Age determination, growth rate and population structure of the horse musselModiolus modiolus

Abstract

The age and growth rate of Modiolus modiolus have been studied from acetate peel replicas of polished and etched shell sections. Age estimates could be reliably obtained from the alternating patterns of light (summer) and dark (winter) growth lines present in the middle nacreous layer of the shell. Growth lines in the inner nacreous layer, however, generally converged to form blocks of nacre such that the identity of individual lines was lost, whilst in the umbones growth lines were often tightly compressed and difficult to resolve. Data obtained from analyses of the internal growth lines in the middle nacreous layer were used to construct growth curves for several subtidal populations using the von Bertalanffy growth equation. The fastest growth rate was recorded for mussels growing epifaunally on the legs of a drilling platform in the North Sea; these mussels achieved a maximum shell length of 110 mm within ten years. The oldest mussel (from Ling Bank in the northern North Sea) was 48 years old and measured 133 mm in length whilst the largest mussel (from Loch Spelve in western Scotland) was 147 mm long and 38 years old. With the exception of the relatively young population (maximum age 10 years) from the drilling platform, most of the benthic populations studied included mussels in excess of 35 years of age. It is clear, therefore, that M. modiolus is a potentially long-lived member of the subtidal benthos.

Assessing the history of trace metal (Cu, Zn, Pb) contamination in the North Sea through laser ablation-ICP-MS of horse mussel Modiolus modiolus shells

“…Horse mussels Modiolus modiolus, dominant members of many shallow-water benthic communities, are widely distributed and can attain ages in excess of 35 yr (Anwar et al 1990). The present study investigates 2 North Sea populations of horse mussels, 1 from an 'impacted waste dump' site to the east of the Humber estuary, which has historically received a mixture of sewage sludge and industrial waste (e.g.…”

Age and growth in three populations of Dosinia exoleta (Bivalvia: Veneridae) from the Portuguese coast

“…In some bivalve species, age can be estimated by counting the number of growth rings deposited in the umbonal region of the shell (e.g. Anwar et al 1990;Ridgway et al 2011;Cardoso et al 2012;Peharda et al 2012). However, this was unfeasible with D. exoleta, since in most acetate peels the growth rings in the umbonal region were absent or very difficult to discern.…”

“…These constraints have been overcome by analysing internal shell microgrowth banding patterns revealed in acetate peel replicas of sectioned shells (Jones et al 1990;Ramón and Richardson 1992;Richardson 2001). Although being a timeconsuming method, internal growth lines visible in acetate peel replicas generally provide a reliable record of the age and growth history of individuals (Anwar et al 1990). However, some problems in the identification of the annual ring may also occur, especially in long-lived species.…”

“…In addition, in older individuals growth becomes slower and the later growth rings are deposited very close together at the shell margin, making them hardly discernible (Deval and Oray 1998;Ezgeta-Balić et al 2011). Furthermore, in some years clearly defined rings may not be formed (Anwar et al 1990). In some species, age can also be estimated by counting the growth lines visible in acetate peel replicas of the umbonal region of the shell (e.g.…”

“…In some species, age can also be estimated by counting the growth lines visible in acetate peel replicas of the umbonal region of the shell (e.g. Anwar et al 1990;Ridgway et al 2011;Peharda et al 2012).…”