Molecular phylogenetic analysis supports a Gondwanan origin of the Hyriidae (Mollusca: Bivalvia: Unionida) and the paraphyly of Australasian taxa

The freshwater mussel family Hyriidae (Mollusca: Bivalvia: Unionida) has a disjunct trans-Pacific distribution in Australasia and South America. Previous phylogenetic analyses have estimated the evolutionary relationships of the family and the major infra-familial taxa (Velesunioninae and Hyriinae: Hyridellini in Australia; Hyriinae: Hyriini, Castaliini, and Rhipidodontini in South America), but taxon and character sampling have been too incomplete to support a predictive classification or allow testing of biogeographical hypotheses. We sampled 30 freshwater mussel individuals representing the aforementioned hyriid taxa, as well as outgroup species representing the five other freshwater mussel families and their marine sister group (order Trigoniida). Our ingroup included representatives of all Australian genera. Phylogenetic relationships were estimated from three gene fragments (nuclear 28S, COI and 16S mtDNA) using maximum parsimony, maximum likelihood, and Bayesian inference, and we applied a Bayesian relaxed clock model calibrated with fossil dates to estimate node ages. Our analyses found good support for monophyly of the Hyriidae and the subfamilies and tribes, as well as the paraphyly of the Australasian taxa (Velesunioninae, (Hyridellini, (Rhipidodontini, (Castaliini, Hyriini)))). The Hyriidae was recovered as sister to a clade comprised of all other Recent freshwater mussel families. Our molecular date estimation supported Cretaceous origins of the major hyriid clades, pre-dating the Tertiary isolation of South America from Antarctica/Australia. We hypothesize that early diversification of the Hyriidae was driven by terrestrial barriers on Gondwana rather than marine barriers following disintegration of the super-continent

Age and growth in the Australian freshwater mussel, Westralunio carteri, with an evaluation of the fluorochrome calcein for validating the assumption of annulus formation

Growth and longevity of freshwater mussels (Unionida) are important for defining life-history strategies and assessing vulnerability to human impacts. We used mark-recapture and analysis of shell rings to investigate age and growth of the hyriid, Westralunio carteri, at 5 sites in southwestern Australia. We tested the utility of the in situ marker calcein for validating the assumption of annulus formation in adults. Calcein was incorporated into the shells of all recovered individuals, but it provided an interpretable reference mark in only 4 of 16 individuals. These 4 individuals produced 1 shell ring subsequent to the mark, supporting the assumption of annulus production during the austral winter. Maximum age ranged among populations from 36 to 52 y and maximum size ranged from 72.9 to 82.8 mm. Mean age and length did not differ between sexes, and growth trajectories differed between sexes at only 1 site. Estimates of growth measured by the von Bertalanffy growth constant, K, ranged from 0.021 to 0.336 among sites. Estimates from mark-recapture experiments were 20 to 52% lower than values from shell annuli at all sites except 1 where K from shell annuli was similar to 1/2 that estimated from mark-recapture. Both methods showed a positive relationship between K and mean water temperature among sites, suggesting a role of riparian shading in regulating stream temperature, and hence, indirectly influencing mussel growth. Mussel growth and mean N or P concentrations were not related among sites, but total N at the site with highest mussel growth was >2x higher than at any other site. Westralunio carteri is a long-lived, slow-growing bivalve. Maximum age, K, and probable age at maturity (4-6 y) are similar to other slow-growing freshwater bivalve groups. This suite of life-history traits is considered an adaptation for stable aquatic habitats. Therefore, W. carteri can be expected to adapt poorly to human impacts, such as riparian clearing and water extraction, which increase the temporal variability of environmental conditions in streams

Freshwater shrimp (Palaemonetes Australis) may be involved in glochidia release from the freshwater mussel(Westraluno Carteri)

On 27 November 2010 while snorkeling in Canebreak Pool, Margaret River I observed interesting interactions between freshwater shrimp (Palaemonetes australis) and freshwater mussels (Westralunio carteri). First, it is necessary to give a brief explanation of the life cycle of the Unionoidea, a superfamily within the order Unionoida, which are characterised by their larval type (Parodiz and Bonetto 1963)

Distribution of Westralunio carteri Iredale, 1934 (Bivalvia: Unionoida: Hyriidae) on the south coast of south-western Australia, including new records of the species

