The organophosphate pesticide -OP- malathion inducing thyroidal disruptions and failures in the metamorphosis of the Senegalese sole, Solea senegalensis.

BACKGROUND: Organophosphate pesticides-OP-, like malathion, can alter the normal functioning of neuro-endocrine systems (e.g., hypothalamus-pituitary-thyroid-HPT- axis), and to interfere on the thyroidal homeostasis. Through direct interactions with thyroid receptors, an/or indirectly via up-stream signalling pathways, from the HPT axis (i.e., negative feedback regulation), malathion possess the ability to affect integrity of thyroidal follicular tissue, and it can also block or delay its hormonal functioning. This insecticide can alter the majority of the ontogenetic processes, inducing several deformities, and also provoking decreases in the growth and survival patterns. The present study has been performed to determine the sublethal effects of malathion during the first month of life of the Senegalese sole, Solea senegalensis, and it is mainly focused on the metamorphosis phase. Different transcript expression levels (i.e. thyroid receptors, matrix and bone -Gla-proteins) and immunohistochemical patterns (i.e. thyroid hormones, osteocalcin, cell proliferation) have been analysed during the most critical phases of the flatfish metamorphosis, that is, through differentiation of thyroid system and skeletal development, migration of the eye, and further adaptation to benthic behaviours. RESULTS: In early life stages of the Senegalese sole, the exposure to the highest concentration of malathion (6.25 µg/L) affected to the growth patterns, showing the exposed individuals, a reduction around 60 and 92% of the total length and the dry weigth, respectively. In paralell, a significant reduction of the thyroid follicles (i.e., size and number) it was also been recorded, in a dose-dependent way. Abnormal phenotypes induced in the exposed larvae, did not complete the process of metamorphosis, and displayed several morphological abnormalities and developmental disorders, which were mainly associated with the eye migration process, and with thyroidal and skeletal disorders (i.e., transcriptional and protein changes of thyroid hormones and receptors, and of matrix and bone Gla proteins distribution), that conduced to an inadequate adaptation to the benthic life. CONCLUSIONS: In the Senegalese sole, the majority of the ontogenetic alterations induced by the exposure to malathion were mainly associated to the metamorphosis period, which is a thyroid-driven proccess. In fact, most crucial and transitional ontogenic events, appeared notably disturbed, for e.g., thyroid gland differentiation and functioning, migration of eye, skeletal development and benthonic behaviors.

Skeletal Anomalies in Senegalese Sole ( Solea senegalensis), an Anosteocytic Boned Flatfish Species.

Skeletal anomalies affect animal welfare and cause important economic problems in aquaculture. Despite the high frequency of skeletal problems in reared Solea senegalensis, there is lack of information regarding the histological features of normal and deformed vertebrae in this flatfish. The aim of this study was to describe the histopathological and radiographical appearance of vertebral body anomalies. Sixty-seven juvenile fish were radiographically examined 104 or 105 days after hatching. Through radiographic images, vertebral segments were selected and processed for histopathological examination from 7 normal and 7 affected fish. Alterations in bone shape and vertebral fusion were the most significant anomalies in the vertebral bodies. These alterations occurred most frequently between the last 3 abdominal vertebrae and the first 10 caudal centra. Radiographically, deformed vertebrae showed flattening of the endplates and narrowing of the intervertebral spaces. The radiographic findings concurred with the histological lesions where affected vertebrae exhibited irregular endplates and changes in trabecular bone. Radiolucent cartilaginous tissue was evident in the endplates of the deformed vertebra and, in some cases, the cartilaginous material extended from the growth zone into the intervertebral space. These changes were likely the primary alterations that led to vertebral fusion. Fused vertebrae were often reshaped and showed a reorganization of the trabeculae. The formation of metaplastic cartilage is frequent in a variety of anomalies affecting teleost species.

Abnormalities in flatfishes of the south-west Atlantic Ocean.

Five adult paralichthyid specimens with various kinds of abnormalities are reported from the south-west Atlantic Ocean. These abnormal flatfish specimens represent the first records of wholly ambicoloured Paralichthys orbignyanus specimens having a deep notch between the eye and dorsal fin and a partially albinistic specimen having skeletal deformities and only the second record of an almost totally ambicoloured specimen. We also report the first observation of reversal in Paralichthys patagonicus and an almost totally ambicoloured, reversed Xystreurys rasile.

Skeletal anomalies in reared Senegalese sole Solea senegalensis juveniles: a radiographic approach.

Reared Senegalese sole Solea senegalensis Kaup show a high incidence of vertebral anomalies; however, little is known about its skeletal anomaly profile in the later farming phases. The purpose of this study was to provide a detailed description and quantification of the most common skeletal anomalies in reared Senegalese sole in the juvenile stage by means of computed radiography. A total of 374 Senegalese sole were classified according to the external morphology of the fish as normal or altered and then radiographed in latero-lateral and in dorso-ventral projections. Radiographic evaluation of anomalies focused especially on vertebral body anomalies (VBA) and vertebral column deviations (VCD). The 2 orthogonal projections provided a more complete visualization of the skeleton. Approximately 75% of the individuals showed at least 1 anomaly, while VBA and/or VCD were detected in 48.9% of the specimens. Regarding external morphology, 88% of the fish were categorized as normal, although about 72% of these normal fish displayed abnormalities in radiographies. The most frequent anomalies consisted of deformations of the caudal complex plates (hypurals, parhypural and epural), preurals and caudal vertebrae. Scoliosis was the most prevalent among VCD, affecting the caudal area in almost 15% of the individuals. The anomaly profile at the juvenile stages showed some differences compared to what has been reported previously in earlier stages of development. In light of these results, further investigation into the progression of skeletal anomalies over time and the causative factors at later stages is required.

