Serum composition of the coelacanth, <i>Latimeria chalumnae</i> Smith

Abstract

Abstract Inorganic and organic constituents were studied on blood serum collected from a living specimen of the coelacanth, Latimeria chalumnae . Inorganic electrolytes determined included sodium (196.7 mM/l), potassium (5.78 mM/l), magnesium (5.30 mM/l), calcium (4.94 mM/l), chloride (186.7 mM/l), bicarbonate (9.60 mM/l), phosphate (5.08 mM/l), and sulfate (4.80 mM/l). Serum urea (377 mM/l) and trimethylamine oxide (122 mM/l) were high as previously reported, and accounted for the bulk of the total non‐protein nitrogen (1199 mg%); total amino acids added a small but not insignificant fraction (21.9 mg%). High serum lactate (16.5 mM/l) and glucose (6.57 mM/l) levels were probably indicative of stress; glucose was the only carbohydrate present in appreciable amounts in the serum, although traces of glucuronic acid and rhamnose were found. Serum total cholesterol was 3.91 mM/l, organically bound phosphorus 1.99 mM/l and total proteins 2.84 g%. Three major protein fractions were evident from cellulose acetate electrophoresis and at least 11 peaks were demonstrable by acrylamide gel electrophoresis. Latimeria serum lacks a protein component with a mobility approaching that of human serum albumin. Serum osmolarity (932 mOsm/l) was somewhat lower than that of sea water collected at the site of capture of the specimen (1035 mOsm/l). Evolutionary implications of the similarity of Latimeria serum chemistry to that of other marine fishes are discussed.