Sexual selection in the sea

Jun 04, 2013
The species can grow up to four centimeters in length and are found around the Spencer Gulf in Southern Australia, with healthy populations in Port Phillip Bay. Credit: Benjamin Wegener, Monash University

Biologists have uncovered new insights into how the male sexual behaviour of the peculiar southern bottletail squid is primed to produce the greatest number of offspring.

Recent studies published in the journals Biology Letters and Behavioral Ecology, have revealed the female ingest the ejaculates of their mates, a trait never before associated with any species of cephalopod – a group including squid, , and .

The studies, led by PhD student Benjamin Wegener and Dr Bob Wong from Monash University's School of , in collaboration with researchers at Melbourne University and Museum Victoria, revealed females used the nutrients from this consumption to aid in the growth of her unfertilized eggs.

This appeared to have implications for how males invest in mating opportunities, particularly as smaller females were found to ingest more of the male's ejaculate than larger females.

Mr Wegener said this could explain why males preferred to mate with larger females in an attempt to minimise ejaculate consumption and better their chances for egg fertilization.

"These squid live for just a year and have only a single breeding season before they die, so it's not surprising that the males can be highly strategic when evaluating potential mates," Mr Wegener said.

"The findings suggest that males who copulate with smaller females could pay a higher price for their ejaculate expenditure."

Both sexes mate from an early stage with females storing from males in an external pouch below their mouth. The male passes sperm packages into the pouch where they are stored for later egg fertilization.

"A male's sperm packages, called spermatophores, take time to produce and he must pass several to the female if he hopes to fertilize her eggs. If she is using the nutrients received from ejaculate consumption to develop her unfertilized eggs, he may even be helping the next male that mates with her"." Mr Wegener said.

"By targeting those larger females less likely to consume their spermatophores, male southern bottletail squid attempt to maximise their chances for egg fertilization."

The studies also found the males were more likely to successfully transfer spermatophores to females already carrying eggs.

"Interestingly, sperm storage appears to last only about three weeks in this species. If females do not lay eggs within this timeframe, they still gain the nutrients from males through spermatophore consumption," Mr Wegener said.

In comparison, males seem to draw the short straw, losing their investments without fertilizing a single egg."

Mr Wegener said science has shown that the ejaculate is a vital adaptation for most sexually reproducing species.

"If a male produces an ejaculate that isn't able to successfully compete in the egg fertilization race, he is essentially an evolutionary dead end," Mr Wegener said.

"Our research has shown how sexual selection, common to all sexually reproducing species, is capable of shaping a species' reproductive strategies in some of the most unexpected ways.

"But it also raises more questions yet to be explored - are females using males as a food source or as a means to assess the quality of her partners? Are even capable of using this feeding behaviour to manipulate female reproduction? Hopefully future discoveries will uncover the answers."

The species can grow up to 4 centimetres in length and are found around the Spencer Gulf in Southern Australia, with healthy populations in Port Phillip Bay.

Explore further: Reversal of the black widow myth

Related Stories

Lady flies can decide who will father their young

Apr 11, 2013

Females in the animal kingdom have many methods available to them to help bias male paternity. One such process is displayed by Euxesta bilimeki, a species of Ulidiid fly, whose females expel and then consum ...

Reversal of the black widow myth

May 06, 2013

The Black Widow spider gets its name from the popular belief that female spiders eat their male suitors after mating. However, a new study has shown that the tendency to consume a potential mate is also true of some types ...

Male bushcrickets are in charge when it comes to sex

Dec 14, 2012

All a question of timing: When bushcrickets mate, the male attaches a sticky package, the so-called spermatophore, to the female's abdomen. Alongside the sperm themselves, this 'bridal present' consists of ...

Guppies and sexual conflict? It's a genital arms race

Jun 03, 2013

(Phys.org) —It's not always easy to tell if a fish is male or female: they look more or less the same. But there are exceptions, such as guppies and, as with humans, guppy genitalia varies in size across ...

Hens' sperm ejection secrets

Aug 03, 2011

In reproductive warfare sperm is a male’s ultimate weapon to decide who fathers the next generation.

Recommended for you

Male monkey filmed caring for dying mate (w/ Video)

36 minutes ago

(Phys.org) —The incident was captured by Dr Bruna Bezerra and colleagues in the Atlantic Forest in the Northeast of Brazil.  Dr Bezerra is a Research Associate at the University of Bristol and a Professor ...

Orchid named after UC Riverside researcher

18 hours ago

One day about eight years ago, Katia Silvera, a postdoctoral scholar at the University of California, Riverside, and her father were on a field trip in a mountainous area in central Panama when they stumbled ...

In sex-reversed cave insects, females have the penises

20 hours ago

Researchers reporting in the Cell Press journal Current Biology on April 17 have discovered little-known cave insects with rather novel sex lives. The Brazilian insects, which represent four distinct but re ...

Fear of the cuckoo mafia

20 hours ago

If a restaurant owner fails to pay the protection money demanded of him, he can expect his premises to be trashed. Warnings like these are seldom required, however, as fear of the consequences is enough to ...

User comments : 0

More news stories

Male monkey filmed caring for dying mate (w/ Video)

(Phys.org) —The incident was captured by Dr Bruna Bezerra and colleagues in the Atlantic Forest in the Northeast of Brazil.  Dr Bezerra is a Research Associate at the University of Bristol and a Professor ...

Scientists tether lionfish to Cayman reefs

Research done by U.S. scientists in the Cayman Islands suggests that native predators can be trained to gobble up invasive lionfish that colonize regional reefs and voraciously prey on juvenile marine creatures.

Leeches help save woman's ear after pit bull mauling

(HealthDay)—A pit bull attack in July 2013 left a 19-year-old woman with her left ear ripped from her head, leaving an open wound. After preserving the ear, the surgical team started with a reconnection ...