High-density aggregations of rodlet cells in the gonads of Greenland halibut Reinhardtius hippoglossoides, a deep-water marine flatfish.

Large aggregations of rodlet cells in the gonads of male and female Greenland halibut Reinhardtius hippoglossoides are reported for the first time. These rodlet cells were not arranged epithelially but rather were found throughout the connective tissue between oocytes (females) or within lymphatic spaces between testicular lobules (males). The reason for large aggregations of rodlet cells in the gonads and not other tissues of this species is uncertain.

Automated sperm head morphology analyzer for open-source software.

Sperm head morphology has been identified as a characteristic that can be used to predict a male's semen quality. In the present study, we have developed an automated sperm head morphology analysis (ASMA) plug-in for open-source ImageJ software (http://rsbweb.nih.gov/ij/). We describe the plug-in's functionality, and confirm its validity for sperm head morphology analysis using fish sperm. Sperm head morphological measurements (length and width) made with the ASMA plug-in did not differ from manual measurements. Using the plug-in to measure sperm head-shaped objects of known size, the associated plug-in error rate was < 0.5%. Brightness and contrast ratios influenced sperm head measurements, suggesting the need for standardized protocols. This plug-in was effective at measuring elliptical (i.e., Atlantic cod) as well as slightly irregular (i.e., Chinook salmon) shaped sperm heads. In conclusion, our ASMA plug-in represents a versatile alternative to costly sperm morphology software.

Relationships between maternal body size, condition and potential fecundity of four north-west Atlantic demersal fishes.

Fecundity data for four species (American plaice Hippoglossoides platessoides, yellowtail flounder Limanda ferruginea, witch flounder Glyptocephalus cynoglossus and Atlantic cod Gadus morhua) of north-west Atlantic demersal fishes, corresponding to nine populations, were examined in relation to fish size and condition in an attempt to explain the observed variability in potential fecundity. Both relative body (K(r)) and liver condition (H(r)) were poor single-factor predictors of fecundity, and in almost all cases fish body mass (M) was the best single-factor predictor. Annual variability in mean K(r) and H(r) existed for most populations. The inclusion of K(r) and H(r) in total length (L(T))-based predictive models improved model fit only slightly and not significantly in all cases. Multiple regression analyses to determine the best model for explaining the variability in fecundity often excluded K(r), H(r) and L(T) in favour of M. The amount of variability in fecundity that could be explained by the factors analysed here was species specific, with the highest proportion explained for H. platessoides and the lowest for L. ferruginea. The highly variable, and sometimes unpredictable, nature of north-west Atlantic groundfish fecundity suggests the need to continue collecting such reproductive data on an ongoing basis.