A team of researchers found evidence on the feeding strategy of one of the most important marine resources for Chile and Argentina. This phenomenon had only been recorded in captivity until now.
In Chile, distribution of spider crab goes from Valdivia to the south, to Tierra del Fuego Island and the Strait of Magellan.
Andrea Navarro, IDEAL Center. The Patagonian spider crab, whose scientific name is Lithodes santolla, is a predatory species that arouses great economic interest. It has 10 legs, although only eight are visible, and a shell. It feeds mainly on invertebrates on the seabed.
In Chile, its distribution goes from Valdivia to the south, to Tierra del Fuego Island and the Strait of Magellan. Then it reappears in the San Jorge Gulf, and in Argentine waters in the northern sector of Chubut. Although there are various scientific studies on its adult phase, information about its early stages is scarce.
To help fill this gap, a team of researchers focused on analyzing the foraging strategy of juvenile king crabs inside and outside kelp forests. The work was led by scientists from the Center for Dynamic Research of High Latitude Marine Ecosystems (IDEAL) of the Austral University of Chile (UACh), the Magallanes University (UMAG) and the Santísima Concepción Catholic University (UCSC).
The study, published in the prestigious journal Diversity, was carried out through the collection of samples of juveniles in Bahía El Águila —south of Punta Arenas—, a place that houses an underwater forest of Macrocystis pyrifera, an alga commonly known as “huiro” or “sargasso.” Subsequently, analyzes were carried out on the stomach contents and stable isotopes. Using these tools, the variation in diet composition was determined.
The analysis of the largest juveniles spider crabs showed that 40% had evidence of having preyed on the small ones.
“With this double methodology, we were able to establish that there are several stages. When the individual is small, it is considered cryptic, that is, it hides and blends in with the huiro environment. However, in the later juvenile period, the crabs are vagile, which means that they have small foraging excursions outside the forest and at greater depths, accessing a greater food supply,” explains Dr. Luis Miguel Pardo, author of the study, researcher at the IDEAL Center and director of the Graduate School of the Faculty of Sciences of the UACh.
At the same time, the team of scientists managed to determine that there is a high incidence of cannibalism: The analysis of the largest juveniles showed that 40% had evidence of having preyed on the small ones. Cannibalism had only been recorded in captivity until now. “This information is important to understand the role of Lithodes santolla in ecosystems and its relationship with the huiro forest. Knowledge of the early stages of life can help us in future plans for the conservation and management of the crab resource, such as eventual repopulation programs,” concludes Dr. Pardo, also an academic at the Institute of Marine and Limnological Sciences (ICML) of UACH.
Read the study here.