Dictymetra longiuncinata, Mariaux & Georgiev, 2018

Mariaux, Jean & Georgiev, Boyko B., 2018, Seven new species of cestode parasites (Neodermata, Platyhelminthes) from Australian birds, European Journal of Taxonomy 440, pp. 1-42 : 22-27

Dictymetra longiuncinata sp. nov.

urn:lsid:zoobank.org:act:71A5F386-689C-4416-A46C-8FC5078441E4

Figs 23–28

Etymology

From Latin longus (long) and uncinus (hook) in reference to the large rostellar hooks of this species.

Material examined

Holotype

AUSTRALIA: Queensland, Yeppoon , 23°8′ S, 150°44′ E, 30 Sep. 1999, Ian Beveridge leg. (AHC 36496).

Paratypes

AUSTRALIA: about 44 specs, same data as for holotype (AHC 36497–36515).

Host

Esacus magnirostris (Vieillot, 1818) (syn. Burhinus magnirostris ) ( Charadriiformes , Burhinidae ).

Site of infection

Small intestine.

Intensity

About 45 specimens in a single host.

Description

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 ). 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 ) 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 ). 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 ).

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 ). 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.

Remarks

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 ). 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 ).

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.

Figures

Figs 23–28. Dictymetra longiuncinata sp. nov. 23. Scolex. 24. Hooks. 25. Mature proglottis. 26. Terminal genitalia. 27. Cirrus armament. 28. Eggs. Scale bars: 23 = 100 µm; 24, 26 = 50 µm; 25 = 200 µm; 27 = 10 µm; 28 = 20 µm.

Tables

Table 4 (continued on next page). Comparison of two new Dictymetra Clark, 1952 species with the presently recognized species in the genus and with “long” Liga Weinland, 1857 species (see text). All data as reported in Spasskaya & Spasskii (1978) for Dictymetra and Spasskaya & Spasskii (1977) for Liga except Burt (1940) for D. dispar, Clark (1952) for D. paranumenii, Fuhrmann & Baer (1943) for D. riccii and Spasskaya & Spasskii (1973) for D. volvulus. Note that values reported by various authors for D. laevigata (Rudolphi, 1919) and D. volvulus (Linstow, 1903) vary to a large extent (Spasskaya & Spasskii 1978). Dictymetra paranumenii and D. radiaspinosa have rows of small spines on rostellum.

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