The Tasmanian Mountain Shrimps, Anaspides Thomson, 1894 (Crustacea, Syncarida, Anaspididae)

Abstract

The Tasmanian mountain shrimps of the genus Anaspides Thomson, 1894 (Syncarida: Anaspididae), are endemic to Tasmania and often regarded as "living fossils" owing to the retention of numerous putatively plesiomorphic eumalacostracan traits and minimal morphological change since the Triassic. All live in cold, usually high altitude fresh-waters. Until recently, only two species were recognised: the presumed widespread A. tasmaniae (Thomson, 1893) (type species) and A. spinulae Williams, 1965a, from Lake St Clair, whose validity was frequently questioned. Independent morphological and molecular studies revealed previously unrecognized taxonomic diversity, resulting in preliminary descriptions of three new species in 2015. Anaspides is revised based on extensive collections from throughout Tasmania. Telson structure and male secondary sexual characters proved taxonomically instrumental. Seven species are recognized of which two are new to science; all are fully figured and morphological variation is discussed in detail. Rather than being widespread, Anaspides tasmaniae is restricted to Mount Wellington; A. spinulae is a valid species known only from Lake St Clair. Two species, A. clarkei Ahyong, 2015, and A. eberhardi sp. nov. occur only in caves of the Ida Bay-Hastings karst systems and Junee-Florentine systems, respectively. The three widest ranging species (A. jarmani Ahyong, 2015, A. swaini Ahyong, 2015, and A. richardsoni sp. nov.) are primarily epigean and each contains several morphological forms that might warrant further taxonomic subdivision. Distributions of species of Anaspides are largely discrete and broadly correspond to the biogeographical discontinuity known as Tyler's Line, dividing the drier eastern from the wetter western parts of Tasmania. Caves are believed to have acted as oligothermal refuges for Anaspides in the past, and it is notable that the specimens from the lowest altitudes today are all from caves, including the northernmost record of Anaspides (A. richardsoni, Great Western Cave, Gunns Plain, 109 m asl). Given the revised taxonomy of Anaspides, with significantly altered species distributions, the conservation status of all species of the genus requires review.

Phylogeny and species diversity of Tasmanian mountain shrimps and their relatives (Crustacea, Anaspidesidae)

“…Within the Anaspides + Paranaspides clade, few relationships are stable when using different analytical approaches. Paranaspides is nested within Anaspides in some analyses, which appears plausible considering the few major morphological differences between the two genera (Ahyong, ; Ahyong et al., ). Anaspides clarkei and A. jarmani form a clade in all analyses, which is also reflected in their close geographical relationship and by synapomorphic male secondary sexual characters (Ahyong, ).…”

“…Field specimens; 6.2–6.5/0.9% compared to the Honeycomb Cave specimens). Thus, A. richardsoni as currently understood may comprise more than one species as possibly suggested by the significant morphological variation evident in parts of its range (Ahyong, ). The results from the 28S data (see Figure ) are more conservative, in which A. tasmaniae , A. swaini and A. jarmani possess uniform sequences, respectively.…”

“…Additional specimens were collected by S. Jarman, J. Andrew, S. Eberhard, R. Mollison, M. Franks and A. Clarke. Specimens were identified based on morphology following Ahyong (, ) and Ahyong et al. ().…”

“…Anaspides spinulae , however, was not found to be well differentiated from A. tasmaniae . More recently, Ahyong (, ) taxonomically revised Anaspides and recognized seven species including A. spinulae as distinct from A. tasmaniae , the former restricted to Lake St Clair and the latter to Mount Wellington. Great Lake and nearby lagoons are the habitat of the “lake shrimp” Paranaspides Smith, , so far the only largely natatorial representative of the Anaspidesidae, but recently, Ahyong, Schwentner, and Richter () recognized a second species of Paranaspides , P. williamsi .…”

“…Although anaspidesids are usually epigean, Anaspides has also entered caves throughout Tasmania, some species having marked troglobitic adaptations (Ahyong, ). Given their cold‐water requirements, Williams () hypothesized that Anaspides entered caves during the much warmer Tertiary period, using these subterranean habitats as oligothermal refuges from the elevated temperatures of the time.…”