Amaga expatria, Jones & Sterrer, 2005

Jones, Hugh D. & Sterrer, Wolfgang, 2005, Terrestrial planarians (Platyhelminthes, with three new species) and nemertines of Bermuda, Zootaxa 1001 (1), pp. 31-58 : 32-38

Amaga expatria n. sp. ( Figs 1–8 , Color Plate 1–2)

Material examined: Holotype. Divided into five parts. Anterior half, pharyngeal region and posterior end are preserved in alcohol. A small portion anterior to the pharyngeal region sectioned transversely (4 slides, remainder in wax). The portion containing the copulatory apparatus serially sectioned longitudinally (28 slides, remainder in wax). Deposited in the Natural History Museum, London, accession number: 2002.10.16.1.

Paratype. Preserved specimen found in unaccessioned collections of the BAMZ, with the label: “ I.W. Hughes, Collector; Smith’s Parish, Bermuda. 22.1.63, Bermuda Dept. Agr. PL 2 #, col in house, seen frequently”. Deposited in the Bermuda Natural History Museum, BAMZ 2004.221.012 .

Type locality: Bermuda Botanical Gardens, Paget, Bermuda.

Etymology: From ex patria = expatriate, meaning away from one’s native country, recognising that this worm, like much of the present biota of Bermuda including humans, originated elsewhere.

Description: The holotype was found by David Wallace in February 1988 in the Bermuda Botanical Gardens, outdoors, during daylight, crawling over a rockery. The specimen was passed to WS at the BAMZ, photographed alive and preserved in 80% alcohol (BAMZ 1989.066.001). It was subsequently sent to HDJ for identification. External dimensions were measured. A portion anterior to the pharynx was removed for transverse sections and the portion containing the copulatory apparatus was removed for longitudinal sectioning ( Fig. 1 ).

The extended living worm (Color Plate 1) was approximately 90 mm long and 8 mm wide and flattened. The dorsal ground colour was mid­brown with a dark brown anterior tip. Two narrow dark blue lines are present dorsally along the anterior third. These fade towards their posterior extremity, though some photographs show these to be just visible almost to the posterior end. The ground color between these two lines is about half the width of the animal so that the lines are about one quarter of the width in from the margin. As these two lines begin to fade (at about one fifth of the length from the anterior end), an irregular series of blue/black marks occurs on either side a little medial to the two lines. The marks are not continuations of the lines ( Fig. 1 ) and continue posteriorly to about the level of the pharynx where they stop abruptly. They may indicate the positions of the dorsal testes.

The preserved holotype was about 80 mm long and 7 mm wide and about 1.5 mm thick at the level of the pharynx, its widest point. The body tapers gently from the pharyngeal region towards the pointed anterior end and the less sharply pointed posterior end. Eyes are absent from the very anterior tip, about 1 mm. On either side of the head the eyes are about three or four deep in a very narrow marginal zone and very close together, almost touching to form a dark line laterally ( Fig. 2 ). There are about 50 mm­1 of body length on either side. Posteriorly the eyes are very small and visible only after clearing. The zone of eyes expands dorsally ( Fig. 3 ) so that by about a quarter of the way along the body, only the mid quarter or so lacks eyes. The eyes become further apart than at the anterior end and the band of eyes is 20 to 30 eyes wide on either side (80–100 mm­1 of body length). This zone continues almost to the posterior end, the eyes becoming more sparse ( Fig. 4 ) and virtually absent in the posterior mm or so. At the level of the pharynx there are about 10 eyes mm­1 on either side.

The pharyngeal aperture and gonopore are respectively about 45 mm (56% of body length) and 57 mm (71%) from the anterior end. After clearing, the pharyngeal pouch is about 10 mm long and the pharynx appears to be of the plicate or “kragenförmig” (collarform) type (see Graff 1899; Winsor et al. 1998). The copulatory apparatus appeared to be about 12 mm long. The creeping sole covers the entire ventral surface which is flattened or even concave.

Figure abbreviations: ca = common antrum; cod = common oviduct; cs = creeping sole; csd = common sperm duct; do = dorsal origin of pharynx; ed = ejaculatory duct; fod = fused ovo­vitelline duct; g = gut; gp = gonopore; jod = junction of the ovo­vitelline ducts; jsd = junction of the sperm ducts; ls = pigment of lateral stripe; m = mouth (pharyngeal aperture); ml = midline; ms = pigment of median stripe; od = ovo­vitelline duct; p = penis; ph = pharynx; sd = sperm duct; t = testes; ted = thickened portion of the ejaculatory duct; v = vagina; vnc = ventral nerve cord; vo = ventral origin of pharynx.

