Dr. Brante-Ramirez, Antonio

Among anthropogenic habitats built in the marine environment, floating and non-floating structures can be colonized by distinct assemblages. However, there is little knowledge whether these differences are also reflected in the functional structure. This study compared the functional diversity of sessile and mobile invertebrate assemblages that settle over three months on floating vs. non-floating artificial habitats, in two Chilean ports. Using morphological, trophic, behavioral, and life history traits, we found differences between mobile and sessile as-semblages regarding the effect of the type of habitat on the functional diversity. Compared to sessile assemblages, a greater functional similarity was observed for mobile assemblages, which suggests that their dispersal capacity enables them to balance the reduced connectivity between settlement structures. No traits, prevailing or selected in one or the other habitat type, was however clearly identified; a result warranting for further studies focusing on more advanced stages of community development.

Molluscan veliger larvae and some annelid larvae capture particulate food between a preoral prototrochal band of long cilia that create a current for both swimming and feeding and a postoral metatrochal band of shorter cilia that beat toward the prototroch. Larvae encountering satiating or noxious particles must somehow swim without capturing particles or else reject large numbers of captured particles. Because high rates of particle capture are inferred to depend on the beat of both ciliary bands, arrest of the metatroch could be one way to swim while reducing captures. Larvae in eight families of annelids arrest metatrochal cilia frequently during prototrochal beat, often over a large part of the metatrochal band and with the arrested cilia aligned near the beginning of the effective stroke. In contrast, metatrochs of veligers of gastropods and bivalves rarely arrested while the prototroch beat, and those arrests were more localized and variable in position. This difference in metatrochal arrest was unexpected under hypotheses of either a single origin of this feeding mechanism or multiple origins within each phylum. Although different in metatrochal arrests, larvae of both phyla can separate swimming from feeding while both prototroch and metatroch beat. One hypothesis explaining low rates of capture per encounter, without metatrochal arrest, is a change in adhesion of prototrochal cilia with algae. In a few observations, part of the velar edge was retained within the veliger's shell so that exposed prototrochal cilia contributed to swimming while the adjacent metatroch and food groove were sequestered.

Of the suite of species interactions involved in biotic resistance to species invasions, predation can have complex outcomes according to the theoretical and empirical framework of community ecology. In this study, we aimed to determine the likelihood of consumptive biotic resistance within fouling communities in four ports of central Chile. Notably, we examined the influence of micro- (> 1–2 mm, < 1–2 cm) and macro- (> 1–2 cm) predators, with a particular focus on their effects on non-indigenous species (NIS). Experimental and observational approaches were combined. An exclusion experiment was carried out over 4 months to examine predator effect on the early establishment of new assemblages on settlement panels. Later successional stages upon panels were examined over a total of 26 months and supported by rapid assessment surveys in the surrounding habitats. Community structure was significantly influenced by the exclusion treatments. Macropredators reduced the fouling biomass and abundance, although conflicting patterns emerged from the exclusion of both categories of predators. Altogether, predators reduced the abundance of most NIS and cryptogenic species, some of them being only observed when the two categories of predators were excluded—a pattern generally sustained over the long-term dynamics in community development. Our results show an effective consumptive biotic resistance, furthermore possibly dependent on predator size. Further work is however needed to determine the influence of the functional diversity of natural enemies on the efficiency of biotic resistance and its interplay with other biotic interactions (competition or mutualism). A comprehensive understanding of these processes should in turn help defining management strategies in a context of habitat modification and species loss.

The mussels Perumytilus purpuratus and Semimytilus algosus are two dominant species of intertidal rocky shores of central Chile. These species have marked differences in their distribution patterns with P. purpuratus dominating the mid-intertidal zone and S. algosus dominating the lower intertidal zone usually in habitats influenced by sand. Although it has been suggested that differences in tolerance to environmental conditions, such as air exposure and presence of sand, can explain the distribution of these species, there are currently no experimental studies to support such hypotheses. Here, we evaluated the growth and survival rate in the field of both mussel species at four different tidal heights: 25, 75, 135, and 175 cm above the zero tide. In addition, filtration rates were estimated for both species in the presence and absence of sand in laboratory conditions. The results showed that shell and wet weight growth rates of P. purpuratus were highest in mid- and medium-high tidal heights, whereas the growth rate of S. algosus was highest in the medium-low level. Similar pattern was observed for survival percentage. Furthermore, small S. algosus individuals cultivated with sand in suspension had significantly higher filtration rates than P. purpuratus. In large individuals, no differences were observed between the two species nor between treatments (presence and absence of sand). These results indicate that the differences in the distribution patterns of P. purpuratus and S. algosus in the intertidal can be explained by differences in physiological tolerances to both air exposure and to the presence of sand.

