Microplana terrestris ( Müller 1774 )

Jones, Hugh D., Webster, Bonnie L., Littlewood, D. Timothy J. & Mcdonald, Jillian C., 2008, Molecular and morphological evidence for two new species of terrestrial planarians of the genus Microplana (Platyhelminthes; Turbellaria; Tricladida; Terricola) from Europe, Zootaxa 1945 (1), pp. 1-38 : 16-19

Microplana terrestris ( Müller 1774)

Müller’s (1774) original description ( Fig. 10 ) is minimal and none of his specimens remain. Müller did not specify any location or even country for the three specimens he examined, though he was Danish and worked in Denmark. Minelli (1977) designated a specimen from Denmark as neotype for the species but gave no figure or description of this specimen. Probably the best descriptions and diagrams of the copulatory apparatus of this species are by von Kennel (1882) and Bendl (1908; 1909), though there are differences apparent in the two Bendl diagrams.

Microplana terrestris (Müller) , neotype (see Minelli, 1977), NHMD, TUR-17.1-8 (8 slides LS anterior including pharynx); TUR-19.1-12 (12 slides LS posterior including copulatory apparatus). Labels read: “ Microplana terrestris (O.F. Müll.) ; det. Minelli 1976; Kildeskoven; I Ellestub; 6.X.1918; Hj. Ditlevsen ”. Google Earth shows two places with the name Kildeskoven, one near Fredericia ( Jutland ), the other near Kalundborg (Zealand). Figure 11 shows a series of sections through the copulatory apparatus of this specimen. Each sperm duct expands to form a sperm storage organ immediately before entering the muscular bulb of the penis. The sperm ducts discharge separately into the base of the penis. The penis consists of two distinct parts, a basal bulb which does not project into the antrum, and a tapering, muscular, penis papilla which projects into the antrum. The basal bulb has an external diameter about 0.4 mm and there are several broad internal projections into its cavity. This cavity is equivalent to the “seminal vesicle” of many authors, though it is uncertain to what extent it is glandular. The projecting penis papilla has a basal diameter of about 0.2 mm and is about 0.5 mm long. A narrow ejaculatory duct, diameter about 25 µm, runs from the bulb to the distal end of the penis through the muscular part. The vagina opens directly off the antrum, is narrow and about 0.3 mm long. The paired ovo-vitelline ducts open separately but close together into its posterior extremity ventrolaterally. Also opening at its posterior extremity, but from the dorsal side is the genito-intestinal connection. This opens into a broad, sinus-like, cavity which, in this specimen, has a single narrow connection antero-dorsally to an intestinal diverticulum .

Rhynchodemus terrestris NHMW, 2831 M257. This collection consists of 151 slides of 20 specimens, some immature, from various European localities. The material originates from L von Graff and his collaborators at the University of Graz and some slides can be recognized as the source of illustrations in Graff (1899) and Bendl (1908, 1909). Some labels are apparently in Bendl’s handwriting. Figure 12a shows a section of a specimen from County Galway, Ireland. There is a spherical basal bulb with internal projections, and a short, conical penis papilla projecting into the antrum. The vagina is short and, as above, the two oviducts and broad genito-intestinal canal open into its posterior end. Transverse sections of another specimen (no locality on label) show the broad genito-intestinal canal and its opening into the intestinal diverticulum ( Fig. 12b & c ).

Rhynchodemus carli Fuhrmann 1914 . NHMG (transferred from the University of Neuchâtel). 5 slides. Minelli (1977) considered this to be a synonym of Microplana terrestris , but as Minelli comments, “the type specimen is of very little help in assessing the true nature of the species”. The specimen was 10.5 mm long (preserved) and uniform brown/yellow in colour. Sections of the copulatory apparatus are poor, incomplete and not clear enough for a definitive identification. The ovaries are only partially mature and no ovo-vitelline duct is visible in transverse sections. However, numerous testes are visible. Expanded sperm ducts with stored sperm are visible posteriorly, but the specimen was damaged and nothing of the penis or other parts of the copulatory apparatus is present. The colour of the specimen suggests that this may not have been a specimen of M. terrestris , but we cannot be certain of its identity.

Microplana terrestris MNHNP, AO 38-49. Labelled “Madé C 1-3 ”. This specimen is one of those reported by Beachamp (1957) from Madeira. The penis is as described above ( Fig. 13a ) thus its identification is confirmed.

The copulatory apparatus of two specimens of M. terrestris from Shirdley Hill , Lancashire (HDJ collection) are shown in Fig. 13 , b & c .

Microplana terrestris T1, T2, T4, T7 (see above). The copulatory apparatus of T1, T2 and T4 all have a basal penial bulb with internal projections, and a short muscular penis papilla ( Figs. 14 & 15 ). The vagina opens directly from the antrum and the genito-intestinal canal is broad and sinus-like. There are two openings from the genito-intestinal canal into the intestine in T1 and T2 but only one in T4. Refractive granules in the digestive epithelium do not enter the genito-intestinal canal ( Figs 14c , 15b, 15d ). We are confident that our identification of these specimens as M. terrestris is accurate.

Discussion of Microplana terrestris . The size, grey or black colour and broad white ventral creeping sole are quite good discriminating factors for live specimens of this species. However the colour may be non-uniform as in the granular specimens. The copulatory apparatus is distinctive, the penis having a spherical basal ejaculatory duct (seminal vesicle) with internal projections, and a distal, muscular penis papilla projecting into the antrum. The genito-intestinal duct opens via a broad, sinus-like chamber into a branch of the intestine via one or two openings. Both Graff (1899) and Bendl (1908; 1909) show that there may be more than one such connection. Minelli’s (1977) figure, which is after Bendl (1908), is generally accurate with the exception that the entry of the sperm ducts (labelled "deferens") into the penis is misleading. The figure in Ball & Reynoldson (1981) is generally accurate with the exception that the cavity in the basal bulb of the penis (labelled “seminal vesicle“) is shown with a smooth lining without any of the internal projections visible in all the above specimens.

Figures

FIGURE 10. Microplana terrestris (Müller 1774). Müller’s description of 1774 (as Fasciola terrestris). This is the first published description of any terrestrial planarian.

FIGURE 11. Microplana terrestris (Müller 1774). Neotype (designated by Minelli, 1977). NHMD, TUR-19.1-12. a–f. Series of sections of the copulatory apparatus at different planes through the serial sections. Each is a merged image of two adjacent images. Anterior to the left.

FIGURE 12. Microplana terrestris (Müller 1774). Specimens from NHMW, originating from the University of Graz. a. Longitudinal section through the copulatory apparatus of a specimen from County Galway, Ireland. b & c. Transverse sections through a specimen of unknown origin.

FIGURE 13. Microplana terrestris (Müller 1774). Copulatory apparatus of specimens from: a. Madeira collected and identified by Beauchamp (1957) MNHNP, AO 38-40; b & c. Two specimens from Shirdley Hill, Lancashire collected 1992 by HDJ. Anterior to the left in a & b, to the right in c. All to same scale.

FIGURE 14. Microplana terrestris (Müller 1774). Specimen T1, NHML, 2006.6.28.1. Sections through the copulatory apparatus. b & c are of the same section, c is viewed with polarised light showing the refractive granules (white) limited to the intestinal epithelium. Anterior to the left.

FIGURE 15. Microplana terrestris (Müller 1774). a & b. Specimen T2, NHML, 2006.6.28.2. c & d. Specimen T4, NHML, 2006.6.28.4. Sections through the copulatory apparatus, b & d viewed with polarised light showing the refractive granules (white) limited to the intestinal epithelium.