Mitochondrial and nuclear gene sequencing confirms the presence of the invasive sea anemone Diadumene lineata (Verrill, 1869) (Cnidaria: Actiniaria) in Argentina.

Background: Diadumene lineata is one of the most widespread sea anemone species worldwide. Although this species has been reported a few times on the Argentine coast since 2004, its identification has traditionally been based on external morphological characteristics, and in most cases no voucher specimens are available to support previous records. Methods: In this study, we obtained DNA sequences of two mitochondrial markers (12S and 16S) and two nuclear markers (18S and 28S) from specimens of D. lineata collected in two locations on the Argentine coast separated by almost 800 km. Additionally, we conducted an analysis of the morphology, as well as the types and size ranges of cnidae, using specimens collected at three different locations along the Argentine coast. Furthermore, since introduced populations of D. lineata are presumably ephemeral and only reproduce asexually outside their native range, we examined the internal anatomy of representatives from the Argentine coast for gametogenic tissue as an indication of whether they might be capable of sexual reproduction. Results: DNA data support our morphological identification, including cnidae analyses, of the specimens as D. lineata. Furthermore, all specimens examined were determined to be sterile. Discussion: Genetic sequence comparisons, phylogenetic reconstruction, and cnidae data support the identification of individuals of D. lineata from Mar Chiquita and Garipe Beach, confirming the presence of the species on the Argentine coast using both morphological and molecular tools. The absence of fertile specimens suggests that each sampled population is likely reproducing only by asexual reproduction and possibly composed of clones. The presence of an additional category of longer p-mastigophores B2a in the actinopharynx and filaments, as well as holotrichs in the column, is also reported. Conclusions: For the first time, we have confirmed the presence of D. lineata in Argentina through molecular data. Additionally, our findings indicate that the analyzed specimens are sterile, suggesting that this species is not engaging in sexual reproduction in the studied localities. It is crucial to continue monitoring the populations of D. lineata along the Argentine coast to assess whether they establish sexual reproduction, expand their distribution range or disappear, or potentially cause any harm to local species or alterations in benthic communities.

Heart urchins from the depths: Corparva lyrida gen. et sp. nov. (Palaeotropidae), and new records for the southwestern Atlantic Ocean

Introduction: Sea urchins in the order Spatangoida are the most diverse group of extant echinoids. Objective: Describe a new genus and species of Spatangoida from abyssal depths, and add new records for known species. Methods: Specimens were collected during several cruises at different areas of the southwestern Atlantic Ocean (SWAO), among 37-55° S latitude at depths ranging from 55 to 3 000 m. We present morphological and ultrastructure analyses. Results: Corparva lyrida gen. et sp. nov. (Palaeotropidae) is described from the Mar del Plata Canyon on the Argentine continental slope (2 950 m depth), the first record of this family from Argentina. Corparva gen. nov. differs in having an apical system semi-ethmolytic, and labrum reaching to rear part of second adjacent ambulacral plate. We also report the northernmost distribution and deepest record for Brisaster moseleyi (38° S latitude, 2 212 m depth), the northward extension of the distribution range of Tripylus excavatus (39° S latitude, 74 m depth), and the first record of Abatus philippii and Abatus agassizii at the Burdwood Bank/MPA Namuncurá. Conclusions: The present work brings novel and updated data about the diversity and distribution of spatangoids from the SWAO, including the description of C. lyrida gen. et sp. nov., and new records of species. This shows how much remains to be known about the diversity and distribution of heart urchins in the SWAO, especially from the deep-sea.

Introducción: Los erizos de mar del orden Spatangoida son el grupo más diverso de equinoideos recientes. Objetivo: Describir un nuevo género y una nueva especie de Spatangoida de profundidades abisales, y reportar nuevos registros para especies conocidas. Métodos: Los ejemplares fueron recolectados durante varias expediciones a diferentes áreas del Océano Atlántico sudoccidental (OAS), entre las latitudes 37-55° S y abarcando profundidades desde 55 a 3 000 metros. Presentamos análisis morfológicos y de ultraestructura. Resultados: Corparva lyrida gen. et sp. nov. (Palaeotropidae) fue descripta para el cañón submarino Mar del Plata en el talud continental de Argentina (2 950 m de profundidad), el primer registro de esta familia para Argentina. Corparva gen. nov. difiere en tener un sistema apical semi-etmolítico y labrum que llega a la parte posterior de la segunda placa ambulacral adyacente. También informamos la distribución más septentrional y el registro más profundo para Brisaster moseleyi (latitud 38° S, 2 212 m de profundidad), la extensión hacia el norte del rango de distribución de Tripylus excavatus (latitud 39° S, 74 m de profundidad) y el primer registro de Abatus philippii y Abatus agassizii en el Banco Burdwood/AMP Namuncurá. Conclusiones: El presente trabajo aporta datos novedosos y actualizados sobre la diversidad y distribución de erizos de mar espatangoideos del OAS, incluyendo la descripción de C. lyrida gen. et sp. nov., y nuevos registros para especies conocidas. Esto muestra cuánto queda por conocer sobre la diversidad y distribución de los erizos corazón en el OAS, especialmente de las profundidades marinas.

