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Mammal-eating killer whales (Orcinus orca (L., 1758)) are a rare example of social predators that hunt together in groups of sexually dimorphic adults and juveniles with diverse physiological diving capacities. Day-night ecological differences should also affect diving as their prey show diel variation in activity and mammal-eating killer whales do not rely on echolocation for prey detection. Our objective was to explore the extent to which physiological aerobic capacities versus ecological factors shape the diving behaviour of this breath-hold diver. We used suction-cup-attached depth record- ers (Dtags) to record 7608 dives of 11 animals in southeast Alaska. Analysis of dive sequences revealed a strong bout structure in both dive depth and duration. Day-night comparisons revealed reduced rates of deep dives, longer shallow dives, and shallower long-duration dives at night. In contrast, dive variables did not differ by age-sex class. Estimates of the aerobic dive limit (cADL) suggest that juveniles exceeded their cADL during as much as 15% of long dives, whereas adult males and females never exceeded their cADL. Mammal-eating killer whales in this area appear to employ a strategy of physiological compromise, with smaller group members diving nearer their physiological limits and large-bodied males scaling down their physiological performance. Resume´ : Les orques (Orcinus orca (L., 1758)) mangeurs de mammiferes representent un rare cas de predateurs sociaux qui chassent ensemble dans des groupes d'adultes adimorphisme sexuel et de jeunes et qui possedent des capacites phy- siologiques de plongee differentes. Les differences ecologiques jour-nuit devraient aussi affecter la plongee parce que leurs proies ont une variation journaliere d'activiteet les orques mangeurs de mammiferes n'utilisent pas l'echolocation pour la detection de leurs proies. Notre objectif est d'explorer de quelle maniere le rapport entre les capacites physiologiques aero- bies et les facteurs ecologiques faconne le comportement de plongee de ce plongeur en apnee. Des etiquettes enregistreu- ses de profondeur (Dtags) munies de ventouses nous ont permis d'enregistrer 7608 plongees chez 11 animaux dans le sud- est de l'Alaska. L'analyse des sequences de plongeer evele une forte structure des episodes, tant en ce qui concerne la pro- fondeur que la duree. Les comparaisons jour-nuit montrent un taux reduit de plongees profondes, des plongees peu profon- des de plus longue duree et des plongees de longue duree moins profondes la nuit. En revanche, les variables de la plongee ne different pas en fonction des classes d'age et de sexe. Les estimations de la limite de la plongeea erobie (cADL) laissent croire que les jeunes depassent leur cADL durant jusqu'a ` 15 % des plongees prolongees, alors que les adultes males et femelles n'excedent jamais leur cADL. Les orques mangeurs de mammiferes dans cette region semblent utiliser une strategie comportant un compromis physiologique, dans lequel les plus petits membres du groupe plongent pres de leurs limites physiologiques et les males de grande taille reduisent leur performance physiologique en proportion. (Traduit par la Redaction)

The upper pH tolerance limit of the zebra mussel (Dreissena polymorpha) has not been established experimentally. This study was designed to test the effect of elevated pH on the health and survivorship of zebra mussels. Dishes that contained 250 mL of pond water were assigned to four replicates of control, zebra mussel control, low-NaOH, medium-NaOH, and high-NaOH treatments. Except for the control replicates, two zebra mussels were added to each dish. Every other day, volumes of 1 M NaOH were added to low- (50 μL), medium- (100 μL), and high-NaOH (200 μL) treatments. All zebra mussels but one in the high-NaOH treatment died between days 17 and 31 at pH 9.3-9.5. On the last day of the study, day 31, three zebra mussels in the medium-NaOH treatment died at pH 9.5-9.6. The zebra mussels in the high-NaOH treatment moved and formed byssus attachments less often and had lower mean dry body mass than zebra mussels in other treatments. Dishes that contained zebra mussels had more algal genera than control dishes. In this experiment, the upper pH tolerance limit of zebra mussels was between 9.3 and 9.6 and may have been dependent on the rate of pH change. Resume : Le seuil superieur de tolerance au pH chez la Moule zebree (Dreissena polymorpha) n'a jamais ete etabli experimentalement. Cette etude a ete planifiee avec l'intention d'eprouver les effets d'un pH eleve sur la sante et la survie des Moules zebrees. Des recipients contenant 250 mL d'eau d'etang ont ete utilises, quatre temoins sans Moules zebrees, quatre avec Moules zebrees temoins, quatre avec addition d'une faible quantite de NaOH, quatre avec addition d'une quantite moyenne de NaOH et quatre avec addition d'une forte quantite de NaOH. Sauf dans les recipients temoins, deux Moules zebrees ont ete ajoutees a chaque recipient. Tous les 2 jours, un volume de 1 M NaOH etait ajoute dans chacun des recipients reserves aux traitements au NaOH, faible (50 μL), moyen (100 μL) et fort (200 μL). Toutes les Moules zebrees sauf une sont mortes entre les jours 17 et 31, a pH 9,3-9,5, dans le groupe soumis a une forte dose de NaOH. Le dernier jour de l'etude, jour 31, trois Moules zebrees du traitement a dose moyenne de NaOH sont mortes a pH 9,5-9,6. Les Moules zebrees soumises au traitement a forte dose de NaOH se deplacaient et s'attachaient avec leur byssus moins souvent que les Moules zebrees soumises aux autres traitements et avaient egalement une masse seche moyenne plus faible. Les recipients comptant des Moules zebrees contenaient un nombre plus grand de genres d'algues que les recipients temoins. Dans cette experience, la limite superieure de tolerance des Moules zebrees a ete evaluee a pH 9,3-9,6 et il se peut que ce seuil ait ete relie au taux de changement du pH. (Traduit par la Redaction) Notes 2123

Larval forms of the free-living nematode Caenorhabditis elegans possess the ability to enter a developmental stage which is thought to be specialized for survival in harsh environmental conditions, i.e. the dauerlarval stage. In this study the responses of dauerlarvae to thermal stress and oxygen deprivation are investigated. Oxygen consumption of dauerlarvae is less sensitive to temperature change that that of adults, with Q10 values of 1.7 and 2.6 respectively. The upper thermal tolerance limit of dauerlarvae is also different from that of adults; dauerlarvae survive approximately three times longer than adults when exposed to 37 °C. In addition to differences in thermal tolerance, dauerlarvae survive longer under anaerobic conditions than adults, 7 days and 2 days respectively. On recovery from anaerobic stress dauerlarvae exhibit behavior changes which are suggestive of emergence from the dauerlarval stage. The responses of dauerlarvae to thermal stress and oxygen deprivation appear to be important aspects of the specialization for survival in this facultative developmental stage.

The upper thermal resistance limit (dose–time analysis of mortality at high temperatures) has been determined in the amphipod G. fasciatus on a time scale of up to 5 days. LTm's (median tolerance limit: 50% survival time) show a 1.12 mean multiplication factor for each degree of acclimation between 5 and 25 °C and a mean reduction factor of 2.06 for each degree of exposure between 25 and 38 °C. Toxicity curves relating LTm, acclimation, and exposure temperatures serve to establish short-term survival diagrams that can be used in various situations of thermal shock. Priority should be given to the ΔT (interval between exposure and acclimation temperatures) or its duration. Thus, a 10 °C ΔT seems to be tolerated during an indefinite period of time when the water temperature is 15 °C or less. Predicted survival times are only 2 days and 2 h, respectively, when temperatures reach 20 and 25 °C. The methods used in this study helped to establish some short-term protection criteria for this species. These methods are also applicable to the study of other species or groups of aquatic organisms.[Journal translation]