Parasite assemblages of whitemouth croaker, Micropogonias furnieri: comparison between marine and brackish waters from the Argentine Sea.

The whitemouth croaker, Micropogonias furnieri, a coastal demersal fish with wide distribution in the Southwest Atlantic Ocean, is a euryhaline species, inhabiting waters with a wide range in salinity. Here, the composition of parasite assemblages of M. furnieri caught along the coastal area off Mar del Plata, Argentina, was described and the infracommunity structure compared with fish from brackish waters to determine variations of its parasite communities due to fish migration between these environments. The relationships between the presence of parasites and the diet and ecological traits of this fish host were discussed. A total of 61 fish from Mar del Plata (MDP) were examined for parasites and compared with previously published data for whitemouth croakers from Mar Chiquita coastal lagoon (MCH), an estuarine system connected to the sea. Corynosoma australe, Dichelyne sciaenidicola, and Neopterinotrematoides avaginata were the most prevalent and abundant species in MDP. Comparisons of infracommunity descriptors showed that fish from MDP harbored a higher number of parasites, as well as richer and more diverse infracommunities than those of MCH. Significant differences occurred in the structure and composition of parasite assemblages of whitemouth croaker from MDP compared to those from MCH, in which Neomacrovalvitrema argentinensis, N. avaginata, Neobrachiella chevreuxii, D. sciaenidicola, and C. australe were the key discriminating species related to these differences. The present study provides comparative data, of great importance for the understanding of parasite-host-environment interactions, particularly in a host that alternates between brackish and marine waters during its life cycle.

Diversity of Empruthotrema Johnston and Tiegs, 1992 parasitizing batoids (Chondrichthyes: Rajiformes and Myliobatiformes) from the Southwest Atlantic Ocean, with description of three new species.

During an extensive research project involving 519 specimens of batoids, including 13 species of Rajiformes and Myliobatiformes (Chondrichthyes) from the Argentine Sea, three new species of Empruthotrema were found and are described using morphologic characteristics and two molecular markers: LSU rDNA and COI mtDNA. The new species can be distinguished from their congeners by the number and distribution of the marginal loculi, the length and morphology of male copulatory organ, and the presence of eyespots. Additionally, multivariate analysis identified the dimensions of the pharynx and ejaculatory bulb as diagnostic features. Host specificity and previous records of the genus in the region are discussed. This is the first description of new species in this genus for the Southwestern Atlantic Ocean, as well as for arhynchobatid hosts.

Morphological and molecular evidence for a new species of Pseudanisakis Layman & Borovkova, 1926 (Nematoda: Ascaridida), parasitizing Rajiformes in southern Southwest Atlantic waters.

Pseudanisakis argentinensis n. sp. is proposed to accommodate parasitic nematodes found in six skate species (Rajidae and Arhynchobatidae) examined from southern Southwest Atlantic waters. The new species differs from its congeners by the following combination of characters: a cupola on each lip, males with 8-12 pairs of precloacal genital papillae, a larger size for both males and females, a greater length-to-breadth ratio of the ventriculus and the presence of a small knob on the tip of the tail. Allometric growth was observed for several morphometric features; however, the slopes of the allometric relationships across host species exhibited non-significant differences and were considered as a strong evidence for conspecificity. Congruent results were obtained after the genetic characterization of the mitochondrial cytochrome c oxidase subunit 1 gene of worms obtained from different skate species, whose values of genetic divergence (1.3) lay within the range of intraspecific variation. Previous records of specimens referred to as Pseudanisakis tricupola in skates from South American waters are regarded as conspecific with P. argentinensis n. sp.

Assessing the role of host traits as drivers of the abundance of long-lived parasites in fish-stock assessment studies.

