Cichlidocestus janikae, Alain de Chambrier & Carlos Daniel Pinacho-Pinacho & Jesus Servando Hernández-Orts & Tomáš Scholz, 2017

Alain de Chambrier, Carlos Daniel Pinacho-Pinacho, Jesus Servando Hernández-Orts & Tomáš Scholz, 2017, A New Genus And Two New Species Of Proteocephalidean Tapeworms (Cestoda) From Cichlid Fish (Perciformes: Cichlidae) In The Neotropics, J. Parasitol. 103 (1), pp. 83-94 : 89-90

Cichlidocestus janikae n. sp.

(Figs. 8–19)

Diagnosis (based on 6 specimens and anterior parts of 2 specimens studied using SEM from H. nicaraguensis in Costa Rica; measurements in micrometers unless otherwise stated; x ‾ = mean, n = number of measurements): Proteocephalidae, Proteocephalinae. Total body length up to 10 mm, maximum width 675 (n = 2). Strobila acraspedote (Fig. 17), anapolytic, consisting of about 30–32 proglottids: 23–24 immature, 1–2 mature, 4–6 pregravid, 1 gravid proglottid. Immature and mature proglottids wider than long (length:width ratio 0.28–0.69), pregravid and gravid proglottids wider than long to longer than wide (length: width ratio 0.69–1.54).

Scolex 240–260 long and 440–520 wide (n = 3), wider than neck (proliferation zone), 730–790 long and 330–440 wide. Scolex rosette-like, with 4 prominent lobes posteriorly, separated from one another by longitudinal grooves, each lobe bearing in center small uniloculate sucker, with internal circular musculature on its distal margin (Figs. 8–10); diameter of suckers 120–140 (n = 12). Apical part slightly conical, with a muscular sucker 70–75 long and 90–95 wide (Figs. 8, 10). Numerous cells with granular content situated between suckers. Apex of scolex, sucker cavities, anterior part of scolex, and proliferation zone covered with capilliform filitriches of similar appearance and density; proglottids covered with acicular spinitriches (data not shown).

Inner longitudinal musculature well-developed, formed by 1 irregular row of numerous small bundles of muscle fibers (Figs. 11, 12). Eight to 10 anastomosed ventral osmoregulatory canals situated in medulla beneath fibers of inner longitudinal musculature (Figs. 11, 12). Dorsal osmoregulatory canals paired, thickwalled, narrow.

Testes ovoid, small, 40–70 long and 35–45 wide, in 3–4 irregular layers, 63–74 (x ‾ = 70, n = 3) in number. Testes form 2 well separated groups (poral and aporal – Fig. 13), present also dorsal to cirrus-sac and vagina (Fig. 16): aporal group with 33–42 testes, and poral group with 27–38 testes. Posteriormost testes approach, but do not reach, to posterior margin of proglottids, being posterior to ovary (Fig. 13). Testes disappear in first pregravid proglottids.

Vas deferens strongly coiled, with loops forming elongated field crossing median line of proglottid (Fig. 13). Cirrus-sac pyriform to elongate, thin-walled, widened towards proximal part (Fig. 16), 110–135 long and 55–80 wide (n = 6), cirrus-sac length:width ratio 1.2–2.3, length of cirrus-sac represents 17–23% (x ‾ = 20%, n = 6) of proglottid width. Internal seminal vesicle voluminous, spherical, occupies almost entirely proximal half of cirrus-sac (Fig. 16). Cirrus short, muscular, reaching up to 40% of cirrus-sac length (n = 6). Common genital atrium narrow, deep (Figs. 13, 16), alternating irregularly, situated near anterior margin of proglottids, at 10–15% (x ‾ = 12, n = 6) of their length (Figs. 13, 16).

Ovary medullary, bilobed, with narrow, equatorially situated isthmus and 2 follicular (grape-like) lateral wings, occupying middle and posterior third of median space of proglottids (Fig. 13); length of ovary represents 43–57% of proglottid length (x ‾ = 50%, n = 12) and its width 35–46% of proglottid width (x ‾ = 41%, n = 7). Mehlis’ gland about 65–90 in diameter, representing 10– 14% of proglottid width (n = 5). Relative ovarian size (see de Chambrier et al., 2012) about 18% of size of mature and pregravid proglottids. Ovary disintegrates soon after appearance of first eggs (in third or fourth pregravid proglottid).

