Réinvestigation de l'ultrastructure du spermatozoïde d' Haematoloechus (Trematoda: Haematoloechidae)

Abstract

en The threadlike spermatozoon of the frog lung fluke, Haematoloechus , shows two patterns of external ornamentation. The first type is anterior and consists of bristles on the membrane that coincide with certain peripheral microtubules. This already exists in the zone of differentiation (ZD) of the young spermatid. The ZD is pinched off from the cytoplasmic mass at the arching-membrane level. The centriolelike body and striated roots are depolymerized. The two centrioles, made up of triplets, and the bristles are retained in the anterior part of the spermatozoon. The second type is more posterior. At this level, the transverse sections of the spermatozoon are asymmetric; only the larger side has peripheral microtubules, arranged in a semicircle around the axoneme, and a thick external crenate layer on its membrane. After several micrometers, this zone ends in an open collar ( collerette ) enclosing the next region of the spermatozoon. Only the part anterior to the collar is motile; on spontaneously breaking off, this region is mobile, although the unbroken spermatozoon is not. After the collar there is a region without microtubules. Then comes the very long middle region with dorsally and ventrally placed microtubules; the nucleus is at the posterior end. This new spermatozoon pattern, with retained ZD and anterior centrioles, resembles what we described earlier in a didymozoid. It probably occurs often in Digenea and perhaps other Platyhelminthes as well.