Coady, L. W. (1973) Aspects of the reproductive biology of Cucumaria frondosa (Gunnerus, 1770) and Psolus fabricii (Düben and Koren, 1846) (Echinodermata: Holothuroidea) in shallow waters of the Avalon Peninsula, Newfoundland. Masters thesis, Memorial University of Newfoundland.
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Populations of the holothurian species Cucumaria frondosa and Psolus fabricii were sampled twice monthly from shallow waters of the Avalon Peninsula, Newfoundland, from August,1971 through August, 1972. Large numbers of both species were also collected and maintained in a free-flowing laboratory seawater system for purposes of general observation and comparative investigation. -- Both species exhibit an annual reproductive cycle. -- The gonads of male and female individuals of both species consist of the same histological elements throughout the year, varying only in width. From outside to inside, these are: visceral peritoneum, nerves, muscles, haemal fluid (lined on either side by an extrahaemal and intrahaemal basal lamina), and germinal epithelium. The cellular components of the gonads of immature individuals are similar. -- The timing and duration of separate histological developments definable as activation, development, maturity, spawning and spent phases of the reproductive cycle, were clearly evident in males of the two species. Active spermatogenesis commenced in early June following the spawning period and continued for approximately six months until the end of November when spermatogenesis slowed as the animals attained maturity. The first indications of spawning occurred in February and spawnings continued until the beginning of May. Spawnings are largely intermittent and completely spent individuals were not evident in any of the histological preparations examined until the latter part of the spawning period. -- Although gametogenic developments through progressive stages of maturation were less clearly evident in females, the two sexes appear to develop at different rates. Whereas the majority of males attained the mature reproductive condition several months prior to spawning, the final maturation divisions of developing oocytes which give rise to fertilizable ova, did not occur until the time of spawning itself. -- There is a marked seasonal variation in the number of accessory cells (nutritive phagocytes) within the lumen of the gonads of both sexes. -- The timing of spawning appears to be more closely related to nutritive factors associated with the spring phytoplankton "bloom" rather than to demonstrable physical parameters of the environment. -- Histological aspects of the reproductive cycle of individuals maintained in the laboratory during the same time period were similar up to the time of spawning. Subsequent to spawning there was a marked depreciation in the rate at which gametogenic activities were renewed. It is felt that the observed difference in recovery rate was due to nutrient deficiences created by the concentrated feeding action of fouling organisms in the piping system of the laboratory's seawater supply. -- Natural populations of Cucumaria frondosa and Psolus fabricii are composed of approximately equal numbers of both sexes. Sexes may be distinguished externally by the appearance of the genital papilla. In females, the opening of the gonoduct to the exterior appears as a single tubular opening whereas in males sperm are released through several openings, each of which appear as minute projections of the genital papilla. -- Gonad index values (ratio gonad volume/total wet weight) in these species do not reflect variations in gonad size. Neither do changes in gonad volume reflect the variable size and/or number of sex cells occurring in the gonad at different times of the reproductive cycle. Pronounced seasonal fluctuations in gonad volume and total wet weight associated with variable food levels at different times of the year give rise to a situation where reproductive developments are best defined histologically.
|Item Type:||Thesis (Masters)|
|Additional Information:||Bibliography: leaves -110.|
|Department(s):||Science, Faculty of > Biology|
|Geographic Location:||Canada--Newfoundland and Labrador--Avalon Peninsula Region|
|Library of Congress Subject Heading:||Sea cucumbers|
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