Diseases of aquatic organisms最新文献

Coral diseases are an increasing threat to continuously degrading reefs as disease abundance and virulence are expected to increase in the future. Active conservation measures, specifically coral restoration projects, are increasingly being implemented worldwide. Yet little is known about the implications of disease occurrence in a restoration context. This study describes white syndrome pathogenesis in 2 coral genera, farmed in 2 mid-water rope nurseries located in a reef and a lagoon habitat in the Maldives. Over a 112 d monitoring period, disease metrics were obtained from 336 Pocillopora and 96 Acropora fragments to assess the impacts of unmitigated disease progression in coral nurseries. Disease had low prevalence (2.2%) and incidence (0.007) in reef-farmed Pocillopora, but survival (91%) was significantly reduced in comparison with the unaffected lagoon-farmed Pocillopora (99%). In contrast, lagoon-farmed Acropora showed high disease prevalence (78.5%) and incidence (0.064), and a lower survival (79%) than disease-unaffected reef-farmed Acropora (98%). These findings had distinct implications for coral gardening success. While Pocillopora was considered suitable for outplanting, especially since subsequent mitigation interventions were successful, the diseased, lagoon-reared Acropora posed a potential risk to the restoration site and was unsuitable for outplanting following 1 yr of farming effort. Our findings demonstrate that unmitigated diseases can cause major setbacks to restoration success. Coral gardening projects are likely to be particularly susceptible; therefore, disease monitoring and risk management are imperative. Since there is currently a lack of available diagnostic and mitigative tools, this study aims to provide case study data for restoration practitioners.

Significant knowledge gaps remain in our understanding of the reproductive physiology and diseases of elasmobranchs. The objective of this work is to describe the clinical, imaging, and pathologic findings associated with polycystic ovaries in cownose rays housed in public aquariums. Ten adult female cownose rays Rhinoptera bonasus housed in 4 public aquariums presented with variable nonspecific (lethargy, anorexia, cutaneous discoloration) or no clinical signs. Clinical antemortem examination revealed a large, heterogeneously hyperechoic mass with many variably sized and shaped anechoic cavitations within the coelom on ultrasound in 2 animals. Necropsies of 10 animals revealed polycystic, fluid-filled ovarian masses filling approximately 65-75% of the coelomic cavity in severe cases along with substantial liver atrophy. Microscopically, the masses were composed of delicate connective tissue supporting a combination of cysts lined by attenuated squamous to foamy columnar epithelium, hemorrhage, embedded anovulatory follicles, and oocytes along the periphery. Polycystic ovarian disease is understudied in elasmobranchs and presumptively resulted from failure of follicular ovulation in these cases. Along with southern stingrays, cownose rays appear to be at heightened risk for developing polycystic ovaries under human care. Further study into disease prevalence, epidemiologic factors, etiopathogenesis, and treatment modalities are needed in order to prevent and medically manage this condition in cownose rays under human care.

The bopyrid Pseudione galacanthae is an ectoparasite of the squat lobster Grimothea gregaria (Munida gregaria). This study aimed to analyze the spatial variations in the prevalence of P. galacanthae in Argentine Patagonia and the potential drivers shaping this variability. To analyze this crustacean/crustacean parasitic relationship, bottom trawl net hauls, a CTD cast, and zooplankton samplings were performed in 10 locations between 43.6° and 47.7°S. Squat lobsters were assigned to 1 of 2 morphotypes (gregaria or subrugosa), sexed, and measured, and the branchial chambers were examined in search of bopyrids. Correlation analyses were performed to identify whether environmental variables (sea bottom salinity, SBS), sea bottom temperature, depth, and calanoid copepods abundance) or population traits (median of size distribution and density of squat lobsters) were related to P. galacanthae prevalence. The gregaria morphotype was dominant in the south of San Jorge Gulf (SJG), whereas the subrugosa morphotype was more abundant in the other locations. No significant differences were observed in P. galacanthae prevalence between sexes or morphotypes. Spatial variations in prevalence were observed, reaching 15.2% in the south of SJG. P. galacanthae prevalence was correlated only with SBS. We hypothesized that the highest prevalence of P. galacanthae could be related to the presence of a tidal frontal system in the south of SJG, which could favor parasite larval retention. The prevalence reported here is the highest for bopyrid parasites in squat lobster species and reveals that this interaction could have a detrimental impact on G. gregaria populations at local scale.

