Open Access Open Access  Restricted Access Subscription or Fee Access


A cultivable acoel species from the Mediterranean, Aphanostoma pisae sp. nov. (Acoela, Acoelomorpha)



Aphanostoma pisae sp. nov. is an interstitial acoel found at the coast of the Liguric Sea in Pisa (Tuscany, Italy). It belongs to the large family Isodiametridae, characterised by a male copulatory organ with a cylindrical shape and non-anastomising longitudinal muscle fibers. It is the first recognised species of Aphanostoma in the Mediterranean and it can occur in great abundance at its type locality (several hundred specimens in a spoonful of sand). A. pisae has been cultured in the laboratory for several years with diatoms for food. The embryonic development lasts for just under two days at 20 °C.

        We provide a description of the new species using live observations, light and electron microscopy of sagittal sections and stainings of the filamentous actin and the serotonergic nervous system, and we discuss and update the genus diagnoses of the genera Aphanostoma and Praeconvoluta.



Xenacoelomorpha, acoel flatworm, taxonomy, phalloidin, antibody stainings

Full Text:

PDF/A (11.67 MB)


Achatz, J.G. & Martinez, P. (2012) The nervous system of Isodiametra pulchra (Acoela) with a discussion on the neuroanatomy of the Xenacoelomorpha and its evolutionary implications. Frontiers in Zoology, 9, 27.

Beklemischev, V.N. (1915) Sur les turbellariés parasites de la côte Mourmanne. I. Acoela. Travaux de la Société impériale des naturalistes de St. Petersbourg, 43 (4), 103–172.

Diesing, K.M. (1862) Revision der Turbellarien. Abtheilung: Rhabdocoelen. Sitzungsberichte der Mathematisch-Naturwissenschaftlichen Classe der Kaiserlichen Akademie der Wissenschaften Abtheilung 1, 45, 191–318.

Dörjes, J. (1968) Die Acoela (Turbellaria) der deutschen Nordseeküste und ein neues System der Ordnung. Journal of Zoological Systematics and Evolutionary Research, 6, 56–452.

Dörjes, J. (1972) Faerlea echinocardii sp. n. und Diskussion der Gattungen Avagina Leiper und Faerlea Westblad (Turbellaria Acoela). Zoologica Scripta, 1 (3), 185–189.

Egger, B. & Ishida, S. (2005) Chromosome fission or duplication in Macrostomum lignano (Macrostomida, Plathelminthes)—remarks on chromosome numbers in "archoophoran turbellarians". Journal of Zoological Systematics and Evolutionary Research, 43 (2), 127–132.

Egger, B., Steinke, D., Tarui, H., De Mulder, K., Arendt, D., Borgonie, G., Funayama, N., Gschwentner, R., Hartenstein, V., Hobmayer, B., Hooge, M., Hrouda, M., Ishida, S., Kobayashi, C., Kuales, G., Nishimura, O., Pfister, D., Rieger, R., Salvenmoser, W., Smith III, J., Technau, U., Tyler, S., Agata, K., Salzburger, W. & Ladurner, P. (2009) To be or not to be a flatworm: The acoel controversy. PLoS ONE, 4 (5), e5502.

Ehlers, U. (1985) Das Phylogenetische System der Plathelminthes. Gustav Fischer, Stuttgart & New York, 317 pp.

Eisenman, E.A. & Alfert, M. (1982) A new fixation procedure for preserving the ultrastructure of marine invertebrate tissues. Journal of Microscopy, 125, 117–120.

Faubel, A. (1974) Die Acoela (Turbellaria) eines Sandstrandes der Nordseeinsel Sylt. Mikrofauna des Meeresbodens, 32, 1–58.

Faubel, A. (1977) Zwei neue interstitielle Arten der Acoela (Turbellaria) von Norwegen. Zoologica Scripta, 6 (1), 21–25.

Faubel, A. & Regier, S. (1983) Anatomy and taxonomy of new Acoela (Turbellaria) from the sublittoral of the northern North Sea. Senckenbergiana maritima, 15 (1), 1–17.

Hooge, M.D. (2001) Evolution of body-wall musculature in the Platyhelminthes (Acoelomorpha, Catenulida, Rhabditophora). Journal of Morphology, 249 (3), 171–194.

Hooge, M.D. & Rocha, C.E.F. (2006) Acoela (Acoelomorpha) from the northern beaches of the state of São Paulo, Brazil, and a systematic revision of the family Otocelididae. Zootaxa, 1335, 1–50.

Hooge, M.D. & Tyler, S. (1999) Body-wall musculature of Praeconvoluta tornuva, n. sp. (Acoela, Platyhelminthes) and the use of muscle patterns in taxonomy. Invertebrate Biology, 118 (1), 8–15.

Hooge, M.D. & Tyler, S. (2003) Acoels (Platyhelminthes, Acoela) from the Atlantic coast of North America. Meiofauna Marina, 12, 7–36.

Hooge, M.D. & Tyler, S. (2005) New tools for resolving phylogenies: a systematic revision of the Convolutidae (Acoelomorpha, Acoela). Journal of Zoological Systematics and Evolutionary Research, 43 (2), 100–113.

