Müller Gunnar
University of Bremen, Department of Biology (FB 2), D-28359 Bremen, Germany.
J Morphol. 2003 Aug;257(2):171-80. doi: 10.1002/jmor.10117.
In the present article the anatomy and histology of the male genital system of an endeostigmatid mite are described for the first time. The Endeostigmata probably are a paraphyletic group supposed to include the most primitive actinotrichid mites. In Nanorchestes amphibius, the testis comprises a paired germinal region connected with an unpaired glandular region. In the germinal region, spermiogenesis takes place in cysts of a somatic cell containing germ cells representing the same developmental stage. In the lumen of the glandular region, the spermatozoa are stored together with secretions of the glandular epithelium. These secretions are probably involved in the formation of spermatophores. From the glandular region, spermatozoa and secretions are released into the vasa deferentia that histologically can be divided into three sections, beginning with a short paired region with strong circular muscles serving as a sphincter, continuing with a paired proximal zone, followed by a short unpaired distal section. The distal vas deferens leads into the chitinous, unpaired ductus ejaculatorius which is followed by the progenital chamber. The ductus ejaculatorius is composed of a proximal section and a proximal, central, and anterior chamber. It is accompanied by a complex system of muscles and sclerites probably involved in the formation and ejaculation of the spermatophore. A similar organization can also be found in Prostigmata, but not in Oribatida. Anterior to the progenital chamber is located a paired accessory gland that probably produces a lipid secretion. Spermiogenesis is characterized by disintegration of the nuclear envelope, condensation of chromatin, and extensive reduction of the amount of sperm cell cytoplasm. The mature aflagellate, U-shaped spermatozoa are simple in structure and lack mitochondria and an acrosome complex. The results do not support the current view that Nanorchestidae are more closely related to Sarcoptiformes, i.e., Oribatida and Astigmata, than to Prostigmata.
在本文中，首次描述了一种内气门螨雄性生殖系统的解剖学和组织学特征。内气门螨可能是一个并系群，被认为包括最原始的辐螨类螨。在两栖纳氏螨中，睾丸由一对生殖区和一个不成对的腺区相连组成。在生殖区，精子发生在含有处于相同发育阶段生殖细胞的体细胞囊中。在腺区的管腔中，精子与腺上皮的分泌物一起储存。这些分泌物可能参与精荚的形成。精子和分泌物从腺区释放到输精管中，输精管在组织学上可分为三个部分，开始是一个短的成对区域，有强大的环形肌肉作为括约肌，接着是成对的近端区域，然后是一个短的不成对的远端部分。远端输精管通向几丁质化的不成对射精管，射精管后面是生殖前腔。射精管由近端部分和近端、中央和前腔组成。它伴有一个复杂的肌肉和骨片系统，可能参与精荚的形成和射精。在真气门螨中也能发现类似的结构，但在甲螨中则没有。在生殖前腔前方有一对附属腺，可能产生脂质分泌物。精子发生的特征是核膜解体、染色质浓缩以及精子细胞质数量大量减少。成熟无鞭毛的U形精子结构简单，缺乏线粒体和顶体复合体。研究结果不支持目前的观点，即纳氏螨科与甲螨亚目（即甲螨和粉螨）的关系比与真气门螨更密切。
