Morphological development and allometric growth of laboratory reared Nannacara anomala were studied from hatching to the loss of larval characters and beginning of squamation (18 days post-hatching) at 26°C. The mean total length (TL) of larvae and juveniles increased from 3.74 mm at hatching to 9.60 mm at metamorphosis. Morphogenesis and differentiation were most intense during the first week of development. During this period (TL interval = 3.74 -4.84 mm) there was an evident priority to enhance the feeding and swimming capabilities by promoting accelerated growth in the head and tail regions. Following this period, there was a major decrease in growth coefficients, indicating a change in growth priorities. Observations on the early development of Nannacara anomala confirmed the basic uniformity development of a substrate brooding cichlid.Se realizó el estudio del desarrollo morfológico y crecimiento alométrico de Nannacara anomala criada en el laboratorio en la temperatura de 26°C, entre la eclosión y la pérdida de todas las características de larva y el principio del proceso de escamación (a los 18 días de la eclosión). La total logitud media (TL) de larvas aumentó de 3,74 mm en eclosión a 9,60 mm en el momento de metamorfosis. La morfogénesis y la diferenciación fueron más intensos durante la primera semana del desarrollo. En este periodo (el intervalo TL= 3,74 -4,84) se observó una gran prioridad en la mejora de habilidades de encontrar alimento y nadar al promover el crecimiento de la zona de la cabeza y la cola. Transcurrido este periodo se notó una importante bajada de los coeficientes del crecimiento lo que indica el cambio de prioridades de crecimiento de distintas partes del cuerpo. Las observaciones del desarrollo temprano de Nannacara anomala confirman las similitudes principales en el desarrollo de cíclidos criados en sustratos.

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Abstract. The aim of the study was to determine the impact the commercial supplement S.presso (INVE Aquaculture, Belgium), a source of polyunsaturated fatty acids to enrich the proximate composition of brine shrimp (Artemia sp.), had on their growth and mortality. Four different enrichment protocols were investigated: the supplement was given in one or two doses at various time intervals. The results indicate that while S.presso increased nauplius mortality slightly, administering the appropriate dose reduced losses to a very low level (from 12.5% with a single dose to 8.6% with the recommended dose divided into to equal parts). Additionally, it was confirmed that the supplement S.presso increased brine shrimp growth slightly in comparison to that of the control group, but the differences were statistically insignificant. The results permit concluding that S.presso is suitable for use as a source of polyunsaturated fatty acids for brine shrimp enrichment with the intent of using them as fish food.

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The aim of this study was to compare the physiology and morphology of the digestive tract of Russian sturgeon (Acipenser gueldenstaedtii) larvae fed Artemia sp. nauplii enriched or non-enriched with essential fatty acids (EFA). Physiology was evaluated by digestive enzyme activity analysis, while morphology was assessed with histological methods. The larvae were divided into two groups, in which fish were fed either pure Artemia sp. nauplii or Artemia enriched in EFA. Both groups had similar survival rates, but fish fed EFA-enriched Artemia displayed higher, body weight and length. At the end of the experiment (22 dph): 1) the activities of lipase and leucine aminopeptidase were similar in both groups; 2) the activities of trypsin, alkaline phosphatase and γ-glutamyltransferase were insignificantly higher in fish fed pure Artemia; 3) the activity of α-amylase was significantly higher in the EFA-enriched feeding group; 4) lower hepatocyte lipid vacuole diameters and hepatocyte proliferation were measured in the EFA-enriched group. Lipid accumulation was observed in the anterior intestine of fish fed pure Artemia on the 15 th and 22 nd dph. The epithelial turnover was significantly lower in the EFAenriched group, in the posterior intestine on the 15 th dph, but no differences occurred between the groups on the 22 nd dph, in either anterior or posterior intestine. In conclusion, the study revealed a positive effect of the EFA-enriched Artemia-based diet on the physiology and morphology of the digestive system of Russian sturgeon larvae.