Research determined that these species allocate up to 6% of their body weight in seminal material, which is considered very high for vertebrate animals.

  • Paulina Quiroz, Graduate School for Science Faculty UACH.

Regularly, and in various species in nature, it is the females who bear the highest energy cost in the reproductive cycle, however, a recent study in the scientific journal Scientific Report revealed that male crabs invest a large amount of energy in their mating strategy, in order to ensure their paternity.

The research, led by Katrin Pretterebner, belonging to the PhD in Marine Biology of the Austral University of Chile (UACh), focused on evaluating the male energy investment in the production of gametes, comparing four species of crabs that inhabit Los Molinos Bay, in the Los Ríos Region: Homalaspis plana, Romaleon setosum, Metacarcinus edwardsii and Taliepus dentatus.

As explained by the scientific team, the different strategies and behaviors observed in males to ensure paternity are related to the natural selection of the species, with a focus on the genes transfer to the next generation. In the case of vertebrates, energy expenditure in sperm production is considered low, while in some invertebrates, such as crabs, up to 6% of their body weight is spent on seminal material, which is considered very high.

The work co-developed by doctors Luis Miguel Pardo, Kurt Paschke and Marcela Paz Riveros, belonging to IDEAL Center also deepened into the weight and size of the reproductive system of males and their various tactics to avoid competition for paternity, among which morphological, physiological and behavioral adaptations such as protection of the partner, multiple copulations and sperm plugs, among others, stand out.

There are species in which the males invest a significant amount of energy in behavior and associated products of seminal material, not necessarily sperm.

Bridal Gift

Among the analyzed species, two groups were clearly distinguished with great differences in energy investment, divergent in the evolution and development of their reproductive system. Thus, Homalaspis plana (Purple crab) and Romaleon setosum (Hairy crab) showed a high investment in terms of energy in the seminal storage structure of the male, which was larger and more complex, in contrast to the reproductive system of the male. Metacarcinus edwardsii (Mola rock crab) and Taliepus dentatus (Panchote or Chilean kelp crab.)

Additionally, in those species that showed higher energy expenditure, anatomical adaptation and a long protection of the couple to ensure paternity were observed. In this context, post-copulatory vigilance occurs after the female’s shell has moulted, when her shell is soft, leaving her vulnerable to predators. Energy was measured through biochemical profiles using proximal analyzes that estimate carbohydrates, lipids, and proteins.

Dr. Pardo explained that, in general, the energy expenditure in reproduction is taken by the females in animal species, due to the size of the female gametes. “In simple terms, the egg is larger and has yolk (nutritive substances) being more ‘expensive’ energetically as opposed to sperm. However, there are species in which the males invest a significant amount of energy in behavior and associated products of seminal material, not necessarily sperm”, he indicated.

Finally, another relevant aspect in the reproductive process of crabs and crabs is that, as occurs, for example, in insects, the male makes a “bridal gift” to the female of specific proteins and lipids during mating, in order to stimulate oocyte development. “In this case, they are a package of nutritional food that the female can use over time while her gonad develops; we can also translate this as a transfer of energy”, concluded Dr. Pardo.

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