Effect of age on liver pathology and other diseases in flatfish: implications for assessment of marine ecological health status

Abstract

Age at disease onset, a familiar concept in human medicine, has not been commonly discussed in relation to diseases of wildlife. Furthermore, while age has been anecdotally linked with disease susceptibility in aquatic animals (e.g. in aquaculture), little attention has been devoted to health of specific cohorts in wild aquatic animal populations. In an attempt to refine current approaches to marine environmental monitoring programmes that utilise fish diseases as a sentinel for ecological status, we have investigated age at onset for 10 disease variables in the flatfish Limanda limanda, a commonly utilised species in such programmes in Europe. By comparing the prevalence of these variables (including several associated with liver neoplasia) in different age classes from the same sites, we have demonstrated an increased propensity for 'harm' (a cumulative measure of multiple disease variables) with age. Furthermore, a comparison of age-matched cohorts from geographically distinct offshore marine sites revealed that this tendency for increased harm differs in magnitude between sites. In these scenarios, the age at onset for key disease variables (such as pre-neoplastic and neoplastic pathologies of the liver) also differs between sites, with some locations containing populations with apparently increased susceptibility in younger age classes. We conclude that while age is an important variable when assessing fish population health status, it does not explain all of the differences in disease prevalence observed in natural populations, and further, that age-matched cohorts from certain populations have a higher propensity for disease than fish of the same age from other sites. The basis for these differences in susceptibility is discussed in relation to the prevailing burden of anthropogenic contaminants and to other natural factors (such as population genetics and migration) inherent in sampled populations.

Liver histopathology in Baltic eelpout (Zoarces viviparus) – A baseline study for use in marine environmental monitoring

“…However, before such a conclusion can be drawn, more research and data analyses are required, e.g., in order to study possible age effects. For instance, from studies in wild flatfish, it is known that young age groups tend to have less neoplastic liver nodules than their conspecifics of higher age groups Stentiford et al, 2010). An alternative explanation of the absence of neoplasms could be given by the example of the starry flounder.…”

Hyperpigmentation in North Sea dab Limanda limanda. II. Macroscopic and microscopic characteristics and pathogen screening

“…This suggests that colour pattern definition takes place at an early life stage and that, once established, the aberrant colour patterns are maintained through life. However, when Stentiford et al (2010) investigated the age at first occurrence of several disease conditions affecting dab in the North Sea and the Irish Sea where the smallest fish sampled were in the range of 10 to 14 cm (the majority of these being 1 yr old), the first occurrence of hyperpigmentation in North Sea dab was found to be at 3 yr . Similarly, data from a different area of the North Sea recorded the first occurrence of hyperpigmentation in 2 yr old dab, the smallest with 12 cm but higher prevalence observed in >15 cm fish (Grütjen et al 2013).…”

Histopathology and contaminant concentrations in fish from Kuwait’s marine environment

“…Biomarkers being either biochemical, physiological or histological are important to interpret the toxicity of the aquatic systems and have been widely used to assess environmental health (Myers et al, 1998;Fracácio et al, 2003;Costa et al, 2009;Stentiford et al, 2010;Brooks et al, 2009;Hutchinson et al, 2013;Stentiford et al, 2014). Significantly a number of field, laboratory and mesocosm studies have also demonstrated causal links between exposure to chemical contamination and the development of toxicopathic hepatic lesions (Hinton and Lauren, 1990;Hinton et al, 1992;Myers et al, 1998;Stehr et al, 2004).…”

“…Thus histological and biochemical biomarkers provide a powerful tool for detection and characterisation of the biological end points of toxicant and carcinogen exposure (Hinton and Lauren, 1990;Hinton et al, 1992;Moore and Simpson, 1992). Furthermore, the utility of histopathology as a sensitive indicator of health in wild fish populations has been demonstrated in Europe and North America (Myers et al, 1998;Costa et al, 2009;Stentiford et al, 2009;Vethaak et al, 2009;Stentiford et al, 2010).…”