THE SNAIL’S LOVE DART
When we talk about competition for mates, we often think of behaviors involving tense fights or flamboyant displays of traits that signal quality. However, sometimes the competition continues even after mating, as the sperm must outcompete sperm from other mates.
In land snails of the families Helicidae and Ariophantidae, this post-copulatory competition involves the injection of a calcium-based “love dart”. These snails are simultaneous hermaphrodites, so during mating, both partners can act as male and female, leading to …
When we talk about competition for mates, we often think of behaviors involving tense fights or flamboyant displays of traits that signal quality. However, sometimes the competition continues even after mating, as the sperm must outcompete sperm from other mates.
In land snails of the families Helicidae and Ariophantidae, this post-copulatory competition involves the injection of a calcium-based “love dart”. These snails are simultaneous hermaphrodites, so during mating, both partners can act as male and female, leading to competition over paternity. Shooting the dart forms part of the courtship ritual, in hopes of increasing the shooter’s success at paternity. The love dart is coated with sticky mucus from a gland located near the dart sac.
Using an integrative approach, Stewart and colleagues (2016) showed that the mucus of the garden snail Cornu aspersum contains a bioactive substance, dubbed the “love dart allohormone” (LDA). When the LDA is transferred to the mating partner, it induces physiological changes in the female reproductive system that reduce digestion of sperm. This socially transferred material increases the chances that the shooter’s sperm will be used for fertilization, thereby enhancing paternity success.
The study also identified numerous additional peptides in the dart mucus that may influence the mating behavior of recipient snails. Further research is needed to disentangle the functions of these peptides, as well as other LDA precursor molecules. Future work on this topic will advance our understanding of the evolution of accessory glands and their products as well as alternative reproductive strategies.
Source:
Stewart M, Wang T, Koene J, Storey KB & Cummins SF. 2016. A “Love” Dart Allohormone Identified in the Mucous Glands of Hermaphroditic Land Snails. Journal of Biological Chemistry 291:7938-7950. https://doi.org/10.1074/jbc.M115.704395
FEEDING ON SLIME
Velvet worms are among the most extraordinary animals on earth! With a very simple body structure, these ancient animals have been living on our planet for nearly 500 million years. Despite their name, they are not actually worms. They are not insects either, but look like caterpillars, and belong to their own phylum called Onycophora.
Onycophorans have a remarkable technique for hunting. To capture their prey, velvet worms eject a sticky, adhesive slime from their oral papillae, which are located close to their mouth. The sticky slime immobilizes the prey so that the velvet worm can then casually approach it.
In a study of feeding behavior conducted in Costa Rica in 2019, researchers documented for the first time a form of parental feeding in velvet worms...
Velvet worms are among the most extraordinary animals on earth! With a very simple body structure, these ancient animals have been living on our planet for nearly 500 million years. Despite their name, they are not actually worms. They are not insects either, but look like caterpillars, and belong to their own phylum called Onycophora.
Onycophorans have a remarkable technique for hunting. To capture their prey, velvet worms eject a sticky, adhesive slime from their oral papillae, which are located close to their mouth. The sticky slime immobilizes the prey so that the velvet worm can then casually approach it.
In a study of feeding behavior conducted in Costa Rica in 2019, researchers documented for the first time a form of parental feeding in velvet worms involving a socially transferred material. Barquero-Gonzales and colleagues showed that in some species, during the first two weeks after birth, the young only eat one thing: the threads of slime used by their parents to capture their prey! This is an unusual form of parental care, and noteworthy as an example of early evolution of a socially transferred material given how ancient these creatures are.
The slime is composed of proteins and lipids, and although its original function may have been defense and prey capture, the components of the slime also represent a good quality food source. So far this is the only study documenting this behavior in velvet worms, so more work is needed to understand the nutritional importance of slime feeding in young velvet worms.
Source: Barquero-González JP, Vega-Hidalgo A & Monge-Nájera J. (2019). Feeding behavior of Costa Rican velvet worms: food hiding, parental feeding investment and ontogenetic diet shift (Onychophora: Peripatidae). doi.org/10.22458/urj.v11i2.2195