F. Patricio Ojeda

Diversity, dynamics and biogeography of Chilean benthic nearshore ecosystems: an overview and guidelines for conservation

A pesar de que Chile ha sido un pais pionero en estudios del efecto del impacto humano sobre la estructura comunitaria en ambientes marinos, y a pesar de la enorme importancia economica y social que el ambiente marino tiene para el pais, el desarrollo de programas de conservacion marina y de bases cientificas para la sustentabilidad no se han generado a la misma tasa a la que han explotado los recursos y se ha utilizado el ambiente costero para diversos fines. Aunque nosotros pensamos que el establecimiento de planes de conservacion a lo largo de la costa de Chile debe basarse en varios factores, los principios cientificos, biologicos y ecologicos deben guiar muchos de estos esfuerzos, y en este trabajo nosotros intentamos presentar una vision general del estado actual del conocimiento sobre la ecologia y la biogegrafia del sistema costero en Chile. En base a la informacion mas relevante existente, nuestros objetivos son: 1) identificar las caracteristicas biogeograficas y ecologicas del ecosistema costero y tambien vacios en informacion, 2) identificar las actividades humanas mas daninas que tengan impacto en la estructura y dinamica de estos sistemas, y 3) sugerir el uso de posibles indicadores para determinar la situacion de diferentes areas de la costa de Chile, y las necesidades de conservacion. Esta revision muestra, por un lado, areas geograficas con informacion critica deficitaria para planes futuros de manejo y conservacion marina , y por el otro lado, la disponibilidad de informacion de alta calidad para otras zonas geograficas del pais. Respecto de la informacion existente sobre taxonomia y patrones de distribucion de especies a gran escala, existen importantes vacios de informacion; no se esperan en el futuro grandes cambios en el numero total de especies. Existen pocos estudios sobre patrones de distribucion de especies a gran escala, y mas informacion es necesaria para identificar areas de alta diversidad de especies, especialmente para algunos taxa, como tambien para identificar areas que posean caracteristicas unicas en relacion a especies (endemicas, especies claves) y a procesos ecosistemicos (disturbios, surgencias). Para la mayoria de los invertebrados y macroalgas, las areas de alta diversidad de especies se encuentran en el sur de Chile. Nuevos estudios dirigidos a entender los factores que podrian generar patrones a macroescala son necesarios, como tambien informacion sobre oceanografia costera y disponibilidad de larvas. Esta informacion es clave para el diseno de una futura red de parques marinos. Por otro lado, la informacion disponible sobre estructuras comunitarias y funcionamiento ecosistemico, especialmente sobre el efecto del impacto humano, provienen de pocas regiones geograficas. Mas informacion sobre otras zonas geograficas es requerida, particularmente si se consideran las diferencias notables en temperatura, patrones de circulacion, heterogeneidad del habitat, y composicion de especies, como tambien el efecto de surgencia y de El Nino a lo largo de los mas de 4.000 km de costa de Chile. Finalmente, listamos las que consideramos son las actividades humanas mas daninas para el ambiente marino, e integramos esta informacion para sugerir posibles indicadores ambientales y necesidades basicas y sugerencias para conservacion marina in Chile

Guild structure of carnivorous intertidal fishes of the Chilean coast : implications of ontogenetic dietary shifts

Abstract Although ontogenetic changes in resource use within species are common in animals, these changes have not been widely considered in studies of guild structure within communities. The occurrence of one or more shifts in resource use in an individual of a given species during its life should mean that it would also belong to different guilds at different life stages. We specifically addressed this issue by describing the feeding habits of ten species of carnivorous fishes occurring in tidepools in rocky intertidal areas along the coast of central Chile. Most of these species undergo clear ontogenetic dietary shifts and a feeding guild structure of this group of fishes was established that takes these dietary shifts into account. Each species was divided into a number of size classes. Dietary overlap values between both intraspecific and interspecific size-class pairs in the entire group of ten species were used to construct a phenogram of dietary similarity through an UPGMA cluster analysis. Numbers of guilds and their memberships were established objectively by applying a bootstrapping procedure. Four “ontogenetic” feeding guilds (OFGs), each consisting of size-classes of species, were recognized. The majority of species belonged to more that one guild. Interestingly, when the bootstrapping procedure was applied to a phenogram based on the diets of “taxonomic” or complete species, only one significant guild was found. The implications of these ontogenetic dietary shifts for interspecific interactions are substantial because the identity of the species with which each fish species shares resources change through their lives. The usefulness of taxonomic species for investigating potential competitive interactions in this assemblage is greatly undermined.

