A New Species of Tasmanian Mountain Shrimp, Anaspides driesseni sp. nov. (Malacostraca, Anaspidacea, Anaspidesidae)

. Species of the genus Anaspides , known as mountain shrimps, are endemic to Tasmania and inhabit a variety of freshwater habitats such as mountain tarns, pools, creeks and runnels, as well as caves. Until 2015 only two species of Tasmanian mountain shrimps were recognized, A. tasmaniae (Thomson, 1893), which was believed to be widespread all over the island and A. spinulae from Lake St. Clair. Revision of the genus by Ahyong in 2016 recognized 7 species, most having narrow geographic distributions. Only two widespread species remained: A. richardsoni, occurring mainly on the Central Plateau and its margins, and A. swaini , occurring largely in south-western Tasmania . Notably, within A. swaini , three geographically correlated morphological forms were observed. We re-evaluated all three forms of A. swaini and herein describe one of the forms as a new species, A. driesseni , on the basis of morphological and molecular data. Anaspides driesseni corresponds to A. swaini form 3 and occurs mainly in south-eastern Tasmania from the Hartz Mountains over the Snowy Mountains to the Wellington Range. Telson structure, spination and male secondary sexual characters proved taxonomically instrumental.


Introduction
The investigations of Ahyong (2015Ahyong ( , 2016) ) significantly expanded our taxonomic knowledge of Anaspides leading to the morphological description of five new species, A. clarkei Ahyong, 2015, A. jarmani Ahyong, 2015, A. swaini Ahyong, 2015, A. eberhardi Ahyong, 2016and A. richardsoni Ahyong, 2016, bringing the known fauna to seven species.Ahyong (2016), however, observed geographically correlated morphological variation in some species (e.g., A. swaini, A. richardsoni) suggesting additional unrealized taxonomic diversity.Anaspides swaini is notable, having the widest putative distribution, ranging from southern Tasmania from the Weld River, Snowy Mountains region, Mt Field and Mt Wellington (North West Bay River catchment) to the Western Arthurs Range, throughout the Franklin-Gordon drainage, north to Lake Rhona and Frenchmans Cap, Mt Rufus and the vicinity of Lake St. Clair on the Central Plateau.Ahyong (2016) observed three morphologically different forms occurring in different areas and drainages.Form 1 corresponds to A. swaini sensu stricto and has a south-western range, essentially around the periphery of Lake Gordon and Lake Pedder, from Lake Rhona to Mt Field and Mt Mueller to the Snowy Mountains, Federation Peak, the Arthur Ranges and at least as far north as Coronation Peak on the south-western side of Lake Pedder.It is usually more spinose than form 2 and 3. Anaspides swaini form 1 was also included in the molecular study of Richter et al. (2018) where they found high intraspecific distances (especially within COI) between specimens that were collected alongside the Mueller Road occurring sympatrically in the sampled rivers.Form 2 has a northern range beyond Lakes Gordon and Pedder, from the southern part of the Central Plateau, where it ranges from the western vicinity of Lake St. Clair including the Cuvier Valley and Mt Rufus south to Butlers Gorge and Wentworth Hills and Frenchmans Cap; it continues further south in caves in the Nicholls Range karst (Bill Nielson) and Franklin River karst (Kutikina), where it is apparently isolated from surface forms (Eberhard et al., 1991).Form 3 has a south-eastern distribution; it occurs east of Tyler's Line, ranging from the western and northern Wellington Range, including the North West Bay River catchment of Mt Wellington, to at least the Huonville area.
The taxonomic status of A. swaini form 2 is currently subject to ongoing study, but herein, we formally recognize A. swaini form 3 as new to science.

