Size‐specific growth patterns and estimated longevity of the unionid mussel (Pronodularia japanensis)

Abstract

Despite the dwindling populations and an urgent need for conservation of unionid freshwater mussels in Japan, there are gaps in our understating of their fundamental ecology. This study examined size-dependent annual growth rates, elucidated size-specific intraannual growth patterns, and estimated age and longevity of P. japanensis individuals for two locally isolated populations in agricultural drainage channels. Annual growth rates of P. japanensis were strongly size-dependent, with growth rates being exponentially decelerated with increasing shell length. Irrespective of sizes, individuals ceased to grow in winter when water temperature fell below 10°C. Intra-annual growth patterns were weakly explained by the changes in water temperature and differed among size classes; juveniles (<25 mm) maximized growth rate in May whereas the growth rates were the highest in June or July for larger individuals. Only adult individuals exhibited growth cessation in the July-August period, suggesting that energy investment was directed towards reproductive activities. Adults also showed negative growth rates (shrinkage of individuals) in winter, suggesting possible dissolution of shell margins. Age estimation based on two 1-year periods suggests that large numbers of P. japanensis individuals were >10 years old, and the oldest individuals were >20 years old for both study populations. Our findings suggest that anthropogenic activities conducted in spring may have strong influences on juveniles and population dynamics of P. japanensis and underscore the need for accurately determining age and longevity of remaining populations of unionid mussels.

Determining Optimum Temperature for Growth and Survival of Laboratory‐Propagated Juvenile Freshwater Mussels

“…Factors that have been found to correlate with mussel growth and survival rates include, but are not limited to, substrate type and size (Hinch et al 1986;Liberty et al 2007), flows and sediment load (Beaty 1997;Zimmerman 2003;Jones et al 2005;Liberty et al 2007;Rypel et al 2008), toxicant exposure (Pandolfo et al 2010a), mussel density (Hanson et al 1988;Beaty 1997;Beaty and Neves 2004;Negishi and Kayaba 2009), food availability (Hanlon 2000), sampling frequency (Beaty 1997;Zimmerman 2003;Liberty et al 2007), maturity of larvae (Jones et al 2005), and temperature (Hanson et al 1988;Buddensiek 1995;Beaty 1997;Hanlon 2000;Zimmerman and Neves 2002;Zimmerman 2003;Liberty 2004;Hanlon and Neves 2006;Pandolfo et al 2010aPandolfo et al , 2010bNegishi and Kayaba 2010). These studies have helped define requirements for mussel propagation and culture by advancing understanding of factors affecting growth and survival and have shown that mussels are useful biological indicators of environmental change.…”

“…Due to their small size (<10-20 mm), juvenile mussels are difficult to detect in the wild, restricting field investigations to Downloaded by [Eastern Michigan University] at 12:55 09 October 2014 adult life stages and making it difficult to examine effects of temperature and other factors on early life stages (Negishi and Kayaba 2010). Though growth rates of juveniles from fieldbased studies are uncommon, researchers have begun to close this knowledge gap by utilizing laboratory-propagated juveniles for experimental studies, as we have done.…”

“…Water temperature is a significant environmental variable affecting growth and survival of juvenile mussels in captivity and in the wild, which also affects various reproductive processes in adults, such as gametogenesis, spawning, and larval brooding (Krebs 1972;Hastie et al 2000;Zimmerman and Neves 2002;Gosling 2003;Hastie et al 2003;Zimmerman 2003;Jones et al 2005;Negishi and Kayaba 2010;Pandolfo et al 2010b). Temperature can affect mussel developmental and physiological processes and also has specific effects on different life stages (Krebs 1972;Negishi and Kayaba 2010;Pandolfo et al 2010b). Efforts to propagate and culture mussels in captivity require an understanding of the environmental factors that influence growth and survival at different life stages.…”

Distribution patterns of freshwater molluscs along environmental gradients in the southern Guadiana River basin (SW Iberian Peninsula)

“…On the basis of these environmental characteristics and the combination of physiological, trophic, and reproductive patterns discussed above, five distribution models were found: 1. the greater species richness of native gastropods in permanent headwater streams, both stenochoric (A. wolfi) and widely distributed species (G. truncatula, R. balthica, P. metidjensis), is also related to ecological factors linked to the low diversity and abundance of fish in these streams and, thus, low predation pressure (Wellborn et al, 1996;Doadrio, 2001;Pilliod & Peterson, 2001); 2. the habitat preferences of euryhaline native gastropod species (M. emiliana, P. ulvae and M. myosotis) responds, mainly, to physiological adaptations to high water conductivity levels, together with a variety of tidal habitat requirements (Berger & Gorbushin, 2001;Piscart et al, 2005;Cardoso et al, 2007), which also means that, unlike the headwater communities, estuarine gastropod communities have a more simple organization based on a low number of species resistant to sudden, large changes in conductivity (Piscart et al, 2006); 3. to maximize their reproduction and growth, naiads (bivalves of the genera Anodonta, Unio and Potomida) select permanent lowland water courses close to the central axis of the Guadiana River, with moderate slopes and muddy substrate (high turbidity) (Morris & Corkum, 1999;Negishi & Kayaba, 2010); 4. both genus Pisidium bivalve species occupy steep slopes-streams, located at great distances from the Guadiana River axis, probably reflecting their preference for permanent headwater environments (Dussart, 1976;Holopainen, 1980;Gallardo et al, 1994); and 5. the distribution of the eurychoric native gastropod species A. cf. fluviatilis reveals their opportunistic behaviour; they colonize highly variable Mediterranean environments (Gallardo et al, 1994;Kefford & Nugegoda, 2005) and so can be found in headwater, lowland, and tidal temporary or permanent streams (Gallardo et al, 1994;Bennike & Lemke, 2001;Kefford & Nugegoda, 2005;Kefford et al, 2007;Zalizniak et al, 2009).…”

Recruitment, abundance, and predation on the blue mussel (Mytilus edulis) on northeastern estuarine rocky shores

“…First, we know that rates of biomass accumulation in mussels decrease with size: smaller mussels gain more mass per unit time than larger individuals (e.g., Sukhotin et al 2002, Negishi andKayaba 2010). Second, differently sized mussels rely on overlapping (if not completely equivalent) resource pools: according to Widdows et al (1979), adult mussels are non-selective filter feeders whose gills retain all particles larger than 5 lm.…”