TRICLADIDA Lang, 1884

Jones, Hugh D. & Fenwick Sr, David, 2018, Specimens of a New Zealand terrestrial planarian, Artioposthia exulans (Dendy, 1901) (Platyhelminthes: Geoplanidae) from Cornwall, UK, Journal of Natural History 52 (41 - 42), pp. 2653-2663 : 2655-2660

Order TRICLADIDA Lang, 1884

Suborder CONTINENTICOLA Carranza, Littlewood, Clough, Ruiz-Trillo, Baguña and Riutort, 1998 Family GEOPLANIDAE Stimpson, 1857 Subfamily RHYNCHODEMINAE Graff, 1896 Tribe Caenoplanini Ogren and Kawakatsu, 1991

Genus Artioposthia Graff, 1896

Artioposthia exulans ( Dendy, 1901)

Geoplana exulans Dendy, 1901

Geoplana exulans Dendy, 1904

Artioposthia exulans Fyfe 1946

Artioposthia exulans Ogren & Kawakatsu 1991

Material examined

NHMUK 2013.9.5.3-4. Newlyn , Cornwall, UK [50.101237°N, 5.543878°W], 13 and 15 May 2013, col . D . Fenwick . The mature Newlyn specimen was cut into four portions: the anterior end, about 2.5 mm long, longitudinal serial sections on three slides; a 1.5 mm portion, transverse sections on three slides; a portion about 7 mm long, though partly twisted, including the pharyngeal opening and gonopore, longitudinal serial sections on 12 slides; the posterior 1 mm, retained for future DNA analysis .

Description

Dimensions of this and other specimens are shown in Table 1. The pharyngeal aperture (mouth) is positioned 29–57% along the ventral surface from the anterior end and the gonopore 39–72%.

The two ovaries are about 6 mm from the anterior end (39% of body length), about 0.5 mm anterior to the base of the pharynx. Each ovary discharges into an ovovitelline duct ( Figure 2a,b ), each of which runs posteriorly just dorsal to the paired ventral nerve cord on either side. Behind the gonopore they join ventrally to form a common female

(pharyngeal aperture) and gonopore from the anterior end. Dimensions in mm. Vial 5a etc. and Vial

6 refer to preserved intact specimens of Chatham Island specimens (NMHUK, 1924.8.15.86-93) in

different vials. Mouth % and gonopore % refer to their position as a proportion of body length.

duct ( Figure 3c,d ) which expands and is surrounded by glandular cells, assumed to secrete the shell of the egg cocoon before opening into the common atrium.

Numerous ventral testes ( Figure 2a,b ) are present from anterior to the ovaries to behind the copulatory apparatus. Anterior to the copulatory apparatus, each sperm duct broadens into a seminal vesicle densely filled with sperm ( Figure 3b ). These ducts narrow, join and discharge through a small conical projection ( Figure 3a ). There are two adenodactyls, one dorsal and one ventral to the opening of the ejaculatory duct into the male atrium ( Figure 3a,b ). Each is roughly spherical, about 200 µm in diameter.

The cylindrical pharynx is strongly contracted lengthwise, about 1.25 mm long and 0.75 mm in diameter ( Figure 4a ). The pharyngeal opening is positioned about 70% along the pharyngeal pouch from the base of the pharynx.

The sub-epidermal musculature consists of a very thin layer of circular muscles 3–4 µm thick and longitudinal muscles in bundles about 35 µm thick ( Figure 5 ). There is no annular zone of parenchymal longitudinal muscle.

Dark pigment, assumed to be melanic, is present in regions of the sub-epidermal muscle bundles and parenchyma ( Figures 2 , 3 , 5 ) but unevenly distributed round the circumference. There is a broad mid-dorsal pigmented region, several more narrow areas dorso-laterally and two ventrally ( Figure 5 ). These are presumed to coincide with the dark stripes visible in the living animal.

The creeping sole occupies about 90% of the ventral surface.

The remaining preserved specimen of NHMUK 2013.9.5.3-4 still shows clear dark striations dorsally and ventrally 5 years after preservation in 99% ethanol.

