Dictymetra longiuncinata, Mariaux & Georgiev, 2018
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Dictymetra longiuncinata sp. nov.
Figs 23–28 View Figs 23–28
From Latin longus (long) and uncinus (hook) in reference to the large rostellar hooks of this species.
AUSTRALIA: about 44 specs, same data as for holotype ( AHC 36497 View Materials –36515).
Site of infection
About 45 specimens in a single host.
Body small, 10.1–13.9 mm (n = 2) long with maximum width 950–1400 (1144, n = 8) at level of early gravid proglottides. Most complete specimen consisting of 76–83 proglottides. Proglottides markedly craspedote, wider than long, progressively becoming longer, but mostly remaining wider than long except for a few terminal or exceptionally extended ones. Osmoregulatory canals only very partially visible. Scolex rounded, in continuity with strobila (without a marked neck); diameter 470–665 (551, n = 7) ( Fig. 23 View Figs 23–28 ). Proglottization starting precociously, often just behind suckers. Suckers rounded to slightly oval, muscular, unarmed, 230–300 (262, n = 32) in diameter. Rostellar apparatus mostly muscular, with a layer of glandular tissue at mid-length of rostellar sac. Rostellar sac well-delineated, with cylindrical anterior part and markedly tapering posterior part, extending well beyond level of posterior margin of suckers and sometimes into first proglottides, 475–690 × 150–210 (608 × 178, n = 7). Rostellum strongly muscular, with expanded anterior part bearing rostellar hooks, 400–620 × 110–145 (537 × 133, n = 8). Rostellar hooks ( Fig. 24 View Figs 23–28 ) in two regular rows, 20 (n = 6) in number, long and robust, curved overall; blade longer than handle. Anterior hooks 119–125 (121.5, n = 13) long, posterior hooks 124–135 (129.5, n = 15) long. Genital pores situated at border of anterior 40% of lateral proglottis margin, alternating irregularly in very short series, e.g., 1, 1, 1, 1, 1, 1, 2, 1, 2, 1, 1, 1, 1 or 1, 1, 2, 1, 1, 3, 1, 1, 1, 1; no more than 3 consecutive pores observed on one side. Genital ducts passing between osmoregulatory canals. Genital atrium as simple depression without particular structures. Genital papilla occasionally expressed in some proglottides.
Testes numerous, 18–28 (22, n = 19) in number, large, reaching 75–92 (84, n = 19) in diameter, situated in 2–3 layers, in one continuous and compact posterior field, extending in anterior direction to level of antiporal wing of ovary ( Fig. 25 View Figs 23–28 ). External vas deferens 13–18 in diameter, highly convoluted and particularly voluminous in antero-poral part of median field, sometimes slightly overlapping cirrussac, seminal receptacle or even testes. Cirrus-sac elongate, 137–180 × 33–45 (159 × 38, n = 44), delicate, slightly oblique, usually straight but with distal quarter sometimes bent anteriorly, crossing osmoregulatory canals, rarely not. Internal vas deferens forming several coils. Cirrus cylindrical, 7.5 in diameter, ornamented with tuft of thin hair-like bristles ( Figs 26–27 View Figs 23–28 ).
Vitellarium central, compact, irregularly shaped and slightly lobated. Ovary transversely elongated, bi-alate, lobate, antiporal wing larger than poral wing; the latter mostly covered by vas deferens. Mehlis’ gland not observed. Empty seminal receptacle round, becoming oval when filled, reaching up to 135 × 68, close to proximal extremity of cirrus sac. Vagina, large, opened posteriorly to male pore, mostly straight and transverse, parallel to cirrus-sac, thin-walled. No sphincters or other ornamentations.
Uterus starts its development in late mature proglottides as diffuse reticulum occupying the whole median field and part of lateral fields, and developing into dense network of tube and chambers. Eggs large, outer shell with polar extensions ( Fig. 28 View Figs 23–28 ). Complete eggs with external membrane difficult to see in utero but reaching at least 85 (without extensions). Embryophores oval, 53–65 (59.5, n = 15) in
diameter. Oncospheres 38–46 (42, n = 22) in diameter. Embryonic hooks: central 20–21.5 (21, n = 8) long, lateral 17–20 (19, n = 16) long.
