Caulobothrium multispelaeum, Caira & Jensen, 2021

Caira, Janine N. & Jensen, Kirsten, 2021, Two new species of Caulobothrium (Cestoda: “ Tetraphyllidea ”) from the duckbill eagle ray, Aetomylaeus bovinus (Myliobatiformes: Myliobatidae), off Senegal with new insights on morphological features of the genus, Zootaxa 4903 (1), pp. 127-139 : 129-132

Caulobothrium multispelaeum n. sp.

( Figs. 1 , 2 , 5A, B )

Zoobank No. 42058EBB-7255-4144-8ACA-C6E89A78BF16

Type host: Aetomylaeus bovinus (Geoffroy St. Hilaire) , duckbill eagle ray ( Myliobatiformes : Myliobatidae ).

Type locality: Diogue (12°34’30”N, 16°45’2”W), Casamance , Senegal, Atlantic Ocean .

Additional locality: St. Louis (16°1’28”N, 16°30’33”W), Senegal, Atlantic Ocean .

Site of infection: Spiral intestine.

Prevalence of infection: 100% (2 of 2 duckbill eagle rays examined).

Type specimens: MNHN No. HEL1365 (holotype), Nos. HEL1366–1368 (3 paratypes); LRP Nos. 10300– 10304 (5 paratypes), LRP Nos. 10228–10242 (cross sections of strobila of 1 paratype stained with H&E); LRP Nos. 10257–10259 (cross sections of strobila of 1 paratype stained with PAS) ; USNM Nos. 1638625–1638630 (6 paratypes); SEM specimens retained in the personal collection of the senior author .

Etymology: multi, L., many; spelaeum, L., pits—refers to the unusual, tandem series of apertures found along the dorsal and ventral surfaces of the strobila of this species.

Description. Based on whole mounts of 15 mature worms, cross sections of mature proglottids from 2 worms (1 series stained with H&E and 1 with PAS), and 4 worms, 1 free proglottid, and 1 strobilar fragment examined with SEM.

Worms euapolytic, 1.7–3.4 (2.5 ± 1; 15) mm long; maximum width 353–511 (408 ± 49; 14) at level of scolex; 8–18 (12 ± 3; 15) proglottids per worm. Scolex consisting of 4 stalked bothridia and cephalic peduncle. Bothridia 331–484 (380 ± 38; 13; 24) long, 121–174 (155 ± 13; 14, 26) wide, bearing single anterior loculus with apical sucker ( Figs. 1A , 2B ) and 2 columns of 14–16 (15 ± 0.7; 12; 14) loculi; loculi 29–33 (30 ± 1; 13, 22) in total number; apical sucker 15–32 (20 ± 5; 10, 17) long, 14–26 (21 ± 3; 11; 20) wide. Cephalic peduncle short, 45–102 (66 ± 17; 14) long, 108–193 (136 ± 24; 12) wide.

Distal surface of septa and most bothridial loculi with densely arranged capilliform filitriches ( Fig. 2E ); distal surface of anterior-most loculus and apical sucker with blend of acicular and papilliform filitriches; distal surface of bothridial rims with band of papilliform filitriches. Proximal surface of bothridium with papilliform and acicular filitriches ( Fig. 2F ). Cephalic peduncle surface with acicular filitriches. Spinitriches not observed on any scolex surfaces. Surfaces of proglottids away from grooves and apertures with acicular filitriches ( Fig. 2G ); surfaces of grooves and apertures with capilliform filitriches.

