Wallaconchis ater (Lesson, 1830)

Goulding, Tricia C., Khalil, Munawar, Tan, Shau Hwai & Dayrat, Benoit, 2018, Integrative taxonomy of a new and highly-diverse genus of onchidiid slugs from the Coral Triangle (Gastropoda, Pulmonata, Onchidiidae), ZooKeys 763, pp. 1-111: 1

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scientific name

Wallaconchis ater (Lesson, 1830)

comb. n.

Wallaconchis ater (Lesson, 1830)  comb. n. Figs 34, 35, 36, 37, 38, 39, 40, 41, 42

Onchidium ater  Lesson, 1830: 300; Bretnall 1919: 327; Hoffmann 1928: 84-85.

Onchidium keiense  Hoffmann, 1926: 18-24, figs 1-5; Hoffmann 1928: 81(as Oncidium keiense  ). syn. n.

Scaphis atra  : Labbé 1934: fig. 30.

Paraoncidium keiense  : Labbé 1934: 230.

Lessonina ferruginea  : Labbé 1934: fig. 50 [non Onchidium ferrugineum  Lesson, 1830].

Type locality

( O. ater  ). Havre de Doréry (for Dorey), à la Nouvelle Guinée [Manokwari, West Papua, Indonesia]. No fresh material was collected from the type locality. However, fresh material was collected from Halmahera, approximately 700 kilometers from the type locality in West Papua (see below, additional material).

Type locality ( O. keiense  ). Toeal (Kei-Inseln) [Kei Islands, Moluccan Islands, Indonesia]. Fresh specimens were collected from the type locality (see below, additional material).

Type material ( O. ater  ). Two syntypes: 30/17 and 28/15 mm (MNHN 22950). Both syntypes were previously dissected and some internal organs are missing. The posterior (female) reproductive parts remain in the smaller syntype and only the oviduct remains in the larger syntype. The male (anterior) parts are missing in both syntypes. The digestive system is present in both syntypes, but the intestinal loops are not preserved.

Type material ( O. keiense  ). Lectotype, 32/21 mm, designated here (ZMUC). Thirty paralectotypes (35/24 to 11/8 mm) are well preserved (ZMUC), although several specimens were dissected prior to the present study and the male parts were previously removed (ZMUC). The lectotype was dissected for this study and all organs left in vials inside the jar. The species name on the label is Onchidium mortenseni  . However, the rest of the information on the label (specimens collected by Mortensen from Toeal and studied by Hoffmann) is identical to the information in Hoffmann’s original description of O. keiense  (the collector is not mentioned in the species description, but the title of the paper indicates the species are described based on collections from Mortensen’s expedition). The only other onchidiid species described by Hoffmann from the Kei Islands was Onchidium verruculatum  Cuvier, 1830, which Hoffmann recognized thanks to the presence of gills on the posterior notum ( O. verruculatum  actually belongs to the genus Peronia  ). Gills are not visible on any of the syntypes labeled O. mortenseni  , which strongly suggests that those specimens are the type material of O. keiense  and that Hoffmann changed his mind for the specific name (i.e., he replaced mortenseni  by keiense  ).

Additional material examined.

