Research Article |
Corresponding author: Ivaylo Dedov ( idedov@gmail.com ) Academic editor: Eike Neubert
© 2019 Ivaylo Dedov, Ulrich Schneppat, Manh Quang Vu, Nguyen Quoc Huy.
This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Citation:
Dedov I, Schneppat U, Vu MQ, Huy NQ (2019) A new semislug of the genus Laocaia (Gastropoda, Pulmonata, Helicarionidae) from Vietnam. ZooKeys 846: 19-30. https://doi.org/10.3897/zookeys.846.34372
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A new species of the genus Laocaia Kuzminykh, 1999, Laocaia simovi Dedov & Schneppat, sp. nov., is described, which was collected from a single locality in northern Vietnam. Color pictures of living specimens are provided. For the first time, information on the ecology and biology of a representative of the genus Laocaia is presented.
Helicarionidae, Laocaia, new species, Vietnam
The genus Laocaia was described by
Our finding of a third species strongly suggests that the genus has evolved in the ecological niches of the high altitudes of the Fansipan Mountain tops, and records of further new species of the genus can be expected in the future. The potential type locality of L. attenuata is situated only 3.5 km eastwards, and that of L. obesa can be found about 4.8 km in a southeast direction of the type locality of Laocaia simovi Dedov & Schneppat, sp. nov., on the same mountain massive. This indicates a high degree of endemism in a comparatively small area, which is in urgent need of further research. According to
The specimens were collected with an entomological standard sweep net from elevated branches of a leaf bearing tree of unknown species in the forest, on the eastern slope of the top of Fansipan Mountain (Fig.
The treatment of the specimens followed
Abbreviations: IBER-BAN – Institute of Biodiversity and Ecosystem Research, Bulgarian Academy of Sciences; NMNHS – National Museum of Natural History, Sofia, Bulgaria.
All measurements given are from specimens preserved in ethanol 75%. The total length and body width, mantle length and mantle width, length of free mantle flap, sole length and sole width, height and width of genital pore of the three adults of the series were measured. Maturity was determined prior to dissection by examining the genital pore under a binocular microscope. The general method of dissecting follows
Laocaia attenuata Kuzminykh, 1999.
small slugs with non-coiled visceral hump, rounded posteriorly, lying in V- shaped body groove; body cavity not extending into tail; shell very thin, non-spiral, internal, hemispheric, completely covering visceral hump, with small calcified part; penis short, bulbous, with large stimulator inside; epiphallus and flagellum absent; spermatheca entering atrium between vagina and penis (amended after
for the systematic position of the genus Laocaia, we here follow
VIETNAM: Lao Cai Province, Fansipan Mountain below peak, in monsoon influenced leaf-bearing mountain forest with dense undergrowth of bamboo, ca 2990 m; 22.30560°N, 103.77625°E; 21 Sep 2018; I. Dedov, N. Simov, R. Bekchiev, P. Beron leg.; NMNHS 10805, ex. coll. IBER-BAN 40339/1-A.
2 adults and 2 juveniles, same data as for holotype: NMNHS 10806, ex. coll. IBER-BAN 40339/1-E; coll. IBER-BAN, 40339/1: B, C, D.
The paratype IBER-BAN 40339/1-C is shown in the photos of the living semislug, as well as in all photos of the preserved animal and its anatomy.
Holotype: total length 24.12 mm, body width 6.72 mm, mantle length 15.96 mm, mantle width 6.72 mm, free mantle flap length 4.08 mm, sole length 24 mm, sole width 3.36 mm, tale length 8.28, tale width 2.52 mm, tale “horn” length 1.3 mm, tale “horn” width 1 mm, genital pore length 1.05 mm, genital pore width 0.25 mm (Fig.
Externally, L. simovi Dedov & Schneppat, sp. nov. differs from L. attenuata and L. obesa by its coloration. The anterior body of L. attenuata is yellow, and its head and neck show three indistinct stripes, while the mantle is marbled with irregularly arranged black spots. The posterior part of the foot is uniformly grayish. In contrast, the body of L. obesa is whitish-grayish colored and covered with numerous white spots. On the visceral hump, the mantle of this species displays a pattern of irregularly arranged black spots (
Anatomically, L. simovi sp. nov. differs from L. attenuata by the narrower base of the penis, as well as by its much more globular sarcobelum with a pointed, cone-shaped apical tip. The sarcobelum is not covered with numerous distinct papillae, but it shows very fine longitudinal striae. The striation is not well visible even under high magnification.