This material is partly macerated, with many fragments contracted and overall in an average state of conservation. This explains the lack of data for several characters such as osmoregulatory canals or Mehlis’ gland. Our observations, nevertheless, allow for a description that fits the definition of Dictymetra , in particular because of its characteristic scolex structure and tuft of setae in the genital atrium and on the cirrus. The genus Dictymetra is typically found in various families of Charadriiformes , including Burhinidae ( Bona 1994) (see remarks above for D. gerganae sp. nov.) and is cosmopolitan ( Table 4 View Table 4 ). Our material can easily be differentiated from other species in the genus because of its very long hooks and large rostellum . Similar characters are only found in D. laevigata (Rudolphi, 1919) , another parasite of thick-knees, and D. paranumenii ( Clark, 1952) , a parasite of curlews in North America. It differs from both by its smaller number of testes. Additionally, it can be distinguished from the former species by its larger cirrus-sac, and from the latter by its shorter strobila ( Table 4 View Table 4 ).
In addition, the genus Stenovaria Spasskii & Borgarenko, 1973 also resembles our material. It differs from Dictymetra by relatively minor characters related to genital pore alternation, the position of genital ducts in relation to osmoregulatory canals and the absence of armament of long setae on the cirrus and (or) genital atrium. The genus was erected by Spasskii & Borgarenko (1973) and is presently recognized as valid ( Bona 1994, Mariaux et al. 2017). It includes 2 species found in thick-knees: Stenovaria facile ( Meggitt, 1927) Spasskaya & Spasskii, 1978 and S. falsificata ( Meggitt, 1927) Spasskii & Borgarenko, 1973 that deserve to be compared to our material. Both differ from it by their much shorter hooks and smaller strobila. In addition, the former species also shows a smaller cirrus-sac and the latter has a larger cirrus-sac and a smaller number of testes. In consequence we consider the present material as a new species that we name Dictymetra longiuncinata sp. nov.
|Species||Host family||Type locality||Body maximum length (mm)||Scolex diameter||Suckers diameter||Rostellar sac||Rostellum||Hooks number||Anterior hooks length||Posterior hooks length||Testes number||Cirrus sac|
|D. gerganae sp. nov.||Podargidae||Australia||72||305–360||145–175||230–292 × 118–145||195–212 × 98–132||24||46–53||50–56||60–77||100–132 × 65–83|
|D. longiuncinata sp. nov.||Burhinidae||Australia||13.2||470–665||230–300||475–690 × 150–210||400–620 × 110–145||20||119–125||124–135||18–28||137–180 × 33–45|
|D. radiaspinosa Mathevossian, 1953||Scolopacidae||USA||15–25||247–330||204–231||–||83–115||24||65–68||–||15–17||146–198 × 23–25|
|D. belopolskajae Spasskaya & Spasskii, 1973||Alaudidae||Russian Arctic||80||313||123||347–408 × 106–123||252–308 × 95–112||20||56–67||–||18–30||106 × 39|
|D. discoidea (Beneden, 1868)||Ciconiidae||Palaearctic||–||370–400||210||–||100||22–23||37–38||33–34||40–45||250–270 × 65–70|
|D. dispar ( Burt, 1940)||Charadriidae||Sri Lanka||40–50||330–385||143–175||325 × 110||175–229 × 65–88||24||41–45||44–49||18–28||170–200 × 38–41|
|D. ganii Spasskaya & Shumilo, 1971||Scolopacidae||Moldavia||70||695||335||246 × 140||162 × 67||22–24||28||–||(~40)||94 × 67|
|D. laevigata (Rudolphi, 1819)||Charadriiformes||Palaearctic||75||650||–||428||314 × 141||20||104–106||109–112||50||98 × 48|
|D. numenii (Owen, 1946)||Scolopacidae||Holarctic||14–20||192–538||133–221||–||124–162||22||99–103||–||42–46||111–140 × 44–58|
|D. nymphaea (Schrank, 1790)||Charadriiformes||Palaearctic||25–30||210–220||80–85||–||80–85||24||60–80||–||30–36||100–130 × 38–55|
|D. paranumenii (Clark, 1952)||Scolopacidae||USA||150–300||476–523||143–165||408–620 × 176–204||442–516 × 136–176||20||100–105||110–115||35–40||132–165 × 33–60|
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