Vaginal canal almost straight in proximal part, slightly sinuous in distal part, with an elongated thick-walled seminal receptacle full of sperms in mature and first pregravid proglottids situated anterior to ovary isthmus (Fig. 13); terminal (distal) part of vaginal canal (pars copulathrix vaginae) surrounded by chromophilic cells and large, spherical vaginal sphincter (Fig. 16). Vagina posterior to cirrus-sac (n = 26).

Vitelline follicles medullary, forming 2 long, narrow, lateral bands not reaching to anterior margin of proglottids; follicles absent preporally, i.e., anterior to cirrus-sac on poral side (Figs. 13, 16). Length of bands represents 63–69% (x ‾ = 66%, n = 6) and 68–69% (x ‾ = 69%, n = 6) of length of proglottid on poral and aporal side, respectively, width of vitelline bands represent 8–11% of proglottid width.

Uterus medullary, with development of type 2 of de Chambrier et al. (2004a), i.e., uterine stem present as elongated longitudinal median concentration of chromophilic cells in immature proglottids, with lumen appearing in last immature proglottids. In mature proglottids, uterine stem thin-walled, with median lumen and almost invisible, long, and digitate diverticula. In pregravid proglottids, uterine diverticula (lateral uterine branches) thinwalled, digitate, lined with few chromophilic cells. Uterus with 8– 12 lateral diverticula on each side.

Eggs become progressively larger as they mature, considerably larger in gravid proglottids compared to those in most pregravid ones. Eggs spherical, hyaline outer envelope up to 100 in diameter (measured in eggs released from unmounted proglottids to water); embryophore bilayered, with external layer 44–46 in diameter and internal nucleate envelope 36–40 in diameter; oncosphere subspherical to spherical, 22–25 long and 20–22 wide, with 6 embryonic hooks 10–11 long (Figs. 14, 15). Uterine pore-like openings not observed.

Taxonomic summary

Type and only host: Hypsophrys nicaraguensis (Günther, 1864) ( Perciformes : Cichlidae ), vernacular name ‘moga amarilla’ (host field No. 844).

Type locality: Lake Arenal, Guanacaste Province, Costa Rica (10 8 29 ′ 18 ′ ′ N, 84 8 50 ′ 29 ′ ′ W).

Site of infection: Intestine.

Infection rate: One of 3 H. nicaraguensis from Lake Arenal examined on 19 February 2015 was infected with a hundred tapeworms (prevalence 33%; total length of infected fish 8 cm); the remaining 37 fish from other rivers in Guanacaste Province examined in February 2015 were negative.

Deposition of specimens: Holotype MHNG-PLAT 94085 (1 whole mount with a complete specimen and cross sections) and IPCAS C-734 (cross sections); 4 paratypes ( IPCAS C-734; whole mounts of 1 complete and 2 incomplete specimens) and cross sections, 1 paratype ( CNHE 10044; whole mount of 1 incomplete specimen), 1 paratype MHNG-PLAT 94086 (whole mount of a complete specimen and cross sections), 1 voucher (MHNG-PLAT 94087; anterior ends of 2 specimens and cross sections); all specimens from H. nicaraguensis (host field No. 844).

Etymology: Specific name refers to Janik Pralong from the Natural History Museum in Geneva for her excellent technical assistance over the past 10 yr.

Remarks

Cichlidocestus janikae shares with C. gillesi , type species of the genus, the characteristics unique or rare among the Proteocephalidea such as the possession of a large ovary occupying two-thirds of the medial region of proglottids, with grape-like (follicular) lateral wings (Fig. 13), a peculiar morphology of the cirrus-sac, which contains a spherical internal seminal vesicle in its proximal part (Fig. 16), a quadrilobed scolex with a well-developed muscular apical sucker (Figs. 8–10, 18, 19), several anastomosed ventral osmoregulatory canals, and the testes disappearing in the first pregravid proglottids.

The new species from Costa Rica can be distinguished from C. gillesi by the extent of vitelline follicles on the poral side, with follicles absent anterior to the cirrus-sac and vagina (Figs. 13, 16; vs. present preporally in P. gillesi ; see Figs. 2–4), larger eggs (diameter of the external layer of the embryophore 44–46 µm in C. janikae vs. 30–33 µm in C. gillesi ) that increase during their development in the uterus in the former species (in C. gillesi , they do not increase markedly during their intrauterine development), fewer uterine diverticula (8–12 in C. janikae vs. 16–21 in the latter species), and more testes (63–74 in C. janikae vs. 37–46 in C. gillesi ).