Leaf litter as a possible food source for chironomids (Diptera) in Brazilian and Portuguese headwater streams

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Abstract
Our objective was to evaluate the potential use of leaf detritus by chironomid larvae. Field and laboratory experiments were performed using leaves and chironomid species collected in Portugal and Brazil. Laboratory experiments under controlled conditions were done using microbial conditioned senescent leaves of Alnus glutinosa (L.) Gaertn, Neriumoleander L., Protium heptaphilum (Aubl.) March, Protium brasiliense (Spreng) Engl., Myrcia guyanensis(Aubl.) DC and Miconia chartacea Triana. Laboratory experiments were performed using specimens collected from leaf litter in local streams. Whenever possible, after the experiments, chironomids were allowed to emerge as adults and identified. In Portugal the following taxa were identified: Micropsectra apposita (Walker, 1856), Polypedilum albicorne (Meigen, 1838),Eukiefferiella claripennis Lundbeck (1898), Rheocricotopus (Psilocricotopus) atripes Rempel (1937) and Ablabesmyia Johannsen (1905) (Diptera, Chironomidae). Consumption rates ranged from 0.15 ± 0.10 mg (AFDM) of leaf animal-1 day-1 (Micropsectra apposita feeding on Alnus glutinosa) up to 0.85 ± 0.33 mg (AFDM) of leaf animal-1 day-1 (Polypedilum albicorne feeding on Miconia chartacea). In Brazil, the following taxa were identified from leaves: Phaenopsectra sp., Chironomus spp. and Polypedilum sp. and maximum consumption rates reached 0.47 ± 0.28 (AFDM) of leaf mg.animal-1.day-1 (Chironomus Meigen (1803) feeding on Protium heptaphilum). Feeding experiments with laboratory cultured specimens, revealed that some chironomids were unable to feed on decomposing leaves (e.g., C. xanthus Rempel (1939) on P.brasiliensis and M.guyanensis). Our results suggest that some stream chironomids (not typical shredders) can use leaf litter of riparian vegetation as a complementary food source.