The Glacidorbidae (Mollusca: Gastropoda: Heterobranchia) of Australia
Total Page：16
File Type：pdf, Size：1020Kb
© Copyright Australian Museum, 2000 Records of the Australian Museum (2000) Vol. 52: 307–353. ISSN 0067-1975 The Glacidorbidae (Mollusca: Gastropoda: Heterobranchia) of Australia W.F. PONDER AND G.J. AVERN Centre for Evolutionary Research, Australian Museum, 6 College Street, Sydney NSW 2010, Australia [email protected] ABSTRACT. The heterobranch gastropod family Glacidorbidae (?Pulmonata) is known only from temperate Australia and Chile. The Australian taxa are reviewed and three new genera, Benthodorbis, Striadorbis and Tasmodorbis are described based on differences in their shells, especially the protoconchs, and in their opercula and radulae. Nineteen species of Australian glacidorbids are recognised, all but four of them new. Of the four Australian species previously included in Glacidorbis, only two, G. hedleyi (Iredale) from New South Wales and Victoria, and G. occidentalis Bunn & Stoddart from south Western Australia, are retained in that genus. Eleven new species of Glacidorbis are described, seven from Tasmania (G. bicarinatus, G. catomus, G. atrophus, G. decoratus, G. costatus, G. tasmanicus and G. circulus), one (G. isolatus) from New South Wales, two (G. otwayensis and G. rusticus) from Victoria and one (G. troglodytes) from South Australia. Striadorbis contains the Tasmanian S. pedderi (Smith), and two new species, S. spiralis from western Victoria and S. janetae from Tasmania. Benthodorbis contains two species, both from old lakes in Tasmania; B. pawpela (Smith) from Great Lake and B. fultoni from Lake Sorell. Tasmodorbis contains a single species found in western Tasmania, T. punctatus, unique in having internal shell pores. Glacidorbis costatus is known only from Pulbeena Swamp in NW Tasmania and appears to be recently extinct, possibly as a result of draining of the swamp in the early part of this century. A cladistic analysis with the South American member of the family, Gondwanorbis, as the outgroup, supports the monophyly of the genera recognised. PONDER, W.F., & G.J. AVERN, 2000. The Glacidorbidae (Mollusca: Gastropoda: Heterobranchia) of Australia. Records of the Australian Museum 52(3): 307–353. Small-sized Australian freshwater molluscs have, in recent A tiny flat-spired gastropod, Glacidorbis hedleyi, was years, been shown to be much more diverse than previously described by Iredale (1943) from Blue Lake, Mount imagined. Nearly all of this diversity is contained within Kosciuszko, NSW. Iredale included his new taxon in the the caenogastropod family Hydrobiidae (see Ponder, 1991 basommatophoran pulmonate family Planorbidae but and Ponder & de Keyzer, 1998 for review), while other Meier-Brook & Smith (1976) showed that the genus was families of small-sized freshwater gastropods such as the operculate and reviewed the known species. While they Assimineidae, Bithyniidae, Planorbidae and Glacidorbidae suggested similarities with the hydrobiids, they did not make are known to contain a several undescribed taxa. This paper any decision on the placement of the genus pending revises the taxa included in the Glacidorbidae. anatomical investigation and Smith (1979) placed 308 Records of the Australian Museum (2000) Vol. 52 Glacidorbis “close to the Hydrobiidae” while Smith & sample was gently elutriated, the light material discarded. Kershaw (1979, 1981) included it in the Hydrobiidae. A few menthol crystals were added to the sample which Glacidorbidae was introduced by Ponder (1986) who was left to stand overnight in an attempt to relax at least described the anatomy of G. hedleyi and erected a new some of the specimens. The sample was then bulk fixed in superfamily for the group that he considered to be atypical, c. 10% neutralised formalin, later transferred to 5% buffered probably paedomorphic, pulmonates. A pulmonate formalin. Specimens were sorted from the bulk sample using relationship was accepted by Visser (1988), although this a dissecting microscope. author suggested that it had a basal position in the Material from the collections of various institutions was basommatophorans, rather than “the suggestion of Ponder also utilised during the study (see list of abbreviations). (1986) that Glacidorbidae represent a neotenous group Although the radulae proved difficult to manipulate, they derived from the Lymnacea”. In fact, Ponder (p. 77) argued were mounted using standard methods. The buccal masses that Glacidorbis may be derived from “proto-pulmonate” were dissolved using a strong solution of potassium ancestors of the Amphibolacea-Ellobiacea, representing a hydroxide, the radulae were removed, washed in distilled freshwater incursion quite independent of the major water and air dried to glass cover slips which were then lymnaeoidean