Cestode parasites (Neodermata, Platyhelminthes) from Malaysian birds, with description of five new species

We studied the cestode fauna (Platyhelminthes) of forest birds in Malaysia (Selangor) collected during a field trip in 2010. Ninety birds of 37 species were examined and global prevalence of cestodes was 15.3%. Five new taxa are described: Emberizotaenia aeschlii sp. nov. (Dilepididae) from Tricholestes criniger (Blyth, 1845) (Pycnonotidae); Anonchotaenia kornyushini sp. nov. (Paruterinidae) from Trichastoma malaccense (Hartlaub, 1844) (Pellorneidae); Biuterina jensenae sp. nov. (Paruterinidae) from Chloropsis cochinchinensis (Gmelin, 1789) (Irenidae); Raillietina hymenolepidoides sp. nov. (Davaineidae) and R. mahnerti sp. nov. (Davaineidae) from Chalcophaps indica (Linnaeus, 1758) (Columbidae). Ophryocotyloides dasi Tandan & Singh, 1964 is reported from Psilopogon henricii (Temminck, 1831) (Ramphastidae). Several other taxa in Dilepididae, Davaineidae, Paruterinidae, Hymenolepididae and Mesocestoididae, either potentially new or poorly known, are also reported. The richness described from this small collection hints at the potentially huge unknown parasite diversity from wild hosts in this part of the world.


Introduction
Between 2008 and 2017, a worldwide concerted effort was made to document the diversity of cestodes in their vertebrate hosts (Caira & Jensen 2017). In this context, a team of taxonomists led by the present authors focused on avian parasites, with a particular focus on Cyclophyllidea of terrestrial birds . This resulted in various expeditions targeting particularly understudied hosts and regions (for previously published results, see Dimitrova et al. 2013Dimitrova et al. , 2017Dimitrova et al. , 2019Widmer et al. 4 Testes 26-34 (29, n = 14) in number; in 2 or 3 layers, in one continuous posterior field, sometimes overlapping osmoregulatory canals and often overlapping posterior lobes of ovary and vitellarium (Fig. 2). External vas deferens convoluted in antero-poral part of median field. Cirrus-sac elongate, 170-212 × 36-50 (191 × 43, n = 20), usually straight, crossing osmoregulatory canals; distal extremity with large cells (Fig. 3). Internal vas deferens forming several coils, mostly in proximal half of cirrus sac. Cirrus unarmed, about 100-130 long and usually straight when invaginated.  Vitellarium central, compact, transversely elongate, variable in shape but often forming a flattened V or reniform. Ovary antero-central, transversely elongate, bi-alate, multilobate, antiporal wing larger than poral wing; not overlapping longitudinal osmoregulatory canals. Mehlis' gland subglobular, anterior to vitellarium. Seminal receptacle round, becoming more oval when full but never elongated, reaching up to 190 × 145 in pregravid proglottides, dorsal and between ovary wings. Vagina opens posterior to male pore, straight and transverse, parallel to cirrus-sac; thick-walled, surrounded by a loose sheath of large cells irregularly positioned along entire canal; no vaginal sphincter (Fig. 3).
Uterus starts its development in late mature proglottides as a diffuse ventral reticulum, progressively forming numerous small lobes and occupying entire median field; crossing osmoregulatory canals and extending into lateral fields. Uterus eventually becoming sacciform with deep septa. Developing oncospheres round, 19-21 in diameter, no fully developed eggs or embryonic hooks observed.

