Laspionchis boucheti 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 : 42-52

publication ID

https://dx.doi.org/10.3897/zookeys.877.36698

publication LSID

lsid:zoobank.org:pub:ABBC811D-2A6D-4615-9ECF-0F44933BFBE1

persistent identifier

https://treatment.plazi.org/id/41EC4683-63DD-4C15-B3CA-F0FB6E543A33

taxon LSID

lsid:zoobank.org:act:41EC4683-63DD-4C15-B3CA-F0FB6E543A33

treatment provided by

ZooKeys by Pensoft

scientific name

Laspionchis boucheti Dayrat & Goulding
status

sp. nov.

Laspionchis boucheti Dayrat & Goulding sp. nov. Figs 8 View Figure 8 , 9 View Figure 9 , 10 View Figure 10 , 11 View Figure 11 , 12 View Figure 12 , 13 View Figure 13 , 14 View Figure 14 , 15 View Figure 15

Holotype.

AUSTRALIA • holotype, designated here, 30/20 mm [1688 H]; Northern Territory, Darwin, end of the Channel Island Road; 12°33.557'S, 130°52.894'E; 17 Aug. 2012; B Dayrat and party leg.; st 66, sequence of Sonneratia , Rhizophora , and Ceriops ; NTM P.57614.

Additional material examined.

AUSTRALIA - Northern Territory • 2 specimens 25/20 mm [1679], 35/25 mm [1681]; Darwin, near Channel Island Road; 12°34.979'S, 130°55.992'E; 16 Aug. 2012; B Dayrat and party leg.; st 65, sequence of Sonneratia , Rhizophora , and Ceriops ; NTM P.57612. • 1 specimen 16/10 mm [1685]; same collection data as for the holotype; NTM P.57613. - Queensland • 1 specimen 15/10 mm [2559]; Cairns, Yorkey’s Knob; 16°48.558'S, 145°42.768'E; 17 Jun. 2013; TC Goulding and party leg.; st 101, hard, red mud with grasses; MTQ. • 1 specimen 15/9 mm [2578]; Cairns, Yorkey’s Knob; 16°48.503'S, 145°42.869'E; 21 Jun. 2013; TC Goulding and party leg.; st 105, hard, red mud with grasses; MTQ. • 1 specimen 18/15 mm [2593]; Townsville, Magnetic Island; 19°09.733'S, 146°48.625'E; 24 Jun. 2013; TC Goulding and party leg.; st 108, very soft mud near creek, with some Rhizophora and Avicennia trees on sides; MTQ. • 1 specimen 16/15 mm [2604]; Townsville; 19°17.717'S, 146°49.487'E; 25 Jun. 2013; TC Goulding and party leg.; st 110, mangrove of short and dense trees; MTQ. • 2 specimens 21/14 mm [2609], 30/17 mm [2612]; Townsville, Ross River; 19°16.275'S, 146°50.284'E; 26 Jun. 2013; TC Goulding and party leg.; st 111, open forest of young Avicennia , very soft mud; MTQ. • 1 specimen 26/20 mm [2692], 30/17 mm [2693]; Mackay, Barnes Creek; 21°07.815'S, 149°11.396'E; 7 Jul. 2013; TC Goulding and party leg.; st 124, soft mud, open area with Avicennia and some Rhizophora , wetland restoration area; MTQ. BRUNEI DARUSSALAM • 2 specimens 31/20 mm [1037], and 14/8 mm [1038]; Pulau Pyatan, Teluk Brunei; 04°55.246'N, 115°02.764'E; 27 Jul. 2011; B Dayrat and party leg.; st 32, open mangrove with a few sparse old trees, and large old logs, by the river; BDMNH. INDONESIA - Sumatra • 1 specimen 15/10 mm [1729]; Tembilahan; 00°10.243'S, 103°27.982'E; 13 Oct. 2012; M Khalil and party leg.; st 76, mangrove of large Avicennia trees, with old logs, soft but solid mud, and Nypa on the margin; UMIZ 00112. MALAYSIA - Peninsular Malaysia • 1 specimen 20/10 mm [914]; Matang, facing fishermen’s village on the other side of river; 04°50.154'N, 100°36.368'E; 20 Jul. 2011; B Dayrat and party leg.; st 29, oldest and open Rhizophora forest of tall and beautiful trees, with hard mud, many creeks, and many old logs; USMMC 00054. • 1 specimen 12/8 mm [915]; Matang, off Kuala Sepatang, Crocodile River, Sungai Babi Manpus; 04°49.097'N, 100°37.370'E; 19 Jul. 2011; B Dayrat and party leg.; st 28, old and open Rhizophora forest with tall trees, hard mud, creeks, and many old logs; USMMC 00053. • 1 specimen 10/8 mm [5520]; Kuala Sepatang; 04°50.434'N, 100°38.176'E; 19 Jul. 2011; B Dayrat and party leg.; st 27, old forest with tall, old Rhizophora trees, high in the tidal zone (ferns), in educational mangrove preserve, at a creek lower in the tidal zone, with mud; USMMC 00052. PHILIPPINES - Bohol • 1 specimen 14/11 mm [3615]; Inabanga; 10°00.389'N, 124°03.522'E; 12 Jul. 2014; B Dayrat and party leg.; st 186, old, rehabilitated fish ponds next to a mangrove with some old Avicennia but mostly young Rhizophora trees; PNM 041252. SINGAPORE • 1 specimen 15/12 mm [1004]; Lim Chu Kang, 01°26.785'N, 103°42.531'E; 5 Apr. 2010; B Dayrat and party leg.; st 9, east of the jetty, open mangrove with medium trees, ending on mudflat outside mangrove with soft mud; ZRC.MOL.10483. • 1 specimen 10/8 mm [1005]; Pasir Ris Park; 01°22.840'N, 103°57.224'E; 30 Mar. 2010; B Dayrat and party leg.; st 5, mangrove forest with rich litter, lobster mounds, and old logs; ZRC.MOL.10482. VIETNAM • 2 specimens 31/20 mm [5609], 39/25 mm [5610]; Can Gio; 10°27.620'N, 106°53.316'E; 17 Jul. 2015; TC Goulding and party leg.; st 231, open mangrove with large Avicennia trees, soft mud, some old logs; ITBZC IM 00017.

