The marine flora and fauna of the Isles of Scilly: Free-living Plathelminthes (‘ Turbellaria’) Author Faubel, A. Author Warwick, R. M. text Journal of Natural History 2005 2010-12-06 39 1 1 45 http://dx.doi.org/10.1080/00222930310001613593 journal article 10.1080/00222930310001613593 1464-5262 4668745 Haplogonaria arenicolae sp. nov. ( Figure 1 ) Material examined HOLOTYPE : Site 2b: one specimen, in squash preparation, within tubes of Arenicola marina L., stored on CD-ROM: 2003.5.22.6. Etymology The specific name refers to the occurrence of the species in tubes of Arenicola marina L. Description Length of body of sexually mature specimen up to 1.2 mm ; maximum width anterior to mid-body ( Figure 1 ); posterior body-third tapering to a pointed end. In transmitted light marginal parts of body yellowish grey; digestive parenchyme strongly granulated contrasting dark grey. Frontal organ present; from frontal tip of body prominent coiling glandular ducts run caudad, the glands of which lie postero-lateral of the statocyst. Statocyst 130 M m distant from frontal tip. Rhabdoids and eyes absent. Mouth opening at the transition from first to second body-fourth. Figure 1. Haplogonaria arenicolae sp. nov. Dorsal view in squash preparation. Scale bar: 200 M m. Reproductiυe system. Bilateral testes ventral at transition from second to third body-fourth. Single ovary anterior to mid-body. Maturing oogonia are successively displaced caudad into bilateral rows. The seminal vesicle enters the male atrium proximally via a very short duct. At the beginning of the last body-fourth, the male atrium opens to the exterior (about 290 M m from hind end). Seminal bursa anterior to the male copulatory organ; any insemination apparatuses absent. Genital pores separate. Discussion Haplogonaria arenicolae was found only once and could only be observed in squash preparation. Therefore, serial sections or whole mounts could not be prepared. The morphological structures were stored on a CD-ROM on which the following description of the morphology of H. arenicolae is based. Up to now the genus Haplogonaria contains 13 valid species and a species nomen nudum , Haplogonaria sp. 1 Yamasu and Okazaki, 1987. The present species is a valid member of the genus Haplogonaria based on the characters of a single ovary, seminal bursa without any insemination apparatuses and lack of a penis or cirrus. With respect to the structure of the seminal bursa, without insemination apparatuses, and absence of rhabdoids, H. arenicolae closely resembles H. elegans Faubel, 1976 . The most conspicuous characters of H. arenicolae are the single ovary, generating germ cells which are displaced successively into bilateral rows of oogonia maturing to oocytes, separate gonopores and the much larger body (cf. Faubel 1976b ). Both the species H. elegans and H. arenicolae preferentially inhabit the deeper layers of oxic sediments, particularly in the oxidized layers of tubes of Arenicola marina L.