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validus Koehler, 1905, Odontaster Odontaster validus Koehler, 1905: 467; 1906: 6, pl. 3, figs 22-26. — Clark 1993: 198. CURRENT STATUS. — Odontaster validus Koehler, 1905. TYPE MATERIAL. — Antarctic • 1 syntype; Booth-Wandel Island; French Antarctic expedition (1903-1905); MNHN-IE-2014-190 • 1 syntype; same as for preceding; MNHN-IE-2014-208 • 1 syntype; Biscoe Bay; same as for preceding; MNHN-IE-2014-397 • 1 syntype; unspecified locality; same as for preceding; MNHN-IE-2014-210 • 1 syntype; same as for preceding; MNHN-IE-2014-212 • 1 syntype; same as for preceding; MNHN-IE-2014-216 • 1 syntype; same as for preceding; MNHN-IE-2014-230. REMARK Koehler (1906) mentioned ten specimens originating from Anvers Island (3), Both-Wandel Island (2), Biscoe Bay (3), Flanders’ Bay (1), and unspecified locality (1)., Published as part of Jangoux, Michel, 2022, The type specimens of extant asteroids (Echinodermata) in the Muséum national d'Histoire naturelle of Paris, pp. 259-334 in Zoosystema 44 (11) on page 322, DOI: 10.5252/zoosystema2022v44a11, http://zenodo.org/record/6616817, {"references":["KOEHLER R. 1905 a. - Note preliminaire sur les echinodermes recueillis par l'expedition antarctique francaise du Dr Charcot (echinides, asterides et ophiures). Bulletin du Museum national d'Histoire naturelle de Paris 11: 64 - 470. https: // www. biodiversitylibrary. org / page / 5034003","KOEHLER R. 1906. - Echinodermes (stellerides, ophiures et echinides). Expedition antarctique francaise (1903 - 1905). Masson, Paris, 41 p. https: // www. biodiversitylibrary. org / page / 951184","CLARK A. M. 1993. - An index of recent Asteroidea. Part 2: Valvatida, in JANGOUX M. & LAWRENCE J. M. (eds) Echinoderm Studies, vol. 4, Balkema, Rotterdam: 187 - 366."]}

One-year time-lapse images acquired via an autonomous photo imaging device positioned at a depth of 20 m in Tethys Bay (Ross Sea, Antarctica) on a rocky bottom colonized by the sponge Mycale (Oxymycale) acerata were analysed. Monthly changes in the abundance and activity of the sea star Odontaster validus and sea urchin Sterechinus neumayeri on the sponge and nearby rocky bottom were compared with respect to environmental variables such as pack-ice presence/absence, temperature, salinity and photosynthetically active radiation. Sea urchins were more abundant on the rocky bottom and sponge during the summer and winter, respectively. Sea stars showed a decrease in the number of individuals on the sponge from January to December. The grazing activity of both species reached its maximum in January–April, when increased sunlight contributed to the phytoplankton bloom. The winter months were critical both for O. validus and S. neumayeri; although the red sea star maintained its pattern of activity on the rocky bottoms in terms of searching for food, the sea urchin reduced its activity. Time-lapse monitoring systems coupled with physicochemical sensors showed potential for revealing species behaviour in polar environments, contributing to the elucidation of future changes in coastal communities facing climate change.

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The importance of intraspecific social behaviors in mediating foraging behaviors of marine invertebrate keystone predators has received little attention. In laboratory investigations employing time-lapse video, we observed that the keystone Antarctic sea star Odontaster validus dis- plays frequent agonistic arm-fencing bouts with conspecifics when near prey (injured sea urchin). Arm-fencing bouts consisted of 2 individuals elevating the distal portion of an arm until positioned arm tip to arm tip. This was followed by intermittent or continuous arm to arm contact, carried out in attempts to place an arm onto the aboral (upper) surface of the opponent. Fifteen (79%) of the 19 bouts observed occurred near prey (mean ± 1 SE, 13 ± 1.6 cm distance to prey; n = 13). These bouts lasted 21.05 ± 2.53 min (n = 15). In all 5 bouts that involved a large individual (radius, R: distance from the tip of an arm to the center of the oral disk; 45 to 53 mm) competing with either a medium (R = 35 to 42 mm) or small (R = 25 to 32 mm) individual, the large sea star prevailed. The only exception occurred in 2 instances where a medium-sized sea star had settled onto prey and was subsequently challenged by a larger individual. Here, the outcomes were reversed in favor of the medium-sized individuals. These complex social behaviors mediating intraspecific competition for the acquisition of prey by a keystone predator are likely to have significant ramifications in terms of individual fitness, population structure, and community composition.