Indonesia, North Sulawesi, Bahoi, 01°43.36'N, 125°01.23'E, 5 specimens 37/15 mm [2170], 30/15 mm [2145], 26/16 mm [2164], 25/14 mm [2157] and 25/11 mm [2177], st 85, sand and small rocks outside a mangrove (UMIZ 00049); North Sulawesi, Bahoi, 01°43.36'N, 125°01.23'E, 3 specimens 30/18 mm [2221], 29/16 mm [2220] and 26/17 mm [2228], st 88, sand and small rocks outside a mangrove (UMIZ 00050); North Sulawesi, Wori, 01°36.06'N, 124°51.73'E, 1 specimen 33/22 mm [2283], st 90, old Avicennia  , Sonneratia  , Rhizophora  mangrove (UMIZ 00038); North Sulawesi, Mantehage Island, 01°41.88'N, 124°46.74'E, 1 specimen 25/16 mm [2330], st 91, rocks behind a Sonneratia  and Rhizophora  mangrove (UMIZ 00039); Ambon, Haruku Island, 03°36.52'S, 128°25.07'E, 1 specimen 9/8 mm [2727], st 127, rocky Sonneratia  mangrove with coral rubble (UMIZ 00040); Maluku, Kei Islands, Tual City, Fiditan, 5°35.96'S, 132°45.11'E, 1 specimen 17/9 mm [2939], st 144, rocks behind muddy mangrove of Rhizophora  trees (UMIZ 00041); Lombok, Seriwe Bay, 08°51.70'S, 116°32.87'E, 1 specimen 18/10 mm [2966], st 147, small beach of coral rubble and rocks by bay (UMIZ 00042); Lombok, Seriwe Bay, 08°54.55'S, 116°22.22'E, 2 specimens 43/20 mm [2970] and 35/24 mm [2974], st 148, rocks behind mangrove with Avicennia  trees (UMIZ 00043); Lombok, Don Don, 08°54.54'S, 116°21.50'E, 2 specimens 35/19 mm [2986] and 25/13 mm [2978] st 149, old Avicennia  forest with coral rubble (UMIZ 00051); Bali, Gilimanuk, 08°10.26'S, 114°26.61'E, 1 specimen 18/14 mm [3591], st 155, large rocks near a patch of Rhizophora  (UMIZ 00052); Bali, Pemuteran, Labuhan Lalang Harbor, 08°08.61'S, 114°32.33'E, 3 specimens 22/12 mm [3137], 20/11 mm [3132], and 14/8 mm [3130], st 157, coral rubble, rocks and a few Avicennia  (UMIZ 00053); North Maluku, Ternate, Bastiong, 00°46.41'N, 127°22.76'E, 1 specimen 38/17 mm [5057], st 203, muddy rocks near a mangrove (UMIZ 00046); Halmahera, Akelamo, 01°01.33'N, 127°39.09'E, 1 specimen 35/20 mm [5078], st 207, sandy-muddy beach at margin of mangrove (UMIZ 00047); Halmahera, Foli, 01°14.66'N, 128°10.61'E, 1 specimen 28/16 mm [5121], st 217, rocky shore near a beach (UMIZ 00048); Halmahera, Foli, 01°14.66'N, 128°10.61'E, 1 specimen 25/10 mm [5125], st 217, rocky shore near a beach (UMIZ 00054). Philippines, Luzon, Batangas, Calatagan, 13°55.32'N, 120°37.26'E, 3 specimens 30/16 mm [3215], 29/16 mm [3212] and 26/12 mm [3210], st 183, rocks in Avicennia  and Rhizophora  mangrove (PNM 041221); Bohol, Maribojoc, 09°44.02'N, E 123°47.45'E, 6 specimens 36/20 mm [3266], 34/21 mm [3271], 33/18 mm [3265], 33/22 mm [3272], 32/20 mm [3277], and 30/17 mm [3270], st 191, uplifted coral rubble with sand (PNM 041222); Bohol, Mabini, 09°51.59'N, 124°34.16'E, 2 specimens 21/12 mm [3373] and 14/8 mm [3370], st 196, open Avicennia  and Sonneratia  mangrove with sand, and coral rubble (PNM 041223); Bohol, Guindulman, 09°44.06'N, 124°27.63'E, 2 specimens 38/15 mm [3624] and 22/13 mm [3629], st 197, rocks and coral rubble near a few Avicennia  trees (PNM 041216); Bohol, Loay, 09°36.23'N, 123°59.73'E, 1 specimen 33/19 mm [3634], st 198, mostly sand, and a few Avicennia  (PNM 041217); Bohol, Maribojoc, 09°44.02'N, 123°47.45'E, 2 specimens 29/16 mm [3393] and 19/12 mm [3404], st 200, coral rubble with sand, at night (PNM 041218); Bohol, Maribojoc, 09°44.28'N, 123°49.39'E, 4 specimens 37/17 mm [3420], 33/23 mm [3406], 26/16 mm [3405] and 21/11 mm [3408], st 202, uplifted coral rubble with sand and algae, near Sonneratia  trees (PNM 041224).


Indonesia: Bali, Edam (near Jakarta), Halmahera, Kei Islands (type locality of O. keiense  ), Lombok, Seram, Sulawesi, and West Papua (type locality of O. ater  ). Philippines: Bohol, Luzon, and Mindanao. All records are new except for the type localities as well as the presence of O. ater  in Edam and Mindanao ( Hoffmann 1928: 81).


