Observations on growth and age of Hyridella menziesi Gray (Mollusca : Bivalvia) in a freshwater tidal lake

Abstract

The freshwater mussel offers considerable scope for study of the relationship between growth and life span. The combination of slow prolonged growth, low adult mortality and longevity are apparently unique in Invertebrate biology (Comfort 1957).

What is the value of knowledge of Molluscan geriatrics? The study of an aging population of fresh water bivalves has apparently little direct effect on man’s social or economic well-being. However man, in his investigation of fresh water communities and their productivity cannot ignore such a large standing crop of biomass, no matter how inert it may be. Likewise with increasing interest in the history of radioactive materials biologists are becoming aware of the value of long-lived organisms whose growth can be accurately dated.

Thus the purpose of this investigation has been to develop a method of measuring the age of the freshwater Molluscan bivalve Hyridella meziesi Gray and apply it broadly to a population in Lake Waipori.

Although the form of the shell is variable, it is considered to be within the variation for the species described by Dell (1953) and McMichael and Hiscock (1958). Both Dell and McMichael and Hiscock give no evidence for any species other than H. menziesi in South Island lakes.

The finding s of the investigation show the lake to be populated largely by aged mussels with one area where juveniles are fairly numerous. [Introduction]