Remarks
Dilepidids with a reduced, unarmed, apical apparatus belong to a number of genera. An important differentiating character for distinguishing among them is the presence (or not) of a rudimentary unarmed rostellum, or "bulb" (Bona 1994). This structure is a diagnostic character of two genera, Eburneotaenia Bona, 1994, with type species E. eburnea (Mariaux & Vaucher, 1988), characterised also by the presence of sucker armature consisting of small punctiform spines (see Mariaux & Vaucher 1988), and Emberizotaenia Spasskaya, 1970, which has unarmed suckers. Our specimen has such an unarmed bulb, albeit weak, and has unarmed suckers. Therefore, it belongs to Emberizotaenia, a genus known from birds of the order Passeriformes in the Palaearctic Region and in Australia. Bona (1994) mentioned Africa and Sri Lanka in the geographical range of this genus but without further explanation or reference; we consider the information about these geographical areas may come from his personal unpublished data.
The new species described here essentially fits the generic diagnosis proposed by Bona (1994). There is an exception related to the number of testes, which are "numerous" (26-34) in our material, instead of "very numerous" as mentioned in the generic diagnosis; according to Bona (1994), the adopted range for "very numerous testes" refers to "from about 36 to 60, seldom more". However, the type species E. reductorhyncha (Spasskaya, 1957), as well as E. skrjabiniana (Spasskaya, 1958), also have "numerous" testes (Table 1), i.e., between 14 and 35 according to Bona's (1994) definition. In addition, we could not observe the osmoregulatory canals forming a network posterior to the scolex in our specimens; this character may, however, be difficult to observe depending on the state of conservation and the fixation of the material, and has not been reported in the original descriptions of the majority of the known species. Therefore, we doubt that it is a reliable character to be used for generic differentiation.
Even in the absence of gravid proglottides, our specimen is unambiguously distinguishable from all of them (Table 1) Metrical characters in both taxa are very similar, but a number of differences nevertheless allow them to be distinguished morphologically. The most obvious ones are the shape of the rostellar pouch, which is globular in E. raymondi and more elongated in our material, as well as the presence of distinctive large cells making a loose sheath around a strongly walled vagina in the Malaysian material. Additionally, E. raymondi has as larger scolex and suckers; a more elongate cirrus sac, a higher proportion of it extending in median field; and a smaller seminal receptacle. From E. chlamyderae, a species with very poorly known anatomy, our specimen differs by its three times smaller body length, a larger cirrus-sac and, possibly, higher number of testes.
Together with the host and the geographical origin of our material, these observations allow its recognition as a new species, Emberizotaenia aeschlii sp. nov. Pycnonotidae represents a new host family for this genus of cestodes.

Remarks
This material presents all the characters of the genus Sobolevitaenia, a genus found in various passerines, including Motacillidae, that we recently discussed in detail (Mariaux & Georgiev 2018b). In that work, we presented a summary of the main metrical and meristic characters of the 17 known species of the genus. Most of them differ obviously from the present material because of their (mostly larger) hook length, number of testes or cirrus-sac length.
The most similar taxa are the type-species S. anthusi (Spasskaya, 1958) and its possible synonym S. orientalis Spasskii & Konovalov, 1969, which are found in various Motacillidae, rarely in other passerines, in the Palaearctic (Spasskaya & Spasskii 1977). Although some variation is known for this taxon, S. anthusi shows a rostellar armature and number of testes similar to the present material. It differs, however, essentially by having a shorter cirrus-sac (that also has a more limited extension across the proglottis), a longer rostellar sac, and a shorter rostellum. Its strobila is also shorter, not exceeding 15 mm (Spasskaya & Spasskii 1977). Sobolevitaenia orientalis has a different subset of differentiating characters, including a larger scolex, a shorter rostellar sac and slightly larger posterior hooks.
Finally, S. (?) borealis (Krabbe, 1869) also show characteristics similar to the present material. However, besides its very different hosts (Calcariidae) and distribution (Greenland), this poorly known taxon also has a larger scolex, only 18 rostellar hooks and shorter posterior hooks (according to Baer 1956).
The status of S. anthusi as a single species or a complex of similar species, and its possible synonymy with S. orientalis, remains unclear. Our material differs slightly from both original descriptions but would be included in the global variation of both taxa taken together. In addition, S. anthusi has been reported with significant morphological variation across its range that extends at least along the entire north coast of Russia and south to Tajikistan and Tuva. Those elements may be indicative of a complex of species, but for now we will take the cautious option of placing our material in S. anthusi sensu Spasskaya & Spasskii (1977). Figs 4-7. Sobolevitaenia anthusi (Spasskaya, 1958

Remarks
Our specimen is about 32 mm long, with a maximum width of 850. It consists of 64 proglottides which very rapidly become longer than wide. The anatomy is typical for a member of the Dilepididae: numerous testes (18-27) in one posterior field; irregularly alternating genital pores opening at anterior 20% of proglottis margin; unarmed cirrus; oval cirrus-sac reaching osmoregulatory canals; genital ducts passing between osmoregulatory canals; a large two-winged central ovary. Uterus is densely labyrinthine. Unfortunately, no scolex is available and a more precise identification is not possible. To our knowledge, no cestode had previously been reported from this host species or, indeed, from any of the 12 other species of tailorbirds.

