Worm Breeder's Gazette 14(3): 26 (June 1, 1996)

These abstracts should not be cited in bibliographies. Material contained herein should be treated as personal communication and should be cited as such only with the consent of the author.

Is there Regenerative Capacity in the Enoplida (Nematoda)?

Roy Douglas Pearson

Science & Medicine Library, University of Toronto, 9 Kings College Circle, Toronto, Ont. M5S 1A5 (PEARSONR@vax.library.utoronto.ca)

     There is precious little in the literature regarding the
regenerative ability of nematodes (Poinar, 1988).  The received
wisdom has been that the determinate cleavage in these pseudocoelomates
precludes any possibility of epimorphic regeneration (K.A. Wright
pers. comm., 1988).  Although Filipjev (1921) stated that regeneration
is "completely absent" in nematodes, other reports by Micoletzky and
Kreis (1930) and Allgen (1959) present another picture which seemingly
contradicts such a blanket generalization.
     Last year it was reported that a gastrotrich (undescribed species
of Turbanella) of the genera Macrodasyidae, a primitive sister group
of the Nematoda, restored epidermis with complete wound closure 
following transection; restructuring of Y organ and intestine; and
caudal adhesive tubes forming anew (Manylov, 1995).  This is the first
report of regeneration in this group.
     In another recent paper from the former Soviet Union, Voronov and
Panchin (1995a) report that a nematode, of the order Enoplida
(E.brevis), has a process of gastrulation which contradicts the
patterns of cleavage formerly ascribed to the Enoplida (Malakhov,1994).
They observed that up to the sixteenth cell stage cleavage is usually
(though this can vary) equal and synchronous, producing blastomeres of
equal appearance; elsewhere they observe that the primordia which gives
rise to all the endoderm can be derived from either the anterior or
posterior at the two-cell stage (Voronov and Panchin,1995b).  This
variability, they offer, makes the Enoplida different from other 
nematodes studied.  Malakhov believes that this variability "can
even engender the idea that the cleavage among members of marine 
Enoplida is indeterminate, but this is not so." (p.166).  However,
the cleavage of the Enoplida may be indeterminate enough to allow for
the regenerative phenomena recently witnessed in a gastrotrich.
     In sum, Enoplid cleavage patterns would appear to be similar
to the more primitive patterns seen in the Macrodasyidae, which is
consistent with the notion that equal cleavage is ancestral and 
determination of early blastomere fate derived (Baguna and Boyer,1990).
Also, it should be remembered that in addition to the single species
reported by Micoletzky and Kreis, all nine of the species which Allgen
found evidence of regeneration were marine Enoplids.

Allgen,C.A.(1959)Free living marine nematodes.  Further Zool. Results
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Baguna,J.,B.C.Boyer(1990)Descriptive and experimental embryology of
     the Turbellaria: Present knowledge, open questions and future
     trends.  In Marthy, H.(ed), Experimental Embryology in Aquatic 
     Plants and Animals.  NATO ASI 195; 95-128.
Filipjev,I.N.(1921)Free living nematodes in the vicinity of Sevastapol.
     (in Russian), Akad. Nauk SSSR. Trudy osob. zool. lab. ser 2
     41: 351-614.
Malakhov,V.V.(1994)Nematodes: Structure, Development, Classification
     and Phylogeny. Smithsonian Inst. Press.
Manylov,O.G.(1995)Regeneration in Gastrotricha - I. Light microscopical
     observations on the regeneration in Turbanella sp. . Acta Zool.
Micoletzky,H.,H.A.Kreis(1930)Freilbende marine Nematoden von den
     sunda-Inseln. Dansk natur. Foren. Vid. medd. Bd 87: 243-339.
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     Nematodes. vol 1, p.133-40, CRC Press, Boca Raton, Florida.
Voronov,D.A.,Y.V.Panchin(1995a)The early-stage of the cleavage in the
     free-living marine nematode Enoplus brevis (Enoplida, Enoplidae)
     in the normal and experimental conditions. Zool. Zhurn. 74(6):
Voronov,D.A.,Y.V.Panchin(1995b)Gastrulation in the free-living marine 
     nematode Enoplus brevis and the localization of endodermal 
     material at the stage of 2 blastomeres in the nematodes of the
     order Enoplida.  Zool. Zhurn. 74(10): 10-18.