Neopolystoma orbiculare (Stunkard, 1916)

Domènech, Francesc, Marquina, Rafael, Soler, Lydia, Valls, Luis, Aznar, Francisco Javier, Fernández, Mercedes, Navarro, Pilar & Lluch, Javier, 2015, Helminth fauna of the invasive American red-eared slider Trachemys scripta in eastern Spain: potential implications for the conservation of native terrapins, Journal of Natural History 50, pp. 467-481 : 471-474

Identification of Neopolystoma orbiculare

Body oval-shaped and elongated [length: 2.93 ± 1.10 mm (2.16–4.32 mm); maximum width: 1.05 ± 0.31 mm (0.65–1.44 mm)]. Oral sucker diameter 433 ± 111 (330–570). Pharynx 192 ± 51 (120–220) long and 237 ± 62 (140–260) wide. Oesophagus not seen due to overlap with vitelline follicles. Intestine branches not convergent posteriorly. Genital pore ventral [diameter: 7.5 ± 2.6 (5–11)], posterior to intestinal bifurcation, with 16 genital spines [length: 3 ± 0.4 (0.3–3.8)]. Oval testis, in medial zone of the body 229 ± 108 (130–380) long and 206 ± 64 (120–270) wide. Vaginal pores ventral, posterior to ovary [separated by 1.07 ± 0.2 mm (1.01–1.33 mm)]. Vitelline follicles extending from posterior part of pharynx to haptor. One individual bearing one pear-shaped egg ( Figure 2D ), 183 long and 108 wide. Haptor slightly circular, 0.84 ± 0.27 mm (0.56–1.13 mm) long and 1.00 ± 0.40 mm (0.67–1.61 mm) wide. Six suckers distributed radially and equidistant from each other, 303 ± 96 (190–410) in diameter. Sixteen larval hooks 17 ± 2 (14–20) long and 9 ± 1 (7–10) wide situated as follows: six between the two anterior suckers, four between posterior suckers and one in each sucker.

Remarks

Species of Neopolystoma ( Price, 1939) are distinguished from those of allied genera, i.e. Polystomoides ( Ward, 1917) and Polystomoidella ( Price, 1939) , by the lack of hamuli ( Morrison 2010). Other diagnostic traits are the presence of one testis, short uterus and ovary in the anterior part of the body. Also, ovarian follicles extend into the posterior part of the body and vaginas are present.

The genus Neopolystoma currently contains 21 species that are distributed worldwide except in the Afro-tropical region, and usually occur in the urinary bladder, cloaca and, occasionally, nasal mucosa and conjunctival sac of freshwater turtles ( Price 1939). Neopolystoma orbiculare was described in T. scripta and Chrysemys picta ( Schneider, 1783) in North America ( Morrison 2010). Diagnostic traits of N. orbiculare found in the present study agree with the measurements and other features provided for the holotype established by Stunkard (1916) and with re-descriptions by Price (1939) and Lamothe-Argumedo (1972). The species can be separated from the four other sympatric species of Neopolystoma from the Nearctic region as follows ( Stunkard 1916; Caballero 1938). Neopolystoma domitilae ( Caballero, 1938) infects the urinary bladder and cloaca of Trachemys ornata ( Gray, 1831) and has 19–21 genital spines and a larger body size (4.04–4.06 by 1.32–1.72 mm). Neopolystoma elizabethae ( Platt, 2000) infects the conjunctival sac of the eye of Chrysemys picta bellii ( Gray, 1831) and has eight genital spines. Neopolystoma terrapenis ( Harwood, 1932) infects the urinary bladder and cloaca of Terrapene carolina ( Linnaeus, 1758) ; Price (1939) considered that this species was very similar to N. orbiculare , but Harwood (1932) stated that N. terrapenis has a smaller body size than N. orbiculare (1.90–2.50 by 0.72–0.82 mm), the vitellaria do not crowd into the intercaecal area posterior to the testis, and the pharynx and cirrus sac are also smaller. Neopolystoma chelodinae ( MacCallum, 1918) infects the urinary bladder and cloaca of Chelodina longicollis ( Shaw, 1794) ; this species is very similar to N. orbiculare but differs from all other species of Neopolystoma in that it has a testis with irregular margin, and vitelline follicles with irregular shape and variable size ( Price 1939; Pichelin 1995) and more variability in the number of genital spines (12–16; Morrison 2010).

In the Palaearctic region, three species of Neopolystoma have been described. Neopolystoma exhamatum ( Ozaki, 1935) is found in the urinary bladder and cloaca of Mauremys japonica from Japan, but it was recently reported from T. scripta in the same region ( Oi et al. 2012). This species resembles N. orbiculare regarding haptor shape, but its testis has different morphology and size (1.20–1.60 by 0.70–1.30); N. exhamatum also has more genital spines (16–18; Morrison 2010). Neopolystoma palpebrae Strelkov, 1950 , which occurs on the lower eyelid of Pelodiscus sinensis ( Wiegmann, 1834) , is very similar to N. orbiculare but differs in the shape and size of genital spines ( Morrison 2010). Finally, Neopolystoma euzeti Combes and Katari, 1976 infects the urinary bladder and cloaca of the Spanish pond turtle, Mauremys leprosa in North Africa ( Combes and Katari 1976). However, compared with the specimens examined in the present study, N. euzeti has more hooks in the genitalia (33–36) with a larger size (length: 48–57 µm); body (4.54 ± 0.75 × 1.51 ± 0.08) and haptor (1.20 ± 0.17 × 1.67 ± 0.32) are also larger, and vitelline follicles are more widely extended.

Based on the above evidence, we conclude that our material is conspecific with

N. orbiculare .

Figures

Figure 2. Parasites found in the American red-eared slider, Trachemys scripta in eastern Spain. (A) Telorchis solivagus; (B) Serpinema microcephalus (anterior part detail); (C) Neopolystoma orbiculare (immature); (D) Neopolystoma orbiculare (adult). Scale bars: A, B, D, 1 mm; C, 0.5 mm.