Accumulation, Depuration, and Biological Effects of Polystyrene Microplastic Spheres and Adsorbed Cadmium and Benzo(a)pyrene on the Mussel Mytilus galloprovincialis

Filter feeders are target species for microplastic (MP) pollution, as particles can accumulate in the digestive system, disturbing feeding processes and becoming internalized in tissues. MPs may also carry pathogens or pollutants present in the environment. This work assessed the influence of polystyrene (PS) MP size and concentration on accumulation and depuration time and the role of MPs as vectors for metallic (Cd) and organic (benzo(a)pyrene, BaP) pollutants. One-day exposure to pristine MPs induced a concentration-dependent accumulation in the digestive gland (in the stomach and duct lumen), and after 3-day depuration, 45 µm MPs appeared between gill filaments, while 4.5 µm MPs also occurred within gill filaments. After 3-day exposure to contaminated 4.5 µm MPs, mussels showed increased BaP levels whilst Cd accumulation did not occur. Here, PS showed higher affinity to BaP than to Cd. Three-day exposure to pristine or contaminated MPs did not provoke significant alterations in antioxidant and peroxisomal enzyme activities in the gills and digestive gland nor in lysosomal membrane stability. Exposure to dissolved contaminants and to MP-BaP caused histological alterations in the digestive gland. In conclusion, these short-term studies suggest that MPs are ingested and internalized in a size-dependent manner and act as carriers of the persistent organic pollutant BaP.

Comparative anatomical studies on the cranial nerves of the fully formed embryos of the Nile tilapia Oreochromis niloticus (Ostiechthyes-Cichlidae). I. Nervus glossopharyngeus

The organization of the roots, ganglia and the peripheral distribution of the cranial nerves of the fully formed embryos of Oreochromis niloticus are examined in the transverse serial sections. These nerves carry fibers, which were also analyzed. The results of this study demonstrated that the glossopharyngeal nerve originates by means of only one root, which leaves the cranium through the glossopharyngeal foramen. This nerve gives fibers (visceromotor) to the first internal and external levator arcus branchialis muscles. There is a single epibranchial (petrosal) ganglion located extracranially. Nervus glossopharyngeus has three rami; pharyngeus, pretramticus and posttrematicus. The ramus pharyngeus carries only viscerosensory fibers; general for the pharyngeal epithelium and special ones for the pseudobranch. General viscerosensory fibers are also carried by rami pretrematicus and posttrematicus for the pharyngeal epithelial lining. The special sensory fibers are carried by the ramus pretrematicus for the taste buds and by ramus posttrematicus for the gill filaments. The ramus pretrematicus also carries visceromotor fibers for the first adductor arcus branchialis and to the first obliquus ventralis muscles.

First Integrative Morphological and Genetic Characterization of Tremoctopus violaceus sensu stricto in the Mediterranean Sea

An integrative approach based on morphological and genetic analyses was undertaken for the first time to confirm the species identification of Mediterranean samples belonging to the genus Tremoctopus. Sequences of two mtDNA genes (cytochrome c oxidase subunit (COI) and 16S) were generated for the first time from Mediterranean samples. Both the similarity-based identifications and tree-based methods indicated that three females can be identified as Tremoctopus violaceus sensu stricto in agreement with their morphological classifications. All Mediterranean sequences clustered with the sequences of Tremoctopus violaceus from the Gulf of Mexico and were clearly differentiated from the sequences attributed to T. gracilis and T. robsoni. The chromatic pattern of the web and some features of gill filaments, arms formula, stylets, radulae, beaks, and stomach contents were given for all the samples; 105,758, 20,140, and 11,237 oocytes were estimated in the mature, immature, and developing samples, respectively. The presence of four spermatangia inside the cavity of the maturing female suggested the ability of this species to mate before reaching full maturity with more partners. Age investigation using beaks, performed for the first time in T. violaceus and within the genus gave results consistent with the different sizes and maturity conditions of the samples.

