The ctenostomatous ectoproct Triticella koreni (G.O. Sars) occurs mainly on Calocaris macandreae (Bell) and Nephrops norvegicus (L.) but also on other Crustacea including Upogebia deltaura (Leach), Goneplax rhomboides (L.), etc. (Eggleston, 1969). Off Northumberland T. koreni occurs mainly on C. macandreae. C. macandreae moults from September to December (Buchanan, 1963).

In order to investigate how the ectoproct copes with this annual substrate loss collections of C. macandreae made in all months were examined. Some of the material was provided by Dr J. B. Buchanan; all came from mud bottoms 40 fathoms deep east of Blyth and was collected between 1961 and 1963. Ten random C. macandreae were taken from each month's collection. One periopod on each Calocaris was selected by the use of random numbers. The number of T. koreni zooids, the number of developing zooids, the number of oviparous zooids and the number of free eggs in each oviparous zooid on each selected limb were counted.

The data recorded from the ten limbs from each collection examined are shown in Table 1.

T. koreni zooids are hermaphrodite. The gonads and free spermatozoa and eggs can be seen through the translucent body wall. Spermatozoa and eggs rarely occur in quantity in the same zooid. Some zooids are so packed with sperm as to appear opaque; up to thirty-one eggs were seen in other zooids. The egg is small and unpigmented; the larva is unknown.

From November to June T. koreni colonies grow rapidly and have a high proportion of developing zooids. From July to October growth slows and reproductive activity increases.