Laocaia simovi sp. nov. differs from L. obesa by its less voluminous penis and the narrower base of the penis. The inner wall of the penis is not covered with papillae, but with almost invisible, very fine granules. The bursa copulatrix of L. simovi sp. nov. is of almost globular shape, the pedunculus is long, slender and of the same diameter all along its length; its bursa copulatrix is more voluminous than the penis.
Coloration: The primary color of the anterior body is light-ocher-brownish. The head, including the ommatophores, is of a grayish-ocher color. The black eye spot on top of the ommatophores is contrasting and well visible. The “tale”, e.g. the posterior part of the foot is of a deep brick red color. This coloration continues anteriorly until the lower sides of the head, where it fades. The whole body shows a pattern of irregularly dispersed, white-yellowish and brownish-blackish spots and markings, which are also irregular in size, shape and placement between specimens. The brownish-blackish spots are missing on the neck and lower frontal sides of the body. The well pronounced dorsal edge of the “U” shaped dorsal groove behind the visceral hump is yellowish (Fig.
Body: The body (n = 3, adult specimens) is slender, elongated, and of comparatively small size and fits the known body dimensions of species within the genus Laocaia. The total length of preserved adult specimens is 21.12–26.40 mm. The body width is 5.76–6.72 mm. The visceral hump length is 11.52–15.96 mm. The visceral hump width is equal to the body width. The free mantle flap is 3.60–4.08 mm. In living animals, the integument of the anterior part of the body, including the mantle over the visceral hump, is very finely granulated, but looks smooth on the photo of a living specimen (Fig.
Shell: The vestigial shell is placed on the anterior roof of the visceral hump. The more calcified apical part of it is situated on the anterior part of the shell. The whole shell is found somewhat central right from the body axis. In other known vestigial shells, the small calcified part is situated apically. The thin seam of periostracum is posterior to the hard plate, rather than anterior to it in other Laocaia species. The apex is well distinguished and positioned almost centrally. The whole vestigial shell is completely covered with the mantle. It is difficult to extract it out of the shell-bed without damage. The shell is very thin and transparent. Under high magnification it is grainy, calcareous from ventral, except the much harder, triangulate, more massive calcified plate of creamy-white opaque color. The shell is without any remains of a helicoid apex, more like those, usually found in Limacidae, Agriolimacidae or Milacidae (Fig.
Anatomy of genital organs (Fig.
Laocaia simovi Dedov & Schneppat, sp. nov. genital anatomy, the whole sexual system (A), male part of the sexual system (B), sexual system, opposite view (C), position of the sarcobelum inside of the penis (D), and inverted (E). Abbreviations: p – penis; sb – sarcobelum, mrp – musculus retractor penis, vd – vas deferens, at – atrium, bc – bursa copulatrix, pd – pedunculus, ag – albumen gland, hg – hermaphroditic gland, hd – hermaphroditic duct.
♀-parts: Bursa copulatrix (bc) is big, almost spherical – length: 3.09 mm, width: 2.40 mm, with a relatively long pedunculus (pd) – length: 4.62 mm, width: 0.93 mm over its complete length. A spermatophore was not found in the pedunculus or bursa copulatrix. The albumen gland (ag) is very large and pale yellowish-white – length: 4.14 mm, width: 2.55–2.76 mm. The free oviduct (fod) is basally conical and then twisted and folded with approximate length of 3.7 mm and a width of 0.9–1.1 mm. It inserts to the atrium at almost the same position as the penis.
♂♀-parts: The atrium (at) is short and tubular. The hermaphroditic gland (hg) is big, relatively globular with a length of 3.6 mm and a width of 2.4 mm, gray-brownish and covered with a dense blackish, irregular connective tissue. The hermaphroditic duct (hd) is short, twisted and folded all along its length with a width of 0.54–0.6 mm. The spermoviduct (sod) is of 1.11–1.14 mm width.
Biological and ecological observations: Up to now, the species was found in epiphytic plant-groups, on elevated branches, in the tree crowns in the forests just below the Fansipan peak. If the animal is touched, it first tries to escape very fast, but if caught, the semislug takes a position with the head inverted and starts to wag its raised “tail” very fast from one side to the other, probably imitating land leeches (Hirudinea). This behavior can be interpreted to be a protective measure against predators, but also to flip itself down from twigs or leaves to the forest floor in order to escape a potential predator. Similar observations of rapid “tail movement” are published by
Up to now this species is known only from its type locality.
This new species is named after our friend and biologist Dr. Nikolay Simov, NMNHS, Sofia, Bulgaria, who found the first specimen of the species.
This study was financially supported by scientific and technological research authorities of the Ministry of Education and Training, Vietnam, Code: B2016- SPH-24. The authors would like to thank to the editor Dr. Eike Neubert and the reviewer Dr. Barna Páll-Gergely for their helpful remarks.