Platevindex latus ( 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 : 116-121

Platevindex latus ( Plate, 1893)

Figs 70–73

Oncis lata Plate, 1893: 191–192 , pl. 7, fig. 2, pl. 11, fig. 59.

Oncis lata – Stantschinsky 1907: 395.

Platevindex latus – Dayrat 2009: 5.

Material examined

Lectotype (here designated)

PAPUA NEW GUINEA • lectotype (27/ 27 mm); Neu-Britannien [New Britain, Papua New Guinea]; ZMB/Moll 45656a .

Paralectotypes

PAPUA NEW GUINEA • 3 paralectotypes (28/27, 27/24 and 23/ 26 mm); same collection data as for lectotype; ZMB/Moll 45656b .

Notes on type material

The lectotype was dissected for the present study and all its internal organs were left inside except for the penial complex, which was extracted and retained in a small vial. The three paralectotypes were previously dissected and are completely empty with no internal organs. All their male parts are missing. Pieces of dorsal notum, stomach, digestive gland, intestine and female gland mass remain in the jar, all mixed together, but they cannot be assigned to a particular paralectotype.

Other material

PAPUA NEW GUINEA • 3 specs (33/28 [#3], 32/31 [#1] and 30/25 [#2] mm); New Britain?; ZMH 27511 .

Description

Color and morphology ( Fig. 70 ) The color of live slugs is unknown. The preserved dorsal surface is dark brown, occasionally with lighter brown, longitudinal stripes. The preserved hyponotum is blue-grey and the foot is light yellow. Dorsal papillae are large and thorny, and do not bear dorsal eyes.

Digestive system ( Figs 3B , 71–72 )

Radulae measure up to 7.2 mm in length. Examples of radular formulae are presented in Table 5 . The intestinal loops are of type III, with a transitional loop oriented between 12 and 2 o’clock ( Figs 3B , 72 ).

Reproductive system ( Fig. 73 )

In the posterior reproductive system, the oviduct is short and approximately as wide as the deferent duct. Its distal section (distal to the spermatheca) is approximately as long as its proximal section. The deferent duct is longer than the oviduct, not attached to it, and is tightly coiled with a few short U-shaped loops. There are no hooks inside the distal, flexible region of the penis. The posterior retractor muscle inserts in the anterior half of the visceral cavity. The retractor muscle of the penis varies from approximately half the length of the penial sheath to ¾ its length. The deferent duct is highly convoluted.

Distinctive diagnostic features ( Table 4 )

Platevindex latus and P. amboinae are the only known species of Platevindex with no dorsal eyes and no penial hooks. Platevindex latus can be distinguished from P. amboinae externally by its large and thorny dorsal papillae and internally by its anterior deferent duct, which is slightly less convoluted.

Distribution ( Fig. 10C )

Papua New Guinea: New Britain (type locality and present study).

Habitat

No habitat was mentioned in the original description of P. latus or on the labels of the additional material. However, P. latus likely lives on dead logs in mangroves, like its close relative P. amboinae .

Remarks

The flattened body and narrow foot of the lectotype of Platevindex latus clearly indicate that it belongs to Platevindex . In the original description, Plate (1893) did not mention whether a rectal gland is present or absent, but it is present in the lectotype as well as in the non-type material (it is present in all species of Platevindex ). An accessory penial gland is also absent in both the lectotype and the non-type material (it is absent in all species of Platevindex ).

In the original description, Plate (1893: 191) described dorsal “conical granules” and indicated that “the mantle appears through them as if spiked with small thorns.” Conical papillae are present in the lectotype and all paralectotypes of P. latus as well as in the additional material from Papua New Guinea. Plate (1893: 192) described the length of the penis but did not mention penial hooks, so it can be assumed that he did not see penial hooks in the types he dissected (now paralectotypes). However, because the male parts are missing from the three paralectotypes dissected by Plate, this could not be confirmed. At any rate, penial hooks are absent in the lectotype dissected for the present study. The intestinal loops of the lectotype are of type III and Plate’s (1893: 192) description of a type II likely is a mistake, which would be consistent as he made the same error in the description of P. amboinae .

Fresh material for DNA sequencing was not available. Platevindex latus was not collected during the recent MNHN expeditions in Madang and New Ireland, Papua New Guinea. Some old material discovered at the Zoologisches Museum in Hamburg seems to be part of P. latus even though its locality is uncertain (the label in the jar states “ Papua New Guinea. New Britain? Museum Godeffroy”). This material is externally identical to the lectotype (and paralectotypes) of P. latus . Plate (1893: 192) described a penis measuring 7 mm long (the proximal chondroid tube being 5 mm long and the distal, flexible region being 2 mm long). In one specimen from the Zoologisches Museum in Hamburg, the chondroid tube also measured 5 mm, but the distal region without hooks was 0.5 mm long rather than 2 mm. However, individual variation in this character occurs within species of Platevindex , and more specimens are needed to evaluate the variation for this trait within P. latus .

Hoffmann (1928: 86) suggested that Platevindex latus (as Oncis lata ) was a synonym of Onchidium granulosum Lesson, 1831 (type locality New Ireland, Papua New Guinea), based on the original descriptions. Although Hoffmann acknowledged that Lesson’s description was not very informative, he considered that Lesson’s description of a notum being much wider than the sole indicated that Onchidium granulosum referred to a species of Oncis (Platevindex) . Labbé (1934: 234) agreed with Hoffmann. However, Lesson’s description is brief and leaves out many important details, such as whether dorsal eyes are present or not. The wide foot in Lesson’s illustration of Onchidium granulosum (Lesson 1831: pl. 14, fig. 2) does not appear to represent a species of Platevindex . The description of the habitat as a rocky shore also strongly suggests that Onchidium granulosum does not apply to a species of Platevindex , but, instead, possibly to a species of Peronia or Wallaconchis . Adams & Adams (1855: 234) transferred Onchidium granulosum to Onchidella with no justification. Because its type material could not be located and its internal anatomy was not described by Lesson, Onchidium granulosum is regarded here as a nomen dubium which applies to an onchidiid species of an unidentifiable genus.