NHMUK 1924.8.15.86-93. Labelled as Geoplana exulans . Specimens in 80% alcohol, several specimens in six vials, all collected by A . Dendy from Chatham Island, New Zealand [43.92°S, 176.49°W], January 1901 and January 1911 . Sixteen slides prepared from Dendy’ s material by Fyfe (1946), in three series: Series 1 (S1), six slides (1–6), longitudinal sections of entire worm, green stain, mature but some sections were damaged in preparation and it is not possible to interpret the copulatory apparatus; Series 2 (S2), four slides (but numbered 1, 2, 5 and 7) labelled ‘TYPE’, longitudinal sections of the posterior including copulatory apparatus, but not the pharynx, Borax carmine; Series 3 (S3), six slides (but numbered 2–7), longitudinal section of an entire worm, mature, Borax carmine, 25 µm.

However, Fyfe (1946) states: ‘The lectotype consists of eight slides deposited in the British Museum (Natural History)’. Presumably this is S2, even though it consists of only four slides, since slides are labelled ‘TYPE’. The NHMUK register records a total of 16 slides deposited in 1946, so none have gone missing since then.

Description

In S3 the paired ovaries lie halfway between the mouth and the anterior end, about 1.9 mm anterior to the base of the pharynx. Each ovary discharges ( Figure 2c ) into an ovovitelline duct which runs posteriorly. In S2 and S3 the ovovitelline ducts join ventrally posterior to the gonopore to form the common female duct surrounded by glandular cells.

Testes ( Figure 2c ) are present anterior to the ovaries and posterior to the copulatory apparatus. The sperm ducts each expand to form a seminal vesicle ( Figure 6 ), then narrow and join to discharge through a short projection ( Figure 6b ). There are two adenodactyls, one dorsal and one ventral to the opening of the ejaculatory duct into the male atrium ( Figure 6 ), each about 250 µm in diameter.

In S1, the cylindrical pharynx is elongated, about 2.62 mm long and 0.42 mm in diameter ( Figure 4b ). The pharyngeal aperture is about 35% of the length of the pharyngeal cavity. In S3 the pharynx is cylindrical but strongly contracted lengthwise, 1.1 mm long and 0.86 mm in diameter ( Figure 4c ). The pharyngeal aperture is about 61% along the pharyngeal cavity.

None of the remaining spirit-preserved specimens from Chatham Island (NHMUK 1924.8.15.86-93) show any sign of dark longitudinal stripes either dorsally or ventrally.

They are currently preserved in 80% industrial methylated spirit, but may previously have been stored in formalin.

Figures

Figure 2. Artioposthia exulans, Newlyn specimen NHMUK 2013.9.5.3-4: a, longitudinal section through the ovary; b, longitudinal section through the ovovitelline duct; c, type material, NHMUK 1924.8.15.86- 93, Series 3, longitudinal section through the ovary. Anterior to the right. Scale bars: 100 µm.

Figure 3. Artioposthia exulans, Newlyn specimen NHMUK 2013.9.5.3-4, copulatory apparatus: a, section through the male parts showing the adenodactyls and male opening; b, section though the shell gland, the female opening to the antrum and the expanded sperm duct; c, section through the common female duct; d, diagrammatic reconstruction. Anterior to the right. Scale bars: 200 µm.

Figure 4. Artioposthia exulans pharynx: a, Newlyn specimen NHMUK 2013.9.5.3-4, anterior to the right; b–c, Chatham Island, New Zealand specimens, NHMUK 1924.8.15.86-93, anterior to the left; b, Series 1; c, Series 3. Arrowheads indicate the position of the pharyngeal aperture. Scale bars: 500 µm.

Figure 5. Artioposthia exulans, Newlyn specimen NHMUK 2013.9.5.3-4: transverse section of prepharyngeal and pre-ovarian region; a and c, enlargement of dorsal and ventral regions of (b) as indicated by dashed lines; b, whole section. Note several regions of sub-epidermal melanic pigment round the circumference. Scale bars: a, c = 50 µm; b = 200 µm.

Figure 6. Artioposthia exulans, Chatham Island, New Zealand specimens, NHMUK 1924.8.15.86-93, copulatory apparatus:a–b, ‘TYPE’ specimen, Series 2; c, Series 3. Anterior to the right.Scale bars:200 µm.