Draining system and feeding rate during the initial development of Lophiosilurus alexandri (Steindachner, 1877), a carnivorous freshwater fish

This study evaluated the efficiency of the drainage system during the larviculture of Lophiosilurus alexandri. Moreover, we assessed the best feeding rate after feed training for juvenile production. The study was performed in three phases over 87 days. In phase 1 (40 days), larvae were fed live food and posteriorly submitted to feed training in two drainage systems: water drained on the surface (DS), and water drained into a tank column (DI). In the second phase (30 days), using only the DS system juveniles were fed a formulated diet at feeding rates, 2, 4, 6 and 8% of body wet weight. In the third phase (17 days), the fish from the second phase were fed until apparent satiation. At the first phase, the animals in the DS system exhibited greater survival rates and growth. The best feeding rate for daily weight gain, specific growth rate (SGR) and mean body weights were similar: 5.57, 5.13 and 5.68% respectively. In the third phase, an increased SGR was observed in the treatment groups that received lower feeding rates in the second phase (2 and 4%), which could indicate a possible compensatory growth rate.     

Effects of Dietary Lipid Levels on Growth,Survival, and Molting of Yearling Narrow Clawed Crayfish,Astacus leptodactylus

The influence of dietary lipid level was evaluated on growth, survival, and molting of yearling narrow clawed crayfish, Astacus leptodactylus. Yearling crayfish were fed five isonitrogenous diets (35% protein), formulated to contain 4%, 7%, 10%, 13%, or 16% lipid. Crayfish (10.1 ± 1.6 g) were reared for 56 days in 60-L fiberglass tanks at 23 ± 1.7 °C, with flow-through water and continuous aeration. At the end of the trial, crayfish fed 13% lipid had the highest weight gain and specific growth rate, significantly different from crayfish fed 4% and 7% lipid (p < 0.05). Crayfish fed 13% lipid had a significantly higher survival rate (86.7%) than the animals fed 4% lipid (71%) (p < 0.05). Molting was not affected by lipid level (p > 0.05). We recommend 13% dietary lipid level for optimum growth and survival of Astacus leptodactylus in intensive cultivation.     

Bilateral patellar agenesis in dog: A case report

A bilateral patellar agenesis is an extremely rare congenital condition in which the patient does not develop both patellas and can present secondary alterations as bone, muscle and postural changes. There are some hypotheses that it has a genetic background presenting dominant characteristic. It is not yet standardized a gold treatment for this affection, but according to rare reports, clinical and surgical treatments are possible. This is a case report based on imagining exams of a mix breed male puppy that was born with bilateral patellar agenesis, an affection not yet reported in canine species.     

Temporal changes in the fish community structure of a small subtropical spring lake: Decadal and seasonal analysis

In spring lakes, which have homogeneous environmental characteristics, it is expected that there will be no significant changes in the composition and structure of communities over time, and fluctuations will generally be related to the ecological attributes of the species. We studied the fish community in a small subtropical spring lake, Lake Zacapu, for two different decades to analyse its structural characteristics. Sampling was performed every 3 months at four sites from January to October 1995 and from May 2019 to May 2020. We determined the temporal variation (seasonal and decadal) in the fish community structure with respect to composition, abundance, diversity and dominance. We evaluated the association between species and water quality. Our results showed spatial homogeneity in most physicochemical variables that remained in the same range across decades, although some nutrients (NO₃) recently increased. All species identified in the early samples were present in the recent surveys (eleven native and two nonnative species), indicating that the fish community composition had significant qualitative stability. However, the dominant littoral cyprinid in 1995 was replaced by the more limnetic atherinopsid in 2019–2020, and the diversity and abundance of sensitive fish decreased in recent samplings. Consequently, the current status of critically endangered species is supported for some restricted and microendemic fish. The changes in the community structure attributes, which show a tendency for reduction in native species, emphasise the need to implement efforts to conserve freshwater fish diversity in small spring lakes.