Susana María Velurtas

In vivo and in vitro protein digestibility of formulated feeds for Artemesia longinaris (Crustacea, Penaeidae)

This study was undertaken to determine the in vivo crude protein apparent digestibility in the prawn Artemesia longinaris, using feeds with 0.25% of chromic oxide and animal (fish meal, meat and bone meal and squid protein concentrate) and plant (soybean meal) ingredients. Three replicate groups of prawn were fed and the feces were collected. The rate of protein hydrolysis was measured in vitro using midgut gland enzyme extract from the prawns fed the respective feeds and was compared with those found with enzyme extract of wild prawn. The in vivo apparent digestibility coefficients showed significant differences among the feeds (P<0.05). Fish meal feed presented the highest digestibility (92%); intermediate digestibility (83%) was found for meat and bone meal feed, and the less digestible feed (63%) was that containing soybean meal and squid proteins concentrate. No significant differences in the in vitro protein digestibility were found among the experimental feeds. The results indicated the limitation of in vitro enzyme assays and that it should be complemented by in vivo studies.

Ontogenetic changes in the digestive system of Pleoticus muelleri (Decapoda, Penaeoidea)

Summary The present study describes the ontogenetic changes observed in the histology and in total protease, trypsin, and chymotrypsin activities of the digestive system in the shrimp Pleoticus muelleri (Decapoda, Penaeoidea) under culture conditions. The stomach development follows the typical pattern described for other decapods. The gland filter develops during larval stages, while the astric mill takes the adult shape during postlarval metamorphosis and juvenile stages. During early larval stages, the histological structure of the anterior and lateral caeca is similar to that of the adult midgut gland, with R, F and B cells. During late larval stages, the anterior caeca decline and take a structure similar to that of the mesodeum and the lateral caeca expand to form the adult midgut gland by proliferation of tubules in antero-posterior direction and from the cortical region to the medullar region. Total protease activity was higher in postlarvae 45, no significant differences was found in the others larval and p larval stages. Trypsin activity was lowest in early postlarval stages (PL1 and PL6), coinciding with the metamorphosis; enzyme activity increased in postlarvae 10 followed by a significant decrease in postlarvae 26. Chymotrypsin showed a significantly lower activity in protozoea 3, a peak of activity between postlarvae 1 and 10, and a decrease in the following postlarval stages. The inhibition of trypsin and chymotrypsin activities were confirmed the presence of these serine proteases during developmental stages. The ontogenetic pattern of P. muelleri digestive system morphology is similar to those described of others penaeoids. The recorded variation in enzyme activity during developmental stages may be associated with the unique postlarval life history. This research has implications for artificial diet development in crustacean culture and understanding of dietary shifts during larval development.

Influence of dietary starch and cellulose levels on the metabolic profile and apparent digestibility in penaeoid shrimp

The present study compared the effect of different starch/cellulose ratios (30/0, 20/10, 10/20, 0/30) on the metabolic response and apparent digestibility in two species of penaeoids: Artemesia longinaris and Pleoticus muelleri. Adult animals were used in order to obtain sufficient quantities of haemolymph and faecal material for analysis. No significant differences were found in levels of plasma metabolites in P. muelleri, but in A. longinaris, a significant increase was observed in glucose, total protein, and cholesterol in correlation with increased dietary starch. The apparent digestibility coefficients decreased from 83.7% to 51.2% (A. longinaris) and from 71.9% to 7.6% (P. muelleri) as the dietary starch levels increased. The ratio of amylase activity to protease activity (A/P ratio) declined in A. longinaris when the percentage of dietary starch increased. In contrast, the A/P ratio for P. muelleri increased with higher starch concentrations. These results demonstrated a close relationship between the feeding habits and digestive physiology of the two species studied; they also suggest a more herbivorous behavior for A. longinaris and more omnivorous habits for P. muelleri.