Nemertean Larval Dispersion Across Biogeographic Provinces of Southwest Atlantic.

The nemertean Malacobdella arrokeana is a commensal of the edible giant bivalve Panopea abbreviata; both species have a restricted geographic distribution, high specificity and populations settled along distinct biogeographic provinces. This supposes a high genetic structuring among populations and low intra-populational variability; nevertheless, a lack of genetic structure was detected previously between M. arrokeana populations from the Atlantic Northern Patagonia Gulfs System (NPGS) by means of mitochondrial and nuclear markers. Here, we present a model that explains this lack of genetic structure, integrating larval development and behavior, as well as bio-oceanographical model simulations. We observed in cultured larvae a maximum 30 days of planktonic life before settlement. Planuliform larval morphology and behavior of M. arrokeana suggested that the dispersion is more influenced by passive transport rather than active swimming. Modeling larvae as particles indicated that the limit of biogeographical provinces along the NPGS is not a barrier for dispersal, corroborating that larval dispersion is strictly related to season and to hydrodynamic diffusion patterns present in the area. These results explain the lack of genetic population structure recorded before in the NPGS. Our results provide novel baseline data regarding larval connectivity and oceanographic circulation patterns on the southwestern Atlantic. This information can be used as a reference for the implementation of management plans of invertebrate species with pelagic larvae to ensure the long-term viability of fishery resources shared by different government districts.

Multiple-biomarker approach in the assessment of the health status of a novel sentinel mussel Brachidontes rodriguezii in a harbor area.

The objective of this study is to analyze whether a combination of biomarkers at different levels of biological complexity could be used to assess the health status of a population of Brachidontes rodriguezii associated to a harbor area in Mar del Plata, Argentina. A battery of biomarkers of general stress was measured in mussels collected from impacted and non-impacted areas. This included: condition index; shell analysis; histopathological alterations; atrophy and integrity of the digestive gland tissue; changes in cell type composition of the digestive gland, and glycogen accumulation. The studied biomarkers were integrated into the Integrative Biological Response (IBR/n) index. Overall, the IBR/n indicated a higher level of stress in mussels located in the harbor area. Thus, this biomarker index is a sensitive analytical tool that could be used to classify the ecotoxicological risk in coastal sites.

Gonadal cycle of Corbicula fluminea (Bivalvia: Corbiculidae) in Pampean streams (Southern Neotropical Region).

Corbicula fluminea is an aggressive invasive species of bivalve that arrived into the Río de la Plata River between the late 60's and early 70's, and dispersed widely throughout the Neotropical region, evidencing a great adaptive flexibility to different environmental conditions. This species is a functional hermaphrodite with larval incubation inside the inner demibranch. Despite its widespread distribution, there are no previous studies of complete gonadal histology and reproductive cycle for this species in the Neotropical region. In this study, the reproductive dynamics of C. fluminea in a temperate region, the Santa Catalina Pampean stream, Argentina, is described. Samples of 20-30 individuals were collected monthly from April 2003-April 2005 and processed using traditional histological techniques. During the two years of this study, seven spawning events were recognized. Three major spawns occurred in spring and summer, and other four minor ones during summer and autumn. Events of oocyte recovery were observed after spawning. A high number of incubating individuals was detected. The results stressed the difficulty of identifying a particular pattern of gamete release and of spawning behaviour in this invasive species, especially when inhabiting an unstable environment.

High energetic cost of oviposition in an edible marine gastropod.

The edible neogastropod Buccinanops cochlidium from Patagonia, Argentina, reproduces by means of egg capsules attached by the female to its own shell. Gravid females lay an outstanding mean of 500,000 eggs that nurse around 800 embryos, which hatch as crawling juveniles (4mm in shell length) after four months of intracapsular development. This reproductive investment could be expressed as the energy content (EC) estimated for the production of a complete egg mass (33.94±12.85 KJ), representing a conservative estimation of the total EC needed for an adult female to spawn, which is in average ∼12% of the total EC in gravid females. This high maternal investment allows a considerable offspring size, which confers them high survival chances. A translocation of energy stored in the foot during the oviposition season is shown in a relative decrease of ∼10% in the foot EC in respect of the total EC (61.8% in non-gravid females vs. 51.3% in gravid females). Gravid females showed significantly higher body wet mass/shell length index and higher total EC than non-gravid females (266.0±66.4 KJ vs. 184.3±69.6 KJ), suggesting that a body condition threshold is required for females to reproduce. These values represent an energetic surplus of over 40% of the total EC per individual when compared to non-gravid females. Protecting gravid females from fisheries would ensure the sustainability of the resource and must be taken into account when establishing fisheries policies.