Growing coastal urbanization together with the intensification of maritime traffic are major processes explaining the increasing rate of biological introductions in marine environments. To investigate the link between international maritime traffic and the establishment of non-indigenous species (NIS) in coastal areas, biofouling communities in three international and three nearby local ports along 100 km of coastline in south-central Chile were compared using settlement panels and rapid assessment surveys. A larger number of NIS was observed in international ports, as expected in these ‘invasion hubs’. However, despite a few environmental differences between international and local ports, the two port categories did not display significant differences regarding NIS establishment and contribution to community structure over the studied period (1.5 years). In international ports, the free space could be a limiting factor for NIS establishment. The results also suggest that local ports should be considered in NIS surveillance programs in Chile.

Poecilogony is the production of different larval types within the same species. Although rare, poecilogonous species are ideal systems for testing the evolutionary and ecological implication of different developmental modes in marine invertebrates. Here, we described a new case of poecilogony, the Southern Hemisphere spionid Boccardia wellingtonensis. We used a combination of common-garden experiments, video recordings, and in vitro manipulations of individuals from three sites to (1) document the type of poecilogony, the brooding behavior of the mother, and the hatching process; (2) experimentally measure the effect of nurse eggs on the growth and type of larvae produced; and (3) document variation in the length of the brooding period, number of capsules, larvae, and nurse eggs of mothers from three sites to explore the potential for plasticity in reproductive traits. These results were compared to the previously reported poecilogonous species B. proboscidea, which resembles B. wellingtonensis in size, morphology, ecology, and reproductive strategy but differs in capsule structure. We found that in contrast to B. proboscidea, B. wellingtonensis produced larvae that, in isolation and in the presence of nurse eggs, developed into a wide range of offspring sizes. Mothers brood and hatch the larvae with frequent partial hatching of the brood during the brooding period. Although larvae could not liberate themselves, larvae crossed to other capsules as interconnections between capsules broke during the developmental period, potentially affecting food availability, sibling competition for nurse eggs, and cannibalism. Variation in brooding time and number of capsules deposited among sites suggest local adaptations.

In coastal Antarctic environments, glacial meltwater changes the nutrients and physicochemical parameters in the water column. Consequently, top-down cascading effects are triggered throughout the food web, which can affect the bioenergetic condition of benthic invertebrates and their coupling processes between energy levels and flows throughout the marine food web. In this study, two benthic polychaetes (Maldane sarsi antarctica and Notomastus latericeus), exposed to the impact of glacial melting over a broad time scale, were used to evaluate the effect of glacial meltwater on their bioenergetic condition through the integrated analysis of: i) their biochemical composition; ii) fatty acid profiles and iii) total energy contents. The findings indicate that glacial meltwater has a direct effect on the bioenergetic condition of polychaetes. In areas where glacial meltwater has a significant impact, N. latericeus showed higher levels of proteins and glucose, but lower levels of lipids. On the other hand, M. sarsi antarctica exhibited decreased protein content with increasing glacial meltwater impact. M. sarsi antarctica presented varying levels of lipids across different sites, with the highest concentrations observed in areas with moderate impact. Both species showed a reduction in fatty acids with increasing glacial meltwater impact. Additionally, M. sarsi antarctica individuals from highly impacted areas had lower energy levels than those from less impacted areas, while N. latericeus had higher energy levels in the most impacted site. This information enables the development of a framework for assessing the impact of climate change using glacial meltwater and the integrated bioenergetics of key benthic polychaeta as a proxy. Therefore, identifying how glacial meltwater affects their bioenergetic condition helps us understand how climate change could affect trophic interactions, structure, and energy flows in the Antarctic marine food web.

