Setocallosa—a new genus and species of land snail from Arnhem Land, Australia (Stylommatophora: Camaenidae)

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Setocallosa—a new genus and species of land snail from Arnhem Land, Australia (Stylommatophora: Camaenidae) a

a

Francesco Criscione & Frank Köhler a

Australian Museum, 6 College St, Sydney, NSW 2010, Australia Published online: 14 Nov 2014.

To cite this article: Francesco Criscione & Frank Köhler (2014): Setocallosa—a new genus and species of land snail from Arnhem Land, Australia (Stylommatophora: Camaenidae), Molluscan Research, DOI: 10.1080/13235818.2014.911804 To link to this article: http://dx.doi.org/10.1080/13235818.2014.911804

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Molluscan Research, 2014 http://dx.doi.org/10.1080/13235818.2014.911804

Setocallosa—a new genus and species of land snail from Arnhem Land, Australia (Stylommatophora: Camaenidae) Francesco Criscione and Frank Köhler∗ Australian Museum, 6 College St, Sydney, NSW 2010, Australia

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(Received 23 December 2013; final version received 14 March 2014 ) The new, monotypic camaenid genus Setocallosa is described for the new species S. pathutchingsae from Arnhem Land, Top End of the Northern Territory. This camaenid is characterized by a combination of distinct morphological features, such as a small, weakly elevated shell with widely open umbilicus and thick callus on the parietal wall, a wide epiphallic flagellum, elongated penis and short bursa copulatrix with subglobose end. The relationships of Setocallosa with the other camaenid genera in the area are investigated by means of mtDNA, but its phylogenetic position remains ambiguous. S. pathutchingsae occurs in sympatry with Arnhemtrachia ramingining, but based on morphology the two camaenids can be readily differentiated. http://zoobank.org/urn:lsid:zoobank.org:pub:1C50CF24-7FEE-446A-9724-A0A4E850B5AA Keywords: anatomy; Australian Monsoon tropics; Helicoidea; morphology; Northern Territory; Pulmonata; taxonomy

Introduction North-western Australia supports a remarkably diverse and highly endemic fauna of camaenid land snails (e.g., Solem 1991). Based on observations of broader patterns of distribution and endemism amongst camaenids, three main regions are recognized in this part of the Australian Monsoon Tropics. With nearly 250 known species in seventeen genera, the north-western Kimberley in Western Australia harbours the largest diversity of Camaenidae. All of these species and most of these genera are endemic to this region (Solem 1991; Gibson and Köhler 2012). The second highest diversity is found further inland, in the East Kimberley and the adjacent Victoria River District in the Northern Territory. The camaenid fauna of this sub-humid to sub-arid region is also largely endemic and there is little overlap with the camaenid fauna from the more humid north-western Kimberley. In addition, this more xeric area supports lower species richness than more humid areas closer to the coast. Twenty-three genera were described from the East Kimberley and Victoria River District combined (e.g., Solem 1985; Criscione et al. 2012; Criscione and Köhler 2013a, 2013b; Köhler and Criscione 2013b) containing 50–60 species in total. Only three of these genera also occur in the NW Kimberley. Arnhem Land supports the least diverse and probably the least known camaenid fauna in north-western Australia. A total of five genera have been recorded from this region

(Solem 1979; Köhler 2012; Köhler and Criscione 2013a), three of which are monotypic (Arnemelassa Iredale, 1938, Parglogenia Iredale, 1938, Arnhemtrachia Köhler & Criscione, 2013). Two further genera known to occur in Arnhem Land are widely distributed throughout the monsoon tropics, Xanthomelon Martens, 1860 and Torresitrachia Iredale, 1939 (e.g., Iredale 1938, 1939). Land snail surveys in the Kimberley, Victoria River District, Pilbara and central to southern Australia undertaken since the late 1980s by various parties have been crucial to more comprehensive documentation of local land snail faunas. There has been no comparable effort to survey land snails in Arnhem Land and most available records stem from opportunistic collections. It is known that Arnhem Land harbours a distinct camaenid fauna, which again is characterized by endemism and little overlap with neighbouring regions. Camaenids living in this region often represent morphologically distinct, phylogenetically enigmatic but taxonomically impoverished groups. The three monotypic genera Arnemelassa (from East Arnhem Land), Arnhemtrachia and Parglogenia (from West Arnhem Land) may be taken as examples for such monotypic genera (Köhler 2012; Köhler and Criscione 2013a). These endemic taxa are characterized by genital anatomies that differ markedly from any other Australian camaenid, but their phylogenetic relationships have so far remained elusive (Köhler 2012). The present

∗ Corresponding

author. Email: [email protected] Supplementary data available online at www.tandfonline.com/10.1080/13235818.2014.911804 © 2014 The Malacological Society of Australasia and the Society for the Study of Molluscan Diversity

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Figure 2. Shell photographs (top, front and bottom view): A, Paratype C.462970; B, East Arnhem Land, Gove Peninsula, Nhulunbuy AM C477792. Scale bar = 10 mm.

