Sistema Regional de Información
en línea para Revistas Científicas de América Latina,
el Caribe, España y Portugal

Previous studies have shown that crustacean feed attractability has an enormous importance, because the consumption, quality and feed conversion rate can be improved, by reducing the time of residence pre-ingestion and the leaching of nutrients. For this reason, different protocols and methods has been developed to measure feed attractability. This study evaluated the use of maze type Y, and rectangular systems to determine the attractant power of a commercial feed on longarm river prawn Macrobrachium tenellum. The Y type maze system without barriers, and with three different types of barriers (with or without access to the area where a commercial feed) was evaluated. Ten prawns were placed in the acclimation chamber of the system at 28°C for 60 min before the start of the experiment. To start the test, commercial feed (20% of prawn biomass) was placed into the system feeding area, then the acclimation chamber was open to allow for the free prawn movement, evaluating the feed attractability by measuring the time for the first “hit”, total number of hits, and the number of prawns which entrances to the feeding area during 15 min. Similar tests were performed with a rectangular type maze system, comparing the atractability results obtained in both systems. The results presented here highlight the importance of the genus behavior and the selection of protocols and systems, as well as the materials used in its maze system construction, for attractability testing in M. tenellum.

An 18-week feeding trial was conducted to estimate the optimum dietary pantothenic acid (PA) requirement for juvenile of Lutjanus guttatus. Seven isoproteic and isocaloric practical diets were formulated containing graded levels of pantothenic acid (PA) 2.57, 31.97, 47.91, 63.79, 76.83, 103.15 and 121.91 mg kg-1 . Triplicate groups of 15 fish, with an initial weight of 10.2 ± 1.4 g, were cultured in 21 glass-fiber tanks and received each diet at random three times daily to apparent satiety. Results showed that the weight gain of fish fed diet 2.57 mg kg-1 PA was significantly less than the weight gain of fish fed diets containing greater quantities of PA. However, no significant differences were observed in the weight gain of the fish fed diets containing between 31.97 to 121.91 mg kg-1 PA. External signs of deficiency in the fish of diet (2.57 mg kg-1PA) included caudal fin erosion, desquamation of the skin, hemorrhages in the body and fins, lethargy and 80% mortality rate were recorded. Hematological parameters indicated that there was no clear reduction of hemoglobin with PA in the diets. The dietary PA requirement to attain maximum growth rate, good survival, and the absence of external injuries range between 40.10 and 44.29 mg kg-1 .

The freshwater shrimp genus Macrobrachium is highly diverse, distributed in tropical and subtropical regions around the world, and of considerable commercial importance in many countries. Here we present the results of an analysis of the scientific production regarding Macrobrachium published between 1980 and 2016 in the database Web of Science. The evaluated indicators were key words and authors producing the scientific literature about this genus. Concept maps and cluster analysis techniques were used to display the relationships between them. The results of the study visualize the temporal development of scientific knowledge of the genus Macrobrachium and describe the development of authorship networks during 36 years study period. Moreover, the results of the analysis show emerging research trends in the field of Macrobrachium studies.

The brown sea cucumber Isostichopus fuscus is the most important commercial holothurian in the eastern Pacific, and its high market value caused overfishing and sharp declines of its populations and catches in several Latin American countries. In Mexico, the fishery has been intense in the northern Gulf of California since the 1990s, and it is currently under strong regulation. To evaluate the current status of the organisms, we measured the size, weight and estimated the relative condition index (Kn) of 702 specimens sampled in 86 rocky reefs of that region in 2016, at depths from 3 to 22 m. Mean length ± SD was 22.32 ± 5.23 cm, lower than average in the northern Gulf, but nevertheless, the average weight was 420.61 ± 192.48 g, among the highest recorded in the eastern Pacific; this is presumably due to the high primary production of the region that favors the presence of well-nourished organisms. The weight (W)-length (L) relationship was W = 3.27 L1.56, and condition index ranged from 0.045 to 2.13 (mean Kn = 0.96 ± 0.29), a figure that did not differ to that reported along the Mexican Pacific. There were differences in the value of Kn among sites, being higher in areas that are subject to the low fishing effort.

The present study aimed to identify yeasts species isolated from fish feed and the intestinal tracts of tambatinga fish (Colossoma macropomum × Piaractus brachypomum) cultivated in a Brazilian fish farm. Twenty tambatingas and 30 fish feed samples from different brands were acquired from two commercial establishments in the state of Piauí, Brazil. The sampled guts were divided into three equal parts, namely the anterior, medium and posterior portions, totaling 60 samples. Molecular identification was performed by PCR amplification and sequencing of the D1/D2 regions of the large rRNA subunit gene. Sixteen Candida nivariensis strains in the gut were identified. The fish feed samples showed a higher variability of yeast species, with the following species isolated: Hyphopichia burtonii (23.08%), Lodderomyces elongisporus (15.39%) and Trichosporon asahii (15.39%), Candida nivariensis (7.69%), C. orthopsilosis (7.69%), C. parapsilosis (7.69%), Rhodotorula minuta (7.69%), Sterigmatomyces elviae (7.69%), Cryptococcus liquefaciens (7.69%). Yeast found in feed, however, was not always isolated from tambatinga gut. Molecular identification allowed for the isolation of yeast species not previously reported in fish feed and gut samples.

The high production levels of the Chilean salmon farming industry have resulted in the emergence of several diseases that affect all stages of development of cultured species. The parasitic copepod Caligus rogercresseyi is considered a potential vector of pathologies, and different chemical compounds such as pyrethroids and organophosphates have been used to prevent and control sea lice outbreaks. In this study, the effect of azametiphos, deltamethrin, and emamectin benzoate on the larval stages of the mussel Choromytilus chorus and the sea-urchins Sphaerechinus granularis and Paracentrotus lividus was explored. No effects were found in the final larval development of C. chorus (D larvae). However, the trochophore development seemed accelerated in the presence of pesticides compared to the control larvae. In the case of P. lividus and S. granularis, exposure to all pesticides caused an increase in the rate of abnormal larval development compared to the control.

The present work evaluates the attractant and palatable potential of six ingredients of animal origin in longarm river prawn Macrobrachium tenellum juveniles in a Y type maze system. Ingredients were pelletized for the first bioassay and included in neutral gelatin (in wet base) in the second bioassay. The ingredient to evaluate was placed in one of the Y-maze arms, allowing the free movement of prawn for 15 min. On both bioassays, attractability was evaluated by quantifying the time required for the first prawn to enter the region where the feed was found and the total of prawns which entered that region. In the second bioassay, also evaluated the palatability quantifying the time for the first prawn to have contact with the ingredient, the total of prawns which had contact with it and the time they remained feeding. No significant differences were obtained between treatments in the first bioassay. Significant differences were found in the second bioassay showing that pork meal, fish meal, feather meal and shrimp meal have greater attractability due to the number of prawns attracted, results also show significant differences in palatability, where fishmeal, shrimp meal and pork meal stimulating a higher number of organisms and promoting a longer consumption time.

In this research it was evaluated the effect of background color on the development of the chromatophores in Macrobrachium tenellum prawns, six juvenile prawns were exposed to five background colors: black, white, pink, red, white and green; each one in triplicate, for 60 days. The development of the chromatophores was evaluated by means of the chromatophores index using a scale of 1 (the maximum concentrated pigment) to 5 (the maximum dispersed pigment). The coloration was analyzed in four anatomical regions of the organisms with the HSB model (hue-saturation-brilliance). The results show that the prawns modify their pigmentation according to the different background colors of experimental aquariums.