This research aimed to evaluate the effect of biofloc technology on the intestinal morphometry, productive performance, and survival of juvenile Mugil cephalus. An 87-day investigation was conducted with two treatments, each with three replicates. Treatment one involved rearing juvenile M. cephalus in a biofloc system with a C/N ratio of 15:1, and treatment two involved rearing juvenile M. cephalus with a water exchange and no carbon addition. Ninety (90) juveniles of Mugil cephalus with an average weight of 117.36 ± 6.48 g were randomly distributed into six (6) circular plastic tanks of 250 L (fifteen fish per tank). At the end of the experiment, 10% of each experimental unit’s population was sacrificed for intestinal morphometry analysis. The productive performance was evaluated every 30 days by randomly sampling fish from each tank for biometric measurements, including the specific growth rate (SGR), feed conversion ratio (FCR), condition factor (K), and survival. No structural changes were observed in the intestinal mucosa. The fish reared in biofloc exhibited a similar gut morphometry (villus length and villus thickness) compared to the fish in the water exchange system. The biofloc system does not compromise the gut health of mullet. No significant differences (p > 0.05) were observed in the final weight, weight gain (WG), daily weight gain (DWG), specific growth rate (SGR), condition factor (K), and survival between the treatments evaluated. M. cephalus can be reared using biofloc technology, demonstrating significant water savings compared to water exchange systems.

Aquaculture is a globally relevant sector in terms of production and income. When we think about shrimp farming, Penaeus vannamei, the Pacific white shrimp, has been instrumental in this growth due to its characteristics and advances in production. Despite achievements, it faces significant economic challenges due to the white spot syndrome virus (WSSV), causing considerable losses. This virus has led to significant economic losses, affecting economies such as Ecuador's. The clinical signs of WSSV require rigorous diagnostic procedures, combining histopathological examination and PCR assays. A retrospective study of 900 specimens of Penaeus vannamei in Ecuador highlights the correlation between tissue pathology and mortality rates, enhancing understanding of the direct impact of the disease. Histopathological analysis reveals distinctive intracellular viral inclusions, reflecting disease progression. Although PCR assays provide definitive diagnoses, histopathological evaluation enriches understanding of lesion severity, supporting a comprehensive approach to disease management strategies.

The production of ornamental fish has increased in recent years. The zebrafish (Danio rerio) is a popular model organism used in scientific research across various fields. Hypoxia, or a reduction in the level of dissolved oxygen in water, is a critical condition that directly affects the survival and maintenance of many aquatic organisms, including fish. In this case report, we describe a zebrafish that experienced hypovolemic shock resulting from hypoxia caused by a sudden drop in dissolved oxygen levels. This case study describes a bioterium in which a power outage caused a drop in dissolved oxygen levels, resulting in a high mortality rate. Histopathology was used to evaluate the tissues, which were fixed in 10% formalin, processed in an automatic processor and embedded in paraplast. Tissue blocks were sectioned at a thickness of 3 µm and stained in haematoxylin and eosin for observation. Microscopically, the myocardium appeared slightly hypertrophic and the pericardium showed dense haemorrhages. The kidney tubular cells showed pronounced oedema with a whitish, foamy cytoplasm. Some tubular cells showed pronounced eosinophilia and necrotic cells were observed detaching from the tubular basement membrane in some tubules. The brain parenchyma showed pericellular oedema, increased Virchow-Robin spaces and mild glial proliferation. Therefore, we conclude that the underlying cause of death was a decrease in environmental oxygen levels combined with pre-existing branchial lesions, which generated hypoxia resulting in cardiac failure due to diffuse haemorrhages.

Hippocampus reidi is an endangered tropical species, as well as being one of the most widely traded marine fish globally. The cellular organization of the normal liver in the longsnout seahorse (H. reidi) was studied using electron microscopy to provide an overview of the liver’s fine structure. Two hundred and fifty seahorses were collected and prepared for transmission electron microscopy. Sections were cut using an LKB ultramicrotome and then washed with PBS, stained with uranyl citrate for 2-3 min, and then with lead acetate for 20 s. The grids were then observed using an electron microscope Zeiss EM 109. The cytoplasm of the hepatocyte contains a nucleus surrounded by a double membrane, diffusely scattered mitochondria and a network of the endoplasmic reticulum of rough and smooth types. Most of the rough endoplasmic reticulum appear to be in parallel to the nuclear envelope or the cell membrane and was situated relatively in the center part of the cytoplasm. The cellular organization of the longsnout seahorse liver is quite similar to that of other mammalian species.

This study evaluated the immunomodulatory and histological effects of dietary supplementation with an ethanol extract of Limnospira platensis (spirulina) in Penaeus vannamei. Shrimp were fed diets supplemented with 0.5%, 1%, 2%, and 4% spirulina extract for 35 days. Growth performance did not differ significantly among treatments, suggesting no adverse effects on nutrient utilization. However, immune parameters, including granulocyte abundance and hemocyte phagocytic capacity, improved significantly at 0.5–2% inclusion levels, with 0.5% promoting the highest granulocyte counts and 2% maximizing phagocytic activity. In contrast, the 4% treatment led to a decline in both granulocyte levels and phagocytosis, indicating saturation effects at higher doses. Histological analyses supported these findings, as villus length improved with 0.5, 1 and 2% doses but not with 4%. Overall, these results confirm a non-linear immunostimulatory response of L. platensis extract, highlighting low inclusion levels, especially 0.5%, as effective and economically feasible strategies to strengthen shrimp immunity in intensive aquaculture.

In this work, we describe lesions produced by the dinoflagellate protozoan Amyloodinium ocellatum on the gills of Mugil liza, which causes the velvet disease in several fish species. These parasites produce severe lesions in the gills, with hyperplasia of primary and secondary gill lamellae rupture of pillar cells, and hyperplasia of chloride cells (ionocytes). The gill structure is totally affected, which presumably impairs normal hematosis and electrolyte regulation and seriously compromises the fish's health. The lesions caused by A. ocellatum are responsible for high mortality rates in fish farms and economic losses in the industry. In the present study, we found cellular hyperplasia of the respiratory epithelium, epithelial disruption, the collapse of secondary lamellae, and various degenerative changes that seriously compromise the gill functioning.