Seasonal vertical migration and aestivation of Rhyacodrilus hiemalis (Tubificidae, Clitellata) in the sediment of Lake Biwa, Japan

• Published in: Hydrobiologia Vol. 564; no. 1; pp. 87 - 93
• Main Author: NARITA, Tetsuya
• Format: Conference Proceeding Journal Article
• Language: English
• Published: Dordrecht Springer 01.07.2006; Springer Nature B.V
• Subjects: Aestivation; Anaerobic respiration; Animal and plant ecology; Animal, plant and microbial ecology; Biological and medical sciences; Climatic conditions; Clitellata; Collections; Cores; Deep layer; Diurnal variations; Dominant species; Freshwater; Fundamental and applied biological sciences. Psychology; General aspects; Grain size; Inland waters; Interspecific relationships; Lake sediments; Lakes; Life history; Littoral environments; Moisture content; Oligochaeta; Phosphorus; Predation; Rhyacodrilus; Rhyacodrilus hiemalis; Seasons; Sediment; Sediment temperature; Sediments; Size distribution; Summer; Synecology; Tubes; Tubificidae; Vertical distribution; Vertical migration; Vertical migrations; Water content; Asia; Japan; Lake Biwa; Japan, Honshu, Shiga Prefect., Biwa L; Tubificidae; Rhyacodrilus hiemalis; Vertical distribution; seasonal vertical migration; Estivation; Lake sediments; Annelida; Oligochaeta; Freshwater environment; Aquatic environment; Hydrobiology; Seasonal variation; Lake Biwa; Invertebrata; aestivation; Vertical migration
• ISSN: 0018-8158; 1573-5117
• DOI: 10.1007/s10750-005-1710-3

The vertical distribution of the tubificid worm Rhyacodrilus hiemalis Ohtaka, the numerically dominant species of oligochaete in the littoral of Lake Biwa, was studied with special reference to seasonal vertical migration in the lake sediment. Monthly collections of lake sediment cores were made using PVC tubes. Core sections of sample sediments ranged from 76 to 117 cm. The vertical distribution of the worms showed no diurnal variation; therefore diel vertical migration was not evident. Seasonal downward migration started in April, and upward migration started in October. From December to March, almost all worms remained in the near-surface sediment layer (surface to 30 cm deep), while from July to September almost all worms remained deeper than 30 cm. However, few individuals migrated deeper than 90 cm. No discontinuous layers were found in grain size composition, water content, loss on ignition, particulate carbon, nitrogen or phosphorus. In deep sediment there was no free oxygen, as evidenced by negative ORP values. For 4 months in summer, R. hiemalis aestivated, probably utilizing anaerobic respiration. It appeared that R. hiemalis moved deeper in the sediment in response to sediment temperature, because sediment temperatures in the deep layers seemed to converge at around 20–21 °C in the summer months. The life history traits of seasonal vertical migration and summer aestivation perhaps arose as an adaptation to the climatic conditions accompanying the geographical origin of R. hiemalis, and they also serve to minimize predation risk during summer when most invertebrate predatory fishes are active.