Metridia lucens and M. pacifica previously have been differentiated primarily by the structure of the male fifth legs. lucens originally was described to have one large spine on the inner margin of the fourth segment and M. pacifica to have two spines, one each on the third and fourth joints. Some authors have reported M. lucens with two so-called spines on the same segment and M. pacifica also with two such spines but located together on the fourth segment. This led to M. pacifica being questioned as a species by certain authors who claimed it synonymous with M. lucens. In the present study, M. lucens from the Northwestern Atlantic is compared with M. pacifica from the Northeastern Pacific and differences in size and structure are evident to separate them. The fifth pair of legs on adult males and females were examined and findings indicated errors in the original descriptions of both species. Another Metridia population, found in the coastal waters of British Columbia, was compared with the described species. It was found to be similar to M. lucens and could be, in part, the reason for the past confusion between the Atlantic and Pacific species. / Science, Faculty of / Zoology, Department of / Graduate

We compared four metabolic indicators of nutritional state: citrate synthase activity (CS), malate dehydrogenase activity (MDH), lactate dehydrogenase activity (LDH) and percent body protein to each other and to respiration measurements. These comparisons were made for four species of copepods (Calanoides acutus, Metridia gerlachei, Paraeuchaeta antarctica and another form of Paraeuchaeta that was unidentifiable to species due to its early life stage), three species of Euphausids (Euphausia crystallorophias, Euphausia triacantha, Euphausia superba (including both F6-furcilial and adult stages)) and Thysonessa macrura which were collected off the Western Antarctic Peninsula (WAP) during Spring/Summer and Fall/Winter. Most species showed significant changes in one or more of the enzyme activities. In general, species that engage diapause during the Winter months showed a decrease in citrate synthase whereas those that actively feed throughout the year showed no significant changes. There was also evidence of correlations between citrate synthase activity and respiration as well as between malate dehydrogenase activity and respiration. The observed patterns are consistent with existing models of survival strategy for these Antarctic species.

Les copépodes sont au cœur des flux de matière et d'énergie dans les réseaux trophiques arctiques et subarctiques. La structure et les fonctions des communautés de copépodes dépendent de l'assemblage des espèces dont elles sont constituées, mais on en connait très peu sur les interactions interspécifiques qui peuvent influencer ces propriétés. Les copépodes ont la capacité d'ingérer leurs propres œufs et nauplii (cannibalisme) ainsi que ceux des autres espèces (prédation intraguilde). Il est donc possible que ce type de prédation ait le potentiel de contrôler le recrutement et la dynamique des espèces de copépodes. L'objectif principal des travaux de recherche présentés dans ce mémoire de maîtrise était donc de mieux comprendre la dynamique des interactions interspécifiques au sein des communautés de copépodes arctiques et subarctiques et plus précisément, la prédation intraguilde soupçonnée de façonner ces communautés. Des expériences en laboratoire ont permis de caractériser la prédation intraguilde de l'espèce arctique Metridia longa sur les œufs d'une autre espèce arctique Calanus hyperboreus, ainsi que la prédation intraguilde de cette dernière sur les œufs de l'espèce subarctique Calanus finmarchicus. Différentes conditions de température, concentration d'œufs et nourriture alternative ont été testées. Parmi les conditions d'incubation testées et les différences individuelles dans les traits des prédateurs (par ex. longueur du prosome, stade de développement), seulement la concentration des œufs a eu un effet significatif et positif sur l'ingestion des œufs, et ce pour les deux relations étudiées. Environ un quart des prédateurs incubés ont rempli plus de la moitié de leurs besoins métaboliques avec l'ingestion des œufs seulement. Par la suite, un modèle de distribution verticale des œufs de C. hyperboreus dans le Golfe d'Amundsen a été développé avec l'intégration de la prédation de M. longa afin de vérifier les implications écologiques de cette interaction interspécifique. Nos résultats montrent une relation asymétrique où M. longa a peu d'impact sur le recrutement de C. hyperboreus alors que les œufs interceptés par M. longa peuvent représenter une partie importante de ses besoins métaboliques durant l'hiver. Cependant, l'ingestion des nauplii n'a pas été considérée et devrait être étudiée puisque que ces larves représentent également des proies de choix, susceptibles d'être davantage visées. Ainsi l'impact de la prédation intraguilde aurait pu être sous-estimée.

The bathypelagic copepods Spinocalanus brevicaudatus, Scaphocalanus brevicornis and Heterorhabdus tanneri have established relatively large, permanent breeding populations in Bute and Jervis Inlet, British Columbia. They are found only rarely in the shallower Strait of Georgia. The preference shown by Spinocalanus brevicaudatus and Scaphocalanus brevicornis was attributed to the deep living habits of breeding adults. The reason for H. tanneri's preference of deep water was not apparent from the distribution study. Two general patterns of vertical distribution were seen among the calanoid capepods in the inlets. The common interzonal species such as Calanus glacialis preferred a definite depth interval near mid-water. The deep-living species such as Spinocalanus brevicaudatus were found throughout the water column below the thermocline, in about equal numbers. Maximum numbers usually occurred in the depth interval immediately below the thermocline. Only females of Metridia pacifica showed a strong diurnal migration pattern in July. This migration became less intense near the head of Bute Inlet. The vertical distribution and migration patterns of Spinocalanus brevicaudatus, Scaphocalanus brevicornis and H. tanneri appeared to increase the chances of secual encounters in these relativelyt rare species. The interzonal and deep-living species showed contrasting life-histories. The interzonal species exhibited a well-defined breeding season, with adults maturing in the winter, and young appearing in the spring. The deep-living species did not show a yearly breeding cycle. Females dominated the population at all times of year, and a relatively small percentage of males and females were always present. A reduction in the male:female sex ratio occurred during or after the last moult in Spinocalanus brevicaudatus and Scaphocalanus brevicornis. In the animals the male has reduced mouth parts and probably dies soon after mating. H. tanneri males do not have reduced mouth parts. This species had a sex ratio close to unity at all times. An increase in total copepod numbers was observed with increasing distance from the head of Bute Inlet. An increase in the percentage of juveniles in the population of most species was also observed with increasing distance from the inlet head. Spinccalanus brevicaudctus, Scaphocalanus brevicornis and H. tanneri are redescribed. Comantenna columbiae is described for the first time. / Graduate

Dt. Titel: Vorhersagemodelle für den Einfluss von Süßwasser Einstrom auf Salzwasser Schichten, Wanderbewegung und Lebenszyklen des Zooplankton im Arktischen Ozean: Szenarien und Trends in der Zukunft