Feeding guild structure of a rocky intertidal fish assemblage in central Chile

The identification and analysis of the guild structure of vertebrate assemblages has played a fundamental role in the understanding of the underlying mechanisms responsible for their community organization and structuring. This approach generally has not been undertaken for temperate water intertidal fish assemblages. In central Chile, fishes are important components of the intertidal community, but no studies attempting to understand their organization and structuring have been done. In the present study, the diets of 13 of the most abundant species which inhabit tidepools in the rocky intertidal zone of central Chile were determined. A total of 660 fishes was collected at 5 sites: Los Molles, Con-Cón, Quintay, El Tabo, and Las Cruces. Dietary overlap between all species pairs was calculated and a phenogram of dietary similarity was constructed and analyzed using a bootstrapping technique to objectively determine guild membership. The results showed that the intertidal fish assemblage of central Chile can be divided into three feeding guilds: two guilds consisting of carnivorous species and one guild of omnivorous and herbivorous species. The possible causes and implications of the resulting guild structure and the potential effects of predation by these fishes on other components of the intertidal community are discussed.

Biogeographic patterns of Chilean littoral fishes

En este estudio, analizamos los patrones biogeograficos de los peces litorales chilenos, incluyendo las tendencias latitudinales en riqueza de especies de peces teleosteos y condrictios, sus rangos de distribucion, y nivel de endemismo, tanto para la costa de Chile, como para el Pacifico Suroriental. Determinamos el numero y porcentaje de taxa de peces pertenecientes a cuatro grupos segun sus afinidades biogeograficas. Esta asignacion a grupos se hizo al nivel de especie, genero y familia, tanto para teleosteos como condrictios. Con el fin de determinar la existencia de regiones biogeograficas, utilizamos analisis de conglomerados y ordenacion en conjunto con tecnicas de aleatorizacion, para los tres niveles taxonomicos estudiados. Se determino que la diversidad de peces litorales se mantiene relativamente constante a lo largo de la costa, hasta alrededor de los 40o S, disminuyendo hacia el sur. Detectamos dos regiones biogeograficas a lo largo de la costa chilena, con un quiebre entre ellas a los 40o S. Estos resultados apoyan la existencia de las provincias biogeograficas o unidades faunisticas reconocidas previamente en la literatura. Estas dos regiones biogeograficas reflejan el origen mixto de la ictiofauna litoral chilena, la que consiste de especies de peces de origen subtropical y subantartico. Aunque el porcentaje de peces endemicos a la costa chilena es bajo (18%), un alto porcentaje de las especies de teleosteos presentes en aguas chilenas es endemico al Pacifico Suroriental (44%). Procesos relacionados con fenomenos de dispersion y la historia evolutiva de los componentes de esta fauna explicarian de mejor manera los patrones de distribucion observados mas que otros factores sugeridos en la literatura. Este estudio representa un primer paso hacia una mejor comprension de la biogeografia de los peces marinos del Pacifico Suroriental

Metabolic and behavioral alterations in the crab Hemigrapsus crenulatus (Milne-Edwards 1837) induced by its acanthocephalan parasite Profilicollis antarcticus (Zdzitowiecki 1985)

