Epithelial transport and osmoregulation in annelids

Abstract

Epithelial transport related to osmoregulation has so far not been extensively investigated in annelids. Compared with the large body of information about ion transport across crustacean or insect epithelia, only a few studies have been done with isolated preparations of annelids, using the body wall of marine polychaetes or Hirudinea. Nephridial function and general body homeostasis have received more attention, and have probably been best investigated in Hirudinea. With recent advances in the molecular physiology of epithelial transport systems in vertebrates, the cloning of various transporters and ion channels, and the considerable number of osmoregulatory peptides that have now been found and analyzed from annelids, it should now be possible, and is timely, to conduct functional studies on individual selected epithelial preparations or isolated cells from annelids. Such studies may be important for establishing useful models with somewhat less complexity than mammalian systems. For example, annelids lack aldosterone, an important osmoregulatory hormone, which is a key factor in the regulation of sodium reabsorption in vertebrates. Therefore, not only would such studies contribute to annelid physiology, but they would be important in a broader sense for understanding osmoregulation and its evolution. They should also facilitate the discovery and investigation of new specific regulatory pathways.

Morphometry of the epidermis of an invasive megascoelecid earthworm (Amynthas gracilis, Kinberg 1867) inhabiting actively volcanic soils in the Azores archipelago

“…Since the epidermis also plays functional roles in an ion transport, it is unsurprising that nonessential metal ions and xenobiotics enter the organism through it (Dietz, 1974;Clauss, 2001). It is noteworthy that there is an evidence that the dermal route is the predominant route for metal uptake by earthworms (Vijver et al, 2003).…”

Mechanism of ammonia excretion in the freshwater leechNephelopsis obscura: characterization of a primitive Rh protein and effects of high environmental ammonia

“…Unlike the more widely known blood-feeding leeches, this species is carnivorous, feeding on a protein-rich diet comprising mainly chironomids and small oligochaetes (16). Although little is known about the nitrogen physiology of N. obscura, a number of studies have investigated the sodium transport across the skin in other freshwater leeches (12). From studies on the bloodfeeding medicinal leech Hirudo medicinalis, the skin has been identified as a site of sodium uptake (60,61), which may also potentially serve as the site of ammonia excretion due to the similarity in transporters typically utilized for both processes (30,35,45).…”

“…From studies on the bloodfeeding medicinal leech Hirudo medicinalis, the skin has been identified as a site of sodium uptake (60,61), which may also potentially serve as the site of ammonia excretion due to the similarity in transporters typically utilized for both processes (30,35,45). In addition to skin, other potential sites of ammonia transport include the metanephridia, where urine formation and salt balance occur, as well as the intestine where nutrient uptake and food breakdown occur (12).…”

Morpho-Histopathological Response of Phorate-An Organo-Phosphorous Pesticide on the Integumentary Musculature of an Epigeic Earthworm, Eisenia fetida

“…Previous studies have suggested that earthworm's skin has direct contact to the contaminated soils and is considered as a significant route in the uptake of toxicants (Vijver et al, 2003). Epidermis and cuticle represent a primary barrier that protects earthworm's body from the environment and are also responsible for the transport of ions, thus allowing/blocking xenobiotics to enter the body (Clauss, 2001). The current investigations on the Eisenia fetida revealed that the contact toxicity of phorate through its integument was increased with increasing concentration and /or exposure time of the given toxicant.…”