Antonio Ostrensky

Acute toxicity of ammonia to various life stages of the São Paulo shrimp, Penaeus paulensis Pérez-Farfante, 1967

Each life stage of the Sao Paulo shrimp, Penaeus paulensis, was exposed to ammonia in a series of acute toxicity tests, by the semistatic method, at 25 °C and salinity at 28 ppt. A pronounced sensitivity was observed in the egg stage. In this phase, 0.30 mg/l NH3-N caused death of 50% of the embryos. The 24-h LC50 values for nauplii, zoeae, myses and postlarvae were, respectively, 102.30, 22.93, 74.87 and 24. 19 mg/l total ammonia-N (4.25, 1.79, 2.91 and 1.40 mg/l NH3-N). The 96-h LC50 values for zoeae, myses and postlarvae were 9.39, 21.98, 5.49 mg/l total ammonia-N (0.73, 0.85 and 0.32 mg/l NH3-N). The LC50 of ammonia for juveniles (5.45 ± 0.4 g mean live-weight) and for adults (31.43 ± 1.3 g mean live-weight) were also measured. The 24-h LC50 values for juveniles and adults were, respectively, 51.87 and 61.63 mg/l total ammonia-N (1.47 and 1.59 mg/l NH3-N) and the 96-h LC50 values were 38.72 and 42.49 mg/l total ammonia-N (1.10 and 1.06 mg/l NH3-N). An analysis of variance showed that there was no direct relationship between shrimp development and its tolerance to ammonia (P > 0.05) and that eggs, zoeae and postlarvae are very sensitive to ammonia:. The “safe level” for rearing P. paulensis was estimated to be 0.03 mg/l NH3-N. In general, P. paulensis is less resistant to ammonia than other species of shrimp.

Lethargic crab disease: multidisciplinary evidence supports a mycotic etiology

Although lethargic crab disease (LCD) is causing massive mortalities in populations of the mangrove crab Ucides cordatus of Northeastern Brazil, the identity of its etiological agent was hitherto unknown. In this study we provide robust evidence suggesting that LCD is caused by an anamorph Ascomycota (Fungi). We examined specimens of U. cordatus collected from stocks affected by LCD. Histological and TEM methods detected the presence of hyphae, conidia, and condiophores in several host tissues. Moreover, the abundance of fungal stages is negatively associated with crab health. Finally, DNA was isolated from the fungus and a region of its 18S ribosomal gene was sequenced Phylogenetic analyses not only confirm the diagnosis of the LCD fungus in crab tissues as an ascomycete, but also suggest a close relationship with members of the subphylum Pezizomycotina.

Postglacial north–south expansion of populations of Rhizophora mangle (Rhizophoraceae) along the Brazilian coast revealed by microsatellite analysis

PREMISE OF THE STUDY Red mangrove (Rhizophora mangle) dominates tropical tidal areas along both sides of the Atlantic, yet little is known about its degree of population differentiation over large geographical scales. Information on the genetic variability of mangrove species along the Brazilian coast is important not only for understanding the recent gene flow dynamic between populations, but also to evaluate models of evolutionary diversification and develop effective strategies for conservation. We investigated the genetic variability of the red mangrove along the Brazilian coast. METHODS Eight microsatellite loci were used to genotype 145 individuals across 10 populations spanning more than 4500 km of coast line. We estimated the genetic variability and structure of the populations and the historical gene flow between them. KEY RESULTS The level of genetic variability was low, with only 27 different alleles being detected and allele richness between 1.25 and 2.75. On the other hand, there was substantial population differentiation (R(st) = 0.48; P < 0.001), especially between the northern and southern populations. The populations from Pará and Maranhão had significantly greater genetic variability than did the remaining locations. CONCLUSIONS This difference might reflect the older age of the northern mangroves, which likely remained stable during the Quaternary glaciations. The lowest variability observed in the southern populations of the red mangrove most likely reflects their recent age, associated with allelic reduction, resulting from the consecutive founder events that followed subsequent colonization of estuaries during the gradual warming by the end of the last glacial period.

Black yeast-like fungi associated with Lethargic Crab Disease (LCD) in the mangrove-land crab, Ucides cordatus (Ocypodidae)

Lethargic Crab Disease (LCD) caused extensive epizootic mortality of the mangrove land crab Ucides cordatus (Brachyura: Ocypodidae) along the Brazilian coast, mainly in the Northeastern region. The disease was named after the symptoms of slow movement of infected crabs. Causative agents were suspected to be two black yeast-like fungi of the family Herpotrichiellaceae (ascomycete order Chaetothyriales), judged by infected tissue biopsies from moribund U. cordatus. The aim of the present study is to prove that two species are involved in the disease: the recently described black yeast Exophiala cancerae, but also a less virulent, hitherto undescribed fonsecaea-like species, introduced here as the novel species Fonsecaea brasiliensis. Strains were identified by ITS rDNA sequencing, and species borderlines were established by multilocus sequencing and AFLP analysis. Fonsecaea brasiliensis proved to be closely related to the pathogenic species Cladophialophora devriesii which originally was isolated from a systemic infection in a human patient. The virulence of F. brasiliensis is lower than that of E. cancerae, as established by artificial inoculation of mangrove crabs.

