André Braga

Unistellate spermatozoa of decapods: comparative evaluation and evolution of the morphology

Decapod unistellate spermatozoa are primarily characterized by the presence of a single appendage (spike) extending from the acrosome. Among decapods, this type of spermatozoon is found only in shrimps of the families Sicyoniidae, Penaeidae, and Solenoceridae (suborder Dendrobranchiata) and of the infraorder Caridea (suborder Pleocyemata). This review comparatively discusses the morphological diversity of unistellate spermatozoal ultrastructure among these decapods, as well as the role of the primary structures involved in the fertilization and spermatozoal capacitation. Furthermore, the use of the unistellate spermatozoal ultrastructure to support phylogenetic relationships and of the current phylogenetic evidences to investigate the evolution of spermatozoa of decapods is discussed. Morphologically, the main differences between caridean and dendrobranchiate unistellate spermatozoa are the shape of the main body (inverted cup-shaped, and spherical, bulged or elongate, respectively) and complexity of the acrosomal region. The latter is directly related to the type of fertilization. For example, dendrobranchiates have more complex acrosomal regions than that carideans, and fertilization involves a visible acrosome reaction, which is not observed in carideans. Ultrastructural changes of spermatozoa throughout capacitation are unknown in carideans, but for dendrobranchiates generally occur in the acrosomal vesicle and subacrosomal region throughout attachment of the spermatophore to the thelycum, enabling fertilization by the spermatozoa. Comparative evaluation of spermatozoal morphology and current phylogenetic evidences corroborates the hypothesis that the spermatozoal spike of carideans and dendrobranchiates is the result of convergent evolution.

A Comparison of the Reproductive Performance of the Wild Pink Shrimp Species Farfantepenaeus paulensis and Farfantepenaeus brasiliensis in Captivity

ABSTRACT The aim of this study was to compare the reproductive performance of the wild shrimp species Farfantepenaeus paulensis and Farfantepenaeus brasiliensis in captivity. The broodstocks were collected in offshore waters in Santa Catarina and transferred to the Marine Station of Aquaculture of the Federal University of Rio Grande. Broodstocks with a similar body weight between the two species were selected to measure reproductive performance. Females with mature ovaries were identified each day to obtain measures of reproductive performance. After spawning, fertilization rates were determined by microscopic examination. In addition, three samples of 100 eggs were collected to determine hatching rates, and three samples of 100 nauplii were collected to evaluate the rate of metamorphosis to protozoa. For males, spermatophores were manually extruded, weighed, and homogenized in 2 mL calcium-free saline solution, and 0.1 mL trypan blue was added. Sperm counts, abnormal cells (malformations of the main body or absence of the spike), and dead cells (blue coloration) were estimated with cell counts, using a hemacytometer under a light microscope. Spermatophore melanization was checked. The larval production of the two species was similar, but F. brasiliensis spawned in less time after unilateral eyestalk ablation. The spermatophore weight and sperm count were higher in the F. brasiliensis males, and none of the shrimp showed melanization.

Contribution of bioflocs to the culture of Litopenaeus vannamei post-larvae determined using stable isotopes

The aim of this study was to use preselected quality indicators for Litopenaeus vannamei post-larvae and the stable isotopes technique with δ13C and δ15N to determine the influence of bioflocs in shrimp feeding during the nursery phase, between PL1 and PL30. A control treatment (CT) with water renewal was compared to a biofloc treatment (BT) that received organic carbon fertilizations. Different types of commercial feed (Stresspak and Flake-INVE™, PL40-GUABI™), microalgae (Chaetoceros muelleri) and Artemia sp. nauplii were used as food sources. The physical and chemical parameters of water and ammonia were monitored daily, and nitrite, nitrate and alkalinity were measured weekly. Suspended solids and the microorganisms of bioflocs were characterized. At the end of the experiment, fifteen shrimps of each replicate were collected to evaluate nine larvae quality indicators. Isotopic values of 13C and 15N of food sources and shrimp tissues were collected on days 10, 20 and 30, and a Bayesian model of isotopic mixture measured the contributions of these sources to the shrimp biomass. Salinity, alkalinity and nitrite differed significantly between the treatments but were appropriate for post-larvae production. The larvae quality conditions in the CT treatment were ranked as “good,” whereas the BT conditions were considered “excellent” according to the analysis of larval quality parameters. The stable isotopes analysis showed that the PL40 GUABI™ feed was the most important food source throughout the experimental period in the CT. In the BT (10th and 20th days), the bioflocs and commercial feeds (Flake-INVE™, PL40-GUABI™) did not present significant variations in their contribution ratios; however, on the 30th day, the contribution of the PL40-GUABI™ feed was higher when compared to bioflocs. In general, the commercial feed played a more important role as a food source for Litopenaeusvannamei larvae during the nursery phase, although the consumption of bioflocs led to a better larvae quality.