Laspionchis Dayrat & Goulding

Dayrat, Benoit, Goulding, Tricia C., Khalil, Munawar, Comendador, Joseph, Xuan, Qu ảng Ngo, Tan, Siong Kiat & Tan, Shau Hwai, 2019, A new genus of air-breathing marine slugs from South-East Asia (Gastropoda, Pulmonata, Onchidiidae), ZooKeys 877, pp. 31-80 : 41-42

Genus Laspionchis Dayrat & Goulding gen. nov.

Type species.

Laspionchis boucheti , designated here.

Etymology.

Combination of láspi, a Greek word meaning mud, and onchis, a word derived from the Greek ὁ ὂγκος (mass, tumor) and used in the past for onchidiid slugs. Laspionchis conveniently refers to those onchidiid species that always live on mud and are covered with a thin layer of mud.

Gender.

Gender masculine of onchis (ICZN Art. 30.1.1), a word derived from the masculine Greek word ὁ ὂγκος.

Diagnosis.

Body not flattened. No dorsal gills. Dorsal eyes present on notum. Retractable, central papilla (usually with four dorsal eyes) present, often raised above dorsal surface. Eyes at tip of short ocular tentacles. Male opening below right ocular tentacle (or below it and very slightly to its left). No transversal protuberance on oral lobes. Foot wide. Pneumostome median, on ventral hyponotum. Intestinal loops exactly between types I and II (with a transitional loop on average descending at 6 o’clock). Rectal gland absent. Accessory penial gland present with a hollow spine and a muscular sac. Penis with hooks: numerous, densely arranged next to each other, and pointed.

Remarks.

No external diagnostic feature unambiguously distinguishes Laspionchis from other onchidiid genera. Externally, Laspionchis slugs are especially difficult to distinguish from Paromoionchis slugs, which live in the same habitat (mud surface) and are often found together at the exact same sites. Also, for a non-expert, Laspionchis slugs could easily be confused with Peronina or Onchidium slugs, although those are characterized by distinctive, external features. However, Laspionchis is characterized by a unique combination of internal and external characters: no dorsal gills, male opening below the right eye tentacle (or below it and very slightly to its left), no rectal gland, intestinal loops between types I and II (i.e., with a transitional loop on average oriented at 6 o’clock), accessory penial gland present with a muscular sac, penis with numerous, pointed hooks densely arranged next to each other. According to our data, any onchidiid slug with this combination of characters belongs to Laspionchis .

Intestinal loops between types I and II, with a transitional loop on average oriented at 6 o’clock, could almost be regarded as diagnostic of Laspionchis slugs, acknowledging the existence of variation (both intra-specific and inter-specific). Indeed, in Laspionchis slugs, the transitional loop is normally oriented at 6 o’clock, even though, strictly speaking, its orientation actually varies between 5 and 7 o’clock ( Fig. 1 ). The intestinal loops of some individuals of other species can sometimes be characterized by a transitional loop oriented within that same range (between 5 and 7 o’clock), such as in species with intestinal loops of type I and a transitional loop oriented from 3 to 6 o’clock (as in Wallaconchis , see Goulding et al. 2018a), and in species with intestinal loops of type II and a transitional loop oriented from 6 to 9 o’clock (as in Paromoionchis , see Dayrat et al. 2019). However, the important difference here is that a transitional loop oriented at 6 o’clock is the norm in Laspionchis , while it is not the norm in those species from other genera.

A new generic name is needed because no existing name applies to the clade described here. Based on the examination of all the type specimens available in Onchidiidae (especially those of all the type species), a careful study of all the original descriptions (especially when no type specimens were available), and our ongoing taxonomic revision of every genus of the family ( Dayrat et al. 2016, 2017, 2018, 2019; Dayrat and Goulding 2017; Goulding et al. 2018a, b, c), it appears that there is no generic name of which the type species matches the diagnosis of this genus. For a recent review of the application of all existing generic names of Onchidiidae , see Dayrat et al. (2017: 1861).

Figures

Figure 1. Intestinal loops, dorsal view A, B Type I C, D Type II E-H Between types I and 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 I, with a transitional loop oriented at 3 o'clock, redrawn from Plate (1893: pl. 8, fig. 29) B Type I, with a transitional loop oriented at 3 o'clock, Wallaconchis sinanui (from Goulding et al. 2018: fig. 8 D) C Type II, with a transitional loop oriented at 9 o'clock, redrawn from Plate (1893: pl. 8, fig. 31) D Type II, with a transitional loop oriented at 9 o'clock, Paromoionchis tumidus (from Dayrat et al. 2019: fig. 12 A) E Between types I and II, with a descending transitional loop at 7 o'clock, holotype, Laspionchis boucheti, Australia, Northern Territory, [1688 H] (NTM P. 57614) F Between types I and II, with a descending transitional loop at 6 o'clock, L. boucheti, Australia, Northern Territory, [1681] (NTM P. 57612) G Between types I and II, with a descending transitional loop at 6 o'clock, L. boucheti, Vietnam, [5610] (ITBZC IM 00017) H Between types I and II, with a descending transitional loop at 5 o'clock, L. boucheti, Australia, Queensland, [2612] (MTQ). Scale bars: 1 mm (B), 2 mm (D, E), 5 mm (F-H).