1-6 1 B . M . Al - Chalabi Bull. Iraq nat. Hist. Mus. (2001) 9 (3):1-6 INHERITANCE OF DARK HEAD AND SIPHON IN THE LARVAE OF CULEX QUINQEFASCIATUS SAY Badia’a M. Al-Chalabi Department of Biology, College of Education, University of Al-Qadisiya ABSTRACT A new spontaneous mutation (dh) is described for Culex quinquefasciatus Say. This phenotype was observed in the second generation to cause complete coloration of the head capsule and the siphon of the larvae. This character is mainly detectable in the larval stage and slightly in the adult stage. The reciprocal mass matting between mutants from F2 generation and normal wild type sibs, revealed that the mode of inheritance can be controlled by an autosomal recessive gene(s). This happened for both sexes with slightly variability in their expression. No significant larval mortalities were found in all crosses. INTRODUCTION Culex quinquefasciatus Say a species of pipiens complex is well known, medically important mosquito. It transmits virus diseases in several parts of the world, also it is involved in the epidemiology of Filariasis in many tropical area as well as st. louis encephalitis. Among mosquito species, Culex quinquefasciatus is one of the wildly distributed one in the world. No records on diseases transmitted by this species has been reported for Iraq so far. Several investigators; Chong (1972), Guptavanij & Barr (1979,82) and Vandehey (1967) have studied relationship between the infection agent and the genetics of Culex mosquitoes to provide a basis of control for this species. In Culex pipiens complex. Barr (1975) listed 47 mutants affecting larval, pupal and adult stages. Others; Dubash et al. (1982), Sharma et al. (1977) and Subbaraw &Adak (1978) have also found several mutants. Although a large number of mutations have been reported for this complex there is a striking lack of phenotypic markers for Culex quinquefasciatus which are essential in may genetic studies. Mutants affecting eye and body color extensively studied by Sakai et al. (1980), Shetty & Chowdaiah (1976) and Subbaraw & Adak (1978). In Iraq only two mutants of this species were found to affect larval growth (Ouda et al., 1986 and Ouda & Mehdi, 1988). The purpose of this study is to describe a new spontaneously isolated for this species and its mode of inheritance. MATERIALS AND METHODS Several samples of mosquito larvae were collected and brought from Jadiriyah square/Baghdad in 1992. The samples then reared in the laboratory. The dark head and siphon larvae were isolated from a second generation of an inbreed line. This is considered as a mutant of the larvae. The later caused complete coloration of the head capsule and the siphon. However, the scape of the antenna and an area around the eyes were pale in color. The head capsule of the mutant larva was rather spherical and wider than normal (Fig. 1). This character is mainly detectable in the larval stage and slightly in the adult stage, moreover the mutant larvae were easy to distinguish from normal individuals. Although the 2 Inheritance of dark head larval instars of the mutants were all pigmented, separation of the mutant phenotype was not easily accomplished with first instar due to their size. In order to determine the mode of inheritance, recoprocal mass mating were made between mutants from F2 generation and normal wild type sibs. The egg rafts were isolated and reared as individual families in a half litter plastic dishes. The larvae were fed on rabbit chaw reared in a glass door incubator at 28-1C°. The crosses were reported between individual of three successive generation. RESULTS AND DISCUSSION The breeding scheme Fig(2) shows reciprocal crosses between mutant individual and normal phenotypes. The later is the progeny of mass crosses of mutants for the wild types. The off springs of both crosses had dark head individuals, but had vary little sex linkage to the (dh) gene or sex influenced expressions. This finding is incontrast to results obtained by Vandehey (1967). His results showed that similar phenotype in Culex pipiens is inherited as sex linked-gene. Inbreeding of the progenies of normal phenotype individuals resulted from the crosses for the two generations produced similar ratios of wild to mutant phenotype in both F2 and F3 progenies (Fig. 3). The dark head that yielded from the above inbreeding had fewer individuals in F2 and F3, and their percent were 1.9 and 5.2 respectively. The inbreeding of dark line in two crosses produced few wild phenotype individuals in their F1 and F2. This indicates that the expression of the character is slightly low. When a reciprocal mass mattings between the mutants of F2 generation and the normal wild type sibs, were made few dark head individuals