سرجيات
| سرجيات | |
|---|---|
| |
| Earthworm | |
التصنيف العلمي 
| |
| أصنوفة غير معروفة (أصلحها): | سرجيات |
| Subclasses | |
|
Branchiobdellae | |
السرجيات (الاسم العلمي: Clitellata) هي class of annelid worms, characterized by having a clitellum - the 'collar' that forms a reproductive cocoon during part of their life cycles. The clitellates comprise around 8,000 species. Unlike the class of Polychaeta, they do not have parapodia and their heads are less developed.
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التكاثر
All clitellata are hermaphrodites. During reproduction, the clitellum secretes a coat which hardens. The worm then creeps out backward from the coat and deposits either fertilized zygotes or both ovae and sperm into the coat, which is then packed into a cocoon. The zygotes then develop directly in the cocoon without passing through a larval stage (as opposed to other annelids, e.g. Polychaeta.) This mechanism is considered to be apomorphic (a newly derived characteristic rather than an evolutionarily ancestral one).[2]
التنظيم
According to modern phylogenetic analyses, the Clitellata are considered to be a monophyletic subclade of the polychaetes.
رتب
انظر أيضاً
مراجع
- ^ Manum, S. B.; Bose, M. N.; Sawyer, R. Y. T. (1991). "Clitellate cocoons in freshwater deposits since the Triassic". Zoologica Scripta. 20 (4): 347. doi:10.1111/j.1463-6409.1991.tb00300.x.
- ^ Reichardt (2006): pp.63, 67-68
المراجع
- Erséus, Christer; Wetzel, Mark J. & Gustavsson, Lena (2008): ICZN rules – a farewell to Tubificidae (Annelida, Clitellata). Zootaxa 1744: 66–68. PDF fulltext
- Reichardt, Anna Katharina (2006): Systematische Zoologie.