Disposable penis and its replenishment in a simultaneous hermaphrodite

Area of Science:

• Marine Biology
• Sexual Selection
• Reproductive Strategies

Background:

• Sexual selection is often considered weaker in simultaneous hermaphrodites compared to gonochorists.
• However, some hermaphroditic species exhibit unusual mating behaviors.
• The nudibranch Chromodoris reticulata is a simultaneous hermaphrodite with a unique reproductive strategy.

Purpose of the Study:

• To investigate the peculiar mating behavior of the simultaneously hermaphroditic nudibranch Chromodoris reticulata.
• To understand the reproductive implications of penis autotomy and regeneration in this species.
• To explore the potential role of sperm competition and removal in their mating system.

Main Methods:

• Observation of mating behavior in Chromodoris reticulata.
• Examination of autotomized penes for sperm presence and morphology.
• Analysis of penis structure related to regeneration and copulation frequency.

Main Results:

• Chromodoris reticulata autotomizes its penis after each copulation.
• The penis is internally spiraled and compressed, allowing for rapid regeneration.
• Regenerated penes enable multiple copulations within a 24-hour period.
• Autotomized penes showed entangled sperm masses and backward-pointed spines, suggesting sperm removal from partners.

Conclusions:

• The 'disposable penis' strategy in Chromodoris reticulata is a novel reproductive adaptation.
• This behavior may enhance fertilization success through repeated mating and potential sperm displacement.
• This finding challenges previous assumptions about sexual selection intensity in simultaneous hermaphrodites.