Citrilolepis citrili Dimitrova & Georgiev & Mariaux & Vasileva 2019, n. g., n. sp.

Citrilolepis citrili n. g., n. sp. Type-host: Crithagra citrinelloides (Passeriformes: Fringillidae), African citril. Type-locality: Wondo Genet (7.08°N, 38.63°E), Ethiopia. Type-material: Three fragmented specimens (coll. 22.xi.2012): 3 anterior fragments consisting of scolex and strobila ending with premature proglottides, and c. 30 fragments of strobila at various stages of maturation (10 slides). The material consisted of highly fragmented specimens and the designation of a complete representative individual as a holotype was not applicable. Syntypes: MHNG-PLAT- 121396 (7 slides), one scolex in Berlese’s medium and fragments of strobila, stained and mounted in Canada balsam; IBER-BAS-C 0159.1.4–1.5 (2 slides), one immature specimen and fragments of strobila, stained wholemounts; hologenophore (syntype): MHNG-PLAT- 121395, stained whole-mount. Site in host: Small intestine. Prevalence and intensity: In 1 out of 3 birds studied; 3 individuals. Representative DNA sequence: cox 1 mtDNA, one sequence (GenBank: MK463853). Etymology: The species name is derived from the common name of the type-host species. Description (Figs. 3–6) [Based on 3 fragmented specimens.] Body slender, ribbon-shaped, medium-sized, gradually widening posteriorly; maximum width at pregravid proglottides, 1510–1630 (1560, n = 5). Scolex oval, apically protruded; 111–158 (142, n = 3) long, with diameter 153–212 (177, n = 3) at level of posterior end of suckers (Fig. 3A). Scolex, neck and premature proglottides densely covered with large microtriches (Fig. 6), becoming smaller with further maturation of strobila. Suckers round, muscular, with diameter 67–94 (79, n = 12). Rhynchus with short, conical apical protrusion anterior to crown of rostellar hooks when rostellum invaginated (Figs. 3A, 6A). Rostellum retractile, ovoid, thick-walled, with length 58–74 (65, n = 3) and maximum width at apical part 42–49 (46, n = 3), slightly tapering posteriorly; intensely stained glandular cells presented in its cavity. Rostellar sheath oval, thick-walled, not reaching level of posterior margins of suckers, 89–95 (92, n = 3) long, with maximum width 57–62 (59, n = 3) at its middle; intensely-stained glandular masses presented in its cavity (Fig. 3A). Rostellar hooks diorchoid, 18 (18, n = 3) in number, arranged in single row; each hook with long, slender handle with slightly curved end, sickleshaped blade, much shorter than handle, and welldeveloped guard (Figs. 3B, 6A). Measurements of hooks: total length 11–13 (12, n = 7); length of blade 3 (3, n = 7); length of base 8–9 (8, n = 7); distance between tip of blade and tip of handle 3–4 (3, n = 7). Neck slim, long, 99–126 (112, n = 3) wide, covered with distinct microtriches (Fig. 6B). Proglottisation beginning at 1.84–2.47 mm (2.16, n = 2) from posterior margins of suckers. Proglottides craspedote, much wider than long at all stages of development. Dorsal osmoregulatory canals narrow, with diameter 2–12 (5, n = 20). Ventral osmoregulatory canals 10–47 (30, n = 22) wide, with irregular transverse anastomoses with diameter 2–20 (8, n = 18); usually anastomoses situated along posterior proglottis margin, sometimes along transverse median line of proglottis (Fig. 3 D), passing ventral to testes, seminal receptacle and Mehlis’ gland, and dorsal to ovary, vitellarium and uterus (Fig. 3C, D, F). Sometimes, in neighbouring proglottides, 2 transverse anastomoses of ventral canals may join together forming short common duct near antiporal ventral osmoregulatory canal (Fig. 3C, D). Inner longitudinal muscle bundles of strobila numerous. Genital pores unilateral, sinistral, opening in anterior third of lateral proglottis margin. Genital atrium simple, thick-walled, surrounded by intensely stained cells, 27–54 (40, n = 13) deep; width diameter at base 10–32 (21, n = 14) and diameter at orifice 10–30 (17, n = 13) (Fig. 5B, C). Genital ducts dorsal to poral osmoregulatory canals. Strobila protrandrous, with gradual maturation. Testes oval or with irregular shape, typically 3 (n = 131) in number per proglottis, rarely 4 (n = 16) and occasionally 5 (n = 1) per proglottis; testes with length 94–161 (123, n = 19) and width 62–94 (78, n = 19) in ‘‘male’’ mature proglottides (Fig. 3E). Position of testes may vary: usually 1 poral and 2 antiporal (n = 115) to female glands (Figs. 3C, F) or 2 poral and 1 antiporal (n = 14); rarely, all 3 testes arranged together antiporally (n = 2) to female glands (Fig. 3D, E); sometimes, in proglottides with more than 3 testes, they divided into 2 poral and 2 antiporal (n = 9), 1 poral and 3 antiporal (n = 6) or 3 poral and 1 antiporal (n = 1). Testes degenerating in postmature proglottides before appearance of young uterus (Fig. 4A). External seminal vesicle along anterior margin of proglottis, dorsal to seminal receptacle, testes, ovary and vitellarium, tubular in young male proglottides (Fig. 3E), becoming voluminous, sac-like