Platevindex luteus Goulding & Bourke & Comendador & Khalil & Quang & Tan & Tan & Dayrat 2021
Creators: name: Goulding, Tricia C.
name: Bourke, Adam J.
name: Comendador, Joseph
name: Khalil, Munawar
name: Quang, Ngo Xuan
name: Tan, Shau Hwai
name: Tan, Siong Kiat
name: Dayrat, Benoît
Publisher: name: Zenodo
Year: 2021
Subjects: Biodiversity
Taxonomy
Animalia
Mollusca
Gastropoda
Systellommatophora
Onchidiidae
Platevindex
Platevindex luteus

description: Platevindex luteus (Semper, 1880)
Figs 31–35
Onchidium luteum Semper, 1880: pl. 20, fig. 10, pl. 23, figs 2, 6.
Oncis schneideri Hoffmann, 1932: 135–137, fig. 1. Syn. nov.
Onchidium luteum – Semper 1882: 274–275, pl. 21, fig. 6. — Plate 1893: 181.
Oncis lutea – Stantschinsky 1907: 395. — Hoffmann 1928: 89–90.
Platevindex luteus – Dayrat 2009: 5. — Goulding et al. 2018a: 340; 2018b: 12; 2018c: 807. — Dayrat et al. 2019a: 6; 2019b: 38; 2019c: 560; 2019d: 30.
Material examined
Lectotype (here designated) SINGAPORE • lectotype (14/ 11 mm); 1858; Semper leg.; ZMB/Moll 39031a.
Paralectotypes SINGAPORE • 3 paralectotypes (15/11, 13/11 and 12/ 12 mm); 1858; Semper leg.; ZMB/Moll 39031b.
Holotype of Oncis schneideri PAPUA NEW GUINEA • holotype (7/ 5 mm) by monotypy; Ostk̹ste von Neu-Pommern [east coast of New Britain]; ZMB/Moll 114152.
Notes on type material Onchidium luteum. The lectotype was selected because the male parts are present (although they were previously detached from the specimen). The posterior part of the lectotype is missing and the digestive system is not well preserved. The three paralectotypes were also previously dissected: the internal organs are missing in the two largest ones; the third and smallest paralectotype was cut longitudinally
in two halves and is largely destroyed. Semper listed five syntypes, suggesting that one of the original syntypes is missing.
Oncis schneideri. The holotype was previously dissected. The penial complex was drawn by Hoffmann and likely destroyed by him (it is missing), and the insertion of the retractor muscle cannot be checked. Some parts of the female (posterior) reproductive system are inside the holotype, but are largely destroyed. The digestive system is largely destroyed; the radula is present but the intestine is missing and the intestinal type cannot be verified.
Other material AUSTRALIA – Queensland • 1 spec. (17/ 14 mm [2551]); Cairns; 16°52.972′ S, 145°45.665′ E; 15 Jun. 2013; station 98; Rhizophora, Bruguiera and Ceriops mangrove; MTQ • 1 spec. (22/ 16 mm [2597]); Magnetic Island; 19°09.733′ S, 146°48.625′ E; 24 Jun. 2013; station 108; dead log over pool of water in mangrove; MTQ • 1 spec. (20/ 14 mm [2678]); Armstrong Beach; 21°27.129′ S, 149°17.084′ E; 5 Jul. 2013; station 120; margins of mangrove and mudflat with Rhizophora and Avicennia; MTQ.
BRUNEI • 1 spec. (16/ 14 mm [1039]); Pulau Kaingara; 04°57.020′ N, 115°01.785′ E; 28 Jul. 2011; station 33; open mangrove with Rhizophora trees and logs, by the river; BDMNH.
