# Macroscopic Markers of Dolphin Healing at Sea Linked to Immunity

## TL;DR

Dolphins heal severe wounds without infection in the sea, and this study identifies visible markers linked to immune processes that could inform human and veterinary medicine.

## Contribution

This is the first study to link visible healing markers in dolphins to underlying immune processes.

## Key findings

- Dolphins form preliminary wound seals within 4–8 weeks and heal to atrophic scars that remodel for years.
- Macroscopic pigment patterns in live dolphins match those in stranded dolphins, linking markers to immune phases.
- These markers could serve as conservation tools and lead to novel regenerative therapies.

## Abstract

Accurate knowledge of healing benefits everyone. A pressing human need is learning how to heal without infection. Animal medical models of healing often lead to novel therapies, so new animal models are always sought. This study presents a new medical model: dolphins wounded at sea heal without medical intervention and commonly without infection despite constant exposure to microbial-rich seas. This daunting medical mystery has been illuminated in a set of 106 detailed longitudinal healing histories and scar searches, which illustrate several macroscopic markers of healing visible to boat-based observers. Further, strong matches with macroscopic markers of the most histologically detailed study of free-ranging dolphin healing to date establish links between markers and underlying immune phases of inflammation, proliferation, and remodeling. These results are pertinent to people interested in the healing process, cosmetic outcomes of scarring, and dolphin stranding, natural history, and conservation studies.

Wound healing has been studied extensively in humans and lab animals, but not in dolphins. Severe human wounds require extensive medical intervention to avoid infection. Yet severe wounds on free-ranging dolphins heal without infection in microbial-infested seas, a compelling distinction. An eye-witnessed shark attack on a yearling bottlenose dolphin yielded 8 years of macroscopic markers on a live recuperating dolphin by known days of healing. In total, 106 healing histories were generated from the author’s 20-year ethological study of free-ranging bottlenose dolphins (Tursiops truncatus) in St. Petersburg, FL, USA. Results show that unaided wound healing at sea involves two consecutive macroscopic pigment patterns, wounds form preliminary seals by 4–8 weeks, and most heal to atrophic scars that remodel for years. Macroscopic markers in live recuperating dolphins show strong matches with macroscopic wound patterns in stranded Fraser’s dolphins (Lagenodelphis hosei), demonstrating links between macroscopic markers and immune activities. This is the first study to link macroscopic markers visible as healing-related pigment patterns to immunity. Macroscopic markers are conservation tools for tracking anthropogenic impacts on increased susceptibility to infection at sea and could lead to novel therapies in veterinary and human regenerative medicine.