Collection, identification of specimens and morphological methods
Morphological terminology follows Ahyong (2015Ahyong ( , 2016)).Measurements of specimens are of total body length, measured from the apex of the rostrum to the tip of the telson.Abbreviations: above sea-level (asl); feet (ft); indeterminate (indet); juvenile (juv.).
For the taxonomic descriptions, ethanol preserved specimens were softened in glycerol for 1-2 days before dissection of appendages along the left side of the body.Illustrations were produced using a drawing tube attached to a Nikon Eclipse 80i or Leica M165C stereomicroscope.
Specimens are deposited in the collections of the Australian Museum, Sydney (AM); South Australian Museum, Adelaide (SAMA); Tasmanian Museum and Art Gallery, Hobart (TMAG); National Museum of Natural History, Smithsonian Institution, Washington DC (USNM); Western Australian Museum (WAM); and Zoological Collection, Universität Rostock (ZSRO).
A total of 94 specimens of A. swaini and A. driesseni sp.nov.were collected and newly sequenced for this study (Table 1).In addition, a total of 47 COI, 57 16S rRNA and 30 28S sequences from the study by Richter et al. (2018) were included to calculate genetic distances.
All PCR reactions were performed with a Mastercycler gradient (Eppendorf).PCR products were visualized by gel electrophoresis, using 5 μl of the PCR product with 1.5 μl loading buffer DNA b II (AppliChem) on a 1.2 % agarose/TAE gel stained with 5 μl Rotisafe (Carl Roth).PCR products were purified using paramagnetic beads (High Prep PCR, Magbio) following the manufacturer's instruction with a final volume of 25 μl.Sequencing of PCR products was performed in Lightrun 96 well plates by the company, Eurofins Genomics, as well as using the dideoxy chain termination method and cycle sequencing using an ABI Prism® Big Dye® Terminator V.1.1Cycle Sequencing Kit.Cycle sequencing products were analysed by using capillary separation on an ABI Genetic Analyzer 3130 xl (Applied Biosystems/Hitachi).The resulting chromatograms were manually checked and adjusted with Geneious 2021.0.3 (Biomatters Limited).The sequences of all three gene fragments were separately aligned using Consensus Align implemented in Geneious Prime 2021.0.3 (Biomatters Limited) with default parameters.All sequences were deposited at GenBank (Benson et al., 2005) (accession numbers: OP684680-684764, OP686521-686535, OP686545-686569, OQ158727-OQ158764, OQ160856-OQ160881, OQ160958-OQ160970).Pairwise distances were calculated using MEGA X (Kumar et al., 2018).For pairwise distance analyses the uncorrected p-distance was calculated.Phylogenetic networks were calculated with Network 10.2.0.0.(Fluxus Technologies) separately for COI, 16S, and 28S alignments by using the median-joining method with the parameter epsilon set to 10.
Right mandibular incisor process with proximal tooth distally bifid to quadrifid, usually trifid.
Uropodal protopod dorsally unarmed or with 1-3 small spines; exopod with 2-5 movable spines on outer margin near position of partial diaeresis; exopod length about 2.5-3.0×width, slightly wider than endopod, apex rounded, narrow to relatively broad.Etymology.Named in honour of Michael Driessen PhD, for his many contributions to the conservation of Tasmanian Wildlife, especially of our knowledge of Allanaspides, and for his facilitation of our research in Tasmania.