In order to identify the best tools for stock assessment studies using fish parasites as biological indicators, different host traits (size, mass and age and their interaction with sex) were evaluated as descriptors of cumulative patterns of both parasite abundance and infracommunity species richness. The effect of such variables was analysed for a sample of 265 specimens of Percophis brasiliensis caught in the Argentine Sea. The abundances and species richness were modelled using generalized linear mixed models (GLMMs) with negative binomial and Poisson distribution respectively. Due to collinearity, separate models were fitted for each of the three main explanatory variables (length, mass and age) to identify the optimal set of factors determining the parasite burdens. Optimal GLMMs were selected on the basis of the lowest Akaike information criteria, residual information and simulation studies based on 10 000 iterations. Results indicated that the covariates length and sex consistently appeared in the most parsimonious models suggesting that fish length seems to be a slightly better predictor than age or mass. The biological causes of these patterns are discussed. It is recommended to use fish length as a measure of growth and to restrict comparisons with fish of similar length or to incorporate length as covariate when comparing parasite burdens. Host sex should be also taken into account for those species sexually dimorphic in terms of morphology, behaviour or growth rates.

Homogeneity of parasite assemblages of Dules auriga (Serranidae) in hydrographically heterogeneous sites.

Parasite assemblages of Dules auriga are described for the first time from samples caught during research cruises in two localities of the Argentine-Uruguayan Common Fishing Zone (AUCFZ) and are compared with four additional samples collected by commercial catches from the same region. A total of 178 fish were examined and 13 parasite species were found. This showed low species richness, a condition observed in some other small benthic species at a low trophic level. The composition of the parasite fauna was similar to those found on other host species in the region, sharing the same set of dominant species with other sympatric fishes, which have been identified as both typical and as indicators of this ecoregion: Grillotia carvajalregorum, Corynosoma australe and Hysterothylacium sp. Multivariate similarity analyses at the infracommunity and the component community levels indicated that the two samples caught at different latitudes in the AUCFZ display almost identical parasite assemblages. This repeatability in assemblage structure was also observed across samples from commercial catches. The homogeneity of the parasite assemblages is considered to be an intrinsic property of fish inhabiting the AUCFZ, independent of their ecology and trophic level.

Feeding strategy of juvenile (age-0+ year) Argentine hake Merluccius hubbsi in the Patagonian nursery ground.

Age-0+ year juvenile Argentine hake Merluccius hubbsi (60-150 mm total length, L(T)) from San Jorge Gulf, north Patagonian shelf region of the Argentine Sea, had an almost exclusively pelagic diet dominated by the hyperiid amphipod Themisto gaudichaudii and the euphausiid Euphausia lucens. This suggested that final settlement and permanent demersal habitat utilization might not, as previously reported, occur at earlier sizes (c. 20 mm L(T)). Their feeding strategy involves specialization at a population level towards both the main pelagic prey, indicating a narrow trophic niche. Novel data are provided which contribute to the growing body of information in relation to the age-0+ year transitional stage in demersal fishes and particularly to M. hubbsi recruitment in the Argentine Sea.

Spatial Distribution of Medusa Cunina octonaria and Frequency of Parasitic Association with Liriope tetraphylla (Cnidaria: Hydrozoa: Trachylina) in Temperate Southwestern Atlantic Waters.

