Ana Cristina Díaz

Growth, molt and survival of Palaemonetes argentinus (Decapoda, Caridea) under different light-dark conditions

Growth, survival and molting rate in Palaemonetes argentinus Nobili, 1901 were compared under different light-dark conditions. During 80 days, 150 immatures of both sexes (initial mean weight 0.09±0.002g), from Los Padres lagoon, Mar del Plata, Argentina, were maintained in aquaria at 19±0.4°C under three light conditions: 0:24, 10:14 and 13:11 (L-D). They were fed daily on an artificial diet (45% proteins, 17.2% lipids, 7% water, 7% ash). Good weight increment was obtained with the three treatments, finding a positive linear correlation between mean weight and time (0:24, r=0.97; 10:14, r=0.99; 13:11, r=0.98). There were no significant differences in the percentage increment in mean weight among the treatments (0:24, 19.3%; 10:14, 29.3% and 13:11, 26.5%) (p<0.05). Molting rate was significantly higher at a long-day photoperiod (MR=1.7) than at a short-day (MR=0.6) or continuous dark condition (MR=0.3) (p<0.05). The lowest survival was found in animals maintained under 13:11 L-D conditions (77%), being statistically different of the other two treatments (92% and 89% at 10:14 and 0:24, respectively) (p<0.05). These results suggest that the best growth and survival in P. argentinus result with a 10:14 L-D cycle, and that the growth is less affected by photoperiod than molting rate and survival.

Functional cytology of the hepatopancreas of Palaemonetes argentinus (Crustacea, Decapoda, Caridea) under osmotic stress

The present work describes the effect of different salinities on the functional morphology of the P. argentinus hepatopancreas and analyses the tissue recovery after re-acclimation to freshwater. Adult prawns of both sexes at sexual rest were collected from a tributary of the Mar Chiquita coastal lagoon. The prawns were acclimated in aquaria to four salinity conditions: 0 (control), 8, 16 and 24‰. To evaluate the possible tissular recovery, after 60 days individuals from all the treatments were gradually acclimated to freshwater and maintained for other 30 days. Hepatopancreas samples were processed at the beginning of the trial and every 30 days using standard histological techniques for OM and TEM. The individuals from all the treatments, except the controls, showed a continuous weight decrease, and survival was lower when higher the salinity. At 30 days from the beginning of the experiment, hepatopancreas from 16 and 24‰ salinities showed an enlarged tubular lumen and an infolded basal lamina. Ultratructurally, nuclear retraction, cytoplasmolysis, and RER membranes separated with electron-dense content were observed in all the treatments except 0‰. After 60 days, profound alterations were observed with the three treatments. After the re-acclimation period, there was no reestablishment of the functional cytology. The tolerance to short-term salinity changes explains the capability of this prawn to inhabit in estuarine environments.

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.

Morphological and functional study of the male reproductive tract in the shrimp Pleoticus muelleri bate (Decapoda, Penaeoidea)

Summary Anatomical relationships and the histological structure of the male reproductive tract in Pleoticus muelleri were described by using light microscopy. The male reproductive tract consists of paired organs: testes and vasa deferentia with the terminal ampoule, which opens at the gonopores on the coxae of the fifth pair of pereopods. Testes are located dorsally in the cephalothorax and are comprised of two lobes surrounded by laminar connective tissue. They are composed of cystic structures (with spermatogonia or primary spermatocytes) covered by connective tissue. Each vas deferens consists of four morphologically different zones: the collecting tubule, proximal, medial, and distal (terminal ampoule). The collecting tubule connects the testes with the proximal zone and is lined by a shallow epithelium. The proximal zone, lined by a columnar secreting epithelium, is internally divided into two ducts by a septum. The biggest spermatophoric duct conveys the sperm mass, and the other secretes the acellular material that supports the sperm mass in the spermatophore. In the medial zone the ducts are incompletely separated by a partial septum and the epithelial cells secrete the hyaline layer of the spermatophoric matrix. The distal zone or terminal ampoule comprises four interconnecting chambers and is externally surrounded by connective tissue and a conspicuous layer of striated muscle. The spermatophore reaches complete maturation in the terminal ampoule.

