Meeting Abstract
Juvenile and adult paddlefish have striking, darkly-pigmented gill respiratory lamellae. To investigate this unusual condition, a visual assessment protocol was developed to quantify the degree of pigmentation of gill filaments. Four groups of larval and early-juvenile stage (30, 50, 60 and 100 day post-hatch) fish were analyzed. For each fish, multiple gill arches from both the right and left sides were studied. Each filament in a gill arch was scored, based on the extent to which pigment was observed along the length of the filament. This approach thus assessed the degree of gill pigmentation in post-hatch, early paddlefish development. Results clearly indicate a dramatic change in gill pigmentation over the period examined. There was no gill pigmentation in 30 day post-hatch fish, low but increasing levels in 50 and 60 day fish, and markedly higher pigment in gills of 100 day post-hatch fish. Pigment changes appeared to be independent of numbers of filaments per gill arch, which stabilized at 50 days post-hatch. Histology indicates that primary lamellae melanocytes are responsible for paddlefish gill pigmentation. These cells are generally perivenous – localized adjacent to and along the central vascular elements of the filament. Results are considered in light of possible functions associated with gill pigmentation as well as developmental origin and activation of gill melanocytes.
