Jorge L. Fenucci

Digestive proteinases of red shrimp Pleoticus muelleri (Decapoda, Penaeoidea): partial characterization and relationship with molting.

The present study describes the activity and some characteristics of proteinases in the hepatopancreas of red shrimp Pleoticus muelleri during the different stages of the molting cycle. Proteolytic activity was highest between pH 7.5 and 8. The hepatopancreatic protein content in the premolt stage was higher than in the other stages of the molting cycle (P<0.05). No significant differences were found in total proteolytic activity in the hepatopancreas when comparing molting stages. The proteolytic activity of the P. muelleri hepatopancreas enzyme preparations is the main responsibility of serine proteinases. TLCK, a trypsin inhibitor, reduced azocasein hydrolysis between 26% (intermolt) and 37% (premolt). TPCK, a chymotrypsin inhibitor, did not decrease hydrolytic activity, except for in postmolt. Low trypsin and chymotrypsin activities were found during intermolt, and increased in postmolt. The electrophoretogram of the enzyme extracts shows 12 bands of activity during intermolt (from 16.6 to 53.1 kDa). Some fractions were not detected in the postmolt and premolt stages. Three low molecular weight trypsin forms (17.4, 19.1 and 20 kDa) were found in all molting stages. One band of chymotrypsin (21.9 kDa) was observed in all molting stages. High molecular mass active bands (66-205 kDa) could not be characterized with inhibitors. Comparison of the protease-specific activity of the hepatopancreas of some species indicated a relationship between digestive enzyme activity and feeding habits of the shrimp. Omnivorous shrimp, such as Penaeus vannamei (syn: Litopenaeus vannamei) and Penaeus monodon, showed higher protease activity than the carnivorous shrimp, Penaeus californiensis (syn: Farfantepenaeus californiensis) and P. muelleri. In fact, the enzymatic activity in the hepatopancreas of P. muelleri showed variations in relation to feeding habit and molting cycle.

Digestive proteinases of Artemesia longinaris (Decapoda, Penaeidae) and relationship with molting

Digestive proteinase activities of Artemesia longinaris were assayed at different stages of the molting cycle. Total proteolytic activity in the hepatopancreas was highest during postmolt. Trypsin and chymotrypsin activities were highest during intermolt. Specific inhibitors and zymograms of A. longinaris hepatopancreas extracts showed four trypsins (14.79, 15.49, 16.60, 17.38 kDa, respectively) and three chymotrypsins (21.38, 22.91, 27.54 kDa, respectively). Our results suggest that proteolytic activity in the hepatopancreas of A. longinaris is influenced by the molting cycle. Types and activity of prawn digestive enzymes constitute background information to further study the digestive abilities of these organisms and will lead to understanding their nutritional needs and feeding ecology.

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.

Calidad de los quistes de Artemia persimilis (Piccinelli & Prosdocimi) (Crustacea: Branchiopoda) de diferentes zonas de Argentina, como alimento en acuicultura

Se evaluo la calidad de los quistes de Artemia persimilis (Piccinelli & Prosdocimi 1968) procedentes de las salinas de las provincias de Buenos Aires, La Pampa y Cordoba. Para ello, se determinaron las tallas de huevos, numero de quistes por gramo, tallas de nauplios, porcentajes y tiempos de eclosion, tiempos de sincronia (Ts), luego del tratamiento con H2O2 y el analisis de la calidad nutricional de los quistes en lo referente a proteinas, lipidos totales, acidos grasos, cenizas y humedad. Los resultados fueron satisfactorios, con porcentajes de eclosion que variaron, en general, entre un 60% y 80% y Ts que no superaron las 7,5 h. El diametro promedio con el desvio estandar de los quistes hidratados, tuvo valores entre 184,7 26,29 µm (Salina El Chancho) y 248,6 17,29 µm (Salina Colorada Grande). El numero de quistes por gramo vario entre 102.600 (Salinas Grandes de Anzoategui) y 276.000 (Salinas Grandes de Hidalgo). La talla promedio con el desvio estandar de los nauplios vario entre 350,6 36,01 µm (Salina El Chancho) y 512,1 63,44 µm (Salina Colorada Grande). El tratamiento de los quistes con H2O2, redujo los Ts. Con respecto a la calidad nutricional, se obtuvieron valores comparables a los que se comercializan actualmente. Se puede afirmar que los quistes de Artemia persimilis podrian ser utilizados como alimento en acuicultura.