Distribution

( Fig. 7 View Figure 7 ). Australia: Northern Territory, Queensland. Brunei Darussalam. Indonesia: Sumatra. Malaysia: Peninsular Malaysia. Singapore. Philippines: Bohol. Vietnam.

Habitat

( Fig. 8 View Figure 8 ). Laspionchis boucheti is found on mud, hard or soft, in open or dense mangrove forests. It is common across its entire distribution range.

Etymology.

Laspionchis boucheti is dedicated to Philippe Bouchet, professor of Malacology at the Muséum national d’Histoire naturelle, Paris, France, for the training that he generously provided to the first author as a graduate student at the MNHN, years ago, for kindly allowing us to study some material collected during expeditions that he organized (Kavieng, Madagascar, New Caledonia, Papua New Guinea, Vanuatu), and, more broadly, for his unconditional love of snails and slugs, biodiversity exploration, and alpha-taxonomy.

Diagnosis

(Table 3 View Table ). Externally, Laspionchis boucheti cannot be distinguished from L. bourkei . Internally, however, the insertion of the retractor muscle of the penis (at the posterior end of the visceral cavity) and the presence of additional, distal retractor muscle fibers can help distinguish L. boucheti from L. bourkei .

Color and morphology of live animals

( Figs 9 View Figure 9 , 10 View Figure 10 ). Live slugs are covered with mud and their dorsal color can hardly be seen. The background of the dorsal notum is brown, light to dark, homogenous or mottled with darker or lighter areas, and, occasionally, with red areas too. In some slugs, the tip of dorsal papillae (with and without dorsal eyes) can be yellow. The color of the foot is gray (light or dark), yellow, or orange. The hyponotum is light or dark grey, pale yellow or red, sometimes with a lighter whitish margin. The color of the foot and of the hyponotum of an individual can change rapidly, especially when disturbed. The ocular tentacles are brown (variable from light to dark) and short (a few millimeters).

Generally, the dorsal notum of any given slug can rapidly change from almost perfectly smooth to densely covered by many papillae. However, when slugs are not disturbed, the dorsum is usually covered by papillae of various sizes. In some slugs, larger papillae may be arranged in two longitudinal ridges on either side of the median line, but those ridges can appear and disappear rapidly. Some papillae bear dorsal eyes at their tip (most papillae bear three eyes). The number of papillae with dorsal eyes is variable (between 8 and 12, on average) and they mostly are on the central part of the notum. Their tip can be pale yellow, but not always. A central, much larger papilla, which also bears three dorsal eyes, is entirely retractable within the notum. In addition to the large papillae, the notum is covered by smaller, rounded papillae, which can make it look very granular.

