Wallaconchis uncinus Goulding & Dayrat

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

Wallaconchis uncinus Goulding & Dayrat sp. n. Figs 13, 14, 15, 16, 17, 18

Type locality.

Indonesia, Ambon, Lateri, 03°38.26'S, 128°14.72'E, st 128, mudflat next to small creek in the low intertidal of mangrove preserve.

Type material.

Holotype, 22/17 mm [2751], designated here (UMIZ 00004).

Additional material examined.

Indonesia, North Sulawesi, Wori, 01°36.06'N, 124°51.73'E, 4 specimens 22/11 mm [2256], 22/16 mm [2250], 18/7 mm [2268], 17/7 mm [2261], st 90, old Avicennia , Sonneratia , Rhizophora mangrove forest with, rocks and dead logs (UMIZ 00005); Ambon, Lateri, 03°38.26'S, 128°14.72'E, 1 specimen 30/21 mm [2752], st 128, mudflat next to small creek and mangrove (UMIZ 00006); Ambon, Lateri, 03°38.24'S, 128°14.78'E, 1 specimen 28/17 mm [2843], st 131, muddy Rhizophora mangrove (UMIZ 00007); Bali, Pemuteran, Labuhan Lalang Harbor, 08°08.61'S, 114°32.33'E, 1 specimen 15/13 mm [3138], st 157, coral rubble, rocks and a few Avicennia (UMIZ 00008); North Maluku, Ternate, Bastiong, 00°46.41'N, 127°22.76'E, 1 specimen (24/11 mm [5056]), st 203, muddy rocks near a mangrove (UMIZ 00009); Halmahera, Sofifi, 00°45.47'N, 127°35.90'E, 2 specimens 25/16 mm [5070] and 22/16 mm [5029], st 205, Sonneratia mangrove (UMIZ 00010); Halmahera, Akelamo, 01°01.33'N, 127°39.09'E, 2 specimens 40/25 mm [5079] and 35/30 mm [5080], st 207, sandy-muddy beach at margin of mangrove (UMIZ 00011); Timor, Oesapa, Kupang City, 10°08.73'S, 123°38.10'E, 1 specimen 29/18 mm [5900], st 250, open Sonneratia mangrove (UMIZ 00071).

Distribution.

Indonesia: Ambon (type locality), Bali, Halmahera, northern Sulawesi, and Timor.

Habitat

(Fig. 13, Table 3). Wallaconchis uncinus predominantly lives on firm mud, in and around mangroves. It can also sometimes be found on rocks inside or adjacent to muddy mangroves. It lives in the low to mid-intertidal zone (i.e., not in higher and dry areas only submerged at the highest tides) but is not found on water-saturated mud (unlike onchidiid species in other genera). Wallaconchis uncinus frequently co-occurs with W. buetschlii . It was also found in the same microhabitat as W. sinanui but in much lower abundance (one individual of W. uncinus was found on a patch of mudflat amongst dozens of individuals of W. sinanui ).

Etymology.

From the Latin adjective uncinus meaning “hooked”, to refer to the distinctive hooks that the penis bears.

Diagnosis

(Table 5). Wallaconchis uncinus cannot be distinguished from other Wallaconchis species based on external features. Red individuals occur in at least three other species (i.e., W. nangkauriense , W. buetschlii , and W. ater ). Individuals of W. uncinus with orange and yellow bands could be confused with W. gracile or W. buetschlii , and these color patterns also occasionally occur in onchidiid species of other genera (personal observation). Brown individuals of W. uncinus cannot be distinguished from brown individuals of other Wallaconchis species. Internally, the flattened hooks (both the curved hooks and the rounded hooks) can be used for identification because they are not present in any other known onchidiid species.

Color and morphology of live animals

(Fig. 14). The dorsal color is variable but is often completely brown or brown mottled with dark orange or bright yellow. Occasionally, specimens are entirely red or black. The color of the hyponotum ranges from light grey to cream and orange in color. The color of the foot is yellow-grey or light grey. The brownish-orange ocular tentacles are short and extend for only a few mm beyond the margin of the notum when the animal crawls undisturbed.

External morphology

(Fig. 15 A–C). There usually are between six and 12 papillae with dorsal eyes (even though their exact number is difficult to determine because they can be retracted within the notum). Exceptionally, 23 papillae were observed in one preserved specimen from Halmahera (Fig. 15C). The female opening is posterior, located 3 - 5 millimeters from the anus (Fig. 15B) depending on the size of the animal (farther from the anus in larger animals). The male aperture is located below the right ocular tentacle (Fig. 15A)

Digestive system

(Figs 15D, 16, Table 4). Examples of radular formulae are presented in Table 4. The length of the main cusp 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 55 µm, excluding the innermost lateral tooth and several outermost lateral teeth, which are significantly smaller. The intestinal loops are of type I (Fig. 15D).

Reproductive system

(Fig. 17A). The middle portion of the oviduct is much wider than the proximal and distal ends (Fig. 17A). The spherical spermatheca connects to the narrow distal portion of the oviduct through a short duct.

Copulatory apparatus

(Figs 17 B–D, 18). The penial sheath is long: the length varies between 1/2 of the length of the visceral cavity to nearly the full length of the cavity. The vestibule is approximately 3 mm in length (in mature specimens). The vestibule is wider than the penial sheath and appears cylindrical or spherical depending on the orientation of the penis inside (Fig. 17B). Inside the vestibule, the penis can form multiple circular loops (Fig. 17D), a single loop, or simply be U-shaped. In mature specimens, the penis bears many large flattened hooks of two types: rounded hooks which lay flat on the surface of the penis and curved hooks which project perpendicularly from the surface of the penis (see hook labels, Fig. 18 B–D). In the distal region of the penis there may also be immature hooks which are not fully developed (Fig. 18A); these small hooks may also be seen in immature specimens, or they may be absent. The developed hooks differ between regions of the penis: in the distal region, the rounded hooks are spread around the penis; in the middle region, the rounded hooks form a single row (Fig. 18 A–B), some of these hooks being adjacent to a row of curved hooks; and, in the proximal region, rounded hooks are generally absent, but the curved hooks may be present. The deferent duct is highly convoluted with many loops (Fig. 17B) (though the deferent duct is significantly less convoluted in immature specimens, see Fig. 17C). The retractor muscle inserts posteriorly, on the body wall, near the rectum.