Long walk home: Magellanic penguins have strategies that lead them to areas where they can navigate most efficiently.

Understanding how animals move in dense environments where vision is compromised is a major challenge. We used GPS and dead-reckoning to examine the movement of Magellanic penguins commuting through vegetation that precluded long-distance vision. Birds leaving the nest followed the shortest, quickest route to the sea (the 'ideal path', or 'I-path') but return tracks depended where the birds left the water. Penguins arriving at the beach departure spot mirrored the departure. Most of those landing at a distance from the departure spot travelled slowly, obliquely to the coast at a more acute angle than a beeline trajectory to the nest. On crossing their I-path, these birds then followed this route quickly to their nests. This movement strategy saves birds distance, time and energy compared to a route along the beach and the into the colony on the I-track and saves time and energy compared to a beeline trajectory which necessitates slow travel in unfamiliar areas. This suggests that some animals adopt tactics that take them to an area where their navigational capacities are enhanced for efficient travel in challenging environments.

Rocky reef biodiversity survey: Punta Pardelas, Argentina.

BACKGROUND: Temperate rocky reefs in the SW Atlantic are productive areas that support highly diverse communities of invertebrates, algae and fishes. Rocky outcrops form complex structures which offer a diversity of microhabitats that lead to a great variety of co-existing species. Subtidal biodiversity within the Natural Protected Area Península Valdés is largely unexplored and studies are mainly limited to fish. A total of 560 high definition photoquadrats from seven rocky reefs (1-25 m depth) at Punta Pardelas were obtained during March 2019. In total, 4491 occurrences were recorded and identified to phyla (n = 2), superclasses (n = 1), classes (n = 5), subclasses (n = 2), orders (n = 2), families (n = 1), subfamilies (n = 1), genera (n = 10) and species (n = 43) levels. This dataset was developed to provide a baseline inventory of Punta Pardelas inside the Natural Protected Area, that was only partially reported more than 50 years ago. Such data represent the first step towards monitoring these less-accessible ecosystems. NEW INFORMATION: Most of the available information about Atlantic Patagonian marine biodiversity is related to rocky intertidal communities or rocky reef fish communities. Despite having more than 4000 km of coastline, in the last 20 years only four studies have focused on subtidal benthic communities from shallow rocky reefs in Argentina (Genzano et al. 2011, Rechimont et al. 2013, Bravo et al. 2015, Bravo et al. 2020a). However, none of them described the epi-benthic community of different surface orientations on the rocky reefs. This dataset includes several surface orientations (i.e. horizontal, vertical, overhang and cave floor) and their microhabitats. We found almost double the number of taxa previously reported for the area. Through stratified sampling of different surface orientations, we recorded species that are often overlooked and thus registered as part of the existing biodiversity. For example, overhang surfaces in our study showed a unique assemblage and a great diversity of sponges. This work will be valuable as baseline information that is currently out of date in Nuevo Gulf rocky reefs.

Heart urchins from the depths: Corparva lyrida gen. et sp. nov. (Palaeotropidae), and new records for the southwestern Atlantic Ocean / Erizos corazón de las profundidades: Corparva lyrida gen. et sp. nov. (Palaeotropidae) y nuevos registros para el Océano Atlántico sudoccidental

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.

The peristomial plates of ophiuroids (Echinodermata: Ophiuroidea) highlight an incongruence between morphology and proposed phylogenies.

The peristomial plates are skeletal components of the interbrachial frame (or mouth frame), which is located below the true mouth of ophiuroids. Whilst the peristomial plates were extensively described and used as diagnostic characters by some early workers, for the past 100 years they have been largely neglected as a taxonomic resource. In this investigation the peristomial plates of 48 species representing 21 families were examined directly, and information on a further 61 species, including representatives of another eight families, was obtained from the published literature. Observations were made with regard to fragmentation state, relative size and orientation of the peristomial plates. Although fragmentation state showed little consistency at any taxonomic level, relative size and orientation segregated a group of families comprising species with relatively small, inclined peristomial plates, viz. Ophiotrichidae, Ophiopholidae, Ophiactidae, Amphiuridae and Ophiocomidae, together with a single hemieuryalid species-Ophioplocus januarii. The distribution of peristomial plate traits was strongly correlated with that of several other character states pertaining to the interbrachial frame. This supported the proposition that two major types of interbrachial frame are present in ophiuroids (designated 'A' and 'B'). Current phylogenies inferred from both morphological and molecular data imply that type B is derived and has evolved independently at least twice in the orders Amphilepidida and Ophiacanthida. This represents a remarkable example of evolutionary convergence. An analysis of the distribution of all interbrachial frame character states suggested that within the Amphilepidida paedomorphosis was probably responsible for the complete reversion of the interbrachial frame to the ancestral type A condition in two families (Ophiothamnidae and Amphilepididae) of suborder Gnathophiurina and possibly responsible for varying degrees of trait reversal in the four families of suborder Ophionereidina. Such paedomorphic events may have been associated with a secondary return to the deep-sea from shallow-sea environments.