INDONESIA – Sumatra • 2 specs (22/ 17 mm [1792] and 15/ 7 mm [1789]); Sungai Lubuk; 05°40.174′ S, 105°34.097′ E; 20 Oct. 2012; station 80; open mangrove with Rhizophora trees, Thalassina mounds and dead logs; UMIZ 00082. – Lombok • 1 spec. (11/ 9 mm [2958]); Seriwe Bay; 08°51.960′ S, 116°32.838′ E; 25 Mar. 2014; station 146; Avicennia mangrove with hard mud and rocks; UMIZ 00094. – Bali • 3specs (19/ 16mm [3046],18/ 13mm [3040]and14/ 12mm [3044]); Denpasar; 08°47.435′S, 115°13.197′E; 1 Apr. 2014; station 153; large mangrove by road, very soft mud; UMIZ 00095. – Sulawesi • 1 spec. (17/ 14 mm [2335]); Makassar City, Tallo; 05°06.117′ S, 119°26.777′ E; 21 Mar. 2013; station 92; small mangrove with outhouse in center; UMIZ 00191 • 1 spec. (23/ 16 mm [2364]); same locality as for preceding but 26 Mar. 2013; station 95; small mangrove with outhouse in center; UMIZ 00086. – Ambon • 1 spec. (28/ 18 mm [2837]); Lateri; 03°38.237′ S, 128°14.783′ E; 14 Feb. 2014; station 131; muddy mangrove with Rhizophora; UMIZ 00089 • 1 spec. (17/ 10 mm [2858]); Lateri; 03°38.261′ S, 128°14.716′ E; 16 Feb. 2014; station 133; low intertidal mangrove, slugs on mangrove trees underneath bark; UMIZ 00188. – Seram • 1 spec. (23/ 20 mm [2886]); Piru; 03°04.072′ S, 128°11.362′ E; 19 Feb. 2014; station 136; beach of palms and Acrostichum ferns behind Sonneratia mangrove; UMIZ 00189. – Kei Islands • 1 spec. (14/ 9 mm [2906]); Un; 05°38.273′ S, 132°45.738′ E; 25 Feb. 2014; station 140; in back of mangrove on rocks, mud, inside logs and under leaf litter; UMIZ 00091 • 2 specs (18/ 10 mm [2915] and 17/ 11 mm [2916]); Un; 05°38.282′ S, 132°45.669′ E; 26 Feb. 2014; station 141; Bruguiera and Rhizophora mangrove, slugs under the bark; UMIZ 00092 • 1 spec. (18/ 12 mm [2922]); Ohoi Ibra; 05°46.216′ S, 132°46.116′ E; 27 Feb. 2014; station 142; some old trees, others replanted, mud very soft; UMIZ 00093. – Ternate • 1 spec. (9/ 6 mm [5051]); Bastiong; 00°46.407′ N, 127°22.760′ E; 7 Mar. 2015; station 203; small mangrove patch and some rocks nearby a harbor; UMIZ 00097. – Halmahera • 1 spec. (17/ 12 mm [5022]); Dodinga; 00°51.348′ N, 127°38.504′ E; 9 Mar. 2015; station 206; back of a mangrove, high intertidal with Acrostichum ferns and mounds of mud; UMIZ 00098 • 1 spec. (17/ 15 mm [5041]); Saolat; 00°53.435′ N, 127°56.475′ E; 12 Mar. 2015; station 209; open Rhizophora mangrove with soft dark mud, many dead logs; UMIZ 00099. – Timor • 1 spec. (17/ 12 mm [5939]); Tablolong; 10°18.895′ S, 123°28.774′ E; 17 Jul. 2016; station 255; mangrove patch with very dark mud by a village; UMIZ 00190.
NEW CALEDONIA • 1 spec. (9/ 8 mm [6344]); Upper Diahot River; 20°20.564′ S, 164°21.842′ E; 6 Sep. 2018; Our Planet Reviewed Koumac 2018 expedition leg.; station KM505; lower, wet (and dry) trunks and roots of trees in a forest of Rhizophora apiculata and Xylocarpus granatum with a patchy understory of Acrostium fern; MNHN-IM-2019-1474 • 1 spec. (12/ 8 mm [6361]); Diahot River; 20°19.435′ S, 164°19.195′ E; 8 Sep. 2018; Our Planet Reviewed Koumac 2018 expedition leg.; station KM510; firm sandy mud amongst prop roots in a Rhizophora stylosa forest fringing the river; MNHN-IM-2019-1475 • 1 spec. (15/ 11 mm [6367]); Hienghene, Hienghene River Bridge; 20°41.756′ S, 164°56.644′ E; 14 Sep. 2018; Our Planet Reviewed Koumac 2018 expedition leg.; station KM521; edge of Rhizophora apiculta mangrove forest near the high tide mark next to a bridge; MNHN-IM-2019-1476.
