The Use of Histological Techniques to Study the Reproductive Biology of the Hermaphroditic Mediterranean Fishes Coris julis, Serranus scriba, and Diplodus annularis

Alexandre Alonso‐Fernández,Josep Alós,Rosario Domínguez‐Petit,Fran Saborido‐Rey,Amalia Grau

doi:10.1080/19425120.2011.556927

Abstract

AbstractThe usefulness and importance of histological techniques in reproductive studies have been widely discussed for gonochoristic fish species. In the case of hermaphroditic fishes, histology is a particularly important tool for the proper identification of sexual pattern (i.e., sequential, simultaneous, or nonfunctional hermaphroditism). We used a histological approach to describe hermaphroditism, dynamics of follicle development, and spawning patterns in three species from the northwestern Mediterranean Sea (Balearic Islands, Spain): the Mediterranean rainbow wrasse Coris julis (sequential hermaphrodite), painted comber Serranus scriba (simultaneous hermaphrodite), and annular sea bream Diplodus annularis (nonfunctional hermaphrodite). Development of secondary growth follicles was asynchronous in all three species, and similar peaks in spawning activity occurred between May and July. However, notable differences in sexual cycle and egg production were found. For the painted comber, hydrated follicles were present in ovarian tissue almost every day during the peak of the spawning season, suggesting daily spawning and increasing the chances of autofertilization unless a mechanism to avoid this action is present in this species. Intersexual Mediterranean rainbow wrasses were identified, and the size and age at sex change were estimated to be 132 mm total length and 4 years, respectively. Previous investigators have concluded that the annular sea bream is a protandric hermaphrodite, but our results indicate nonfunctional hermaphroditism. These three species are of little commercial interest and are considered to be bycatch by the artisanal fleet, but they are vulnerable to the impacts of some recreational angling activities. Currently, no specific management plan has been developed for these species. We address the importance of describing sexual pattern and its implications for future conservation efforts.

Highlights

To understand fish population dynamics, it is essential to study reproductive biology, especially in exploited species
Previous investigators have concluded that the annular sea bream is a protandric hermaphrodite, but our results indicate nonfunctional hermaphroditism
These three species are of little commercial interest and are considered to be bycatch by the artisanal fleet, but they are vulnerable to the impacts of some recreational angling activities

Summary

Introduction

To understand fish population dynamics, it is essential to study reproductive biology, especially in exploited species. Beyond its importance for phylogenetic purposes (Sadovy and Domeier 2005; Sadovy de Mitcheson and Liu 2008), the classification of sexual pattern should be fundamental to the selection of fisheries conservation strategies because sex-changing species may be prone to overexploitation by size-selective fishing (Punt et al 1993; Alonzo and Mangel 2004; Molloy et al 2007; Sattar et al 2008). The purpose of the present study was to use a histological approach to establish the functional sexual pattern of each species and to delineate the organization of gonad development, the seasonal cycle of reproductive development, and the timing of spawning

Objectives

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Results

Conclusion