Spatial asymmetry of the paternity success in nests of a fish with alternative reproductive tactics.

Guard-sneaker tactics are widespread among fish, where territorial males defend a nest and provide parental care while sneakers try to steal fertilizations. Territorials and sneakers adopt diverse pre- and post-mating strategies, adjusting their ejaculate investment and/or behavioural responses to the presence of competitors. The relative distance of competitors from the spawning female plays a major role in influencing male mating strategies and the resulting paternity share. However, territorial male quality and sneaking intensity do not fully account for the variability in the relative siring success occurring among species. An often neglected factor potentially affecting sneakers proximity to females is the nest structure. We conducted a field experiment using the black goby, whose nests show two openings of different size. We found that territorial males defend more and sneaking pressure is higher at the front, larger access of the nest than at the back, smaller one. Moreover, microsatellite paternity analysis shows that territorials sire more offspring at the back of their nest. Such a predictable spatial distribution of the paternity share suggests that nest structure might work as an indirect cue of male relative siring success, potentially influencing the territorial male investment in parental care and/or the female egg deposition strategy.

Unexpected female preference for smaller males in the marbled goby Pomatoschistus marmoratus.

The study tested the role of body size and of nest size in female mate choice in the marbled goby, Pomatoschistus marmoratus. The results show a female preference for smaller males, supporting the idea that smaller males may be preferred to larger ones in the absence of male-male competition. No effect of nest size was detected, suggesting that other nest characteristics, beyond nest size, may be implicated.

An insight into the reproductive biology of the bearded goby Sufflogobius bibarbatus.

Preliminary results obtained from histological analyses of the male reproductive organs, supplemented with field and behavioural data, indicate that Sufflogobius bibarbatus, a small, slow growing gobiid exhibiting low fecundity, which plays an important role in the food web off Namibia, where large areas of the shelf are hypoxic, spawns demersally. Large males defend benthic nests, possibly at the edge of the hypoxic shelf. Male reproductive strategy appears to be flexible, and tentative evidence to suggest that polygyny and sneaking may also occur is presented.

Colourful male guppies produce faster and more viable sperm.

In guppies (Poecilia reticulata) precopulatory sexual selection (via female choice) and post-copulatory selection (via sperm competition) both favour males with relatively high levels of carotenoid (orange) pigmentation, suggesting that colourful males produce more competitive ejaculates. Here we test whether there is a positive association between male orange pigmentation and sperm quality. Our analysis of sperm quality focused on sperm swimming speeds (using CASA: computer-assisted sperm analysis to estimate three parameters of sperm velocity in vitro), sperm viability (proportion of live sperm per stripped ejaculate) and sperm lengths. We found that males with relatively large areas of orange pigmentation had significantly faster and more viable sperm than their less ornamented counterparts, suggesting a possible link between dietary carotenoid intake and sperm quality. By contrast, we found no relationship between sperm length (head length and total sperm length) and male phenotype. These findings, in conjunction with previous work showing that highly ornamented male guppies sire higher quality offspring, suggest that female preference for colourful males and sperm competition work in concert to favour intrinsically higher quality males.

Ejaculate of sneaker males is pheromonally inconspicuous in the black goby, Gobius niger (Teleostei, Gobiidae).

The black goby, Gobius niger, shows alternative male mating tactics, i.e., parental and sneaker males. Males release a sexual pheromone that attracts females and stimulates aggressive displays in males. This pheromone is produced by the mesorchial gland, a structure well developed in parental males but markedly undeveloped in sneakers. We measured the behavioral response of parental males to the ejaculates of males performing different reproductive tactics. Parental males reacted to the ejaculate of other parental males, with stereotypic aggressive behaviors, but not to the ejaculate of sneakers; consequently sneaker male ejaculate appears to be pheromonally inconspicuous.

Intercellular communication in the eight-cell stage of Xenopus laevis development: a study using dye coupling.

We report an investigation of dye coupling in the eight-cell stage of Xenopus laevis development. Our results indicate that fluorophors injected into micrometers at this stage pass only to sister cells (the corresponding macromeres) and that detectable dye transfer occurs only via cytoplasmic bridges, which persist for about the first two-thirds of the fourth cell cycle. We had previously shown that the dorsoventral polarity of the Xenopus embryo is regulated by a cell interaction that occurs at the end of the fourth cell cycle and we conclude that this cell interaction probably does not require cytoplasmic bridges or gap junctions.

Globin evolution in some species of the genus Bufo.

The globins of 10 species of toads of the genus Bufo have been analysed. From the values of the reciprocal rates between their amino acid residues a 'dissimilarity matrix' was made. In this have been included the values related to Discoglossus pictus and Xenopus laevis. The numerical data, derived from a computer program, gave a dendrogram representing the evolution of the analysed globins. This appears correlated to the geographical distribution and to the metabolic adaptation of the corresponding species of Bufo more than their chronological appearance.