PAPUA NEW GUINEA – Madang • 1 spec. (9/ 8 mm [5429]); Meiro River, near airport; 05°12.2′ S, 145°47.4′ E; 5 Nov. 2012; MNHN expedition Papua Niugini leg.; station PM01; Nypa palm swamp; MNHN-IM-2013-10407 • 1 spec. (9/ 7 mm [5431]); South Dumduman Island; 05°00.2′ S, 145°47.6′ E; 9 Nov. 2012; MNHN expedition Papua Niugini leg.; station PM12; limestone rocky intertidal; MNHN- IM-2013-10409. – New Ireland • 1 spec. (8/ 5 mm [6101]); Kavieng, Lisinung Island; 02°40.6′ S, 150°44.4′ E; 23 Jun. 2014; MNHN expedition Kavieng 2014 leg.; station KM60; platform with seagrass and mangrove; MNHN-IM-2013-55235 • 1 spec. (8/ 5 mm [6102]); same collection data as for preceding; MNHN-IM-2013-55239.
PHILIPPINES – Luzon • 1 spec. (10/ 9 mm [3198]); Batangas, Calantagan; 13°55.319′ N, 120°37.260′ E; 7 Jul. 2014; station 183; open forest with mix of Avicennia and Rhizophora, sandy and muddy areas; PNM 041242 • 2 specs (13/ 10 mm [3224] and 11/ 7 mm [3225]); Batangas, Calantagan; 13°53.278′ N, 120°37.124′ E; 8 Jul. 2014; station 184; very narrow forest on the shore, mixed Avicennia and young Rhizophora; PNM 041243. – Bohol • 2 specs (19/ 14 mm [3281] and 15/ 8 mm [3280]); Maribojoc; 09°43.806′ N, 123°51.234′ E; 15 Jul. 2014; station 192; pier at the beginning of Sabima boardwalk; PNM 041244 • 1 spec. (22/ 14 mm [3367]); Mabini; 09°51.402′ N, 124°30.982′ E; 18 Jul. 2014; station 195; narrow Rhizophora and Avicennia mangrove by the sea with fish ponds built on landward side, cement ditches between the mangrove patches and the ponds; PNM 041246 • 1 spec. (22/ 12 mm [3428]); Maribojoc; 09°44.280′ N, 123°49.389′ E; 20 Jul. 2014; station 202; uplifted, dead coral flat covered with sand and algae, near Sonneratia trees; PNM 041248.
SINGAPORE • 1 spec. (14/ 11 mm [1000]); Mandai; 01°26.237′ N, 103°45.730′ E; 1 Apr. 2010; station 6; followed river in the mangrove from railroad towards sea; ZRC.MOL.10476 • 1 spec. mm (12/8 [997]); Semakao Island; 01°12.083′ N, 103°45.585′ E; 3 Apr. 2010; station 8; artificial landfill island with low and very dense newly-planted Rhizophora trees, muddy areas in between Rhizophora patches and coral rubble close to the shore; ZRC.MOL.10477.
VIETNAM • 2 specs (18/ 13 mm [5668] and 14/ 11 mm [5613]); Can Gio mangrove forest; 10°24.157′ N, 106°53.950′ E; 19 Jul. 2015; station 233; rocks and gravel on side of Avicennia and Rhizophora mangrove; ITBZC IM 00016.
Description
Color and morphology of live animals (Fig. 31) The dorsal notum of live animals may be covered by dry mud (especially when found underneath logs and rocks). The notum is bumpy with prominent, distinctly-raised papillae (with or without dorsal eyes). Individuals are flattened but often become almost hemispherical when disturbed. The dorsal color is typically brown, dark brown or nearly black, and occasionally yellowish-brown. The hyponotum color varies greatly: it may be dark blue, medium grey, white or variants in between. Papillae with dorsal eyes are present, many of which are distinctly raised. The exact number of papillae bearing dorsal eyes is difficult to determine as papillae may be retracted, but is usually between 10 and 22, although up to 35 dorsal eyes have been observed. Papillae bear only one dorsal eye. Dorsal eyes may be distributed across the entire notum or only in the middle but are absent from the margin (eyes are never <2 mm from the notum edge).
