Elena Irene Cuartas

Morphology and function of the reproductive tract of the spider crab Libinia spinosa (Crustacea, Brachyura, Majoidea): pattern of sperm storage

Morphology and function of the male reproductive tract, female spermatheca and patterns of sperm storage were assessed in the crab Libinia spinosa using histological methods. Testes are characterized by the presence of peripheral spermatogonia and different sequences of sperm maturity. Spermatophores begin to be packed in the last portion. The vas deferens consists of three sections: anterior, with undeveloped spermatophores and free sperm; median, with well-developed spermatophores; and posterior with granular secretions. Female spermathecae are of the ventral type, with a velum separating dorsal and ventral chambers. Live individuals were kept in the laboratory and arranged in pairs. An experiment was conducted toward the end of the reproductive season, in which males with the right gonopod excised were placed with receptive females. After mating, females were killed and the spermathecae dissected for histological study and observation of the pattern of sperm storage. Spermatozoa were found forming discrete sperm packages. New ejaculates can fill the entire spermatheca or be restricted to the ventral chamber; sperm are rounded, with a distinguishable acrosomal core. Old ejaculates are restricted to the dorsal chamber and are of irregular shape and larger size; an acrosomal core was not distinguishable. The secretions produced by the glandular epithelium of the dorsal chamber of the spermathecae are likely to have a role in the removal of dead sperm.

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.

Reproductive System and Size Maturity of the Paddle Crab Ovalipes trimaculatus (Brachyura: Portunidae) Along the Argentine Coast

Ovalipes trimaculatus (de Haan, 1833) is a commercial species captured in the Mar del Plata coast, Argentina. However, no studies were conducted in order to study its population features neither its reproductive biology. The morphometric and physiological maturity of both sexes, the histology of the female seminal receptacle and ovary, and the ultrastructure of the male gonopods were studied in the present paper. In females, morphometric maturity (44.6 mm of carapace width, CW) was acquired prior to physiological maturity (54.6 mm CW). By contrast, in males, physiological maturity (46.6 mm CW) was acquired prior to morphometric maturity (52.3 mm CW). The ovary is connected to the dorsal part of the seminal receptacle. Neither Spermatophores, nor sperm packets were found inside the seminal receptacle; instead free spermatozoids were observed indicating that sperm from different males is probably mixed favoring sperm competition. The ultrastructure of the male gonopods was similar to the described for other Brachyura. Different types of setae and the presence of internal rosette glands were described and probable functions were suggested.

Estructura del aparato reproductor masculino de Uca uruguayensis (Decapoda, Ocypodidae)

El objetivo de este trabajo es describir las estructuras del sistema reproductor de machos de Uca uruguayensis Nobili, 1901 y estudiar los cambios relacionados con la madurez sexual. Se trabajo con observacion estereoscopica de material fresco, tecnica histologica de rutina y observaciones en Microscopio Electronico de Barrido. Se incluyo la caracterizacion de los gonopodos 1 (G1) y 2 (G2). El tracto reproductor del macho se compone de un par de testiculos (T), un vaso deferente (VD) tubular y sinuoso y una ampolla terminal (AT). El VD tiene tres secciones, la anterior (VDA), la media (VDM) y la posterior (VDP). El VDA y VDM estan conformadas por un epitelio simple de celulas cubicas. El epitelio del VDP es columnar y con nucleos basales y alongados. El diseno tubular se modifica al ocuparse el lumen del VDP con liquido espermatico durante el verano y la musculatura circular se hace mas evidente. La porcion terminal del VDP se ensancha formando una ampolla (AT) que comprende cuatro camaras interconectadas. Todas las estructuras estan rodeadas de una capa de tejido conectivo de poco espesor. Se identifican las modificaciones observadas en la histologia de T y VD, definiendo como mas relevantes las observadas desde el mes de noviembre hasta marzo. Estas modificaciones sugieren que U. uruguayensis tiene, en la localidad estudiada, una unica estacion reproductiva durante el verano en esta latitud. La AT, tal como es descripta, es una estructura que hasta el momento no ha sido mencionada para los Brachyura.

Cytoarchitecture of the Hepatopancreas of Three Species of Crabs from Mar Chiquita Lagoon, Argentina

Based on the various functions of the crustacean hepatopancreas, this work analyzes the possible structural differences in brachyurans from different microhabitats in the Mar Chiquita lagoon “cangrejal” (37° 45′ S, 57° 26′ W). Adult males in intermolt (Stage C) of Uca uruguayensis, Chasmagnathus granulata and Cyrtograpsus angulatus were collected at the same time. The hepatopancreas was removed and processed by using standard histological techniques. The organ completely occupies the dorsal hemocoel in C. granulata and C. angulatus, while it is arranged in two dorsal, lateral masses in U. uruguayensis. The cytoarchitecture of the three species is similar to that observed in other brachyurans. Differences in the tubular structure are related to the presence of a peritrophic lamina in all its extension and a marked differentiation at the medial zone in C. angulatus. The tubular lumen in C angulatus and U. uruguayensis is cross-shaped, though very branched in C. granulata. These characteristics indicate a different rhythm in the cycle of cellular activity. The tubular and cell dimensions are similar for the three species; it is outstanding the augmented intertubular tissue in U. uruguayensis.