Spiny dogfish can cover small skin wounds with a new cell layer very early. In a laboratory study, all wound beds examined on the first day already had a continuous new epithelial layer. Rebuilding the deeper skin and its characteristic dermal denticles took considerably longer.
Published on 9 September 2026 in Scientific Reports, the wound-healing study distinguishes two stages: early surface coverage and slower restoration of tissue structure. The findings do not mean that wounds were completely healed within 24 hours.
20 female spiny dogfish under controlled conditions
The team studied 20 female spiny dogfish of the species Squalus acanthias. The animals came from commercial hook-and-line catches near Chatham, Massachusetts, and were kept at the Marine Biological Laboratory in Woods Hole. The flow-through seawater was approximately 14 degrees Celsius.
After acclimation, six standardized skin biopsies, each four millimetres in diameter, were taken from each animal. This produced 120 full-thickness skin wounds. The researchers documented their development photographically for 35 days and collected wound tissue on days 1, 14 and 35. The sharks were euthanized at the end of the approved animal experiment.
A new cell layer after one day
Microscopic examination showed a continuous cell layer across the wound bed at the first sampling time. Exactly when this coverage developed during the first day remains unknown, because no additional tissue samples were examined between injury and day 1.
These early changes did not yet appear as complete healing in ordinary photographs. The visible wound area continued to decrease over the following weeks. By day 14, the new epidermis had thickened, while the basement membrane and collagen-containing repair tissue underneath had begun to reorganize.
Dermal denticles were still absent after 35 days
On day 35, the researchers observed a thickened epidermis and collagen-rich, scar-like tissue. The original architecture of the deeper skin had not been fully restored. The repaired surface still lacked the dermal denticles that give shark skin its characteristic structure.
Early cell coverage is therefore an important repair step, but not evidence of fully restored skin. The 35-day study does not establish how long denticles take to return in these spiny dogfish.
Signs of an early immune response
The team also examined RNA from individual nuclei in skin samples. The data enabled different cell groups to be identified, including epidermal, connective-tissue and immune cells. In the pooled samples, the relative proportions of several immune-cell groups increased on the first day and generally declined again by day 14.
These molecular results are explicitly descriptive: samples from four animals were pooled at each time point. There were therefore no independent animal-level replicates for statistically robust comparisons between time points. The day-35 RNA sample failed quality control and was excluded.
What the experiment can tell us
The study documents rapid early reepithelialization in female spiny dogfish under these laboratory conditions. Tissue assessment was qualitative and unblinded, without comparative statistical tests. The small standardized injuries also do not allow direct conclusions about large bite wounds in the wild.
For shark biology, the work provides a time-resolved view of skin repair in one species. It demonstrates neither a uniform healing rate across all sharks nor a treatment ready for human use. Particularly informative is the considerable time gap between early wound coverage and complete tissue reconstruction.
