Wallaconchis buetschlii (Stantschinsky, 1907)

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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Wallaconchis buetschlii (Stantschinsky, 1907)

comb. n.

Wallaconchis buetschlii (Stantschinsky, 1907)  comb. n. Figs 19, 20, 21, 22, 23

Onchidium buetschlii  Stantschinsky, 1907: 383-386, pl. 12, figs 10-12, pl. 13, figs 20a, 20b, 22, 35; Bretnall 1919: 316 (as Oncidium buetschlii  ).

Onchidium gracile  : Stantschinsky 1907: pl. 13, fig. 34 [non Onchidium gracile  Stantschinsky, 1907].

Type locality.

Australien: Queensland [Queensland, Australia]. Stantschinsky indicated that the syntypes were collected from the state of Queensland by Professor Simroth, but no detailed information about the locality is available in either the original description or the jar of the type material. Fresh material was collected from the type locality (see below, additional material).

Type material.

Lectotype, 19/17 mm, designated here (SMF 333595/2). The lectotype was dissected prior to the present study and its posterior end is missing. A lectotype is designated here because its remaining anterior, male parts can be used for species identification. The two other syntypes (30/22 mm and 30/29 mm) become paralectotypes (SMF 333595/2). Both paralectotypes were dissected prior to the present study and their male parts are missing. According to the original description, there were four syntypes, so one syntype has been lost or destroyed.

Additional material examined.

Indonesia, North Sulawesi, Wori, 01°36.06'N, 124°51.73'E, 2 specimens 31/14 mm [2120] and 27/14 mm [2122], st 84, old Sonneratia  and Avicennia  mangrove (UMIZ 00021); North Sulawesi, Bahoi, 01°43.36'N, 125°01.23'E, 1 specimen 22/18 mm [2189], st 85, sand and small rocks outside a mangrove (UMIZ 00022); North Sulawesi, Wori, 01°36.06'N, 124°51.73'E, 1 specimen 23/14 mm [2249], st 90, old mangrove forest with Avicennia  , Sonneratia  , and Rhizophora  , with rocks (UMIZ 00024); North Sulawesi, Mantehage Island, 01°41.88'N, 124°46.74'E, 1 specimen 32/22 mm [2310], st 91, rocks behind a mangrove of Sonneratia  and Rhizophora  (UMIZ 00025); Ambon, Haruku Island, 03°36.52'S, 128°25.07'E, 1 specimen 46/21 mm [2722], st 127, rocky Sonneratia  mangrove with coral rubble (UMIZ 00026); Ambon, Wai, 03°34.65'S, 128°19.53'E, 1 specimen 31/16 mm [2853], st 132, narrow band of old Avicennia  trees on sandy mud, old logs on ground (UMIZ 00027); Seram, 02°58.24'S, 128°07.07'E, 1 specimen 21/17 mm [2872], st 135, mud next to a mangrove (UMIZ 00028); Maluku, Kei Islands, Tual City, Fiditan, 05°35.96'S, 132°45.11'E, 2 specimens 30/16 mm [2928] and 30/15 mm [2933], st 144, rocks behind muddy mangrove of Rhizophora  (UMIZ 00029); Lombok, Don Don, 08°54.54'S, 116°21.50'E, 2 specimens 43/23 mm [2982] and 43/23 mm [2989] st 149, old, Avicennia  forest with coral rubble (UMIZ 00030); Bali, Gilimanuk, 08°10.16'S, 114°26.65'E, 1 specimen 24/15 mm [3123], st 156, sandy mudflat outside Rhizophora  and Avicennia  mangrove (UMIZ 00032); Bali, Pemuteran, Labuhan Lalang Harbor, 08°08.61'S, 114°32.33'E, 1 specimen 27/17 mm [3128], st 157, coral rubble, rocks and mud with a few Avicennia  (UMIZ 00033); North Maluku, Ternate, Bastiong, 00°46.41'N, 127°22.76'E, 1 specimen 32/19 mm [5016], st 203, muddy rocks near a mangrove (UMIZ 00034); Halmahera, Sofifi, 00°45.47'N, 127°35.90'E, 1 specimen 37/20 mm [5067], st 205, Sonneratia  mangrove (UMIZ 00035); Timor, Oesapa, 10°08.73'S, 123°38.10'E, 1 specimen 44/26 mm [5898], st 250, sandy area with Sonneratia  and Avicennia  (UMIZ 00072). Australia, Queensland, Cairns, Yule Point, 16°34.23'S, 145°30.58'E, 2 specimens 43/23 mm [2554] and 16/10 mm [2555], st 100, sand flat outside mangrove with dense Rhizophora  (st100, MTQ). Philippines, Mindanao, [no information on the collecting date], 1 specimen 28/20 mm, paralectotype of W. gracile  , [no information on the collector] (ZMB 103082b); Luzon, Batangas, Lian, 13°59.76'N, 120°37.43'E, 1 specimen 52/34 mm [3159], st 181, sandy, open Avicennia  forest (PNM 041209); Bohol, Guindulman, 09°44.06'N, 124°27.63'E, 1 specimen 31/25 mm [3631], st 197, rocks, coral rubble, and sand near a few Avicennia  trees (PNM 041210); Bohol, Loay, 09°36.23'N, 123°59.72'E, 1 specimen 35/20 mm [3637], st 198, mostly sand, and a few Avicennia  (PNM 041211); Bohol, Maribojoc, 09°44.28'N, 123°49.39'E, 2 specimens 36/17 mm [3409] and 18/13 mm [3410], st 202, coral rubble with sand and algae, near Sonneratia  (PNM 041212).


