Australophiotaenia mjobergi ( Nybelin, 1917 ) Chambrier & Beveridge & Scholz, 2018

Chambrier, Alain De, Beveridge, Ian & Scholz, Tomáš, 2018, Tapeworms (Cestoda: Proteocephalidae) of Australian reptiles: hidden diversity of strictly host-specific parasites, Zootaxa 4461 (4), pp. 477-498 : 483-488

Australophiotaenia mjobergi ( Nybelin, 1917) n. comb.

( Figs. 11–17 )

Syns Crepidobothrium mjobergi Nybelin, 1917 ; Proteocephalus mjobergi ( Nybelin, 1917) Hughes, Baker & Dawson, 1941 ; Ophiotaenia mjobergi ( Nybelin, 1917) Wardle & McLeod, 1952

Type and only known host: Yellow-faced whip-snake, Demansia psammophis (Schlegel, 1837) ( Ophidia : Elapidae ).

Site of infection: Intestine.

Type locality. ‘ Police Camp’ , located within the Conservation Park, near Walsh Creek, Western Australia (17°13'59.0''S, 125°35'47.0''E).

Distribution. Western Australia.

Reference. Nybelin (1917).

Material studied. Syntypes (3 whole mounted slides—SMNH 102304 – 102306; 3 slides with sections— SMNH 102307 – 102309; 2 whole mounts and 8 slides with cross sections made in Geneva from syntype material in ethanol—SMNH 3272).

Redescription. Based on type material. Cestodes up to 150 mm long; maximum width 2.4 mm. Strobila acraspedote, anapolytic. Immature proglottids wider than long to longer than wide (length: width ratio 0.42–0.50, n = 6), mature, pregravid and gravid proglottids longer than wide (length: width ratio 0.43–1.83, n = 17).

Internal longitudinal musculature well-developed, composed by a thick layer of numerous bundles of muscle fibres ( Figs. 14–16 ). Ventral osmoregulatory canals 20–25 in diameter, situated between vitelline follicles and testes ( Fig. 15 ). Dorsal osmoregulatory canals 10–12 in diameter, overlapping dorsally most lateral.

Scolex 430–470 long and 750–880 wide, slightly wider than neck, 795–815 wide. Suckers uniloculate, round, slightly embedded, somewhat cordate, 325–430 wide, representing about 41–48% of scolex width ( Fig. 11 ). Apical organ absent, but scolex apex with numerous gland cells ( Fig. 11 ).

Testes medullary, in one or two layers, forming two large lateral bands (poral band separated by terminal genitalia into preporal and postporal groups). Testes reach anterior margin of proglottid and some anterolateral testes may slightly overlap vitelline follicles ( Fig. 12 ). Testes 245–257 (x = 251, n = 2) in number, with 124–133 aporal testes, 76–82 preporal testes and 42–45 postporal testes. Testes oval to elongate, 30–70 wide to 85–135 long, present also in gravid proglottids.

Cirrus-sac ovoid, thin-walled, 435–615 long and 220–290 wide; length: width ratio 1.62–2.31; length of cirrussac represents 24–31 % (x = 28%, n = 11) of proglottid width. Cirrus thick-walled, its length representing about 80% of cirrus-sac length. Sperm duct strongly coiled. Vas deferens strongly coiled, occupying a small area between proximal part of cirrus-sac and midline of proglottids, but never crossing it. Genital atrium shallow; genital pores alternating irregularly, slightly pre-equatorial to equatorial, at 45–51% of proglottid length from anterior margin. Ovary medullary, bilobed, 435–695 wide; width of ovary represents 56–61% (x = 60%, n = 11) of proglottid width; relative size of ovary (see de Chambrier et al. 2012) 4.7%. Mehlis’ gland 150–175 in diameter, representing 8–9% of proglottid width. Vagina forming small seminal receptacle posterior to ovarian isthmus; vaginal canal slightly sinuous just anterior to seminal receptacle. Terminal (distal) part of vaginal canal (pars copulatrix vaginae) surrounded by elongate vaginal sphincter and chromophilic cells ( Fig. 13 ). Vagina usually posterior (92%, n = 36) to cirrus-sac.

Vitelline follicles medullary, on dorsal side only, paramuscular, arranged in two lateral fields near margins of proglottids, occupying porally 89–96% and aporally 91–97% of proglottids length, interrupted at level of cirrus-sac and vagina.

Primordium of uterine stem paramuscular, present in immature proglottids. Development of uterus of type 1 according to de Chambrier et al. (2004, 2015): in immature proglottids, uterine stem straight, occupying most of length of proglottid but never crossing ovarian isthmus, formed by wide longitudinal band of chromophilic cells situated along midline of proglottids. In pregravid proglottids, uterus occupying up to 40% of proglottid width, with 33–34 thin-walled lateral diverticula on each side; apex of lateral diverticula lined with thin layer of chromophilic cells. In gravid proglottids, diverticula occupying up to 65% of proglottid width. Uterine duct entering uterus almost at level of ovary isthmus.

Eggs in clusters of 6– 9 eggs ( Fig. 17 ). Outer envelope hyaline, up to 150 in diameter; embryophore threelayered, diameter of individual layers 30–34, 22–25 and 17–19, respectively; oncosphere 12–14 in diameter, with six embryonic hooks 7–8 long. Immature egg clusters entering uterus 45–55 in diameter, increasing in size within the uterus up to 100 in diameter.

Remarks. The species was described by Nybelin (1917), who reported the eggs to be individual in the uterus or in clusters (“Die Eier liegen einzeln oder in unregelmässigen Klümpchen zusammengeklebt.”), but only eggs in clusters were observed in the type material. We presume that Nybelin observed immature clusters and thought they represented isolated eggs. In some proteocephalids, eggs entering the uterus increase in size within the uterus, reaching up to four times the diameter of immature eggs (see Sandonella sandoni [Lynsdale, 1960] or Proteocephalus hobergi de Chambrier and Vaucher, 1999 —de Chambrier and Vaucher, 1999 and de Chambrier et al., 2008).

Abbreviations: OV = percentage of the width of the ovary versus the width of the proglottid; PC = percentage of the length of the cirrus-sac to the width of the proglottid; PP = position of the genital pore (cirrus pore) as the % of the proglottid length; SL = Supplementary layer of the eggs

The syntypes are of reasonably good quality, which enabled us to redescribe this species, which is probably specific to yellow-faced whip-snake and has never been found since its original description. This rare cestode differs from congeneric species found in reptiles from Australia by the following features: a high concentration of glandular cells within the apex of the scolex, numerous testes (200–300), a small ratio of the width of the ovary to the proglottid width (53–64%), and the number of eggs in each clusters (6– 9 eggs; see Table 1).

Molecular data are not available for this cestode species.

Figures

FIGURES 11–17. Australophiotaenia mjobergi (Nybelin, 1917) n. comb., syntype from Police Camp, Northern Territory, Australia [Coll. No. SMNH 3272]. 11. Scolex. 12. Pregravid proglottid, ventral. 13. Terminal genitalia. 14–16. Cross sections at level of ovary, testes and uterus, respectively. 17. Eggs in capsules.