碩士 / 國立臺灣大學 / 海洋研究所 / 100 / Outbreaks of the black cyanobacteriosponge, Terpios hoshinota have been reported in Green Island and Orchid Island, Taiwan since 2006. Because T. hoshinota grows fast and has the ability to kill and overgrow scleractinian corals, the outbreak of T. hoshinota results in serious decrease of coral coverage and biodiversity. Although the outbreak of T. hoshinota has also been reported in Guam and Ryukyu Archipelago (Japan) since 1970s, little is known about its life history and ecology of T. hoshinota, which are essential to understand its outbreak mechanisms and population dynamics after the outbreak. Accordingly, in this study, some reproductive information of T. hoshinota (gametogenesis, embryogenesis and larval release pattern) was examined in Green Island, Taiwan. Intensive sampling and field observation of 2-3 day intervals were performed on 15 tagged colonies as well as haphazardly chosen colonies for 2 months (June 16-August 17) in 2011.
Histological observations revealed some patterns in sexual reproduction of T. hoshinota: (1) spermatogenesis is very short (< 8 days); sperm was released on a semi-lunar cycle around the full moon and new moon, (2) oocytes (< 40 μm) and early embryos were always presented, and (3) mature embryos (length: ~400 µm, width 285 µm) were presented only around the full moon and new moon. The semi-lunar cycle of embryo maturation is also coincided well with larval release timing observed in the field (around the full moon and new moon). One larval release event continued for ~8 days. The semi-lunar cycle of embryo maturation and larval release may be determined by the semi-lunar cycle of sperm-release. Embryogenesis of T. hoshinota was unique and never been reported: (1) embryo at morula stage developed outside the embryo-nursing chamber, which consisted of a single layer of pinacocytes and contained numerous cyanobacteria and maternal sponge cells transferred gradually from adult, (2) and then embryo penetrated into the nursing chamber and underwent blastulation, (3) finally, embryonic cells migrated to the periphery of the nursing chamber, packed all of the cyanobacteria and maternal sponge cells inside, and formed a compact single outer layer to become a mature embryo. Symbiotic cyanobacteria were not found in oocyte, but numerously in central cavity of mature embryo and larvae, suggesting vertical transmission of the symbionts from mother sponges to larvae during embryogenesis.
| Identifer | oai:union.ndltd.org:TW/100NTU05279010 |
| Date | January 2012 |
| Creators | Yu-sin Huang, 黃玉馨 |
| Contributors | Yoko Nozawa, 野澤洋耕 |
| Source Sets | National Digital Library of Theses and Dissertations in Taiwan |
| Language | zh-TW |
| Detected Language | English |
| Type | 學位論文 ; thesis |
| Format | 60 |
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