Male pregnancy in seahorses and pipefish: beyond the mammalian model

Pregnancy has been traditionally defined as the period during which developing embryos are incubated in the body after egg-sperm union. Despite strong similarities between viviparity in mammals and other vertebrate groups, researchers have historically been reluctant to use the term pregnancy for non-mammals in recognition of the highly developed form of viviparity in eutherians. Syngnathid fishes (seahorses and pipefishes) have a unique reproductive system, where the male incubates developing embryos in a specialized brooding structure in which they are aerated, osmoregulated, protected and likely provisioned during their development. Recent insights into physiological, morphological and genetic changes associated with syngnathid reproduction provide compelling evidence that male incubation in these species is a highly specialized form of reproduction akin to other forms of viviparity. Here, we review these recent advances, highlighting similarities and differences between seahorse and mammalian pregnancy. Understanding the changes associated with the parallel evolution of male pregnancy in the two major syngnathid lineages will help to identify key innovations that facilitated the development of this unique form of reproduction and, through comparison with other forms of live bearing, may allow the identification of a common set of characteristics shared by all viviparous organisms.     

Male pregnancy and the evolution of body segmentation in seahorses and pipefishes

The evolution of complex traits, which are specified by the interplay of multiple genetic loci and environmental effects, is a topic of central importance in evolutionary biology. Here, we show that body and tail vertebral numbers in fishes of the pipefish and seahorse family (Syngnathidae) can serve as a model for studies of quantitative trait evolution. A quantitative genetic analysis of body and tail vertebrae from field-collected families of the Gulf pipefish, Syngnathus scovelli, shows that both traits exhibit significantly positive additive genetic variance, with heritabilities of 0.75 +/- 0.13 (mean +/- standard error) and 0.46 +/- 0.18, respectively. We do not find any evidence for either phenotypic or genetic correlations between the two traits. Pipefish are characterized by male pregnancy, and phylogenetic consideration of body proportions suggests that the position of eggs on the pregnant male's body may have contributed to the evolution of vertebral counts. In terms of numbers of vertebrae, tail-brooding males have longer tails for a given trunk size than do trunk-brooding males. Overall, these results suggest that vertebral counts in pipefish are heritable traits, capable of a response to selection, and they may have experienced an interesting history of selection due to the phenomenon of male pregnancy. Given that these traits vary among populations within species as well as among species, they appear to provide an excellent model for further research on complex trait evolution. Body segmentation may thus afford excellent opportunities for comparative study of homologous complex traits among disparate vertebrate taxa.     

Male copulatory behavior triggers nightly prolactin surges resulting in successful pregnancy in rats

A positive correlation between the number of preejaculatory intromissions that a female receives during copulation and the probability of successful pregnancy has been demonstrated previously. In the present investigation the nocturnal secretion of prolactin (PRL) was followed for 4 days after mating in female rats receiving either 3–5 intromissions before ejaculation (low intromission group) or 15–18 intromissions (high intromission group). Nightly PRL surges occurred in most of the females (9/12) in the high intromission group and the same 9 females became pregnant. Only 2/9 females in the low intromission group exhibited nightly PRL surges and again only these 2 females became pregnant. This study demonstrates that the stimulation which the female receives from multiple intromissions during mating is effective in setting off nightly PRL surges. We propose that the so-called pregnancy-inducing neuroendocrine reflex which is triggered in this manner is expressed in a characteristic pattern of nightly surges of prolactin, the hormone known to be essential for the activation of the corpora lutea and their secretion of progesterone.     

Male pseudohermaphroditism related to complications at conception, in early pregnancy or in prenatal growth.

We examined whether male pseudohermaphroditism, when unexplained, is associated with reduced prenatal growth. Birth weight SD scores of 29 children with male pseudohermaphroditism were compared. The scores of children with an unexplained condition (median -2.1 SD) were found to be lower (p = 0.0001) than those of children with an explained condition (median -0.4 SD). In the majority of cases of unexplained male pseudohermaphroditism, there was a complicated history before conception or in early pregnancy. In conclusion, hitherto unexplained male pseudohermaphroditism was found to be associated with reduced prenatal growth and complications at conception or in early pregnancy.     

Male rhinoplasty

Rhinoplasty is one of the most complex and challenging operations in plastic surgery. This complexity is increased among male patients, because male patients tend to have relatively nonspecific complaints, are typically more demanding, and are regarded as being much less attentive during consultations. It is critical for the surgeon to verify that the male patient has realistic goals before he undergoes an operation, and the surgeon must confirm that the male patient has heard and understood all of the risks, benefits, and options. It is essential that masculine features be preserved for male rhinoplasty patients. Excessive dorsal reduction or tip refinement produces unsatisfactory results. A comprehensive discussion of proper evaluation of the male nose, surgical planning, intraoperative techniques, and postoperative treatment is presented. These tools should allow plastic surgeons to produce a balanced harmonious nose in relation to the rest of the face.