ABSTRACT. Over recent years, Macrobrachium amazonicum has become a popular species for shrimp farming due to their fast growth, high survival rates, and marketability. Several studies have focused on the development of new technology for the culture of this species, but many aspects of their nutrition and physiology remain unknown. Thus, the goal of the present study was to obtain transcripts of putative genes encoding digestive enzymes, based on a library of the cDNA from the hepatopancreas of M. amazonicum, sequenced in the Ion Torrent TM platform. We identified fragments of nine genes related to digestive enzymes, acting over proteins, carbohydrates and lipids. Endo and exoproteases were also recorded in the hepatopancreas, indicating adaptation to the digestion of protein-rich foods. Nonetheless, the enzymes involved in the carbohydrate metabolism formed the largest functional group in M. amazonicum, including enzymes related to the digestion of starch, chitin, and cellulose. These findings indicate that the species has a genetic apparatus of a well-adapted omnivorous animal. This information may provide important insights for the selection of ingredients for the formulation of a more appropriate diet to the enzymatic repertoire of M. amazonicum.

ABSTRACT Effects of four feeding regimes on the development and feed intake, survival, productivity, and growth of Macrobrachium amazonicum larvae were investigated. Larvae were fed from stage II to IX, as follows: Artemia nauplii + inert diet during the entire larval cycle (AIn); Artemia nauplii for the entire larval cycle + inert diet from stage V onward (A/AIn); Artemia nauplii until stage IV + inert diet from stage IV onward (A/In); and only inert diet for the entire larval cycle (In). Each feeding regime (treatment) was carried out in three 50-L rectangular black tanks, set up in a recirculating system, filled with 10 salinity brackish water, and stocked at 81.8±0.8 larvae/L. The larval stage index, occurrence of Artemia nauplii and/or inert feed into the digestive tract, survival (number of larvae and postlarvae), productivity (number of postlarvae/L), and weight gain (mg) were evaluated. Larval development was similar in treatments AIn, A/Ain, and A/In, but was delayed in treatment In. Artemia nauplii were ingested by larvae irrespective of developmental stages, while inert feed was ingested only from stage III onward. Survival and productivity were higher in treatment AIn and decreased according to the number of days larvae were fed Artemia nauplii. Macrobrachium amazonicum larvae are omnivorous and polytrophic, but live feed is essential in the first stages and act as a complementary diet in the last half of larval cycle. There is a potential for inert diet to replace Artemia in the last phase of development if the nutrient composition matches larvae requirements. The combination of Artemia nauplii and inert diet during all larval cycles is the best management to maximize productivity.

ABSTRACT The Nile tilapia, Oreochromis niloticus (Linnaeus, 1758), uses filter feeding and visual predation to catch prey. In filter feeding, the mucus secreted in their gill rakers traps planktonic organisms. In visual predation, the fish spot and capture food, eating it directly. At different ontogenetic stages, the Nile tilapia may impact the zooplankton community differently, since it changes how it captures its prey. The objective in this study was to verify which zooplankton groups contribute to the diet of O. niloticus at the post-larval stage, and if the way they capture food may determine prey size. We evaluated the diet of Nile tilapia kept in ponds for four months. We randomly removed one fish per pond every month. Stomach contents and gills of fish were extracted, fixed in formaldehyde and then analyzed with an optical microscope and stereomicroscope with a micrometric ocular in order to measure the zooplankton and the gill rakers. Fish increased consumption of rotifers, and decreased the consumption of microcrustaceans considerably up to zero in the last month. The gill raker size, nevertheless, increased as tilapia grew. Therefore, negative correlations were found between raker size and size of ingested zooplankton, showing that the size of ingested prey decreases throughout this cichlid's life. Juveniles filter feed on rotifers, and actively prey on microcrustaceans. As adults, fish stop preying visually and the mucus secreted by the gill rakers trap only small individuals. Juvenile Nile tilapia filter feed and visually prey on zooplankton. However, when adults, filter-feeding plays a more important role in the way the zooplankton community is affected. The increase in the size of the Nile tilapia's gill raker does not determine the consumption of larger zooplankton prey, and the presence of mucus in these structures plays a major role for the capture of zooplankton during the cichlid's adult stage.