Etymology
The species is dedicated to our colleague Prof. Vadim V. Kornyushin (Kiev, Ukraine), a dedicated cestode taxonomist with numerous contributions to the knowledge of the family Paruterinidae.

Remarks
This material belongs to the genus Anonchotaenia Cohn, 1900 as defined by Mariaux (1991) or Georgiev & Kornyushin (1994). The most recent review of its diversity was by Phillips et al. (2014), who presented a summary of the main characters of the known species. Subsequently, a single additional species, A. adhiraji Banerjee, Manna & Sanyal, 2018, was described in India (Banerjee et al. 2018). This allows the easy comparison of our material with the 30 known species of Anonchotaenia. Most of Anonchotaenia spp. clearly differ by more than one of the characters listed by Phillips et al. (2014) (scolex and sucker diameters, position of genital ducts, testis number, cirrus sac extent and size) and only 2 species are similar to our material, i.e., A. castellanii Fuhrmann & Baer, 1943, described from an Ethiopian laniid bird, and A. globata (von Linstow, 1879), initially described from a parid bird from Germany (von Linstow 1879). The former species exhibits close similarities with our material; however, its testis number (9-10) is only marginally overlapping our observations (6-9, with a dominant proportion of 7-8 testes). Anonchotaenia castellanii further differs from our material in showing a much more muscular cirrus-sac as well as a strong atrial sphincter (Fuhrmann & Baer 1943). Furthermore, Eurocephalus rueppellii Bonaparte, 1853, the host of A. castellanii, is endemic to Eastern Africa.
Anonchotaenia globata has been reported from a wide range of Passeriformes all over the world (Matevosyan 1969). It also resembles our material for most characters, even if a precise description of this species is difficult to infer from the multiple reports of this taxon. Kornyushin (1989) believed that the reports of A. globata should be referred to a complex of species. Philips et al. (2014) presented metrical data based on summarising known ranges reported for A. globata by many authors from various hosts and various geographical origins (but erroneously mentioning in their table that these data come from the original description only). Even considered in this wide and doubtful taxonomic context, A. globata is characterized by a smaller number of testes (4-5) than our material, though a larger range has occasionally been reported for this species. Although a few other unusual morphological characters (such as the changes of the shape of the paruterine organ during its development) seem promising for specific identifications in the group (Phillips et al. 2014), they still lack a complete comparative basis. Testis number presently remains crucial, and the most reliable criterion to identify Anonchotaenia spp. at the morphological level (Mariaux 1991). We consider it sufficient to justify the placement of our material in a new species that we name Anonchotaenia kornyushini sp. nov.

Etymology
The species is dedicated to our colleague Prof. Kirsten Jensen, University of Kansas, Lawrence, in recognition of her remarkable contribution to tapeworms systematics. Hologenophore MHNG-PLAT-121157. Partial COI sequence, Genbank MN590287.

Remarks
With its distinctive pair of uterine sacs, paruterine organ and typical rostellum, our material unambiguously belongs to the genus Biuterina Fuhrmann, 1902 as defined by Georgiev & Kornyushin (1994). The last review of the group by Georgiev & Mariaux (2007) reported 34 species in the genus and presented an identification key to the species. To our knowledge, no additional species has been reported since this publication. None of the species in this genus is known from Irenidae or Pycnonotidae, and only 3 of them have an Oriental distribution, all of them in India. No species of Biuterina spp. are known from SE Asia yet.
The majority of the known species differ markedly from our material by a combination of their rostellar hook numbers and length (which are mostly both more numerous and longer), resulting in only 2 species showing similar metric characters: We are well aware that, ideally, more material would be desirable to describe this species. However, given the unambiguous characters considered and the fact that access to these parasites is extremely scarce, we think it is worth taking the opportunity to describe and name it, even if additional information, especially concerning the variability of the metrical data, is to be provided when more specimens are available.
Specimens from T. criniger are juvenile and therefore not included in the type series. Their observable characters, especially the shape and organization of their rostellum and hooks, are, however, very similar to those of B. jensenae sp. nov. Unless access to fully developed specimens shows otherwise in the future, we consider them conspecific.