New insight on vertebral anomalies in cultured Senegalese sole (Solea senegalensis, Kaup) at early stages of development.

Senegalese sole (Solea senegalensis, Kaup) is a promising flatfish species in aquaculture. However, skeletal anomalies are still a great concern in sole farming. Investigation of this issue is crucial to improving larval quality and optimizing production. The aim of this study was to thoroughly assess anomalies in the rachis of reared sole at early developmental stages. Sole (n = 507) were sampled at 31 or 32 days after hatching (dah). The specimens were stained with alcian blue and alizarin red and evaluated for the detection of vertebral deformities. Most fish presented 9:34:3 vertebrae in abdominal, caudal and caudal complex regions, respectively. Remarkably, all specimens showed at least one spinal anomaly. Alterations of neural/haemal elements, as well as deformities of hypurals, parhypural and epural, were recurrent. Vertebral body anomalies and/or vertebral column deviations were identified in 52% of the individuals. Vertebral deformations and fusions were common, especially in caudal complex. 'Minor' anomalies were predominant, and some of the detected disorders might be a result of non-/low-pathological processes. These results contribute a new insight into the main skeletal anomalies affecting cultured sole larvae. Further research is required to determine their impact on fish welfare and external appearances at commercial stages.

Oxidative stress parameters in juvenile brazilian flounder Paralichthys orbignyanus (Valenciennes, 1839) (Pleuronectiformes: Paralichthyidae) exposed to cold and heat shocks

The aim of this study was to determine oxidative stress parameters in the liver and gill of Brazilian flounder juveniles (307.0 ± 16.0 g and 30.0 ± 4.0 cm) submitted to different water temperature (17.1, 23.0 and 28.8ºC) for 72 h and maintained at salinity 25‰. After the acclimation of 7 days, in 23ºC, fish were transferred to 200 L tanks containing seawater (salinity 25‰) at 28.8ºC (heat shock), 17.1ºC (cold shock) or 23.0ºC (control), five replicates (five fish tank-1). The sampled collection occurred in 0 (pre-challenge), 3, 24, 48 and 72 h after temperature shock. Flounder exposed to 17.1ºC and 28.8ºC showed significantly higher TBARS levels and GST activity in the liver post-exposition (PE) in relation to the control (23ºC). CAT activity in liver present a significantly increase at 17.1ºC, in first 48 h, and subsequently decrease in 72 h PE in relation to 28.8ºC. The gills of flounder showed significantly higher TBARS levels, GST and CAT activity when submitted at 17.1 and 28.8ºC in relation to 23.0ºC. There were observed changes in lipid peroxidation levels (LPO), CAT and GST activities in the liver and gill of Brazilian flounder in response to reactive oxygen species (ROS) produced by thermal shocks.

O objetivo deste estudo foi determinar os parâmetros de estresse oxidativo no fígado e brânquias de juvenis de linguado (307,0 ± 16,0 g e 30,0 ± 4,0 cm) submetidos a diferentes temperaturas da água (17,1, 23,0 e 28,8ºC) por 72 h e mantidos na salinidade de 25‰. Após uma aclimatação de sete dias, em 23ºC, os peixes foram transferidos para tanques de 200 L contendo água do mar (salinidade 25‰) em 28,8ºC (choque quente), 17,1ºC (choque frio) ou 23,0ºC (controle), cinco repetições (cinco peixes/tanque). A coleta de amostras ocorreu em 0 (pré-exposição), 3, 24, 48 e 72 h após o choque térmico. O linguado exposto a 17,1ºC e 28,8ºC apresentaram um significante aumento dos níveis de TBARS e atividade da GST no fígado pós-exposição (PE) em relação ao controle (23ºC). A atividade da CAT no fígado apresentou um aumento significativo em 17,1ºC, nas primeiras 48 h, e subsequente diminuição em 72 h PE em relação a 28,8ºC. As brânquias do linguado apresentaram significante aumento dos níveis de TBARS e atividade da GST e CAT quando submetidos a 17,1ºC e 28,8ºC em relação a 23,0ºC. Foram observadas alterações nos níveis de peroxidação lipídica (LPO) e atividade de GST e CAT no fígado e brânquias de linguado em resposta as espécies reativas de oxigênio (ROS) produzidas pelo choque térmico.

Defective skeletogenesis and oversized otoliths in fish early stages in a changing ocean.

Early life stages of many marine organisms are being challenged by rising seawater temperature and CO2 concentrations, but their physiological responses to these environmental changes still remain unclear. In the present study, we show that future predictions of ocean warming (+4°C) and acidification (ΔpH=0.5 units) may compromise the development of early life stages of a highly commercial teleost fish, Solea senegalensis. Exposure to future conditions caused a decline in hatching success and larval survival. Growth, metabolic rates and thermal tolerance increased with temperature but decreased under acidified conditions. Hypercapnia and warming amplified the incidence of deformities by 31.5% (including severe deformities such as lordosis, scoliosis and kyphosis), while promoting the occurrence of oversized otoliths (109.3% increase). Smaller larvae with greater skeletal deformities and larger otoliths may face major ecophysiological challenges, which might potentiate substantial declines in adult fish populations, putting in jeopardy the species' fitness under a changing ocean.