Westralunio carteri Iredale 1934 is the only hyriid in southwestern Australia. The species was listed as ‘Vulnerable’ by the IUCN, due to population decline from dryland salinity, although the listing was recently changed to ‘Least Concern’. The Department of Environment and Conservation lists the species as ‘Priority 4’, yet it lacks special protection under federal or state legislation. Accuracy in species accounts is an important driver in determining conservation status of threatened species. In this regard, discrepancies in locality names and vagary in museum records necessitated the eastern distributional bounds of W. carteri to be clarified. Here we present an updated account of the species’ distribution and describe two previously unknown populations of W. carteri in the Moates Lake catchment and Waychinicup River, resulting in an eastern range extension of 96–118 km from the Kent River, formerly the easternmost river where W. carteri was known. For mussel identification, samples (n = 31) were collected and transported live to the laboratory for examination and internal shell morphology confirmed that the species was W. carteri. Due to an acute salinity tolerance of 3.06 g/L (LD50 ), the species is unlikely to exist in catchments east of the Waychinicup River where salinities are known to be as high as 45 g/L. The current study clarifies the eastern distribution of W. carteri and will allow monitoring of its range decline to be made in the future

Description of the glochidia of Alathyria pertexta pertexta Iredale, 1934 (Bivalvia:Hyriidae) from south-eastern Queensland

Most freshwater mussels (Bivalvia: Unionida) have larvae (glochidia in Margaritiferidae, Hyriidae and Unionidae) that are parasitic on fishes. Mechanisms of glochidia release and morphological features (size, shape, larval teeth, etc.) vary across taxa and geography. Among the Australasian Hyriidae, glochidia have been described from 12 of the 28 putative species. Alathyria pertexta Iredale, 1934 is a widespread species from subtropical/semitemperate south-eastern Queensland and northern New South Wales to the northern wet tropics of Queensland and southern New Guinea. Little information is available on its biology and its glochidia have not been described in detail. The aim of this study was to describe the glochidia of A. pertexta pertexta and the method of their release. Gravid females collected from Mary River, near Kenilworth, and Isaac River, north-west of Rockhampton, Queensland, released glochidia in ‘amorphous mucus conglutinates’, in which glochidia are released from exhalent siphons of females in a loose mucus matrix that dissociates in water, during the austral spring (August–October); they then hatched from vitelline membranes but remained tethered by a larval thread and began characteristically ‘winking’. Shells (n = 80) are subtriangular and scalene in shape, 268.1 µm long (±1.21, s.e.), 242.9 µm high (±1.22, s.e.) and have a hinge length of 191 µm (±0.63, s.e.). Larval teeth are spineless, S-shaped hooks with singular interlocking cusps on opposing valves. The surface of the apex and valve margins are crenulated, and valves are smooth and porous, held together by a hinge and a singular internal adductor muscle

Glochidia ecology in wild fish populations and laboratory determination of competent host fishes for an endemic freshwater mussel of south-western Australia

Glochidia (parasitic larvae) of freshwater mussels generally require a fish as a host. Westralunio carteri Iredale, 1934 (Bivalvia : Hyriidae), the only freshwater mussel found in south-western Australia, was listed as Vulnerable, but recently changed to Least Concern (International Union for the Conservation of Nature). Glochidia were found on four alien and seven native species of fish from 18 sites in the South West Coast Drainage Division. On alien fishes, prevalence of glochidia ranged from 0.0 to 41.0% and mean intensity (number of glochidia per infested fish) from 1.0 to 6.0, while on native fishes prevalence was 9.2–90.5% and intensity was 2.3–7.1. Glochidia infestation was greatest on benthic fishes, which may be a consequence of greater encounter rates, but other factors, such as host size, probably also influence glochidia prevalence and intensity. Glochidia were generally restricted to fins of infested fish, and were rarely on gills or the body surface. In the laboratory, four native and one alien fish species were found to be competent hosts for their ability to produce juvenile W. carteri, but two alien fish species were not. The inability of some alien fishes to produce juvenile W. carteri could potentially reduce recruitment success in areas dominated by alien fishes

