Dr. George-Nascimento-Failla, Mario

Hookworms of the genus Uncinaria parasitize pinniped pups in various locations worldwide. Four species have been described, two of which parasitize pinniped pups in the southern hemisphere: Uncinaria hamiltoni parasitizes Otaria flavescens and Arctocephalus australis from the South American coast, and Uncinaria sanguinis parasitizes Neophoca cinerea from the Australian coast. However, their geographical ranges and host specificity are unknown. Uncinaria spp. are morphologically similar, but molecular analyses have allowed the recognition of new species in the genus Uncinaria. We used nuclear genetic markers (internal transcribed spacer (ITS) and large subunit (LSU) rDNA) and a mitochondrial genetic marker (cytochrome c oxidase subunit I (COI)) to evaluate the phylogenetic relationships of Uncinaria spp. parasitizing A. australis and O. flavescens from South American coasts (Atlantic and Pacific coasts). We compared our sequences with published Uncinaria sequences. A Generalized Mixed Yule Coalescent (GMYC) analysis was also used to delimit species, and principal component analysis was used to compare morphometry among Uncinaria specimens. Parasites were sampled from A. australis from Peru (12°S), southern Chile (42°S), and the Uruguayan coast, and from O. flavescens from northern Chile (24°S) and the Uruguayan coast. Morphometric differences were observed between Uncinaria specimens from both South American coasts and between Uncinaria specimens from A. australis in Peru and southern Chile. Phylogenetic and GMYC analyses suggest that south-eastern Pacific otariid species harbour U. hamiltoni and an undescribed putative species of Uncinaria. However, more samples from A. australis and O. flavescens are necessary to understand the phylogenetic patterns of Uncinaria spp. across the South Pacific.

A new species, Hemipera cribbi sp. nov., is described. This trematode was found in three intertidal fish species: Scartichthys viridis (Valenciennes) (Blenniidae), Gobiesox marmoratus Jenyns (Gobiesocidae) and Myxodes viridis Valenciennes (Clinidae) from the central and southern coast of Chile. Of 233 individuals of S. viridis from the central coast examined, 19 were infected. From the southern coast, nine individuals of S. viridis (one infected), five individuals of G. marmoratus (four infected), and 16 individuals of M. viridis (one fish infected) were examined. Hemipera cribbi sp. nov. is distinguished from the five other congeneric species mainly in the body size, being the smallest and narrowest species in the genus, reaching five times longer than wide. This is the first species of the genus described for the South Pacific Ocean off South America. ITS2 rDNA sequences of Hemipera cribbi sp. nov. from each host and locality were identified.

Parasites alter the reproductive performance of their hosts, limit their growth, and thereby modify the energy budget of these hosts. Experimental studies and theoretical models suggest that the outcome of the host-parasite interactions could be determined by ecological factors such as food availability levels in the local habitats. Nutrient inputs may affect the host's food resource availability with positive or negative effects on parasite infection rates and tolerance of infection, however this has not been specifically evaluated in natural systems. In this study, we evaluate the effects of parasitism by Proctoeces humboldti on body size, gonadosomatic index (GSI), and metabolic rate (oxygen consumption) of their second intermediate host Fissurella crassa limpets, under contrasting natural conditions of productivity (upwelling center vs upwelling shadow sites). Our results evidenced that parasitized limpets collected from the intertidal habitat influenced by coastal upwelling site showed greater shell length, muscular foot biomass and GSI as compared to non-parasitized limpets collected in the same site, and compared to parasitized and non-parasitized limpets collected from the sites under the influence of upwelling shadow conditions. Oxygen consumption was lower in parasitized limpets collected from the upwelling-influenced site than in the other groups, independent of age, suggesting reduced metabolic stress in infected individuals inhabiting these productive sites. Our results suggest that increased productivity in upwelling sites could mitigate the conflict for resources in the P. humboldti – F. crassa system, influencing where such interaction is found in the continuum between parasitism and mutualism. Since parasitism is ubiquitous in natural systems, and play important roles in ecological and evolutionary processes, it is important to analyze host-parasite interaction across a variety of ecological conditions, especially in biological conservation.

