Skin filament recovery after clipping in Hippocampus guttulatus: behavioural and histological aspects

Skin filaments are present on the heads of several Hippocampus species. Their clipping is a useful, non-lethal technique for marking individuals and sampling tissue. Little is known about the consequences of clipping on behaviour and details of regeneration. We present the results of a study on the effects of filament clipping on activity patterns and the regeneration of this structure at the macroscopic and microscopic level in Hippocampus guttulatus Cuvier, 1801 from the Gulf of Taranto (Apulia, Ionian Sea). Twelve individuals of both sexes underwent filament clipping, and their behaviour sequences (expressed as percent of total time spent swimming, resting, food searching, and swinging) were monitored for 10 wk in water tanks. In the first week, individuals spent significantly more time food searching and swimming compared to controls, whereas in the following weeks, no differences between groups were observed. Regeneration was observed in 12 other individuals reclipped after 3, 5, and 7 wk. Sections of paraffin-embedded filaments were stained with Mallory’s trichrome, alcian blue pH 2.5, periodic acid-Schiff (PAS), and PAS with diastase. Epidermal cells and basal membranes were the first to recover fully. Basal epidermal cells were filled with glycogen. In the dermis, the arrangement of bundles of fibres surrounded by melanocytes took longer to reconstitute. After 10 wk, the filaments grew to about 36.7% of their original length, whereas at the microscopic level, the tissues recovered fully. It is concluded that filament clipping does not significantly affect the general behavioural patterns of H. guttulatus, and regeneration at the microscopic level is fully accomplished.