Morphological evidence shows not all Velesunioninae have sculptured umbos

Most species in the freshwater bivalve order Unionida (sensu Carter et al., 2011) display some form of shell sculpture during the early postlarval stage. These so-called ‘umbonal sculptures’, ‘beak sculptures’ or ‘rugae’ range from more or less regularly formed V- and zigzag-shapes to pseudoradial, pseudoconcentric and double-looped bars, and single-standing nodules (Modell, 1942, 1964; Watters, 1994; Zieritz, 2010). In some Unionida, this ornamentation may extend to mature ontogenetic stages (e.g. Hyriidae; Haas, 1969a, b; Watters, 1994). Others, however, are regarded as lacking sculptured umbos altogether. These include (1) the Mycetopodidae (according to descriptions by Modell, 1942, 1964; Haas, 1969a, b; Zieritz, 2010); (2) most Iridininae including Mutela rostrata (Rang, 1835), Pleiodon ovata (Swainson, 1823) and Pleiodon spekii (Woodward, 1859) (according to descriptions by Pilsbry & Bequaert, 1927; Zieritz, 2010); and (3) some Unionidae such as Actinonaias pectorosa (Conrad, 1834), Delphinonaias delphinulus (Morelet, 1849) and Pseudospatha tanganyicensis (Smith, 1880) (Zieritz, 2010). Finally, various authors, including Cotton & Gabriel (1932), Iredale (1934), Modell (1942, 1964), McMichael & Hiscock (1958) and Haas (1969a), stated that smooth umbos are also characteristic of all members of (4) the Velesunioninae, a subfamily of the Hyriidae endemic to the Australasian region (Walker et al., 2001; Walker, Jones & Klunzinger, 2013). Haas (1969b), on the other hand, described beak sculpture in the “subgenus Velesunio”—comprising four of the five currently recognized velesunionine genera (except Lortiella)—as “not strong, consisting of broken, nodulose ridges curving toward each other below, generally with smooth space between”. Unfortunately, no illustration of these sculptures has been made available by this or any other author to date

Discovery of a host fish species for glochidia of Westralunio carteri Iredale, 1934 (Bivalvia: Unionoidea: Hyriidae)

Freshwater fishes are the usual hosts of glochidia (the parasitic larval stage) of freshwater mussels (Bivalvia: Unionoidea). Westralunio carteri Iredale 1934 (Carter’s mussel), the only unionoid species found in the Southwest Coast Drainage Division of Australia, is endemic to the region and is currently listed as Vulnerable on the IUCN Red List, yet nothing is known of its host species. Small, white, bladder-like cysts were observed macroscopically on Tandanus bostocki Whitley, 1944 (freshwater cobbler) captured from the Blackwood River, Western Australia. Light microscopy of sectioned cysts revealed that they contained glochidia and these were of similar size and shape to glochidia obtained from gravid females of W. carteri. Glochidia were found on 40.7% of 461 T. bostocki examined, with a mean intensity of 10.6 cysts per infested fish. Prevalence of infestation was greater on juvenile than on adult fish. The findings represent an important step in developing conservation measures for W. carteri in this region

Discovery of a host fish for glochidia of Velesunio angasi (Sowerby, 1867) (Bivalvia : Unionoida : Hyriidae) from the Fortescue River, Pilbara, Western Australia

Freshwater fishes are the most common hosts of the glochidia (parasitic larvae) of freshwater mussels (Bivalvia: Unionoida: Unionoidea). Velesunio angasi (Sowerby, 1867) (Hyriidae), is the only known hyriid species recorded from the Fortescue River in the Pilbara region of Western Australia. Eleven species of fish (n = 516) were captured from pools of the Fortescue River in June 2010. Small, white, bladder-like cysts were observed on Neosilurus hyrtlii Steindachner, 1867, though not on any of the remaining 10 species examined. Light microscopy of sectioned cysts revealed that they contained glochidia that were of similar size and shape to those of V. angasi. Glochidia were found on 73.2% of 168 N. hyrtlii examined, with a mean intensity of 3.3 cysts per infested fish. Prevalence was significantly greater on smaller fish (P < 0.01); however, no relationship between size and intensity of infestation was observed. This represents the first record of glochidia infestation on fish from the Pilbara region

Piggyback on a fish: the marsupial freshwater mussel tells its tale

Scientists are putting the freshwater mussel under the spotlight in a bid to learn more about this little-known creature