Post-settlement movement has been reported mainly in marine species with low or reduced adult mobility, where distribution varies in accordance with ontogeny, thus avoiding or reducing environmental stress or biological interactions. Mussels show high dispersal at the larval stage, and settlement is a highly complex process in which larvae must choose an appropriate site to attach. Although adults are mainly sedentary, it has been shown that they move on a local scale during the benthic phase in response to physical and biological factors. Semimytilus algosus and Perumytilus purpuratus are two bioengineer mussel species cohabiting most of the Chilean rocky shores. While S. algosus occurs in the low intertidal zone, P. purpuratus dominates the mid and mid-high zones. Field and laboratory experiments have shown that S. algosus is a weak competitor with respect to P. purpuratus, and post-settlers present high mobility to relocate in the intertidal. Under this scenario, we evaluated the dispersal behavior of juveniles and adults of S. algosus as a potential response to competition with P. purpuratus. We also measured the attachment strength of S. algosus in the presence of its competitor, as a measure of its escape response ability. Our results showed that the presence of P. purpuratus increased the movement activity of juveniles and adults of S. algosus and decreased their attachment strength. Field experiments carried out with marked individuals in a Chilean rocky shore, showed that S. algosus exhibits higher local dispersion in the zone where P. purpuratus is present. Mussels' high dispersal ability throughout the whole benthic phase may not only serve to reach the optimal physiological position in the intertidal, but also to reduce competition interaction.

One of the most important issues in biological invasions is understanding the factors and mechanisms determining the invasion success of non-native species. Theoretical and empirical works have shown that genetic diversity is a determinant of invasion success; thus, studying spatial patterns of genetic diversity, and exploring how biological and physical factors shape this population trait, are fundamental for understanding this phenomenon. Coastal marine ecosystems are one of the most susceptible habitats to invasion given the complex network of maritime transport. In this work we study the cryptogenic anemone, Anemonia alicemartinae, which has rapidly increased its geographical range southward during the last 50 years (approx. 2000 km) along the southeastern Pacific coast. Based on COI mtDNA sequences we evaluated three main hypotheses: a) the genetic diversity of A. alicemartinae decreases according to the direction of invasion (from north to south); b) there is biogeographic–phylogeographic concordance at the 30°S biogeographic break; and c) the demographic history is coherent with a recent geographic expansion. A total of 161 individual samples of A. alicemartinae were collected along the southeastern Pacific coast range of distribution, covering more than 2000 km, including samples along the 30°S biogeographical break. Results showed low genetic diversity (Hd = 0.253; π = 0.08) and a lack of geographic population genetic structure (FST = − 0.009, p-value = 0.656). The highest genetic diversity was observed in Peru (Chero and Mesas) and at localities close to the main Chilean seaports. We did not observe concordance between biogeographic and phylogeographic patterns or isolation by distance. Demographic indices (D = − 2.604, p < 0.001; Fu's = − 26.619, p < 0.001), as well as a star-like configuration of the haplotype network support recent population expansion of this species. Our results, together with historical field observations, support the idea that the current distribution of A. alicemartinae may be explained by an increase in population size from one small ancestral population probably from the south of Peru, with subsequent human-mediated southward transport, probably associated with regional-scale maritime activities.

Poecilogony is a type of reproduction in which a species produces different types of larvae. Boccardia wellingtonensis, is a poecilogonous polychaete with females producing planktotrophic and adelphophagic larvae, in addition to nurse eggs, in the same capsule that differ in feeding behavior. It is still unclear why planktotrophs do not feed on nurse eggs during the intracapsular development and arrest its growth, while adelphophagic larvae consume nurse eggs and planktotrophic larvae inside the capsule, hatching as advance larvae or as juveniles. Here we characterized the expression of selected miRNAs from these two types of larvae and from adults in order to begin to understand the molecular mechanisms that regulate expression in this type of poecilogony. Results showed that adults and pre-hatching adelphophagic larvae have high levels of expression of miR-125, miR-87a and let-7, while adelphophages at early developmental stage had low levels of expression of miR-87b. Planktotrophic larvae showed low expression level of let-7. This work represents the first step in understanding the role of miRNAs in the development of different larval types in a poecilogonous species. We also propose to B. wellingtonensis as an interesting biological model to study the evolution of larval modes and reproductive strategies of marine invertebrates.