Malacobdella arrokeana: Parasite or Commensal of the Giant Clam Panopea abbreviata?

We examined trophic relationship between the nemertean Malacobdella arrokeana and its host, the edible geoduck Panopea abbreviata by studying the diets of both species by direct (stomach contents) and indirect methods (stable-isotope analysis of C and N). In addition to these methods, the feeding behavior of M. arrokeana within the host and the morphology of its feeding organs were examined. The feeding behavior of M. arrokeana did not exhibit parasitic characteristics, and the proboscis morphology indicates it is unable to injure host tissues. Analysis of stomach contents revealed a diet consisting mainly of microalgae and diatoms. Panopea abbreviata and M. arrokeana shared similar trophic levels, presenting no differences in the spread of the isotopic niches and high overlap (SEAB overlapped 63%). Consistent with this, our results showed no differences in δ(15)N or δ(13)C values between the two species. The combination of direct and indirect approaches revealed that M. arrokeana has a diet similar to that of its host, confirming a commensal relationship.

Tooth microstructure and feeding biology of the brittle star Ophioplocus januarii (Echinodermata: Ophiuroidea) from northern Patagonia, Argentina / Microestructura dental y biología alimentaria del Ophioplocus januarii (Echinodermata: Ophiuroidea) del norte de Patagonia, Argentina

Abstract Ophioplocus januarii is a common brittle star on soft and hard substrates along the Argentinian and Brazilian coasts. Based on stomach contents, tooth microstructure and field observations we identified its food. Opposed to previous suggestions, O. januarii appears to be a microphagous species feeding on macroalgal fragments (found in 60.0 % of the analyzed stomachs with content), plant debris (28.0 %), animal cuticle structures (13.0 %), and unidentifiable material (30.7 %). Less frequent items found were foraminiferans, ostracods, an amphipod, a juvenile bivalve, and other crustaceans. Electronic microscope revealed digested material, diatoms and small crustacean appendices. Thus, O. januarii is an omnivorous species, feeding mainly on algae, complemented opportunistically with other items. Suspension feeding was observed in the field. It has an fenestrated arrangement intermediate between the previously described uniform and compound teeth. Rev. Biol. Trop. 63 (Suppl. 2): 353-360. Epub 2015 June 01.

Resumen El ofiuroideo Ophioplocus januarii se distribuye a lo largo de las costas de Argentina y Brasil, encontrándose tanto en substratos duros como blandos. En base al análisis de contenidos estomacales y la microestructura de los dientes, junto a observaciones de campo, se describe el comportamiento alimentario de esta especie. Opuesto a suposiciones previas, O. januarii es una especie micrófaga que se alimenta de fragmentos de macroalgas (encontrados en el 60.0 % de los estómagos analizados que presentaban contenido), detritos vegetales (28.0 %), estructuras cuticulares animales (13.0 %) y material inidentificable (30.7 %). Menos frecuente, se encontraron foraminíferos, ostrácodos, un anfípodo, un bivalvo juvenil y otros crustáceos. Pequeñas porciones del material inidentificable fueron analizadas en el microscopio electrónico de barrido, resultando ser material digerido, diatomeas y pequeños apéndices de crustáceos. Así, O. januarii es una especie omnívora, que se alimenta principalmente de algas, complementando su dieta de manera oportunista con otros ítems. Las observaciones de campo revelaron alimentación suspensívora. El análisis de la microestructura del estereoma del diente resultó en un arreglo del tipo fenestrado intermedio, que se encuentra entre los dos tipos de arreglos descriptos hasta ahora, los dientes de tipo uniforme y los compuestos. De estos últimos, el primero ha sido encontrado en especies macrófagas mientras que el segundo se corresponde a ofiuroideos micrófagos. En el presente trabajo, se propone la existencia de un nuevo tipo de arreglo intermedio en la matriz dental de los ofiuroideos.

Benthodytes violeta, a new species of a deep-sea holothuroid (Elasipodida: Psychropotidae) from Mar del Plata Canyon (south-western Atlantic Ocean).

