Growth parameters of endangered freshwater pearl mussel (Margaritifera laevis, Unionoida)

Abstract

Abstract:We observed periodic increments of the annuli to verify the annual growth-age relationship in two populations of a freshwater pearl mussel, Margaritifera laevis (Bivalvia, Unionoida), in northern Japan and confi rmed that one annulus is added each year. The relationship between yearly shell growth and age was regarded as a unimodal distribution. We fi tted several growth models to the shell length-age relationships of these two populations, which had different densities and age distributions. The Gompertz function showed the best fi t, in terms of both RSS (residual sum of squares) and the difference between the observed maximum shell length and the asymptotic shell length. The life span of M. laevis was shorter than that reported for Margaritifera margaritifera populations at higher latitudes (≥ 50°N), which have been widely recognized as threatened. Margaritiferid mussels living at lower latitudes tend to have shorter life spans and smaller maximum size. These results suggest that margaritiferid mussels in southern regions such as M. laevis in Japan and M. margaritifera in Spain may be particularly vulnerable when conditions are unsuitable for juvenile mussels for prolonged periods.

How parasite-mediated costs drive the evolution of disease state-dependent dispersal

“…Indeed, infection during (and after) dispersal is observed in a bird species (Knowles et al, 2013), and recovery during dispersal is also observed in salmon that are infected with the larvae of freshwater pearl-mussels (e.g. Morales et al, 2006;Akiyama and Iwakuma, 2009;Terui et al, 2014). Thus, the bias predictor presented here plays an essential role in understanding the distribution of hosts and parasites in these systems.…”

“…Similarly, if infected hosts have a chance of recovery during dispersal (e.g. salmon that is parasitised by the larvae of freshwater pearl-mussels), infected individuals are expected to have strong incentives for dispersing (Morales et al, 2006;Akiyama and Iwakuma, 2009;Terui et al, 2014). These biased dispersal propensities are important for population biology, because if S-biased dispersal is observed in a metapopulation, parasites fail to spread over space.…”

Trace element composition of freshwater pearl mussels Margaritifera spp. across Eurasia: Testing the effect of species and geographic location

“…The lifespan and shell flexibility of Margaritifera species strongly depend on environmental conditions (Akiyama and Iwakuma, 2009;Bolotov et al, 2013). For example, Margaritifera margaritifera mussels living in the lower reaches of rivers grow faster than those living in the upper reaches, and the maximum size and age differ among sampling sites along the same river (Hastie et al 2000;Akiyama and Iwakuma, 2009).…”

Age, Growth and Mortality of Unio tigridis (Bourguignat, 1852)

“…Alternative growth models with the VBGM, therefore, have been used to describe the growth in comparative studies (Hastie et al, 2000;Haddon, 2001). Akiyama and Iwakuma (2009), fitted several growth models (Hyperbolic, Gompertz, Logistic and von Bertalanffy growth functions) to the shell length-age relationships for two populations (Shiribetsu river and Chitose river) of a freshwater pearl mussel, Margaritifera laevis (Bivalvia, Unionoida), in northern Japan. They found that the Gompertz function showed the best fit, in terms of both RSS (residual sum of squares) and the difference between the observed maximum shell length and the asymptotic shell length.…”