Remarks.
Of the three morphological forms of Anaspides swaini recognized by Ahyong (2016), A. driesseni sp.nov.corresponds to form 3. Anaspides driesseni sp.nov.differs from form 1 through the reduced pleonal spination (except for some specimens from the Arthurs Range and Frankland Range), the less narrowed lateral margins of the telson, which are more parallel and narrows just to the end, the shape of the antennule inner flagellum with the highly setose lateral inner margins on article 1-6, the proportions of article 5-6 (in A. swaini form 1, article 5 is as wide as long to slightly longer than wide and article 6 is always longer than wide), the obtusely angled inner margin of article 4-7 and the presence of two short clasping spines, with the distal clasping spine being equal to slightly longer than the width of article 7 and the proximal clasping spine being equal to slightly shorter than the width of article 7 (Figs 2G, 4E,H,M, 5).In contrast, both clasping spines of A. swaini form 1 are always longer than the width of article 7 (1.3-2.0×longer than the width) (Fig. 11A,B).Anaspides swaini form 2 has reduced pleonal spination as in A. driesseni, but differs in the shape of the telson, resembling that of form 1, the presence of pleopodal endopod 1-5 and the shape of the antennule inner flagellum.As in A. swaini form 1, both clasping spines are longer than the width of article 7 (1.1-1.8×longer than the width of article 7), only article 6 is obtusely angled and articles 5-6 are longer than wide (Fig. 11C).Also A. swaini form 2 shows less setation on articles 1-6, similar to that of A. swaini form 1.
Anaspides driesseni sp.nov. is distinguished from other congeners by the combination of the angular posterior margin of the telson, the presence of pleopodal endopod 1-4, the greater size at maturity (23-29 mm, usually 26-28 mm), the shape of the antennule inner flagellum in adult males (Figs 2G , 4E,H,J, 5) and the presence of two small clasping spines (Figs 2G , 4E,J, 5).
Sexual maturation at a larger body size (indicated by the full development of secondary sexual features) is noticeable and separates A. driesseni from all other species of the genus.In A. driesseni, sexual maturity is reached by 23-29 mm, usually at 26-28 mm body length, while other species reach maturity at 18-23 mm (usually 20-21 mm), respectively 14-15 mm in A. spinulae (Ahyong, 2016).In A. driesseni, the endopod of pleopod 4 is not developed (occasionally on one side) before reaching a size of about 11 mm.
Overall, A. driesseni is morphologically rather consistent, with only slight variation evident.The specimens from the Snowy Range region, except those from the unnamed creek crossing the road off Waterfall Creek Road (tributary of Styx River) (ZSRO CR183, AM P106559), some specimens from Lake Skinner and one specimen from Lake Picton (TMAG G6424), lack the denticle on the uropodal protopod and show no pleural spination of the pleon.Furthermore, the antennular outer flagellum is elongated, ranging from 0.7-0.9× of the body length in comparison to specimens from the Wellington Range and the tributary of Styx River (0.4-0.8× of the body length, usually 0.4-0.6).The Arve-Valley-Hartz populations similarly lack the denticle on the uropodal protopod, but in the remaining characters, resemble the populations from the Wellington Range.Only in three aberrant specimens from Snowy North (ZSRO CR183) and one specimen from a nameless tarn near the summit of Snowy South, an abnormal number of clasping spines on one side was observed.Three specimens had 3 clasping spines (2x Snowy North, 1x Snowy South) on one side rather than the usual 2, and one specimen had 4 clasping spines (Fig. 5B).In these specimens the additional spines were not in a row as in "normal" males, but instead they stand disorderly in a second row, forming a kind of cluster.These cases appear to be the result of abnormal development of the clasping spines, which typically develop in a single row along the article axis.
Anaspides driesseni the species with the largest known males, with two males from an unnamed tarn near the summit of Snowy South reaching 40 mm total length.The largest known male so far is one male of A. richardsoni from Honeycomb Cave in the Mole Creek karst system reaching 37 mm.The largest epigean males apart A. driesseni are recorded with 33 mm in A. richardsoni and A. tasmaniae (Ahyong, 2016).
Why epigean A. driesseni attains such a large maximum body size compared to congeners might be related to the onset of maturity at a larger body size.
