Research Article |
Corresponding author: John Slapcinsky ( slapcin@flmnh.ufl.edu ) Academic editor: Menno Schilthuizen
© 2016 John Slapcinsky, Fred Kraus.
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:
Slapcinsky J, Kraus F (2016) Revision of Partulidae (Gastropoda, Stylommatophora) of Palau, with description of a new genus for an unusual ground-dwelling species. ZooKeys 614: 27-49. https://doi.org/10.3897/zookeys.614.8807
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We describe a new stylommatophoran land snail of the family Partulidae from Palau. The new species has a combination of morphological and ecological characters that do not allow its placement in any existing partulid genus, so we describe a new genus for it. The new genus is characterized by a large (18–23 mm) obese-pupoid shell; smooth protoconch; teleoconch with weak and inconsistent, progressively stronger, striae; last half of body whorl not extending beyond the penultimate whorl; widely expanded and reflexed peristome; relatively long penis, with longitudinal pilasters that fuse apically into a fleshy ridge that divides the main chamber from a small apical chamber; and vas deferens entering and penial-retractor muscle attaching at the apex of the penis. Unlike all other partulids, the new species is strictly associated with rocks in contact with the ground. Comparing the other three Palauan species – currently assigned to Partula – to our new genus and to other partulids makes it clear that they require their own genus because their morphology is quite different from that of true Partula and from that of all other genera. Hence, we resurrect the name Palaopartula Pilsbry for these snails.
Land snail, Oceania, new species, Pacific, Palaopartula , Partula , pulmonate
The land-snail fauna of oceanic islands in the Pacific is disharmonic, with about 20 of the nearly 130 terrestrial snail families represented. Except for camaenid and bradybaenid species near the Asian and Australian continental margins (
More than 50% of all extinctions documented since 1500 are mollusks; nearly 40% of these are terrestrial snails from oceanic islands (
Palau harbors an estimated 200 species of land snails, of which only 78 have been described (
During a visit in 1998, one of us (FK) discovered an unusual stylommatophoran snail of moderate size that was not readily assignable to any genus known from the country. Subsequently, we discovered that the species had been collected previously by others and that specimens were already lodged at the Florida Museum of Natural History. In trying to identify these specimens we confirmed that they were morphologically distinct from any known Pacific-island species. Herein we provide evidence for their familial assignment to Partulidae and describe a new genus and species for these specimens. In comparing this snail to its closest relatives it became obvious that Palauan snails currently assigned to Partula in fact do not accord well morphologically with that genus. Furthermore, they have been found to comprise a separate clade of partulids evolutionarily independent of lineages that are properly assigned to Partula (
We hand-collected specimens, drowned them overnight, and preserved them in 75% ethanol. We dissected pallial organs, genitalia, and buccal masses from specimens under 75% ethanol using a dissecting microscope, and we isolated radulae from buccal masses using a 3% sodium hypochlorite solution. We imaged radulae and jaws using a Field Emission-SEM, photographed genital anatomy, and drew pallial organs with the aid of a drawing tube. We used Helcion Focus software for photo stacking. We counted whorls from the suture of the first whorl to the body whorl (Fig.
We isolated genomic DNA from 1 cubic mm of foot tissue of the new taxon using a solution of 10% Chelex beads (Bio-Rad Laboratories) in sterile water heated to 65 °C for 4 hours. DNAses and other protein contaminants were digested using Proteinase K. We amplified a 655-bp nucleotide fragment of cytochrome oxidase I (COI) with GoTaq DNA Polymerase (Promega, Madison, WI) using the primer pairs LCO1490/HCO2198 (
The familial placement of this new, unusual stylommatophoran species is not immediately obvious based on shell characters. The shell resembles some Camaenidae and Bradybaenidae, but these are precluded because the new species lacks a head wart, which is present in many camaenids (
Sphendone insolita sp. n.: A–C Shell, holotype,
The penis in Samoana, Palaopartula and Partula is divided into two chambers: a main chamber and an apical chamber that are usually defined by a constriction between them and by different sculpture.