Comparative Evaluation of Different Animal Protein Source in Juveniles of Pleoticus Muelleri (Crustacea, Penaeoidea)

A study was conducted to evaluate alternative protein supplements that could be used to reduce the cost of formulated diets for shrimp. Marine proteins, such as fish meal, squid meal, and bivalve meal, are considerably more expensive than byproduct meals such as meat and bone meal. The objective of this study was to compare the growth, survival, and body composition of juvenile Pleoticus muelleri fed diets containing different levels of meat and bone meal as a substitute of the marine fish meal. Feeding trials were carried out on early juveniles (0.70 ± 0.05 g initial weight) held in 150 l glass aquaria (33% salinity, 20°C, 12:12 h photoperiod, 20 shrimp/m2 density). Each diet (control, PL1, PL2, PL3, PL4) was tested in three replicate groups of 10 shrimps during 50 days. The juveniles were obtained from hatchery-raised postlarvae (wild broodstock from Mar del Plata, Argentina) at Nagera Station, dependent of the Marine Science Department (Mar del Plata National University, Argentina). Four isoproteic and isolipidic diets (34% crude protein) were prepared to contain 0, 11, 15 and 23% meat and bone meal in substitution of fish meal. The control group was fed with fresh squid mantle. Percentage increment in mean weight varied between 81 and 103%. Survival rates ranged from 50 to 76%. No significant differences were detected in final weight gain or survival among dietary treatments (P < 0.05). Whole body moisture, ash, crude protein, and lipid content of shrimps were not affected by diet (P < 0.05). The feeding experiment suggests that meat and bone meal can be utilized by P. muelleri as a suitable replacement for fish meal in a formulated diet.

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.

Alimentación de protozoeas del langostino Pleoticus muelleri Bate utilizando diferentes microencapsulados y especies de microalgas

The aim of this work was to obtain an adequate diet for the growth and survival of protozoeal stages of Pleoticus muelleri. Parabolic tanks of 10 liters wer...

Vitamin E Requirement of the Prawn Artemesia Longinaris (Decapoda, Penaeidae)

Two trials were conducted to evaluate the growth and survival of Argentine prawn Artemesia longinaris fed with different levels of vitamin E and BHT (butylated hydroxytoluene) in a semi purified diet. The feeding trial consisted of 0, 1500 and 3000 mg vitamin E/kg diet, and 0.5 mg BHT/kg diet (trial 1) and 500, 1000, 1500 and 2000 mg vitamin E/kg diet (trial 2). After 40 days (trial 1), survival of prawns fed diets with 3000 mg vitamin E/kg diet was significantly (P < 0.05) lower (59%) than the other treatments. Prawns fed diets supplemented with 1500 mg/kg diet exhibited high weight gain (71.3%), however no significant differences were found among treatments. After 32 days (trial 2), prawns fed a diet containing 1500 mg vitamin E, exhibited higher survival (72%), than the other treatments (53–64%), and the percent weight gain ranged from 38.1 to 61.5% with no significant differences among treatments. The results of this study indicate that the dietary vitamin E requirement of A. longinaris, under the particular experimental conditions, is around 1500 mg/kg diet.

Effect of Different Dietary Arginine and Lysine Levels for Argentine Prawn Artemesia Longinaris Bate (Crustacea, Decapoda, Penaeidea)

Amino acids are essential for synthesis of tissular proteins and many other important compounds. It has been determined a lysine - arginine dietary relationship and it is believed that the ratio of these compounds in diets should be maintained between 1:1 and 1:1.1. Three experiments were conducted using Artemesia longinaris to determine the effect of different arginine:lysine ratios in diets. The experimental diets contained 1:4, 1:1, 1:2 and 2:1 arginine to lysine ratios. Prawns exhibited no significant differences in growth and survival among treatments.