The ultrastructure of the lachrymal 'salt' gland and the Harderain gland in the euryhaline Malaclemys and some closely related stenohaline emydines

Abstract

The ultrastructure of the Harderian gland from the euryhaline species Malaclemys terrapin is nearly identical with that of the Harderian gland from several freshwater and stenohaline emydines. The abundant rough-surfaced endoplasmic reticulum, and the prominence of the secretory droplets throughout most of the cytoplasm, indicate that this gland is primarily involved in the secretion of organic materials, and has no role related to the salinity of the environment in which the animals are kept. However, the ultrastructure of the lachrymal gland in Malaclemys differs markedly from that of the remaining emydines studied. In the freshwater emydines the lachrymal gland appears to be involved in the secretion of organic material; the tubules contain both mucous and serous cells. In the lachrymal gland from Malaclemys secretory droplets, Golgi apparatus, and endoplasmic reticulum were insignificant features, while mitochondria, glycogen, and microvilli on the serosal surfaces of the cells were very prominent. These and other features cause a strong resemblance between the lachrymal gland in Malaclemys and other tissues noted for active transport. The above morphological evidence suggests that if either of the orbital glands is involved in osmoregulation the most probable choice is the lachrymal gland.