Discovery of the Larvae and Pupae of the Black Fly Simulium (Gomphostilbia) khelangense and Breeding Habitats of Potential Pest Species of the S. (G.) chumpornense Subgroup (Simuliidae).

THAILAND; SOUTHEAST Asia

Simple Summary: The concentration of larval black flies in well-defined aquatic habitats makes knowledge of the breeding sites critical for the efficient management of pest species. Black flies can achieve pest status either as generalists by developing in many types of streams and rivers or as specialists by developing in one or a few types of flowing water, such as large rivers. These two developmental strategies are evident in pest and vector species of the Simulium (Gomphostilbia) varicorne species group in Thailand. Simulium chumpornense is a habitat generalist, whereas S. khelangense is a habitat specialist, developing in the large Mekong River, where we discovered its immature stages. The first descriptions of the larva and pupa of S. khelangense, along with mitochondrial and nuclear genetic markers, allow accurate identification and comparisons with structurally similar species in the S. varicorne species group, thus aiding the ability to monitor the pest and vector status of black flies in Southeast Asia. Two species of black flies (Simuliidae) in Thailand, Simulium chumpornense Takaoka and Kuvangkadilok, 2000, and S. khelangense Takaoka, Srisuka & Saeung, 2022, are potent vectors of avian blood protozoa of the genera Leucocytozoon and Trypanosoma and are pests of domestic avian species. Although the adults are abundant throughout Thailand, information on their breeding habitats is limited, and the immature stages of S. khelangense are unknown. We collected the larvae and pupae of S. khelangense from the Mekong River, the first-ever record of Simuliidae from this large continental river. Mitochondrial cytochrome c oxidase I and internal transcribed spacer 2 were used to associate the larvae and pupae with known adults. Both genetic markers strongly supported their identity as S. khelangense. The larvae and pupa of S. khelangense are described. The pupal gill filaments, larval abdominal protuberances, and setae distinguish this species from other members of the S. varicorne species group. The immature stages of S. chumpornense inhabit a wide variety of flowing waters, from small streams (3 m wide) to enormous continental rivers (400 m wide); thus, S. chumpornense is a habitat generalist. In contrast, S. khelangense was found only in the large Mekong River and is, therefore, a habitat specialist. Both species can exploit their principal habitats and produce abundant adult populations. [ABSTRACT FROM AUTHOR]

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