Abstract Acanthocephalans are parasites with complex life cycles. The parasitic larval stages are found mostly within crustaceans, while the adults live in the digestive tract of vertebrates that prey upon the intermediate hosts. Transition of the cystacanth larvae to the definitive host is mediated by a trophic interaction. To ensure transmission to the final vertebrate host, these parasites are known to induce behavioral changes in the intermediate host, increasing its vulnerability to predation. The acanthocephalan, Profilicollis antarcticus (Zdzitowiecki), has as intermediate host the estuarine crab, Hemigrapsus crenulatus (Milne-Edwards), and as definitive host, the gull, Larus dominicanus . We hypothesized that persistent behavioral alterations observed in crabs infected with acanthocephalans are determined by physiological changes, which are expressed in alterations of the metabolic rate of the intermediate host. Determinations of oxygen consumption were carried out for parasitized and control (non-parasitized) crabs, and metabolic rates were calculated based on oxygen consumption. The crabs infected with cystacanths of P. antarcticus had higher metabolic rates than the control crabs. Patterns of activity of the parasitized and control crabs were recorded according to seven behavioral displays arbitrarily defined. Parasitized crabs were much more active—and excited—than control crabs. These results suggest that the cystacanth larvae of the acanthocephalan, P. antarcticus, induces a phenotypic change in the crab, H. crenulatus, both in the metabolic rate and in activity patterns. This study represents the first experimental demonstration that altered behavior induced by acanthocephalan parasites on their hosts has a physiological basis. The physiological manipulation of the parasite alters the metabolic rate of its host, which is expressed in behavioral changes that increase its vulnerability to predators which are the definitive hosts of the parasite.

Local distribution and thermal ecology of two intertidal fishes

Geographic variability in the physiological attributes of widely distributed species can be a result of phenotypic plasticity or can reflect evolutionary responses to a particular habitat. In the field, we assessed thermal variability in low and high intertidal pools and the distribution of resident fish species Scartichthys viridis and transitory Girella laevifrons along this vertical intertidal gradient at three localities along the Chilean coast: Antofagasta (the northernmost and warmest habitat), Carrizal Bajo (central coast) and Las Cruces (the southernmost and coldest habitat). In the laboratory, we evaluated the thermal sensitivity of fish captured from each locality. The response to temperature was estimated as the frequency of opercular movements and as thermal selectivity in a gradient; the former being a indirect indicator of energy costs in a particular environment and the latter revealing differential occupation of habitat. Seawater temperature in intertidal pools was greatest at Antofagasta, and within each site was greatest in high intertidal pools. The two intertidal fish species showed opposite patterns of local distribution, with S. viridis primarily inhabiting the lower sectors of the intertidal zone, and G. laevifrons occupying the higher sectors of the intertidal zone. This pattern was consistent for all three localities. Locality was found to be a very important factor determining the frequency of opercular movement and thermal selectivity of both S. viridis and G. laevifrons. Our results suggest that S. viridis and G. laevifrons respond according to: (1) the thermal history of the habitat from which they came, and (2) the immediate physical conditions of their habitat. These results suggest local adaptation rather than plasticity in thermoregulatory and energetic mechanisms.

Abundance, distribution and feeding patterns of a temperate reef fish in subtidal environments of the Chilean coast: the importance of understory algal turf

