14.02.07
Tremough biologists make breakthrough discovery

University of Exeter biologists from the Tremough Campus, Penryn, which is part of the Combined Universities in Cornwall (CUC) partnership, have made an important new discovery. Based at the University of Exeter's School of Biosciences at Tremough. The researchers studied a captive population of green swordtail fish, a species native to Central America and popular in tropical aquariums. The green swordtail is named after the striking sword-like growth, which males develop on their tail-fin, so they appear larger and more attractive to females. They have shown how the sight of physical ornamentation on another member of the group determines when an individual is ready to mate. Their research, which was carried out with other scientists at the University of Glasgow, has just been published in the Royal Society journal 'Biology Letters'.

The females in the group that were shown males with long 'swords' reached sexual maturity earlier than those that were not by up to four months. Young males that were shown mature males with impressive 'swords' matured later than those that saw lower quality competitors. Both sexes are unconsciously using visual cues to increase their likely mating opportunities. For females, this means maximising the quality of potential mates and for males, this means delaying maturity until there is less competition from more attractive males.

"This is the first evidence that a species adjusts its rate of sexual maturation in response to visual cues. While our study focused on green swordtail fish, it seems unlikely that this attribute is limited to this one species," said Dr Craig Walling of the University of Exeter's School of Biosciences at Tremough.

Previous studies have shown that the timing of sexual maturation can be determined by chemical stimulus from other individuals in a variety of species, including some mammals like rats and sheep. In this study the fish were kept in separate tanks so while they could see members of the opposite sex through the glass, they could not use other senses to respond to one another.

Dr Walling continues: "It's well established that sexual maturation in swordtails is highly variable, occurring anywhere between four and 20 months of age even though they rarely live longer than two years. We were really surprised to find that visual cues can have such an effect on sexual maturation, which is so important to an individual's reproductive success."

The £100 million Tremough campus is a Combined Universities in Cornwall initiative of which the University of Exeter and University College Falmouth are two of the founding partners. It is funded mainly by the European Union (Objective One), the South West Regional Development Agency, and the Higher Education Funding Council for England, with support from Cornwall County Council. Set in 70 acres of countryside, but close to the waterside towns of Penryn and Falmouth, the campus offers a lively student community. The University of Exeter is expanding its courses available to include Politics, Law and History to existing degrees in Mining Engineering, Geology, Biology, Geography, English and Renewable Energy.

For further information contact Sarah Hoyle of the University of Exeter on 01392 262062 or email: S.Hoyle@exeter.ac.uk.

The Objective One Programme for Cornwall and the Isles of Scilly has invested in the Combined Universities in Cornwall (CUC) project, both Phase 1 and Phase 2, through the European Regional Development Fund (ERDF) and the European Social Fund (ESF). The University of Exeter is a partner of the CUC.

Editor's notes:

Clare Morgan
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