Dimensions of the preserved paratype specimen (Color Plate 2) are: length 100 mm; largest width 8 mm; pharyngeal aperture 55 mm (55%) and gonopore (with partly everted penis) 70 mm (70%) behind the anterior end.

Transverse sections ( Fig. 5 ) are about 6 mm wide and 1.5 mm high. Dorsal epithelium is 25–30 µm thick and columnar, nuclei are basal. Dorsal sub­cutaneous musculature is 60–70 µm thick, consisting of an outer layer of circular fibres 10–20 µm thick, a layer of helical muscle 10–20 µm thick and an inner longitudinal layer, not in bundles, about 30 µm thick. Ventral epithelium is 20–25 µm thick and columnar, nuclei are basal. The ventral surface is densely ciliated across the full width. The cilia are about 5 µm long. Ventral sub­cutaneous musculature is 40–50 µm thick with an outer layer of circular muscle only one or two fibres deep, helical fibres and inner longitudinal muscle not in bundles. Thus the cutaneous muscular index (CMI, the proportion of cutaneous muscle thickness to body thickness, see Froehlich, 1955; Winsor 1983, 1998) is about 7% (this in a very flattened species). Dorso­ventral muscle fibres run vertically between the gut diverticula. The ventral nerve plate is slightly expanded either side of the midline into ventral nerve cords ( Fig. 5 ). The paired ovo­vitelline ducts lie immediately dorsal and lateral to the nerve plate ( Fig. 5 ). It is presumed that the ovaries are a single pair anteriorly, as in most terrestrial planarians. Confirmation would require sectioning of the anterior portion. Vitelline glands appear to be restricted to the ventral region, there are none dorsal to the gut diverticula. Testes are dorsal. The paired sperm ducts lie closely dorsal to the ovo­vitelline ducts.

Longitudinal sections of the copulatory apparatus ( Figs 6–8 ) show that the paired sperm ducts fuse ventrally at the anterior of the penis bulb to form a single wide combined sperm duct which passes dorsally to enter a broad chamber of uncertain function near the dorsal surface (no sperm are evident, yet it is full of eosinophilic material). A narrow ejaculatory duct leaves this chamber and leads to the penis. The proximal part of the ejaculatory duct is convoluted. It then becomes more or less straight, but the centre part has a thickened wall. The thickening extends horizontally through many sections (estimated width across the specimen, 710 µm) and appears to form what appears to be a horizontal chamber. The distal end of the penis is highly convoluted and ill­defined. The musculature of the penis is relatively loose and not clearly organized into layers of circular or longitudinal muscle. The paired ovo­vitelline ducts run posterior to the gonopore and then turn gently dorsally to join near the dorsal surface. They form a narrow single duct which runs anteriorly, curving ventrally then dorsally and widens into the horizontal, wide and long vagina (this could be considered a posterior extension of the female antrum). The vagina is a little convoluted towards the common antrum. The vagina enters the common antrum horizontally but near the dorsal surface.