radiation. In contrast to this view of the fixed to SEM stubs. Shells and opercula were mounted using relationship of the family, Haszprunar (1988), Haszprunar standard methods. Most of the material was examined using & Huber (1990) and Huber (1993) argued that because of a Cambridge 120 SEM, although some was examined using the lack of a typical pentaganglionate nervous system, a a LEO 435VP SEM (both with Robinson backscatter pneumostome, procerebrum and dorsal bodies, Glacidorbis detector). Images were captured digitally. was an “allogastropod”, a grouping introduced by A cladistic analysis was conducted using the data matrix Haszprunar (1985) for the “lower heterobranchs” and given in Table 1 with PAUP*4b2 (Swofford, 1999) and the equivalent to Heterostropha as used by Ponder & Warén default heuristic search options and 100 random iterations. (1988). Unpublished sperm ultrastructural data (J. Healy, Gondwanorbis was defined as the outgroup. Bremer support pers. comm.) suggest relationships with basal pulmonates. was calculated using TreeRot ver. 2 (Sorenson, 1999). The pulmonate placement of this group was provisionally followed by Stanisic (1998) in his review of the family Abbreviations for the “Fauna of Australia”. The group was placed in a Shell measurements: aph—aperture height; apw— separate “order” (Glacidorbiformes) within the “subclass aperture width; dmax—maximum diameter; dmin— Sinistrobranchia” by Starobogatov (1988) but this minimum diameter; mdht—height (at mid point of shell); classification has not been considered seriously by other mxht—maximum height of shell; whl—total number of workers. We consider a pulmonate relationship is still whorls. probable and that Glacidorbis is highly paedomorphic, a Collectors: ACM—Alison C. Miller; BJS—Brian. J. factor explaining the absence of many of the typical Smith; DLB—Des L. Beechey; FEH—Frank E. Hermans; pulmonate characters (see also Ponder & Lindberg, 1997). GAC—Gerard A. Clark; IFCT—Inland Fisheries Commission, This assessment could be readily tested using molecular Tasmania; JH—Jane Hall; JHW—Janet H. Waterhouse; data but is beyond the scope of this paper. JMP—Julie M. Ponder; RdK—Roger de Keyzer; SAC— Only four species assigned to Glacidorbis have Stephanie A. Clark; WFP—Winston F. Ponder; WFPj— previously been described from Australia, two of these Warwick F. Ponder. (Valvata(?) pedderi Smith, 1973; Glacidorbis pawpela Institutions: AMS—Australian Museum, Sydney; MV— Smith, 1979) from Tasmania, one from SW Australia (G. Museum of Victoria; QVM—Queen Victoria Museum, occidentalis Bunn & Stoddart, 1983) and G. hedleyi (Iredale, Launceston; SAM—South Australian Museum, Adelaide; 1943) from the Great Dividing Range of Victoria and New TM—Tasmanian Museum, Hobart; WAM—Western South Wales. Smith & Kershaw (1981) mapped the Australian Museum. distributions of the species of Glacidorbis known at that Miscellaneous: AMG—Australian Map Grid, cond.— time and Ponder (1996) mapped Glacidorbis records in NE conductivity (in mS/cm at 12°C); NP—National Park; SF— Tasmania noting that they comprised “two or three State Forest. undescribed species”. A few studies have been made on the biology and ecology of these animals, other than basic habitat and brooding. Ponder Taxonomy (1986) described the reproduction and feeding of Glacidorbis hedleyi, Boulton & Smith (1985) described the ecological The following diagnosis of the monotypic superfamily and requirements of that species, and Bunn et al. (1989) described family are modified from Ponder (1986). the ecology of G. occidentalis Bunn & Stoddard, 1983. Glacidorboidea and Glacidorbidae Ponder, 1986 Material and methods Diagnosis. Shell small to minute (most species less than 2 Material was collected by hand either by washing substrate mm in maximum diameter, one species slightly less than 4 (e.g., vegetation, roots, wood, rock, gravel) into a plastic mm), dextrally coiled, orthostrophic to hyperstrophic, with bowl or small bucket or by using a hand sieve, with a mesh flat or near flat spire to planispiral, with wide, shallow size of c. 1 mm, and sweeping the vegetation. The resulting umbilicus. Operculum circular to oval, multispiral to Ponder & Avern: Glacidorbidae of Australia 309 paucispiral, with central to eccentric nucleus. Jaw with cavity. Prostate gland separate from vas deferens, penis dorsal and ventral elements. Radula with large central teeth narrow and small, completely invaginated, with large sucker bearing several sharp cusps on a pointed mesocone, with or knob-like glands in the large praeputium. broader, arched base lacking additional cusps. Lateral teeth vestigial or narrow and small; marginal teeth absent. Head- Remarks. Glacidorbis shares many anatomical characters foot (details only known for a few species of Glacidorbis) with other heterobranchs