Palaopartula
Pilsbry, 1909, in
Palaeopartula Richardson, 1990, page 6 [incorrect subsequent spelling].
Palaopartula Schileyko, 1999, page 271, figure 327.
Partula thetis Semper, 1865; by original designation.
Partula calypso, Partula leucothoe, and Partula thetis, all
Known only from Palau.
Shell large, elongate, with a tall, relatively flat-sided and acutely pointed spire (Fig.
Palaopartula has historically been grouped with Partula. It differs from Partula, Eua, and Samoana in having a relatively large and more elongate shell with a high and rapidly descending spire (Fig.
Apical sculpture of partulid genera: A Sphendone insolita sp. n., holotype,
This genus is isolated to the west of all previously named partulid genera (Fig.
Sphendone insolita sp. n.
One species, Sphendone insolita sp. n.
Shell obese-pupoid (Fig.
The shells of Eua, Samoana, Palaopartula, and Partula are not pupoid in shape; they are attenuated apically. The protoconch of the new species lacks strong spiral striae or pitting, unlike the strong striae of Eua, or the pitted striae of Palaopartula, Partula, and Samoana. Sphendone is similar only to Eua in the apical insertion of the vas deferens into the penis, unlike the lateral insertion into the apical chamber in Samoana, Palaopartula, and Partula (Figure
A comparison of a partial COI sequence (540 bp) of Sphendone (
Sphendone is a feminine Greek noun for a sling missile and is used here in reference to the unique bullet shape of the shell among partulids. The accent is on the first syllable.
Known only from Palau.
(n = 76). Palau: Ngeruktabel (Uruktapel) Island: along trail to German Lighthouse, 7.2600°N, 134.4493°W, F. Kraus, 24 August 1998 (
Palau: Eil Malk (Mecherchar) Island: southeastern peninsula, from hermit crab, F. G. Thompson, 22 October 1985 (
Large, obese-pupoid shell approximately 18–23 mm in height and 13–15 mm in width, with 4.5–5.1 whorls. Body whorl descends below the penultimate whorl. Protoconch sculptured with growth lines, strongest near the sutures; spiral sculpture lacking or, less commonly, comprising faint and irregular striae. Wavy spiral striae are progressively stronger and more regular on penultimate and body whorls but never become regular and strong. Peristome widely expanded and reflexed, palatal and parietal margins nearly parallel, base evenly rounded. Palatal margin with slight central thickening; parietal margin attaching to the body whorl at umbilicus. Penis long, with apical insertion of the vas deferens and retractor muscle. Approximately ten longitudinal pilasters coalesce to form a ridge that defines a small apical chamber below the insertion of the vas deferens.
Shell obese-pupoid, height 22.2 mm, width 14.0 mm, with 4.9 whorls (Fig.
Variation. Measurements of 56 adult shells: height 18.3–22.7 mm, mean 21.1 ± 0.8 mm; width 12.9–14.9 mm, mean 14.0 ± 0.4 mm; whorls 4.5–5.1, mean 4.9 ± 0.1. Aperture height 10.5–12.1 mm, mean 11.3 ± 0.4 mm. Aperture width 8.4–9.8 mm, mean 9.2 ± 0.3 mm. Most shells are similar to the holotype in coloration, but three of 79 shells are uniformly white. These white-shelled individuals have normal surface sculpture and are not worn. Nor are they albino, as evidenced by their normal mantle pigmentation. Most shells are dextral, but two of 79 are sinistral.
Pallial system (2 specimens). Nephridium nearly 2/3 length of pallial cavity, broad at base, tapering anteriorly, and sharply turned at renal orifice (Fig.
Radula (2 specimens). Central tooth two-thirds height of lateral teeth, trigonal, with poorly defined ectocones (Fig.