Piscinoodinium is a well-known parasitic dinoflagellate genus that causes epizootics in tropical freshwater fish. This study investigated the first outbreak of Piscinoodinium sp. in freshwater fish of the Andaman Islands, India. The infection was noticed in the non-native fish Betta splendens and Poecilia reticulata, and in the endemic killifish Aplocheilus andamanicus. The infection caused mass mortality in larval, sub-adult, and adult fish. The parasite was identified based on microscopy and molecular characterization. The prevalence, parasite density, and mortality percentage were recorded. Infected fish had numerous trophonts attached on the body surface, gills, fins, and eyes. Infected skin and gills showed degeneration of the epithelial cells and clubbed gills. Small subunit rDNA (955 bp) was amplified from the Piscinoodinium sp. infecting B. splendens, revealing genetic differences between it and Piscinoodinium spp. from the USA and from India.

We studied the population and reproductive characteristics of the stone crab Hapalogaster dentata (De Haan, 1849) (Anomura: Lithodidae) parasitized by Briarosaccus hoegi (Rhizocephala: Peltogastridae) from Peter the Great Bay (northwestern Sea of Japan) in 2023. The sex structure of the H. dentata population was female-biased and represented by 39.1% males and 60.9% females. The size-frequency distribution differed between males and females. The prevalence of parasitization of H. dentata by B. hoegi reached 6.7%. No relationship between crab sex and parasitization prevalence was found. Most of the parasitized specimens (94.8%) had only a single parasitic externa. The non-parasitized and parasitized crabs did not differ in main carapace length. The pleopods in most of the externa-bearing females were shortened or completely atrophied. H. dentata produced 1 clutch per year with ovigerous females occurring from October to May. An obvious delay in embryonic development was observed in winter. None of the parasitized H. dentata females were ovigerous. Externae with embryos of B. hoegi were found from May to July.

Physiological mechanisms underlying relationships between the trematode parthenitae and their molluscan hosts are poorly understood. In this study, we estimated the cardiac function of gastropods Littorina littorea L. infected with Himasthla elongata and Cryptocotyle lingua under laboratory conditions and in situ. The heart rate (HR) of the infected periwinkles was significantly lower than in the uninfected ones. HR of uninfected periwinkles in the natural environment followed a clear tidal pattern, with high values at high tide and low values at low tide. However, HR in most of the infected molluscs did not follow this rhythm. The decrease in HR was more pronounced in the periwinkles infected with C. lingua than with H. elongata. Thus, infection with C. lingua had a greater effect on the physiology and metabolic rate of periwinkles than infection with H. elongata.

Acute hepatopancreatic necrosis disease (AHPND) is a devastating shrimp disease caused by a binary toxin, PirAB, produced by Vibrio parahaemolyticus and other closely related bacteria. To address AHPND, over 300 unique single-domain antibodies (also known as nanobodies) derived from the VHH domains of Lama glama heavy-chain-only antibodies were raised against either PirA or PirB and characterized. Nanobodies were shortlisted based on their affinities for either PirA or PirB, their relative stability in intestinal fluids, and their ability to reduce PirAB-induced death in brine shrimp Artemia salina. From these data, a subset of nanobodies was tested for their ability to reduce AHPND in whiteleg shrimp Penaeus vannamei, and nanobodies targeting either PirA or PirB provided significant disease protection to whiteleg shrimp. These results show that nanobodies can be a new option for shrimp farmers to reduce or eliminate the impact of AHPND on their operations.