Figure 1. Known occurrences of Setocallosa pathutchingsae n. sp. in Arnhem Land, Northern Territory: —type locality in West Arnhem Land, south of Ramingining. •—localities in East Arnhem Land, Gove Peninsula.

shown in (Köhler 2011: Fig. 2). Representative specimens from each collection site were dissected in order to study the genital anatomy by use of a Leica M8 stereo microscope with drawing mirror. Observations on the anatomy and measurements are reported in the taxonomic descriptions below. Here, references to size are intended as relative to other camaenid genera in the region. Molecular studies

work is based on the comparative study of museum samples from rainforest patches of two isolated localities in Arnhem Land (Fig. 1). Based on initial observations of shell features, these specimens were believed to represent one new species and one undescribed genus. The aim of this work is to confirm the identity of this putative taxon by means of comparative morphological and genetic analyses and to provide an appropriate taxonomic description.

Materials and methods Materials This study is based on dry shell material and ethanol preserved samples deposited in the Malacology Collection of the Australian Museum (Sydney, AM) and in the Museum and Art Galleries of the Northern Territory (Darwin, NTM).

Morphological studies Shell characters (dimensions, colouration, sculpture) were assessed from all adult shells. Adults were recognized by a complete apertural lip. Shell height (H = maximum dimension parallel to axis of coiling, including lip) and shell diameter (D = maximum dimension perpendicular to H, including lip) were measured with callipers precise to 0.1 mm. The number of whorls (W), including protoconch, was counted precise to 0.1 as

DNA was extracted from small pieces of foot muscle from up to four specimens per lot by use of a QIAGEN DNA extraction kit for animal tissue following the standard procedure of the manual. Fragments of the mitochondrial 16S rRNA (16S) and of the cytochrome c oxidase subunit 1 (COI) genes were amplified by PCR using the primer pairs 16Scs1 (Chiba 1999) and 16Sbd1 (Sutcharit et al. 2007) and L1490 and H2198 (Folmer et al. 1994), respectively. Reactions were performed with annealing steps of 90 s at 55◦ C for 16S and 60 s at 50◦ C for COI. Both strands of PCR fragments were purified and cycle sequenced by use of the PCR primers. Electropherograms were corrected for misreads and forward and reverse strands were merged into one sequence file using CodonCode Aligner v. 3.6.1 (CodonCode Corporation, Dedham, MA). Sequences have been deposited in GenBank (Table 1). Sequence alignments were generated using MUSCLE as implemented in MEGA5 (Tamura et al. 2011). Sequence saturation was assessed for each mtDNA fragment by using tests implemented in DAMBE (Xia et al. 2003). Uncorrected pair-wise genetic distances were calculated using MEGA5 under the option ‘pairwise deletion of gaps’. For phylogenetic analyses, 16S and COI sequences were concatenated into one partitioned data set. Prior to the model-based phylogenetic analyses, the best-fit model of nucleotide substitution was identified for each gene partition separately using the model proposal function of MEGA5. Partitioned models were applied in the BI analyses with parameters estimated from the data set. ML analyses were performed

New camaenid genus

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Table 1. Shell dimensions (mm) and whorl counts of Setocallosa pathutchingsae n. sp. from two different populations for N measured shells. Locality

N

H

D

W

Type locality

4

Gove Peninsula

20

All specimens

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3.6–4.5 4.0 ± 0.4 3.0–4.0 3.7 ± 0.2 3.5–4.5 3.8 ± 0.2