Australia: Queensland (type locality). Indonesia: Ambon, Bali, Halmahera, Kei Islands, Lombok, Seram, Sulawesi, and Timor. Philippines: Bohol and Luzon. All records, except the type locality, are new.


(Fig. 19, Table 3). Wallaconchis buetschlii  is found on firm mud or coarse sand in mangroves (i.e., mud which is not saturated in water) along with Wallaconchis uncinus  . It also lives on fine, sandy mud along with W. gracile  .


(Table 5). The slugs that are part of Wallaconchis buetschlii  are the largest of the genus (the largest live animal measured 60 mm). However, species cannot reliably be distinguished based on individual length. Red individuals cannot be distinguished from several species (usually W. nangkauriense  and W. ater  ), and grey or brown individuals cannot be distinguished from other species. Dorsal papillae with yellow tips can be prominent in W. buetschlii  , but also can be visible in other Wallaconchis  species (particularly in W. melanesiensis  ). In addition, the dorsal papillae with yellow tips found on the notum of W. buetschlii  are nearly identical to those on the notum of several species in other genera. The color of the hyponotum is helpful to distinguish W. buetschlii  (grey or yellow-grey hyponotum) from species in other genera (orange hyponotum) that live in the same habitat but is not fully reliable and should only be used with caution (i.e., the orange hyponotum in other onchidiids is occasionally a dull orange-grey similar to the yellow-grey hyponotum of W. buetschlii  ). As a result, W. buetschlii  cannot be reliably distinguished externally from other onchidiid species.

Internally, the penis is diagnostic of W. buetschlii  : it is not protected by a penial sheath or a vestibule and bears internal longitudinal ridges. The oviduct attached to the posterior wall of the visceral cavity is peculiar but it also occurs in W. gracile  . However, the penis of W. gracile  is protected by a penial sheath and extends into the vestibule.

Color and morphology of live animals

(Fig. 20). The dorsal coloration is variable. It is usually brown or grey, but occasionally brown with red or yellow patches, or even completely red. In some individuals, many small yellow dots are present on the dorsal notum. The color of the ocular tentacles also varies, and may be yellow-orange, brown, or reddish brown. The hyponotum color can be grey, light grey, or yellow-grey. The foot is also grey or yellow-grey. Crawling slugs tend to be elongated, but they contract when disturbed.

External morphology.

There are many papillae on the dorsal surface, which are usually bright yellow in color, or occasionally brown. Between six and 14 papillae bear eyes, with three or four eyes per papilla. There is a large, retractable papilla with eyes in the center of the dorsal notum, and it is often raised several millimeters above the dorsal surface.