The most studied digenean of marine organisms in Chile is by far Proctoeces humboldti, a parasite of the intestine of the clingfish Sicyases sanguineus and gonad of the keyhole limpet Fissurella spp. (progenetic metacercariae). The mussel Perumytilus purpuratus has been suggested as the first intermediate host for this digenean. In a study examining the parasites of S. sanguineus from central Chile, we found specimens of Proctoeces showing significant morphological differences with P. humboldti. To assist in the resolution of the taxonomic identification of these specimens, as well sporocysts obtained from the mussel P. purpuratus from central and northern Chile, phylogenetic studies using DNA sequences from the SSU rRNA, as well the LSU rRNA and Cox 1 gene were performed. Results showed that the clingfish S. sanguineus is a host for two species of Proctoeces (P. humboldti and P. syciases n. sp.) along the northern and central Chilean coast, without geographic separation; the mussel P. purpuratus is the first intermediate host for P. syciases n. sp. but not for P. humboldti in central and northern Chile. Fissurellids (Archaeogastropoda) along the Chilean coast harbor only progenetic stages of P. humboldti, but there is no evidence of progenesis for P. syciases. The reinstatement of Proctoeces humboldti is strongly suggested.

Research using parasites infish population studies in the South Eastern Pacific (SEP) is summarized. There are 27 suchstudies (snapshots mainly) in single host species sampled at different geographic localities and at somewhat similar times.They have been devoted mainly to economically important species, though others on coastal and intertidalfish or on less- ornon-commercial species provide insights on scales of temporal and spatial variation of parasite infracommunities. Later, weassess whether the probability of harbouring parasites depends on the host species body size. Our results indicate that astronger tool forfish population studies may be developed under regular (long term) scrutiny of parasite communities,especially of smallfish host species, due to their larger variability in richness, abundance and total biomass, than in largefishspecies. Finally, it might also be necessary to consider the effects offishing on parasite communities as well as the naturaloscillations (coupled or not) of host and parasite populations.

The coasts of central Chile and central California are important points of comparison in the study of ecological convergence such as a host’s parasite load because of their similar environmental conditions and the shared presence of many families of different species. In this study, the diversity of parasites in fish species from both zones was analyzed and compared to establish if there are similarities between them. The presence of 6 taxonomic groups of parasites was determined using published literature and databases for each location. A presence-absence matrix was created for the fish species studied in Chile and California, and a similarity analysis was carried out to prove whether the parasite loads of both zones were similar. The parasite taxa most frequently found in fish in central California were Digenea and Nematoda, whereas in central Chile the common taxa were Digenea, Annelida, Copepoda, Acanthocephala, and Nematoda. The similarity analysis showed that the parasite composition was different between zones. Nevertheless, overlaps were obtained in the parasitic diversity grouping the host in 3 host groups, one of which consists of hosts from both zones. This difference can be explained by the low parasitic diversity in the assemble of rocky intertidal fishes in California, potentially due to the limited amount of existing studies on intertidal fish parasites in California, along with other possible factors not explored in the present study.

Biological interactions and environmental constraints alter life-history traits, modifying organismal performances. Trematode parasites often impact their hosts by inducing parasitic castration, frequently correlated with increased body size in the host (i.e., gigantism hypothesis), which is postulated to reflect the re-allocation of energy released by the reduction in the reproductive process. In this study, we compared the effect of a trematode species on shell size and morphology in adult individuals of the intertidal mussels Perumytilus purpuratus (>20 mm) collected from two local populations of contrasting environmental regimes experienced in central-southern Chile. Our field data indicates that in both study locations, parasitized mussels evidenced higher body sizes (shell length, total weight and volume) as compared with non-parasitized. In addition, parasitized mussels from the southern location evidenced thinner shells than non-parasitized ones and those collected from central Chile, suggesting geographical variation in shell carbonate precipitation across intertidal habitats of the Chilean coast. In laboratory conditions, mussels collected from a local population in central Chile were exposed to two temperature treatments (12 and 18 °C). Parasitized mussels showed higher growth rates than non-parasitized, regardless of the seawater temperature treatments. However, the metabolic rate was not influenced by the parasite condition or the temperature treatments. Our field and laboratory results support the parasite-induced gigantism hypothesis, and suggest that both the thermal environment and geographic location explain only a portion of the increased body size, while the parasitic condition is the most plausible factor modulating the outcome of this host-parasite interaction.

