Marine Flora and Fauna of the Northeastern 

 United States. Sipuncula 



EDWARD B. CUTLER' 



ABSTRACT 



This report includes an account of the five species of Sipuncula living in shallow waters (down to 

 200 m) from Maine to Virginia. Four of these are widespread elsewhere in the world — Golfingia 

 eremita. G. margaritacea, G. minuta. and Phaseolion strombi. PhaacolopsU gouldi is endemic to the 

 east coast of North America. An introduction to their biology, an annotated systematic list, selected 

 bibliography, and an illustrated key are presented. 



INTRODUCTION 



The Sipuncula (peanut worms) are marine, seden- 

 tary, vermiform coelomates which lack any trace of seg- 

 mentation, although related to the annelids. They are 

 found in all oceans and live within the sediment or in- 

 side a protective shelter such as a discarded mollusc shell 

 (pteropod, gastropod, or scaphopod), foraminiferan test, 

 polvchaete tube, or crevice in rock or coral. 



Sipunculans have two body regions: the trunk (or 

 body) and a retractable introvert (Fig. 1A). The mouth is 

 located at the tip of the introvert and is usually sur- 

 rounded by tentacles of varying degrees of development 

 and complexity. Behind the tentacular region is a zone 

 which may bear chitinous, posteriorly directed hooks 

 which are scattered or arranged in regular rings. The in- 

 trovert may be less than half the trunk length in some 

 species to many times its length in others. The demarca- 

 tion between these two regions is usually defined by the 

 abrupt narrowing of the diameter where the introvert 

 begins. This area generally coincides with the position of 

 the anus or nephridiopores, or both. Sipunculans range 

 in trunk length from less than 2 mm to over 300 mm, but 

 in the northeastern Atlantic they are more commonly 

 between 3 and 30 mm. 



The shape of the body may vary from almost spherical 

 to cylindrical. In those forms inhabiting discarded gas- 

 tropod shells, the living worm retains the spiral shape of 

 its shell even after it is removed. Sipunculans have a 

 variety of epidermal structures such as papillae, hold- 

 fasts, and hooks. The papillae are glandular structures 

 which produce material which is thought may function in 

 i (instructing or maintaining burrows or tubes. Generally, 

 pigmentation is scant but when present, it is in shades of 

 yellow or brown and is not ordinarily useful for iden- 

 tification. 



The internal anatomy of these worms is relatively sim- 

 ple (Fig. IB). The digestive tract has a straight esoph- 

 agus and a double-coiled intestine extending towards 



I'tk-a Toiler ,,f Syracuse University. Utica, NY 13502. 



the posterior end of the body. The tract terminates in a 

 rectum, which may bear a small caecum. The dorsal 

 anus is located at the anterior end of the trunk except in 

 a few species where it is in the midregion and in one 

 genus (Onchnesoma) where it is on the introvert. The 

 distal part of the rectum is anchored to the body wall by 

 a sheet of muscle tissue referred to as the wing muscles. 

 Near the anus a long strand of muscle tissue originates 

 from the body wall and extends down the center of the 

 gut coil, increasing its stability; this is the spindle mus- 

 cle. It may terminate within the coil or extend beyond to 

 the posterior end of the trunk. In addition, the worm 

 may have fixing muscles, which are fine muscle strands 

 anchoring the gut coils or esophagus to the body wall. 



One or usually two simple, saclike nephridia 

 (sometimes called segmental organs) open on the ven- 

 tral side at the anterior end of the trunk. The nephridia 

 are always attached to the body wall at the neph- 

 ridiopores and sometimes are attached by more exten- 

 sive mesentery along some portion of their length. The 

 nephridiopores themselves, in most species, are not dis- 

 cernible externally. The longitudinal and circular 

 muscles of the body wall are frequently arranged in 

 smooth, uniform layers but also may be gathered into 

 bundles. One, two, or four retractor muscles control the 

 introvert. A ventral nerve cord with lateral nerves and a 

 pair of cerebral ganglia are present. Two or four pig- 

 mented eyespots may be present on the cerebral ganglia. 



Our knowledge of the reproductive biology of east coast 

 sipunculans is scanty. Rice (1967, 1973, 1975) has given 

 the most current statement of our knowledge on develop- 

 mental patterns in Sipuncula. Gerould (1907) gave an ac- 

 count of the development of Phascolopsis gouldi. Good 

 information on breeding cycles is unavailable for most 

 species. Gametes are produced from a strip of gonadal 

 tissue at the base of the ventral retractor muscles. They 

 are released into the coelom at an early stage where they 

 undergo the remainder of their growth and differentia- 

 tion as freely floating cells. 



Gibbs (1975), working with Golfingia minuta pop- 

 ulations, found monoecious animals in the eastern At- 

 lantic but not in the western Atlantic. With the possible 



