Nemertean Larval Dispersion Across Biogeographic Provinces of Southwest Atlantic

ALFAYA, JOSÉ E. F.; TONINI, MARIANO H.; SORIA, GASPAR; PENCHASZADEH, PABLO E.; BIGATTI, GREGORIO

ZOOLOGICAL SCIENCE

ZOOLOGICAL SOC JAPAN

Año: 2020 vol. 37

0289-0003

The nemertean Malacobdella arrokeana is a commensal of the edible giant bivalve Panopeaabbreviata; both species have a restricted geographic distribution, high specificity and popula-tions settled along distinct biogeographic provinces. This supposes a high genetic structuringamong populations and low intra-populational variability; nevertheless, a lack of genetic structurewas detected previously between M. arrokeana populations from the Atlantic Northern PatagoniaGulfs System (NPGS) by means of mitochondrial and nuclear markers. Here, we present a modelthat explains this lack of genetic structure, integrating larval development and behavior, as well asbio-oceanographical model simulations. We observed in cultured larvae a maximum 30 days ofplanktonic life before settlement. Planuliform larval morphology and behavior of M. arrokeana sug-gested that the dispersion is more influenced by passive transport rather than active swimming.Modeling larvae as particles indicated that the limit of biogeographical provinces along the NPGSis not a barrier for dispersal, corroborating that larval dispersion is strictly related to season andto hydrodynamic diffusion patterns present in the area. These results explain the lack of geneticpopulation structure recorded before in the NPGS. Our results provide novel baseline data regard-ing larval connectivity and oceanographic circulation patterns on the southwestern Atlantic. Thisinformation can be used as a reference for the implementation of management plans of inverte-brate species with pelagic larvae to ensure the long-term viability of fishery resources shared bydifferent government districts.