Notes from Flatford Mill

NOTES FROM FLATFORD

MILL

Priapulus caudatus Lamark.

P. caudatus was found for the first time in the Fiatford area on March Ist, 1958 ; a single specimen was taken from soft mud just below mean sea level on the shore of the Stour estuary at Stutton Ness. Subsequently it has proved to be widespread on both Suffolk and Essex shores of the estuary and occurs intertidally in small numbers wherever there is a suitable substrate of soft mud. No individuals have been taken however from the region of lowered salinities above Brantham. In addition to the animals from the Stour, P. caudatus has been found in the mud of the large lagoon at Shingle Street in Suffolk and from a similar habitat by the Wade at Hamford Water, Essex. T h e Victoria History of Suffolk (1911) notes that this animal is common in the mud of the Deben at Waldringfield. It seems very likely that the species occurs and should be looked for in all Suffolk estuaries under suitable conditions.

Priapulus is an unusual unsegmented worm. The genus appears to have only slight affinities with other groups of invertebrates and is usually placed in a phylum of its own—Phylum Priapulida.

Paragnathia formica Hesse.

A pike (Esox lucius) in poor condition was caught on May 27th, 1958, in the tidal pool below the main sluice at Fiatford Mill.

T h e fish was infected with two species of crustacean parasites.

One of these, Argulus foliaceus (Crustacea, Branchiura), the fish louse, occurs frequently on pike and on other freshwater fish in the River Stour system. The other parasite, the Praniza larva of Paragnathia formica (Crustacea Isopoda) which is typically an estuarine species, has not been observed at Fiatford before.

Ten of these larvae were found in the mouth of the host, chiefly in folds of skin lying alongside the rows of teeth. Estuarine fish are the normal hosts of P. formica and a freshwater host would appear to be unusual.

P. formica is a fish parasite only during the larval part of its life history; the adults are free living. These have been found frequently in the Fiatford area particularly in the upper region of the Stour estuary between Cattawade Bridge and Judas Gap. They live in Chambers in stiff mud or clay, usually on the eroded edge of a salt marsh ; upwards of twenty animals may congregate in a single Chamber.

The sexes in mature animals are markedly dimorphic and females are distinguishable at a glance by the swollen form of the thorax and are usually more numerous than males in the mud Chambers.

FLATFORD MILL FIELD CENTRE

159

Pleurobrachia pilens (O. F. Muller).

DĂźring the past 15 months Pleurobrachia pilens has been taken in small numbers at all seasons in the large tidal lagoon at Shingle Street. The animal is carnivorous and at Shingle Street the chief food appears to be Praunus flexuosus an opossum shrimp occurring in larger numbers there.

This crustacean has been found in the enteron of Pleurobrachia on a number of occasions.

Orchestia bottae Milne Edwards.

On August 2nd, 1958, several sand hoppers (resembling freshwater shrimps) were found amongst damp stones and soil on the margin of Dedham Mill Pool. These proved to be Orchestia bottae (Crustacea Amphipoda). Sand hoppers are typically maritime, and there is a number of British species occurring in various habitats round our coasts. O. bottae is exceptional in that it is an inland species. It is apparently very local in its distribution and only one of the recorded localities in East Anglia is the River Yare at Brundali, Norfolk.

Early in September, 1958, more individuals were found at Dedham, on this occasion under damp moss on the lock gates.

Further investigations may prove that this species is widespread on the banks of Suffolk rivers.

SUFFOLK by

F. W.

WILLOWS SIMPSON

THE Willows form an important part of our flora and there is hardly a marsh, damp wood, river bank, stream, pond, flooded quarry or waste place where they do not occur. Plantations of various kinds can be seen in all areas. Osiers have been extensively cultivated near Stowmarket and other towns for very many years. However, many of the beds are now much overgrown and neglected since there has been a decline in the demand for baskets and other articles which were formerly made locally in considerable numbers.