Platevindex martensi ( Plate, 1893 ), 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 : 96-103

Platevindex martensi ( Plate, 1893)

Figs 54–58

Oncis martensi Plate, 1893: 196–197 , pl. 7, figs 7, 23a, pl. 10, fig. 50.

Oncis inspectabilis Plate, 1893: 198–199 . Syn. nov.

Onchidium coriaceum – Semper 1880: 271–273 (in part only) [non Onchidium coriaceum Semper, 1880 ].

Oncis martensi – Stantschinsky 1907: 395. — Hoffmann 1928: 89.

Oncis inspectabilis – Stantschinsky 1907: 395.

Platevindex martensi – Dayrat 2009: 5.

Platevindex mortoni – Zhang et al. 2017: fig. 1e (non Platevindex mortoni Britton, 1984 ).

Material examined

Holotype

THAILAND • holotype (44/ 41 mm) by monotypy; Petshaburi, Gulf of Siam [Phetchaburi, Gulf of Thailand]; ZMB/Moll 8454 .

Holotype of Oncis inspectabilis

MYANMAR • holotype (28/ 23 mm) by monotypy; Lampee , Birma [ Lampi Island , Mergui Archipelago, southern Myanmar, Andaman Sea]; Anderson leg.; ZMB/Moll 38934 .

Notes on type material

Oncis martensi . The holotype was previously dissected. Internal organs are mostly missing; only a few pieces of the female (posterior) reproductive system and digestive system remain. The penial complex and buccal mass are missing.

Oncis inspectabilis . The holotype was previously dissected. Internal organs are mostly missing. The buccal mass remains, as well as pieces of the deferent duct, oviduct and spermatheca.

Other material

AUSTRALIA – Northern Territory • 4 specs (39/26 [1711], 25/20 [1709], 25/20 [1710] and 13/12 [1707] mm); Darwin , Elizabeth Road ; 12°32.893′ S, 130°57.642′ E; 20 Aug. 2012; station 70; Ceriops and old logs in Rhizophora forest; NTM P.57611 .

BRUNEI • 1 spec. (43/29 [1040] mm); near Batu Marang; 04°59.131′ N, 115°01.820′ E; 29 Jul. 2011; station 34; old mangrove with tall Rhizophora trees with high roots and Thalassina mounds; BDMNH.

INDONESIA – Sumatra • 1 spec. (52/19 [1767] mm); Pulau Sinaboi; 02°18.145′ N, 100°59.309′ E; 8 Oct. 2012; station 73; some small Avicennia and Rhizophora near shore; UMIZ 00107 • 1 spec. (22/13 [1776] mm); Dumai ; 01°42.838′ N, 101°23.286′ E; 9 Oct. 2012; station 74; mangrove just behind abandoned buildings, high intertidal; UMIZ 00108 • 1 spec. (34/19 [1748] mm); Sungai Lubuk; 05°40.174′ S, 105°34.097′ E; 19 Oct. 2012; station 79; mounds of Thalassina , Rhizophora , dead logs in the high intertidal; UMIZ 00109 . – Sulawesi • 2 specs (36/23 [2334] and 35/23 [2333] mm); Makassar City, Tallo ; 05°06.117′ S, 119°26.777′ E; 21 Mar. 2013; station 92; small mangrove with outhouse in center; UMIZ 00111 .

MALAYSIA – Peninsular Malaysia • 1 spec. (30/18 [964] mm); Nibong Tebal, Pulau Burung ; 05°12.488′ N, 100°25.564′ E; 11 Jul. 2011; station 17; Rhizophora mangrove with a few Sonneratia and soft mud; USMMC 00029 • 1 spec. (31/30 [934] mm); Balok; 03°53.219′ N, 103°21.978′ E; 14 Jul. 2011; station 19; Rhizophora mangrove with some Avicennia and mostly hard mud; USMMC 00030 • 2 specs (37/23 [no DNA] and 36/18 [no DNA] mm); Merbok ; 05°39.035′ N, 100°25.782′ E; 18 Jul. 2011; station 21; deep Rhizophora forest with old, tall trees, hard mud, many small creeks and dead logs; USMMC 00031 • 1 spec. (39/21 [933] mm); Merbok ; 05°40.143′ N, 100°26.178′ E; 19 Jul. 2011; station 22; mangrove of mostly Rhizophora , some Avicennia with soft mud near creek; USMMC 00077 • 1 spec. (37/15 [no DNA] mm); Langkawi , Tanjung Rhu; 06°25.317′ N, 99°50.106′ E; 15 Jul. 2011; station 26; open forest of Rhizophora , Sonneratia , Bruguiera with high mounds of mud around some trees; USMMC 00032 • 1 spec. (32/24 [930] mm); Kuala Sepatang; 04°50.434′ N, 100°38.176′ E; 19 Jul. 2011; station 27; old Rhizophora and Acrostichum ferns very high in tidal zone, near boardwalk; USMMC 00033 .

