Editing Seahorse (section)

===Reproductive roles===
[[File:Diagram of a pregnant male seahorse.png|thumb|left| Diagram of a pregnant male seahorse (''[[Hippocampus comes]]'')<ref name=nature20595/>]]
[[File:Tehotny morsky konik.jpg|thumb|right|Pregnant male seahorse at the [[New York Aquarium]]]]

Reproduction is energetically costly to the male. This brings into question why the sexual role reversal even takes place. In an environment where one partner incurs more energy costs than the other, [[Bateman's principle]] suggests that the lesser contributor takes the role of the aggressor. Male seahorses are more aggressive and sometimes fight for female attention. According to [[Amanda Vincent]] of [[Project Seahorse]], only males tail-wrestle and snap their heads at each other. This discovery prompted further study of energy costs. To estimate the female's direct contribution, researchers chemically analyzed the energy stored in each egg. To measure the burden on the males, oxygen consumption was used. By the end of incubation, the male consumed almost 33% more oxygen than before mating. The study concluded that the female's energy expenditure while generating eggs is twice that of males during incubation, confirming the standard hypothesis.<ref name="autogenerated2" />

Why the male seahorse (and other members of the Syngnathidae) carries the offspring through gestation is unknown, though some researchers believe it allows for shorter birthing intervals, in turn resulting in more offspring.<ref>{{cite journal |title=Operational Sex Ratios in Seahorses |author=Vincent, Amanda C. J. |journal=Behaviour |volume=128 |issue=1/2 |year=1994 |pages=153–167 |jstor=4535169 |doi=10.1163/156853994X00091}}</ref> Given an unlimited number of ready and willing partners, males have the potential to produce 17% more offspring than females in a breeding season. Also, females have "time-outs" from the reproductive cycle 1.2 times longer than those of males. This seems to be based on mate choice, rather than physiology. When the female's eggs are ready, she must lay them in a few hours or eject them into the water column. Making eggs is a huge cost to her physically, since they amount to about a third of her body weight. To protect against losing a clutch, the female demands a long courtship. The daily greetings help to cement the bond between the pair.<ref>{{cite web |url=http://petseahorse.com/male-seahorses-pregnant/ |archive-url=https://archive.today/20130717075359/http://petseahorse.com/male-seahorses-pregnant/ |url-status=usurped |archive-date=17 July 2013 |title=Why Do Male Seahorses Get Pregnant? |publisher=Petseahorse.com }}</ref>