Dr. Brante-Ramírez, Antonio

The intertidal mussel Perumytilus purpuratus exhibits phenotypic plasticity in response to predation threats, with these responses influenced by the mussels' perception of predation risk. These adaptations, however, are constrained by energy costs and interactions with environmental factors that may trigger synergistic effects or trade-offs among different fitness traits. In particular, this study focuses on the anti-predatory responses of P. purpuratus against the sea star Meyenaster gelatinosus, examining how the presence of the predator and water flow strength influence these responses. The research was conducted through laboratory experiments, comparing mussels from two distinct localities with varying predation risks posed by M. gelatinosus: Punta Hualpén, where the predator is naturally present, and Coliumo, where it is absent. The anti-predatory responses were assessed by measuring attachment strength, byssus production, and adductor muscle mass in the presence of predator cues. Additionally, potential costs associated with these responses were estimated using the gonadosomatic index as a measure of reproductive investment. The findings indicate that the anti-predatory responses of P. purpuratus are contingent on the mussel's origin, with adhesion strength and byssus production negatively impacting reproductive investment. Moreover, the study highlights the intricate interplay of multiple factors, as evidenced by the complex adaptive mechanisms observed in P. purpuratus. The interaction between predator presence and water flow strength and their combined effects on various traits underscores the need for comprehensive multifactorial experiments to understand these adaptive processes. In conclusion, this study provided valuable insights into the nuanced and site-specific nature of anti-predatory responses in P. purpuratus. The research emphasizes the importance of considering multiple factors and conducting comprehensive experiments to unravel the intricacies of adaptive mechanisms in prey species.

Non-native ascidians are important members of the fouling community associated with artificial substrata and man-made structures. Being efficient fouling species, they are easily spread by human-mediated transports (e.g., with aquaculture trade and maritime transports). This is exemplified by the ascidian Asterocarpa humilis which displays a wide distribution in the Southern Hemisphere and has been recently reported in the Northern Hemisphere (NW Europe). In continental Chile, its first report dates back from 2000 for the locality of Antofagasta (23_x000E_S). Although there was no evidence about the vectors of introduction and spread, nor the source, some authors suggested maritime transport by ship hulls and aquaculture devices as putative introduction pathways and vectors. In the present study, we report for the first time the presence of A. humilis on the hull of an international ship in a commercial port in Concepción bay (36_x000E_S), south central Chile. We also found one individual associated to a seashell farm, 70 km far from Concepción bay. Further individuals were subsequently identified within Concepción bay: one juvenile settled upon international harbor pilings and a dozen individuals along aquaculture seashell longlines. For the first specimens sampled, species identification was ascertained using both morphological criteria and molecular barcoding, using the mitochondrial gene cytochrome c oxidase subunit I (COI) and a nuclear gene (ribosomal RNA 18S). The nuclear 18S gene and the mitochondrial gene COI clearly assigned the specimens to A. humilis, confirming our morphological identification. Two haplotypes were obtained with COI corresponding to haplotypes previously obtained with European and Northern Chilean specimens. The present study thus reports for the first time the presence of A. humilis in the Araucanian ecoregion, documenting the apparent expansion of this non-native tunicate in Chile over 2,000 km, spanning over three ecoregions. In addition we reveal the potential implication of the international maritime transport as a vector of spread of this species along the Eastern Pacific coast, and the putative role of aquaculture facilities in promoting local establishments of non-native tunicates.