Hunting maidens with a pointed arrow
The strange Roman snail custom of torturing the courted mother-to-be with a sharp lime arrow actually serves to minimize the digestion of the sperm cells in the female's body by means of a slime supplied. This is reported by Ronald Chase and Katrina Blanchard of McGill University in Québec.
The "love arrow" shot towards the end of the hermaphrodite act by the animal acting as a male usually misses - but whether it hits or not has no influence on whether copulation takes place at all and how large the sperm package handed over to the would-be father's fails. However, a successful shooter still has greater chances of actually enjoying young talent than a missed target.
Chase and Blanchard suspected more than the purely mechanical irritation caused by the penetrating tip as the cause of the success. So they collected spotted edible snails (Cantareus aspersus) from the area, placed them in isolation for a period of time to exclude other fathers, and then allowed them to make love to other specimens that they had previously removed arrow and slime glands from. Instead, they injected the prospective sperm recipients directly into their bellies with saline solution or a homogenized mixture of mucus obtained by previously milking conspecifics.
The subsequent paternity test confirmed the hypothesis that the mucus pack makes a decisive contribution to reproductive success: If the females only received saline solution at the rendezvous, the proportion of offspring from the respective fathers was halved compared to those whose wooing the researchers had crowned with mucus. Earlier laboratory tests support the suspicion: according to in-vitro experiments, the secretion causes contractions in the organs receiving the sperm and thus prevents the sperm cells from being destroyed by digestive enzymes.
But the researchers also found that almost half of the young snails had an alien father outside of their laboratory specimens. Apparently, the animals had been mated weeks before moving from the wild to the enclosure and had saved the sperm cells for a correspondingly long time. Since this significantly reduces the reproductive success, according to Chase and Blanchard, it is advisable for the temporary snail men not only to perfect their slime arrow shooting technique, but also to look for virgins in order to be the first and thus most promising paternity candidates. However, the researchers do not know whether the animals are even capable of controlling one and registering the other.
