Untersuchungen zum Fluoridhaushalt der Euphausiaceen am Beispiel von Meganyctiphanes norvegica (M. Sars) und Euphausia superba Dana

• Main Author: Keck, Alexander
• Format: Thesis
• Language: German
• Published: 1984
• Subjects: Euphausia superba; Meganyctiphanes norvegica
• Online Access: https://oceanrep.geomar.de/id/eprint/42258/; https://oceanrep.geomar.de/id/eprint/42258/1/Diss.%201984%20Keck,%20A.pdf

On the fluoride budget of euphausiids. Investigations on Meganyctiphanes norvegica (M. Sars) and Euphausia superba Dana various aspects of the fluoride occurrence in euphausiids were chiefly examined in maintenance experiments: Fluoride uptake, release, toxicity, accumulation, dynamics during the mault cycle and function. Krill takes up dissolved fluoride quantitatively from seawater. A potential uptake via food can be neglected as a model calculation shows. The fluoride uptake was quantified for norvegica by F- analysis of experimental water. Fluoride was released rapidly from dissected cuticle and exuviae, respectively (70% and 50% of the initial value in the course of 4 hours, resp.). In dead individuals, however, the F- release was strongly delayed (40% in the course of 4 hours). The loss of the organic portion in any case proceeded more slowly and therefore reveals no direct connection with the F- liberation. The possible chemical binding in the cuticle is discussed. A raised amount of fluoride in the experimental tanks from 5 mg/1 up caused significant mortality. Dependent on the exposure time an additional fluoride accumulation took place which more than doubled the normal F- values of the carapace. More than 99% of the total fluoride in an individual is bound in the cuticle, as a balance estimation shows. The p- content of the cuticle only changes for a short period directly before (F- decrease) and after exuviation, during the synthesis of the new shell F- increase), and otherwise remains constant. Maintenance for several weeks in fluoride-free artificial seawater did not affect survival rates of experimental animals as compared to controls. Accordingly, fluoride appears not to have a vital function for krill. It is hypothesized that the significance of fluoride for euphausiids is its functional property as a structural element of a common type of skeletal construction in marine invertebrates to which high contents of phosphate and protein are characteristic.