The ecology of populations of dace, Leudscus leuciscus (L.), from two tributaries of the River Wye, Herefordshire, England

Samples of dace were taken from the Afon Llynfi and the River Lugg each month for 13 consecutive months. Male dace grew faster than females and rates were comparable with those described for several other populations. Variations in year-class strengths were observed and these differed between the populations although 1959 was strongly represented in both. The sex ratio varied throughout life and disturbances in the expected ratio were attributed to the attainment of sexual maturity at the end of the fourth year of life (3+). Observation of the seasonal gonad cycles indicated that spawning occurred in March or April. Fecundity was estimated at about forty eggs per gram of total weight. A seasonal cycle of feeding activity was established with highest food consumption during summer. There was evidence of a fast during the spawning period. No correlation between temperature and feeding activity could be established. Dace were omnivorous, but aquatic insects and algae were the main components of the diet. Seasonal variations generally followed availability. The importance of aerial insects declined with age. Many differences in feeding habits were detected between the populations.     

Microheterogeneity of cross-linked gamma dimers isolated from bovine stabilized fibrin

Bovine stabilized fibrin was reduced, carboxymethylated and separated by chromatography on a Sepharose 4B column. The fraction containing cross-linked γ dimers was then subjected to linear gradient chromatography on a CM-52 column. On this column, the γ dimers were separated into an adsorbed and unadsorbed fraction. The components in these fractions were designated as the γ-1 and γ-2 dimers. They each gave a single band on SDS-polyacrylamide gel electrophoresis and both had a molecular weight of 90,000 (±2,000). The identities of the γ-1 and γ-2 dimers were also shown by their amino acid compositions, terminal residues and tryptic and plasmic maps. However, they differed in electrophoretic mobilities on gels at pH 8.3 and pH 3.6 and in carbohydrate composition. The γ-1 dimer was slightly acidic and contained more hexoses and glucosamine than the γ-2 dimer. These results indicate that the characteristics of the bovine monomeric γ chains, γ-1 and γ-2, previously reported by Gerbeck $\text{et al}$., are transferred to their corresponding cross-linked γ dimers, formed in the stabilization of fibrin.