The sea slug Chromodoris reticulata sheds and regrows its penis between matings.
MATTHEW OLDFIELD/SCIENCE PHOTO LIBRARY
Sea slug loses penis after sex but grows another the next day
: Invertebrate may discard organ like a dirty needle to avoid carrying competitors' sperm.
Although it is often thought that sexual selection is weaker in simultaneous hermaphrodites than in gonochorists, some simultaneous hermaphrodites exhibit bizarre mating behaviour. In the simultaneously hermaphroditic nudibranch Chromodoris reticulata, we found a peculiar mating behaviour, wherein the nudibranch autotomized its penis after each copulation and was able to copulate again within 24 h. To have sufficient length to be replenished for three copulations, the penis is compressed and spiralled internally. No other animal is known to repeatedly copulate using such ‘disposable penes’. Entangled sperm masses were observed on the outer surface of the autotomized penis, which is equipped with many backward-pointed spines. There is a possibility that the nudibranch removes sperm already stored in a mating partner’s sperm storage organ(s).
Sekizawa A, Seki S, Tokuzato M, Shiga S, Nakashima Y. 2013. Disposable penis and its replenishment in a simultaneous hermaphrodite. Biol Lett. 9: 20121150. http://dx.doi.org/10.1098/rsbl.2012.1150