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Green terror (Andinoacara rivulatus) is one of the most popular freshwater ornamental fish of the Cichlidae, which is commonly bred and cultivated in Iran. The aim of this study was to investigate the main cause of green terror mass losses in an ornamental fish breeding center in Nazarabad, Alborz province. Following chronic and continuous losses of mature green terrors with clinical signs including white feces hanging from the anus, the fish were sampled between June 2021 and July 2021. The fish were packed in water-filled polyethylene bags and transported to the Ornamental Fish Clinic, Faculty of Veterinary Medicine, University of Tehran. In macroscopic examinations, cachexia and paleness of the fish were evident. In order to investigate ectoparasitic infestations, wet smears were prepared from skin and gills, and examined under a light microscope. However, no parasitic infection was observed. In addition, the fish were euthanised, necropsied, and internal organs such as the intestine were examined. Microscopic examination of the intestine showed a heavy infection with mature Capillaria sp. and the barrel-shaped eggs. In the present study, the severity of Capillaria infection was very high and determined to be the main cause of losses. In order to treat the other fish in the population, levamisole was administered for 48 h every 7 days for 28 days. After re-examination, fish losses completely stopped, and no infection was observed after 28 days.

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A female albino pindani (Chindongo socolofi) and female cobalt‐zebra (Maylandia callainos) were referred to the Ornamental Fish Clinic with a soft tissue mass on their upper jaw. Also, during clinical examination, an unencapsulated intraoral soft tissue mass was observed in the cobalt‐zebra cichlid. Digital radiography showed soft tissue masses and osteolytic lesions. Computed tomography (CT) imaging confirmed that osteolytic lesions occurred in skull bones of cobalt‐zebra. Also, soft tissue mass invaded to the intraoral space. Histopathologically, a non‐encapsulated, multilobulated and densely cellular neoplastic mass was identified. Extensive infiltration of neoplastic cells to the dermis and subcutaneous tissue was observed in both cases. The masses were composed of multiple coalescing nests, sheets, lobules and trabeculae of neoplastic cells within a fibrovascular stroma. The palisading basaloid neoplastic cells were markedly extended from the basal cells of the epidermis into the dermis and subcutis. The majority of the neoplastic cells had scant amounts of eosinophilic cytoplasm with indistinct margins, round to ovoid nuclei and typically a single small basophilic nucleolus. There was invasion of basaloid neoplastic cells into the bone tissue that caused osteolytic lesions. Mitotic figures were three to seven per high‐power field. Epidermal basement membrane was periodic acid‐Schiff (PAS) positive and neoplastic cell extension into the dermis was identified by the PAS staining. Fibrovascular stroma of the mass was also stained blue with Masson's trichrome. Based on histopathological and histochemical findings, the masses were diagnosed as infiltrative type of basal cell carcinoma (BCC).

Background: : Parasitic infestations are one of the most significant problems in global aquaculture. In addition to direct economic losses due to significant mortalities, parasites may have a significant negative impact on the fish's behaviour, energetic demands, trophic position, interspecific competition, growth rate, and reproductive function.Objectives: : We conducted the present study to evaluate the infection status of parasitic pathogens in freshwater sutchi catfish (Pangasianodon hypophthalmus) and silver dollar (Metynnis hypsauchen) farmed in Alborz province of Iran.Methods: : Between January and February 2021, 140 ornamental fish, including 70 sutchi catfish (P. hypophthalmus) and 70 silver dollar (M. hypsauchen), were delivered from various ornamental fish farms for parasitological analysis. Thorough macroscopic and microscopic examinations were performed to detect parasitic infections in delivered freshwater ornamental fish.Results: : A total of six parasite species, including five protozoan species (Nyctotherus piscicola, Trichodina heterodentata, Ichthyophthirius multifiliis, Protoopalina sp., and Hexamita sp.) and one monogenean species (Ancyrocephalus sp.), were identified in the examined fish. The overall prevalence of the recovered parasites was 46.43% (65/140) of the fish.Conclusions: : In the current study, several parasites, including Hexamita sp., Ancyrocephalus sp., Protoopalina sp., and N. piscicola, were identified as the first records of the sutchi catfish (P. hypophthalmus) and/or silver dollar (M. hypsauchen), and these two fish species are known as new hosts for the isolated parasites in ornamental fish farms in Iran. Assessing the parasitic fauna of ornamental fish is therefore critical for preventing parasite introduction into adjacent provinces as well as neighbouring countries and promoting fish health.