Remarks
The hook arrangement in two rows, as well as their triangular shape and epiphyses on both guard and handles, are reminiscent of the genus Biuterina. If confirmed, the combination of numerous (about 60 in number) and very small triangular hooks of same shape and size (about 14) in both rows, would be unique for this genus (Georgiev & Mariaux 2007

Remarks
This worm also shows characters of the genus Biuterina, although the lack of gravid proglottides does not allow a definitive identification. Scolex 325 in diameter. Suckers strong, 162-165 in diameter. Rostellum muscular, 120 in diameter, armed with double crown of 38 typical triangular hooks. Hooks about 15-16 long in both rows, those from first row slightly less massive. Genital pores irregularly alternating, opening slightly anteriorly to middle of lateral proglottis margin. Genital ducts passing between excretory canals. Testes in one continuous posterior field, 7-10 in number. Cirrus pouch elongate, regular, with strong walls, 74-84 × 28-34 (80 × 30, n = 7), not reaching or just reaching poral osmoregulatory canals. Vagina posterior to cirrus-sac. As for Biuterina sp. 1, the combination of number/length of rostellar hooks of this specimen seems to have not been observed in the presently known species of Biuterina (see Georgiev & Mariaux 2007). It is similar to B. jensenae sp. nov. and found in the same host family, but shows fewer rostellar hooks, slightly fewer testes and a shorter cirrussac. It is considered here a different taxon to be described when more abundant material is available.

Remarks
Columbiformes are second only to Galliformes as hosts for cestodes of the genus Raillietina. Over 60 species of these worms have been reported from pigeons and doves (Movsessian 2003a), three of them in Malaysia (Amin-Babjee & Lee 1992; Lee et al. 1998). In addition, R. palawanensis Deardorff, Schmidt & Kuntz, 1976 was described by Deardorff et al. (1976) in C. indica in the Philippines. To our knowledge, no other species have subsequently been described from these hosts.
Our material is quite unique in having an extremely reduced and constant number of testes per proglottis and can thus easily be differentiated from all these taxa. Although the number of testes is very variable among species of Raillietina, only a very few have fewer than 5, and none has 3 as observed in our specimens. Two species, R. palawanensis and R. quadritesticulata Moghe, 1925, are nevertheless relatively similar, though not identical, to our material for this character (3-4 and 4 testes, respectively, according to their descriptions). We reexamined part of the R. palawanensis type series, including its holotype, and although several original observations in Deardorff et al. (1976) are confirmed, we also observed several significant differences (Table 2): -the worms are much longer (length more than 60 mm, complete specimen probably more than 100 mm long) and wider (up to 790 at level of gravid proglottides); -the dorsal osmoregulatory canals are absent (likely mistaken for longitudinal muscle bundles in the original description); European Journal of Taxonomy 616: 1-35 (2020) 20 -testis number is essentially 4 (5 is not unusual, 3 and 6 are very rare); it should be noted that the initial development of testes is not synchronous, with one, sometimes two, antiporal testes showing a delayed growth; -the cirrus sac may be slightly larger than reported (up to 120 in length and 56 in width); -the copulatory vagina part is longer (39-52); -up to 17 egg capsules per proglottis, each containing up to 7 eggs can be observed in gravid proglottides; -oncospheres are 16-18 in diameter.
These observations confirm that R. palawanensis differs from our material by having a larger scolex and rostellum and fewer, much larger, rostellar hooks, as well as a larger cirrus-sac, while R. quadritesticulata has more rostellar hooks, a larger cirrus-sac and more egg-capsules per proglottis (Table 2). Our material is therefore clearly distinct and we place it in a new species, Raillietina hymenolepidoides sp. nov. Interestingly, all three species with an extreme reduction of testis number are found in South/South East Asia and two in the same host species. Although this clearly suggests a close relationship between these taxa, the significance of this observation in a phylogenetic context remains to be studied. A similar reduction in testis number is observed in the genus Diorchiraillietina Yamaguti, 1959, whose single species has only 2 testes per segment. It is found in various pangolin species in Africa and South Asia, including in species distributed in Malaysia, and may be indicative of a host-switching event. Molecular samples from pangolin parasites would allow the examination of this hypothesis.
The absence of dorsal excretory canals is an uncommon feature found in some davaineids. It is observed in the monotypic genera Porogynia Railliet &Henry, 1909 andBaerfainia Yamaguti, 1959. The latter, found in African Pholidota and erected for Raillietina anoplocephaloides Baer & Fain, 1955(Yamaguti 1959, shows a similar reduction of testis numbers (4, sometimes 3) as observed in our material. Its rudimentary rostellum and particular vagina structure are, however, very different. Hologenophore MHNG-PLAT-121346. Partial COI sequence, Genbank MN590291.

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.