resulted from their F3 progenies (13.9% and 4.3%) in fig. 4. The results presented in table 1 revealed that this phenotype is probably controlled by an autosomal recessive gene (s) with incomplete penetrance in both sexes and with slightly variable expression. The homozygous conditions of the mutant is variable in both sexes, but a phenotype of slow growing larvae was also observed in most families of all generation in various frequencies. Larval mortalities in most of the crosses were not significantly different. To determine the linkage group of the gene(s) and its mode of inheritance, further analysis should be made using large number of follow-up crosses as well as its interaction and/or linkage to other genes that already mapped for this species. Such mutations could be valuable tool for genetic control of this vactor. Fig.1: The mutant larvae C. quinquefasciatus with dark, small and round head capsule ( 5 left ) compared with normal larvae ( 3 right ). 3 B . M . Al - Chalabi 4 Inheritance of dark head Table 1: Summary of crosses showing that dark head and siphon (dh) is a recessive trait with incomplete penetrance and variable expression. Cross Parental phenotype No. of families Progeny phenotype % larval mortality Female Male + dh A dh F1(dhXdh+) 10 441 206 24.9 B F1(dhXdh+) dh+ 9 222 180 29.8 C dh dh 19 37 1485 - D F1(dhXdh+) F1(dhXdh+) 12 678 178 - E + dh 12 605 158 14.2 F dh + 3 173 28 15.1 G F2dh F2dh 6 23 422 4.3 H F2(dhXdh+) dh 2 339 141 16.8 I F2(dhXdh+) F2(dhXdh+) 6 342 142 26.8 J dh F2(dhXdh+) 7 446 73 22.8 K + + 3 198 9 15.2 linkage to other genes that already mapped for this species. Such mutations could be valuable tool for genetic control of this vector. ACKNOWLEDGEMENT Special appreciation is expressed to Dr. Nazar A. Ouda –Department of Biology, Education College for Women, University of Baghdad, also to Dr. Abdulameir Ali Yassen – Department of Biology, College of Education, University of Al-Qadisiya, for their help. LITERATURE CITED Barr, A. R. 1975 Culex. P. 374-375. In: King, R. C. (ed.) Handbook of genetics, 3. Invertebrates of genetic interest. Plenum Press, New York. 874 pp. Cheng, M. L. 1972 The inheritance of pigmented-paddle in Culex pipiens. . M. Sc. thesis, Univ. Calif. Los Angeles, p. ix-79. Dubash, C. J., Sakai, R. K. and Baker, R. H. 1982 Two new body color mutants in the mosquito. J. Heredity, 73: 340-344. Guptavanij, P. and Barr, A. R. 1979 Plum-eye, a marker for the third linkage group in Culex pipiens (Diptera:Culicidae). J. Med. Entomol., 16 (3): 219-222. Guptavanij, P. and Barr, A. R. 1982 Two sex-linked mutants, blond (bl) and maroon eye (mar), in Culex pipiens (Diptera: Culicidae). J. Med. Entomol., 19 (4): 394-398. Ouda, N. A., Al-Chalabi, B. M. and Dikran, B. B. 1986 Observation on slow-growth larvae: A new character in the mosquito Culex quinquefasciatus Say (Diptera: Culicidae). J. Biol. Sci. Res., 17 (1): 211-217. Ouda, N. A. and Mehdi, N. S. 1988 Black larvae a recessive lethal mutation in Culex quinquefasciatus Say. J. Biol. Sci. Res., 19 (3): 675-679. 5 B . M . Al - Chalabi Sakai, R. K., Chaudhry, M. and Baker, R. H. 1980 An EMS-induced mutant, rose eye in Culex quinquefasciatus. J. Hered., 71:136-139. Sharma, V. P., Mani, T. R., Adak, T. and Ansari, M. A. 1977 Colorless eye, a recessive autosomal mutant of Anopheles stephensi. Mosquito News, 37: 667-669. Shetty, N. J. and Chowdaiah, B. N. 1976 Tests for allelism among certain larval colour mutants of Culex quinquefasciatus. Mosquito News, 36 (4): 477-482. Subbaraw, S. K. and Adak, T. 1978 Genetic mapping of a larval colour mutant greenish larva with the help of male linked translocations and ruby-eye marker in Culex quinquefasciatus. Mosquito News, 38 (1): 47-51. Subbaraw, S. K. and Adak, T. 1978Genetic analysis of a larval color mutant, greenish larva, in Anopheles stephensi. Mosquito News, 38 (1): 51-53. Vandehey, R. C. 1967 Inheritance of pigmented larval head capsules in Culex pipiens. Mosquito News, 27 (1): 69-73. 6 Inheritance of dark head Bull. Iraq nat. Hist. Mus. (2001) 9 (3):1-6 Culex quinquefasciatus Say توارث صفة السواد في الرأس والسيفون لبعوضة بديعة محمود الجلبي جامعة القادسية- كلية التربية-قسم علوم الحياة الخالصة وقد لوحظت هذه الصفة الول Culex quinquefasciatusمت وصف طفرة جديدة لنوع البعوض هذه الطفرة التلون الكامل لرأس الريقات والسـيفون بلـون غـامق عـدا الثاين حيث مييزمرة يف اجليل قاعدة قرون االستشعار يف الرأس إضافة إىل كون رأس الريقات الطافرة غالباً اكثر استدارة من رأس ولقـد مت إجـراء تزاوجـات متعاكسـة مجاعيـة بـني األفـراد الطـافرة مـن اجليـل الثـاين . الريقات االعتيادية العتياديـة أظهـرت النتـائج بـان املظهـر املوصـوف قـد يكـون مسـيطراً عليـه بواسـطة جـني أو واألفراد ا جينات جسمية متنحية مع احتمال وجود حالة عدم النفوذ الكامل يف كال اجلنسني وتعبري متغاير .إىل حد ما