Discussion: Fourteen genera are included in the Geoplaninae by Ogren & Kawakatsu (1990) and two further genera were proposed by Carbayo & Leal­Zanchet (2003). The genus Pseudogeoplana Ogren & Kawakatsu 1990 is a collective genus for species with insufficient details of internal anatomy (either immature specimens or described only on external characteristics) to place in a defined genus. These specimens do not match the description of any of the species listed in Pseudogeoplana . The remaining genera are defined largely, but not exclusively, on the basis of the anatomy of the copulatory apparatus. Before sectioning we had considered that the specimen might be a species of Gigantea Ogren & Kawakatsu 1990 . However, our specimen lacks the penis papilla characteristic of that genus and some others. It also has eyes (one genus lacks eyes) and has no sucker­like organ ventrally on the anterior. This restricts the candidate genera to Amaga , Notogynaphallia and Pasipha , all originally defined by Ogren & Kawakatsu (1990). Definitions are as follows. Amaga : “ Geoplaninae of elongate, large, broad and flattened body; male copulatory organ with intra­antral papilla surrounding the opening of the ejaculatory duct; female canal enters the genital antrum dorsally; ovovitelline ducts approach from the antero­dorsal aspect”. Notogynaphallia : “medium­sized, slender body; penis papilla absent; male antrum with folded walls; female canal enters dorsally”. Pasipha : “elongate body; penis papilla absent; with folds in male antrum; female canal approaches from ventral side”. Since the Bermuda specimens are distinctly large and broad, and if the thickening of the ejaculatory duct is interpreted as an “intra­antral papilla”, then the specimen is an Amaga . However, in A. expatria the thickening of the ejaculatory duct appears to form an extensive flattened chamber and does not have the appearance of a conical papilla. No other species has a similar structure. Examination of original descriptions and illustrations of some Amaga species ( Fuhrmann 1914; Hyman 1955) leads us to conclude that it is a debatable point whether some of these have an “intra­antral” papilla. However, if the thickening is considered not to be a papilla, then the specimen is either Notogynaphallia or Pasipha , yet neither of these has species which are particularly large and broad. The approach of the oviducts to the common female duct is also antero­dorsal. All this leads to the somewhat tentative placement of the Bermuda specimens in the genus Amaga . The Bermuda species does not match any of the 11 Amaga species listed by Ogren & Kawakatsu (1990) and is thus described as a new species.

The dorsal black spots may indicate the position of the testes, which are dorsal and quite close to the dorsal epithelium. E.M. Froehlich (pers. comm.) has noted similar pigmentation in some other geoplanids, Geoplana (Geoplana) ladislavii von Graff 1899 and G. (G.) chiuna E.M. Froehlich 1955 . The following species also shows dark pigmentation over the dorsal testes.

The eyes of the Bermuda specimens have a distinctive distribution. They do not spread round the anterior tip and are restricted anteriorly to a narrow lateral, dense band, 2–3 eyes wide, but then spread widely dorsally further back. A similar eye distribution is shown by Amaga contamensis ( Hyman 1955) from Peru, though in other species of Amaga the row of eyes is continuous round the anterior end.

Nothing is known of the feeding or other aspects of the biology of A. expatria . However, the plicate type of pharynx, as in A. expatria , is present in many other species of terrestrial planarian such as Bipalium kewense Moseley 1878 and Arthurdendyus triangulatus (Dendy 1894) . Both of these feed almost exclusively on earthworms and it is likely that earthworms are the sole or principal prey of A. expatria . Presumably reproduction is by copulation and subsequent production of an egg capsule, as in all other terrestrial triclads, though there may be some asexual reproduction by fission.

Since all Geoplaninae are from South or Central America ( Ogren et al. 1997), it is safe to assume that A. expatria originated in that region. While the single specimen found in 1988 could have been attributed to a recent chance introduction, the discovery of a specimen collected in 1963 and the note on the label (“seen frequently”) raises the question of a cryptic Bermudian population. The locality is given as Smith’s Parish but without a precise location. The collector of this specimen has been contacted but does not recall any further details. Some localities in Smith’s Parish were visited in 2003 in ignorance of the 1963 specimen, but a more detailed search of the parish might produce further specimens.

Figures

FIGURES 1–5. Amaga expatria n. sp. Holotype. 1. Whole worm, preserved. The two dotted oval outlines indicate the positions of the pharynx and copulatory apparatus. Regions removed for transverse (ts) and longitudinal (ls) sectioning are indicated by dashed lines. Length approximately 80 mm. 2–4. Eye distribution traced from cleared specimen. Scale lines 1 mm. 2. Lateral view of left side of anterior end. 3. Dorsal view of right side about a quarter of the way from the anterior end. 4. Dorsal view of right side adjacent to the pharynx. Dashed line in 3 & 4 represents the mid­line. 5. Transverse section anterior to the pharynx. Scale line 1 mm.

FIGURES 6–8. Amaga expatria n. sp. Holotype. 6. Diagram of the copulatory apparatus reconstructed from longitudinal sections (cf. Fig. 7). Anterior is to the left. Scale line 1 mm. 7. Montage of micrographs of longitudinal sections through the copulatory apparatus (cf. Fig. 6). Anterior is to the left. Scale line 1 mm. 8. Section, lateral to that of Fig. 7, through the posterior part of vagina showing the relationship of the ovo­vitelline ducts and vagina. Same scale.