Distribuição das ampolas de lorenzini de isogomphodon oxyrhynchus (Muller & Henle, 1839) (Elasmobranchii, Carcharhinidae) e sua relação com a história natural

Abstract

Isogomphodon oxyrhynchus is a medium-sized Carcharhinidae, endemic to the north eastern coast of South America, closely associated with the continental shelf. The perception of the environment and detection of prey through electroreception is fundamental for its survival, since it has small eyes and lives in murky waters. However, there are few studies on the electroreception of the species. Categorized as Critically Endangered by the IUCN, it is caught in fishery bycatch and its population has been declining with a reduction of more than 80% in the last 30 years. Therefore, it is necessary to invest efforts to obtain data on its natural history, constituting an important subsidy for its conservation. The present work aimed to analyze the distribution of the electrosensory pores of I. oxyrhynchus identifying its importance in the natural history of the species. The analysis of the distribution, abundance and density of the pores was carried out based on photographs and digital microscope videos. Isogomphodon oxyrhynchus possesses the highest abundance of pores among all Carcharhiniformes, revealing that this species with small eyes and high turbidity habitats have a well-developed electroreceptor system that may have amplified its evolutionary success in this type of environment. Furthermore, this high abundance can also be explained by being a morphologically derived genus, comprising a more complex and specialized electrosensory system compared to the other species. It has a high-resolution electrosensory system and a high density of pores on the snout, which emphasizes the importance of the elongated snout since it expands the search area coverage to maximize the possibility of detecting prey. There is ontogenetic variation in pore abundance, highlighting the importance of a high-resolution system for adults. The higher density of pores in the ventral region indicates a preference for benthic prey, despite also feeding on pelagic prey. Evolutionary convergence was observed as a phenomenon in the development of the electrosensory system, since I. oxyrhynchus shares characteristics of abundance and distribution of electroreceptors similar to phylogenetically unrelated species, revealing that the characteristics of electroreception are more related to habitat and feeding strategies than phylogenetic relationships.