 2015; station 212; logged area in front of old Rhizophora forest; UMIZ 00081 .

Other museum material without DNA sequences

AUSTRALIA – Western Australia • 13 specs (from 35/30 to 20/ 20 mm); Kimberley, Whirlpool Pass ; 16°15. 81′ S, 123°29.88′ E; on mangroves; WAM S42812 • 6 specs (from 25/25 to 17/ 15 mm); Kimberley, Cambridge Gulf, Cape Domett ; 14°49.78′ S, 128°23.20′ E; WAM S26581 • 4 specs (from 35/30 to 15/ 15 mm); Exmouth Gulf, Tubridgi Point Boat Channel ; 21°50.0′ S, 114°39.90′ E; WAM S26772 • 5 specs (from 30/30 to 8/ 8 mm); Exmouth Gulf , NE of Tent Point; 22°00.0′ S, 114°30.5′ E to 22°00.4′ S, 114°32.1′ E; WAM S26777 .

Description

Color and morphology of live animals ( Fig. 22 )

Identical to P. coriaceus coriaceus (see above), acknowledging some minor variations: the hyponotum is grey or light grey; the foot is light yellow; there are between 20 and 36 papillae with dorsal eyes, the largest animals bearing the largest numbers of eyes.

Digestive system ( Figs 17B , 23 )

Identical to that of P. coriaceus coriaceus (see above), acknowledging some minor variations: radulae measure up to 7.4 mm; examples of radular formulae are presented in Table 5 ; intestinal loops are of type II, with a transitional loop oriented between 6 and 8 o’clock ( Fig. 17B ).

Reproductive system ( Figs 18–19 , 24 )

Identical to that of P. coriaceus coriaceus (see above), acknowledging some minor variations: the distal section of the oviduct (i.e., distal to the spermatheca) is long, up to two times the length of the proximal section (from the female gland mass to the spermatheca); the oviduct is much wider (up to five times) than the deferent duct; penial hooks measure from 60 to 110 μm; the flexible region of the penis with hooks is between 2 and 8 mm long ( Fig. 24 ); the retractor muscle varies from the length of the sheath to ¼ of its length.

Distinctive diagnostic features ( Table 4 )

Platevindex coriaceus coriaceus and P. coriaceus darwinensis subsp. nov. are indistinguishable externally.The only minor difference in color variation is that a dark blue-grey hyponotum was observed in P. coriaceus coriaceus (most commonly in the Philippines) but never in P. coriaceus darwinensis subsp. nov. Internally, both subspecies can hardly be distinguished either. The ratio between the oviduct width and the deferent duct width tends to be much higher in P. coriaceus darwinensis subsp. nov. than in P. coriaceus coriaceus , but a higher variation may be discovered in the future. However, based on current data, P. coriaceus coriaceus and P. coriaceus darwinensis subsp. nov. do not overlap geographically.

Distribution ( Fig. 10B )

Australia: Northern Territory and Queensland. Indonesia: Halmahera.

Habitat ( Fig. 25 )

Platevindex coriaceus darwinensis subsp. nov. is found in the same habitat as the nominotypical subspecies, i.e., mangrove forests, on tree roots, tree trunks and logs. It is very common in the Northern Territory ( Australia) and Halmahera ( Indonesia). It seems to be less common in Queensland ( Australia), with Platevindex luteus found in higher abundance.

Remarks

A new subspecific name is needed because no existing species-group name could apply with confidence to the taxon recognized here. Platevindex cinereus was described from Broome, Western Australia, by Odhner (1917) as Oncis cinerea , exclusively known from the holotype, by monotypy, which is a small (9/ 9 mm) and immature specimen (SMNH 945). There is no doubt that the holotype of Oncis cinerea belongs to a species of Platevindex , but, because it is immature, it is not possible to determine which one. Platevindex cinereus could apply to either of the two species sampled in the Northern Territory, Australia, P. coriaceus darwinensis subsp. nov. or P. martensi , and even to the widespread species P. luteus , although the latter has not been recorded from Northern Territory or Western Australia. Because it will remain impossible to confidently apply P. cinereus to any particular species of Platevindex , it is regarded here as a nomen dubium. Some onchidiid slugs from the collections of the Western Australia Museum are identified here as P. coriaceus based on the position of their dorsal eyes and their reproductive anatomy. Whether populations of P. coriaceus from Western Australia belong to P. coriaceus coriaceus , P. coriaceus darwinensis subsp. nov., or even a distinct subspecies would have to be checked with fresh material from Western Australia.

Bretnall’s (1919: 323) description of Onchidium coriaceum from Queensland does not appear to be based on Platevindex slugs: “short conical papillae” and a hyponotum “regularly yellowish” are not compatible with P. coriaceus darwinensis subsp. nov.

Figures

Fig. 16. Platevindex coriaceus (Semper, 1880), digestive system. A. Dorsal view of intestinal loops of type II, with a transitional loop oriented at 9 o’clock, Platevindex coriaceus coriaceus unit #1, Vietnam [5629] (ITBZC IM 00014). B. Dorsal view with no digestive glands, type II, with a transitional loop oriented at 7 o’clock, Platevindex coriaceus darwinensis Goulding & Dayrat subsp. nov., Northern Territory, Australia [1663] (NTM P.57602). Abbreviations: ddg = dorsal digestive gland; i = intestine; oddg = opening of the dorsal lobe of the digestive gland; opdg = opening of the posterior lobe of the digestive gland; pdg = posterior digestive gland; rg = rectal gland; st = stomach. Scale bars = 3 mm.

