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Effects of temperature rise (from 0 to +5°C) and salinity decline (from 34 to 30 psu) on vital biological functions of the Antarctic isopod Serolis polita were studied in laboratory experiments. Behavioural reactions to food odour, as well as righting responses and reburying in the sediments, were measured. Both temperature increase and salinity decline impaired the ability of S. polita to perform these biological functions critical for their long-term survival, by lowering the number of isopods able to right and rebury in the sediment, increasing time-to-right, reducing locomotory activity and weakening isopod reaction to food odour. Significant interactive effects between temperature and salinity on time-to-right and time spent swimming were observed, with isopods being more vulnerable to lower salinities when exposed to higher temperatures. Some biological functions (righting, reburying) were more sensitive to temperature and salinity changes than others (swimming). In conclusion, our findings strongly suggest that Antarctic isopods are vulnerable to environmental changes, and their ability to cope with them is limited.

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.

[Underwater field observations were made by SCUBA divers to document the behaviour of scavengers gathering around food sources in the near-shore part of an Arctic fjord (Gronfjorden, Spitsbergen). The only species feeding on the baits were the spider crab, Hyas araneus and the whelk, Buccinum sp., although single individuals of the hermit crab, Eupagurus pubescens were seen moving towards the bait. Our data show that individuals of H. araneus distinguish between different types of potential competitors or predators appropriately modifying their behaviour. A gradual response of the crabs to a perceived threat was observed, from no reaction towards the presence of whelks, to aggressive display provoked by the divers. Overt acts of aggression among H. araneus were absent, although smaller individuals were observed retreating from the bait earlier than the larger ones. Des observations sous-marines ont ete realisees par des plongeurs afin d'apporter des informations sur le comportement des charognards presents autour des sources de nourriture dans la partie cotiere d'un fjord arctique (Gronfjorden, Spitzberg). Les seules especes se nourrissant sur les appâts etait l'araignee de mer Hyas araneus et le buccin, Buccinum sp., bien que des individus isoles du pagure Eupagurus pubescens aient ete observes se dirigeant vers l'appât. Nos donnees montrent que les individus de H. araneus distinguent entre differents types de competiteurs potentiels ou de predateurs en modifiant leur comportement de facon appropriee. Une graduation dans les reponses des crabes face a une menace a ete observee, de l'absence de reaction a la presence des buccins, jusqu'a la manifestation d'agressivite provoquee par les plongeurs. Des reactions d'agression caracterisees chez H. araneus n'ont pas ete observees, meme si des individus plus petits ont ete vus quittant l'appât plus tot que les plus grands., Underwater field observations were made by SCUBA divers to document the behaviour of scavengers gathering around food sources in the near-shore part of an Arctic fjord (Gronfjorden, Spitsbergen). The only species feeding on the baits were the spider crab, Hyas araneus and the whelk, Buccinum sp., although single individuals of the hermit crab, Eupagurus pubescens were seen moving towards the bait. Our data show that individuals of H. araneus distinguish between different types of potential competitors or predators appropriately modifying their behaviour. A gradual response of the crabs to a perceived threat was observed, from no reaction towards the presence of whelks, to aggressive display provoked by the divers. Overt acts of aggression among H. araneus were absent, although smaller individuals were observed retreating from the bait earlier than the larger ones. Des observations sous-marines ont ete realisees par des plongeurs afin d'apporter des informations sur le comportement des charognards presents autour des sources de nourriture dans la partie cotiere d'un fjord arctique (Gronfjorden, Spitzberg). Les seules especes se nourrissant sur les appâts etait l'araignee de mer Hyas araneus et le buccin, Buccinum sp., bien que des individus isoles du pagure Eupagurus pubescens aient ete observes se dirigeant vers l'appât. Nos donnees montrent que les individus de H. araneus distinguent entre differents types de competiteurs potentiels ou de predateurs en modifiant leur comportement de facon appropriee. Une graduation dans les reponses des crabes face a une menace a ete observee, de l'absence de reaction a la presence des buccins, jusqu'a la manifestation d'agressivite provoquee par les plongeurs. Des reactions d'agression caracterisees chez H. araneus n'ont pas ete observees, meme si des individus plus petits ont ete vus quittant l'appât plus tot que les plus grands.]

