Changes in pH in the caecum of Loligo vulgaris reynaudii during digestion

Abstract

The time-scale of colour/pH changes in the caeca of 196 longfinned squid Loligo vulgaris reynauclii during digestion/absorption was tested at sea. Red, brown, dark yellow, pale yellow and white were the recorded colours. The range of mean pH for these colours was 6,019–5,638. The time-span of the whole process in the field, at a temperature of 7–10°C, is thought not to exceed 14 h. The red and brown stages lasted on average 4 h each and the mean pH for these colours was 6,019 and 5,823 respectively. The other stages were probably much shorter, the mean pH being 5,756 for the dark yellow phase, 5,699 for the pale yellow and 5,638 for the white. It is suggested that sex, stage of maturity, size of animal, food type and meal volume have a negligible impact on the colour and pH in the caeca of the squid investigated and, therefore, on the duration of the digestion/absorption process. However, before the colour/pH scale can be used for assessing the duration of the digestion/absorption process of wild squid under all circumstances, it requires further testing in aquaria as well as in the field. © 1990 Taylor and Francis Group, LLC.