The cirrus of a monogenean Diplectanum aequans was isolated by treatment with sodium carbonate solution and studied with a scanning electron microscope. The method may be used in studies of the functional morphology and taxonomy of other organism

Gonzalez, J.

Maillard, C.

Noisy, D.

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Parasitology (1982), 84, 63-64 6 3With 2 platesA scanning electron microscope study of the male copulatorysclerite of the monogenean Diplectanum aequansC. MAILLARD1, J. GONZALEZ2 and D. NOISY21 Laboratoire de Parasitologie Comparee, E.R.A. 915, Universite des Sciences etTechniques du Languedoc, PI. E. Bataillon, 34060 Montpellier Cedex, France.2 Institut de Biologie animale, Palais de Rumine, 1005 Lausanne, Switzerland.(Accepted 26 June 1981)SUMMARYThe cirrus of a monogenean Diplectanum aequans was isolated bytreatment with sodium carbonate solution and studied with a scanningelectron microscope. The method may be used in studies of the functionalmorphology and taxonomy of other organisms.INTRODUCTIONSclerotized structures are frequently used in both specific identifications andphylogenetic studies of helminths. Among the sclerites used for such purposes inmonogeneans are the male copulatory organs; these appear not to be subject tothe same degree of adaptative variation as the sclerites of adhesive organs.However, some of the copulatory sclerites are complex and have an intricate3-dimensional structure, the details of which are at the limit of resolution of thelight microscope.It was decided therefore to explore the use of the scanning electron microscope(S.E.M.) in elucidating the detailed structure of some sclerites and, mainly becauseof the availability of the Bass Dicentrachus labrax L. which is cultivated com-mercially in the south of France, its very common monogenean gill parasiteDiplectanum aequans (Wagener) was selected for our pilot study.MATERIALS AND METHODSAfter considerable trials the following method for fresh parasites was evolved.Specimens were fixed for 24 h in 70 % (v/v) ethanol and were then treated witha 40% (w/v) solution of sodium carbonate for about 6h to dissolve intercellularcement. They were transferred to a cover-slip previously coated with a thin layerof dilute rubber cement and excess sodium carbonate was removed with a pipette.A drop of distilled water was added to disrupt the parasite and disperse thesclerites. The water was allowed to evaporate, leaving the sclerites stuck by therubber cement to the slide. Cell debris was removed by washing and the specimenswere finally coated with metal, in the usual way, for scanning electron microscopy.RESULTSAs a result of treating specimens of D. aequans by the method described, thecirrus, hamuli and transverse bars were isolated but the other sclerites, namelythe spines of the squamodiscs and the marginal hooks, were never recovered.3-2https:/www.cambridge.org/core/terms. https://doi.org/10.1017/S0031182000051660Downloaded from https:/www.cambridge.org/core. University of Basel Library, on 11 Jul 2017 at 09:50:05, subject to the Cambridge Core terms of use, available at64 C. MAILLARD, J. GONZALEZ AND D. NOISYThe treatment with sodium carbonate appeared to dissolve material from withinthe hamuli, but the other sclerites recovered appeared to be undamaged.When examined with the S.E.M. the transverse bars yielded only a few detailsof structure beyond those revealed by light microscope studies, but much newinformation was obtained about the male copulatory organ, especially in regardto its distal region (PI. 1 A). The distal part tapers, then is recurved (PI. IB) andhollowed into a spoon (PI. 1C). In the concavity of some specimens an orifice isseen which is probably that of the canal running throughout the organ (PI. ID,arrow). The outer border of this zone, the flange, bears teeth which vary, indifferent individuals, in their number, form and arrangement.Near the distal end of the male sclerite there is always an isolated tooth lyingin a different plane from that of the more proximal teeth (PI. 2B,C). The proximalteeth vary in number and it is possible to recognize two types of dentition, onein which the flange bears 5—7 teeth restricted to the mid-region of the flange (PI.2A,C) and another in which there is a complete row of 9—12 teeth (PI. 2B,D).DISCUSSIONThe use of the S.E.M. has provided new information about the detailed structureof the male sclerite. This could lead to a better understanding of the functioningof this organ, for example, a possible relationship between its shape and that ofthe spermatophores produced by this parasite (Paling, 1966). Again, a variationwas discovered in the arrangement and number of teeth at the distal end of themale sclerite, and it is possible that these variations could be of use, for example,in comparing specimens of D. aequans from different geographical locations.Further work will be necessary to overcome the difficulties we experienced inrecovering certain sclerites, but the method is promising and may be capable ofapplication to other parasites.We are grateful to Professors L. Euzet and J. Llewellyn for their help and useful criticismsin the preparation of this paper.REFERENCEPALING, J. E. (1966). The functional morphology of thegenitaliaofthespermatophore-producingmonogenean parasite Diplectanum aequans (Wagener) Diesing, with a note on the copulationof the parasite. Parasitology 56, 367-83.EXPLANATION OF PLATESPLATE 1A. The cirrus of Diplectanum aequans in toto.C-D. Distal end of the cirrus of several specimens of Diplectanum aequans observed fromdifferent angles.PLATE 2A-D. Distal end of the cirrus of several specimens of Diplectanum aequans observed fromdifferent angles.Printed in Great Britainhttps:/www.cambridge.org/core/terms. https://doi.org/10.1017/S0031182000051660Downloaded from https:/www.cambridge.org/core. University of Basel Library, on 11 Jul 2017 at 09:50:05, subject to the Cambridge Core terms of use, available atParasitology, Vol. 84, Part 1 Plate 1C. MAILLARD, J. GONZALEZ AND D. NOISY (Facing p. 64)https:/www.cambridge.org/core/terms. https://doi.org/10.1017/S0031182000051660Downloaded from https:/www.cambridge.org/core. University of Basel Library, on 11 Jul 2017 at 09:50:05, subject to the Cambridge Core terms of use, available atParasitology, Vol. 84, Part 1 Plate 2C. MAILLARD, J. GONZALEZ AND D. NOISYhttps:/www.cambridge.org/core/terms. https://doi.org/10.1017/S0031182000051660Downloaded from https:/www.cambridge.org/core. University of Basel Library, on 11 Jul 2017 at 09:50:05, subject to the Cambridge Core terms of use, available at

A scanning electron microscope study of the male copulatory sclerite of the monogenean Diplectanum aequans

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