|
|
|
|
|
||
|
|||||
| Home Help Feedback Subscriptions Archive Search Table of Contents | |||||
Quarterly Journal of Microscopical Science, Vol s3-105, 123-137, Copyright © 1964 by Company of Biologists
1 Department of Natural History, The University, St. Andrews; present address: Medical Research Council, Radiobiological Research Unit, Harwell, Didcot, Berks.
The material studied consisted of laboratory-bred specimens of 2 species of Prostriata and 8 species of Metastriata.
Ixodes ricinus and I. hexagonus (Prostriata) have XX:XY sex-determining mechanisms with diploid complements of 28 and 26 acrocentric chromosomes respectively. All the species of Metastriata studied have XX:XO sex-determining mechanisms with diploid complements of 21 and 22 chromosomes in males and females respectively. Haemaphysalis leporis palustris is the only species with metacentric chromosomes. Hyalomma spp., Dermacentor andersoni and Haemaphysalis leporis palustris each have X-chromosomes larger than any of the autosomes, whereas Rhipicephalus sanguineus and R. secundus do not have conspicuously large X-chromosomes.
In all the species studied early male meiotic prophase is characterized by a period of growth similar to that of oocytes at first meiotic division. This nuclear growth of the primary spermatocyte is thought to have evolved together with the production of a large-sized spermatozoon.
The structure of the testes and their accessory glands in Ixodes differs significantly from that of the corresponding organs in Metastriata. Ixodes also differs from the other genera studied as regards the splitting of the integument during ecdysis. It is suggested that Ixodes should be given the status of a ‘family’.