The ectoparasite Amyloodinium ocellatum is a dinoflagellate that causes severe morbidity and mortality in both brackish and marine warmwater aquaculture fishes worldwide. A. ocellatum has a triphasic life cycle based on a free-living flagellate (the dinospore), a parasitic stage (the trophont) and a resting and reproductive cyst (the tomont). Current chemical treatments have shown some efficacy in eliminating dinospores but fail to inactivate the tomonts. Here we evaluated the efficacy of alternative treatments in vitro through sporulation tests and the quantification of dinospore production and motility. Hydrogen peroxide and peracetic acid efficiently decreased dinospore production at low concentrations, but total inactivation of tomonts was only achieved with higher dosages. Tomont inactivation was also observed with disinfectants such as sodium hypochlorite and Virkon S. This work provides insights into effective and environmentally friendly alternatives for the elimination of resistant forms of the marine parasite A. ocellatum.

An evaluation of morbidity and mortality in Steller sea lions (SSLs) Eumetopias jubatus under professional care identified a high prevalence of thyroid disease in aged animals. While studies have investigated the effects of age, season, nutrition, stressors, and pollutants on thyroid hormones in pinnipeds, data from individuals with known thyroid disease are lacking. Histopathological reports of adult SSLs in North American aquariums from 1979 to 2022 with banked serum (n = 14) were reviewed. Radioimmunoassays, which have been validated in this species, were used to determine triiodothyronine (TT3), total thyroxine (TT4), and free thyroxine (fT4). A solid-phase chemiluminescent immunometric assay for thyroid-stimulating hormone (TSH) quantification was validated by testing inter- and intra-assay repeatability, recovery, and parallelism. Lesions included follicular cysts (n = 5), adenoma with thyroglossal duct or follicular cysts (n = 2), medullary or follicular C-cell carcinoma with follicular cysts and nodular hyperplasia (n = 1), neuroendocrine carcinoma with follicular cysts (n = 1), and sarcomatoid carcinoma metastasis to the thyroid (n = 1). Significantly lower concentrations of TT3, TT4, and fT4 in SSLs with thyroid disease (n = 10) versus those without (n = 4) were attributed to space-occupying lesions, advanced age, and/or season. TSH was not significantly different between groups. Fifty percent of diseased SSL profiles were within reference ranges, and all individuals with lesions were clinically euthyroid. These data expand the current understanding of thyroid disease in SSLs and underscore the need for additional diagnostics (e.g. cervical ultrasound) concurrently with hormone assays to effectively screen for underlying abnormalities.

Septic arthritis is a frustrating disease in sea turtle rehabilitation because of its unclear pathogenesis, delayed onset during rehabilitation, long-term treatment requirements, and potentially poor prognosis. Radiography, blood cultures, and arthrocentesis have been used as diagnostic tools for suspected cases. However, there is currently a lack of data on the characteristics of synovial fluid in healthy sea turtles. To establish reference data for synovial fluid in sea turtles, we enrolled 14 green turtles Chelonia mydas rescued between 2019 and 2022 from 3 facilities using the following inclusion criteria: normal attitude and appetite, normal motor functions of the 4 limbs, no joint swelling, and no ongoing use of antibiotics for at least 1 mo. Bacterial cultures of blood and synovial fluid from the shoulder joints of these turtles were obtained and a qualitative analysis of the synovial fluid was performed. The results revealed bacterial culture-negative blood and synovial fluids at 37°C. Most characteristics of normal synovial fluid in green turtles, such as being transparent, colorless, and able to create a strand of over 2.5 cm by being pulled with a needle in viscosity trials, as well as the cytology of the normal synovial fluids being dominated by histiocytes and synovial lining cells, lymphocytes, and occasionally a few heterophils or erythrocytes were similar to those in mammals. This study provides information on the normal synovial fluid characteristics of green turtles in Taiwan, which may be beneficial for the diagnosis of joint diseases in sea turtles.