This study examined the spatial distribution of the medusae phase of Cunina octonaria (Narcomedusae) in temperate Southwestern Atlantic waters using a total of 3,288 zooplankton lots collected along the Uruguayan and Argentine waters (34-56°S), which were placed in the Medusae collection of the Universidad Nacional de Mar del Plata, Argentina. In addition, we reported the peculiar parasitic association between two hydrozoan species: the polypoid phase (stolon and medusoid buds) of C. octonaria (parasite) and the free-swimming medusa of Liriope tetraphylla (Limnomedusae) (host) over a one-year sampling period (February 2014 to March 2015) in the coasts of Mar del Plata, Argentina. We examined the seasonality, prevalence, and intensity of parasitic infection. Metadata associated with the medusa collection was also used to map areas of seasonality where such association was observed. Cunina octonaria was found from southern Uruguay to the coast of Mar del Plata (34.8-38.2°S, 57.2-54.0°W), with the highest abundances and frequency of occurrence in the Río de la Plata estuary. The parasitic association was identified from the austral warm period (spring-summer season) until mid-autumn. Out of the 21,734 L. tetraphylla specimens that were examined, 316 were parasitized (prevalence = 1.5%) exclusively in the manubrium and gastric peduncle, with an infection intensity of 1 to 2 stolons per host. Furthermore, the medusoid buds per stolon ranged from 11 and 29 at different stages of development. No significant differences were observed between the umbrella diameter of parasitized and non-parasitized L. tetraphylla specimens, nor was any significant correlation identified between umbrella diameter and prevalence, and intensity of infection. According to the aggregation coefficient, C. octonaria had an overdispersed distribution in the host population. All parasitized hosts showed stomach vacuity due to the location of the stolon, which blocked the mouth of the host. We identified the parasitic association in the coasts of Mar del Plata, as well as in both coasts of the Río de la Plata Estuary (Uruguayan-Argentinean coasts). In the Southwestern Atlantic, several biological interactions between medusae and other groups have been identified; however, the specific host selectivity of C. octonaria for L. tetraphylla was not previously identified. Here we discuss the ecological importance of this association during the holoplanktonic life history of the narcomedusae. Additionally, we report the southern limit of the spatial distribution of this particular parasitic association in the Southwestern Atlantic, thus increasing the knowledge of biological associations of gelatinous zooplankton (Cnidaria and Ctenophora) on Uruguayan and Argentinean coasts.

Linking the scientific knowledge on marine frontal systems with ecosystem services.

Primary production hotspots in the marine environment occur where the combination of light, turbulence, temperature and nutrients makes the proliferation of phytoplankton possible. Satellite-derived surface chlorophyll-a distributions indicate that these conditions are frequently associated with sharp water mass transitions named "marine fronts". Given the link between primary production, consumers and ecosystem functions, marine fronts could play a key role in the production of ecosystem services (ES). Using the shelf break front in the Argentine Sea as a study case, we show that the high primary production found in the front is the main ecological feature that supports the production of tangible (fisheries) and intangible (recreation, regulation of atmospheric gases) marine ES and the reason why the provision of ES in the Argentine Sea concentrates there. This information provides support to satellite chlorophyll as a good indicator of multiple marine ES. We suggest that marine fronts could be considered as marine ES hot spots.

Distribution of anisakid nematodes parasitizing rajiform skates under commercial exploitation in the Southwestern Atlantic.

In order to evaluate the infestation by anisakids present in elasmobranchs and their distribution in the Argentine Sea, this study was carried at a regional scale with the following aims: 1) to identify those anisakid species present in skates under exploitation; 2) to characterize quantitatively these infestations and 3) to determine those factors driving the variability in parasite burdens across skate species. A total of 351 skates, belonging to 3 species (218 Sympterygia bonapartii, 86 Zearaja chilensis and 47 Atlantoraja castelnaui) and from different localities of the Argentine Sea were examined for anisakids. Parasites were found in the stomach wall at high prevalence in some samples. Based on morphology and mtDNA cox2 sequences analyses (from 24 larval worms), specimens were identified as Anisakis berlandi, A. pegreffii and Pseudoterranova cattani; the last two known as potentially pathogenic for humans. Differential distribution patterns were observed across parasite and hosts species. In general, fish caught in southern and deeper waters exhibited higher loads of Anisakis spp., whereas infestation levels by P. cattani increase in larger skates. Taking into account that the mere presence of worms or their antigens in fish meat can provoke allergic responses, information on distribution of parasites and their variability is essential for the implementation of food safety practices.

Distribution of Dinophysis species and their association with lipophilic phycotoxins in plankton from the Argentine Sea.