(Figs 34-35, Table 3). Wallaconchis ater  is found in the intertidal on coral rubble and small stones. It is often in patches of mangrove trees with coral rubble (Fig. 34), but may also be found in intertidal regions without mangrove trees (Fig. 35).


(Table 5). Wallaconchis ater  cannot be distinguished from other Wallaconchis  species based on external features. Grey or brown specimens cannot be distinguished from any other species, and brightly colored specimens cannot be distinguished from W. nangkauriense  or W. graniferum  . Internally, the large, coiled penis of W. ater  with projections at its tip is quite peculiar and is diagnostic.

Color and morphology of live animals

(Figs 36-37). In sandy habitats, sand grains may be stuck to the dorsal notum. The dorsal coloration is highly variable, and often a mottling of two or three colors, of which the most common are brown, black, green, red, grey, and yellow. In some individuals, many small yellow dots are present on the dorsal notum. The color of the ocular tentacles may be yellow-orange, light brown or reddish brown. The hyponotum is cream colored, yellow-orange, yellow-grey or grey. The foot is yellow-grey, yellow-orange, or grey. The lateral sides of the foot may be the same color as the pedal sole (for example, Fig. 37H) or occasionally dark grey (Fig. 37D).

External morphology.

Between six and 18 papillae bear dorsal eyes (three or four per papilla). There is a retractable papilla with eyes in the center of the dorsal notum, which may be slightly raised above the dorsal surface.

Digestive system

(Fig. 38, Table 4). Each radular row contains a rachidian tooth and two half rows of lateral teeth. Examples of radular formulae are presented in Table 4. The length of the rachidian teeth is approximately 20-25 µm, significantly smaller than that of the lateral teeth. The length of the hook of the lateral teeth gradually increases, from 40 to 70 µm, from the inner to the outer teeth (excluding the innermost and outermost lateral teeth which are significantly smaller). The intestinal loops are of type I.

Reproductive system

(Fig. 39). Posteriorly, the oviduct is larger than the deferent duct and is especially wide distally. The spermatheca is spherical and enters the distal end of the oviduct through a short duct. In small specimens (less than 17 mm long) female reproductive organs are small, with a narrower oviduct.

Copulatory apparatus

(Figs 40-42). The penis is smooth. It does not bear any hooks. In mature specimens (> 22 mm long), it is tightly coiled (Fig. 42C), with approximately eight to 15 loops in the coil (Figs 40A, B, 41). However, the number of loops in the coil is correlated with the body length (and sexual maturity) and there are fewer (less than five) or no loops in shorter (< 22 mm long) and less mature specimens (Fig. 40D). When the tip of the penis is evaginated, it is tapered distally and bears three pointed projections (Figs 40A, 41A, 42A, B). The penis is enclosed within the vestibule (Figs 40C, 41B), and the coil may form a U-shape within the vestibule (Fig. 41A). The penis is sometimes longitudinally folded and it appears that its loops could expand in diameter (cross-section of penis, Fig. 42D). The vestibule is exceptionally large (it can be nearly half the length of the body cavity). The penial sheath is long and usually forms a loop within the body cavity. The deferent duct is exceptionally narrow and convoluted, and only becomes wider distally in the anterior region of the body cavity (Fig. 40). In small specimens, the deferent duct is less convoluted than in larger (and more mature) specimens. The retractor muscle is short (approximately 2 mm) and inserts on the posterior body wall, on the right side of the rectum.


Lesson’s original description of Onchidium ater  was brief, mostly based on the external morphology, and lacked illustrations of the internal anatomy. Fortunately, some organs remain in the syntypes which display the diagnostic characters of Wallaconchis  (intestinal loops of type I and no rectal gland).

The male parts were removed from both syntypes by Labbé when he re-described them for his 1934 monograph. Therefore, only Lesson’s original description of the male parts and their re-description by Labbé can be used to determine the application of the name O. ater  . Lesson (1830: 300, our translation from French) describes the penis as a "very elongated, cylindrical, twisted upon itself, and very contractile tube in the anterior part of the body." Also, Labbé’s (1934: fig. 30) illustration of the penis of the syntypes of O. ater  reveals that it consists of a coil of tight loops, which perfectly matches the penis of the species described here. In addition, the wide oviduct in the syntypes is consistent with this species. As a result, we apply the name O. ater  to the species described here.