Jaw (1 specimen). Crescent-shaped, thin, stegognathous, composed of many narrow flat plaits that converge towards middle of cutting edge, which is not raised and does not bear a central cusp (Fig.
Reproductive system (10 specimens). Prostate gland short, extending only a short distance beyond albumen gland (Fig.
The new species differs from other partulids as stated for the genus.
The trivial name is a feminine Latin adjective meaning unusual, in recognition of both the unusual shell shape and ecological habits for a partulid.
Known only from southeasternmost Ngeruktabel (Uruktapel) and nearby Mecherchar (Eil Malk) Islands, Palau, Caroline Islands (Figs
Live individuals of the new species were collected only from beneath rocks, between soil and the overlying rock, or deep in rock piles. Dead shells were also found on the soil surface and in leaf litter among stones. The site is well-developed limestone rainforest (Fig.
Palau comprises more than 700 small islands at the western end of the Pacific Ocean, totaling 490 km2 of land and extending over 700 km, although the majority of islands lie within a single fringing reef approximately 130 km in length. These islands are situated some 800 km east of the Philippines and 850 km north of New Guinea and form the westernmost component of the Caroline Islands. They lie along the southern end of the Kyushu-Palau Ridge, a relict intra-oceanic volcanic-arc system the evolution of which ended 15–25 MYA (
Partulidae comprises more than 120 currently recognized species (
All known partulids, like many other Central Pacific taxa, including Microcystinae and some Achatinellidae, are ovoviviparous. Although ovoviviparous species may have an advantage colonizing islands (
Sphendone insolita is relatively common where found but may have specific habitat requirements that give it a limited and/or discontinuous distribution within Palau. Nearly all partulids are arboreal; however, a few species live on the ground in leaf litter – such as P. compressa and P. crassilabris – or in leaf litter and under stones – like P. producta (Pilsbry 1910). The new species is the only one associated with deep rock and boulder talus or found in crevices under and between rocks on the ground but not in surrounding leaf litter. Until further surveys better delimit this species’ range, populations should be considered spatially restricted, making this species potentially vulnerable to habitat modification such as deforestation or limestone mining. The habitat specificity, small range, and apparently slow rate of reproduction of this species should make this a species of special concern to land managers.
We thank Ron Crombie for providing GPS coordinates along the trail to the German lighthouse and for information on the type locality and Palau in general; Ron Leidich for kindly providing habitat photos; Don Cameron for advice on Greek etymological options; Taehwan Lee and Diarmaid O'Foighil for a copy of Yoshio Kondo’s thesis and information from their Partula study (
Eua expansa (Pease 1872): Samoa: Savaii Island, near Salailua, L. Price, November 1965 (
Eua zebrina (Gould 1846): American Samoa: Tutuila Island (
Palaopartula calypso
Palaopartula leucothoe
Palaopartula thetis
Partula affinis Pease 1868: French Polynesia: Society Islands: Tahiti Island, Faarumai, W. H. Pease (
Partula arguta Pease 1864: French Polynesia: Society Islands: Huahine Island, A. Garrett (
Partula auriculata Broderip 1832: French Polynesia: Society Islands: Raiatea Island, A. Garrett (
Partula caledonica Pfeiffer 1862: Vanuatu: Efate, Teouma Bay, along coast road, L. Price, 23 November 1972 (
