Dr. George-Nascimento-Failla, Mario

Two new digenean species are described from the intertidal blenny Scartichthys viridis (Valenciennes) (Blenniidae) collected off the coasts of Chile. The digenean Monorchimacradena viridis n. sp. (Lecithasteridae: Macradenininae) differs from the only known species described in the genus, M. acanthuri Nahhas and Cable 1964, in the presence of Drüsenmagen in the caeca, the location of the seminal vesicle between the testis and ovary (anterior to the testis in M. viridis n. sp.), and the pre-ovarian vitellarium. Megasolena littoralis n. sp. (Haploporidae), which is also reported from Scartichthys gigas (Steindachner), differs from the five valid species of Megasolena in that the post-caecal region (from the posterior edge of the caeca to the end of the body) is larger in M. viridis n. sp., meaning that the caeca are shortest in this species. Also, M. littoralis n. sp. is distinguished, from the other congeneric species, in a combination of characteristics, e.g., body length, suckers, pharynx, testes, hermaphroditic sac and sucker-length ratio. Sequences of ITS2 rDNA were generated for specimens of both species from various localities, indicating that it was invariant within the species. This study describes species of Monorchimacradena and Megasolena in Chilean waters, here reported for the first time off the Pacific Coast of South America.

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.

Studies on helminth communities associated with didelphids are scarce; the majority of works have focused at taxonomic level. To increase the ecological knowledge of these host–parasite associations, during March (dry season) of 3 consecutive years (2013–2015) a total of 49 adults of the gray four-eyed opossum (Philander opossum) was collected in the Neotropical portion of Mexico (Agua Fría, Chiapas State) and examined for helminths. The main objectives of this study were to describe the infra- and component communities of helminths associated with P. opossum and to compare the helminth fauna of the Mexican population of this host species with those studied in French Guiana and in other Mexican terrestrial didelphids. The helminthological record of this host consisted of 12 species: 7 taxa of Nematoda, 3 of Trematoda, 1 Cestoda, and 1 Acanthocephala. Eight of the 12 taxa have been previously recorded in Didelphidae and 4 represent accidental infections (Glossocercus sp., Stomylotrema vicarium, Spirura mexicana and Acanthocephala gen. sp.). Diet of hosts is the main structuring factor of the communities (92% of the helminth species were recruited through ingestion). Forty-eight hosts were parasitized by at least 1 helminth species; Rhopalias coronatus was the most prevalent and abundant species in the hosts sampled. No significant differences were found in global prevalence among the helminth species present in all samplings, considering host sex and year. The dominance exerted by R. coronatus led to low values of evenness and diversity at both community levels. No significant differences were observed in composition of helminth species among the 3 sampling years regarding sex. The results of our study showed changes in helminth abundance at infracommunity level; during the first sampling these changes are explained by species with direct life cycle (Viannaia sp. and Cruzia tentaculata), whereas in last 2 surveys the explanation can be attributed to species with heteroxenous life cycles (particularly R. coronatus, Duboisiella proloba, and Turgida turgida). Thirty-three percent of the helminth species recorded in P. opossum in Agua Fría is shared with the other 2 terrestrial species of didelphids sampled in different sites of Mexico: Didelphis marsupialis and Didelphis virginiana. In contrast, samples from French Guiana and Agua Fría, differ in terms of helminth fauna, confirming that the helminth communities of opossum species inhabiting the same locality show higher levels of taxonomic similarity than communities of conspecific marsupials allopatrically distributed.

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.

Eumetazoan parasites in fish larvae normally exhibit large body sizes relative to their hosts. This observation raises a question about the potential effects that parasites might have on small fish. We indirectly evaluated this question using energetic metabolic laws based on body volume and the parasite densities. We compared the biovolume as well as the numeric and volumetric densities of parasites over the host body volume of larval and juvenile-adult fish and the average of these parasitological descriptors for castrator parasites and the parasites found in the fish studied here. We collected 5266 fish larvae using nearshore zooplankton sampling and 1556 juveniles and adult fish from intertidal rocky pools in central Chile. We considered only the parasitized hosts: 482 fish larvae and 629 juvenile-adult fish. We obtained 31 fish species; 14 species were in both plankton and intertidal zones. Fish larvae exhibited a significantly smaller biovolume but larger numeric and volumetric densities of parasites than juvenile-adult fish. Therefore, fish larvae showed a large proportion of parasite biovolume per unit of body host (cm3). However, the general scaling of parasitological descriptors and host body volume were similar between larvae and juvenile-adult fish. The ratio between the biovolume of parasites and the host body volume in fish larvae was similar to the proportion observed in castrator parasites. Furthermore, the ratios were different from those of juvenile-adult fish, which suggests that the presence of parasites implies a high energetic cost for fish larvae that would diminish the fitness of these small hosts.

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.

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.