Infection of the spined loach, Cobitis taenia (L.), by the digenean, Allocreadium transversale (Rud.)

The digenean Allocreadium transversale (Rud.) has been recorded once previously in Great Britain. During work on the feeding of Cobitis taenia (L.) it was found to be a frequently occurring gut parasite. Great variation occurred in its seasonal level of incidence and mean worm burden, indicating a rapid turnover and replacement of the parasite in the fish. No significant relationship could be shown between the level of infection and age of the fish; but a highly significant relationship occurred between incidence of infection and fish age.     

The mechanism of motilin excitation of the canine small intestine

Close intraarterial injections of motilin to the small intestine of the anaesthetized dog produce prolonged phasic contractions. Tetrodotoxin infused intraarterially blocked field stimulated contractions and abolished the response to motilin as did treatment with a combination of hexamethonium and atropine. Atropine alone increased the dose of motilin required to induce responses. Hexamethonium alone similarly increased the dose of motilin required in the jejunum, but not for the ileum. These results suggest that motilin acts to contract small intestine by stimulation of intrinsic excitatory nerves, some of which are post-ganglionic cholinergic and some of which are not, but are activated by a pathway with a nicotinic synapse. The ED₅₀ for ileal contractions was greater than that for the jejunum and the time to reach maximum contractions longer suggesting a decreased responsiveness of the lower small intestine to motilin as compared to the upper gastro-intestinal tract. These results and the lesser quantity of immunoreactive motilin in the ileum than in the jejunum may explain the lack of relationship of the activity front of the migrating motor complex in the lower small intestine to venous motilin concentrations.     

Some factors influencing the microdistribution of a population of spined loach,Cobitis taenia (L.)

Monthly observations (October 1972–October 1974) of a natural population of spined loach, Cobitis taenia (L.), in the River Great Ouse at Newport Pagnell indicated a patchy microdistribution, which varied seasonally. The distribution was clearly linked to the areas of fine substrate, which altered seasonally in position.Flow rates measured at monthly intervals in areas where Cobitis taenia (L.) were present were found to be approximately half those of areas in which Cobitis taenia L. were not found (0.148 m/sec and 0.293 m/sec). Substrate samples from areas where Cobitis taenia L. were present had a fine organic component, in contrast to the remainder of the river bed, which consisted of hard-packed gravel.In the laboratory, choice chamber experiments demonstrated a positive selection for fine organic deposits.