A new anhydrobiotic midge from Malawi, Polypedilum pembai sp.n. (Diptera: Chironomidae), closely related to the desiccation tolerant midge, Polypedilum vanderplanki Hinton

Abstract

The sleeping chironomid (Polypedilum vanderplanki Hinton) lives on temporary rock pools in the semi‐arid tropical regions of Africa. Its larvae are able to survive the dry season in a completely desiccated ametabolic state known as anhydrobiosis. So far, P. vanderplanki was the only species among all insects showing demonstrated anhydrobiotic ability. Here, we show that a new related species originating from Malawi, Polypedilum pembai sp.n., is also anhydrobiotic and that its desiccation tolerance mechanism is probably similar to what is observed in P. vanderplanki. The new species, P. pembai sp.n., is described with special attention to the common and different morphological features, compared with P. vanderplanki. Phylogenetic analysis showed that both species are closely related, suggesting that anhydrobiosis evolved only once in their common ancestor about 49 Ma somewhere in Africa, before the divergence of two species, one in the sub‐Saharan area and another in southeastern Africa.

DNA barcodes successfully delimit morphospecies in a superdiverse insect genus

“…Immatures of Polypedilum can occur in both standing and flowing waters, even in those at high latitude and altitude (Zhang, Song, Qi, & Wang, ). Moreover, three Polypedilum species, including the famous sleeping midge Polypedilum vanderplanki Hinton, are known for their capability to undergo anhydrobiosis and tolerance to complete dehydration (Cornette et al., ; Cranston, ; Hinton, ). Polypedilum may also be among the most abundant invertebrates in eutrophic ponds, reaching densities of up to 1,200 larvae per square metre (Int Panis, Bervoets, & Verheyen, ).…”

Population genomics of two closely related anhydrobiotic midges reveals differences in adaptation to extreme desiccation

“…Consistently with this assumption, we observe a similar genetic architecture of anhydrobiosis-associated genes, in particular, the presence of a multigene family of PIMTs (see below). Still, due to the difference in the ecotopes of P. pembai and P. vanderplanki, the frequency of desiccation-rehydration cycles is expected to be higher for P. pembai (Cornette et al 2017), suggesting the possibility of a species-specific adaptation. Indeed, the genetic distance between P. vanderplanki and P. pembai was higher for chromosome 4 (10%) than for the other three chromosomes (7%) (table S8).…”

“…While other lineages (tardigrades, rotifers, nematodes) have many anhydrobiotic organisms in their phyla, P. vanderplanki was untill recently the only proven anhydrobiotic species both among the Chironomidae family and the whole phylum Arthropoda (Watanabe 2006). However, another midge from Malawi that was initially referred to as P. vanderplanki (McLachlan 1983) is also able to survive in the desiccated state in the larval stage but differs in ecology from the Nigerian anhydrobiotic midge (Cornette et al 2017). While in Nigeria the dry season can last up to eight months without rain, in Malawi, it is interspersed with periodic sporadic rainfall (Cornette et al 2017).…”

“…However, another midge from Malawi that was initially referred to as P. vanderplanki (McLachlan 1983) is also able to survive in the desiccated state in the larval stage but differs in ecology from the Nigerian anhydrobiotic midge (Cornette et al 2017). While in Nigeria the dry season can last up to eight months without rain, in Malawi, it is interspersed with periodic sporadic rainfall (Cornette et al 2017). Therefore, the larvae of the Malawian midge face several desiccation-rehydration cycles within one season (Cornette et al 2017).…”

“…While in Nigeria the dry season can last up to eight months without rain, in Malawi, it is interspersed with periodic sporadic rainfall (Cornette et al 2017). Therefore, the larvae of the Malawian midge face several desiccation-rehydration cycles within one season (Cornette et al 2017). Together with morphological differences between the two chironomids, this allowed to describe the Malawian midge as a new anhydrobiotic species Polypedilum pembai (Cornette et al 2017) (fig.…”