280
THE ESSEX NATURALIST
Skippers Island Papers
(8) FURTHER RECORDS OF FREE-LIVING NEMATODES
FROM SKIPPERS ISLAND
By John W. Coles
(Department of Zoology, British Museum (Natural History))
Some years ago Coles (1960) published a note on free-living
nematodes, as a contribution to the general ecology of Skippers
Island in the parish of Thorpe le Soken, Essex. Since then Mr
A. C. Wheeler has kindly collected three more samples of mud
and algae from the shore of, and from a 'lagoon' within, Skippers
Island. Of the forty-six nematode species which have been
found most have been reported previously from European waters
while six are new records to the British fauna. Brief descriptions
and figures of many of these species are given by Schuurmans
Stekhoven (1935).
Sample 1. Soil (mud bound together by plants) surround-
ing the roots of the sea aster (Aster tripolium) and glasswort
(Salicornia sp.) from 'saltings'. Collected in June 1960. The
saltings are flooded at high water of all spring tides when they
are totally submerged for an hour or more with sea water, but at
high water of neap tides the sea only just covers the soil.
Although some dilution must occur during heavy rain the soil
is always saturated with sea water. Most of the eighteen species
found in this sample are typical marine forms, but two belong to
a genus (Haliplectus) which is typically brackish, and one belongs
to a genus (Dorylaimus) which is well known from soil and fresh-
water although some species of it have previously been found in
the sea.
Sample 2. Algae (Enteromorpha sp.) and mud from a small
pond ('lagoon') in a low-lying part of the island, collected on the
last day of March 1961. The pond is flooded with sea water at
high water of spring tides but not by neaps. It is about 40' x 15'
in size with an average depth of one foot and sides of clay banks.
The only macro-flora consists of green 'Enteromorpha-type' weed
which in summer forms a dense blanket overall. The macro-fauna
consists of fish: gobies (Gobius microps), sticklebacks (Gasteros-
teus aculeatus), young eels (Anguilla anguilla); Molluscs: many
small cockles (Cardium edule), Hydrobia sp.; and Crustacea:
Crangon vulgaris, Corophium volutator, Gammarus sp. The
twenty species of nematodes found are all typically marine.
Sample 3. Marine mud collected from the shore, above the
dam but below the level of low water, in October 1961. For
position of locality see map in Nisbet (1961). This sample was
taken from approximately the same locality as Sample 5 of the
previous note (Coles, 1960). Twenty-three species of nematodes
were found, all typically marine.