Food and Habits of Meganyctiphanes norvegica

Abstract

1. Vegetable detritus of land and coastal origin is of notable importance as a source of food, especially to those specimens measuring 21-29 mm., which is the most abundant size found in the Clyde Sea Area.2. Meganyctiphanes in the Clyde Sea Area for the most part lives and feeds between 10 and 20 fathoms above a muddy bottom, usually in waters about 60-80 fathoms deep.3. Meganyctiphanes feeds by selecting from the surrounding water the suspended micro-organisms and detritus, and would thus come under the category of a “suspension feeder.”4. The larger specimens measuring 29-31 mm. are found chiefly in Upper Loch Fyne. The largest specimens measuring 37 mm. are found exclusively in Upper Loch Fyne.5. Adult specimens tend to decrease in numbers from May till September. During these months they appear to live during the day immediately above or on the muddy bottom.6. The association of Meganyctijihanes norvegica, Thysanoessa raschii, Euchceta norvegica, and Calanus finmarchicus, in large numbers in Upper Loch Fyne would indicate that conditions there are specially favourable to all these species.7. In Upper Loch Fyne M. norvegica, T. raschii, E. norvegica, and C. finmarchicus, make partial vertical diurnal migrations, specimens being found a few fathoms from the bottom during both day and night.8. Under certain circumstances light appears to have a harmful effect on M. norvegica.