Embryogenesis and morphology of larval structures in Chlamys hastata : with an examination of the effect of temperature on larval development and factors affecting settlement and metamorphosis
| dc.contributor.author | Cooke, Christine A. | en_US |
| dc.date.accessioned | 2024-08-13T18:11:45Z | |
| dc.date.available | 2024-08-13T18:11:45Z | |
| dc.date.copyright | 1986 | en_US |
| dc.date.issued | 1986 | |
| dc.degree.department | Department of Biology | |
| dc.degree.level | Master of Science M.Sc. | en |
| dc.description.abstract | The early life history of Chlamys hastata, the spiny scallop, from gamete release through metamorphosis to a benthic juvenile, was observed and described. Specimens at different stages of development were prepared for Scanning Electron Microscopy and histological examination to complement live observations. Study of embryology and ontogeny of larval structures revealed many structures previously undescribed for a pectinid species: 1) on two occasions, newly released oocytes were surrounded by a thick jelly coat, 2) elevation of fertilization envelope was very low and only observable in SEM preparations, 3) gastrulation occurred by both epiboly and invagination, 4) a hinge ligament was present in the larval stage, and 5) proviniculum length remained constant throughout larval development. Secretory cells among velar cilia and their probable function in particle collection were described. Growth and survival of the larval stage was examined when reared at 12°, 16°, 19°, 24°C. Larvae reared at 19° and 24°C did not reach competency to metamorphose. Larvae reared at 12°C had 42 % survival by the end of the experiment whereas larvae reared at 16°C had 33 % survival. Larvae reared at 12°C reached a maximum valve length of 238.9 ± 0.93 um and were ready to metamorphose 42 days after fertilization. Larvae reared at 16°C reached a maximum valve length of 231.0 ± 0.84 um and were ready to metamorphose 34 days after fertilization. Throughout development, valve length corresponded to valve height by a linear correlation (r2 = 0.87) with a ratio of 1.11 for length to height. The observed inverse relationship between valve length and developmental time is probably a result of energy partitioning by larvae whereby larvae reared at higher temperatures require more energy to satisfy metabolic needs and so have less available for growth and accumulation of stores. It was observed that C. hastata larvae did not metamorphose after a specified period time, but rather they required a stimulus before the process was initiated. Several types of substrates and chemicals, known to cause other invertebrate larvae to metamorphose, were tested for their effect on causing C. hastata larvae to metamorphose. Percent metamorphosis increased when a fouled surface and/or a water flow was introduced. Larvae appeared to settle and metamorphose preferentially along edges and corners of objects rather than on planar surfaces. They did not settle gregariously. C. hastata larvae could survive without metamorphosing for 103 days at 16°C and 130 days at 12°C. Age of larvae tested influenced the rate of settlement metamorphosis with a reduced response observed as maximum age was reached. A positive correlation between length of the precompetent period of larval life and competent period was observed. | |
| dc.format.extent | 170 pages | |
| dc.identifier.uri | https://hdl.handle.net/1828/17509 | |
| dc.rights | Available to the World Wide Web | en_US |
| dc.title | Embryogenesis and morphology of larval structures in Chlamys hastata : with an examination of the effect of temperature on larval development and factors affecting settlement and metamorphosis | en_US |
| dc.type | Thesis | en_US |
Files
Original bundle
1 - 1 of 1
Loading...
- Name:
- COOKE_Christine_Annette_MSC_1986_85215.pdf
- Size:
- 36.65 MB
- Format:
- Adobe Portable Document Format