A new species of elasipodid holothuroid, Benthodytes violeta sp. nov., is described from the Mar del Plata Canyon off Buenos Aires Province (around 38ºS-54ºW). It was taken at four locations at depths ranging from 1500 to 1950 m. This new species has a violet gelatinous body of up to 200 mm in length, with eight pairs of dorsal appendages, lateral festooned edges and four rows of tube feet ventrally. Body wall ossicles comprise rods and crosses with three or four arms and a central bipartite apophysis borne on the primary cross; tentacles and gonad deposits comprise rods and crosses with three and four arms. This is the first report of a holothuroid from the Mar del Plata Canyon area.

A new species of Havelockia Pearson, 1903 from the Argentine Sea (Holothuroidea: Dendrochirotida: Sclerodactylidae).

Havelockia pegi sp. nov., is here described from shallow waters of the Argentine Sea. This new species is distinctive in the purple colouration of its tentacles, scarcity of body wall ossicles and the presence of rosette-shaped ossicles in both the introvert and the tentacles. It is not closely related to any of its congenors. This is the first record of a true sclerodactylid from Argentina. Thandarum hernandezi Martinez & Brogger, 2012, described in the family Sclerodactylidae, is now classified in the family Sclerothyonidae.

Assessment of gonadal follicle size in the invading bivalve Limnoperna fortunei (Mytilidae).

Limnoperna fortunei is an invasive gonochoristic and byssate freshwater bivalve originary from Southeast Asia. It shows great adaptive-reproductive ability, so knowledge of the gonadal cycle is an important factor for the prevention and control of this bioinvasion. This species is highly damaging to natural and human environments. We analyzed the distribution and maturity state of reproductive follicles in the mantle of both male and females. Male results are not shown but, in general, they followed the same pattern as that of females. Routine histological techniques included serial longitudinal sections and transversal sections in three body regions (anterior, middle and psoterior). Oocytes with conspicuous nucleoli were measured on both types of sections to estimate the maturity stage in the different regions. ANOVA indicates that there were no significant differences in maturity ratio between the studied regions, so that a small number of sections would render precise results to assess maturity.

Marine biodiversity in the Atlantic and Pacific coasts of South America: knowledge and gaps.

The marine areas of South America (SA) include almost 30,000 km of coastline and encompass three different oceanic domains--the Caribbean, the Pacific, and the Atlantic--ranging in latitude from 12∘N to 55∘S. The 10 countries that border these coasts have different research capabilities and taxonomic traditions that affect taxonomic knowledge. This paper analyzes the status of knowledge of marine biodiversity in five subregions along the Atlantic and Pacific coasts of South America (SA): the Tropical East Pacific, the Humboldt Current,the Patagonian Shelf, the Brazilian Shelves, and the Tropical West Atlantic, and it provides a review of ecosystem threats and regional marine conservation strategies. South American marine biodiversity is least well known in the tropical subregions (with the exception of Costa Rica and Panama). Differences in total biodiversity were observed between the Atlantic and Pacific oceans at the same latitude. In the north of the continent, the Tropical East Pacific is richer in species than the Tropical West Atlantic, however, when standardized by coastal length, there is very little difference among them. In the south, the Humboldt Current system is much richer than the Patagonian Shelf. An analysis of endemism shows that 75% of the species are reported within only one of the SA regions, while about 22% of the species of SA are not reported elsewhere in the world. National and regional initiatives focusing on new exploration, especially to unknown areas and ecosystems, as well as collaboration among countries are fundamental to achieving the goal of completing inventories of species diversity and distribution.These inventories will allow accurate interpretation of the biogeography of its two oceanic coasts and latitudinal trends,and will also provide relevant information for science based policies.

Biomonitoring of TBT contamination and imposex incidence along 4700 km of Argentinean shoreline (SW Atlantic: from 38S to 54S).

The imposex incidence and TBT pollution were investigated along 4,700km of Argentinean coast, including city harbors and proximal zones without marine traffic. We analyzed 1805 individuals from 12 gastropod species, including families Volutidae, Muricidae, Nassariidea, Calyptraidae, Marginellidae, and Buccinidae, and found the imposex phenomenon for the first time in six species. In high marine traffic zones, TBT pollution was registered and the percentage of imposex was high, while these occurrences were null in areas without boat traffic. The species that best reflect the degree of imposex were those inhabiting sandy/muddy or mixed bottoms. TBT determination and imposex incidence indicate that pollution was focused only in ports with high marine traffic or in areas where ship hulls are painted. This is the first report of an imposex-sediment approach to evaluate organotin contamination along the coast of a South American country.