To date, there are no known subterranean occurrences of A. driesseni.Molecular data.Maximum intraspecific uncorrected p-distances for A. driesseni were 2.2% in COI, 0.6% in 16S and 0.3% in 28S, while interspecific distances to other congeners of the genus Anaspides were 8.4-14.2% in COI, 1.2-7.1% in 16S and 0.6-3.5% in 28S (Table 2).In COI we uncovered 11 different haplotypes in 4 distinct haplotype clusters for Anaspides driesseni (Fig. 6).The first cluster comprises specimens from an unnamed creek crossing the road off Waterfall Creek Road, the tributary of South Styx River, a nameless tarn near Snowy South, Billy Brown River, Glen Dhu Creek and a roadside ditch near the East-West track.The second cluster comprises specimens from Lake Skinner, while the third cluster comprises specimens from St. Crispins Well and an unnamed creek crossing the Pipeline Track.The fourth cluster comprises specimens from Myrtle morphologically, being less spinose than their more easterly occurring conspecifics.Until more detailed population data are available, they are considered to represent a single species (A.swaini).
Comparable to Anaspides tasmaniae (Höpel et al., 2021), in A. driesseni a disjunct distribution between Wellington Park and areas in the south-western wilderness is present (25 km apart, Billy Brown River-Lake Skinner, Figs 7-9), which might be due to a current lack of suitable habitats in the lower areas between the two mountain ranges with the main limiting factors being the water temperature, dissolved solids and turbidity (Williams, 1965;Swain and Reid, 1983;O'Brien, 1990).It should also be noted that we see no signs of artificial translocation as shared haplotypes in COI between Snowy Range and Wellington Range as well as between major drainage systems at Wellington Range (Figs 6, 8-9) do not occur.Therefore, we are likely witnessing the same phenomenon as observed in A. tasmaniae, namely that during glacial periods (6-10°C colder than today, Colhoun et al., 2010), A. driesseni may have occupied a wider Interestingly, we detected one shared haplotype in COI between two locations at the Snowy Range, which belong to two different major drainage systems (Derwent and Huon River catchment) (Figs 6,8).We suggest that this shared haplotype is explained by colonization of neighbour ing drainages over mountain plateaus via floodplains, swamps or snow and snowmelt channels, connect ing temporarily different water systems (e.g., at Nevada Peak) (Fig. 8).Interestingly, specimens from a nameless tarn near the summit of Snowy South and Lake Skinner belong to different haplotype clusters in COI (Fig. 6) despite being only 800 m horizontally and 300 m in altitude apart.A similar case of potential crossing of watersheds is found at Wellington Park, where we have two closely related haplotypes in COI and even a shared one in 16S (Fig. 6), between the Myrtle Forest Creek/Sorell Creek (Fig. 9, subdrainage system 3) + Knights Creek systems (Fig. 9, subdrainage system) (all Derwent River catchment) and the Mountain River catchment (Fig. 9, subdrainage system 9, Huon River catchment).A potential crossing area could be the floodplains, swampy area near todays Big Bend Trail.This model of phylogeographic pattering corresponds largely to the Headwater Model (HM) proposed by Finn et al. (2007) (waterbug Abedus herberti, limited overland dispersal), extended by temporarily connections due to flooded tarn shelfs or swamps or snow and snow melt.Anaspides probably also has a limited overland dispersal ability, having been previously observed to sometimes crawl out of the water and being able to survive several days on land (Swain & Reid, 1983).

Figure 6 .
Figure 6.COI, 16S and 28S median joining haplotype networks of Anaspides driesseni.Colours correspond to figure legend.The size of each haplotype corresponds to the number of individuals sharing that specific haplotype (see scale).Each dash corresponds to one mutation respectively indel.

Figure 8 .
Figure 8. Topographical map of Snowy Range with major drainage systems, as well as collection sites with genetically analysed individuals from this study.1 corresponds to the Derwent River drainage system, while 2 corresponds to the Huon River drainage systems.Base image by TASMAP© (www.tasmap.tas.gov.au)State of Tasmania.

Figure 10 .
Figure 10.Typical habitats and colour-in-life of A. driesseni: (A) Glen Dhu Creek (B) Knights Creek at Knights Creek Track (C) small trickle fed road side ditch, next to Collins Cap Trail (D) unnamed creek, tributary of Styx River, crossing the road off Waterfall Creek Road (E) adult male, 35 mm, Ana560, unnamed creek, tributary of Styx River, crossing the road off Waterfall Creek Road.(F) adult male, 29 mm, AM P106559, unnamed creek, tributary of Styx River, crossing the road off Waterfall Creek Road.