Digestive system (Figs 1B, 1D, 2E, 32, 33 A–E)
Radulae measure up to 3.7 mm in length. Examples of radular formulae are presented in Table 5. The intestinal loops are of type I, with a transitional loop oriented between 3 and 6 o’clock, and of type II, with a transitional loop oriented between 6 and 8 o’clock (Figs 1B, 1D, 2E, 32).
Reproductive system (Figs 33F, 34)
In the posterior part of the reproductive system, the oviduct is approximately twice as wide as the deferent duct. Its distal section (distal to the spermatheca) is shorter or equal to its proximal section. The deferent duct is not attached or only loosely attached to the oviduct, and generally loosely coiled (not with many tight, U-shaped loops), but individuals with a highly-coiled deferent duct exceptionally do exist. The position of the female pore varies from very close to the anus (<1 mm) up to 3 mm away from the anus. The flexible region of the penis with hooks is approximately 1 to 1.5 mm long. Penial hooks are large, approximately 45 to 90 µm long, but between 20 to 60 µm long in smaller individuals from Mauritius. The penial hooks can be seen inside the semi-transparent penis. The posterior retractor muscle inserts near the heart on the right side of the visceral cavity. Its length varies from being half the length of the penial sheath to three times as long. The deferent duct is not particularly long or convoluted, displaying only a few loose loops (it is even less convoluted in immature specimens).
Distinctive diagnostic features (Table 4)
The yellow foot of Platevindex luteus easily distinguishes it from P. martensi (black foot) and P. aptei sp. nov. (orange foot). However, its hyponotum color is highly variable and does not help distinguish it from other species of Platevindex with a blue or grey hyponotum (e.g., P. coriaceus, P. burnupi and P. applanatus). Live individuals can be more hemispherical (especially when contracted) than in other species, but flattened individuals can easily be mistaken for small individuals of other species of Platevindex. Platevindex luteus reaches a smaller maximum size than other species with a similar ventral color, but the size range of all these species overlaps and cannot be used for identification. Finally, the notum of P. luteus bears prominent dorsal papillae, which are especially obvious when the animal is contracted, but these dorsal papillae are also present in P. applanatus and are thus not strictly diagnostic of P. luteus. The notum of P. burnupi is granular (i.e., not smooth), but does not bear prominent papillae, whether animals are disturbed or not.
Internally, intestinal loops help to distinguish P. luteus from P. applanatus, P. amboinae and P. latus (Table 4). The latter two species share intestinal loops of type III, while the intestine of P. luteus is of type I or II. Further, even though the intestinal loops of P. applanatus are also of type I, their transitional loop is oriented between 1 and 2 o’clock, while the transitional loop of individuals of P. luteus with a type I is oriented between 3 and 6 o’clock. Platevindex slugs with similar intestinal loops of type II can be distinguished by other means, especially the length of the region of the penis with penial hooks: P. luteus (approximately 1 mm), P. coriaceus (2–8 mm), P. martensi (2–2.5 mm) and P. aptei sp. nov. (2.5–5 mm). Note that P. amboinae and P. latus, which both completely lack penial hooks, also differ from P. luteus in that respect. In the posterior reproductive system, the deferent duct is short, usually loosely coiled and only loosely attached to the oviduct, which helps to differentiate P. luteus from P. coriaceus and P. tigrinus, in which the deferent duct is tightly coiled and attached to the oviduct. The insertion of the retractor muscle of the penis near the heart in P. luteus also clearly distinguishes it from P. coriaceus and P. aptei sp. nov., in which it inserts at the posterior end of the visceral cavity.
Finally, individuals of P. luteus with intestinal loops of type I can also be distinguished from P. burnupi (intestinal loops of type II) but individuals of P. luteus with intestinal loops of type II cannot. However, P. burnupi and P. luteus do not overlap geographically, and can be reliably distinguished using both mitochondrial and nuclear DNA sequences.