Diverse reproductive strategies may be adopted by different species of Macrobrachium prawns, and even among different populations of the same species. The present study evaluated the influence of differences in the reproductive strategies of two geographically isolated populations of Macrobachium amazonicum, upon female fecundity, reproductive output and the chemical content of prawns and eggs. One prawn population from Pará only completes its life cycle in brackish water, whereas another from Mato Grosso do Sul only inhabits freshwater. Pará female prawns exhibited a larger average size and weight and produced more eggs than females from Mato Grosso do Sul. However, the Mato Grosso do Sul population produced eggs that were larger in volume than those of females from the other population. Furthermore, eggs produced by Pará prawns were composed primarily of water (56%), whereas those produced in Mato Grosso do Sul were composed mostly of organic matter (80%). This difference in the eggs' chemical compositions did not apply to the chemical compositions of the females, as individuals from both sites were composed primarily of water. Mato Grosso do Sul females invested a higher amount of energy in brood formation (14% of their wet weight) than individuals from Pará (only 10%). It is possible that M. amazonicum populations show a higher degree of plasticity in their reproductive activity due to habitat conditions and genetic differences. Although the brackish population produces larger individuals, and exhibits higher fecundity, the freshwater population exhibited a higher reproductive investment. These results suggest a high reproductive capacity to adapt to different environmental conditions for this species, which should be considered in the context of aquaculture activities.

Diversas estrategias reproductivas pueden ser adoptadas por distintas especies de camarones del género Macrobrachium, e incluso entre diferentes poblaciones de la misma especie. En el presente estudio se evaluó la influencia de las diferencias en las estrategias reproductivas de dos poblaciones de Macrobachium amazonicum, geográficamente aisladas, sobre la fecundidad, rendimiento reproductivo y composición química de los camarones y sus huevos. Una población de camarones de agua dulce de Pará sólo completa su ciclo de vida en agua salobre mientras, que otra de Mato Grosso do Sul sólo habita en aguas dulces. Las hembras de la población de Pará presentaron, en promedio, mayores tamaños y mayor peso y producen más huevos que las hembras de Mato Grosso do Sul. Sin embargo, la población de Mato Grosso do Sul produjo huevos que eran más grandes en volumen que aquellos de las hembras de la otra población. Aún más, los huevos producidos por hembras de la población de Pará contenían mayor cantidad de agua (56%), mientras que aquellos producidos por las hembras de Mato Grosso do Sul se componen sobre todo de materia orgánica (80%). Esta diferencia en la composición química de los huevos no se aplicaba a la composición química de las hembras, ya que individuos de ambos sitios estaban compuestos principalmente de agua. Las hembras de Mato Grosso do Sul invirtieron una mayor cantidad de energía en la puesta (14% de peso húmedo) que las hembras de Pará (solo 10%). Es posible que las poblaciones de M. amazonicum muestren un mayor grado de plasticidad en su actividad reproductiva debido a las condiciones del medio y a diferencias genéticas. Aun cuando la población estuarina produce individuos más grandes y presenta mayor fecundidad, la población de agua dulce presenta una inversión reproductiva mayor. Estos resultados sugieren una alta capacidad reproductiva de adaptación a diferentes condiciones ambientales para esta especie, que debe ser considerada en el contexto de las actividades de acuicultura.

O objetivo deste trabalho foi avaliar a composição química e os teores de ácidos graxos do camarão-amazônico e do camarão-da-malásia. Após cultivo de quatro meses, com a mesma dieta para ambas as espécies, os principais ácidos graxos saturados foram o palmítico e o esteárico. O oleico foi o principal ácido graxo monoinsaturado, e o eicosapentaenoico e o docosahexaenoico foram os ácidos poli-insaturados mais abundantes. O camarão-amazônico apresenta níveis mais elevados de proteínas e de ácidos graxos poli-insaturados do que os do camarão-da-malásia, o que mostra seu potencial para a aquicultura.

The objective of this work was to evaluate the chemical composition and fatty acid contents of Amazonian and giant river prawns. After four-month farming, with the same diet for both species, palmitic and stearic acids were the main saturated fatty acids. Oleic acid was the main monounsatured fatty acid, and the eicosapentaenoic and docosahexaenoic acids were the most abundant polyunsaturated acids. Amazonian prawn has higher levels of protein and polyunsaturated fatty acids than those of the giant river prawn, which shows its potential for aquaculture.

The giant river prawn, Macrobrachium cf. rosenbergii, is one of the most cultivated freshwater prawns in the world and has been introduced into more than 40 countries. In some countries, this prawn is considered an invasive species that requires close monitoring. Recent changes in the taxonomy of this species (separation of M. rosenbergii and M. dacqueti) require a re-evaluation of introduced taxa. In this work, molecular analyses were used to determine which of these two species was introduced into Brazil and to establish the geographic origin of the introduced populations that have invaded Amazonian coastal waters. The species introduced into Brazil was M. dacqueti through two introduction events involving prawns originating from Vietnam and either Bangladesh or Thailand. These origins differ from historical reports of the introductions and underline the need to confirm the origin of other exotic populations around the world. The invading populations in Amazonia require monitoring not only because the biodiversity of this region may be affected by the introduction, but also because admixture of different native haplotypes can increase the genetic variability and the likelihood of persistence of the invading species in new habitats.