8.3–9.5 9.1 ± 0.5 7.5–8.5 8.0 ± 0.3 7.5–9.5 8.1 ± 0.5

3.9–4.3 4.2 ± 0.2 3.7–4.0 3.8 ± 0.1 3.7–4.3 3.9 ± 0.2

by employing the more complex model of sequence evolution to the entire data set as the program used did not allow for data partitioning. One-thousand ML bootstrap replicates were performed to assess the topology support of the ML tree. Bayesian posterior probabilities of phylogenetic trees were estimated by running a 106 generations Metropolis-coupled Markov chain Monte Carlo (2 runs with each 4 chains, of which one was heated) as implemented by MrBayes v. 3.2.1 (Ronquist and Huelsenbeck 2003). A data partition was applied that allowed parameters to be estimated separately for each gene fragment and for each codon position of the COI gene. Sampling rate of the trees was 1000 generations. Generations sampled before the chain reached stationary were discarded as burn-in. Stationarity was reached when the average standard deviation of split frequencies shown in MrBayes was less than 0.01 and the log likelihood of sampled trees reached a stationary distribution (Ronquist and Huelsenbeck 2003). Abbreviations 16S–16S ribosomal RNA gene; AM–Australian Museum, Sydney; AMT–Australian Monsoon Tropics; COI– cytochrome oxidase I gene; D–shell diameter; dry– number of dry shells; FMNH–Field Museum of Natural History, Chicago; H–shell height; Ht–Holotype; NT– Northern Territory; NTM–Museum and Art Galleries of the Northern Territory; Pt–Paratype; QM–Queensland Museum, Brisbane; W–number of shell whorls; WAM– Western Australian Museum, Perth; wet–number of ethanol–preserved specimen(s). Systematics Gastropoda Heterobranchia Stylommatophora Camaenidae Pilsbry, 1895 Setocallosa n. gen. Type species Setocallosa pathutchingsae n. sp.

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Description Shell. Small with almost flat spire and rounded periphery, deep suture. Umbilicus open, wide, not concealed by outer lip. Protoconch with fine microsculpture of tubercles. Teleoconch sculpture of growth lines and tubercles supporting short pointed periostracal projections (setae). Aperture simple, rounded; outer lip thin, not extending onto parietal wall but forming a thick callus. Reproductive tract. Typically camaenid with prostate and uterus being fused forming spermoviduct, bursa copulatrix lacking diverticulum and genitalia lacking stimulatory organs. Vas deferens reflexing apically into epiphallus. Epiphallus well developed, connected to penial interior through verge. Epiphallic flagellum with longitudinal pilasters. Penial sheath lacking. Inner penial wall with longitudinal pilasters. Penial retractor muscle originating from diaphragm, inserting on epiphallus. Bursa copulatrix short, with subglobose end, reaching spermoviduct.

Comparative remarks Setocallosa differs from other camaenids by a combination of distinct shell and genital characters which is not found in any other known camaenid genera. Genera from north-western Australia with a similarly small and flat shell with widely open umbilicus, no peripheral keel and no (or weak) axial ribs are Trachiopsis Pilsbry, 1893, Torresitrachia, Baudinella Thiele, 1931, Setobaudinia Iredale, 1933 and Kymatobaudinia Criscione and Köhler, 2013. The first two genera are represented in Arnhem Land, while the latter three genera are known from the Kimberley only. Nanotrachia levis Köhler and Criscione, 2013 from the East Kimberley also exhibits a similar shell. Shells of Trachiopsis differ mainly by a more expanded lip, generally raised at the parietal region, and absence of parietal callus. The callus is much weaker in Torresitrachia, N. levis, Setobaudinia, Baudinella and Kymatobaudinia, the latter four also having a much more expanded lip. Species of Kymatobaudinia and most species of Setobaudinia and Baudinella exhibit strong lip indentations, absent in Setocallosa. Most significantly, Setocallosa differs from all the above mentioned camaenids with similar shells by peculiar features of its reproductive system, such as lack of penial sheath, co-occurrence of a wide epiphallic flagellum, well-developed verge and a relatively short bursa copulatrix. Flagellum and verge also cooccur in Retroterra Solem, 1985, Trachiopsis and Setobaudinia; but in all these genera the bursa is much longer and exhibits a significantly different shape; a well-developed sheath is also present in the latter two genera.

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Figure 3. Scanning electron micrographs of shell sculpture of Setocallosa pathutchingsae, paratype NTM P48941. A, Protoconch viewed from above. B, Sculpture on teleoconch whorls viewed from above. Scale bars: A = 500 μm; B = 1 mm.

Etymology In reference to the periostracal projections present on the shell surface and the thick parietal callus; derived from the Latin word ‘seta’ (= hair) and the Latin word ‘callus’ (= callus). The prefix ‘Seto-’ has been employed for another Australian camaenid genus (Setobaudinia), whose species exhibit conspicuous periostracal projections; noun of feminine gender. Setocallosa pathutchingsae n. sp.

Holotype Australia, NT, Top End, West Arnhem Land, S of Ramingining, vine thicket near the edge of the plateau, rocky ground, under rocks., 12◦ 41 8 S, 134◦ 49 15 E (Kessner, 02 July 2007); (NTM P48940).

Paratypes Same data as holotype, 1 dry, 4 wet (NTM P48941), 2 wet (AM C.462970).