Revision of some ophiuroid records (Echinodermata: Ophiuroidea) from Argentina.

The taxonomy of some ophiuroids reported from off Argentina, western Antarctica and the SW Atlantic Ocean is reviewed. The species Amphilepis sanmatiensis, known only from the small holotype, is a synonym of Amphioplus lucyae. This synonymy removes the only reported endemic ophiuroid from Argentina. The species name "Ophiacantha ingrata Koehler, 1923" used for specimens from South Georgia is invalid; the specimens are likely to belong to one of two cryptic species within the O. vivipara complex. Specimens of Amphiura joubini reported from Argentina are re-identified as Amphiura princeps, and specimens of Ophiactis amator from the Antarctic Peninsula are re-identified as Ophiactis asperula.

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.

Histological analysis after arm tip amputation in the brittle star Ophioplocus januarii (Echinodermata: Ophiuroidea) / Análisis histológico luego de la amputación de las puntas de los brazos en Ophioplocus januarii (Echinodermata: Ophiuroidea)

Abstract Wound healing in the arm tip after amputation in the brittle star Ophioplocus januarii was examined in San José gulf, Argentina, to observe histological and morphological changes. The process of wound healing is described and compared with other brittle stars species. This process in O. januarii involves the closure of the wound, the repair of the tissue damage and posterior formation of a presumptive stalked blastema by undifferentiated cells, sclerocytes and presumptive blastemic cells. The sclerocytes are the most abundant cell type due to this cells are crucial to the future skeleton regeneration. The results found in this study support the results found in others brittle stars Rev. Biol. Trop. 63 (Suppl. 2): 297-308. Epub 2015 June 01.

Resumen Se examinaron los cambios histológicos y morfológicos producidos en la punta del brazo de la ofiura Ophioplocus januarii luego de su amputación. En el presente trabajo se describe el proceso de cicatrización de la herida y se lo compara con otras especies de la misma Clase. Este proceso en O. januarii involucra el cierre de la herida, la reparación del tejido dañado y la posterior formación de un presunto blastema formado por células indiferenciadas, esclerocitos y presuntas células blastémicas. Los esclerocitos son las células más abundantes debido a que estas células son cruciales para la regeneración del esqueleto. Los resultados encontrados en este estudio apoyan los resultados que se encuentran en otras estrellas frágiles.

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.

Ultrastructural and cytochemical aspects of the germarium and the vitellarium in Syndesmis patagonica (Platyhelminthes, Rhabdocoela, Umagillidae).

The cytoarchitecture of the female gonad of the endosymbiont umagillid Syndesmis patagonica has been investigated using electron microscopy and cytochemical techniques. The female gonad consists of paired germaria and vitellaria located behind the pharynx in the mid-posterior region of the body. Both the germaria and the vitellaria are enveloped by an outer extracellular lamina and an inner sheath of accessory cells which contribute to the extracellular lamina. Oocyte maturation occurs completely during the prophase of the first meiotic division. Oocyte differentiation is characterized by the appearance of chromatoid bodies and the development of endoplasmic reticulum and Golgi complexes. These organelles appear to be involved in the production of round granules, about 2-2.5 µm in diameter, with a homogeneous electron-dense core surrounded by a granular component and a translucent halo delimited by a membrane. These egg granules migrate to the periphery of mature oocytes, are positive to the cytochemical test for polyphenol detection, are unaffected by protease and have been interpreted as eggshell granules. The mature oocytes also contain a small number of yolk granules, lipid droplets, and glycogen particles scattered throughout the ooplasm. The vitellaria are branched organs composed of vitelline follicles with vitellocytes at different stages of maturation. Developing vitellocytes contain well-developed rough endoplasmic reticulum and small Golgi complexes involved in the production of eggshell and yolk globules. Eggshell globules are round, measure 4-5 µm in diameter, and have a mosaic-like patterned content which contains polyphenols. The yolk globules, 2-3 µm in diameter, show a homogeneous protein content of medium electron density, devoid of polyphenols, and completely digested by protease. The mature vitellocytes also contain glycogen as further reserve material. The presence of polyphenolic eggshell granules in the oocytes and of polyphenolic eggshell globules with a mosaic-like pattern in the vitellocytes have been considered apomorphic features of the Rhabdocoela + Prolecithophora.