Reproductive endocrinology of Syngnathidae

Abstract

Few studies have examined the underlying hormonal mechanisms that mediate reproductive cyclicity, male pregnancy and reproductive behaviour in syngnathids. Progress in these areas has been hampered by the small size of most species in the family and a lack of validated techniques for assessing endocrine function. Research on a relatively small number of species has suggested that androgens are likely regulators of spermatogenesis and the development of the male brood pouch prior to pregnancy whereas prolactin and corticosteroids synergistically promote brood pouch function during pregnancy. No evidence supports a reversal of reproductive steroid hormone function in sex-role reversed behaviour, but neuropeptides such as arginine vasotocin or isotocin should be examined for their role in regulating parturition and mating behaviour. The diversity of reproductive patterns exhibited by syngnathids suggests that they will provide a unique opportunity to assess how hormonal regulation of integumentary function, gametogenesis and reproductive behaviour have evolved within a teleost lineage. Additionally, their coastal distribution and embryo retention make them potentially important subjects for studies on the effect of endocrine disruption on fitness.

Standardised classification of pre-release development in male-brooding pipefish, seahorses, and seadragons (Family Syngnathidae)

“…Given the number of comparative studies on syngnathid reproductive biology (e.g. [18-24]), and in view of the growing scientific interest in these fish, such a standardisation is essential for cross-species comparisons. In the present account, we describe common features in the development of syngnathids, reviewing available data (lit.…”

A multidisciplinary experimental study on the effects of breeders diet on newborn seahorses (Hippocampus guttulatus)

“…photoperiod regime, temperature) (Lin et al, 2006(Lin et al, , 2008bPlanas et al, 2010Planas et al, , 2013, zootechnical conditions (e.g. sex ratio, aquaria design, seahorse size) (Woods et al, 2000;Dzyuba et al, 2006;Planas et al, 2008;Faleiro et al, 2008Faleiro et al, , 2016, and biological / physiological features (Boisseau, 1967;Carcupino et al, 2002;Poortenaar et al, 2004;Stölting and Wilson, 2007;Scobell and MacKenzie, 2011;Zhang et al, 2019; Wittington and Fresien, 2020). Only a few studies have focused on the effects of feeding and dietary sources on breeding success and newborn features in seahorses under ex-situ conditions (Lin et al, 2007;Faleiro and Narciso, 2010;Binh and Serrano, 2012;Saavedra et al, 2015;Palma et al, 2012Palma et al, , 2017Otero-Ferrer et al, 2012.…”

The biology of Syngnathidae: pipefishes, seadragons and seahorses

“…This special issue presents recent progress and concern, as well as future research potential in these fishes. In particular, highlights of syngnathids are provided by reviews on evolutionary origins (Wilson & Orr, 2011), genetics and genomics (Mobley et al , 2011), sexual signals and mating patterns (Rosenqvist & Berglund, 2011), reproductive endocrinology (Scobell & MacKenzie, 2011), and conservation and management (Vincent et al , 2011). In addition, a number of original research papers on many important aspects of the biology of syngnathids are presented.…”

“…Such processes may be of great importance in patterns of sexual conflict in syngnathids (Paczolt & Jones, 2010). Reproductive endocrinology in relation to male pregnancy is also of particular interest, hormones associated with male pregnancy are now more easily analysed (Ripley & Foran, 2010; Scobell & MacKenzie, 2011). The sampling of minute amounts of hormones has improved due to modern analytical techniques.…”

“…Eutrophication is one such common perturbation that affects seagrass to become increasingly overgrown by filamentous algae, and pipefishes have been shown to avoid such habitats (Sundin et al , 2011). Pollutants are also of concern, for instance, as endocrine disrupters in syngnathids (Scobell & MacKenzie, 2011). Changing sea temperatures due to global warming is another concern, both for biodiversity and because temperature is an important factor influencing the brooding times of males and thus their reproductive ecology (Ahnesjö et al , 2008).…”