PHILIPPINES – Bohol • 2 specs (31/16 [3342] and 14/8 [3336] mm); Mabini; 09°51.532′ N, 124°31.685′ E; 17 Jul. 2014; station 194; narrow Rhizophora and Avicennia mangrove by the sea with fish ponds built on landward side, many dead logs; PNM 041250 • 4 specs (51/27 [3365], 34/22 [3364], 33/14 [3362] and 24/11 [3358] mm); 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 041251 .

SINGAPORE • 1 spec. (31/20 [988] mm); Pasir Ris Park ; 01°22.840′ N, 103°57.224′ E; 30 Mar. 2010; station 5; mud and dead logs in upper tidal; ZRC.MOL.10480 • 3 specs (40/22 [no DNA], 37/20 [no DNA] and 35/21 [987] mm); Lim Chu Kang; 01°26.785′ N, 103°42.531′ E; 5 Apr. 2010; station 9; piece of wood in Avicennia and Rhizophora mangrove; ZRC.MOL.10481 .

Description

Color and morphology of live animals ( Figs 54–55A )

Live animals are not usually covered with mud, and their natural color is visible without washing. The dorsal notum is brown to dark brown or black, often mottled with two colors. The notum bears small elongated (longitudinal) ridges. The ventral color varies but the hyponotum is yellow, beige or yellow-orange, with distinct darker spots of variable size (small to large) and color (faintly tan to black). When those spots are large and dark enough, the hyponotum appears nearly black (which was most common in the Strait of Malacca). The hyponotum of juvenile specimens can be marked by fewer spots. In Malaysia, Singapore and Brunei, the edge of the hyponotum commonly is orange, which was also occasionally observed in other populations. The foot is distinctively orange. Papillae with dorsal eyes are present. Their exact number is variable (generally between 20 and 65). Each papilla bears one dorsal eye. Eyes are distributed across the notum and many eyes are found at the margin (i.e., eyes can be <2 mm from the notum edge).

Digestive system ( Figs 2 C–D, 55B–C, 56)

Radulae measure up to 5 mm in length. Examples of radular formulae are presented in Table 5 . The intestinal loops are of type II, with a transitional loop oriented between 6 and 9 o’clock.

Reproductive system ( Figs 55 D–F, 57)

In the posterior part of the reproductive system, the oviduct is wider than the deferent duct (approximately up to twice as wide). Its distal section (distal to the spermatheca) is approximately up to twice as long as its proximal section. The deferent duct is longer than the oviduct, not attached to it, and highly coiled with tight, long, U-shaped loops. However, the deferent duct tends to be shorter in Malaysia and Northern Territory ( Australia), and considerably longer in Brunei and the Philippines. The female pore is very close to the anus, between 0.5 mm and 2.5 mm apart. The distal, flexible region of the penis with hooks is approximately 2 to 2.5 mm long and approximately 170 µm wide. Penial hooks are relatively large, approximately 35 to 55 µm long ( Fig. 57B ), and can be seen inside the semi-transparent penis or when the penis is evaginated like the finger of a glove in the vestibule ( Fig. 57A ). The posterior retractor muscle of the penis inserts on the right side, within the third (posterior) quarter of the visceral cavity. The length of the retractor muscle varies from half the length of the penial sheath to slightly longer than the penial sheath. The deferent duct is highly convoluted (but is less convoluted in juvenile specimens).