Labbé (1934: 206) also described "feathery gills" in the two syntypes of O. ater  , which, as a result, he transferred to the genus Scaphis  . Labbé commonly made surprising mistakes, describing features in specimens in which they were clearly not present. In this case, there are no gills on the dorsal notum of the syntypes of O. ater  . Labbé also described a penial accessory gland in the syntypes of O. ater  . Because the male parts are missing ( Labbé removed them), it is something that we cannot verify. However, given that there is no known onchidiid species in any other genus with this type of penial anatomy, Labbé’s description of an accessory penial gland is regarded as one of his numerous mistakes. Because of the errors he made when he re-described the two syntypes of O. ater  , only Labbé’s (1934: fig. 30) illustration of the penis is cited as a description of W. ater  in the list of references above.

The unique combination of characters observed on the lectotype of Onchidium keiense  (intestinal loops of type I, no rectal gland, male opening below the right tentacle, and no accessory penial gland) indicates that O. keiense  belongs to Wallaconchis  . The re-examination of the lectotype and most paralectotypes available for O. keiense  revealed no difference with the two syntypes of O. ater  for the penial anatomy and the enlarged oviduct, therefore O. keiense  is identified here as a junior synonym of W. ater  . However, not all paralectotypes of O. keiense  are part of W. ater  : at least one paralectotype of O. keiense  belongs to the genus Peronia  (due to the presence of an accessory gland and a different intestinal type). The designation of the lectotype makes it clear that the name O. keiense  applies to the species described by Hoffmann without an accessory gland.

Hoffmann (1926: 23) wrote that O. keiense  was very close to O. ater  , but he was not convinced that the two were the same species because he thought that the cylindrical "organe excitateur" that Lesson described could have either been the penis or an accessory penial gland. If Hoffmann had been able to examine the syntypes of O. ater  , he would have seen that the penial morphology is identical to O. keiense  . Hoffmann’s description of O. keiense  is consistent with Wallaconchis ater  , except for the description of dorsal eyes. The dorsal notum of W. ater  bears many papillae with three or four dorsal eyes on each papilla, while Hoffmann described 12 large papillae on the dorsal notum of O. keiense  with one dorsal eye each, and the central papillae with three or four eyes. Although the papillae are retracted in the lectotype and many paralectotypes, the presence of three or four dorsal eyes on all visible papillae was confirmed.

Hoffmann (1928: 81) examined additional specimens (he does not indicate how many) from Mindanao (Philippines) and Edam (a small Indonesian island near Jakarta) which he identified as O. keiense  in his subsequent revision of the Onchidiidae  . Hoffmann did not comment on the anatomy of these additional specimens (which were not examined for the present study). However, given that he is the original author of O. keiense  , it can be assumed that he recognized the distinct penial anatomy of this species. Mindanao is within the geographic range of W. ater  . However, the presence of W. ater  in Edam slightly expands to the west the geographic range delineated here based on our collections and expands the known distribution of W. ater  .

Hoffmann (1926: 24, our translation from German) considered creating a new genus for Onchidium keiense  : "The peculiarity of the penis could almost suggest the idea that we are dealing here with a whole new genus. In the genus Onchidium  [spelled Oncidium  ], however, there are already species which differ quite considerably from each other, so that I have no reason to create a new genus for my species." Hoffmann recognized the similarity between some Onchidium  species transferred here to Wallaconchis  (i.e., O. buetschlii  , O. nangkauriense  , and O. ovale  ), but he did not comment on the similarity between O. keiense  and these species. However, in his identification key, Hoffmann (1928: 109-110) listed O. keiense  in the same part of the key as the Onchidium  species transferred here to Wallaconchis  , using exactly the same characters: no accessory penial gland, no rectal gland, and intestinal loops of type I. So, even though Hoffmann showed in his identification key that those species are similar, he did not create or name any group for them. Also, in that same part of the key, Hoffmann listed O. papuanum  and O. palaense  . He must have assumed that the intestinal loops in these two species are of type I because there is no indication in the original descriptions that their intestinal loops are actually of type I and Hoffmann did not comment on the type material (which is lost for both species). However, the position of the male opening in the original descriptions of O. papuanum  and O. palaense  (to the left of right tentacle) indicates that these two names do not apply to Wallaconchis  species.

