Comparing five species of pipefish, egg size was significantly larger in species with brood pouches ( Syngnathus typhle , Syngnathus acus and Syngnathus rostellatus ) than in species without brood pouches ( Entelurus aequoreus and Nerophis ophidion ). Egg size correlated positively with female body size in species with brood pouches, but was similar across female sizes in the species lacking pouches. These results may reflect...

In two experiments, radioactively labelled nutrients (either 3 H‐labelled amino‐acid mixture or 14 C‐labelled glucose) were tube‐fed to brooding male Syngnathus typhle . Both nutrients were taken up by the males and radioactivity generally increased in the brood pouch tissue with time. Furthermore, a low but significant increase of 3 H‐labelled amino acids in embryos was found over the experimental interval (48 h), whereas in...

This study of the sand goby Pomatoschistus minutus , a nest‐holding fish with paternal care, focused on gonadal investment among males of different sizes collected early and late in the breeding season. All males caught at the nest had breeding colour, whereas trawl‐caught fish consisted of males both with and without colour. The absence or presence of breeding colour was a good predictor of testes investment. Compared to male...

Nerophis ophidion sperm activation and morphology were investigated with the aim of explaining the apparent lack of sperm competition in this syngnathid with externally brooding males. Nerophis ophidion sperm were activated by a mixture of ovarian fluid and sea water, but not by sea water alone. This indicated that sperm were not shed into the water but needed to be released near the eggs, which probably restrained sperm compe...

Intensely displaying sand goby Pomatoschistus minutus males had lower lipid content, indicating that signalling increased energy expenditure, or that low condition males increased their signalling effort. Display intensity correlated positively with nest‐defence and tended to correlate positively with filial cannibalism.

One can predict fish species that spawn externally to have larger testes for their body size than internal fertilizers, to produce greater numbers of sperm as a response either to increased risk of sperm competition from sneaker males, or to counter the dilution of sperm in open water. Using museum specimen, we measured testis and body mass of 95 mature males, belonging to 21 genera of the family Syngnathidae (pipefishes and s...

Molecular markers have proved extremely useful in resolving mating patterns within individual populations of a number of species, but little is known about how genetic mating systems might vary geographically within a species. Here we use microsatellite markers to compare patterns of sneaked fertilization and mating success in two populations of sand goby ( Pomatoschistus minutus ) that differ dramatically with respect to nest...

Four polymorphic microsatellite loci were used to assess biological parentage of 453 offspring from 15 pregnant males from a natural population of the Western Australian seahorse Hippocampus angustus . Microsatellite genotypes in the progeny arrays were consistent with a monogamous mating system in which both females and males had a single mate during a male brooding period. Multilocus genotypes implicated four females in the...