Morphological abnormalities in gonads of the Baltic herring (Clupea harengus membras): Description of types and prevalence in the northern Baltic Sea

Abstract

Due to heavy anthropogenic influence and variation of the environmental conditions in the Baltic Sea, reproductive disorders are becoming a major environmental concern. We show here an increasing prevalence of gonadal malformations in the Baltic herring (Clupea harengus membras), a key species of the Baltic ecosystem and important in commercial fishery. During 1987-2014, the spawning herring population in the Archipelago Sea (AS) (North Baltic Sea, Finland) was monitored annually and analyzed for gross morphology of the gonads [total number (n) of analyzed fish = 38 284]. Four different types of malformations were repeatedly found and named as asymmetric, rudimentary, segmented, and branched gonads, but also hermaphroditic gonads and miscellaneous (unidentified) disorders were recorded. In 2013, additional samplings (n of fish analyzed = 541) showed similar malformations in herring from the Bothnian Sea. In some gonad types, histological examination revealed disintegration of seminiferous tubules and hyperplasia of the interstitial tissue. In 2014, the overall prevalence of malformations was still relatively low in the AS (frequency = 0-3.4 %; n = 750) and had apparently minimal effect on population recruitment. However, an increasing trend in the time-series (GLM; F = 32.65; p\0.001) and a significantly higher prevalence in the Bothnian Sea (frequency = 0.7-5.0 %; n = 541; v 2 = 6.24; p\0.05) suggest that gonadal malformations may become a new threat for fish in the Baltic Sea. The observed gonad atrophies may be due to environmental endocrine disruption; however, also other explanations may exist and potential explanations are discussed.

First abnormalities investigation in Mullus barbatus (Mullidae) from the Eastern Coast of Algeria

“…Due to its vulnerability to external perturbations reproduction is a sensitive environmental indicator (Rajasilta et al 2016). Many types of gonads malformations such as hermaphroditism, atrophy, compartmentations, and asymmetry have been described for a number of fish populations in both sexes (Bernet et al 2004;Hliwa et al 2011;Sopinka et al 2012;Rajasilta et al 2016).…”

“…Due to its vulnerability to external perturbations reproduction is a sensitive environmental indicator (Rajasilta et al 2016). Many types of gonads malformations such as hermaphroditism, atrophy, compartmentations, and asymmetry have been described for a number of fish populations in both sexes (Bernet et al 2004;Hliwa et al 2011;Sopinka et al 2012;Rajasilta et al 2016). Rajasilta et al (2016) have reported that asymmetry was the most frequent gonad type that deviated from normal in the Archipelago Sea, which was observed during the entire study period at varying but low frequencies.…”

“…Sopinka et al (2012) have reported that Porichthys notatus males in high-exposure areas exhibited more asymmetry in their testicles, shorter-headed sperm, and fewer living eggs in their nests. However, Rajasilta et al (2016) have suggested that asymmetric gonads would only be minor deviations from the usual and wouldn't impact the fish's ability to reproduce regularly. The causes of such anomaly are still unknown, but it has been shown that pathogens, parasites, and chemicals that produce crypto-endocrine or toxic effects can all have a significant impact on how fish gonads form and behave (Hliwa et al 2011;Sopinka et al 2012;Rajasilta et al 2016).…”

“…Lymphocystis disease is one of the oldest and most widespread viral diseases of fish (Borrego et al 2017). Different types of gonad malformations such as hermaphroditism, asymmetry, atrophy, segmented, branched gonads were described in many fish populations (Hliwa et al 2011;Rajasilta et al 2016). Skeletal deformities (kyphosis, lordosis, scoliosis, vertebral coalescence and fusion, fin abnormalities) are a major factor that affects the production cost (Berillis 2015).…”

Zooplankton Feeding Induces Macroscopical Gonad Malformations in Whitefish (Coregonus ssp.) from Lake Thun, Switzerland

“…Morphological abnormalities of the gonads is a phenomenon that has been reported from numerous wild fish populations [1][2][3][4][5][6][7][8][9][10][11][12][13][14]. These morphological alterations are of concern as they may be indicative of a disease and/or may impair the reproductive success of the populations [11,15,16].…”