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A B S T R A C TEggs of 20 females were sampled to analyze lipid, protein, and carbohydrate content during the embryonic development of Cherax quadricarinatus. Sampling was performed on recently spawned eggs to first juvenile stage. Ten eggs were sampled every 48 h during the first two weeks and every 72 h thereafter for biochemical analysis. Total proteins, lipids, and carbohydrates were measured. Proteins were the most abundant egg component (63.2%), followed by lipids (32.3%), and carbohydrates (4.4%). A steady decrease of lipid content was observed ( y 5 895.38 2 9.93x, r 2 5 0.94; y 5 lipid concentration, x 5 days). For proteins, two different depletion rates were observed, with the initial rate maintained for 30 days ( y 1 5 1,443.0 2 4.46x 1 , r 2 5 0.90) and an increased depletion rate after hatching ( y 2 5 1,936.60 2 21.10x 2 , r 2 5 0.96). Carbohydrates were always present as a minor constituent, and its concentration did not change significantly. Water content increased from 52% in recently spawned egg to 85% in juveniles. Energy equivalents were calculated from each component, and the overall energy expenditure is represented by the equation y 5 13.86 2 0.11x (r 2 5 0.95). Relevant morphological features for each sample day are indicated.

RESUMEN.Los langostinos del género Macrobrachium con interés económico y pesquero son bien conocidos y explotados en casi todas las comunidades ribereñas de Latinoamérica. Sin embargo no han sido estudiados apropiadamente, y su conservación está en riesgo. Las características económicas, sociales y culturales, de la mayoría de los países de la región, que se traducen en el deterioro del hábitat y la sobreexplotación pesquera, ponen en peligro de desaparición las poblaciones de este género de macroinvertebrados acuáticos. De esto, se desprende que todas estas especies están escasamente estudiadas y el estado actual de sus poblaciones no es conocido, si bien en el caso de M. amazonicum hay numerosos estudios. Las técnicas de cultivo es el rubro en que más investigación se ha realizado. En este trabajo se resume el conocimiento que se tiene sobre las especies nativas de Macrobrachium en Latinoamérica y se discute su importancia económica y necesidades de conservación.

ABSTRACT. The cauque river prawn Macrobrachium americanum occurs along the Pacific coast of America. This prawn can grow to a large size, making it an interesting option for aquaculture production. Currently, supplies of juveniles are limited because hatchery and laboratory-reared larvae are difficult to raise. This study assesses larval survival for different combinations of stocking density and feeding from larvae cultivated in green water. From these combinations, larvae fed with Artemia nauplii and maintained at a density of 50 larvae L -1 had the highest survival.Keywords: Macrobrachium americanum, larval development, feeding, survival, prawn.Cultivo experimental de larvas de langostino Macrobrachium americanum (Bate, 1868), con énfasis en alimentación y efecto de la densidad sobre la supervivencia RESUMEN. El langostino de río Macrobrachium americanum, ocurre a lo largo de la costa Pacífica de América. Este langostino puede alcanzar grandes tallas lo que lo convierte en una opción interesante para la acuicultura. En la actualidad, el abastecimiento de juveniles a partir del cultivo de sus larvas en hatchery y en laboratorio son difíciles de criar. Este estudio evalúa la supervivencia de las larvas con diferentes combinaciones de alimento y densidades de población cultivadas en agua verde. A partir de estas combinaciones, las larvas alimentadas con nauplios de Artemia salina, mantenidas a una densidad de 50 larvas L -1 , tuvieron la mayor supervivencia.Palabras clave: Macrobrachium americanum, desarrollo larvario, alimentación, supervivencia, langostino.

We determined the effect of four concentrations of dietary crude protein, 30.7, 37.2, 41.8 and 46.8% on growth rate, survival and body composition of the juvenile cauque river prawn (Macrobrachium americanum). The prawns were hatched in the laboratory from the spawn of one wild ovigerous female. Prawns consuming 37.2% crude protein reached a final weight of 0.58 g (feed conversion ratio of 2.15), which was significantly better than the other treatments. Survival was 100% in all treatments. Protein content in the diets had no significant effect on whole body proximate composition and amino acid profile. Juveniles consuming the 37.2% crude protein diet grew faster than those fed the other diets. Specific growth rate was adjusted to the two-slope broken-line regression analysis model to estimate the optimal protein requirement. In conclusion, these results demonstrated that the 37.2% protein level diet is optimal for juvenile cauque river prawn M. americanum in the experimental conditions of this study.

The embryonic changes during the development of the freshwater prawn, Macrobrachium americanum are described from observations made on live embryos based on the percentage-staging method. Eggs were observed with a stereomicroscope to obtain descriptions of embryonic periods. This prawn has an incubation time of 18 days at 24 • C. Ten periods are described and illustrated. A comparison of this developmental process with those of congeneric species is included. RESUMEN Se describen los caracteres externos del desarrollo embrionario del langostino dulceacuícola Macrobrachium americanum tomando como criterio el método de estadios fijos basado en porcentajes. Los huevecillos fueron observados en vivo con un microscopio estereoscópico y se descibe cada periodo de desarrollo. Los huevecillos tardan 18 días en incubarse a una temperatura de 24 • C. Diez periodos se describen e ilustran. Se compara el desarrollo con el de algunas especies cercanas.

Consumer demand for aquatic animals has led to increased interest in using new species for aquaculture purposes. This study appraises the potential for aquaculture of the cauque prawn Macrobrachium americanum using wild juveniles from the west coast of Mexico. Four treatments were applied; treatments A and B consisted of 196 prawns/m2 and treatments C and D of 98 prawns/m2, with and without shelter, respectively. Growth and survival under these conditions were examined for 84 d. The combination of 98 prawns/m2 and shelter resulted in the best survival and growth, whereas the poorest performance was in the treatment with 196 prawns/m2 and no shelter.

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