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

Abstract

Abstract. 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 39.5% and mean intensity (number of glochidia per infested fish) from 1.0 to 6.0, while on native fishes prevalence was 9.2-75.0% 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 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.

Upstream recolonization by freshwater mussels (Unionoida: Hyriidae) following installation of a fishway

“…First, the W. carteri population may have mirrored the growth of the G. truttaceus population, which has increased in overall numbers and maximum lengths of individuals (Morgan et al, ), potentially providing more host fish (sensu Arvidsson et al, ). Second, the G. truttaceus population boom would also presumably translate to a greater abundance of juvenile fish, which undertake a spring mass migration (Close, Ryan, Morgan, Beatty, & Lawrence, ; Morgan et al, ) coinciding with the period of glochidial release by W. carteri (Klunzinger, Beatty, Morgan, Thomson, ). Third, the Goodga mussel population was only discovered in 2012 (Klunzinger, Beatty, Morgan, Lymbery, ); while there have been few biological surveys of the river, mussels were not detected during an invertebrate survey in the downstream reach by Shiel (), despite extensively sampling instream habitats including various benthic substrates, albeit at only one location.…”

“…The applicability of this approach to other situations will depend on factors such as the host‐specificity of the mussel and mobility of the host. For example, W. carteri is a host‐generalist, likely to use highly mobile galaxiids (Klunzinger, Beatty, Morgan, Thomson, ). These fish are strong swimmers and are known to use the Goodga fishway in large numbers (Morgan & Beatty, ).…”

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

“…The number of adults (n) and juveniles (; <4 y old) represented in the data are given in brackets. For information on glochidial size and growth, see Klunzinger et al (2012Klunzinger et al ( , 2013.…”

Range decline and conservation status of Westralunio carteri Iredale, 1934 (Bivalvia:Hyriidae) from south-western Australia

“…Fish species diversity was not included in the list of potential environmental variables, because it was available only for some of the sites and because we considered it unlikely to be a major determining factor in the distribution of W. carteri, which is a host generalist (Klunzinger et al 2012a). Given the importance of variable selection and the need to avoid over-fitting the data during model construction (Burnham and Anderson 2002), several approaches were used to reduce the variable set.…”

“…However, until recently, little was known of its biology. The species is now known to be a sexually dimorphic seasonal brooder with females producing spineless hooked larvae (glochidia) that are parasitic on several host fishes (making W. carteri a host-generalist); they become sexually mature within 3-6 years and live for at least 50 years (Klunzinger et al 2012a(Klunzinger et al , 2013.…”