Partula callifera Pfeiffer 1857: French Polynesia: Society Islands: Raiatea Island, A. Garrett (
Partula carteriensis (Quoy & Gaimard 1832): Papua New Guinea: New Ireland Province: St. Matthias Island, W. J. Eyerdam (
Partula citrina Pease 1866: French Polynesia: Society Islands: Raiatea Island, A. Garrett (
Partula crassilabris Pease 1866: French Polynesia: Society Islands: Raiatea Island, W. J. Clench (
Partula dentifera Pfeiffer 1853: French Polynesia: Society Islands: Raiatea Island, W. J. Clench (
Partula faba Martyn 1784: French Polynesia: Society Islands: Raiatea Island, A. Garrett (
Partula flexuosa Hartman 1885: Solomon Islands: New Georgia Islands, Gizo Island (
Partula formosa Garrett 1884: French Polynesia: Society Islands: Raiatea Island, Fatimu (
Partula fusca Pease 1866: French Polynesia: Society Islands: Raiatea Island, western Vaioara Valley (
Partula garretti Pease 1864: French Polynesia: Society Islands: Raiatea Island: W. H. Pease (
Partula gibba Ferussac 1821: Mariana Islands: Guam Island, W. H. Eshnaur (
Partula guamensis Pfeiffer 1846: Federated States of Micronesia: Pohnpei Island, W. H. Pease (
Partula hebe Pfeiffer 1846: French Polynesia: Society Islands: Raiatea Island: W. H. Pease (
Partula hyalina Broderip 1832: French Polynesia: Society Islands: Tahiti Island, A. Garrett (
Partula imperforata Pfeiffer 1877: French Polynesia: Society Islands (
Partula lugubris Pease 1864: French Polynesia: Society Islands: Tahiti Island, H. J. Armstrong (
Partula lutea Lesson 1831: French Polynesia: Society Islands: Bora Bora Island, W. H. Pease (
Partula macgillivrayi Pfeiffer 1855: Vanuatu (
Partula micans Pfeiffer 1853: Papua New Guinea, P. Dautzenberg (
Partula mooreana Hartman 1880: French Polynesia: Society Islands: Moorea Island, A. Garrett (
Partula navigatoria Pfeiffer 1850: French Polynesia: Society Islands: Raiatea Island, Western Vaioara Valley (
Partula otaheitana (Bruguiere 1789): French Polynesia: Society Islands: Tahiti Island, Faarumai Paune, W. H. Pease (
Partula planilabra Pease 1864: French Polynesia: Society Islands: Tahaa Island, A. Garrett (
Partula radiata Garrett 1884: French Polynesia: Society Islands: Raiatea Island, A. Garrett (
Partula radiolata Pfeiffer 1846: Mariana Islands: Guam Island, N side of Route 7, 5.0 mi E of Route 6, F. Kraus, 17 May 1995 (
Partula rosea Broderip 1832: French Polynesia: Society Islands: Huahine Island, A. Garrett (
Partula rustica Pease 1866: French Polynesia: Society Islands: Raiatea Island, W. J. Clench (
Partula similaris Hartman 1886: Papua New Guinea: Milne Bay Province: Woodlark Island, Guasopa, 9.2241°S, 152.9439°E, J. Slapcinsky, 23 January 2003 (
Partula suturalis Pfeiffer 1855: French Polynesia: Society Islands: Moorea Island, A. Garrett (
Partula taeniata Mörch 1850: French Polynesia: Society Islands: Moorea Island, A. Garrett (
Partula thalia Garrett 1884: French Polynesia: Society Islands: Raiatea Island, W. J. Clench (
Partula turneri Pfeiffer 1860: Vanuatu: Anatom Island (
Partula umbilicata Pease 1866: Samoa: Upolu Island (
Partula varia Broderip 1832: French Polynesia: Society Islands: Huahine Island, T. Dranga (
Samoana abbreviata (Mousson 1869): American Samoa: Tutuila Island: T. Dranga (
Samoana conica (Gould 1846): Samoa: Upolu Island, H. J. Armstrong (
Samoana fragilis (Ferussac 1821): Northern Mariana Islands: Rota Island, Water Cave, S. Bauman, 2 April 1996 (
Samoana ganymedes (Pfeiffer 1846): French Polynesia: Marquesas Islands (
Samoana inflata (Reeve 1842): French Polynesia: Marquesas Islands, A. Garrett (
Samoana strigata (Reeve 1850): French Polynesia: Marquesas Islands: Nuku Hiva Island, W. H. Pease (