Hobergia irazuensis, Gardner & Dursahinhan & Campbell & Rácz, 2020

Gardner, Scott L., Dursahinhan, Altangerel T., Campbell, Mariel L. & Rácz, S. Elizabeth, 2020, A new genus and two new species of unarmed hymenolepidid cestodes (Cestoda Hymenolepididae) from geomyid rodents in Mexico and Costa Rica, Zootaxa 4766 (2), pp. 358-376 : 364-367

Hobergia irazuensis n. gen., n. sp.

( Figures 1–6 )

LSIDurn:lsid:zoobank.org:act: 84C2C2D1-5ACC-4177-9EC4-BE630DC7FB8

Type Host: Heterogeomys heterodus (Peters, 1865) .

Type locality: Agricultural field, approximately 12 km from Irazú volcano, on the northeastern edge of Potrero Cerrado, Cartago, Costa Rica, altitude 2,140 m; lat. 9°55´18” N, long. 83°52´41” W.

Symbiotype host: (See Frey et al., 1992) Variable pocket gopher, Heterogeomys heterodus (Peters 1865) ( Rodentia : Geomyidae ).

Symbiotype catalog number: Not available.

Type locality/collection date: Potrero Cerrado, Cartago, Costa Rica, Elevation: 2,140 m; lat. 9°55´18” N, long. 83°52´41” W; 28 March 1990.

Collector: Dr. Never Bonino and students.

Site of infection: Small intestine.

Prevalence: (5.3%) 2 of 38 specimens of Heterogeomys heterodus infected, one male and one female.

Specimens deposited: Holotype, HWML139040

Specimens examined: Paratypes: HWML 39041, HWML 139042, HWML 139043, HWML 139044, HWML 139045, HWML 13946, HWML 13947, HWML 13948, HWML 13949, HWML 13950, HWML 13951, HWML 13952, HWML 13953, HWML 139054.

Description: Fourteen specimens were studied for the following description, not all specimens had all characters visible. Scolex unarmed ( Fig. 1 ), N = 5, 334–426 (393 ± 30) in maximum width. Apical organ (AO) present, N = 13, 20–32 (24 ± 3) in length. Each osmoregulatory duct terminates in the scolex near posterior end of AO but none penetrate the AO sac (posterior part of the AO) [ Figure 1 ]. Apical organ sac, N = 12, 96–128 (114 ± 9) long by N= 9, 61–75 (68 ± 5) wide. Apical organ sac not reaching beyond the posterior margins of suckers. Suckers, N = 48, 102–146 (128 ± 11) long by N = 53, 110-161 (134 ± 11) wide. Well-defined foveolae present ( Figure 2 ). Neck, N = 8, 708–899 (801 ± 66) long by N= 12, 261-307 (284 ± 17) in maximum width. Strobila, N = 4, 52.85 mm– 64.64 mm (60.00 ± 5.13 mm) long, with N = 8, 531–640 (587 ± 34) proglottids; maximum width N = 7, 1.69–2.18 mm (1.91 ± 0.19 mm) occurs in gravid proglottids immediately anterior to terminal proglottids. Strobilar margins craspedote with intersegmental divisions clearly evident in mature and gravid proglottids; length-width ratio of mature and gravid proglottids 0.09–0.12 (N = 17) and 0.15–0.19 (N = 13). Proglottids wider than long. Genital pores unilateral, dextral, non-alternating. Genital atrium depth, N = 7, 14–18 (16 ± 2). Vaginal opening posterior and slightly ventral to cirrus opening. Genital ducts pass dorsally to longitudinal excretory canals. Dorsal canals, N = 15, 5–7 (6 ± 1) wide. Ventral canals, N = 20, 42–57 (51 ± 5) wide. Anlagen of genitalia first appearing N = 2,828–852 (840 ± 17) from anterior end. Cirrus sac piriform, N = 22, 145–197 (165 ± 16) in maximum length by N = 21, 41–56 (47 ± 5) in maximum width, antiporal end not overlapping excretory canals. Cirrus claviform, armed with minute spines, N = 11, 1.1-1.5 (1.2 ± 0.1) in length. Cirrus armature patterned in well-defined gridded rows ( Fig. 3 ). Internal seminal vesicle piriform, N = 12, 85–111 (98 ± 9) long by N = 14, 34–44 (38 ± 4) wide. External seminal vesicle (ESV), N =24, 220–289 (251 ± 23) long by N = 15, 70–90 (80 ± 5) in maximum width. ESV, elongate, fusiform, situated anterior to poral testis. Testes N = 58, 132–179 (155 ± 15) long by N = 36, 78–107 (91 ± 9) wide, one poral and two antiporal. Testes arrangement usually triangular, sometimes more linear, arrangement depends on level of contrac- tion (or relaxation) of strobila (relaxed strobila always with testes arranged in triangular pattern ( Fig. 4 ). Seminal receptacle, N = 12, 369–482 (419 ± 41) long by N = 18, 55–74 (64 ± 6) in maximum width, extending anterior to ovary. Ovary N = 19, 125–166 (148 ± 15) in maximum length by N = 45, 288–405 (341 ± 32) in maximum width. Ovary markedly bilobed, each lobe subdivided into globular fan-shaped lobules extending laterad. Lateral lobes connected centrally in segment via thin isthmus ( Fig. 4 ). Vitelline gland, N = 42, 132–199 (172 ± 17) wide by N = 31, 57–79 (67 ± 6) in maximum length, margins with small lobules, situated medially and posterior to ovary and anterior to transverse ducts of ventral osmoregulatory canals. Uterus first appearing as undefined tube extending bilaterad from area of o ӧtype, appearing quickly in developing mature proglottids with uterus extending transversely through segment before eggs are evident within. Gravid proglottids filled entirely by saccular uterus. Internal organs, displaced by gravid uterus, persist in gravid proglottids ( Fig. 5 ). Strobila with anapolytic proglottids. Eggs N = 51, 34–45 (39 ± 3) long by N = 51, 25–42 (34 ± 3) wide, sub-spherical. Embryo, N = 51, 20–28 (24 ± 2) long by N = 51, 18–27 (21 ±2) wide ( Fig. 6 ), with sub-spherical shape. Embryo hooks as follows: larger hooks of first and third pairs, total length, N = 51, 9–12 (11 ± 1) long by N = 51, 2–3 (2 ± 0.2) wide at guard. Handle, N = 51, 4–7 (6 ± 1) long, blade, N = 51, 3–5 (4 ± 0.3) long. Larger hooks of first and third pairs have robust, wide guards. Smaller hooks of first and third pairs, total length, N = 45, 9–13 (11 ± 1) long by N = 46, 1–2 (1.8 ± 0.2) wide at guard. Handle, N = 46, 4–7 (6 ± 1) long, blade, N = 46, 3–5 (4 ± 0.4) long. Smaller hooks of first and third pairs have narrow, more delicate guards. Middle pair of hooks, total length, N = 24, 11–14 (12 ± 1) long by N = 24, 1–2 (1.7 ± 0.2) wide at guard, handle, N = 24, 6–8 (7 ± 1) long, blade, N = 24, 4–6 (5 ± 1) long. Middle pair of hooks usually longer than hooks of 1st and 3rd pairs with a less tapered guard and deeply rounded blade.