Digestive system

(Fig. 21, Table 4). Examples of radular formulae are presented in Table 4. The length of the rachidian teeth is approximately 20 µm, significantly smaller than that of the lateral teeth. The length of the hook of the lateral teeth gradually increases, from 40 to 75 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. 22A). The distal region of the oviduct forms a loop, approximately 1/2 to 3/4 of a circle, attached by fibers of tissue to the inner wall of the visceral cavity (Fig. 22A). The oviduct is narrow and approximately of the same width as the deferent duct. The spermatheca is apple-shaped and joins the middle part of the oviduct through a short duct.

Copulatory apparatus

(Figs 22B, C, 23). The anterior, male copulatory apparatus exclusively consists of the deferent duct, the penis, and the retractor muscle of the penis. The penis, distal to the deferent duct, is a long and smooth tube, which can evaginate like a glove. It is not protected by a distinct penial sheath and, strictly speaking, there is no vestibule either. The penis is narrow proximally, widens gradually, with three longitudinal, internal ridges distally (one ridge shown in Fig. 23). In small individuals, the penis is narrow for its entire length. The relative length of the penis compared to that of the retractor muscle varies greatly, from both being of similar length to the penis being five times longer than the retractor muscle. The retractor muscle inserts near the rectum at the posterior end of the visceral cavity. In mature specimens, the deferent duct is thicker than the penis and convoluted distally (Fig. 22C). In immature individuals, the deferent duct is thinner, and less convoluted (Fig. 22B).


Stantschinsky’s Onchidium buetschlii  refers to a Wallaconchis  species because of the unique combination of characters of the lectotype (intestine of type I, no penial accessory gland, no rectal gland). Stantschinsky’s original description of the penis (confirmed by our examination of the lectotype) matches exactly the penial anatomy of the species described here. The unique attachment of the oviduct to the posterior body wall was not described by Stantschinsky but is clearly present in the lectotype as well. Because the male parts of the two paralectotypes of W. buetschlii  are missing, it cannot be confirmed that they are part of W. buetschlii  . The anatomy of the posterior (female) reproductive parts of the paralectotypes matches that of the lectotype (with an oviduct attached to posterior body wall), indicating that they could be part of either W. buetschlii  or W. gracile  .

The two syntypes used by Stantschinsky to describe Onchidium gracile  are part of two distinct species; therefore, one specimen is designated as the lectotype (see Wallaconchis gracile  ). The paralectotype of O. gracile  is part of W. buetschlii  . Both species share the unique attachment of the oviduct to the posterior body wall and are anatomically extremely similar. However, the penis (of the lectotype) of W. gracile  is within a penial sheath, while the penis (of the lectotype) of W. buetschlii  lacks a penial sheath. The penis of the paralectotype of W. gracile  matches perfectly that of (the lectotype of) W. buetschlii  . The written description of O. gracile  ( Stantschinsky 1907: 380-383) is confusing because it likely is a mix of both W. buetschlii  (paralectotype) and W. gracile  (lectotype). However, Stantschinsky’s (1907: pl. 13, fig. 34) illustration of O. gracile  matches the copulatory apparatus of the paralectotype and is thus an illustration of W. buetschlii  .

Hoffmann (1928) commented that O. buetschlii  is similar to Onchidium palaense  , but he did not list any new material for either species, and he does not seem to have examined the type material (he does not mention that he examined it). Semper’s description of the position of the male opening in O. palaense  as "between the two very small tentacles, almost in the middle between these" (1880: 276) differs from all Wallaconchis  species and indicates that O. palaense  does not belong to Wallaconchis  . The application of the name O. palaense  will be discussed in the revision of another onchidiid genus.

Labbé (1934) identified two specimens from New Guinea as Paraoncidium buetschlii  , but he also indicated they might be part of O. palaense  , both of which were originally described with no rectal gland. The lack of rectal gland combined with traits described by Labbé (intestinal loops of type I, no accessory penial gland) indicate that the specimens he examined are part of a Wallaconchis  species. However, Labbé’s brief description does not provide enough information to determine whether the specimens he examined are part of W. buetschlii  or another Wallaconchis  species without penial hooks. The fact that Labbé did not see any dorsal eyes was most likely due to preservation because dorsal eyes are present in all known Wallaconchis  species. Finally, Bretnall (1919) summarized Stantschinsky’s original description of W. buetschlii  but did not examine any new material.