Dinophysis is a cosmopolitan genus of marine dinoflagellates, considered as the major proximal source of diarrheic shellfish toxins and the only producer of pectenotoxins (PTX). From three oceanographic expeditions carried out during autumn, spring and late summer along the Argentine Sea (∼38-56°S), lipophilic phycotoxins were determined by liquid chromatography coupled to tandem mass spectrometry (LC-MS/MS) in size-fractionated plankton samples. Lipophilic toxin profiles were associated with species composition by microscopic analyses of toxigenic phytoplankton. Pectenotoxin-2 and PTX-11 were frequently found together with the presence of Dinophysis acuminata and Dinophysis tripos. By contrast, okadaic acid was rarely detected and only in trace concentrations, and dinophysistoxins were not found. The clear predominance of PTX over other lipophilic toxins in Dinophysis species from the Argentine Sea is in accordance with previous results obtained from north Patagonian Gulfs of the Argentine Sea, and from coastal waters of New Zealand, Chile, Denmark and United States. Dinophysis caudata was rarely found and it was confined to the north of the sampling area. Because of low cell densities, neither D. caudata nor Dinophysis norvegica could be biogeographically related to lipophilic toxins in this study. Nevertheless, the current identification of D. norvegica in the southern Argentine Sea is the first record for the southwestern Atlantic Ocean. Given the typical toxigenicity of this species on a global scale, this represents an important finding for future surveillance of plankton-toxin associations.

Echinoderm diversity in the Southwestern Atlantic / Diversidad de equinodermos del Atlántico suroccidental

Abstract Studies of biodiversity of echinoderms from South America have increased in recent years. Here we summarize sampling done on three expeditions along the Argentinean coast (35º - 55º S) and near the Antarctic Peninsula. The first campaign, Mejillón II (M-II; 2009), was carried out between 35º - 39º S and covered a depth range between 10 to 140 m. The second was part of the Summer Antarctic Campaign 2011 (CAV-III; 2011) that took place around the Antarctic Peninsula, South Shetland and South Orkney Islands (depth range between 67 to 754 m). The last cruise was the final stretch of the Summer Antarctic Campaign 2011 (CAV-IV; 2011), from 39º - 55º S and between 30 - 140 m depth. As result, 74 stations have been studied, of which 68 had at least one echinoderm specimen. From the total number of stations, the occurrence percentages for each class were Asteroidea (68 %), Echinoidea (64 %), Ophiuroidea (55 %), Holothuroidea (51 %) and Crinoidea (20 %). In the M-II campaign, echinoderms were presented in 94 % of the sampled stations, with Echinoidea most frequent (74 %). In the CAV-III campaign echinoderms were presented in all the stations; Ophiuroidea were found in all stations. The lowest occurrence of echinoderms was found in the CAV-IV campaign (82 %), where Asteroidea was present in the 73 % of the samples, and crinoids were absent. Rev. Biol. Trop. 63 (Suppl. 2): 115-120. Epub 2015 June 01.

Resumen En los últimos años se han incrementado los estudios sobre la biodiversidad de equinodermos de Latinoamérica. En el presente trabajo, se exponen los resultados sobre muestras obtenidas en tres expediciones a lo largo de la costa argentina (35 - 55º S) y cerca de la Península Antártica. La primera campaña analizada, Mejillón II (M-II; 2009), se llevó acabo entre 35º - 39º S cubriendo profundidades entre 10 y 140 m. La segunda, parte de la Campaña Antártica de Verano 2011 (CAV-III; 2011), tuvo lugar en el área de la Península Antártica, Shetland del Sur e islas Orcadas del Sur (profundidad entre 67 hasta 754 m). La última expedición analizada en este trabajo fue el último tramo de la Campaña Antártica de Verano (CAV-IV; 2011) desde 39º - 55º S y entre 30 - 140 m de profundidad. Como resultado, 74 estaciones fueron estudiadas, en las cuales en 68 se encontró al menos un espécimen del Phylum Echinodermata. Considerando todas las estaciones, el porcentaje de encuentro para cada clase fue Asteroidea (68 %), Echinoidea (64 %), Ophiuroidea (55 %), Holothuroidea (51 %) and Crinoidea (20 %). En la campaña M-II, los equinodermos estuvieron presentes en el 94 % de las estaciones muestreadas, siendo Echinoidea el más frecuente (74 %). En relación a la Campaña CAV-III, los equinodermos estuvieron presentes en todas las estaciones muestreadas; Ophiuroidea fue la clase más representativa en número de estaciones (100 %). El valor más bajo de aparición de equinodermos fue encontrado en la campaña CAV-IV (82 %), donde Asteroidea estuvo presente en el 73 % de las muestras, y los crinoideos estuvieron ausentes.