OCCURRENCE OF AN UNUSUAL POLYMERASE CHAIN-REACTION PRODUCT DURING IDENTIFICATION OF ANOPHELES-GAMBIAE SIBLING SPECIES (DIPTERA, CULICIDAE)

Using the polymerase chain reaction (PCR) for species differentiation within the Anopheles gambiae complex, we examined several hundred Came roonian mosquito specimens. Applying an approved routine protocol for DNA extraction and PCR conditions, apart from the indubitable identifi cation of most of the specimens, we came across ten PCR products that did not correspond in length to any of the hitherto known amplificatio n products of the sibling species. Sequencing experiments showed the t en products to be of identical length (117-bp) and nucleotide sequence . The total sequence of the novel product is included in the PCR produ ct specific for A. melas, which is known to occur in the same collecti on area as the ten unidentifiable mosquito specimens. On alignment of the novel PCR product sequence and the A. melas one starting at the 3' -end primer annealing site, the last 20 nucleotides of the novel produ ct, reflecting the sequence of the 2(nd) PCR primer, showed only 60% h omology with the then-corresponding A. melas DNA site. Explanations fo r the occurrence of the unusual PCR products are given and discussed.