Occurrence of an alternative pathway in the larval development of the crab Chasmagnathus granulata Dana, 1851 under laboratory conditions

Larvae of the crab Chasmagnathus granulata were collected in a salt marsh located in the Lagoa dos Patos, Brazil and reared from eclosion to metamorphosis under different dietary regimes. Larvae reared individually in beakers of 40 ml and fed Tetraselmis chuii (zoea III and zoea IV), showed a supplementary stage, here designated as zoea V, with morphological characteristics intermediary between zoea IV and megalopa. No zoeae V molted to megalopa stage. To confirm the occurrence of the supplementary stage, mass cultures of larvae of C. granulata were fed Artemia sp. at high densities, we again detected the fifth zoeal instar. However, when zoeae V were individually placed in beakers and fed Artemia nauplii, they succeeded in molting into megalopae. We observed the occurrence of two types of zoeae IV — a smaller type (from which originated the zoeae V) and a larger type (which directly developed into megalopae). We conclude that stressful nutritional/environmental conditions were responsible for the occurrence of this alternative path of development.

Genetic structure of populations of the mangrove crab Ucides cordatus (Decapoda: Ocypodidae) at local and regional scales

The crab Ucides cordatus (Decapoda: Ocypodidae) is a species of considerable economic and ecological importance in mangrove areas of the Western Atlantic coast. However, habitat loss, overfishing, and a new infectious disease are causing substantial reductions in local stocks of this species, leading to a pressing need to design efficient management strategies. A crucial step in this design in an understanding of how the genetic variability of U. cordatus is distributed among estuaries throughout its range. In this study we assess the degree of spatial structure in the pattern of genetic variation of U. cordatus over local (estuaries located within 100 km from each other) and geographical scales (estuaries located farther than 2700 km from each other). Ninety individuals were collected from nine estuaries and analyzed using PCR-RFLP and RAPD techniques. The percentage of polymorphic bands within populations ranged from 15% to 46% for RFLP markers and from 40% to 70% for RAPD markers. Our results failed to demonstrate significant geographical structure in the pattern of genetic variation, indicating that populations of U. cordatus are capable of extensive gene flow among estuaries. The implications of these results for the management of U. cordatus populations are discussed.

The effect of temperature and body size on filtration rates of Limnoperna fortunei (Bivalvia, Mytilidae) under laboratory conditions.

The golden mussel (Limnoperna fortunei, Mollusca: Bivalvia) is an invasive species that has been causing considerable environmental and economic problems in South America. In the present study, filtration rates of L. fortunei were determined in the laboratory under different temperatures (10, 15, 20, 25, 28, and 30 oC) and two types of food (Algamac-2000® and the chlorophycean alga Scenedesmus sp.). There was a statistically significant relationship between time and filtration rates in the experiment using Scenedesmus sp., regardless of temperature. However, this pattern was absent in the experiment using Algamac, suggesting that the relationship between filtration rates and temperature might depend on the size of the filtered particles. In addition, there was no correlation between filtration rates and either shell size or condition index (the relationship between the weight and the length of a mussel). The filtration rate measured in the present study (724.94 ml/h) was one of the highest rates recorded among invasive bivalves to date. Given that the colonies of the golden mussel could reach hundreds of thousands of individuals per square meter, such filtration levels could severely impact the freshwater environments in its introduced range.

The Organization of the Mitochondrial Control Region in 2 Brachyuran Crustaceans: Ucides cordatus (Ocypodidae) and Cardisoma guanhumi (Gecarcinidae)

The control region (CR) is the largest noncoding segment of the mitochondrial DNA and includes the major regulatory elements for its replication and expression. In addition, the high level of intraspecific genetic variability found in the CR favors its use in phylogeographical and population genetic studies of a variety of organisms. However, most of the work on the structure of the CR has focused on vertebrates and insects, and little is known about the evolution of the CR in other taxa. In this study, we sequenced the entire CR of several individuals of 2 crab species: Ucides cordatus (Ocypodidae) and Cardisoma guanhumi (Gecarcinidae). There were neither large conserved regions in the CR of either species nor any similarity among species at the nucleotide level. However, the spatial pattern of genetic variability on the CR was similar among species. In addition, interesting similarities were found in the formation of stable secondary structures and in the position of regulatory elements. These results indicate that the evolution of CR in crustaceans is a remarkably dynamic process, with most homology among species being found at the secondary level.

Genetic evidence for multiple paternity in the mangrove land crab Ucides cordatus (Decapoda: Ocypodidae)

Abstract Studies on mating patterns of marine crustaceans are rare, but the few studies on brachyuran crabs to date suggest that polyandrous mating is uncommon. In the present study, we used 6 microsatellite loci to genotype 8–16 larvae obtained from each of 10 gravid females of the crab Ucides cordatus (Brachyura: Ocypodidae). Based on the number of non-maternal alleles detected among the offspring, at least 40% of the females were inseminated by more than one male. We suggest forced copulation and maintenance of sperm in spermathecae throughout the year as possible causes of polyandry in U. cordatus.

Molecular data reveal a diverse Astyanax species complex in the upper Iguaçu River

Astyanax is among the most speciose genera in the Characidae. In this study, molecular markers were used to assess the extent to which some of the commonly recognized Astyanax species of the upper Iguaçu River correspond to natural groups. These results indicate that the diversity of Astyanax has been severely underestimated with several potential cryptic species.