PARIS: Scientists reported Wednesday on the bizarre sex life of a sea slug that discards its penis after copulation. Then grows a new one.

"No other animal is known to repeatedly copulate using such 'disposable penes'," Japanese biologists wrote in the Royal Society journal Biology Letters, describing the behaviour as "extremely peculiar".

Dubbed Chromodoris reticulata in Latin, the red-and-white slug - technically a shell-less mollusc - inhabits warms waters in Southeast Asia.

The critter needs 24 hours between couplings to unroll an internally coiled and compressed juvenile penis to replace the used, external bit, the scientists found.

It can repeat this feat at least three times.

The human thumb-sized slug is an hermaphrodite, meaning it has both male and female sexual organs.

The animals perform dual sexual roles during copulation. They give sperm to a mating partner while simultaneously receiving sperm, which they store for later insemination.

The team observed copulation between sea slugs that they had captured during scuba dives and held in a tank.

After each coupling, which lasted between dozens of seconds and a few minutes, every slug discarded its penis - a thread-like organ that it projects from its side into a partner's vagina.

The team also examined the microscopic structure and function of the male organs - observing an internal spiral structure they believe grows into a replacement penis.

"We propose that the tissue at the spiral part of the penis is compressed and undifferentiated, gradually differentiating into the 'next penis'," the team wrote.

"It may need approximately a day for the spiral structure to be ready for copulation."

In another revelation about the sea slug's sex life, the scientists found its penis was covered with spines - and suggested these may be used to remove the sperm of previous partners being held in store by their mate.

The spines are backward-pointing, making it difficult to withdraw the penis after copulation. This may explain the organ's disposable nature.

"Chromodoris reticulata may compensate for the short-term cost of decreased reproductive opportunities caused by the loss of a penis with the reproductive advantage gained by sperm displacement," wrote the study authors.

Various animals are known to discard parts of their body, such as the gecko which sheds its tail.

Few, though, are willing to part with their penis, the team noted with clinical understatement. -AFP

• Alliance Neutral on Axiata, ups target price to RM7
• Deleum top loser, down 11.3% after disappointing results
• Maybank KE Research maintains Hold on AirAsia
• Public Invest Research ups Uzma target price to RM2.86
• Malaysia's blue chips fall more than 6pts in early trade
• Profit taking may weigh on Malaysian equities
• HP raises 2013 outlook as Whitman's plan takes hold
• Bernanke says more progress needed before stimulus pullback
• Wall Street falters in volatile session on Fed worries
• Aeon director: GST won’t affect group
• Petronas Chemicals Group to invest RM3bil in capital expenditure
• Weak CPO prices hit Boustead profit
• April CPI up 1.7% on higher food prices
• Report: AirAsia X sets indicative price for IPO
• MAEI sees 3%-4% rise in electrical, electronics exports

• Two babies among US tornado victims
• Anti-Islamist protests flare following London attack
• 'British solider' butchered in suspected Islamist attack

• Ice queen Nicol into British Open quarters
• Australia to consider following ban on anchor putters
• Intxausti wins 16th stage, Nibali still keeps pink jersey
• Indonesia drawn to meet China again – in knockout stage
• Results worldwide
• Malacca sprinter Mohd Azam Masri out to create history by winning five events in MSSM meet
• Athletics runs in the veins of Vallabouy family
• Chinese long jumper Jinzhe claims another Olympic scalp
• Dane Jorgensen’s wish is to avoid Chinese ace Lin Dan in World Championships
• National badminton team’s lack of depth a glaring factor in home tourney
• Khim Wah-V Shem perform above expectations in Sudirman Cup debut
• Jindapon aims to qualify for 2016 Olympics
• Kenichi’s goal is to take Japan into Sudirman Cup semi-finals
• Dong-keun shows he’s a capable replacement
• Harrison makes swift U-turn

• Please wait.

• Actress’ barking pet saves her from attacker in late night incident
• In China, food scares put Mao's self-sufficiency goal at risk
• What comes after WYY?
• Chromebook to help rural pupils leapfrog into parity with urban peers
• Free entry to MATTA Fair in Penang
• All four accused guilty in murder of Sosilawati Lawiya and three others (Update)
• Asean flavour in Invest M’sia confab
• Petronas Chemicals Group to invest RM3bil in capital expenditure
• Report: AirAsia X sets indicative price for IPO
• We have to be humane to all who are put under arrest