Meeting Abstract

15.4  Wednesday, Jan. 4  Ammonia excretion in the green shore crab Carcinus maenas WEIHRAUCH, D.*; FEHSENFELD, S.; MARINI, A.-M.; ZIEGLER, A.; EDWARDS, S.; MEYER, H.; SIEBERS, D.; TOWLE, D. W.; Univ. of Manitoba; Univ. of Manitoba; Universite Libre de Bruxelles; Univ. of Ulm; Appalachian State University; Univ. of Osnabrück; Alfred-Wegener-Institut f. Polar und Meersforschung; Mount Desert Island Biological Laboratory weihrauc@cc.umanitoba.ca

The passion for crabs and their capabilities for osmoregulation and ammonia excretion brought us, David Towle, me and a number of collaborators together to explore how toxic ammonia is excreted in the branchial epithelium of the green shore crab Carcinus maenas. Here we summarize our published and unpublished findings on ammonia excretion mechanisms in C. maenas. Studies were performed on animals acclimated to full strength seawater (32 ppt S.) and brackish water (10 ppt S.). Interestingly, in either environment active ammonia excretion rates were significantly lower in the osmoregulatory active, mitochondria-rich posterior gills. An Rh-like ammonia transporter cloned from C. maenas gills was highly expressed in the gill epithelium, here with corresponding expression levels with regard to their actual ammonia transport rates. In contrast, expression levels were found to be very low in other tissues such as the antennal gland, hypodermis, hepatopancreas and heart muscle. Long term exposure to high environmental ammonia (HEA, 1 mM NH4Cl) caused in anterior and posterior gills of crabs acclimated to both, sea- and brackish water a significant decrease of the ammonia excretion rates. Moreover, while in seawater animals Rh-protein mRNA expression levels did not alter after short (6 hrs) and long term (14 d) HEA exposure, expression levels in the gills of brackish water acclimated crabs doubled after 14 d HEA exposure.