Isoglaridacris brevicollis, Toma & Scholz & P & Leon, 2021

Toma, Scholz, s, P, Gerardo & Leon, erez-Ponce de, 2021, Caryophyllidean tapeworms (Cestoda), Nearctic parasites of fish in Mexico, including description of a new species of Isoglaridacris and the first report of Khawia japonensis, an invasive parasite of common carp (Cyprinus carpio), International Journal for Parasitology: Parasites and Wildlife 15, pp. 70-78 : 73-74

4. Isoglaridacris brevicollis sp. n. Fig. 2A–F

Synonym: Isoglaridacris sp. of P´erez-Ponce de Leon´et al. (2010).

Material studied: four specimens from Catostomus nebuliferus Garman, Rio Covadonga, Penon ˜Blanco, Durango, collected by Rogelio Aguilar-

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Aguilar ( CNHE 6761, 6802; IPCAS C- 885); ten spec. from Catostomus bernardini Girard, Rio Bavispe , Sonora, collected by Rogelio Rosas-Vald´ez in November 2008 ( CNHE 6796); two spec. from Moxostoma astrinum Bean, Atengo , Jalisco, collected by Rogelio Rosas-Vald´ez in November 2008 ( CNHE 6799).

Description (based on whole mounts of four specimens, including one contracted; measurements in micrometres unless otherwise stated): Caryophyllidea , Capingentidae (as emended by Scholz et al., 2021; formerly in the Caryophyllaeidae sensu Mackiewicz, 1994 ). Body elongate, robust, 10.0– 12.6 mm long, with maximum width 798–1054 mm at anterior third or middle of body (length: width ratio 1: 0.07–0.09); width of body at level of cirrus-sac 713–837, at level of ovarian isthmus 615–701.

Scolex widely rounded, 540–611 wide, with central pair of shallow loculi; lateral loculi very shallow or indistinguishable ( Fig. 2A, B, D ); apical disc absent, anterior edge of scolex slightly convex ( Fig. 2B, D ) or almost blunt ( Fig. 2A ). Neck indistinct, body at level of first vitelline follicles 570–652 wide. Inner longitudinal muscles well-developed. Osmoregulatory canals form 8 pairs of main longitudinal, anastomosed canals. Excretory bladder elongate, with widened proximal and long, narrow distal (terminal) part, 158–208 long and 72–88 wide. Excretory pore terminal.

Testes medullary, subspherical to widely oval, 123–273 long and 114–193 wide, arranged in 2 longitudinal rows and 2 layers; testes numbering 154–180 (mean 168; n = 4). Anterior-most testes begin 1015–1618 posterior to anterior extremity, i.e., 9–13% of total body length, 201–324 posterior to anterior-most vitelline follicles. Posteriorly, testes reach anterior to cirrus-sac, slightly anterior to posterior-most preovarian vitelline follicles ( Fig. 2C ). Cirrus-sac thick-walled, subspherical, wider than long, 200–256 long and 230–287 wide; width of cirrus-sac represents 32–34% of body width at level of cirrus-sac. External seminal vesicle thick-walled, pyriform, 177–207 long and 93–123 wide. Gonopore single, situated 137–266 anterior to ovarian wings.

Ovary inverted A-shaped, with long and narrow ovarian wings, posterior wings approaching to each other ( Fig. 2A, C ) or overlapping one another ( Fig. 2F ), but never connected posteriorly. Ovarian arms 1168–1631 long, i.e., 11–13% of total body length, and 160–231 wide near isthmus. Maximum width of ovary at level of anterior-most ovarian wings 534–652; width at level of ovarian isthmus 461–568. Ratio of length of ovarian wings to length of uterus area 1: 0.86–1.09. Vagina tubular, slightly sinuous; seminal receptacle absent ( Fig. 2F ).

Vitelline follicles medullary, variable in shape and size, 72–212 long and 42–143 wide. Preovarian vitelline follicles numerous, begin anterior to first testes, 691–1420 posterior to anterior edge of scolex, i.e., 7–11% of total body length. Posteriorly, preovarian vitelline follicles do not reach to ovary (finish at distance of 151–238 from ovary; Fig. 2C ). Postovarian vitelline follicles relatively few (estimated as 15–30 follicles), forming small, compact group near posterior extremity, between posterior ovarian wings ( Fig. 2A, C ) or slightly more posterior ( Fig. 2F ).

Uterus coiled, forming a few loops posterior to ovarian isthmus; anteriorly, loops reach to level of cirrus-sac, never more anteriorly ( Fig. 2C ). Uterine glands well-developed, absent only in most distal and proximal parts of uterus ( Fig. 2C ). Uterus area 1440–1500 long, i.e., 12–15% of total body length. Eggs operculate, without fully formed oncosphere in utero; intrauterine eggs in whole mounts 36–41 long and 23–26 wide (n = 11).

Figures

Fig. 2. Isoglaridacris brevicollis sp. n. from Catostomus nebuliferus, Durango (CNHE 6802; IPCAS C-885; 2x CNHE 6761) (A–D), Catostomus bernardini, Sonora (CNHE 6796) (E), and Moxostoma astrinum, Jalisco (CNHE 6799) (F); Pseudoglaridacris confusa (Hunter, 1929) from Ictiobus meridionalis, Oaxaca (CNHE 6798) (G). A – total view, ventrally; B – anterior end; C – posterior end, ventrally; D – slightly contracted scolex; E – cirrus-sac with external seminal vesicle, ventrally; F – ovary with overlapping posterior wings, dorsally (uterine loops are omitted at level of ovarian isthmus and more posteriorly); G – total view, dorsally. Abbreviations: cgp – common genital pore; cs – cirrus-sac; eb – excretory bladder; esv – external seminal vesicle; lo – loculi; ov – ovary; povf – postovarian vitelline follicles; sd – sperm duct (vas deferens); te – testes; ut – uterus; va – vagina; vd – vitelline duct; vf – vitelline follicles.