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Chromosome patterns of Boophilus annulatus, Boophilus microplus and their F₁ hybrids
Abstract
Chromosome Patterns of Boophilus annulatus, Boophilus microplus and Their F? Hybrids. (May 1969) Weldon H. Newton, B.S., M.S., Texas A&M University Directed by: Dr. Perry L. Adkisson Chromosome patterns in excised gonads from laboratory-reared Mexican Boophilus annulatus (Say), B. microplus (Canestrini) and their reciprocal hybrids F? were studied. Mitotic and meiotic divisions were observed in males of both species, but hybrid males, with a possible exception, exhibited only mitotic cells. Females of both species possessed only mitotic oogonia, with one exception, but hybrid female tissue contained both mitotic and meiotic cells. Both species possessed 10 pairs of autosomes plus one and two near-homomorphic sex chromosomes in males and females, respectively. All chromosomes appeared to possess terminal centromeres. B. annulatus autosomes ranged, from 1.43 to 2.87 microns in length, and the sex chromosomes averaged 7.1 microns in the males and 6.5 and 7.0 microns in the females. Autosomes in B. microplus ranged from 2.29 to 4.86 microns in length, the male sex chromosome averaged 5.58 microns and the near-homomorphic sex chromosomes in females ranged from approximately 1.5X to 4X the length of the autosomes. Sex determination in both species is by an XX:XO mechanism. In both hybrid crosses, ovaries appeared to be normal, but testes were either absent or vestigial. Occasional spermatids were observed in male organ squashes, however, indicating the presence of limited spermiogenic testicular tissue in some specimens. The resolvable male chromosome complements ranged from 2n=19 to 2n=25. The most common was 2n=21 with 20 autosomes and one sex chromosome. Measurable male autosomes ranged from 2.0 to 3.14 microns at metaphase, and the sex chromosome averaged 4.57 microns in length. Hybrid female complements most commonly consisted of 2n=22 with 20 autosomes and two heteromorphic sex chromosomes. Autosomal lengths ranged from 1.71 to 3.43 microns in the two hybrid females. Sex chromosomes in females of annulatus male X microplus female averaged 8.1 and 4.57 microns in length. In the reciprocal hybrid, female sex chromosomes averaged 4.3 and 3.7 microns. Presumably precocious meiosis through anaphase I was observed in female hybrids. At diakinesis, four types of aberrations were observed; namely, improperly paired sex chromosomes, an autosomal trivalent, a dissociated autosomal bivalent and a heteromorphic autosomal bivalent. Occasional spermatozoa were observed in hybrid ovarial squashes indicating successful prior matings.
Description
Ph.D. in Entomology -- Texas A&M UniversitySubject
EntomologyCollections
Citation
Newton, Weldon Harrison (1969). Chromosome patterns of Boophilus annulatus, Boophilus microplus and their F₁ hybrids. Doctoral dissertation, Texas A&M University. Texas A&M University. Available electronically from https : / /hdl .handle .net /1969 .1 /157713.
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