Cold-blooded Antarctic marine species are highly stenothermal and possibly the most temperature-sensitive group on Earth. Studies to date have produced upper lethal temperatures in the range of 4 to 10 degrees C. Although invertebrates have not been acclimated to temperatures above 3 degrees C, some Antarctic fish have been acclimated to 4 degrees C. Activity competence has been evaluated in several Antarctic marine invertebrates and shown to be very sensitive to temperature, with 50% failures in the range of 1 to 3 degrees C for clams, limpets and scallops. The starfish Odontaster validus is much more capable of coping with elevated temperatures than any of these species. Turning speed increased with temperature, reaching a maximum at 7.5 degrees C. Temperature increase led to a clear hierarchy of response loss in the starfish, with lethal limits occurring at a higher temperature (15 degrees C) than loss of activity (9 degrees C) and loss of feeding competence (Specific Dynamic Action, or SDA) and coelomic oxygen level collapse both occurring at 6 degrees C. The higher temperature limit for activity than coelomic oxygen level could be explained by body design or taxonomic factors, which may also explain the markedly enhanced ability to cope with elevated temperature over other Antarctic marine species. Long-term acclimation and survival up to 6 degrees C should be possible for this species, which is important for species living on the west coast of the Antarctic Peninsula, possibly the fastest warming marine environment on Earth. The markedly higher resistance to elevated temperature and maintenance of function in a common Antarctic predator compared to the abilities of several of its prey species suggests that a warming environment could have dramatic consequences on the community-level ecological balance for large areas of the Antarctic benthos.

The effects of temperature on the behaviour of the Antarctic sea starOdontaster validusMany Antarctic marine benthic invertebrates are adapted to specific environmental conditions (e.g.low stable temperatures, high salinity and oxygen content). Changes caused by global climatic shifts can be expected to have significant impact on their physiology and distribution.Odontaster validus, an ubiquitous, omnivorous sea star is one of the "keystone species" in the Antarctic benthic communities. Laboratory experiments were carried out to study the effect of temperature rise (from 0 to 5°C) on some vital biological functions that sea stars must perform in order to survive in their environment. Parameters such as behavioural reaction of sea stars to food and food odour, locomotory performance and ability to right were measured. Temperature increase significantly impaired the ability ofO. validusto perform these functions (e.g.lowering the number of sea stars able to right, increasing time-to-right, reducing locomotory activity, weakening chemosensory reaction to food and food odour). At temperatures of 4 and 5°C a loss of motor coordination was observed, although at all tested temperatures up to 5°C there were single individuals performing successfully.

Marine organisms in Antarctica are adapted to an extreme ecosystem including extremely stable temperatures and strong seasonality due to changes in day length. It is now largely accepted that Southern Ocean organisms are particularly vulnerable to global warming with some regions already being challenged by a rapid increase of temperature. Climate change affects both the physical and biotic components of marine ecosystems and will have an impact on the distribution and population dynamics of Antarctic marine organisms. To pre- dict and assess the effect of climate change on marine ecosystems a more comprehensive knowledge of the life history and physiology of key species is urgently needed. In this study we estimate the Dynamic Energy Budget (DEB) model parameters for key benthic Antarctic species the sea star Odontaster validus using available information from literature and experiments. The DEB theory is unique in capturing the metabolic processes of an organ- ism through its entire life cycle as a function of temperature and food availability. The DEB model allows for the inclusion of the different life history stages, and thus, becomes a tool that can be used to model lifetime feeding, growth, reproduction, and their responses to changes in biotic and abiotic conditions. The DEB model presented here includes the esti- mation of reproduction handling rules for the development of simultaneous oocyte cohorts within the gonad. Additionally it links the DEB model reserves to the pyloric caeca an organ whose function has long been ascribed to energy storage. Model parameters described a slowed down metabolism of long living animals that mature slowly. O. validus has a large reserve that—matching low maintenance costs- allow withstanding long periods of starva- tion. Gonad development is continuous and individual cohorts developed within the gonads grow in biomass following a power function of the age of the cohort. The DEB model devel- oped here for O. validus allowed us to increase our knowledge on the ecophysiology of this species, providing new insights on the role of food availability and temperature on its life cycle and reproduction strategy., SCOPUS: ar.j, info:eu-repo/semantics/published