Experimental Induction of Tenacibaculosis in Atlantic Salmon (Salmo salar L.) Using Tenacibaculum maritimum, T. dicentrarchi, and T. finnmarkense

There is a limited understanding of the pathogenesis of tenacibaculosis in Atlantic salmon (Salmo salar L.) and there are few reproducible exposure models for comparison. Atlantic salmon were exposed via bath to Tenacibaculum maritimum, T. dicentrarchi, or T. finnmarkense, and were then grouped with naïve cohabitants. Mortalities had exaggerated clinical signs of mouthrot, a presentation of tenacibaculosis characterized by epidermal ulceration and yellow plaques, on the mouth and less frequently on other tissues. Histopathology showed tissue spongiosis, erosion, ulceration, and necrosis ranging from mild to marked, locally to regionally extensive with mats of intralesional bacteria on the rostrum, vomer, gill rakers, gill filaments, and body surface. Exposure to T. maritimum resulted in less than a 0.4 probability of survival for both exposed and cohabitants until Day 21. Exposures to T. dicentrarchi resulted in 0 and 0.55 (exposed), and 0.8 and 0.9 (cohabitant) probability of survival to Day 12 post-exposure, while T. finnmarkense had a 0.9 probability of survival to Day 12 for all groups. This experimental infection model will be useful to further investigate the pathogenesis of tenacibaculosis, its treatment, and immunity to Tenacibaculum species.

Oribatid mites (Acariformes, Sarcoptiformes: Oribatida) in the gills of Salmo spp. (Actinopterygii: Salmonidae) parr – Short communication

Live oribatid mites of the family Malaconothridae were found on Salmo spp. parr caught in the rivers of Northwest Russia. The mites were localised in the gill filaments and enclosed in connective tissue capsules. The encapsulation was accompanied by hyperplasia and displacement of the respiratory epithelium. One mite specimen was an adult female, while all the other specimens were protonymphs. The adult female and one protonymph specimen were identified as Tyrphonothrus sp. Other protonymphs could be identified only at the family level. The obtained partial 18S rDNA sequence of one protonymph was 100% identical to that of Tyrphonothrus maior (NCBI accession No. KY922215). This is the first report of living malaconothrid mites encapsulated in fish gills, and the phenomenon may assume parasitic behaviour. However, the nature of the relationship between the mites and the fish requires further investigations.

Health Status Comparison of Blood Cockle (Tegillarca granosa) between Low and High Yield Farms in Selangor and Johor

This study aims to provide insight knowledge on the potential reason for low blood cockles (Tegillarca granosa) production in Sungai Buloh Selangor by comparing the condition indices and histology of the gills and gonad with samples from a high yield farm at Sungai Ayam, Johor. Samples were collected in September 2020 and grouped for histological analysis and for condition indices. About 60% individuals from Sungai Buloh and 20% of samples from Sungai Ayam found with degenerated gill filaments. The sex ratio were found identical (50%:50% male to a female) in samples from Sungai Ayam, while 40%: 60% of male to female from Sungai Buloh. The gonad of males found at Stage 2 (developing) and Stage 3 (developed or ripe) and the ovaries at Stage 3 and Stage 4 (spawning) for Sungai Buloh, and between Stage 2 to Stage 4 from Sungai Ayam. The total condition index (CI Tot) was significantly differences between farms. Findings indicate sample from Sungai Buloh has low health status due to poor gill’s filaments condition, and ripe ovaries found in lightweight (2 g) T. granosa. Hence being the potential reason for low survival rate in the Sungai Buloh.

Rapid embryonic development supports the early onset of gill functions in two coral reef damselfishes

The gill is one of the most important organs for growth and survival of fishes. Early life stages in coral reef fishes often exhibit extreme physiological and demographic characteristics that are linked to well-established respiratory and ionoregulatory processes. However, gill development and function in coral reef fishes is not well-understood. Therefore, we investigated gill morphology, oxygen uptake, and ionoregulatory systems throughout embryogenesis in two coral reef damselfishes, Acanthochromis polyacanthus and Amphiprion melanopus (Pomacentridae). In both species, we found key gill structures to develop rapidly early in the embryonic phase. Ionoregulatory cells appear on gill filaments 3-4 days post fertilization and increase in density, whilst disappearing or shrinking in cutaneous locations. Primary respiratory tissue (lamellae) appears 5-7 days post fertilization, coinciding with a peak in oxygen uptake rates of the developing embryos. Oxygen uptake was unaffected by phenylhydrazine across all ages (pre-hatch), indicating that haemoglobin is not yet required for oxygen uptake. This suggests that gills have limited contribution to respiratory functions during embryonic development, at least until hatching. Rapid gill development in damselfishes, when compared to most of the previously investigated fishes, may reflect preparations for a high-performance, challenging lifestyle on tropical reefs, but may also make reef fishes more vulnerable to anthropogenic stressors.

