Thesis (Ph. D.)--Johns Hopkins University, 1890. / Cover title. "Reprinted from Studies from the Biological Laboratory, Vol. V. No. 1"--Cover. Includes bibliographical references (p. 71).

Thesis (Ph. D.)--Johns Hopkins University, 1890. / Cover title. "Reprinted from Studies from the Biological Laboratory, Vol. V. No. 1"--Cover. Includes bibliographical references (p. 71).

Thesis (Ph. D.)--Universiteit van Amsterdam, 1957. / Also issued in Beaufortia, v. 6, no. 68. Includes bibliographical references (p. 80-81).

x, 97 p. : ill. A print copy of this thesis is available through the UO Libraries. Search the library catalog for the location and call number. / In all species of pycnogonids (sea spiders) males care exclusively for the offspring, making this group essential for studies on sex roles, sexual selection, and the evolution of parental investment. Unfortunately, little is known about pycnogonid mating patterns, larval development, or the costs associated with parental care. The mating habits of both male and female Achelia simplissima were studied experimentally and reveal that both sexes routinely mate multiple times and have multiple mates. Parental males experience higher frequencies of predator attacks and epibionts and a lower rate of movement as compared with nonparental males. However, parental males are harder to dislodge than nonparental males and suffer no change in feeding frequency as a result of parental care. The external morphology of the first larval stage of Achelia simplissima was described using SEM photos and compared with other larval pycnogonids. Morphological characteristics suggest a "parasitic" mode of postembryonic development. / Committee in Charge: Alan Shanks, Chair; Svetlana Maslakova; Craig Young

Work on the systematics of a large collection of Antarctic Pycnogohida has revealed very forcibly the limitations of existing systems of classification of this group. In an attempt to rectify some of these shortcomings for a monograph on the pycnogonid fauna of the Ross Sea area, the author has been led to seek new characters and character states which will be useful in taxonomy. Virtually nothing is known of pycnogonid behaviour and ecology, and it seems unlikely that additional knowledge in these fields will be forthcoming in the near future. Our knowledge of pycnogonid comparative anatomy and histology is also very slight. However, the Pycnogonida do lend themselves very readily to mensural description of much of their form. It is true that the expressions of some characters are more simply described by the traditional vocabulary of experts in the field (e.g., ovigeral spine shape), but for other characters this self-same vocabulary may be a source of confusion, as, for instance, in the description of proboscis shape. A morphometric study involving: some 160 specimens of three species revealed that certain simple statistical hypotheses on relative growth can readily be proposed. The values to practical taxonomy and the possible functional interpretation of these hypotheses, in the light of existing information on pycnogonid anatomy, are discussed in the following pages. The work was supported by National Science Foundation Grants Numbers G 14107, G 19338, and G 17890. Part of the work was carried out at the USARP Biology Laboratory at McMurdo Sound, Antarctica, and the author wishes to acknowledge his gratitude for the assistance and hospitality given to him by Dr. Donald E. Wohlschlag, the Director of the laboratory.