Distinctive diagnostic features ( Table 4 )

Externally, the orange foot distinguishes Platevindex martensi from all other species of Platevindex . The small, elongated ridges on its dorsal notum are also present in P. aptei sp. nov., but the foot of P. aptei sp. nov. is black. The presence of many dorsal eyes right at the margin of the dorsal notum (within 2 mm from the edge) is only shared by P. martensi and P. aptei sp. nov. Internally, the long deferent duct with elongated loops in the anterior penial apparatus (which is not closely attached to the oviduct) differentiate P. martensi from other species of Platevindex . Also, the penial retractor muscle inserts between ½ to ¾ down the length of the visceral cavity in P. martensi while it inserts at the posterior end of the cavity in P. aptei sp. nov.

Distribution ( Fig. 10C )

Australia: Northern Territory. Brunei. Indonesia: Sulawesi, Sumatra. Peninsular Malaysia. Myanmar: Andaman Sea (type locality of P. inspectabilis ). Philippines: Bohol. Singapore. Thailand: Gulf of Thailand (type locality of P. martensi ). All records are new, except for the type localities.

Habitat ( Fig. 58 )

Platevindex martensi is typically found in or near mangroves, on tree roots and trunks as well as dead logs. It usually lives in the high intertidal only reached by the highest tides (with Acrostichum ferns). It can also be found in cement ditches nearby a mangrove. One juvenile was found on coarse-grained sand in a mangrove forest in the Philippines, but Platevindex slugs normally are not found directly on mud or sand. Platevindex martensi is not found on rocky shores.

Remarks

All of the distinctive characters of Platevindex are present in the holotype of Oncis martensi , including a flattened and hard body, a narrow foot, a male opening to the right of the midline between the two eye tentacles and no accessory penial gland. In the original description of P. martensi, Plate (1893: 196) wrote that the holotype was collected from Singapore by professor von Martens. However, von Martens (1897: 128) later wrote that “ Oncis martensi Plate was not found by me at Singapore, but at Petshaburi in the Gulf of Siam,” which is in the north of the Gulf of Thailand. The label of the holotype at the Berlin Museum now reads “ Siam, Petehabardi” (presumably a misspelling). Hoffmann (1928: 89) considered Petshaburi to be the type locality and even specified “ Singapore, Plate, ex errore, nach Martens 1897.” Also, note that the specific name appears as “ martensi ” in the text and in one figure caption ( Plate 1893: 196, pl. 7, fig. 23a) but as “ martensii ” in the two other figure captions ( Plate 1893: pl. 7, fig. 7, pl. 10, fig. 50).

The posterior (female) reproductive system in the holotype of P. martensi is largely destroyed. The hermaphroditic gland is in pieces and disconnected from the hermaphroditic duct. A large part of the female gland mass is separated from the oviduct and the deferent duct. However, the long and convoluted deferent duct is intact and is only consistent with the species described here. Plate (1893: 197) also described the color of the live animal (based on field notes from von Martens) as having an intense yellow hyponotum with black marbling as well as a light gray-brown foot. A yellow hyponotum is only found in P. martensi and P. aptei sp. nov. The color of the foot is the external trait which can distinguish these two species, and Plate’s description of “light gray-brown” is a closer match to the bright orange foot of P. martensi than the dark black foot of P. aptei sp. nov. The number of dorsal eyes he described (90) is higher than what we have observed in P. martensi , but we could not check this as the dorsal eyes have lost their pigment. Plate’s (1893: 197) description of the dorsal eyes that “sit alone on the big warts” is consistent with this species, but his comment that “this rule does not apply without exception, because on about 12 warts there are 2 eye spots, so that one can speak in these cases of a group” is surprising. We have found no evidence that dorsal eyes occur in groups of two in this species; Plate’s statement that dorsal eyes occurred in pairs suggests that his count of dorsal eyes is likely an overestimate.