Hooge, M.D. & Tyler, S. (2008) Acoela (Acoelomorpha) from Bocas del Toro, Panama. Zootaxa, 1719, 1–40.

Jensen, O.S. (1878) Turbellaria ad litora Norvegiae occidentalia. Turbellarier ved Norges Vestkyst. J.W. Eided Bogtrykkeri, Bergen, 97 pp.

Jondelius, U., Wallberg, A., Hooge, M. & Raikova, O.I. (2011) How the worm got its pharynx: phylogeny, classification and Bayesian assessment of character evolution in Acoela. Systematic Biology, 60 (6), 845–871.

Kozloff, E.N. (1965) New species of the acoel turbellarians from the Pacific coast. Biological Bulletin, 129, 151–166.

Ladurner, P. & Rieger, R.M. (2000) Embryonic muscle development of Convoluta pulchra (Turbellaria: Acoelomorpha, Platyhelminthes). Developmental Biology, 222 (2), 359–375.

Meixner, J. (1938) Turbellaria (Strudelwürmer). In: Grimpe, G. & Wagler, E. (Eds.), Die Tierwelt der Nord- und Ostsee. Vol. 33 (IVb). Akademische Verlagsgesellschaft, Leipzig, pp. 1–146.

Mollenhauer, H.H. (1964) Plastic embedding mixtures for use in electron microscopy. Stain Technology, 39 (2), 111–114.

Nilsson, K.S., Wallberg, A. & Jondelius, U. (2011) New species of Acoela from the Mediterranean, the Red Sea, and the South Pacific. Zootaxa, 2867, 1–31.

Nimeth, K.T., Egger, B., Rieger, R., Salvenmoser, W., Peter, R. & Gschwentner, R. (2007) Regeneration in Macrostomum lignano (Platyhelminthes): cellular dynamics in the neoblast stem cell system. Cell and Tissue Research, 327, 637–646.

Ørsted, A.S. (1845) Fortegnelse over Dyr, samlede i Christianafjord ved Drøbak. Naturhistorisk Tidsskrift udgivet of Henrik Krøyer, Series 2, 1, 400–427.

Pereyaslawzewa, S. (1892) Monographie des turbellaries de la Mer Noire. Schriften der neurussischen naturforschenden Gesellschaft, 17 (3), 1–303.

Petrov, A., Hooge, M. & Tyler, S. (2006) Comparative morphology of the bursal nozzles in acoels (Acoela, Acoelomorpha). Journal of Morphology, 267 (5), 634–648.

Philippe, H., Brinkmann, H., Copley, R.R., Moroz, L.L., Nakano, H., Poustka, A., Wallberg, A., Peterson, K.J. & Telford, M.J. (2011) Acoelomorph flatworms are deuterostomes related to Xenoturbella. Nature, 470 (7333), 255–260.

Reuter, M., Raikova, O.I. & Gustafsson, M.K.S. (2001) Patterns in the nervous and muscle systems in lower flatworms. Belgian Journal of Zoology, Supplement 1 (131), 47–53.

Richardson, K.C., Jarret, L. & Finke, E.H. (1960) Embedding in epoxy resins for ultrathin sectioning in electron microscopy. Stain Technology, 35 (6), 313–323.

Romeis, B. (1968) Mikroskopische Technik. R. Oldenbourg Verlag, München, 757 pp.

Ruiz-Trillo, I., Riutort, M., Littlewood, D.T., Herniou, E.A. & Baguña, J. (1999) Acoel flatworms: earliest extant bilaterian Metazoans, not members of Platyhelminthes. Science, 283 (5409), 1919–1923.

Salvenmoser, W., Egger, B., Achatz, J.G., Ladurner, P. & Hess, M.W. (2010) Electron microscopy of flatworms: standard and cryo-preparation methods. Methods in Cell Biology, 96, 307–330.

Smith, J.P.S. & Bush, L. (1991) Convoluta pulchra, n. sp., (Turbellaria: Acoela) from the east coast of North America. Transactions of the American Microscopical Society, 110, 12–26.

Spurr, A.R. (1969) A low-viscosity epoxy resin embedding medium for electron microscopy. Journal of Ultrastructure Research, 26 (1–2), 31–43.

Steinböck, O. (1933) Die Turbellarienfauna der Umgebung von Rovigno. Thalassia, 1, 1–33.

Tyler, S. & Rieger, R.M. (1999) Functional morphology of musculature in the acoelomate worm, Convoluta pulchra (Plathelminthes). Zoomorphology, 119 (3), 127–141.

Tyler, S., Schilling, S., Hooge, M. & Bush, L.F. (2006–2013) Turbellarian taxonomic database. Version 1.7. Available from: (accessed 1 November 2014).

Westblad, E. (1945) Studien über skandinavische Turbellaria Acoela. III. Arkiv för Zoologi, 36A (5), 1–56.

Westblad, E. (1948) Studien über skandinavische Turbellaria Acoela. V. Arkiv för Zoologi, 41A (7), 1–82.


  • There are currently no refbacks.

ISSN 1175-5326 (Print Edition) & ISSN 1175-5334 (Online Edition)
Published by Magnolia Press, Auckland, New Zealand
A founding journal of Biotaxa