Diplostomatid digeneans are well-known manipulators of the behavior of their intermediate hosts. Unencysted metacercariae of Tylodelphys sp. inhabit the cranial cavity of the fish Galaxias maculatus; however, to date they have not been documented to alter their host behavior. The goal of this study was to evaluate the potential effects of Tylodelphys sp. inhabiting the cranial cavity of Galaxias maculatus on host physiology and swimming behavior as well as its reaction to a simulated predation attempt. Blind experiments in the lab were carried out on 56 fish that were filmed individually. The Fulton condition factor (K) was used as an approximation of nutritional status and a respirometry chamber was used to evaluate oxygen consumption rates of fish. Of the 56 fish, 21 were parasitized by Tylodelphys sp. (mean intensity = 30, range from 1 to 101). Parasitized and non-parasitized fish were similar in condition factor and oxygen consumption rates. Furthermore, the oxygen consumption rate of G. maculatus was not correlated with the abundance of Tylodelphys sp. However, parasitized fish more frequently swam close to the water surface, whereas non-parasitized fish more frequently swam at intermediate depths. When faced with a simulated predator attack, unparasitized fish showed more frequent fleeing behavior as well as a more intense post-fleeing activity. Collectively, these results suggest that Tylodelphys sp. inhabiting the cranial cavity of fish may alter their behavior predisposing them to predation by birds.

Los Digenea son platelmintos parásitos comunes en organismos intermareales, y en sus etapas de vida libre (miracidio y cercaria) están expuestos a distintas condiciones ambientales, al igual que sus hospedadores. Por otro lado, éstos últimos pueden presentar un comportamiento fisiológico diferente si están o no parasitados. En este estudio se evaluó el efecto de la parasitosis por un digeneo, aún no identificado, sobre el consumo de oxígeno del chorito Perumytilus purpuratus, y se analizó la influencia de la temperatura del agua y los ciclos de emersión-inmersión sobre la liberación de las cercarias de estos parásitos. Ejemplares de P. purpuratus fueron recolectaron manualmente desde el roquerío intermareal de la desembocadura del río Biobío, Chile. En el laboratorio se comparó, en experimentos con distintos ejemplares, el consumo de oxígeno de individuos con y sin parásitos, y se midió la liberación de cercarias a 9, 17 y 22°C de temperatura del agua, y según ciclos opuestos de inmersión-emersión de duración variable. El consumo de oxígeno no mostró diferencias significativas entre choritos parasitados y no parasitados. Sin embargo, los ejemplares parasitados mostraron escaso desarrollo gonadal, lo que sugiere una reasignación de los productos metabólicos de los choritos hacia el parásito. La liberación de cercarias aumentó con la temperatura del agua y decreció exponencialmente con la duración de la inmersión-emersión, alcanzando valores máximos en las primeras 2 h de ocurrida la inmersión. Las secuencias opuestas de los ciclos de inmersión-emersión empleadas en los experimentos no influyeron significativamente en el número final de cercarias liberadas. Estos resultados sugieren que el metabolismo del hospedador aumenta con la temperatura, y que la inmersión y la temperatura del agua inducen la liberación de las cercarias.

Los crustáceos tienen un rol importante en el ciclo de vida de los parásitos, ya que actúan como hospedadores intermediarios. No obstante, en Chile y a nivel mundial existen pocos estudios parasitológicos sobre crustáceos que habitan el intermareal rocoso. En este estudio se registró y comparó la carga parasitaria de crustáceos decápodos, y se relacionó con la abundancia de sus hospedadores definitivos (peces y aves). Entre julio y septiembre de 2013 se recolectaron 409 crustáceos, correspondientes a 16 especies, desde el intermareal rocoso de dos localidades de Chile central (33°S), Las Cruces y Montemar. El 65,5% de la muestra estaba parasitada, recolectándose 2.410 metacercarias y 18 nemátodos. Algunas metacercarias correspondían a la familia Opecoelidae, mientras que otras a Microphallidae; los nematodos eran de la familia Cystidicolidae. La mayor prevalencia y abundancia de Microphallidae se registró en Petrolisthes tuberculosus (42,3%; 4,8 ± 11,08 parásitos/crustáceo) y de Opecoelidae en P. violaceus (96,9%; 13,59 ± 17,50 parásitos/crustáceo), mientras que Cystidicolidae fue poco prevalente y abundante en ambas localidades. Las infecciones parasíticas fueron afectadas por la localidad de muestreo, especie y tamaño del hospedador. No se encontró asociación entre la abundancia de los hospedadores definitivos y las cargas parasitarias que presentaban los crustáceos. La nula relación entre las cargas parasitarias y la abundancia de hospedadores definitivos puede ocurrir si estos últimos tienen un amplio espectro trófico o viajan largas distancias, de este modo, la transmisión de los parásitos no sería afectada directamente por la abundancia de los hospedadores definitivos.