when filled of sperm, with maximum length 198–238 (221, n = 4) and width 50–89 (68, n = 4); connected to cirrus-sac by coiled canal with diameter 30–37 (34, n = 10). Cirrus-sac thin-walled, elongate, slightly narrowing at middle and with rounded antiporal end; passing along anterior proglottis margin, crossing osmoregulatory canals dorsally, never reaching midline of proglottis; maximum length 235–259 (244, n = 14) and width 45–82 (54, n = 14) in mature proglottides (Figs. 3, 5B). Internal seminal vesicle oval or drop-shaped, 111–143 (131, n = 8) long and 37–57 (48, n = 8) wide, filling entire antiporal 1/3 to 1/2 of cirrus-sac (Fig. 5B). Ejaculatory duct 6–8 (6, n = 11) in diameter, coiled in cirrus-sac with invaginated cirrus; intensely-stained glandular cells surrounding internal walls of cirrus-sac and bottom of internal seminal vesicle. Evaginated cirrus cylindrical, 104–124 (110, n = 5) long; consisting of 3 distinct parts; basal part short, unarmed, 12–15 (15, n = 5) long, 22–25 (23, n = 5) wide; middle part 30– 37 X 22–25 (33 X 23, n = 5), densely covered with 19–23 (21, n = 10) rows of small triangular spines with maximum length 2–3 (3, n = 10); apical part unarmed, cylindrical, slightly tapering distally, with measurements 57– 87 X 12–20 (64 X 15, n = 5) (Fig. 5D). Ovary median, ventral to testes and genital ducts, usually adjacent to anterior proglottis margin; almost fan-shaped, consisting of 5–8 (6, n = 17) compact oval lobes (Fig. 3 E); fully-developed ovary 248–312 (281, n = 12) wide (Fig. 4 A). Vitellarium with irregular shape, consisting of several compact oval lobes, median, posterior to ovary, 106–119 (112, n = 9) wide (Figs. 3 E, 4 A). Mehlis & gland almost compact, situated between vitellarium and ovary, dorsally to them (Figs. 3F, 4A). Seminal receptacle tubular when empty, becoming voluminous when filled of sperm, dorsal to female gonads and ventral to testes, cirrussac and external seminal vesicle (Figs. 3E, 4A); connecting with conductive part of vagina by tubular, thin-walled, coiled part, gradually enlarging and passing into voluminous sac-like part, 198–257 X 89 –109 (216 X 93, n = 7) (Figs. 4A, B). Vagina opening and passing ventral or postero-ventral to cirrus-sac; copulatory and conductive parts distinct (Fig. 5C). Copulatory part of vagina with cup-shaped poral portion, with length 35–46 (37, n = 6) and diameter at vaginal orifice 26–35 (28, n = 6), tapering and passing into narrow, tubular antiporal part 48–60 (52, n = 6) long and 16–19 (17, n = 6) wide; vaginal lumen covered by long, hair-like microtriches; genital atrium and copulatory vagina surrounded by thick sleeve of intensely-stained glandular cells (Fig. 5C). Conductive part of vagina thin, 5–8 (7, n = 8) wide, its lumen without microtriches, gradually passing into seminal receptacle at level of poral osmoregulatory canals (Fig. 5C). Young uterus first appearing in fully-developed ‘‘female’’ mature proglottides as transversely-elongate, convoluted, thick-walled tube with slightlydeveloped labyrinthine structure and often with diverticula of poral end, situated in median field, dorsal to female gonads and ventral to cirrus-sac and genital ducts (Fig. 4 A). Developing uterus transversely-elongate, thick-walled, with labyrinthine structure, forming deep diverticula and numerous sacculations (Figs. 4B, C). Gravid uterus thickwalled, sac-like, occupying entire median field, expanding above anterior margin of proglottis, never crossing lateral osmoregulatory canals (Fig. 5 A). Ripe eggs oval; external shell thin, with diameter 40–55 (47, n = 9); embryophore thick, elliptical, 26– 32 X 18–25 (29 X 21, n = 13); oncospheres 20– 28 X 13–19 (23 X 17, n = 13); 3 pairs of embryonic hooks differing in length; median pair 12–13 (13, n = 10) long, internal lateral pair 10–11 (11, n = 11) long and external lateral pair with length 10–11 (10, n = 11) (Fig. 5E). Remarks According to the revision of the family Hymenolepididae by Czaplinski & Vaucher (1994), the avian hymenolepidid genera are divided into four subfamilies, i.e. Fimbriariinae Wolffhügel, 1899, Echinorhynchotaeniinae Mola, 1929, Hymenolepidinae Perrier, 1897 and Diploposthinae Poche, 1926. The presence of two pairs of osmoregulatory canals, with the genital ducts passing dorsally to them, unilateral genital pores, a rostellum armed with a single crown of hooks, a single set of male and female genitalia per proglottis and a small number of testes per proglottis indicate that the cestodes from Crithagra citrinelloides in Ethiopia belong to the subfamily Hymenolepidinae. This is the most specious hymenolepidid subfamily having more than 40 genera (Czaplinski & Vaucher, 1994; Mariaux et al., 2017). The majority of them are characterised by the presence of 8 or 10 rostellar hooks. The cestodes from Wondo Genet belong to a genus which is clearly distinguished from the remaining hymenolepidids of birds by a unique set of characters, i.e

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