Reproductive biology of the nonnative oyster, Crassostrea gigas (Thunber, 1793) as a key for its successful spread along the rocky shores of Northern Patagonia, Argentina

Crassostrea gigas was introduced in Anegada Bay (North Patagonia, Argentina), in 1981 for aquaculture purposes. The species has, since established in the field, covered all available hard substrata in the bay and gradually expanded south along the coast of the neighboring province of Río Negro, 90 km away from its original introduction site. Our work focused on the reproductive dynamics of the species at the introduction site, with emphasis on the thermal thresholds needed for each stage of gonad development. During early spring, the oysters in Anegada Bay go through active gonad proliferation. Maturity extends mainly from October to January. The first spawning occurs in November, when seawater temperature exceeds 17°C, and peaks from December to February, when seawater temperature lies in the range ot 19–21.5°C. The timing of gonad development is size dependent. Larger (≥70 mm) and medium-size oysters begin spawning first, whereas small oysters ( 17°C), and spawning only occurs in those sites where this threshold is reached.Versión del editor

Gametogenesis in the Pacific Oyster Crassostrea gigas: A Microarrays-Based Analysis Identifies Sex and Stage Specific Genes

Background: The Pacific oyster Crassostrea gigas (Mollusca, Lophotrochozoa) is an alternative and irregular protandrous hermaphrodite: most individuals mature first as males and then change sex several times. Little is known about genetic and phenotypic basis of sex differentiation in oysters, and little more about the molecular pathways regulating reproduction. We have recently developed and validated a microarray containing 31,918 oligomers (Dheilly et al., 2011) representing the oyster transcriptome. The application of this microarray to the study of mollusk gametogenesis should provide a better understanding of the key factors involved in sex differentiation and the regulation of oyster reproduction. Methodology/Principal Findings: Gene expression was studied in gonads of oysters cultured over a yearly reproductive cycle. Principal component analysis and hierarchical clustering showed a significant divergence in gene expression patterns of males and females coinciding with the start of gonial mitosis. ANOVA analysis of the data revealed 2,482 genes differentially expressed during the course of males and/or females gametogenesis. The expression of 434 genes could be localized in either germ cells or somatic cells of the gonad by comparing the transcriptome of female gonads to the transcriptome of stripped oocytes and somatic tissues. Analysis of the annotated genes revealed conserved molecular mechanisms between mollusks and mammals: genes involved in chromatin condensation, DNA replication and repair, mitosis and meiosis regulation, transcription, translation and apoptosis were expressed in both male and female gonads. Most interestingly, early expressed male-specific genes included bindin and a dpy-30 homolog and female-specific genes included foxL2, nanos homolog 3, a pancreatic lipase related protein, cd63 and vitellogenin. Further functional analyses are now required in order to investigate their role in sex differentiation in oysters. Conclusions/Significance: This study allowed us to identify potential markers of early sex differentiation in the oyster C. gigas, an alternative hermaphrodite mollusk. We also provided new highly valuable information on genes specifically expressed by mature spermatozoids and mature oocytes

Helminth Community of the Black Margate Anisotremus surinamensis (Teleostei: Haemulidae), from Coral Reefs off the Veracruz Coast, Mexico, Southern Gulf of Mexico

We describe the composition and structure of the helminth community of the black margate Anisotremus surinamensis in coral reefs from the Parque Nacional Sistema Arrecifal Veracruzano (PNSAV) off the Veracruz coast. We examined a total of 78 specimens (total length TL range 21.7–77.9, mean 33.7 cm) (28 males, TL range 22.5–51.5, mean 32.7 cm; 50 females, TL range 21.7–77.9, mean 34.3 cm) of A. surinamensis. At least nine helminth taxa (seven intestinal) were found, for all of which A. surinamensis is a new host. Our inventory includes two new geographic records for the southern Gulf of Mexico: the digeneans Cainocreadium oscitans (Linton, 1910) and Infundiburictus longovatus (Hopkins, 1941). Observed component community richness (S = 9) and infracommunity richness (mean ± SD, S = 2.8 ± 1.3) for A. surinamensis were lower than previously recorded richness for the sympatric A. virginicus and other coral reef fishes from the PNSAV. Numerically dominant taxa were trematodes (four taxa) and monogeneans (two), followed by nematodes (one), acanthocephalans (and) and cestodes (one). The trematode Monorchis latus was the more prevalent, more abundant and numerically dominant helminth species in the community of parasites of A. surinamensis

Helminth Community of the Black Margate <i>Anisotremus surinamensis</i> (Teleostei: Haemulidae), from Coral Reefs off the Veracruz Coast, Mexico, Southern Gulf of Mexico

We describe the composition and structure of the helminth community of the black margate Anisotremus surinamensis in coral reefs from the Parque Nacional Sistema Arrecifal Veracruzano (PNSAV) off the Veracruz coast. We examined a total of 78 specimens (total length TL range 21.7–77.9, mean 33.7 cm) (28 males, TL range 22.5–51.5, mean 32.7 cm; 50 females, TL range 21.7–77.9, mean 34.3 cm) of A. surinamensis. At least nine helminth taxa (seven intestinal) were found, for all of which A. surinamensis is a new host. Our inventory includes two new geographic records for the southern Gulf of Mexico: the digeneans Cainocreadium oscitans (Linton, 1910) and Infundiburictus longovatus (Hopkins, 1941). Observed component community richness (S = 9) and infracommunity richness (mean ± SD, S = 2.8 ± 1.3) for A. surinamensis were lower than previously recorded richness for the sympatric A. virginicus and other coral reef fishes from the PNSAV. Numerically dominant taxa were trematodes (four taxa) and monogeneans (two), followed by nematodes (one), acanthocephalans (and) and cestodes (one). The trematode Monorchis latus was the more prevalent, more abundant and numerically dominant helminth species in the community of parasites of A. surinamensis

Parasitic helminths infecting <i>Eucinostomus melanopterus</i> and <i>Eugerres plumieri</i> (Perciformes: Gerreidae), from Boca del Rio, Veracruz, México

A helminthological examination was carried out on 14 specimens of Eucinostomus melanopterus (flagfin mojarra) and 19 Eugerres plumieri (striped mojarra), of which a total of 461 helminths were collected. As a result, and 12 taxa were registered (five species, five genus and tow family), as follows: four monogeneans, five digeneans (four adults, one metacercaria), one cestode (larva) and tow nematodes (larvae). The highest prevalence was for Neodiplectanum mexicanum (29 %) infecting E. melanopterus and Aristocleidus hastatus (37 %) infecting E. plumieri. Both hosts shared 50 % of recorded species, and none of the identified helminthes represents a zoonotic risk