Cytology of the rice leaf folder, Cnaphalocrocis medinalis (Guenee) (Lepidoptera: Pyralidae)

Date

3-1984

Degree

Bachelor of Science in Biology

College

College of Arts and Sciences (CAS)

Adviser/Committee Chair

Adelina A. Barrion

Abstract

The cytology of the sixth instar larvae of the rice leaf folder, Cnaphalocrocis medinalis (G,), was investigated using the squash technique with lacto-aceto-orcein. The testicular cells of last instar caterpillars were found ideal for cellular and chromosomal investigations. The chromosome number, morphology and behavior of the chromosomes during meiosis were determined and described. The meiotic index of C. medinalis was found to be 2`1.9T %. The chromosome number was observed to vary from n=6 to n-45 with 27 as the predominating haploid chromosome number. Thus the diploid number was 54. Only three frequently encountered meiotic stages were observed - leptotene, pachytene and diakinesis. Two deeply-staining bodies were found contained in the nucleus during the leptotene and pachytene stages. One was the nucleolus and the smaller heteropycnotic body was the sex chromosome. There were also some cells observed which contained only one deeply-staining body in their nucleus. Aside from the dark evenly-stained chromosomes visible during pachynema, thin fiber-like strands were also observed distributed all throughout the nuclear region. The idiogram revealed 27 heterochromatic chromosomes with relative lengths ranging from 18 4-o V. The leaf folder chromosomes did not exhibit a distinct centromeric site. They were observed to contain "diffused centromeres" along the entire length of the chromosomes. The unique karyological features observed in C. medinalis could possibly be attributed to holokineticity of its chromosomes.

Language

English

Location

UPLB Main Library Special Collections Section (USCS)

Call Number

Thesis

Document Type

Thesis

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