Longevity in a Polychaete and a Coelenterate

IN December 1949 I collected a small group of the serpulid Mercierella enigmatica Fauvel, which lives in brackish-water as well as in the sea, growing on reeds in Lake Mariout, Alexandria, Egypt. I brought the dozen or so of the tube-worms back to London and kept them alive for a number of years in a small aquarium containing sea-water diluted half-and-half with distilled water. Together with the tube-worms were a filamentous green alga, Rhizoclonium sp., a brown alga, Ectocarpus sp., and a small rissoid gasteropod mollusc which went through many generations. Nothing was added to the aquarium except distilled water occasionally. The Mercierella must have fed on flagellate protozoa and perhaps sometimes on algal zoospores. The last individual worm died in May 1962, that is, 12 years and 5 months after capture. During captivity the most noticeable change was that the colour of the crowns altered from the original light greenish-brown to a dark brown. The age of the animals at the time of the capture was, of course, unknown, but their length of life in captivity seems to be the greatest known for an annelid.