Von Martens (1897: 128) indicated that M. Weber found Oncis lata in “Celebs: M̹ndung des Flusses Djenemaedja in Luwu” [Sulawesi: mouth of the river Djenemaedja in Luwu]. Measurements were provided for the largest and smallest specimens, and the edge of the hyponotum was described as dirty yellow-gray. Von Martens indicated that the specimens are exactly the same as Plate’s (1893) description of O. lata , except for the color of edge of the hyponotum. However, when specimens from Luwu collected by M. Weber (identified as Oncis lata ) were examined, they did not have the large thornlike papillae characteristic of P. lata . Thus, Sulawesi is not considered part of the geographic range of P. lata , and those specimens are identified here as P. amboinae (see that species).

Bretnall’s (1919: 323) description of Oncis lata is merely a translation of Plate’s original description, except that Plate’s (1893: 191) correct statement that “eyes are missing” was changed to “eyes are present on all of the papillae.” Bretnall likely assumed that Plate made a mistake because dorsal eyes are present in most other species of Platevindex and because eyes can be difficult to see when dorsal papillae are retracted. However, it is confirmed here that dorsal eyes are not present in the type material of Platevindex latus .

Labbé (1934: 234) identified two specimens (24/17 and 19/ 14 mm) from the Malabar coast (southwest India) collected by M. Dussumier as Oncis granulosa , but also indicated that the exterior aspect of his specimens was similar to that of Oncis lata from New Britain. However, Labbé also reported that the notum is granular with tubers that are not prominent, and that dorsal eyes are not very visible. The intestinal loops are also described as type II by Labbé, while they are of type III in Oncis lata . Due to the lack of dorsal papillae in the specimens Labbé examined, and the fact that Labbé’s description suggests that dorsal eyes may have simply been retracted, the specimens he examined are not considered to be Oncis lata . It is also worth noting that the specimens Labbé examined from western India are very distant from New Britain, Papua New Guinea, and that no observations of Oncis lata have been confirmed west of New Britain.

Morphological evidence suggests that Platevindex latus is closely related to P. amboinae because both species lack penial hooks and dorsal eyes, which are present in all other species of Platevindex . They also are the only species of Platevindex with intestinal loops of type III.

Figures

Fig. 70. Platevindex latus (Plate, 1893), preserved specimens. A. Dorsal view, 24 mm, syntype, New Britain, Papua New Guinea (ZMB/Moll 45656). B. Ventral view, same as A. C. Close-up of papillae, same as A. D. Dorsal view, 25 mm, Papua New Guinea (ZMH 27511). E. Ventral view, same as D.

Fig. 71. Platevindex latus (Plate, 1893), radula, Papua New Guinea [#1] (ZMB/Moll 45656). A–C. Rachidian and lateral teeth. D. Lateral teeth. E. Outermost lateral teeth. Scale bars: A, D = 100 μm; B, E = 20 μm; C = 50 μm.

Fig. 72. Platevindex latus (Plate, 1893), digestive system, dorsal view, intestinal loops of type III. A. Transitional loop oriented at 2 o’clock, New Britain, Papua New Guinea, lectotype (ZMB/Moll 45656a). B. Transitional loop oriented at 12 o’clock, Papua New Guinea [#1] (ZMH 27511). C. Transitional loop oriented at 2 o’clock, Papua New Guinea [#2] (ZMH 27511). Abbreviations: ddg = dorsal digestive gland; i = intestine; pdg = posterior digestive gland; rg = rectal gland; st = stomach. Scale bars = 3 mm.

Fig. 73. Platevindex latus (Plate, 1893), reproductive system. A. Posterior reproductive system, Papua New Guinea [#2] (ZMH 27511).B.Anterior, male copulatory apparatus, New Britain, Papua New Guinea, lectotype (ZMB/Moll 45656a). C. Anterior, male copulatory apparatus, same as A. Abbreviations: dd = deferent duct; fgm = female gland mass; hd = hermaphroditic duct; hg = hermaphroditic gland; ov = oviduct; ps = penial sheath; rm = retractor muscle; rs = receptaculum seminis; sp = spermatheca; v = vestibule. Scale bars: A = 3 mm; B–C = 2 mm.

Fig. 3. Intestinal loops of type III. 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 III, with a transitional loop oriented at 3 o’clock, Onchidium stuxbergi (Westerlund, 1883) (from Dayrat et al. 2016: fig. 11b). B. Type III, with a transitional loop oriented at 12 o’clock, Platevindex latus (Plate, 1893) (ZMH 27511, #1), Papua New Guinea. C. Type III, with a transitional loop oriented at 1 o’clock,P. amboinae (Plate, 1893), lectotype (ZMB/Moll 11621a), Ambon, Indonesia. D. Type III, with a transitional loop oriented at 2 o’clock, P. amboinae [2883] (UMIZ 00105), Seram, Indonesia. E. Type III, with a transitional loop oriented at 6 o’clock, P. amboinae (SMF 333602, #1), Sulawesi, Indonesia. Scale bars: A–B = 5 mm; C–E = 4 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).