External morphology

( Fig. 11A, B View Figure 11 ). The body is not flattened. The notum is oval. Dorsal gills are absent. The large, central, retractable papilla at the center of the notum can usually only be seen in live animals. In preserved specimens, it is retracted inside the notum. The hyponotum is horizontal. The width of the hyponotum relative to the width of the pedal sole varies among individuals. The width of the hyponotum is approximately half of its total width. In the anterior region, the left and right ocular tentacles are superior to the mouth. Eyes are located at the tip of the ocular tentacles. Inferior to the ocular tentacles, superior to the mouth, the head bears a pair of oral lobes. The latter are smooth, with no transversal protuberance. The male aperture (opening of the copulatory complex) is below the right ocular tentacle (or very slightly to its left in dorsal view). The anus is posterior, medial, close to the edge of the pedal sole. On the right side (to the left in ventral view), a peripodial groove is present at the junction between the pedal sole and the hyponotum, running longitudinally from the buccal area to the posterior end, very close to the anus. The position of the female pore (at the posterior end of the peripodial groove) does not vary much among individuals. The pneumostome is medial. Its position on the hyponotum relative to the notum margin and the edge of the pedal sole varies among individuals but it tends to be closer to the notum margin.

Visceral cavity and pallial complex.

The heart, enclosed in the pericardium, is on the right side of the visceral cavity, slightly posterior to the middle. From the anterior ventricle is an anterior vessel supporting several anterior organs such as the buccal mass, the nervous system, and the copulatory complex. The auricle is posterior. The kidney is more or less symmetrical, the right and left parts being equally developed. The kidney is intricately attached to the respiratory complex. The lung is in two left and right, more or less symmetrical, parts.

Digestive system

( Figs 12 View Figure 12 , 13 View Figure 13 ). There are no jaws. The left and right salivary glands, heavily branched, join the buccal mass dorsally, on either side of the esophagus. The radula is between two large postero-lateral muscular masses. Radulae measure up to 2 mm in length. Each radular row contains a rachidian tooth and two half rows of lateral teeth of similar size and shape. Examples of radular formulae are in Table 4 View Table . The rachidian teeth are unicuspid: the median cusp is always present; there are two inconspicuous lateral cusps ( Fig. 13A View Figure 13 ). The length of the rachidian teeth (ca. 20 µm) tend to be approximately half the size of the lateral teeth (ca. 50 µm). The lateral aspect of the base of the rachidian teeth is straight, occasionally slightly convex. The half rows of lateral teeth form an angle of 45° with the rachidian axis. With the exception of the few innermost and outermost lateral teeth, the size and shape of the hook of the lateral teeth do not vary along the half row, nor do they vary among half rows. The hook of lateral teeth is extended posteriorly by a tail-like structure attaching to the radular membrane and making the hook look longer. The tail-like structure (posterior hook extension, Fig. 13D View Figure 13 ) is especially obvious in the outermost lateral teeth as its length gradually increases along each half row. The lateral teeth seem to be unicuspid with a flattened and curved hook with a rounded or pointed tip, but there also is a pointed spine on the outer lateral expansion of the base (basal lateral spine, Fig. 13A View Figure 13 ). In most cases, that spine cannot be observed because it is hidden below the hook of the next, outer lateral tooth. It can only be observed when the teeth are not too close (such as in the innermost and outermost regions) or when teeth are placed in an unusual position. The length of the spine decreases along the half row such that outermost teeth may be characterized by reduced or no lateral spine. The inner and outer lateral aspects of the hook of the lateral teeth are straight (i.e., not wavy and not with a protuberance).

The esophagus is narrow and straight, with thin internal folds. The esophagus enters the stomach anteriorly. Only a portion of the posterior aspect of the stomach can be seen in dorsal view because it is partly covered by the lobes of the digestive gland. The dorsal lobe is mainly on the right. The left, lateral lobe is mainly ventral. The posterior lobe covers the posterior aspect of the stomach. The stomach is a U-shaped sac divided into four chambers. The first chamber, which follows the esophagus, receives the ducts of the dorsal and lateral lobes of the digestive gland. The second chamber, posterior, receives the duct of the posterior lobe of the digestive gland. The third chamber is funnel-shaped and lined by ridges internally. The fourth chamber is continuous and externally similar to the third. The intestine is long, narrow, and the intestinal loops are exactly between types I and II, i.e., with a transitional loop on average oriented at 6 o’clock, though the orientation of the transitional loop ranges between 5 and 7 o’clock ( Figs 1 View Figure 1 , 12 View Figure 12 ). There is no rectal gland.

