PLATYHELMINTHES (TURBELLARIA)

P.E. Tompsett & S.M. Turk

Turbellarians form a component of the marine meiofauna with a wide size range 1mm – 200+mm. Despite their size, these unsegmented, often leaf-like, marine flatworms are poorly known, being fragile and very easily damaged during collection and examination. They are found amongst algae and bryozoa on rock or mixed sand substrates in shallow water on lower intertidal or subtidal sites. A taxonomic collection survey on the Isles of Scilly in May 2002 revealed 67 species of Turbellaria, of these, 46 species were mature and readily identifiable, six were new to science whilst 15 were juveniles (Faubel & Warwick, 2005). The assistance of R.M. Warwick is gratefully acknowledged. The numbers of specimens in recorded locations is not necessarily related to true abundance whilst nationally and internationally there is a distinct ‘Deficiency of data’ for individual species.

1. Species occurring in the Isles of Scilly and possibly Cornwall, many only recently identified, which could be considered as provisionally Red Data Book species.

Archimacrostomum sublitorale

Bradynectes scilliensis

Haplogonaria arenicolae

Haplovejdovskya scilliensis

Paromalostomum scilliensis

Scillyvortex phytophilus

2. Species occurring in Cornwall and the Isles of Scilly which could be considered as provisionally Nationally Scarce.

(N.B. All sites SA19 and reference Faubel & Warwick, 2005, unless otherwise indicated)

2.1. Acoela

Small (1-5 mm) common flatworms which inhabit marine or brackish water sediments; a few are planktonic or symbiotic.

Actinoposthia haplovata Dörjes

Antropostia unipora Faubel

Aphanostoma album Dörjes

Atriofronta polyvacuola Dörjes

Eumecynostomum papillosum (Faubel) Faubel & Regier

Haplogonaria simplex Dörjes

Haplogonaria syltensis Dörjes

Mecynostomum auritum (Schultze) Van Benenden SA18; SA19, IOS Recorded from English Channel

Notocelis gullmarensis (Westblad) Dörjes

Oligophilomorpha interstitiophilum Faubel

Pelophila lutheri (Westblad) Karling

Philactinoposthia adengonaria Dörjes

Philomecynostomum lapillum Dörjes

Praeconvoluta minor Faubel

Pseudoaphanostoma psammophilum Dörjes

Simplicomorpha gigantorhabditis Dörjes

Simsagittifera schultzei (Schmidt) Kostenko & Mamkaev SA18; SA19, IOS Previously recorded from Plymouth Sound

2.2. Macrostomida

Small and predominantly interstitial; marine or freshwater.

Haplopharynx rostratus Meixner

Microstomum jenseni Reidel

Microstomum papillosum v. Graff

2.3. Polycladida

A diverse group of relatively large turbellarians, with a flattened body up to 15cm in length. They are predominantly marine, benthic and free-living, although a few are pelagic or symbiotic.

Leptoplana tremellaris (Müller) Oersted SA18; SA19, IOS Previously recorded from Plymouth Sound. (Prudhoe 1982, Faubel & Warwick, 2005).

Oligocladus sanguinolentus  (Quatrefages) Lang SA18; SA19, IOS Previously recorded from Plymouth Sound (Prudhoe 1982, Faubel & Warwick, 2005).

Prostheceraeus vittatus (Montagu) Lang SA18; SA19, IOS Previously recorded from Falmouth and Plymouth Sound (Prudhoe 1982, Faubel & Warwick, 2005).

Prosthiostomum siphunculus delle Chiaje SA18 Found “On oyster beds, among shell and algae in depths to 20m”; this species “Ranges along the west coast of Europe to western Mediterranean” and in European seas it is otherwise known only from the Channel Isles, Galway Bay and Plymouth area (Drake’s Island) (Prudhoe, 1982).

Stylochoplana agilis Lang SA18 In Britain known only from “Plymouth” and Dorset (Prudhoe, 1982).

Stylostomum ellipse (Dalyell) Lang SA18; SA19, IOS Previously recorded from Falmouth and Plymouth Sound (Prudhoe 1982, Faubel & Warwick, 2005).

Thyanozoon brocchi (Risso) SA18 The only British locality is “Plymouth” (Prudhoe, 1982).

2.4. Prolecthophora

Small, free-living, marine or freshwater.

Acmostomum dioicum Mecznikow

Monoophorum tubiferum (Westblad) Karling

Plagiostomum striatum Westblad

Vorticeros auriculatus (Müller) v.Graff  SA18; SA19, IOS Previously recorded from Plymouth Sound. (Prudhoe 1982, Faubel & Warwick, 2005).

2.5. Proseriata

Most are free-living, marine.

Archotoplana holtricha Ax

Monocelis lineata (Müller) Ehrenberg SA18; SA19, IOS Previously recorded from Plymouth Sound. (Prudhoe 1982, Faubel & Warwick, 2005).

Monocelopsis cf. septentrionalis (Sopott) Martens & Curinin-Galletti

Parotoplana capitata Meixner

Parotoplana multispinosa Ax

2.6. Rhabdocoela

A large and diverse group with both free-living and symbiotic taxa found in marine and freshwater habitats.

Balgetia cf. semicirculifera Karling in Luther

Carcharodorhynchus subterraneus Meixner

Cheliplanilla caudata Meixner

Gyratrix hermaphroditus Ehrenberg

Litucivis serpens Ax & Heller (Prudhoe 1982, Faubel & Warwick, 2005).

Maeharenthaliella intermedia (v.Graff) Karling

Paulodora riedli (Karling) Artois & Schockaert

Phonorhynchus helgolandicus (Mecznikow) v.Graff SA18; SA19, IOS Previously recorded from Plymouth Sound.

Polycystis naegelii Kölliger SA18; SA19, IOS Previously recorded from Plymouth Sound.

Promesostoma cochleare Karling

Promesostoma meixneri Ax

Rogneda hibernica (Southern) Karling SA18; SA19, IOS Previously recorded from Cawsand and Plymouth Sound.

Trigonostomum penicillatum (Schmidt) Micoletzki SA18; SA19, IOS Previously recorded from Plymouth Sound.

2.7. Tricladida

Marine or freshwater, with some terrestrial species. Most are free-living, including the familiar planarians. Ball & Reynoldson (1981) list four British marine species. Three of these are Cornish and one has a very limited distribution.

Procerodes lobata