Misidentification of sex for Lampsilis teres, Yellow Sandshell, and its implications for mussel conservation and wildlife management

Abstract

Correct identification of sex is an important component of wildlife management because changes in sex ratios can affect population viability. Identification of sex often relies on external morphology, which can be biased by intermediate or nondistinctive morphotypes and observer experience. For unionid mussels, research has demonstrated that species misidentification is common but less attention has been given to the reliability of sex identification. To evaluate whether this is an issue, we surveyed 117 researchers on their ability to correctly identify sex of Lampsilis teres (Yellow Sandshell), a wide ranging, sexually dimorphic species. Personal background information of each observer was analyzed to identify factors that may contribute to misidentification of sex. We found that median misidentification rates were ~20% across males and females and that observers falsely identified the number of female specimens more often (~23%) than males (~10%). Misidentification rates were partially explained by geographic region of prior mussel experience and where observers learned how to identify mussels, but there remained substantial variation among observers after controlling for these factors. We also used three morphometric methods (traditional, geometric, and Fourier) to investigate whether sex could be more correctly identified statistically and found that misidentification rates for the geometric and Fourier methods (which characterize shape) were less than 5% (on average 7% and 2% for females and males, respectively). Our results show that misidentification of sex is likely common for mussels if based solely on external morphology, which raises general questions, regardless of taxonomic group, about its reliability for conservation efforts.

An alarming tendency towards freshwater mussel misidentification in scientific works may bias endangered and invasive species management

“…Discovery of ‘ P. exilis ’ in Lake Sentani (Surbakti, 2020) could be used as evidence for the introduction of one more representative of the Unionidae to New Guinea, but instead it is the first confirmed record of the tropical invasive lineage of S. woodiana on this island. It should be noted that works on ‘ M. margaritifera ’ [= S. woodiana ] from the Philippines (Joaquino et al, 2017) and ‘ A. cygnea ’ [= S. woodiana ] from Pakistan (Khan et al, 2018) have already been listed in global reviews on certain topics (Hess et al, 2018; Singh & Gupta, 2021). It is clear that all data from this dataset (Appendix ), being reused with the original (incorrect) taxonomic names, will cause further misconceptions (‘error cascades’) among scientists, conservationists and stakeholders from around the world.…”

“…cygnea' [=S. woodiana] from Pakistan (Khan et al, 2018) have already been listed in global reviews on certain topics (Hess et al, 2018;Singh & Gupta, 2021). It is clear that all data from this dataset (Appendix A), being reused with the original (incorrect) taxonomic names, will cause further misconceptions ('error cascades') among scientists, conservationists and stakeholders from around the world.…”

Pathology and infectious agents of unionid mussels: A primer for pathologists in disease surveillance and investigation of mortality events

“…140 Freshwater mussels can be sexed by assessing shell shape in sexually dimorphic species, visual inspection for pallor and inflation of the marsupium to assess gravidity, collection of gonadal fluid and staining to evaluate microscopically for developing gametes, and histopathologic identification of ovaries or testes. 47,88,134,171…”