Rosario Domínguez-Petit

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

Abstract The 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.

Exhaustive comparison of colour texture features and classification methods to discriminate cells categories in histological images of fish ovary

The estimation of fecundity and reproductive cells (oocytes) development dynamic is essential for an accurate study of biology and population dynamics of fish species. This estimation can be developed using the stereometric method to analyse histological images of fish ovary. However, this method still requires specialised technicians and much time and effort to make routinary fecundity studies commonly used in fish stock assessment, because the available software does not allow an automatic analysis. The automatic fecundity estimation requires both the classification of cells depending on their stage of development and the measurement of their diameters, based on those cells that are cut through the nucleous within the histological slide. Human experts seem to use colour and texture properties of the image to classify cells, i.e., colour texture analysis from the computer vision point of view. In the current work, we provide an exhaustive statistical evaluation of a very wide variety of parallel and integrative texture analysis strategies, giving a total of 126 different feature vectors. Besides, a selection of 17 classifiers, representative of the currently available classification techniques, was used to classify the cells according to the presence/absence of nucleous and their stage of development. The Support Vector Machine (SVM) achieves the best results for nucleous (99.0% of accuracy using colour Local Binary Patterns (LPB) feature vector, integrative strategy) and for stages of development (99.6% using First Order Statistics and grey level LPB, parallel strategy) with the species Merluccius merluccius, and similar accuracies for Trisopterus luscus. These results provide a high reliability for an automatic fecundity estimation from histological images of fish ovary.

Intraspecific variability in reproductive patterns in the temperate hermaphrodite fish, Labrus bergylta

For many fish populations reproductive patterns remain unknown, which often results in inadequate management strategies. Timing and intraspecific variability in the main reproductive traits of ballan wrasse (Labrus bergylta) were investigated based on microscopic analysis of gonads sampled from NW Spain in 2009–2012. This species displays two main body colour patterns, plain and spotted, which coexist in sympatry. Females spawned from January to April whereas spawning capable males were present almost year-round. Length at 50% maturity did not differ between colour patterns and was above the minimum catch size. Plain individuals attained the length and age at 50% sex change earlier than spotted individuals, which might be explained by differences in growth patterns, mortality rates or by an evolutionary genetic divergence between populations. Individuals with gonads infected by encysted trematode metacercariae were associated with an earlier timing of sex change, which represents one of the few examples of a possible parasitic influence on the sex allocation of its host. Our findings provide a framework for scientific-based management of this hermaphrodite fish.

Evaluating the use of the autodiametric method for estimating fecundity of Reinhardtius hippoglossoides, a species with an unusual oocyte development strategy

Evaluating the use of the autodiametric method for estimating fecundity of Reinhardtius hippoglossoides, a species with an unusual oocyte development strategy R. Dominguez-Petit*, R. M. Rideout, D. Garabana, Y. Lambert, M. Hermida, and M. J. Morgan Spanish Institute of Oceanography, Oceanographic Centre of Vigo, Vigo, Spain Institute of Marine Research-CSIC, Vigo, Spain Fisheries and Oceans Canada, Northwest Atlantic Fisheries Centre, St John’s, NL, Canada Spanish Institute of Oceanography, Oceanographic Centre of A Coru~na, A Coru~na, Spain Fisheries and Oceans Canada, Institute Maurice-Lamontagne, Mont-Joli, QC, Canada *Corresponding author: tel: þ34 98 646 2271; fax: 986498626; e-mail: rosario.dominguez@ieo.es.

Govocitos: A software tool for estimating fish fecundity based on digital analysis of histological images

Abstract To estimate productivity of a fish stock, the precise determination of fish fecundity is essential. The stereological method accurately estimates fecundity from histological images of a fish gonad. For that purpose, a hexagonal grid is overlaid on the histological image and the number of grid points associated to each oocyte (reproductive cells) category and the number of oocytes in each category is counted. This process is done manually often using off-the-shelf software, but it is very time-consuming, requires specialized technicians, and does not allow to review the calculations. In this paper, we describe and evaluate the software Govocitos, which offers an easy and automatic way to estimate fecundity using the stereological method. Govocitos contains a module to automatically detects the matured oocytes in the slice (nearly 80% of oocytes are correctly detected) and a module to automatically classify the oocytes according to the presence/absence of nucleus (with 84% of accuracy) and to three development stages (with 87% of accuracy). It also provides a user friendly GUI that allows the experts to modify the outlines and classifications of oocytes, to calculate diameters, areas and roundness, to build diameter frequency histograms, to count the points and objects inside the grid, to estimate partial and potential fecundity and to export the data to files and into a database. In addition, Govocitos provides the possibility of varying grid characteristics, it can be trained to work with different species and it allows to check and supervise the calculations whenever needed including in a later point in time. Govocitos is a free software that can be downloaded from http://lia.ei.uvigo.es/daeira/software/govocitos or http://citius.usc.es/w/govocitos .

A Multi-platform Graphical Software for Determining Reproductive Parameters in Fishes Using Histological Image Analysis

Govocitos is a multi-platform application designed to integrate all processes to estimate the fecundity of fish, a fundamental issue for the management of sustainable fisheries. Govocitos incorporates supervised and unsupervised algorithms to extract oocytes and their features in digitized histological images. Oocytes are classified automatically into the classes used traditionally in studies of reproductive ecology. A database gives support to allow for reproducible data management and to share results among different laboratories. The output of Govocitos has been evaluated through extensive validation procedures and found to be precise and accurate. Govocitos is open source software running on Linux and Windows platforms.