Distribution (Fig. 10A)
Australia: Queensland. Brunei. Indonesia: Ambon, Bali, Halmahera, Kei Islands, Lombok, Seram, Sulawesi, Sumatra, Ternate and Timor. Papua New Guinea: New Britain (type locality of O. schneideri), New Ireland and Madang. Philippines: Bohol and Luzon. Singapore (type locality of O. luteum and newly-collected material). Vietnam. All records are new, except for the type localities.
Habitat (Fig. 31)
Platevindex luteus is found both within mangroves and at mangrove margins. It is typically found on dead logs or tree trunks and, occasionally, on tree roots or under the loose bark of dead logs. In Timor, some individuals were found on pieces of wood and other plant material, but also on very dark mud (individuals were found directly on mud nowhere else).
Remarks
The publication dates of the different sections of Semper’s Landmollusken in the Reisen im Archipel der Philippinen series were clarified by Johnson (1969). Because Onchidium luteum was published before 1931, ICZN Article 12.2.7 applies: Onchidium luteum was made available in 1880 because Semper’s figures (pl. 20, fig. 10, pl. 23, figs 2, 6) are regarded as an indication accompanying it, although the text of the description was not published until 1882.
The species treated here is common and broadly distributed in the Indo-West Pacific, and so many original descriptions had to be reviewed and many type specimens examined in order to determine which existing names apply to it. The lectotype of Onchidium luteum displays all the distinctive characteristics of a species of Platevindex: flattened shape, narrow foot and no accessory penial gland. Also, its male opening is slightly to the right of the midline between the oral tentacles, which agrees with Semper’s (1882: 275) description and is perfectly compatible with Platevindex. Two main features indicate that the lectotype of O. luteum belongs to the species described here: the dorsal papillae on its notum as well as its penial anatomy, which is identical to what was observed in fresh material (Fig. 31C). Based on their dorsal notum (which also bears dorsal papillae) and Semper’s description (1882: 275) of the internal anatomy, it is very likely that the paralectotypes also are part of the species described here. In particular, Semper described a short penis with a distal, flexible, hook-bearing region scarcely 1 mm long and a retractor muscle that inserts by the heart. Semper also described 16–25 dorsal eyes and noted that the dorsal eyes never reach the edge of the dorsal notum, which is in agreement with our observations and with all species of Platevindex in clade C (see Fig. 4).
Semper (1882) did not mention or illustrate the type of intestinal loops in the original description of Onchidium luteum, and it could not be checked for the present study because the intestine of the lectotype is not well preserved (and that of the paralectotypes could not be checked either). However, Plate (1893: 181) examined two of the former syntypes and indicated that intestinal loops are of type II, which is compatible with our observations on freshly-collected samples from Singapore.
The intraspecific variation in the type of intestinal loops observed in Platevindex luteus (type I, type II and intermediary between types I and II) is very unusual. Nearly all onchidiid species are characterized by only one type of intestinal loops. Another known exception is Alionchis jailoloensis characterized by intestinal loops of both types II and III (Goulding et al. 2018a; Dayrat et al. 2019c). The dissection of individuals for which the species identification was confirmed through DNA sequences allowed us to determine that intestinal types vary between individuals of P. luteus even at the exact same localities.
Platevindex schneideri was described by Hoffmann (1932: 135–137), as Oncis schneideri, from New Britain, Papua New Guinea, as a flat animal with a rectal gland, no accessory penial gland and a male pore to the left of the right eye tentacle. Combined, these features indicate that Hoffmann was correct in describing the species in Plate’s genus Oncis (now Platevindex). Hoffmann (1932: 135) also described strong dorsal papillae (which he called ‘Tuberkeln’, or tubercles), a characteristic of P. luteus. The male parts of the holotype, now missing, were described and illustrated by Hoffmann (1932: 136), and the insertion of the retractor muscle at the level of the pericardium is compatible with P. luteus. The intestinal loops were described as of type II, which is compatible with the variation observed in P. luteus, but not with the sympatric species P. applanatus (in which intestinal loops are only of type I). For all the reasons above, Platevindex schneideri is regarded as a junior synonym of P. luteus.