Some morphometric relationships in Macrobrachium amazonicum (Heller, 1862) reared in earthen ponds were studied. A total of 239 individuals were collected, sexed and sorted to juvenile or adult. Total length (Lt), post-orbital length (Lpo), carapace length (Lcp) and queliped length (Lql) were measured. The relationships Lt/Lpo, Lpo/Lcp and Lt/Lcp are the same for juveniles, males and females, indicating unchanged growth pattern during post-larval ontogenetic development. While Lt/Lpo showed isometric growth, Lpo/Lcp and Lt/Lcp showed negative allometry. On the other hand, for the Lql/Lcp relationship, juveniles showed isometric growth, females slight positive allometry and males a strong positive allometry. It suggests that the importance of chelipeds may be different in these groups. Quelipeds play important role on food capture and on agonistic, social and reproductive behavior. Therefore, inter and intraspecific interactions may change during prawn growth, even after morphological

Feeding behavior of the larvae's prawn, Macrobrachium rosenbergii De Man, 1879, in each stage of development was studied face alArtemia Linnaeus, 1758 nauplii, dry and wet diets. Groups of ten larvae in each stage were placed in 500 ml beakers at 29ºC in filtered brackish water. After the fasting period of acclimatization, the three types of food were offered separately to the larvae and the feeding behavior was observed during 30 min. Feeding perception, capture, grasp and ingestion of food were used to determine feeding pattern. Stage I lawac do not eat. The feeding behavior of larvae was similar on the stages II - XI. The perception in distance does not occur in most individuais; the feeding process generally started with the physrcal contact of food with the animal. Food is captured by thoracic appendages (maxillipeds until stage III, and maxillipeds + pereopods in stages IV - XI) and particles are grasped and handled by maxillipeds. Inopposition at the capture, the ingestion is a seletive process. Selective responses decrease in later stages and larvae become omnivorous in greater degree.

In this paper, female Macrobrachium carcinus (Linnaeus, 1758) maturation curve, weight/length relationship, length and weight growth curves were studied. Prawns were captured, by traps, in Ribeira de Iguape river (24ºS and 47ºW), southern Brazil. There were used 207 females. It was observed that M. carcinus presents several spawnings during its life cycle and reproductive period goes on, at least till six years old. Weight/length relationship can be represented for the equation W = 8.73 E-3 L3.28. Expressions obtained for length and weight growth curves are Lt = 21 .0 (1-e-0493t) and Wt= 190 (1-e-0493t)3.28. respectively. A symptotic maximum length and asymptotic maximum weight are nearly attained at six and eight years old, respectively.

In this article the length growth curves of Macrobrachium rosenbergii (De Man, 1879) held in different population densities were analysed. Postlarvae prawns were stocked into five 0,02 ha earthen ponds at densities of 4, 8, 12, 16 and 20 ind./m² during six months. Forthnightly, the mean total length of animals from each pond were obtained by means of random samples. For each population the length growth curves and the instantaneous growth rate expressions were determined. The growth rate and the asymptotic maximum length decreased with the stocking density raised. This effect is greater when the density ranges in low levels. The growth decrease can be due to intraspecific competition for life resources and to negative interactions between individuals, as aggressive or social behavior, that increase with the increase prawns density.

In this paper, the fecundity in Macrobrachium acanthurus (Wiegmann, 1836) of the Ribeira de Iguape river (Southern Brazil) (Crustacea, Decapoda, Palaemonidae), is presented. The mean individual fecundity of the population was estimated. Fecundity was related to either length and/or weight. Our data showed that this species presents high fecundity and is thus suitable for comercial culture. The fecundity/length and fecundity/weight relationships obtained are: F = - 14 712 + 2 311,8 L and F = -1493,9 + 798,76 W

In this paper, the relative growth of Macrobrachium acanthurus (Wiegmann, 1836) (Crustacea, Decapoda, Palaemonidae), is presented; the cephalothorax length/abdominal length, telson length/abdominal length and abdominal length/total length relashionships were determined. The adjusted equations showed a isometric growth pattern. There are no changes in these relationships during the animals growth that may be significant in the maximization of the meat's profit.