Collembola

Lang, Birgit & Russell, David J., 2022, Excretion of nitrogenous waste by soil fauna and assessment of the contribution to soil nitrogen pools, Soil Organisms 94 (2), pp. 69-83 : 73-74

2.4 Collembola

The main excretory organs in Collembola are the labial nephridia located in the head ( Hopkin 1997). Urine excreted via the nephridia is transported along the ventral groove (linea ventralis) to the ventral tube, at whose apical end the exchange of fluids and salts takes place ( Hopkin 1997). Additionally, the renewal of the midgut epithelium during moulting provides a way to excrete waste or toxic products ( Fountain & Hopkin 2005). However, a cytochemical study of the concretions found in midgut cells did not provide clear evidence for the presence of uric acid or urates by Humbert (1978). Ammonia is assumed to be the main excretory product as urea was not detected in experiments ( Larsen et al. 2007). Quantitative measurements are available for seven species, with ammonia excretion ranging from 0.005 to 1.66 µg N mg-1 day-1 ( Tab. 4) with a mean nitrogen excretion across species of 0.2 µg N mg-1 day-1. Interestingly, ammonia excretion reported by Larsen et al. (2007) at 21°C for Folsomia fimetaria (Linnaeus, 1758) , Protaphorura armata (Tullberg, 1869) and Sinella curviseta Brook, 1882 is many times higher in comparison to results by Sjursen & Holmstrup (2004) for the respective species at 20°C. This discrepancy is assumed to be caused by a different metabolic activity due to the length of starvation prior and during the experiments (Larsen 2007).

Nitrogen excretion was not found to be affected by population density ( Sjursen & Holmstrup 2004). Investigations of the influence of temperature on nitrogen excretion showed mixed results depending on species. For F. fimetaria , Folsomia candida Willem, 1902 and S. curviseta , ammonia excretion seems to increase with increasing temperature across a range from 5°C to 20°C ( Sjursen & Holmstrup 2004). In contrast, ammonia excretion seems to slightly decrease with increasing temperature in Hypogastrura assimilis (Krausbauer, 1898) , whereas no influence of temperature is apparent in P. armata ( Sjursen & Holmstrup 2004) .