Supplementary non-type material Australia, NT, Arnhem Land, Gove Peninsula, Nhulunbuy: Turtle Beach, littoral rainforest, in leaf litter, 12◦ 18 46 S, 136◦ 55 53 E (24 August 2007), (AM C.477788); Pisonia forest, sand dune forest, sand and limestone, 12◦ 18 49 S, 136◦ 55 55 E (24 August 2007), (AM C.477793); Dhimurru Indigenous Protected Area (IPA), Mosquito Creek, gallery rainforest with Melaleuca, dunes, 12◦ 25 38 S, 136◦ 50 05 E (25 August 2007) (AM C.477792); swale rainforest, 12◦ 25 41 S, 136◦ 49 49 E (25 August 2007) (AM C.477790); 12◦ 25 44 S, 136◦ 49 54 E (S. Laidlaw, 23 August 2007) (AM C.477791); Daliwuy (= Daliwoi) Bay Rd, ca 2 kms SW of Macassan Beach, monsoonal rainforest, 12◦ 19 56 S, 136◦ 55 31 E (26 August 2007) (AM C.477794).

Description Shell (Figs. 2–3). Rather small (Table 1), with strongly depressed spire, rounded periphery, deep suture. Umbilicus open, wide, not concealed by outer lip. Protoconch microsculpture of dense tubercles, arranged in regular spiral rows. Teleoconch sculpture of dense growth lines and spiral rows of well-spaced tubercles, particularly prominent below suture. Tubercles supporting setae, eroded in early whorls. Aperture simple, rounded, without nodes; outer lip thin, forming a thick callus on parietal wall, weakly expanded. Colour light brown. Reproductive tract (Fig. 4). Vas deferens reflexing apically into epiphallus. Epiphallus well developed, connected to penial interior through verge. Epiphallic flagellum wide, twice as long epiphallus with four, regular, longitudinal pilasters. Penis without penial sheath. Penis elongated, not coiled, inner penial wall with well developed, slightly undulating longitudinal pilasters. Penial retractor muscle long, originating from diaphragm, inserting on distal third of epiphallus. Bursa copulatrix short, with subglobose end, reaching second third of spermoviduct.

A

B

Figure 4. Genital anatomy of Setocallosa pathutchingsae, holotype NMT P48940. A, Genital system. B, Penial anatomy. Abbreviations: al—albumen gland; at—atrium; bc—bursa copulatrix; ep—epiphallus; ef—flagellum; fo—free oviduct; fp—flagellic pilasters; hd—hermaphroditic duct; lp—longitudinal pilasters; p—penis; pv—penial verge; rm—retractor muscle; so—spermoviduct; tb—tubercles; va—vagina; vd—vas deferens.

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New camaenid genus Remarks The species is known from a few museum samples from localities that are a considerable distance from each other. The only living material was collected at the type locality, south of Ramingining. In addition, the species is reported from the Gove Peninsula, about 150 km east from the type locality (Fig. 1). These two geographically isolated populations reveal consistent shell morphology, but shells from the Gove Peninsula appear significantly smaller (Fig. 2B; Table 1). Due to its dependence on environmental factors, shell size is not commonly considered a good predictor of taxonomic differentiation (Solem 1985; Criscione et al. 2012; Criscione and Köhler 2013a). The scattered distribution records are presumably an artefact of poor sampling and are probably not indicative of a fragmented distribution of this species. Thus, following a conservative approach we consider all populations to be conspecific. A different conclusion could be attained if live-collected material from the Gove Peninsula was available in the future and its examination would reveal considerable molecular and anatomical divergence. The type locality of S. pathutchingsae is also the type locality for Arnhemtrachia ramingining Köhler and Criscione, 2013. Shells of both species were also found in all sample localities within the Gove Peninsula. The two species have a similar shell size, but shells of S. pathutchingsae differ mainly by having periostracal projections and by lacking peripheral keel and axial ribs. The features of their reproductive anatomy also differ conspicuously. S. pathutchingsae exhibits an epiphallic flagellum and a verge, absent in A. ramingining, and its bursa copulatrix is a much shorter. Etymology For Patricia (Pat) Hutchings, in recognition of her support in difficult times.