Plate’s (1893: 198–199) original description of Platevindex inspectabilis from an island in southern Myanmar, in the Andaman Sea, mentioned the diagnostic characters of Platevindex . Plate indicated intestinal loops of type II, but this could not be verified because the intestine of the holotype was previously dissected. Plate’s original description indicates a black-blue hyponotum (the color of the holotype has faded over time and could not be verified). Fresh specimens were not available from Myanmar, but many specimens were observed with a nearly solid black hyponotum (due to a high density of black spots) along the north-western coast of peninsular Malaysia. Despite a slight difference in the description of the hyponotum color, it can be determined that the holotype of P. inspectabilis belongs to the species described here due to the remains of its female (posterior) reproductive system. The length of the deferent duct adjacent to the oviduct is long and convoluted with elongated loops, which is indistinguishable from P. martensi (the deferent duct is similar in length in specimens of a similar size from Peninsular Malaysia). The length of the distal portion of the penis with hooks in P. inspectabilis (2 mm) also fits exactly the size range observed in P. martensi (2–2.5 mm). So, for all the reasons above, P. inspectabilis is considered here to be a junior synonym of P. martensi .

Semper’s (1882) original description of Onchidium coriaceum was based on syntypes that are part of at least two species (see our remarks on Platevindex coriaceus coriaceus ). One paralectotype of O. coriaceum from Penang belongs to P. martensi . Indeed, its posterior (female) reproductive system is not compatible with P. coriaceus , P. tigrinus or P. luteus , but displays the diagnostic feature of P. martensi (the wide, long, highly-convoluted deferent duct adjacent to the oviduct). In addition, Semper rightly noted that dorsal eyes are present across the notum including on its margin, and dorsal eyes very close to the notum edge (<2 mm) are only found in P. martensi and P. aptei sp. nov.

Zhang et al. (2017) recently re-described a species they identified as Platevindex mortoni based on specimens from Hong Kong, but P. mortoni is considered here a nomen dubium and their description is based on specimens that belong to at least two different species. One individual illustrated with a bright orange foot ( Zhang et al. 2017: fig. 1e) is identified here as P. martensi .

Plate (1893: 196–199) did not comment on the very close similarity between Platevindex inspectabilis and P. martensi in his original descriptions, but he compared P. inspectabilis to P. semperi , from the Philippines ( Plate 1893: 199). This may be due to a similarity in their hyponotum color; the preserved hyponota of both O. inspectabilis and O. semperi were described by Plate as dark blue (though, now, decades later, the hyponotum is creamish in the type specimens of both species). However, P. inspectabilis and P. semperi are not regarded as synonyms because Plate’s (1893: 193) description of the copulatory apparatus of P. semperi indicates that it is a junior synonym of P. coriaceus . Platevindex inspectabilis was also proposed as a synonym of Oncis stuxbergi by Hoffmann (1928: 88) and Labbé (1934: 235), but Vaginulus stuxbergi Westerlund, 1883 actually belongs to the genus Onchidium ( Dayrat et al. 2016) .

We collected Platevindex martensi in Northern Territory, Australia, but did not find it in Queensland, Australia, though it cannot be excluded that we missed it there. An online photo (viewed at https://www.inaturalist.org/observations/14094815 on 30 Jul. 2018) from Maroochy, Mooloolaba, Queensland, shows a Platevindex slug with elongated dorsal ridges similar to those found in P. martensi and P. aptei sp. nov. Also, its description mentions that it is an “orange footed mangrove onch slug.” Because no photograph of the ventral surface is available, the identification of that slug cannot be confirmed. Until this geographic record is confirmed by the examination of actual specimens, Queensland is not considered part of the geographic distribution for P. martensi .

Figures

Fig. 54. Platevindex martensi (Plate, 1893), live animals. A. Dorsal view, 34 mm long [1748], Indonesia, Sumatra (UMIZ 00109). B. Dorsal view, 24 mm long [3358], Philippines, Bohol (PNM 041251). C. Dorsal view, 34 mm long [3364], Philippines, Bohol (PNM 041251). D. Dorsal view, 13 mm long [1707], Australia, Darwin (NTM P.57611). E. Dorsal view, 38 mm long [#1], Peninsular Malaysia, Langkawi (USMMC 00032). F. Dorsal view, 25 mm long [1709], Australia, Darwin (NTM P.57611). G. Ventral view, 36 mm long [2334], Indonesia, Sulawesi (UMIZ 00111). H. Ventral view, same as C. I. Ventral view, same as F. J. Ventral view, 31 mm long [934], Peninsular Malaysia, Balok (USMMC 00030). K. Ventral view, 30 mm long, [964], Peninsular Malaysia, Penang (USMMC 00029).