Chemical cues released from dead or injured organisms constitute important signals informing nearby animals about a feeding possibility. The ability to detect the signal, evaluate its meaning and locate its source can help organisms to exploit food resources efficiently, which is especially important to animals living in environments with limited food supply. Experiments were carried out to study the behavioral responses of several Antarctic benthic invertebrates to fish (Notothenia corriceps) blood. Necrophagous species such as sea stars Odontaster validus and Lysasterias sp., amphipod Waldeckia obesa and nemertean Parborlasia corrugatus responded to fish blood with changes in their behavior. The behavior common to all these species was locomotion directed towards the stimulus source. Behavioral components consistent with food consumption were observed in O. validus and P. corrugatus. The reaction of herbivorous limpets Nacella concinna to fish blood depended on the animal size. Large (>10 mm) limpets showed no behavioral response, whereas small ones (

Antarctic limpets, Nacella concinna, from the Admiralty Bay (King George Island, South Shetlands) for at least part of the year (austral winter) co-exist with predatory sea stars Lysasterias sp. Our laboratory and field experiments established that the presence of Lysasterias sp. or its odour had considerable influence upon their behaviour. Limpets’ responses, consisting of shell mushrooming, shell rotation and flight, were distinctly different from their reaction to other stimuli, such as food and conspecific odours, or mechanical stimulation. Moreover, a significant impact of sea star presence on limpets’ activity was observed, with limpets fleeing to a distance of 60 cm from the predator. Such reactions allow limpets to lower the incidence of sea star predation, but at the cost of presumptive disrupting of foraging and an additional energy expended for locomotion. A visible difference was noted between two limpet populations, with the rockpool limpets responding only after physical contact with being touched by a sea star, and the subtidal ones responding at a distance of up to 20 cm.

Experiments were carried out to study the behavioural and metabolic responses of the Antarctic sea star, Odontaster validus, to different concentration of food signals (glutamic acid, aspartic acid, glicyne, alanine, tyrosine and a mixture of 11 amino acids). Stimulus concentration increase caused a rise in both the percentage of reacting animals and in the reaction intensity. At low stimulus concentration, O. validus reaction consisted of tube foot waving, and only high concentrations elicited a complicated sequence of several types of behaviour. The metabolic rate of small O. validus was more sensitive to chemical stimuli than of large individuals, with small sea stars reacting even to low signal concentration. It can be speculated that small body size can be a factor restricting sea star capabilities and influencing its reaction to chemical signals.

Experiments were carried out to study the behavioural responses of the omnivorous Antarctic sea star Odontaster validus to natural food odour, several single amino acids and their mixtures. Starved sea stars responded to natural food stimulus by rapid rise of metabolic rate, locomotory activity directed towards signal source, cessation of movement after reaching it and initiation of feeding. All single amino acids that were tested were detected by experimental animals, although there were marked differences in the sea stars’ reaction to them. Amino acids with narrow and broad scope of influence were distinguished, with glutamic acid being the most potent sea star stimulant. It was also found that the same sea star reaction (e.g. metabolic rate increase or locomotory activity) can be caused by several different amino acids. The effects of amino acid mixtures were significantly stronger than that of single amino acids, with >80% of animals reaching signal source. O. validus seems well adapted to using both single and complicated food signals in its foraging behaviour.