Molecular phylogenetics Phylogenetic trees were reconstructed by analysing a dataset of concatenated sequences of mitochondrial COI and 16S fragments. These trees were employed to infer the phylogenetic relationships of the new genus Setocallosa and to confirm their distinctiveness from other camaenid genera in the region, which has been deduced from comparative morphology (Fig. 5). Based on an explorative phylogenetic analysis of a comprehensive 16S data set of the Camaenidae (not shown) we selected a subset of more closely related camaenids, including a suitable outgroup, for more thorough analysis. This final data set contained concatenated COI and 16S sequences from 147 camaenid specimens from the NT and WA, which represented 23 different genera

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(Table S1). Sequences of Setobaudinia spp., endemic to the Kimberley (WA), were used as outgroup to root the trees. One hundred and forty specimens were represented in the dataset by sequences from both genes, three specimens only by COI and four only by 16S sequences. The missing sequence fragments were coded as unknown. The concatenated alignment of COI and 16S had a total length of 1446 bp (COI: 655 bp, 16S: 791 bp). Xia’s tests (Xia et al. 2003) indicated no or little saturation in both mitochondrial fragments (Iss < Iss.c with p < 0.01). The goodness-of-fit test revealed the TN93 model (Tamura and Nei 1993) with gamma distribution and proportions of invariable sites (TN93 +  + I) as the best-fit model of sequence evolution for both gene fragments by means of the Bayesian Information Criterion. TN93 +  + I was used in all ML analyses but because this model is not supported by MrBayes, the model GTR +  + I was used instead in the BI analyses. The BI and ML analyses produced trees that differed with respect to their basal topology and the nodal support for basal branches. Both trees supported two large supra-generic clades: EK/VRD, including most of the camaenid genera occurring in the more arid rangelands of the AMT and KIM, comprised of three genera (Baudinella, Molema and Retroterra) having their largest diversity in the wetter island and coastline of the Kimberley. A third monophyletic group, NAUS, is supported by the BI analysis only, including the Kimberley endemic sister taxa Setobaudinia and Kymatobaudinia along with some genera with wide distributional ranges (Trachiopsis, Torresitrachia and Rhagada Martens, 1860) across Northern Australia Within the major clades, the topologies are consistently resolved and receive high nodal support in both trees. All species were well separated from each other by being placed on long branches. The new taxon, S. pathutchingsae, occupied a distinct position that was well-isolated from any other species in the analysis. The BI and the ML trees revealed different sister-group relationships of S. pathutchingsae with either the EK/VRD or the KIM clades. The nodal support of both topologies was low. Discussion The newly described taxon Setocallosa pathutchingsae revealed patterns already known from other camaenids in Arnhem Land, such as Arnemelassa, Arnhemtrachia and Parglogenia (Köhler 2012; Köhler and Criscione 2013a). All of these taxa are morphologically highly distinct, strictly endemic to the region but phylogenetically rather enigmatic. As for Setocallosa, its morphological and phylogenetic distinctiveness warrants recognition as a new and monotypic genus, but its position in the camaenid tree remains ambiguous. Setocallosa is readily distinguished

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A

B

Figure 5. Phylograms based on analyses of the concatenated COI and 16S sequences. A, Bayesian tree. Numbers above branches indicate nodal support (% ≥ 90%) by Bayesian posterior clade probabilities (BPP). B, Maximum Likelihood phylogram based on analyses of the concatenated COI and 16S sequences. Numbers above branches indicate nodal support (% ≥ 70%) by ML bootstrap (BTSP). Support values of 100% are represented by asterisks. Branches including sequences of most outgroup taxa are shown as collapsed. KIM, genera from the Kimberley high-precipitation zone; EK/VRD, genera from arid and semi-arid rangelands of Australian Monsoon Tropic; NAUS, genera endemic of the Kimberley or with wide distributional ranges across Northern Australia.

from other camaenids by a typical combination of morphological features of the shell and genital anatomy: The shell differs from most other known taxa by a combination of small size, flat shape, wide umbilicus and peculiar sculpture. While shell characters may also reflect functional constraints or adaptations to varying environments (Solem 1985; Criscione et al. 2012; Criscione and Köhler 2013a), the genital anatomy confirmed the systematic distinctiveness of Setocallosa from any other Arnhem Land camaenid. The mitochondrial phylogenies revealed a basal position of Setocallosa amongst

the north-western Australian Camaenidae. However, conflicting topologies of the Bayesian and Maximum Likelihood trees showed Setocallosa either as sister group of a Kimberley Clade (KIM) or the East Kimberley/Victoria River District clade (Fig. 5). Supplementary data Table S1. Museum registration numbers, voucher status and GenBank accession numbers of samples included in the molecular analysis.

New camaenid genus Acknowledgements This work has been made possible through financial support from the Australian Government (ABRS grant RF210–05 to FK). Special thanks are due to Michael Shea (AM) for producing illustrations of genitalia, and to Sue Lindsay (AM) for conducting the SEM work. Thanks are also due to the reviewers, Corey Whisson (WAM) and John Stanisic (QM), for their helpful comments on an earlier manuscript.

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