Anatomic site and interanimal variability in morphologic characteristics of bottlenose dolphin (Tursiops truncatus) skin likely to affect dermal absorption studies

Abstract

Objective: To investigate anatomic site and interanimal variability in dolphin skin for use in development of models for cutaneous absorption studies.

Sample population: Skin from 30 healthy free-ranging bottlenose dolphins (17 males and 13 females grouped by age) and 10 captive males between 13 and 19 years old.

Procedure: Biopsy specimens were collected from the 10 male dolphins at 3 anatomic sites and from the 30 dolphins at 1 site; specimens were evaluated by light microscopy. Stratum externum thickness, minimal depth to the vasculature, and maximal epidermal depth were measured at 4 locations on 4 sequential sections. Comparisons of replicate measurements for 3 skin characteristics were made within and among anatomic sites, between dolphins of the same sex and approximate age, and across males and females of various ages.

Results: The stratum externum in male dolphins was thicker. Differences attributable to age and anatomic site were not significant. Variation attributable to differences in stratum externum thickness between dolphins was significant. Differences among body sites within the same dolphin were significant but were not consistent from dolphin to dolphin. Mean stratum externum thickness was not different between males of the 2 cohorts, but mean maximal epidermal depth and mean minimal depth to the vasculature were different. Variances within the 2 male cohorts were not significantly different.

Conclusions: Studies affected by stratum externum thickness should eliminate the effect attributable to sex difference by using dolphins of the same sex or grouping analytical data by sex. Precision could be improved without increasing the total number of dolphins by collecting more than 1 sample/dolphin.