A COMPATIVE STUDY OF THE LARVAL. SALIVARY GLAND CHROMOSOMES OF FOUR BLACK FLY SPECIES IN NORTHERN NIGERIA.
A COMPATIVE STUDY OF THE LARVAL. SALIVARY GLAND CHROMOSOMES OF FOUR BLACK FLY SPECIES IN NORTHERN NIGERIA.
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Date
1982
Authors
KUMARAKULATUNGAM, PRIYADARSHINI.
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Abstract
The gross morphological characteristics of larval salivary
gland chromosomes of four black fly species namely S.sirbanum,
S .hargreavesi. S.adersi and S .ruficorne were studied using
S.sirbanum as a standard. The landmarks used for this comparison
were arm ratios, the degree of pairing, the expanded region, the
nucleolar organiser, the "double bubble", the Balbiani Ring, the
Para Balbiani, the "blister", homologous hands and chromosome ends.
The arm ratios were found to be constant among all the four
species while the TCL varied. The position and expression of
the expanded region, the nucleolar organiser, the Balbiani Ring,
the Para Balbiani and the "blister" were found to be characteristic
of each species. The nucleolar organiser was found to occur both
heterozygously and homozygously. From the position of the
nucleolar organiser in S.ruficorne it is evident that the nucleolar
organiser is involved in a shift. The occurence of a pericentric
inversion is another possible explanation. Possible reasons for
the position of the nucleolar organiser in S Adersi have been
discussed. The expression of the Balbiani Ring, the "double
bubble", the Para Balbiani and the "blister" were found to be
interspecifically and intraspecifically variable. Reasons for
such variations were discussed. The positions of the Balbiani
Ring and the Para Balbiani among species indicate the presence of
interspecific structural rearrangements. The presence of complex
interspecific heterozygous rearrangements were observed only in
S .ruficorne.
Homologies were best detected at the regions adjoining the
centromere and at the chromosome ends in all the four species.
Reasons for the preservation of bands at these two regions were
discussed. The degree of homology are found to be more extensive
at the Ills end in all the four spocies despite the fact that
S.ruficorne belongs to a separate sub-genus. This is indicative
of the conservative nature of evolution in the Similiidae.
Description
Thesis submitted in partial fulfilment of the requirements
for the Degree of Master of Science in the Department of
Biological Sciences, Ahmadu Bello University, Zaria, Nigeria.
Keywords
COMPATIVE STUDY,, LARVAL. SALIVARY GLAND CHROMOSOMES,, BLACK FLY SPECIES,, NORTHERN NIGERIA.