Shell drilling and gonad biopsies provide a rapid, nonlethal method for in situ assessment of reproductive periodicity in a turbinid gastropod

Abstract

Reproductive data on marine molluscs are imperative for informing conservation and management strategies. Most methods for assessing reproductive periodicity are lethal, which could be unfavourable for fragile populations. This study aimed to trial a nonlethal, drill-biopsy technique for assessing the reproductive cycle in the turbinid gastropod, Turbo militaris. This technique was tested in the laboratory, where a small hole was drilled into the shell, from where a biopsy of the gonad was taken. The procedures resulted in zero mortalities and rapid recovery of the animals when returned to seawater. Sex was identified by viewing the gonad colour through the shell hole and confirmed by viewing gametes from a biopsy. Preservation of the female biopsy was investigated, with buffered formalin found to be the most suitable solution. The drill-biopsy method was also tested in the field; five (out of six) recaptured T. militaris had repaired the shell hole after 6 weeks, and two were recaptured on multiple occasions up to the end of this study, 10 months later. The size–frequency distributions of oocytes from female biopsies suggested an increase in mode size over 2 months with a shift towards a higher number of larger oocytes, supporting the practicality of this nonlethal approach to evaluate reproductive periodicity and sex determination. Nonlethal sampling is recommended for broad-scale studies and populations under stress; methods, such as the drill-biopsy technique, facilitate reproductive sampling without detriment to the target populations.