Formation of germ cell cluster in tubuliferan thrips (Thysanoptera) |
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| Institution: | 1. Institute of Biological Sciences, University of Tsukuba, Tsukuba, Ibaraki 305, Japan;2. Biological Laboratory, Fukushima University, Fukushima, Fukushima 960-12, Japan;3. School Education Center, University of Tsukuba, Ohtsuka 3-29-1, Bunkyo-ku, Tokyo 112, Japan;1. Department of Biology, Institute of Zoology, University of Cologne, D-50674, Cologne, Germany;2. Department of Marine Biology, Texas A&M University at Galveston, Galveston, TX, 77554, USA;1. Faculty of Forestry and Wood Sciences, Czech University of Life Sciences Prague, Kamýcká 129, 165 21 Prague, Czech Republic;2. Department of Entomology, National Taiwan University, No. 1, Sec. 4, Roosevelt Road, Taipei 106, Taiwan;1. Department of Entomology, Texas A&M University, College Station, TX 77843-2475, USA;2. Insect Control and Cotton Disease Research Unit, Southern Plains Agricultural Research Center, U.S. Department of Agriculture, College Station, TX 77845, USA;1. Department of Biological Sciences, Sungkyunkwan University, Suwon 440-746, Republic of Korea;2. Division of Biological Science, Graduate School of Science, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8602, Japan;3. Université de Bordeaux, INCIA UMR 5287 CNRS, 33405 Talence, France;4. Samsung Biomedical Research Institute, Department of Anatomy and Cell Biology, School of Medicine, Sungkyunkwan University, Suwon 440-746, Republic of Korea;5. School of Life Sciences, Gwangju Institute of Science and Technology, 261 Cheomdan-gwagiro, Buk-gu, Gwangju 500-712, Republic of Korea |
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| Abstract: | The ovarian structure and oogenesis in the larval stages of 2 tubuliferan species, Bactrothrips brevitubus (Idolothripinae) and Holothrips yuasai (Phlaeothripinae) of the Thysanoptera were examined using ultrathin serial sections, with special reference to the cluster formation of germ cells. No cells identifiable as stem cells were found in the ovarian rudiments of the 1st and 2nd-instar larvae. The clusters of oogonial cells were observed frequently in the 1st-instar, but scarcely in the 2nd-instar larvae: all the oogonial clusters observed were composed of 2 cells. In the 2nd-instar larvae, the ovarian region posterior to the germarium, or the vitellarium, contained both solitary and clustered oocytes. The oocyte clusters were composed of less than 5 cells. The oocytes, located in the posterior region of the vitellarium, were all solitary and at the previtellogenic stages.A protuberance was found in some solitary germ cells. The structure may represent a remnant of the intercellular bridge, previously formed between the germ cells. The number of oocytes composing a cluster is small but does not always fit the 2n-rule. One possible explanation is the accelerated detachment process of oocytes from a cluster. The cluster formation of germ cells has been confirmed in the Tubulifera as well as in the Terebrantia, and this phenomenon can be recognized as a general feature of the panoistic ovaries of the Thysanoptera. |
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