Nervous system

( Fig. 11C View Figure 11 ). The circum-esophageal nerve ring is post-pharyngeal and pre-esophageal. The paired cerebral ganglia are close and the cerebral commissure is short (but its length does vary among individuals). Paired pleural and pedal ganglia are also all distinct. The visceral commissure is very short and the visceral ganglion is more or less median. Cerebro-pleural and pleuro-pedal connectives are short and pleural and cerebral ganglia touch each other on either side. Nerves from the cerebral ganglia innervate the buccal area and the ocular tentacles, and, on the right side, the penial complex. Nerves from the pedal ganglia innervate the foot. Nerves from the pleural ganglia innervate the lateral and dorsal regions of the mantle. Nerves from the visceral ganglia innervate the visceral organs.

Reproductive system

( Fig. 14 View Figure 14 ). Sexual maturity is correlated with animal length. Mature individuals have large female organs (with a large female gland mass) and fully-developed male parts. Immature individuals may have inconspicuous (or no) female organs and rudimentary anterior male parts. The hermaphroditic gland is a single mass, joining the spermoviduct through the hermaphroditic duct. There is a narrow receptaculum seminis (caecum) along the hermaphroditic duct. The female gland mass contains various glands (mucus and albumen) which can hardly be separated by dissection and of which the exact connections remain uncertain. The hermaphroditic duct becomes the spermoviduct. Proximally, the spermoviduct is not divided (at least externally) and is embedded within the female gland mass. Distally, the spermoviduct branches into the deferent duct and the oviduct. The free oviduct conveys the eggs up to the female opening and the exosperm from the female opening up to the fertilization chamber. The large, ovate-spherical spermatheca connects to the oviduct through a narrow and short duct. The oviduct is large (larger than the deferent duct) and straight. There is no vaginal gland.

Copulatory apparatus

( Figs 14C View Figure 14 , 15 View Figure 15 , 16 View Figure 16 ). The male anterior organs consist of the penial complex (penis, penial sheath, deferent duct, retractor muscle) and the accessory penial gland (flagellum, muscular sac, hollow spine). The penial complex and the accessory penial gland share the same vestibule and the same anterior male opening.

The penial sheath is narrow and elongated. The penial sheath protects the penis for its entire length. The beginning of the retractor muscle marks the separation between the penial sheath (and the penis inside) and the deferent duct. The retractor muscle is strong, shorter than the penial sheath, and inserts at the posterior end of the visceral cavity. In addition, there is a cluster of retractor muscle fibers on the distal part of the penial sheath, near the vestibule. The deferent duct is highly convoluted with many loops. Inside the penial sheath, the penis is a narrow, thin, elongated, hollow tube, with numerous and densely-arranged (next to each other) hooks in its distal part. Penial hooks are pointed and measure from 50 to 100 μm. When the penis is retracted inside the penial sheath, the hooks are inside the tube-like penis; during copulation, the penis is everted like a glove and the hooks are then on the outside.

The accessory penial gland is a long, tube-like flagellum with a proximal dead end. The length of the flagellum of the penial gland varies among individuals but it is always heavily coiled. Near its distal part, the flagellum is enlarged into a muscular sac. Distally, the flagellum ends in a hard, hollow spine protected by a sheath which opens into the vestibule. The hollow spine is narrow, straight, elongated. Its base is conical. Its diameter is ca. 50 μm except at the base where it is larger (ca. 100 μm). The diameter of the opening at the tip measures ca. 30 μm. Its length ranges from 0.7 mm [1037] (BDMNH) to 1 mm [2693] (MTQ). There is no disc separating the spine of the penial gland and the vestibule.

Remarks.

A new species name is needed because no existing name applies to the species described here, based on the examination of all the type specimens available in the Onchidiidae , a careful study of all the original descriptions, 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). Several problematic species names, already discussed in detail in our revision of Paromoionchis ( Dayrat et al. 2019: 68-72), are regarded as nomina dubia for a variety of reasons (the type locality is too vague, the original description is not informative enough, the type material is destroyed or lost). One of those nomina dubia, Onchidium palaense Semper, 1880 (type locality in Aibukit, Palau Islands) could belong to Paromoionchis or Laspionchis but its generic placement cannot be determined. Onchidium palaense does not belong to Onchidium because several traits mentioned by Semper, such as the absence of a rectal gland and of an accessory penial gland, are incompatible with Onchidium ( Dayrat et al. 2016). Onchidium palaense simply is a nomen dubium which was arbitrarily placed in the genus Onchidium and cannot reliably be placed in any of the onchidiid genera.