Fig. 55 Platevindex martensi (Plate, 1893), external morphology, digestive and reproductive systems. A. Dorsal notum, entire animal, Bohol, Philippines [3365] (PNM 041251). B. Digestive system, dorsal view, type II with a transitional loop oriented at 9 o’clock, Sulawesi, Indonesia [2333] (UMIZ 00111). C. Digestive system, dorsal view, type II with a transitional loop oriented at 6 o’clock, Peninsular Malaysia [964] (USMMC 00029). D. Posterior reproductive system (remaining parts), Phetchaburi, Gulf of Thailand, holotype (ZMB/Moll 8454). E. Posterior reproductive system, Darwin, Northern Territory, Australia [1711] (NTM P.57611). F. Anterior, male copulatory apparatus, same as E. Abbreviations: dd = deferent duct; ddg = dorsal digestive gland; fgm = female gland mass; hd = hermaphroditic duct; hg = hermaphroditic gland; i = intestine; ov = oviduct; pdg = posterior digestive gland; ps = penial sheath; rg = rectal gland; rm = retractor muscle; rs = receptaculum seminis; sp = spermatheca; st = stomach; v = vestibule. Scale bars: A = 10 mm; B–C = 3 mm; D–F = 2 mm.

Fig. 56.Platevindex martensi (Plate, 1893),radula, Philippines, Bohol[3336].A. Rachidian and innermost lateral teeth. B. Innermost lateral teeth. C. Lateral teeth. D. Outermost lateral teeth. Abrreviations: lp = lateral protuberance. Scale bars: A, D = 20 μm; B–C = 30 μm.

Fig. 57.Platevindex martensi (Plate, 1893), penial hooks.A. Penis everted with hooks outside, Peninsular Malaysia, Penang [964] (USMMC 00029). B. Australia, Darwin [1711] (NTM P.57611). Scale bars: A = 50 μm; B = 30 μm.

Fig. 58. Habitats of Platevindex martensi (Plate, 1893). A. Philippines, Bohol, narrow mangrove will tall trees on edge of fish ponds, cement ditches between the mangrove patches and the ponds (station 195). B. Philippines, Bohol, narrow mangrove on the edge of fish ponds, tall Rhizophora and Avicennia, many dead logs (station 194). C. Indonesia, Sulawesi, small mangrove used as outhouse by village, very impacted by trash (station 92). D. Australia, Darwin, Ceriops and old logs in Rhizophora forest (station 70).

Fig. 2. Intestinal loops of type II. Small black arrows show the direction of the intestinal transport. The clockwise loop is in blue. The counterclockwise loop is in yellow. The transitional loop (between clockwise and counterclockwise loops) is in green. Red arrows indicate the orientation of the transitional loop. A. Type II (as defined by Plate 1893), with a transitional loop oriented at 9 o’clock, redrawn from Plate (1893: pl. 8, fig. 31). B. Type II, with a transitional loop oriented at 9 o’clock, Platevindex coriaceus coriaceus (Semper, 1880) unit #2 [3170] (PNM 041236), Luzon, Philippines. C. Type II, with a transitional loop oriented at 9 o’clock, P. martensi (Plate, 1893) [2333] (UMIZ 00111), Sulawesi, Indonesia. D. Type II, with a transitional loop oriented at 6 o’clock, P. martensi [964] (USMMC 00029), Peninsular Malaysia. E. Type II, with a transitional loop oriented at 8 o’clock, P. luteus (Semper, 1880) [3367] (PNM 041246), Bohol, Philippines. F. Type II, with a transitional loop oriented at 8 o’clock, P. aptei Goulding & Dayrat sp. nov., [5955] (USMMC 00078), Peninsular Malaysia. G. Type II, with a transitional loop oriented at 7 o’clock, P. burnupi (Collinge, 1902) [3150] (MNHN-IM-2019-1398), Madagascar. H. Type II, with a transitional loop oriented at 7 o’clock, P. coriaceus coriaceus unit #2 [3256] (PNM 041238), Bohol, Philippines. Scale bars: B–H = 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).