An Examination of Non-Destructive Methods for Differentiating Between Yellow Lampmussel (Lampsilis cariosa) and Tidewater Mucket (Atlanticoncha ochracea)

Abstract

Conservation and management of imperilled freshwater mussel populations (Order Unionida) rely on the ability to distinguish between species occupying the same habitat. Standard methods of mussel identification have relied on external and internal shell characteristics. However, distinguishing species based on shell form can be challenging due overlapping traits across species and phenotypic plasticity. Furthermore, examination of internal shell features requires destructive sampling, which is not ideal for imperilled taxa. In Canada, Yellow Lampmussel (Lampsilis cariosa) is a species listed as “Special Concern” and is limited in distribution to isolated populations in Cape Breton, Nova Scotia, and New Brunswick. This mussel appears strikingly similar to another species, Tidewater Mucket (Atlanticoncha ochracea), and both species can reside within similar habitats. In a survey given to 29 people, participants were only able to correctly differentiate between Yellow Lampmussel and Tidewater Mucket 61.7% of the time using external shell characteristics. The objective of my honours thesis research was to explore alternative, non-destructive identification methods to differentiate between live Yellow Lampmussel and Tidewater Mucket, including morphometric analyses, comparisons of soft-tissue morphology, and molecular tools. A custom-designed multiplex PCR method was employed to validate the identification of the 36 Yellow Lampmussel and 20 Tidewater Mucket specimens used in this study. Ratios of linear shell measurements were 83.9% accurate in differentiating between species, while ratios of soft-tissue measurements showed greater success (90.6%), and size-corrected soft-tissue measurements (i.e., divided by shell length) had the highest reliability among all non-molecular methods (92.5%). Furthermore, notable differences in soft-tissue colour and colour pattern were observed between these species. Finding a reliable method of species identification that can be implemented in the field will be of enormous value to freshwater mussel ecologists. The results of this study provide a framework for this, but future studies employing larger sample sizes, wider geographic sampling, and standardized methods for assessing qualitative soft-tissue features will be required to validate a robust identification tool.