[Experiments were carried out to study the effects of food signal concentration, animal nutritional status, and signal repetition on behavioural responses of the mud crab, Rhithropanopeus harrisii tridentatus. Starved crabs responded to a food stimulus by maxilliped movements, chela probing, cleaning movements by the first pair of walking legs, and locomotion. A low concentration of the stimulus elicited only detection, medium concentrations triggered far-field food search, and high concentration activated near-field food search. These results indicate that crabs use the stimulus concentration as a source of information about their distance from a food item. Fed animals reacted to a full-strength food stimulus by escaping from the place where such odour was released. No search behaviour was elicited. Such strategy can decrease the risk of encountering predators or cannibalistic conspecifics by animals that are not under the imminent danger of starving. Stimulus repetition had an inhibitory effect on crab behavioural reactions. The degree of blockade was decreasing with the increase in time between successive stimulus applications. These results indicate that crabs may have a learning mechanism, protecting them from repeating useless food search. Des experiences ont ete menees pour etudier les effets de la concentration du signal de nourriture, de l'etat nutritionnel des animaux et de la repetition du signal sur les reponses comportementales du crabe Rhithropanopeus harrisii tridentatus. Les crabes a jeun repondaient a un stimulus nutritionnel par des mouvements de leurs maxillipedes, de leurs pinces, par des mouvements de nettoyage grâce a leur premiere paire de pattes marcheuses et par la locomotion. Une faible concentration du stimulus ne permettait que la detection, une concentration moyenne provoquait la recherche d'une nourriture eloignee tandis qu'une forte concentration activait la recherche d'une nourriture proche. Ces resultats montrent que les crabes utilisent le stimulus de concentration comme source d'information par rapport a la distance d'une source de nourriture. Les animaux nourris reagissaient a un stimulus tres fort de nourriture en fuyant l'endroit ou une telle odeur avait ete liberee. Aucun comportement de recherche n'a ete observe. Une telle strategie peut diminuer le risque de rencontre avec des predateurs ou des congeneres cannibales chez des animaux qui ne sont pas en danger imminent d'etre affames. La repetition du stimulus avait un effet inhibiteur sur les reactions comportementales du crabe. Le degre de bloquage diminuait quand le temps entre deux applications successives du stimulus augmentait. Ces resultats indiquent que les crabes peuvent avoir un mecanisme d'apprentissage, les protegeant d'une repetition de recherche de nourriture inutile., Experiments were carried out to study the effects of food signal concentration, animal nutritional status, and signal repetition on behavioural responses of the mud crab, Rhithropanopeus harrisii tridentatus. Starved crabs responded to a food stimulus by maxilliped movements, chela probing, cleaning movements by the first pair of walking legs, and locomotion. A low concentration of the stimulus elicited only detection, medium concentrations triggered far-field food search, and high concentration activated near-field food search. These results indicate that crabs use the stimulus concentration as a source of information about their distance from a food item. Fed animals reacted to a full-strength food stimulus by escaping from the place where such odour was released. No search behaviour was elicited. Such strategy can decrease the risk of encountering predators or cannibalistic conspecifics by animals that are not under the imminent danger of starving. Stimulus repetition had an inhibitory effect on crab behavioural reactions. The degree of blockade was decreasing with the increase in time between successive stimulus applications. These results indicate that crabs may have a learning mechanism, protecting them from repeating useless food search. Des experiences ont ete menees pour etudier les effets de la concentration du signal de nourriture, de l'etat nutritionnel des animaux et de la repetition du signal sur les reponses comportementales du crabe Rhithropanopeus harrisii tridentatus. Les crabes a jeun repondaient a un stimulus nutritionnel par des mouvements de leurs maxillipedes, de leurs pinces, par des mouvements de nettoyage grâce a leur premiere paire de pattes marcheuses et par la locomotion. Une faible concentration du stimulus ne permettait que la detection, une concentration moyenne provoquait la recherche d'une nourriture eloignee tandis qu'une forte concentration activait la recherche d'une nourriture proche. Ces resultats montrent que les crabes utilisent le stimulus de concentration comme source d'information par rapport a la distance d'une source de nourriture. Les animaux nourris reagissaient a un stimulus tres fort de nourriture en fuyant l'endroit ou une telle odeur avait ete liberee. Aucun comportement de recherche n'a ete observe. Une telle strategie peut diminuer le risque de rencontre avec des predateurs ou des congeneres cannibales chez des animaux qui ne sont pas en danger imminent d'etre affames. La repetition du stimulus avait un effet inhibiteur sur les reactions comportementales du crabe. Le degre de bloquage diminuait quand le temps entre deux applications successives du stimulus augmentait. Ces resultats indiquent que les crabes peuvent avoir un mecanisme d'apprentissage, les protegeant d'une repetition de recherche de nourriture inutile.]

In the last 50 years a significant climatic shift has been observed along the Antarctic Peninsula (air and seawater temperature rise, glacial retreat, localized instances of lowered shallow waters salinities). Many Antarctic marine benthic invertebrates are adapted to specific environmental conditions (e.g. low stable temperatures, high salinity and oxygen content). Changes caused by global climate changes and subsequent glacial melting can be expected to have significant impacts on species physiology and distribution. The rise of sea water temperature coupled with such additional stress factors as melt water run-off, increased ice disturbance, disruption of food webs or invasion of alien species can be a serious problem for their long-term survival.

Experiments were carried out to study the behavioural responses of the Antarctic omnivorous starfish Odontaster validus to the chemical signals produced by undamaged conspecifics. Tested starved animals displayed the ability to distinguish between fed and starved conspecifics. Effluents of starved conspecifics were mostly ignored by O. validus, although they showed a strong and complex reaction to the smell of fed ones. This combination of responses may be expected both to decrease the risk of cannibalism in the feeding aggregations typical for O. validus, and to increase foraging efficiency by stimulating the searching behaviour in animals exposed to satiated conspecifics.