The Production and Respiration of an Enchytraeid Population in Blanket Bog

• Published in: The Journal of animal ecology 1973-06, Vol.42 (2), p.219-245
• Main Author: Standen, Valerie
• Format: Article
• Language: English
• Subjects: Acclimatization; Body weight; Bogs; Death; Mortality; Oxygen consumption; Population estimates; Production estimates; Respiration; Worms
• ISSN: 0021-8790; 1365-2656
• DOI: 10.2307/3282

(1) Cognettia sphagnetorum comprises approximately 90% of the biomass of Enchytraeidae extracted from Moor House blanket bog. (2) C. sphagnetorum reproduces by fragmentation. Laboratory experiments established that two or three fragments are produced at a rate modified by temperature according to the time the whole worms were removed from the field. (3) The fragments regenerate their missing parts. The rate of growth by addition of new segments is highly variable but not related to the size. (4) A compartmental model predicts the sizes of various categories of the population and compares the predictions with the observed sizes. (5) The mortality estimates show that the greatest biomass of C. sphagnetorum is returned to the soil in autumn or winter. (6) The annual net production of C. sphagnetorum was$12\cdot 44\ {\rm g}/{\rm m}^{2}$in 1968-69 and$10\cdot 05\ {\rm g}/{\rm m}^{2}$in 1969-70. P/B̄ is 1·19 and 0·77 in the successive years which may be low compared with other small invertebrates. (7) Estimates of the annual net production of the five species of sexually reproducing enchytraeids found on the same sites are also given. (8) There was no evidence that the worms are acclimatized to low temperatures. The worms become passive in response to low temperatures. (9) Total population respiration was$61\cdot 98\ {\rm kcal}/{\rm m}^{2}$in 1968-69 and$63\cdot 36\ {\rm kcal}/{\rm m}^{2}$for 1969-70; 60-65% of this energy was utilized by the large whole worms. (10) Material utilized directly by the population for tissue production and respiration in a year amounts to only 2% of the annual input of litter into the system. (11) Litter consumed though not assimilated by the population may be as much as 40%. (12) By comparison with other invertebrates C. sphagnetorum populations appear to have a low rate of production. (13) It is suggested that reproduction by fragmentation conserves minerals and energy and that therefore this species is well adapted to live under Moor House conditions.