Epizootic aspects of young carp contamination with Dactylogyrosis in the ponds of the Orenburg region

Modern fish farming having intensive forms of farming provides for feeding fish with artificial feed, fertilizing ponds and compacting fish planting in nursery, finishing and wintering ponds. This leads to close contact of cultivated fish and, in this regard, favorable conditions for the pathogens accumulation in ponds, the distribution of infectious and invasive diseases. Invasive diseases are a significant danger among diseases including pond fish dactylogyrosis. Dactylogyrosis are monogenetic suckers, parasites with a direct development cycle, live on the fish gill filaments, belong to conditionally pathogenic parasites and pose a serious danger to young fish. Despite a fairly complete study of the biology of carp dactylogyrid, a number of questions regarding the formation of the parasitofauna of these young fish in the early stages of development - the most vulnerable period of their lives - remain little covered in the literature. The work presents data on the Dactylogyrus types found in young carp in the nursery ponds of the Orenburg region, the invasion extensiveness and intensity. 4 species of monogenetic suckers have been found: Dactylogyrus vastator, Dactylogyrus extensus, Dactylogyrus achmerowi, Dactylogyrus anchoratus. Among the four species of Dactylogyrosis, only two species, Dactylogyrus vastator and Dactylogyrus extensus, were found most often and from an early age, two other species were found in older fish, 20 and 25 days of age with little invasion extensiveness and intensity.

Histopathological alterations in the gills of banded gourami (Trichogaster fasciata) exposed to thiamethoxam

Thiamethoxam (THM) is a widely used agro-pesticide in Bangladesh, though European Union has banned this neonicotinoid insecticide due to its toxic effects on non-target organisms. A 60-day experiment was conducted to study the effect of sub-lethal concentrations of THM on gills of Banded Gourami Trichogaster fasciata. The experiment was conducted in 15 PVC tanks each containing 100L water. The 96-h LC50 value of THM was estimated as 161.06mg/L for Banded Gourami. Based on estimated 96-h LC50 value, the experiment was carried out using a control (0 mg/L of THM) and five sub-lethal concentrations (9.37, 18.75, 37.5, 75 and 150 mg/L of THM in water) with three replications. For collection of gills, fishes were sampled on day-30 and day-60 of exposure to THM. Several histopathological changes were observed in the gill tissues of treated fishes viz. clubbing and reduction of gill filaments, telangiectasis of gill lamellae, haemorrhage and damage of gill raker. Water quality parameters (e.g. DO, pH and temperature) were recorded every 15 days interval. The DO levels were found to decrease significantly with increasing THM concentrations and time of exposure, whereas no noticeable changes were observed for pH and temperature. Therefore, neonicotinoid crop insecticide like THM is capable of damaging gill tissues of an small indigenous fish Banded Gourami.

Acute Toxicity of Hexavalent Chromium on Behavioural Parameters and Histopathology Damages in Freshwater Common Carp, Cyprinus carpio

Water sources of almost all regions in India are carrying the unbearable burden of dangerous pollutants. The release of waste products and anthropogenic wastes run-off has contributed to aquatic pollution. The environment has become a storehouse for chemical pollutant which infiltrate into the aquatic environment, including estuarine, thus immobilizing the aquatic biota, among the heavy metals. Chromium is a heavy metal which has both beneficial and harmful effect on organisms. It is highly toxic and carcinogenic. Many industries are disposing of chemical pollutants to the water. These disposals contain many chemicals, including Chromium. The purpose of this review was to check the accumulation and concentration of heavy metals in different organs of freshwater fishes that come in contact with the water contaminated with heavy metals. The subjected fish were exposed to Chromium (Cr) at the sub-lethal level at a concentration of 40mg/L in 96 hours. During the observation period, the fishes shown some behavioral changes like erratic swimming, slow motility, suffocation, and the scales become thin and decolorized. In the gill region, the gill filaments become swollen, and gill rackers become thick, and curling of lamellae was noticed, and it is caused due to the Chromium build-upon gills. At the region of the caudal fin, permanent bending of the tail was observed. The Chromium also affects other vital organs like the spleen and gut region. LC50 was found in 96 hours. The result indicates that Chromium is highly toxic and has deleterious effects on aquatic life. Humans are also affected by the intake of fishes for primary people of those areas where the leading food is fish.