Tuesday, June 15, 2010

Recent Publications On Meiofauna


Dongsung Kim1 and Yoshihisa ShirayamaContact Information
(1)  Marine Living Resources Research Division, Korea Ocean Research & Development Institute, Ansan P.O. Box 29, Seoul, 425-600, Korea
(2)  Seto Marine Biological Laboratory, Graduate School of Science, Kyoto University, Shirahama-cho, Wakayama 649-2211, Japan

Received: 10 September 2009  Revised: 24 November 2009  Accepted: 24 November 2009  Published online: 25 March 2010
Ingestion rates of free-living marine nematodes were measured using colloidal iron as a tracer. Detritus labeled with colloidal iron was fed to the dominant nematode species and cultured. The iron ingested by the animals was quantified using a scanning electron microscope equipped with differential X-ray energy analyzer (EDX). Average ingestion rates (µgC ind.−1day−1) measured were 0.28 for Symplocostoma sp., 0.29 for Polygastrophora sp., 0.73 for Mesacanthion sp. and 0.15 for Metachromadora sp. These values were higher than the values determined using radioactive organic materials as tracers, though the present method is considered to provide conservative values. This result thus strongly suggests that the ingestion rates of nematodes measured so far were underestimated, and the use of colloidal iron has advantages over the use of radioactive organic matter as a tracer.
Keywords  Ingestion rates - nematodes - colloidal iron - EDX - subtidal

Maria BalsamoContact Information, L. Guidi1, M. Ferraguti2, L. Pierboni1 and R. M. Kristensen3
(1)  Dipartimento di Scienze dell’Uomo, dell’Ambiente e della Natura, Università di Urbino, Urbino, Italy
(2)  Dipartimento di Biologia, Università di Milano, Via Celoria 26, 20133 Milan, Italy
(3)  Zoological Museum, Natural History Museum, University of Copenhagen, Universitetsparken 15, 2100 Copenhagen OE, Denmark

Received: 4 February 2009  Revised: 30 April 2009  Accepted: 11 May 2009  Published online: 30 June 2009
Communicated by H.-D. Franke.
Abstract  The genus Diuronotus (Gastrotricha Chaetonotida) includes two species, D. aspetos and D. rupperti; its morphological affinity with the genus Musellifer has been pointed out. Here, new morphological data from light and electron microscopy and the description of the spermatozoon of D. aspetos are reported, with the aim of clarifying the phylogenetic position of the genus. The mouth cavity has a wreath of stout, protrusible processes. The two secondary furcal tubes are inserted ventrally and are covered with elongate scales. All the caudal tubes contain a duo-gland adhesive system. Three kinds of ciliated sensory receptors are described for the first time in Diuronotus. The filiform spermatozoon consists of an acrosome, a nuclear-mitochondrial complex, and a flagellum. The acrosome including two long and different cones, the single, giant mitochondrion surrounding the nuclear base, and the axoneme arising from a deep nuclear ‘fossa’ appear as autapomorphic characters. The keeled, solid cuticular body scales and the spermatozoon with a supernumerary membrane are features shared with Musellifer delamarei. The structure of the accessory fibres is a strong spermatological similarity between the families Muselliferidae and Xenotrichulidae. Thus morphological and spermatological characters support the inclusion of D. aspetos and M. delamarei into the family Muselliferidae recently described. The comparative spermatology also suggests that Xenotrichulidae may be the sister group of Muselliferidae.

Keywords   Diuronotus aspetos  - Gastrotricha - Chaetonotida - Ultrastructure - Spermatozoon 


Ilse BartschContact Information
(1)  Forschungsinstitut Senckenberg, DZMB, c/o DESY, Notkestr. 85, 22607 Hamburg, Germany
Received: 9 April 2009  Revised: 14 October 2009  Accepted: 2 November 2009  Published online: 24 November 2009
Isobactrus is a worldwide-spread genus. Most species live in the upper and middle area of a more or less regularly emerged zone. The species diversity is distinctly higher in the northern than in the southern hemisphere. At present, the genus consists of 29 species. An analysis of the geographical distribution of 36 external morphological characters revealed a uniformity in the combination of states of northern Pacific species, but a heterogeneity in the characters of northern Atlantic species. Several character states demonstrate a distinct north/south or north/tropics/south distribution. A parsimony analysis revealed basal northern Atlantic clades, a northern Pacific clade that also includes Northern Atlantic species and an Indo-Pacific clade with a tropical area cluster. The present data suggest that the genus Isobactrus evolved in the Palaearctic Ocean and might represent a basal lineage within the family Halacaridae.

Keywords  Halacaroidea - Characters - Distribution - Phylogeny - Palaearctic Ocean 

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