An improved diet for inland broodstock and the establishment of an inbred line from Botryllus schlosseri, a colonial sea squirt (Ascidiacea)

Abstract

Improved inland culturing methods for marine invertebrates are the most important prerequisite for the establishment of inbred lines. Here, we study the effects of improved diet on growth rates, survivorship and reproductive activities of the colonial urochordate Botryllus schlosseri, an important model species in a variety of scientific disciplines. Six long-term experiments (6−8 weeks each; 3−8 treatments per experiment) were conducted in an attempt to evaluate 10 different food types alone and in various combinations. We took a hierarchical approach in which some food types were contrasted and the results were used to design the next experimental set with new food types. A mixture of at least two types of diets was superior to any monotonous diet examined. Results were also characterized by high variability between colonies of the same hatch in any studied life history aspect, by the appearance of reproductive sterile colonies in the cultures, high survivorship, fast growing and long-lived colonies. The improved maintenance protocols enabled us to develop the first long-lived (> 6.5 years) inbred line of Botryllus with four successive generations of self-crossed pedigree animals.