GROWTH OF THE PRAWN, PALAEMONETES ARGENTINUS NOBILI, 1901 (DECAPODA, PALAEMONIDAE) ON DIFFERENT FEEDS

Our aim was to study the individual growth of Palaemonetes argentinus in the laboratory, and to analyse the effect of diet on both moult increment and intermoult period. Juveniles collected from Los Padres lagoon (38°S 55°W) were maintained individually in 400 ml containers with aerated fresh water under a constant regime (19 ± 2°C; 11 : 13 h L/D) and fed daily. Three different feeds were given: frozen shrimp (76% proteins, 17% lipids) and two formulated diets, i.e., E(0.5) and M91 (containing 45 and 54% proteins, and 17 and 14% lipids, respectively). The moult increment was studied by comparing premoult and postmoult weight and cephalothorax length, and by next determining a linear regression according to Kurata (1962), which resulted in an arithmetic growth with the M91 diet (b = 0.96) and geometric regressive growth with E(0.5) (b = 0.94) and shrimp (b = 0.88) for the weight values. Length data yielded geometric regressive growth, with coefficients of 0.91, 0.79, and 0.91 for E(0.5), M91, and shrimp regimes, respectively. The average duration of the intermoult period was: E(0.5), 16 ± 2 days; M91, 18 ± 2 days; frozen shrimp, 18 ± 3 days. Comparing survival, moulting rate, and growth, the prawns grew best under the M91 dietary regime. These results indicate that, in this species, a food with approximately 50% protein and with a high proportion of animal-based ingredients produces satisfactory growth and survival. Se estudio el crecimiento individual de Palaemonetes argentinus en laboratorio, analizando el efecto de la dieta sobre el incremento por muda y el periodo de intermuda. Se mantuvieron individualmente camarones juveniles obtenidos de la laguna de Los Padres (38°S 55°W) en recipientes de 400 ml con agua dulce aireada y bajo condiciones constantes de temperatura y fotoperiodo (19±2°C; 11 : 13 h L/O). Se alimentaron diariamente probando tres alimentos: camaron congelado (76% de proteinas, 17% de lipidos) y dos dietas formuladas, E(0,5) y M91 (conteniendo 45 y 54% de proteinas y 17 y 14% de lipidos, respectivamente). El incremento por muda se estudio comparando el peso y la longitud del cefalotorax premuda y postmuda, analizando su ajuste a distintos modelos de regresion lineal de acuerdo con Kurata (1962). A partir de los datos se determino un crecimiento aritmetico con la dieta M91, con un coeficiente de crecimiento en peso b = 0,96; geometrico regresivo con E(0,5) (b = 0,94) y camaron (b = 0,88). En cuanto al crecimiento en longitud fue geometrico regresivo con las tres dietas, con coeficientes de 0,91, 0,79 y 0,91 para E(0,5), M91 y camaron, respectivamente. La duracion promedio del periodo de intermuda fue: E(0,5), 16±2 dias; M91, 18±2 dias; camaron congelado, 18±3 dias. Comparando la supervivencia, la tasa de muda y el crecimiento, los camarones crecieron mejor con la dieta M91. Estos resultados indican que, para esta especie, una dieta con aproximadamente 50% de proteinas totales con una alta proporcion de proteinas animales produce un crecimiento y una supervivencia satisfactorios.

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.

Efecto de la ablacion peduncular en la maduracion gonadal de Pleoticus muelleri bate (decapoda, solenoceridae). I. interaccion entre muda y desarrollo ovarico

Este trabalho teve como objetivo comparar o grau de desenvolvimento ovariano de remeas ablacionadas e intactas de Pleoticus muelleri e avaliar a influencia da ablacao sobre a frequencia da muda. As femeas, de 7 a 22 g de peso, foram mantidas em condicoes de cultivo com fotoperiodo de 12:12, temperatura entre 15 e 17ÂoC, salinidade de 31 e alimentadas com lula, camarao e bivalvos frescos. Foram pesados e fixados os ovarios e hepatopâncreas, realizando um controle histologico nos 4; 9; 15; 20; 40 e 50 dias. O indice gonadossomatico variou entre 0,925 e 3,747 (controle) e entre 1,457 e 5,035 (ablacionados). Determinou-se valores de indice hepatopancreatico entre 2,059 a 4,520 (controle) e de 3,471 a 4,471 (ablacionados). A duracao media da intermuda foi 21,7 :j: 3,9 e 23,2 :j: 2,4 dias para o grupo controle e ablacionados, respectivamente. Ao finalizar o experimento a analise histologica demostrou que os ovarios das femeas ablacionadas encontravam-se totalmente amadurecidos e os do controle em vitelogenese primaria. Conclui-se que a ablacao peduncular acelera a maturacao ovariana de P. muelleri, sem modificar a frequencia da muda. O indice ovariano e independente do tamanho no intervalo de peso estudado e a ablacao nao apresentou efeito sobre o peso relativo dos hepatopâncreas.