Astrotorhynchus bifidus - A marine flatworm (Marine flatworm images)

Species approx. 1.0mm in length.

The species, flatworms and cocoons, was first found on a microscopic red algae, which was found growing on a US / Canadian shotgun cartridge that had been washed-up on the beach at Perranporth, Cornwall. 30.01.15 and also 01.04.15.

Species also found on Ascophyllum nodosum, Knotted or Egg wrack, which was covered in the hydroid Obelia geniculata and diatom Licmophora sp., that had washed-up at Gwithian Towans, Cornwall. 01.02.15. A lot of the material stated above was also washed-up at Perranporth on 30.01.15, at both sites Lepas pectinatus was sometimes attached to the Ascophyllum nodosum.

Ascophyllum nodosum, Knotted or Egg wrack was commonly found on both beaches above, at both sites it also had the hydroid Obelia geniculata and diatom Licmophora sp.. It is very probable the wrack has arrived here due to North Atlantic drift and as a result of harvesting of Ascophyllum in either NE USA, Canada or Ireland; it has therefore had enough time for Obelia geniculata to colonize it, and the diatom colonize the Obelia.

Hayward and Ryland in the Handbook of the marine fauna of North-West Europe, state Astrotorhynchus bifidus has been found in mid-shore pools near Swansea in July. However, ref. WoRMS, its distribution includes NW Atlantic waters from where the Ascophyllum nodosum and shotgun cartridge has thought to have drifted from. So the flatworm has probably crossed the Atlantic, and has possible been surviving on epiphytes or / and epizooytes that have fouled Ascophyllum.

Ascophyllum nodosum and other algal species that wash-up on shores like at Sennen are called drift weed. Drift weed can contain other algal as parasites, epiphytes etc., diatoms, but also micro and macro fauna, including nematodes, flatworms, marine annelids and even sea slugs, nudibranchs. There are is an old 19th century record for this species, found by F. W. Gamble at Port Erin, Isle of Man in 1893; Gamble describes Astrotorhynchus bifidus as being found on drift weed, which conveniently confirms what has recently been observed.

APHOTOMARINE

An educational resource dedicated mainly to the photography
and diversity of marine life that can be found in coastal waters
and intertidal areas of Great Britain and Ireland by David Fenwick.

APHOTOMARINE

An educational resource dedicated mainly to the photography and diversity of marine life that can be found in coastal waters and intertidal areas of Great Britain and Ireland by David Fenwick.

An educational resource dedicated mainly to the photography
and diversity of marine life that can be found in coastal waters
and intertidal areas of Great Britain and Ireland by David Fenwick.