Hoffmann (1932: 136) suggested that Platevindex schneideri might be a synonym of P. amboinae or P. granulosa (all as species of Oncis), but P. granulosa is a nomen dubium (see our species remarks on P. latus). However, since Hoffmann (1928: 36) considered Platevindex latus a synonym of P. granulosa, we can consider his comments on P. schneideri (Hoffmann 1932: 136) refer, in his mind, to P. amboinae and P. latus. Hoffmann’s (1932: 136) description of P. schneideri includes penial hooks, which are not found in either P. amboinae or P. latus (Table 4). Hoffmann did not describe the dorsal eyes on the back of O. schneideri, but there are at least 18 eyes (one eye per papilla) on the dorsal notum of the holotype. The presence of dorsal eyes also precludes P. schneideri from being a synonym of P. amboinae or P. latus, which both lack dorsal eyes (Table 4).
Hoffmann (1932: 135) noted a similarity between Platevindex schneideri and P. semperi (Plate, 1893), but concluded that they could not refer to the same species because their intestinal loops differed (type II in the holotype of P. schneideri and type I in P. semperi according to Plate’s original description). However, as mentioned above, P. luteus is an exception regarding intestinal loops, and both P. schneideri and P. semperi are compatible with the intraspecific variation in intestinal loops within P. luteus.
Plate’s (1893) description of Oncis semperi, based on two syntypes (22/18 and 22/ 18 mm) from Mindanao (ZMB/Moll 45661), is only compatible with P. coriaceus, and Platevindex semperi is thus regarded as a junior synonym of P. coriaceus. The description of intestinal loops of type I suggests that one of the two syntypes could belong to P. luteus instead of P. coriaceus, but this is most likely simply a mistake (see our remarks on P. coriaceus).
Britton (1984) described Platevindex mortoni from Hong Kong based on four specimens with different intestinal types: two specimens (including the holotype) with intestinal loops of type I, one with intestinal loops of type II and one with intestinal loops of an intermediate type between types I and II. Only the latter could be checked here because the digestive system is missing in all other types (see our remarks on P. tigrinus for a detailed description of the type material of P. mortoni). If Britton was correct that the intestinal loops of the holotype of P. mortoni were of type I, then P. mortoni would be incompatible with P. tigrinus, P. coriaceus or P. martensi (which are all characterized by a digestive system of type II), and the holotype of P. mortoni could be part of P. luteus. However, it is unclear whether Britton’s description of the intestinal loops of the holotype is correct (see our remarks on P. tigrinus for additional discussion of the status of P. mortoni). Also, P. luteus is not represented in the genetic sequences published by Sun et al. (2014) or other sequences available in GenBank from China. If P. luteus is later found in Hong Kong, then the name P. mortoni could be discussed as a possible synonym of P. luteus. For now, however, P. mortoni is regarded as a nomen dubium.
Von Martens (1897: 127) indicated that Onchidium luteum was found in “ Celebes Djenemaedja bei Luwu” [Djenemaedja by Luwu, Sulawesi, Indonesia] by M. Weber, but did not provide any details with respect to identification. Hoffmann (1928: 89–90) noted that it was impossible to determine whether the specimens von Martens examined from Sulawesi were O. luteum, since only the external appearance was described.
In a study focusing on the relative abundance of onchidiids across a Malaysian mangrove forest, Sabri & Singh (2018) mentioned P. luteus from Selangor, western Peninsular Malaysia. Based on the small picture provided and the absence of any additional details regarding ventral coloration, anatomy or DNA sequences, it is unclear whether this identification is correct. We did not find P. luteus at any of the localities we visited in western Peninsular Malaysia. Thus, the presence of P. luteus in Selangor is regarded here as hypothetical.
Platevindex luteus is not a new combination because it was already used in our recent studies (Dayrat 2009: 5; Goulding et al. 2018a, 2018b, 2018c; Dayrat et al. 2019a, 2019 b, 2019c, 2019d), even though the classification in Platevindex is demonstrated here for the first time. Note that Stantschinsky (1907: 395) and Hoffmann (1928: 89) had already moved Onchidium luteus to Plate’s genus Oncis, based on information from the original description (Semper 1882).
description: Published as part of 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), pp. 1-133 in European Journal of Taxonomy 737 (1) on pages 68-78, DOI: 10.5852/ejt.2021.737.1259, http://zenodo.org/record/4594357