Chromosome structure in spermatogenesis of Anabolia furcata (Trichoptera)

Abstract

The structure of metaphase chromosomes was analysed in spermatogonia and spermatocytes of the caddis-fly, Anabolia furcata (Trichoptera: Limnephilidae), using ultrathin serial sections and electron microscopy. In metaphase spermatogonia, about 40% of the chromosomal length was covered with a compact kinetochore plate. Subjectively estimated, secondary spermatocytes were not significantly different in this respect. However, in primary spermatocytes, each bivalent showed four kinetochores, two at each poleward surface, connected with the chromosome. The kinetochores were not located at the chromosome portions most proximal to the spindle poles, but attached laterally in a more equatorial position. When the orientation of individual kinetochore plates in metaphase I bivalents was not roughly at right angles with respect to the spindle axis, gaps and holes were visible in the plates. This possibly indicates the presence of compound kinetochores in A. furcata. The center of the bivalents contains less dense material than the periphery. The structural features of chromosomes in this Trichoptera species are very similar to those described in Lepidotera species with a comparable chromosome number. Taken together with similarities in other karyotype characteristics, such as female heterogamety and the lack of chiasmata in female meiosis, this further corroborates the notion that Lepidoptera and Trichoptera have strong phylogenetic affinities.Key words: caddis-fly, metaphase chromosomes, kinetochore, microtubules, spindle.