Cheilodactylus variegatus es un pez demersal abundante que habita el submareal somero de la costa norte y central de Chile. Es caracteristico de estos ambientes el estar dominados por praderas del alga Lessonia trabeculata. Esta especie incorpora en su dieta una variada gama de invertebrados bentonicos, mostrando una tasa particularmente alta de consumo de crustaceos anfipodos. En nuestro estudio, se considero dos poblaciones ampliamente separadas de C. variegatus (centro y norte de Chile). Los individuos que integran estas poblaciones exhiben claras diferencias en su distribucion, abundancia y comportamiento trofico. En la zona norte, la especie es abundante y tanto juveniles como adultos se distribuyen a lo largo de todo el gradiente batimetrico. Esto contrasta con las poblaciones de la zona central de Chile, las que estan mas dispersas y desprovistas de juveniles. El patron de distribucion y abundancia parece estar principalmente influenciado por la gran abundancia de diversas especies de macroalgas que conforman el subdosel en el submareal del norte, el que es habitado por un gran numero de invertebrados, especialmente anfipodos. En contraste, la abundancia de algas del subdosel de la zona central es mucho menor y no muestra una relacion directa con la menor abundancia de anfipodos observada. La tasa de consumo que C. variegatus ejerce sobre anfipodos es en general alta durante toda su ontogenia, incorporando a otros items presa en estadios ontogeneticos posteriores. Es posible que los diferentes ensambles de diversas algas de subdosel, junto con su fauna asociada, sean el principal factor que afecta los patrones de abundancia y distribucion observado entre estas dos poblaciones de peces geograficamente distintas

Behavioral thermoregulation in the intertidal fish Girella laevifrons (kyphosidae): The effect of starvation

One of the key factors that determine an animals distribution and abundance is environmental temperature. This factor affects all the components of an organisms energy budget and fitness. In this study, we tested the effect of water temperature and starvation on patterns of space use in the intertidal fish Girella laevifrons. We postulated that starved animals would select cold temperatures as a mechanism of energy conservation while fed animals would prefer higher temperatures as a mechanism to facilitate digestive processes. In a thermal gradient tank, fishes, irrespective of treatment (fed and starved), actively selected temperatures between 15 and 18°C. Starvation did not affect temperature selection, although it did alter the time and number of visits to thermal gradient extremes. Starved fishes stayed longer in, and visited the warmer temperatures of the gradient more frequently. In contrast, fed fishes stayed longer in, and visited cold temperatures more frequently. We discuss the ecological cons...

Is the feeding type related with the content of microplastics in intertidal fish gut

Microplastics pollution is a growing global concern that affects all aquatic ecosystems. Microplastics in the environment can be in the form of fibers and/or particles, being the former the most abundant in the marine environment, representing up to 95% of total plastics. The aim of this work was to compare the content of microplastics among intertidal fish with different feeding type. Our results show that omnivorous fish presented a higher amount of microplastic fibers than registered in herbivores and carnivores. Moreover, lower condition factors (K) were found in omnivorous specimens with higher microplastic content. We hypothesized that the type of feeding resulted in different microplastic ingestion, with species with wider range of food sources as omnivores with higher rates. Futures studies carried out to evaluate the biological impacts of microplastics on marine organisms, and microplastics cycling on the marine environment should consider the type of feeding of the studied species.

Altered dopamine levels induced by the parasite Profilicollis antarcticus on its intermediate host, the crab Hemigrapsus crenulatus

A serotonergic pathway is apparently involved in parasite-host interactions. Previous studies conducted in our laboratory showed increased rates in oxygen consumption and alterations in body posture in the crab Hemigrapsus crenulatus parasitized by the acanthocephalan, Profilicollis antarcticus. Such changes may be related to the functions described for biogenic amines in crustaceans. During the infective stage the acanthocephalans live freely in the hemocelomic cavity, suggesting that the possible alteration induced by biogenic amines may be related to their neurohormonal function in crustaceans. To test whether the presence of P. antarcticus produced neurohormonal changes in its intermediate host, H. crenulatus, we analyzed serotonin and dopamine levels in the host using HPLC with electrochemical detection. Two groups of 11 female crabs were studied; one group was artificially inoculated with two cystacanths while the other was used as the control. Our results show a dramatic increase in hemolymph dopamine, but not serotonin in H. crenulatus parasitized by the acanthocephalan P. antarcticus. Our results, along with those reported by Maynard (1996), suggest a parasite-specific strategy involved in the behavior alteration caused by the acanthocephalans on their intermediate host. The use of a biogenic amine as a mechanism of interaction by the parasites gives them an endless number of alternative potential actions on their intermediate hosts.