Publications & Contributions

A comprehensive database of Project Seahorse outputs

Operational sex ratios and behavioral sex differences in a pipefish population

In the pipefish Syngnathus typhle, only males brood embryos in specially developed brood pouches, supplying oxygen and nutrients. Laboratory studies have shown that this elaborate paternal care has led to sex-role reversal in this species: males limit female reproductive rate, females are the primary competitors for mates and males exercise greater selectivity in accepting mates. In …

Operational sex ratios in seahorses

Contrary to all expectations based on their male pregnancy, recent work shows that seahorses exhibit conventional sex roles in mating competition: male seahorses compete more to obtain eggs than females do to give their eggs away. This suggests that the operational sex ratio (OSR: the relative number of males and females available to mate) might …

Seahorses exhibit conventional sex roles in mating competition, despite male pregnancy

In seahorses, only males undergo a pregnancy. It had been tacitly and explicitly assumed that seahorses were sex role reversed (that females competed more intensely than males for access to mates), on the basis that male pregnancy so limited male reproduction as to produce a female-biased operational sex ratio (OSR). However, this supposition had never …

The role of females in influencing mating patterns

Adaptive arguments about mating patterns should focus on and evaluate the costs and benefits relating to both female and male mating patterns. To date, most work on mating systems (using prevalent terminology) has concentrated on males, with mating systems categorized as to whether males mate with females once or multiply, sequentially or simulataneously (EMlen and …

Pipefishes and seahorses: Are they all sex role reversed?

The male pregnancy of pipefishes and seahorses has led to the inference that females compete most intensely for access to mates, because males limit female reproduction. However, recent work has shown that in different species either sex may be the predominant competitor for mates. In this family, there is an apparent association between the mating …

Pipefishes and seahorses: are they all sex role reversed?

The male pregnancy of pipefishes and seahorses has led to the inference that females compete most intensely for access to mates, because males limit female reproduction. However, recent work has shown that in different species either sex may be the predominant competitor for mates. In this family, there is an apparent association between the mating …

Sexual selection and the potential reproductive rates of males and females

PRONOUNCED sex differences in mating competition are a prominent feature of many animal breeding systems. These differences are widely attributed to sex differences in parental investment1,2which bias the ratio of sexually receptive females to males3 (the operational sex ratio), generating more intense competition between members of one sex, usually males3–5. Unfortunately, relative parental investment1 is usually impossible …

Reproductive ecology of seahorses

Seahorses provide an ideal opportunity to test our understanding of the evolution of sex differences because of their unique specialization for parental care. Male seahorses undergo a lengthy “pregnancy” during which developing embryos are aerated, osmoregulated and nourished in an abdominal pouch, while females provide no care. In most animals, females limit male reproductive rate …

Pregnant males & horses’ tales

Seahorses have long been held to have magical properties. In ancient Greece, fishermen who found seahorses washed ashore believed these were the young of the giant stallions that pulled Neptune’s chariots across the waves. The Roman natural historian Pliny stated that ashes of seahorse mixed with tallow and oil of marjoram, and applied to the …