Thesis (M.S.)--Oregon State University, 1964. / Typescript. Includes bibliographical references (leaves 68-71). Also available online.

Graduation date: 1972

An attempt has been made to experimentally interbreed Atlantic and Pacific populations of the marine calanoid copepod Acartia clausi Giesbrecht. Breeding between individuals from each population produced many successive generations in the laboratory, but interbreeding between populations failed to produce viable offspring. This result is strong evidence that the Atlantic and Pacific populations of A. clausi have diverged enough to become reproductively isolated. Assignment of specific rank to differentiate both populations is suggested. Some morphological and ecological differences between Atlantic and Pacific populations of A. clausi were observed. Further studies are proposed to evaluate the constancy of these differences, and their possible use for the recognition of Pacific and Atlantic A. clausi. Observations are presented on the general problems of copepod culture work. / Graduation date: 1974

The morphology of a rather rare parasitic copepod was studied. Ismaila monstrosa Bergh, an endoparasitic copepod was found in the nudibranch, Antiopella fusca, at Coos Bay, Oregon. Many anatomical features were found, which were different from previous descriptions. Males were described for the first time. Young males lacked the gonadal lobes found on the dorsal sides of adult males. Both sexes had similar mouthparts, differing only in size. These mouthparts consisted, like those of Splanchnotrophus, of a bifid labrum, a pair of simple mandibles, a pair of maxillae and a triangular labium with side processes. There was only a single pair of maxillae and they are unusual in that they were found to be setigerous and two-jointed. The distal portion of this characteristic maxilla was biramous, the smaller member often obscure. Because of this and other anatomical factors, I proposed a new variety Ismaila monstrosa var. pacifica and a new subfamily, the Ismailinae. Although the female possessed three pairs of lateral appendages, the male lacked these, having only the two pairs of ventral appendages. In the female specimens there were two pairs of ventral appendages or "stomach-arms". The first pair was bifurcate, the second pair trifurcate. In the male specimens the first pair was uniramous and the second pair unequally biramous. The digestive system was found to be incomplete in both sexes. There were no extensions into the "stomach-arms" No portions of either nervous or circulatory systems were found in the sections. The reproductive system was found to be the major one in the body of the parasite. In the adults of both sexes the gonads were in the dorsal and anterior gonadal lobes. The ovaries connected to an extensively ramified oviduct. The lower part of the oviduct connected to the anterior end of the cement glands. A seminal receptacle was found in the female. In the male two testes were seen in the dorsal gonadal lobes. The vas deferens ran into the lower abdomen where spermatophores could be seen. / Graduation date: 1965

A method for measuring food carbon assimilation in the copepod Calanus finmarchicus was developed, using the diatom Ditylum brightwelli as food. The amount of particulate food carbon ingested was determined as the difference between CHN analyzer analyses for particulate food carbon of pre- and post-grazed food suspensions. The fraction of ingested food that was assimilated as organic matter was determined by a modified Conover gravimetric ratio method. This fraction was computed as: U=(F'-E')/(l-E')F' where F' and E' were the ash free dry weight:dry weight ratios of the copepods' food and feces, respectively. The fraction of ingested organic matter assimilated (U) multiplied by the amount of food carbon ingested estimated the amount of food carbon assimilated, assuming that the fraction of organic matter assimilated by the copepods was identical to the fraction of food carbon assimilated. Assimilation fraction determinations agreed well with those in the literature. The consistency in the carbon assimilation rates obtained apparently indicated a seasonal uniformity in absolute food carbon assimilated by adult Calanus. / Graduation date: 1969

Plankton samples for this present study were collected from an area off the southern Oregon coast, extending westward to about 83 kilometers offshore. Over this sampling area, 41 species of adult copepods were identified, including representatives of 26 genera and 17 families. The total abundance averaged 550/m³. Population densities of copepods as a group were found higher inshore than offshore and this distribution was largely determined by four dominant species, that is, Oithona similis, Pseudocalanus minutus, Acartia longiremis, and Acartia clausi. They accounted for approximately 81% of the total copepod abundance. Species diversity had a tendency to increase with distance from the coast. This could be due to the possibilities that the sampling depth was increased offshore, or that the living environment was more stable offshore than inshore. Rank-correlation analysis of the four dominant species, fish eggs, copepod nauplii, euphausiids, and Eucalanus bungii suggest that the positively correlated category includes several pairs, Oithona similis to Pseudocalanus minutus, O. sirnilis to Acartia clausi, A. longiremis to P. minutus, fish eggs to O. similis, A. longiremis to A. clausi, O. similis to copepod nauplii, and fish eggs to copepod nauplii. The negatively correlated category includes three pairs, euphausiids to copepod nauplii, euphausiids to fish eggs, and euphaus lids to O. similis. Results from the correlation analysis of the dominant species relative to temperature, salinity, and distance from shore show that no significant relationship was apparent except that the occurrence of P. minutus was negatively correlated to distance from shore. / Graduation date: 1971

Graduation date: 1974

Thesis--University of Michigan. / Issued in microfilm form in 1962. Includes bibliographical references.

Inaug.-diss.-Basel. / "Extrait de la Revue suisse de zoologie, t. 11, 1903."

Graduation date: 1980