Effects of different dietary vitamin A levels in the red shrimp Pleoticus muelleri (Bate, 1888) (Decapoda, Solenoceridae)

Se evaluo el crecimiento, la supervivencia, morfologia celular, estructura y la actividad enzimatica de proteinasas del hepatopancreas del langostino Pleoticus muelleri (Bate, 1888). Se realizo un experimento con juveniles en acuarios durante 6 semanas. Los animales fueron alimentados con dietas semipurificadas con diferentes niveles de vitamina A (140, 160 y 180 mg vitamina A kg-1 dieta). No hubo diferencias significativas en supervivencia e incremento en peso en los distintos tratamientos en las condiciones de trabajo. El estudio histologico permitio visualizar cambios estructurales en el hepatopancreas de los individuos alimentados con diferentes niveles de vitamina A. Los organismos del tratamiento de 180 mg kg-1 presentaron una morfologia funcional normal, en cambio en los alimentados con las otras dietas se observo un deterioro del organo que denota signos de desnutricion, tales como: hiperplasia e hipertrofia celular, desorganizacion del tejido y retraccion celular. La mayor actividad de proteinasas se registro en los tratamientos de 140 y 160 mg kg-1 y se observo una disminucion significativa en el de 180 mg kg-1. Se puede concluir que el nivel recomendado de vitamina A en la dieta para P. muelleri es de 180 mg kg-1 y que en situaciones de desnutricion el hepatopancreas presenta importantes cambios estructurales y alteracion en la actividad de las proteasas.

Effect of Dietary Astaxanthin on Free Radical Scavenging Capacity and Nitrite Stress Tolerance of Postlarvae Shrimp, Pleoticus muelleri

The aim of this study was to investigate the effect of astaxanthin feed supplementation and environmental nitrite stress in postlarvae of Pleoticus muelleri (15 ± 0.004 mg initial weight) under culture conditions. Diets containing three levels of astaxanthin, 0 mg kg(-1) of diet (C0), 100 mg kg(-1) of diet (C(100)), and 300 mg kg(-1) of diet (C(300)), were used. Postlarvae fed with each diet were exposed to different concentrations of nitrite (NO(2)Na) (0-200 mg L(-1)). The 96 h median lethal concentration (LC50) values of nitrite N were 76.3, 89.7, and 157 mg L(-1) for shrimps fed to C0, C(100), and C(300). The scavenging properties were evaluated against the stable 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical by electron resonance spectroscopy (EPR). For all feed treatments, the extracts exhibited strong DPPH scavenging activity; however, shrimp fed with C(100) and C(300) showed the greatest activity to quench DPPH (62 and 59%, respectively) with respect to C0 (43%). It can be concluded that astaxanthin acts as a protector of nitrite stress in P. muelleri.

Correlation between radical scavenging capacity and carotenoid profile during Pleoticus muelleri larval development

The purpose of this study was to measure the concentration of carotenoids and properties which occur in tissues to neutralize free radicals during ontogeny of Pleoticus muelleri. The stages of nauplius, protozoea, mysis and postlarvae of 1, 6, 10, 26, 30 days were examined from hatchery raised postlarvae from wild females. The β-carotene and the astaxanthin from the lyophilized tissue were quantified using a ultraviolet–visible spectrophotometer. Free radicals scavenging properties of tissues extracts were evaluated by electron paramagnetic resonance (EPR). The reaction of protective substances was followed with the 1,1-diphenyl-2-picryhydrazyl (DPPH) radical. The concentration of carotenoids of the whole larvae and postlarvae ranged from 1.72 to 87.04 µg g−1 for β-carotene, and 2.26 to 19.86 µg g−1 for astaxanthin. All the larval and postlarvae stages showed a protective capacity. In the stages of mysis, postlarvae 1 and 30 the homogenates were monitored without DPPH. The undefined EPR signal was quantified and considered as a “pool” of persistent radicals, with a concentration about 10−5 M. A relationship was observed between the concentration of carotenoids and the protective capacity of the homogenate. The postlarvae stages had a high concentration of carotenoids and the greatest protective capacity.