In situ studies on the diurnal activity pattern of diastylis rathkei cumacea crustacea and its importance for the hyper benthos
Anger, K.; Valentin, C.
Helgolaender Wissenschaftliche Meeresuntersuchungen 28(2): 138-144
D. rathkei Kroeyer exhibits negative phototaxis during the day. It never leaves the sediment as long as there is any light. The vertical migrations into the pelagic environment, as observed in Aug. and Oct., start about 1 h after sunset with maximum intensity from about 22.00-23.00 h and ending at midnight. D. rathkei reacts positively to light during this time. Fishes and other predatory animals are almost inactive during this period. Population loss by predation is thus negligible or even lacking. The literature on the hyperbenthos is critically discussed in relation to the method mostly employed, the use of Beyer's epibenthic closing net. This gear is not considered to be useful and the results obtained by it are questioned. D. rathkei has no significance for the hyperbenthos. The existence of this community in the W Baltic Sea is doubted.