Hoffmann (1926:23) wrote that W. keiense  seemed to be like Onchidium cinereum  Quoy & Gaimard, 1832, but his comparison was based on Semper’s (1880: pl. 20, fig. 11, pl. 23, fig. 13; 1882:286) description of new specimens from Tonga-tabu [Tongatapu Island, Tonga] which he received from the Museum Godeffroy, instead of Quoy and Gaimard’s original type material (from Tonga). The type material of O. cinereum  could not be located. Onchidium cinereum  should likely be regarded as a nomen dubium because and it is unclear to which genus it belongs. Hoffmann also found an enlarged oviduct in Onchidium aberrans  Semper, 1882 similar to the oviduct found in O. keiense  , but O. aberrans  does not belong to Wallaconchis  as it lacks the diagnostic characters of Wallaconchis  .

Hoffmann did not illustrate the coiled penis of O. keiense  (the penial complex was illustrated with the vestibule and did not show the loops inside), which made it difficult for others to identify the diagnostic character of O. keiense  . Labbé did not recognize the similarity between the syntypes of O. ater  which he examined and Hoffmann’s description of O. keiense  . Labbé moved O. keiense  to his genus Paraoncidium  Labbé, 1934, which he created for a series of Onchidium  species with no accessory gland and no rectal gland, but he did not examine any new material for O. keiense  . Note that Paraoncidium  is a junior synonym of Onchidina  ( Dayrat and Goulding 2017).

Another species, Onchidium ferrugineum  Lesson, 1830 was described from the same type locality as O. ater  (Manokwari, West Papua, Indonesia). The number of syntypes was not included in Lesson’s original description, but Labbé (1934: 214) indicates that he examined four syntypes, one of which was "completely emptied of its viscera." There are now only three syntypes left in the jar (36/25 mm, 35/19 mm, and 30/18 mm), suggesting that one of the syntypes was lost (MNHN 22951). Lesson’s (1830: 301) description of the penis of O. ferrugineum  as cylindrical and very twisted is remarkably similar to his description of the penis of O. ater  . However, Lesson also clearly specifies that gills are present on the dorsal notum. A re-examination of the three syntypes of O. ferrugineum  shows that they are part of two different genera: the largest syntype (36/25 mm) bears gills (only found in species of the genus Peronia  ) while the two other syntypes do not. To clarify the application of O. ferrugineum  , the largest syntype with gills is designated here as the lectotype (and now clearly labeled in the jar). Therefore, the name-bearing type of O. ferrugineum  is part of a Peronia  species. Both paralectotypes display the diagnostic characters of Wallaconchis  , and the penis left in one of the paralectotypes is identical to the large, coiled penis of W. ater  and W. keiense  . However, because the paralectotypes no longer have any name-bearing function, O. ferrugineum  applies to a Peronia  species and cannot apply to a Wallaconchis  species. Because Labbé’s re-description is based on specimens from two different species (and two different genera), only Labbé’s (1934: fig. 50) illustration of the penis of a paralectotype of O. ferrugineum  is cited as a description of W. ater  in the list of references above.

Bretnall (1919) translated Lesson’s description of O. ater  but did not examine any new material. Gray (1850) and Adams and Adams (1858) mentioned the name Oncidiella nigra  Lesson, but, as Tapparone-Canefri (1883) first suggested, Lesson did not describe a species with this name, and these authors likely made the error of using the name O. nigra  for O. ater  (both ater  and nigra  mean black in Latin). Gray (1850) did not include a description to accompany the name O. nigra  , but included an illustration (pl. 181, fig. 7) of the dorsal notum of an animal which could be a Wallaconchis  species but cannot be positively identified. Adams and Adams (1858) only listed the name O. nigra  without commenting on it. Finally, Hoffmann (1928) and Labbé (1934) adopted Tapparone-Canefri’s conclusion that O. nigra  was mistakenly used to refer to O. ater  .