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. 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.
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.
However, although the original description of Yamaguti & Mitunaga (1943) was correctly summarized by Artiukh (1966) and Movsessian (2003a), these authors failed to notice that in the original description the number of rostellar hooks was described as "… arranged in two alternating circles of 105-115 each". The total number of hooks in P. pycnonoti should thus be 210-230 in total, a figure different from what we observed in our material, which remains an unidentified species, either in Raillietina or Paroniella.
Egg developing in entire proglottis, including external to osmoregulatory canals. Uterus apparently saccular although barely visible, no egg capsules. Oncospheres small but no fully-developed eggs observed, as last proglottides in our specimen are filled with calcareous corpuscles.

Remarks
With numerous typical davaineid hooks in 2 rows, armed suckers, unilateral genital pores and an absence of egg capsules, our material belongs to the genus Ophryocotyloides Fuhrmann, 1920. According to Movsessian (2003b), 6 species of this genus parasitize Piciformes and 3 are found in the genus Psilopogon. All of them have been described from India and show very similar characters. Ophryocotyloides barbeti Singh, 1959 was described from the Brown-headed Barbet, P. zeylanicus (Gmelin, 1788) and O. haemacephala Singh, 1959 from the Coppersmith Barbet, P. haemacephalus (Muller, 1776). The former taxon can easily be differentiated from our material by its smaller number (150) of longer (22-27) hooks and higher number (10-15) of poral testes. The latter resembles our specimen but has a smaller rostellum (110-160); although the total numbers of testes are comparable, it has a larger poral number of testes according to Singh's (1959) drawing.
The third species, O. dasi Tandan & Singh, 1964 described from P. haemacephalus, is the most similar to our material on the basis of the description by Tandan & Singh (1964). It only differs in minor details like smaller suckers, which are reported to only bear 6-7 rows of hooklets. Ophryocotyloides dasi is also described with slightly fewer aporal testes (17-21), although the total number just overlaps our own observations. This is not sufficient to differentiate this species from our material with any certainty, as superimposed aporal testes are difficult to differentiate. Finally, Tandan & Singh (1964) reported a vaginal sphincter that is not present in our material (unless they refer to the cellular sheath we have observed). All other characters closely match our measurements. Without access to the type specimens of O. dasi, we consider that the minor differences noted above are not sufficient to distinguish our specimen from this species. In addition, it should be noted that the host of O. dasi and the Yellowcrowned Barbet (in which we found our material) have overlapping geographical ranges. This is the first report of this taxon since its original description. P. henricii is a new host for this species, and this is the first record of O. dasi in SE Asia.

Description
Worm with body of medium size, 7.5 mm long; maximum width 380 at level of last available pregravid proglottides. Strobila consisting of 73 proglottides. Proglottides craspedote, wider than long. Scolex poorly delineated from neck, 150 in diameter (Fig. 33 Vitellarium posterior to ovary, central, massive. Ovary antero-central, bi-winged with wings diverging posteriorly, compact but forming a few lobes in late development. Mehlis' gland anterior to vitellarium. Vagina opened posteriorly to male pore and parallel, postero-ventrally to cirrus pouch. Seminal receptacle central and dorsal, between ovary wings, anterior to vitellarium, up to 74 in largest diameter (Fig. 35).
Uterus starts its development in late mature proglottides as an antero-central sac, developing into a horseshoe-shaped saccular structure. Completely developed uterus and eggs not observed.

