Testicular cells and chromosome of the rice black bug Scotinophara sp. (coarctata group) (Hemiptera: Pentatomidae) sampled from rice fields in Bicol Region [Philippines]
2007
Genil, F.G.dM. | Barrion, A.A. | Villamael, L.N. | Barrion-Dupo, A.L.A. | Barrion, A.T.
Cytogenetic investigation was conducted on the male rice black bug (RBB), Scotinophara sp. (coarctata group), sampled from five areas of the Bicol Region, namely: San Roque, Sangay, Camarines Sur; Tulangan, Matnog, Sorsogon; Bagacay, Gubat, Sorsogon; Balading, Tobaco, Albay; and Nagas Tiwi, Albay. Testes of the Carnoy's fluid-fixed males were extracted and macerated in lacto-aceto-orcein to reveal the spermatogenetic cells during the first and second meiotic divisions. All stages of the reductional and equational meiosis were observed. The most frequently encountered meiotic stage was Prophase I (47.90%) while Anaphase II and Telophase II were the least observed (1.20%). Meiotic indices of Scotinophara sp. ranged from 69.40 to 83.80% and the average index was 79.64%. The average actual lengths of the Pachytene Chromosomes ranged from 0.59 um to 1.37 um and the average relative lengths ranged from 0.09 to 0.21. The autosomes (A) with nucleolus organizing region (NOR) measured 0.17 while the sex (X) chromosomes measured 0.09. Diakinesis chromosomes had average actual lengths of 0.25 um to 0.80 um and the average relative lengths ranged from 0.07 to 0.22. The autosome with NOR measured 0.16 while the X chromosome measured 0.07. The spermatocytes of the testicular cells showed the holokinetic chromosomes of Scotinophara sp. At Diakinesis, the haploid number of homologous chromosomes was either six or seven. The smallest, heterochromatic, unpaired chromosome was the sex(X) chromosome. Thus, the karyotype of the heterogametic male Scotinophara sp. is 2n(male) = 13 (12 A + X0) producing two types of sperms, the n = 7 consisting of 6 univalent (I) A+X and n=6 or 6IA only.
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