Climate changes effects include ocean acidification and, possibly, the alteration of frequency and magnitude of climate events, such as El Ni�o. All environmental global changes are supposed to be a major threat to ecosystem, both terrestrial and marine. Despite the amazing bulk of literature on these last, few efforts have been devoted to polar regions, which are actually likely to be the most fragile environments on the Earth. In this work we want to elucidate the response, to environmental modifications, of three Antarctic benthic macroinvertebrates: the scallop Adamussium colbecki, the sea urchin Sterechinus neumayeri and the sea star Odontaster validus, inhabiting the littoral area of Terra Nova Bay (Ross Sea, Victoria Land). Using long term series, we investigated potential correlation between A. colbecki recruitment and environmental variables (sea ice cover duration and El Ni�o events), reporting that A. colbecki recruitment is not affected by these variables. We also performed a manipulative experiment in the Mario Zucchelli Station to understand the effects of three pH levels (8.16, 7.8 and 7.6) on the three species, investigating the response of hard tissues and of the reproductive system. Results show that S. neumayeri spines are affected by low pH only at nanoscale and only in hardness property, while the shell of A. colbecki is not altered at all. As far as reproductive system, we found a significant effect in the gonado-somatic index and on stage development of A. colbecki, in addition to some damages in the gonad tissue, although not statistically significant. S. neumayeri shows the same disrupt tissue all over ovary and testes, although differences from the control are not statistically significant. Conversely, O. validus does not show any effect of low pH exposure at all. Further investigations are necessary to understand the energy costs of maintenance of the polar organisms and its potential consequence on individual life history and, thus, populations dynamic.

Soft-bottom zoobenthic communities at Terra Nova Bay down to 100 m depth are mainly characterised by the presence of three species, generally occurring together and reaching high values of density: the scallop Adamussium colbecki (Smith 1902), the echinoid Sterechinus neumayeri (Meissner 1900) and the asteroid Odontaster validus Koehler 1911. These three species have a planktotrophic larval behaviour, but differ in terms of extent of gametogenic cycle and in feeding behaviour. The aim of this work is to give a first account of their reproductive conditions at Terra Nova Bay, comparing two following summer seasons, characterised by quite different ice-coverage and, consequently, food availability in the water column. The comparative analysis of the data evidences strong inter-annual differences in the scallop, a suspension-feeding species. In contrast, no significant changes were found in the two echinoderms, suggesting that a 2-year oogenic cycle, coupled with the opportunistic feeding behaviour, allow successful management of inter-annual shortcomings in food supply. On a latitudinal perspective, the comparison between data from McMurdo Sound and Terra Nova Bay shows small (for the echinoderms) or greater (for the scallop) geographical shifts in spawning occurrence.

The phagocytosis and germicidal capacity of Saccharomyces cerevisiae by phagocytic amoebocytes (PA) of the Antarctic starfish Odontaster validus were studied in vivo (after incubation periods of 1, 2, and 4 h) and in vitro (after incubation periods of 1, 2, 4, 8, and 12 h) at 0 degree C. The total number of PA and the phagocytic capacity (PC), phagocytic index (PI), and germicidal capacity (GC) of the PA were calculated. Results showed significant variability of the total PA number in different animals. There was a significant increase in PC and no significant differences in PI and GC for different in vitro incubation times. In vivo, experiments showed no significant difference of PC and PI, but there was a significant increase in GC as incubation periods increased. Comparison between in vitro and in vivo results revealed that PI and PC were significantly higher in vitro and that GC was significantly higher in vivo. The present study shows for the first time the phagocytosis and GC of an Antarctic invertebrate in vivo at low temperature (0 degree C), and the results are comparing with the available literature for echinoderms.