Remarks
Our material most closely matches the definition of Variolepis Spasskii & Spasskaya, 1954. This genus has been treated very differently by various authors. Notably it has recently been put in synonymy with Wardium Mayhew, 1925by Czaplinski (in Czaplinski & Vaucher 1994. This synonymy has, however, been widely considered as unjustified and Variolepis is now recognised as being valid Dimitrova et al. 2019).
The most widespread species of Variolepis is the type-species, V. farciminosa (Goeze, 1782), that has been found on several continents and in a wide diversity of passerine hosts. Most of these contributions report substantial variations in the observed characters (see, e.g., Illescas Gómez & Gómez García 1984), casting some doubts on their conspecificity and possibly being indicative of a complex of species. A common character of "V. farciminosa" s. lat. is nevertheless the presence of relatively long (20 or more) rostellar hooks, that unambiguously differentiate it from our material. Nine more species of the genus are known from Passeriformes worldwide (Schmidt 1986). We have summarized their available distinctive characters in Table 3. Most differ from our material by their larger rostellar hook size and only V. planestici (Mayhew, 1925) and V. bilharzii (Krabbe, 1869) are comparable for that crucial character.
Variolepis planestici was described from an American robin by Mayhew (1925), unfortunately without some crucial details such as rostellar or cirrus-sac measurements. Despite its similar hooks, this species seem to differ from our material by having its testes clearly disposed in a triangle.
The original description of V. bilharzii is incomplete; however, Krabbe's drawings show hooks with massive guards that are much longer than the blades (Krabbe 1869: figs 228-229.). A later description by Joyeux & Baer (in Joyeux et al. 1928) from a West African drongo is the most complete to date but remains partial. The species was subsequently only found again by Johri (1935) in a crow from Myanmar. Interestingly, in his figure 4, Johri illustrates hooks of the same shape as shown by Krabbe. It is difficult to separate our material from V. bilharzii, although our specimen has a smaller scolex and suckers and a somewhat larger cirrus-sac. Furthermore V. bilharzii is described with testes in a triangular arrangement, but testes are mostly in a row in our material (although some variation is possible, see Fig. 35).
Globally, the characters available to differentiate our material and the two species discussed above are extremely limited and basically insufficient. Previously used arguments (e.g., Mayhew (1925) claimed a slight difference in hook shape for erecting V. planestici) need to be critically evaluated with more material. As a consequence, it is very difficult to separate our material from both above-mentioned taxa, or indeed to separate them from each other. For now, we attribute our specimen to V. bilharzii, given its species range and diversity of hosts, which include East Asia and Muscicapidae. Due to priority, it is also the name that would apply to all these specimens in case they are eventually considered conspecific. A more definite conclusion would require additional specimens to assess their morphological variation and, Table 3. Variolepis Spasskii & Spasskaya, 1954 of Passeriformes. Data from original descriptions except: * from Spasskaya (1966), ** from Skrjabin & Matevosyan (1945), *** from Joyeux et al. (1928).

Remarks
The presence, possibly massive, of tetrathyridia is known from many avian species, including Passeriformes over almost all the world (Literák et al. 2004;Mariaux et al. 2017;Heneberg et al. 2019). This is a new host and locality for the genus.

Discussion
The helminth parasitofauna of Malaysian birds, and especially its cestode component, has been very little studied. Surveys are few (e.g., Kuntz (1969) examined over 100 species of birds, but from Malaysian Borneo only) and recent isolated reports mostly deal with the parasitofauna of domestic animals or focusing on other types of parasites, especially ectoparasites, haematozoa or viruses. A few isolated contributions by S. Amin Babjee and C. Lee are an exception, as these authors examined various wild birds belonging to the Corvidae (Amin-Babjee et al. 1987), Phasianidae (Amin-Babjee et al. 1985) and Columbidae (Amin-Babjee & Lee 1992; Lee et al. 1998). As far as cestodes are concerned, the specific diversity reported in these papers remains, however, extremely limited. In addition, Singh et al. (1987) conducted a survey of vertebrates from the Ulu Endau area (South of Malay Peninsula) but found no (!) endoparasites in 17 species of birds. Some more comprehensive reports focused on 'neighbouring' Myanmar or Sri Lanka birds (e.g., Meggitt 1927Meggitt , 1931Johri 1935Johri , 1951Burt 1940) but are mostly outdated now in terms of degree of detail compared to the recent standards in cestode taxonomy and remain patchy. It is thus no overstatement to consider that the parasitofauna of the over 800 species of birds known from Malaysia is basically unexplored. More generally, Southeast Asia remains one of the large areas in the world where the cestodes of wild animals are particularly poorly known.
Despite the fact that the small size of our sample prevents a detailed analysis of its faunal structure, we observe that all major bird cestode families are represented, most by several taxa. The apparent high diversity of Paruterinidae is especially interesting and further data for this group would allow for useful comparisons with its better known African fauna.
In this contribution we identified 13 taxa, 5 of them new. There is little doubt that most of the others would also represent new species, provided a sufficient number of specimens is available. In fact, we postulate that a systematic study of wild birds would allow the description of dozens of new taxa with limited efforts, even if restricted to a few specimens from common bird species.
Given the particular vulnerability of these hosts (Soh et al. 2006) and a more general rapid disappearance of tropical habitats in Southeast Asia (see, e.g., Sodhi et al. 2010), large scale surveys focusing on the parasitofauna of non-model vertebrate hosts, an essential component of global biodiversity, should urgently be undertaken.