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 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

IS THE HEALTH OF THE OFFSPRING REALLY ONLY THE MOTHER’S RESPONSIBILITY?

Decades of research have been dedicated to link the mother’s health and nutritional habits with the health of their children in both the short and the long term. And yes, it is important of course! However, what do we know about the effect of the father’s nutritional habits? Is the father’s only job really to contribute sperm to fertilize the egg? In short, the answers are “yes” and “no”. Yes, because the nutritional habits of the father also affect the offspring. And no, because the sperm does not only contribute genetic material, but also play a fundamental role in fetal and child development.  

In an elegant review, Skerrett-Byrne and colleagues (2025) remind us that sperm is far from being only a passive DNA carrier, but rather is an epigenetically active player. The epigenome can be thought of as a set of chemical tags that dictate gene expression, turning different genes on and off. In their review, the researchers point out that sperm can acquire epigenetic information, driven by environmental and dietary stressors. They highlight evidence that shows how a high-fat-diet (HFD) causes epigenetic changes in fathers’ sperm that in turn alter the expression of genes and small non-coding RNAs. These changes are implicated in placental and embryonic development, as well as metabolic disease susceptibility in offspring after birth.

The review goes a step further by introducing an interactive digital application, ShinySpermPlacenta, designed to facilitate open-access exploration of the paternal epigenetic data. Users can explore the overlap between HFD sperm epigenetic data and placenta phenotype-driven genes. The app aims to promote systems-level understanding of how preconception environments shape the next generation.

Although the research on the transgenerational effects of paternal nutrition is still new compared to research on maternal nutrition, the growing body of evidence is substantial. Skerrett-Byrne and colleagues highlight the need to reframe preconception care as a truly bi-parental responsibility, rather than placing the entire burden on mothers. This fresh perspective could improve fertility and reduce pregnancy complications and chronic disease in our society.

Source: 

Skerrett-Byrne DA,  Pepin AS,  Laurent K, Beckers J,  Schneider R,  de Angelis MH & Teperino R. 2025. Dad’s diet shapes the future: How paternal nutrition impacts placental development and childhood metabolic health. Molecular Nutrition & Food Research, 0:e70261. https://doi.org/10.1002/mnfr.70261

TOXIC SEX: WHEN POISON BECOMES A GIFT

Blister beetles, as their name suggests, are beetles of the Meloidae family known for causing blisters upon contact with human skin. Toxicity in these coleopterans is due to the presence of a defensive chemical compound in their hemolymph called cantharidin, which is known to be toxic to mammals, birds, and frogs. Cantharidin has fascinated scientists and human societies alike for centuries and has a long history in both scientific and popular literature.

Female blister beetles contain less cantharidin than males. They are unable to synthesize it themselves, but the way that they acquire it is fascinating: they receive it from males! Cantharidin is synthesized in the accessory reproductive glands of male blister beetles. The males incorporate it into the spermatophore, and then it is transferred as a nuptial gift during copulation. Females then absorb the cantharidin and incorporate it into their bodies, thereby achieving chemical defense.

Another extraordinary aspect of this process is that females accumulate cantharidin in their ovaries and add it to their eggs. Therefore, blister beetle eggs are also chemically protected against predation. This system is particularly interesting because it is a case in which the same material is socially transferred in two different contexts: from male to female during mating and from female to eggs during maternal provisioning.

In human society, cantharidin has been known for over 2000 years. It has been used in traditional medicine and pharmacology in a multitude of cultures and countries, as an aphrodisiac, a drug, and even a poison. Derivatives of cantharidin are currently being investigated as therapeutic alternatives due to their strong potential as novel anticancer agents. Cantharidin itself was recently approved by the FDA (as a topical solution called “YCANTH”) to treat molluscum contagiosum. The blister beetle-cantharidin system is a great example of how one can derive useful benefits, here in a medical context, from the wonders of nature and the powers of Socially Transferred Materials.

Recommended literature:

McCormick JP, Carrel JE, 1987. Cantharidin biosynthesis and function in meloid beetles. In: Prestwitch, GD, Blomquist, GJ. (Eds.), Pheromone Biochemistry. Academic Press, Orlando, FL, pp. 307–350. https://doi.org/10.1016/B978-0-12-564485-3.50015-4

Muzzi M, Mancini E, Fratini E, Cervelli M , Gasperi T, Mariottini P, Persichini T, Bologna MA & Di Giulio, A. 2022. Male Accessory Glands of Blister Beetles and Cantharidin Release: A Comparative Ultrastructural Analysis. Insects 13, 132. https://doi.org/10.3390/insects13020132 

Scott KA, McCluskey A, Njardarson JT & Wang W. 2026.On the history, synthesis, and medicinal use of cantharidin, LB-100, and their analogs. Royal Society of Chemistry Medical Chemistry 17, 743–767. https://doi.org/10.1039/d5md00917k 

Sierra JR, Woggon WD, Schmidt H, 1976. Transfer of cantharidin during copulation from the adult male to the female Lytta vesicatoria (Spanish flies). Experientia 32, 142–144. https://doi.org/10.1007/BF01937729

ORAL SEX IN SPIDERS

When we think about sexual rituals in insects, perhaps the first things that come to mind are sexual cannibalism of males by females, nuptial gifts from males to females, opportunistic mating, pair bonding, genital mutilation, or plugging. All of these, while impressive, are relatively well documented.

But, in 2016, Gregoric and colleagues studied the sexual behavior of the Darwin's bark spider from Madagascar. Among the rituals in the diverse and striking sexual repertoire of this species, researchers documented the occurrence of oral sex. That's right! Males of this species obligatorily secrete oral fluids (saliva) into the female genitalia before, during, and after copulation. How’s that for a socially transferred material!

The exact behavioral and adaptive significance of oral contact in the sexual repertoire of the Darwin's bark spider, is yet to be understood. However, the researchers point to two plausible functions of this behavior. By mechanisms of cryptic choice, females might assess male quality and bias the fertilization of their gametes to favor paternity with sperm from better quality males. Another hypothesis suggests that in order to reduce sperm competition, salivary enzymes might induce some sort of physiological advantage to the donor's sperm over the sperm of rivals. However, It is necessary to decipher the composition of male spider saliva before we can determine the significance of this behavior as well as how often it occurs among spiders, or even other animals.

Here you can watch a video of this behavior, posted by the Evolutionary Zoology Lab: https://www.youtube.com/watch?v=_Zp4-tjha6M. It shows the complete behavior, including the transfer of liquid into the female genitals!!!

Source:

Gregorič M, Šuen K, Cheng RC, Kralj-Fišer S & Kuntner M. (2016). Spider behaviors include oral sexual encounters. Scientific Reports 6, 25128. doi.org/10.1038/srep25128