Raillietina mahnerti, Mariaux & Georgiev, 2020

Mariaux, Jean & Georgiev, Boyko B., 2020, Cestode parasites (Neodermata, Platyhelminthes) from Malaysian birds, with description of five new species, European Journal of Taxonomy 616, pp. 1-35 : 21-24

Raillietina mahnerti sp. nov.

urn:lsid:zoobank.org:act:0705D781-68CD-4B0B-BF6B-0E8DAF4A24EF

Figs 27–30

Etymology

The species is dedicated to Prof. Volker Mahnert, former director of the Museum of Natural History of Geneva and eminent naturalist ( Schwendinger 2019), who passed away during the preparation of this paper.

Material examined

Holotype

MALAYSIA • Selangor, University of Malaya’s Gombak Field Station ; 3.32° N, 101.77° E; 280–350 m a.s.l.; 5 Aug. 2010; MHNG-PLAT-121344.

Paratypes

MALAYSIA • 4 specs; same collection data as for holotype; MHNG-PLAT- 121347 .

Hologenophore

MHNG-PLAT- 121346. Partial COI sequence, Genbank MN 590291 .

Type host

Chalcophaps indica (Linnaeus, 1758) ( Columbiformes , Columbidae ).

Prevalence

25% (1/4).

Description

Thin and very long worm with body consisting of more than 850 proglottides, reaching ca 200 mm in length (estimated from fragments) and 950 in maximum width at level of pregravid proglottides. Proglottides weakly craspedote, wider than long, except for the very last gravid ones. Scolex not clearly delineated from neck, 185 in diameter. Suckers round, 46–50 (49, n = 4) in diameter; muscular, armed with 6 dense rows of hooklets 3–6 long; crown of hooklets progressively reduced in posterior direction, then interrupted ( Fig. 27b ). Rostellum discoid, 100 in diameter, 60 long, weakly muscular, armed with double crown of about 270 hooks ( Fig. 27a ). Rostellar hooks of typical davaineid shape, delicate, 9 long ( Fig. 27c ). Pseudoproboscis covered with minute, spine-like microtriches. Neck segmentation distinct at 1.3 mm from posterior margin of suckers. Genital primordia appearing at about 200 th proglottis. Genital pores unilateral, situated at 35% of lateral proglottis margin. Ventral osmoregulatory canals up to 58 wide, connected posteriorly in each proglottis by wide transverse (occasionally bifurcated) anastomosis. Dorsal osmoregulatory canals 1–2 wide; not distinct in many proglottides. Genital ducts passing between osmoregulatory canals (or dorsal to ventral canals when dorsal canal not distinct). Genital atrium small, infundibular, inconspicuous.

Testes 8–14 in number (11, n = 75), in single layer; in two fields, each with variable number of testes: poral group of 1–6 testes and larger antiporal group of 5–10 testes (average 4 and 7, respectively, n = 75), one detached testis sometimes positioned posteriorly; testes round, in single layer ( Fig. 28 ). External vas deferens highly convoluted, extended transversely almost up to middle of proglottis. Cirrus-sac elongate, oval, with well-marked walls, 90–115 × 44–58 (102 × 49, n = 45), not reaching osmoregulatory canals. Internal vas deferens short, making single loop before reaching rounded expansion resembling internal seminal vesicle, 19–26 (22, n = 20) in diameter. Cirrus armed with dense long setae, connected to sac by distinct retractor muscles ( Fig. 29 ).

Vitellarium posterior, central, compact and globular, 50–75 (62, n = 26). Ovary antero-central, compact fan-shaped, composed of a few large lobes. Mehlis’ gland just anterior to vitellarium. Seminal receptacle tubular, more distinct in pregravid proglottides. Vagina opened posteriorly to male pore, composed of a copulatory part 40–48 × 8–15 (44 × 11, n =12), surrounded by a well-defined and thick wall, terminally surrounded by discrete but wide muscular sphincter, followed by short and narrow proximal (conductive) part and wider elongate seminal receptacle extending transversely, then posteriorly toward mid-proglottis ( Figs 28–29 ).

Eggs developing in well-defined parenchymatous capsules. Capsules 19–31 (26, n = 34) in number per proglottis, 80–120 (95, n = 20) in diameter, each containing 4–10 (6, n = 85) eggs ( Fig. 30 ). Eggs 26–35 (31, n = 20) in diameter, oncospheres 14–19 (16, n = 24) in diameter, embryonic hooks 6–8 (7, n = 10) long.

Remarks

With its typical rostellar apparatus and hammer-shaped hooks, armed suckers, unilateral genital pores and multiple egg capsules, this material can confidently be placed in the genus Raillietina . As stated above, over 60 species of this genus are known from Columbiformes worldwide ( Movsessian 2003a). In order to check whether our material belongs to any of them, we initially compared the number and size of rostellar hooks as well as the number of testes with our observations, allowing the differentiation of most of these species from the present material. The few remaining species listed below are more similar to our material and are compared in more detail.

Railletina flaminiata ( Meggitt, 1931) (usually erroneously reported as R. flaminata ) was described from Columba punicea Blyth, 1842 and Goura coronata (= G. cristata (Pallas, 1764)) in Myanmar ( Meggitt 1931). The former host is also present in Malaysia. The species description is incomplete, in particular as the number of rostellar hooks is lacking, but most available characters are similar to our observations. However, the number of testes (5–9) is somewhat smaller and the number of egg capsules (16) and eggs per capsule (2–6 but mostly 2) are distinctive.

Raillietina kunisakiensis Sawada & Kugi, 1979 is known from Treron sieboldii sieboldii (Temminck, 1835) in Japan, a host that is absent from the Malaysian Peninsula. Its description makes it very similar to our material, but it has longer (14) rostellar hooks, a slightly different disposition and number of testes and a vagina that is not split into distinct copulatory and conductive parts ( Sawada & Kugi 1979).

Raillietina fuhrmanni idiogenoides (Baer, 1933) is known from various African Columbidae . According to Mahon (1958), it has slightly fewer (230) rostellar hooks than in our material and a longer (145–164) cirrus sac.

Raillietina joyeuxbaeri (Nguyen Thi Ky & Dubinina, 1980) is a parasite of Streptopelia tranquebarica (Hermann, 1804) in Vietnam (the host has been introduced to Malaysia), showing close similarity to our material. However, it is a smaller species with slightly larger (11–13) rostellar hooks and fewer testes (6–7).

Finally, we also consider Raillietina polychalix (Kotlan, 1921) here. Although this species is parasitic in Psittaciformes, it was also reported in Columba livia by Movsessian (2003a) (however, no source is cited). This species is very similar to our material for most characters, including a close (240–250) number of rostellar hooks, which are, however, somewhat longer (13). It also has a slightly longer cirrus-sac (120) and wider scolex (320).

Even though morphological identification of Raillietina is notoriously difficult, we consider that the differences listed above, together with its new host and locality, are sufficient to conclude that our material differs from all know species of Raillietina and to place it in a new species, R. mahnerti sp. nov.

Figures

Figs 27–30. Raillietina mahnerti sp. nov. 27. a) Scolex. b) Sucker hooklets. c) Rostellar hook. 28. Mature proglottis, ventral view. 29. Copulatory organs. 30. Gravid proglottis with egg capsules. Scale bars: 27a, 28, 30 = 100 µm; 27b = 20 µm; 27c = 10 µm; 29 = 50 µm.