Fig. 18. Platevindex coriaceus (Semper, 1880), posterior reproductive system. A. Platevindex coriaceus coriaceus unit #2, Philippines, lectotype (ZMB/Moll 39028a). B. Platevindex coriaceus coriaceus unit #2, Bohol, Philippines [3356] (PNM 041240). C. Platevindex coriaceus coriaceus unit #1, Vietnam [5629] (ITBZC IM 00014). D. Platevindex coriaceus darwinensis Goulding & Dayrat subsp. nov., Northern Territory, Australia [1690] (NTM P.57606). Abbreviations: dd = deferent duct; fgm = female gland mass; hd = hermaphroditic duct; hg = hermaphroditic gland; ov = oviduct; rs = receptaculum seminis; sp = spermatheca. Scale bars = 2 mm.

Fig. 19. Platevindex coriaceus (Semper, 1880), anterior, male copulatory apparatus. A. Platevindex coriaceus coriaceus unit #2, Bohol, Philippines [3356] (PNM 041240). B. Penis (extracted from the penial sheath), same as A. C. Platevindex coriaceus coriaceus unit #1, Vietnam [5629] (ITBZC IM 00014). D. Platevindex coriaceus darwinensis Goulding & Dayrat subsp. nov., Northern Territory, Australia [1663] (NTM P.57602). Abbreviations: dd = deferent duct; p = penis; ps = penial sheath; rm = retractor muscle; v = vestibule. Scale bars: A, C–D = 3 mm; B = 2 mm.

Fig. 22. Platevindex coriaceus darwinensis Goulding & Dayrat subsp. nov., live animals. A. Dorsal view, 20 mm long [1672], Australia, Darwin (NTM P.57602). B. Dorsal view, 36 mm long [5071], Indonesia, Halmahera (UMIZ 00080). C. Dorsal view, 36 mm long [1674], Australia, Darwin (NTM P.57602). D. Dorsal view, 34 mm long [5109], Indonesia, Halmahera (UMIZ 00081). E. Dorsal view, holotype, 28 mm long [1700], Australia, Darwin (NTM P.57601). F. Dorsal view, 22 mm long [5111], Indonesia, Halmahera (UMIZ 00081). G. Ventral view, 33 mm long [1701], Australia, Darwin. H. Ventral view, same as B. I. Ventral view, same as C.

Fig. 23. Platevindex coriaceus darwinensis Goulding & Dayrat subsp. nov., radula, Indonesia, Halmahera [5021] (UMIZ 00080). A. Rachidian and innermost lateral teeth. B. Lateral teeth with rachidian teeth. C. Lateral teeth. D. Outermost lateral teeth. Scale bars: A = 50 μm; B = 10 μm; C = 100 μm; D = 30 μm.

Fig. 24. Platevindex coriaceus darwinensis Goulding & Dayrat subsp. nov., penial hooks, Australia, Queensland, [no DNA] (MTQ). Scale bar = 100 μm.

Fig. 25. Habitats of Platevindex coriaceus darwinensis Goulding & Dayrat subsp. nov. A. Australia, Darwin, large Sonneratia alba, open forest, soft mud by shore (station 62). B. Australia, Queensland, Rhizophora, Bruguiera and Ceriops by boardwalk, not many dead logs (station 98). C. Australia, Queensland, open forest with Avicennia, some Rhizophora and soft mud (station 124). D. Indonesia, Halmahera, high intertidal back of a mangrove, with Acrostichum ferns and mounds of mud (station 206).

Fig. 17. Platevindex coriaceus coriaceus (Semper, 1880) unit #2, digestive system, dorsal view, intestinal loops of type II. A. Transitional loop oriented at 9 o’clock, Luzon, Philippines [3170] (PNM 041236). B. Transitional loop oriented at 7 o’clock, Bohol, Philippines [3256] (PNM 041238). Abbreviations: ddg = dorsal digestive gland; i = intestine; pdg = posterior digestive gland; rg = rectal gland; st = stomach. Scale bars = 2 mm.

Fig. 10. Geographic distributions of species of Platevindex. Colored areas correspond to hypothetical ranges proposed based on all known records, and the colors are the same as those used for each species in the phylogenetic trees (Figs 1–5). Distinct colors are used for each subspecies and mitochondrial unit in P. coriaceus (Semper, 1880) as well as for each subspecies of P. burnupi (Collinge, 1902). Black dots show sites sampled for this study and red dots (China and Japan) show localities of previously published genetic sequences included in the phylogenetic analyses. A. Platevindex luteus (Semper, 1880), P. applanatus (Simroth, 1920), P. burnupi. B. Platevindex tigrinus (Stoliczka, 1869), P. coriaceus coriaceus (units #1, #2, and #3) and P. coriaceus darwinensis subsp. nov. C. Platevindex martensi (Plate, 1893), P. aptei Goulding & Dayrat sp. nov., P. amboinae (Plate, 1893) and P. latus (Plate, 1893).