Etymology: Hobergia irazuensis n. sp. was named for the Volcán Irazú near the type locality, Costa Rica, northern Neotropical region.

Remarks: Hobergia irazuensis n. gen., n. sp. exhibits the characteristics of Hymenolepis as defined by Schmidt (1986) but refined and complemented by Makarikov & Tkach (2013). The following comparisons are restricted to members of the genus Hymenolepis known to occur in mammals of the Nearctic region, see Gardner (1985) and Gardner & Schmidt (1988).

Comparison of H. irazuensis n. gen., n. sp. with other hymenolepidids found in the Nearctic

Hobergia irazuensis n. gen., n. sp. is readily distinguishable from all other known species of Hymenolepididae in the Nearctic by the presence of sucker foveolae on the scolex. Each of the four suckers on the scolex has a pocketlike foveola in which the sucker can retract. The tissue of the foveola covers each sucker with a thin membrane ( Fig. 2 ) which appears striated and likely involved in foveola structure or function in retraction of the suckers into the foveolae. Additionally, H. irazuensis can be differentiated from species of Hymenolepis s. str. in the Nearctic by the following characters: Ovary extremely bilobed with a central thin isthmus only a few cells in diameter; no other described species of Hymenolepis s. str. has this structure. In addition, the new species has a much longer and wider scolex and wider neck relative to all described species.

Figures

FIGURE 1. Scolex of Hobergia irazuensis n. gen., n. sp. showing details of apical organ and apical organ sac. Line indicates apical organ sac.

FIGURE 2. Scolex of Hobergia irazuensis n. gen., n. sp. showing detail of membranes on the scolex that cover the suckers creating a foveola or pocket into which each sucker can be retracted. Line indicates pocket opening.

FIGURE 3. Image of distal end of cirrus sac of Hobergia irazuensis n. gen., n. sp. showing the spinose nature of the cirrus (line).

FIGURE 4. Line drawing of last mature proglottid of Hobergia irazuensis n. gen., n. sp.

FIGURE 5. Image of terminal gravid proglottids of Hobergia irazuensis n. gen., n. sp. showing the uterus filled completely with eggs in the subterminal proglottid and the terminal segment with no eggs evident (anapolytic).

FIGURE 6. Egg of H. irazuensis n. gen., n. sp. showing extent of development of embryo hooks with usual dimorphic hooks of the lateral pairs and the monomorphic hooks of the central pair in the embryophore larva.