a student’s guide to the seashore || priapula

Priapula The priapulans are benthic, marine animals varying in length from a millimetre or so to about 200 mm. There are only a few species in the phylum. The body is divided into two distinct parts, an anterior proboscis and a posterior trunk. The proboscis is the shorter of the two regions and is retractile and covered with a large number of spines. The mouth is terminal. In some species, the posterior region of the body bears one or two much branched processes. The trunk often has papillae on the surface and is annulated, but the body is not segmented. The animals live in sandy and muddy sediments on the lower shore and in the sublittoral. They are carnivorous, feeding on polychaete worms and other invertebrates captured by means of the proboscis. The sexes are separate and the gametes are discharged into the sea where fertilization occurs. The larvae live in soft sediments. Priapulus caudatus Lamarck (Fig. 72) Body elongate, cylindrical up to 150 mm in length. Large proboscis with rows of spines. Posterior of trunk with single, much branched process, Pinkish-brown in colour. P. caudatus is widely distributed but not common in north-west Europe, burrowing in mud, muddy-gravel and muddy-sand from the lower shore into the sublittoral. It is carnivorous, feeding on polychaete worms such as Aphrodita (p. 143) and brittle-stars. The sexes are separate, fertilization external and breeding has been recorded in winter in specimens from the North Sea. The larvae inhabit the surface layers of sediment and are believed to feed on detritus. Development to the adult takes about two years. Stephen, A.c. 1960. British echiurids (Echiuroidea), sipunculids (Sipunculoida) and priapulids (Priapuloidea) with keys and notes for the identification of the species. Synopses of the British fauna (Series 1) No. 12. London: Linnean Society. 134 J. D. Fish et al., A Student’s Guide to the Seashore © J.D. Fish & S. Fish 1989

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Priapula

The priapulans are benthic, marine animals varying in length from a millimetre or so to about 200 mm. There are only a few species in the phylum. The body is divided into two distinct parts, an anterior proboscis and a posterior trunk. The proboscis is the shorter of the two regions and is retractile and covered with a large number of spines. The mouth is terminal. In some species, the posterior region of the body bears one or two much branched processes. The trunk often has papillae on the surface and is annulated, but the body is not segmented. The animals live in sandy and muddy sediments on the lower shore and in the sublittoral. They are carnivorous, feeding on polychaete worms and other invertebrates captured by means of the proboscis. The sexes are separate and the gametes are discharged into the sea where fertilization occurs. The larvae live in soft sediments.

Priapulus caudatus Lamarck (Fig. 72) Body elongate, cylindrical up to 150 mm in length. Large proboscis with rows of spines. Posterior of trunk with single, much branched process, Pinkish-brown in colour.

P. caudatus is widely distributed but not common in north-west Europe, burrowing in mud, muddy-gravel and muddy-sand from the lower shore into the sublittoral. It is carnivorous, feeding on polychaete worms such as Aphrodita (p. 143) and brittle-stars. The sexes are separate, fertilization external and breeding has been recorded in winter in specimens from the North Sea. The larvae inhabit the surface layers of sediment and are believed to feed on detritus. Development to the adult takes about two years.

Stephen, A.c. 1960. British echiurids (Echiuroidea), sipunculids (Sipunculoida) and priapulids (Priapuloidea) with keys and notes for the identification of the species. Synopses of the British fauna (Series 1) No. 12. London: Linnean Society.

134 J. D. Fish et al., A Student’s Guide to the Seashore© J.D. Fish & S. Fish 1989