BEDO, D. G. 1986. Polytene and mitotic chromosome analysis in Ceratitis capitata (Diptera; Tephritidae). Can. J. Genet. Cytol.28: 180-188 Polytene chromosomes were found in several larval and pupal tissues of the Medfly, Ceratitis capitata, during a search for chromosomes suitable for detailed cytological analysis. Well-banded highly polytene chromosomes, which could be adequately separated and spread, were found in trichogen cells of the spatulate superior orbital bristles of male pupae. These chromosomes proved suitable for full polytene analysis. Thoracic trichogen cells of both male and female pupae also contain useful polytene chromosomes, although they are considerably thinner and thus more difficult to analyze. Contrasting with those in pupal trichogen cells, the chromosomes in the salivary glands, Malphighian tubules, midgut, hindgut, and fat body of larvae and pupae were difficult to prepare because of high levels of ectopic pairing and chromosome fragmentation. In hindgut preparations partial separation of up to three chromosomes was achieved, but in all other tissues no useful chromosome separation was possible. In trichogen polytene cells, five banded chromosomes and a prominent heterochromatic network associated with a nucleolus are found. The mitotic chromosomes respond to C-and Q-banding and silver staining with considerable variation. This is especially so in the X chromosome, which displays an extensive array of bands following both Q-banding and silver staining. Comparison of Q-banded metaphase and polytene chromosomes demonstrates that the five autosomes are represented by conventional polytene chromosomes, while the sex chromosomes are contained in the heterochromatic net, most of which fluoresces strongly. This suggests that the Q-bands of the mitotic X chromosome are replicated to a greater extent than the nonfluorescent material in polytene cells. This investigation shows C . capitata to have excellent cytological material for both polytene and mitotic analysis. Des chromosomes polytenes ont Ct C observes chez plusieurs tissus larvaires et pupaires de la mouche a fruit mediterranCenne, Ceratitis capitata, au cours d'une recherche visant a trouver des chromosomes convenables pour des Ctudes cytologiques detaillkes. Des chromosomes fortement polytenes et bien marques de bandes, qui ont pu ttre isolCs et CtalCs adkquatement, ont Ct C trouvis dans les cellules trichogenes des soies orbitales supirieures spatulCes des pupes miles. Ces chromosomes se sont avCrCs convenir a une analyse complete des polytenes. Des cellules trichogenes thoraciques, tant de pupes miles que femelles contenaient aussi des chromosomes polytenes utiles, bien qu'ils Ctaient considCrablement plus fins, et donc plus difficiles a analyser. Contrairement aux chromosomes des cellules trichogenes pupaires, ceux des glandes salivaires, des tubules de Malpighi, de I'intestin mCdian et postkrieur, de mtme que du corps gras des larves et des pupes, furent difficiles a prkparer en raison des niveaux ClevCs d'appariements ectopiques...

Polytene chromosome reference maps of the five autosomes of Ceratitis capitata from male pupal orbital bristle trichogen cells are presented and a correlation is established between two of them and the two largest of the five autosomes in the haploid mitotic complement. Characteristic features of each chromosome are described identifying areas that are difficult to analyze and noting the existence of common alternative band expression. A quantitative analysis of the mitotic karyotype of C. capitata indicates that the two smallest autosome pairs cannot be reliably distinguished. This may present problems with future attempts to establish homologies between the remaining mitotic and polytene chromosomes. A comparison of polytene chromosome banding patterns from salivary gland and trichogen cells failed to find any homologous regions, or even to identify homologous chromosomes. The banding differences are not explained by variation in puffing patterns, heterochromatin expression, or polyteny levels, but appear to reflect fundamental differences in banding patterns of the chromosomes in each tissue. Key words: Ceratitis capitata, polytene chromosome map, mitotic chromosome measurements.

Polytene chromosome banding patterns in Simulium ruficorne populations from two island and a continental African locality were analyzed and a standard map was prepared. Distinct arrays of fixed and polymorphic rearrangements characterize unique cytotypes in Santiago Island, Tenerife, and Ivory Coast populations. Sex-chromosome differentiation where an inversion linked to the male determiner marks a Y chromosome also occurs in the Santiago Island population. No sibling species can be defined at present because of the absence of sympatric population samples. Comparison of banding patterns between S. ruficorne and the S. ornatipes–neornatipes species complex in Australia and New Caledonia shows striking similarities. Banding homology is readily established with about 90% of polytene banding recognizable between the two standards. Three inversions are shared between the lineages, further emphasizing their similarity. These results provide independent corroboration of the close relationship between S. ruficorne and S. ornatipes established from conventional taxonomy. The validity of using shared inversions and common breakpoints in phylogenetic comparisons is discussed in relation to the possibility of confusing similar but distinct rearrangements and the inversion-generating role of transposable elements. The possibility of transposable element mediated identical, independently derived, rearrangements seems unlikely, but in all studies the confusion of phylogenies by similar inversions must be carefully considered.Key words: Simulium ruficorne, polytene chromosome, inversion phylogeny.

Polytene and mitotic chromosomes of Simulium ornatipes and S. melatum were subjected to C banding procedures. In both species polytene chromosomes consistently show C banding of centromere regions, telomeres, nucleolar organiser and, unexpectedly, numerous interstitial sites. The interstitial C banding sites correspond to morphologically single polytene bands. Their response is graded and independent of band size. Interstitial C bands in S. ornatipes are scattered throughout the complement, whereas in S. melatum they are clustered. Supernumerary heterochromatic segments in S. ornatipes also exhibit strong C banding and inverted segments can differ from standard in C banding pattern. -- Mitotic chromosomes of both species show a single centric C band with indications of two weak interstitial bands in S. ornatipes, suggesting that many C band regions, detectable in polytene chromosomes, are not resolved by present techniques in mitotic chromosomes. -- Contrary to current opinion that C banding is diagnostic for constitutive heterochromatin, the interstitial C band sites of polytene chromosomes are regarded as euchromatic. Conversely, the heterochromatic pericentric regions of S. ornatipes are not C banded. -- It appears that polytene chromosomes offer a promising system for the elucidation of C banding mechanisms.

In Lucilia cuprina C-banding produces procentric bands on all autosomes and deep staining over most of the X and Y chromosomes which conciderably facilitates the analysis of complex Y chromosome rearrangements. The Y chromosome is generally darkly C-banded throughout while in the X chromosome a pale staining segment is found in the distal portion of the long arm. Modulation of the banding reaction results in 'grey' areas in both X and Y. When C-banding is compared with allocycly it is clear that not all heteropycnotic regions in the sex chromosomes C-band to the same extent. Secondary constrictions in the short arms of both X and Y chromosomes are clearly revealed by C-banding, the X satellite being polymorphic for size.--Q-banding results in a brightly fluorescing band in the short arm of structurally normal Y chromosomes. This band loses its fluorescence in some translocations, probably through a position effect. Hoechst 33258 staining does not produce any brightly fluorescing bands.