Life history of Lepidostoma hirtum in an iberian stream and its role in organic matter processing

The goal of this research was to determine the role of Lepidostoma hirtum Fabricius 1775 in the fragmentation of allochtonous organic material, in a segment of a mountain river in central Portugal. For this purpose, we measured leaf fragmentation and growth rates at four temperatures (9, 12, 15 and 18 degrees C) and four leaf types (alder, Alnus glutinosa L.; oak, Quercus andegavensis Hy; poplar, Populus x canadensis Moench; and chestnut, Castanea sativa Mill.). Growth rates ranged from 0.012 to 0.049 mg AFDW day(-1) with no significant effect of temperature and leaf type. Fragmentation/consumption rates were significantly higher for alder (1.62 mg animal(-1) day(-1)) than for other leaf types, and significantly lower at 9 degrees C (0.70 mg animal(-1) day(-1)) than at any other temperature (1.12 mg animal(-1) day(-1)). In the studied stream, L. hirtum larvae had a univoltine life history, with an asynchronous development. Secondary production of L. hirtum ranged from 53.95 mg m(-2) year(-1) (pools) to 63.12 mg m(-2) year(-1) (riffles). Annual P/B ratios differ between habitats: they were 4.01 year(-1) for pools and 4.49 year(-1) for riffles. Considering the average density of this species in the study river and their consumption rates, this species has the potential to fragment 8.6 times the mean annual standing stock of organic matter, in the study location.