Strobila with conspicuous medial longitudinal grooves along dorsal and ventral surfaces ( Fig. 2C ); grooves expanding laterally to form tandem series of elliptical apertures on posterior proglottids ( Fig. 2D ). Proglottids acraspedote. Immature proglottids 7–16 (11 ± 2; 15) in number, initially wider than long, becoming longer than wide with maturity. Mature proglottids 1–2 (1 ± 1; 15) in number; terminal mature proglottid 525–1,170 (845 ± 180; 15) long, 219–330 (279 ± 36; 15) wide; length to width ratio 2.2–4.8:1 (3.2 ± 1; 15). Genital pores lateral, alternating irregularly, 43–56% (48 ± 3; 15) of proglottid length from posterior margin of proglottid. Testes 29–44 (35 ± 4; 14; 20) in total number, 10–48 (30 ± 10; 14; 42) long, 34–102 (67 ± 17; 14; 42) wide, arranged in 2 regular columns, 1 layer deep in cross section ( Fig. 5A ); each column extending from near anterior margin of proglottid to slightly posterior to anterior margin of ovary; post-poral testes present, 2–6 (4 ± 1; 14, 20) in number; post-ovarian testes absent. Vas deferens coiled, joining cirrus sac at antero-medial margin. Cirrus sac bent slightly anteriorly, elongate oval, 73–134 (106 ± 16; 12) long, 26–46 (37 ± 6; 12) wide, extending to near midline of proglottid, containing cirrus; cirrus unarmed. Ovary 103–393 (214 ± 83; 14) long, 95–231 (169 ± 35; 14) wide, H-shaped in dorso-ventral view, tetralobed in cross section ( Fig. 5B ); ovarian margins lobulated. Vagina weakly sinuous, extending from ootype along midline of proglottid, passing ventral to cirrus sac, opening into genital atrium ventral to cirrus; vaginal sphincter not observed. Vitellarium follicular; vitelline follicles generally wider than long, 6–30 (15 ± 5; 15; 45) long, 7–68 (34 ± 13; 15; 45) wide, in 1 dorsal and 1 ventral column on each lateral margin of proglottid dorsal and ventral to testes ( Fig. 5A ); columns extending from anterior margin of testicular field to near posterior margin of proglottid, uninterrupted by terminal genitalia and ovary. Uterus medial, ventral, sacciform, extending to near anterior margin of testicular field. Excretory vessels 4, arranged in 1 dorsal and 1 ventral pair on each lateral margin of proglottid. Eggs not observed.

Remarks. Caulobothrium multispelaeum n. sp. is unique among the eight valid species of Caulobothrium (see Caira et al. 2017; Coleman et al. 2019) in its possession of a medial groove along each of the dorsal and ventral surfaces of the strobila that develop into a tandem series of elliptical apertures on the posterior proglottids. In addition, with a total length (TL) of 1.7–3.3 mm, it is a much smaller worm than Caulobothrium longicolle ( Linton, 1890) Baer, 1948 , C. opisthorchis , Caulobothrium ostrowskiae Brooks, Mayes, and Thorson, 1981 , C. tetrascaphium , Caulobothrium tobijei ( Yamaguti, 1934) Baer, 1948 , and Caulobothrium uruguayense Brooks, Mayes, and Thorson, 1981 (with TLs of 28, less than 15, up to 15, 200, 80, and 30 mm, respectively). Caulobothrium multispelaeum n. sp. further differs from its smaller congeners, Caulobothrium myliobatidis Carvajal, 1977 and Caulobothrium pedunculatum , in its possession of fewer loculi per bothridium (29–33 vs. 54–58 and 56–62, respectively).

Cross sections through the proglottids of C. multispelaeum n. sp. showed that the grooves open into a larger cavity, the lining of which stains positively with PAS, especially along the inner-most surfaces. These results lead us to believe that these cavities may produce some sort of mucopolysaccharide.

This species was assigned the provisional name Caulobothrium n. sp. 2 by Healy et al. (2009) and in the associated GenBank record (No. FJ177102 ). We are hereby formally naming this species Caulobothrium multispelaeum n. sp.

Figures

FIGURE 1. Line drawings of Caulobothrium multispelaeum n. sp. from Aetomylaeus bovinus off Senegal. A. Scolex (paratype; USNM No. 1638628). B. Whole worm (paratype; USNM No. 1638628). C. Mature proglottid (holotype; MNHN No. HEL1365). D. Detail of terminal genitalia and ootype region, elliptical depressions/apertures removed (holotype; MNHN No. HEL1365).

FIGURE 2. Scanning electron micrographs of Caulobothrium multispelaeum n. sp. from Aetomylaeus bovinus off Senegal. A. Scolex; small letters indicate locations of details in E and F. B. Anterior region of bothridium showing apical sucker; inset light micrograph of same region. C. Medial longitudinal groove on immature proglottids; small letter indicates location of detail in G. D. Mature proglottid with medial longitudinal groove expanded laterally to form tandem series of elliptical apertures. E. Distal surface of bothridium. F. Proximal surface of bothridium. G. Surface of strobila.

FIGURE 5. Light micrographs of sections of Caulobothrium multispelaeum n. sp. and Caulobothrium katzi n. sp. stained with Delafield’s hematoxylin and counter-stained with eosin. A. Cross section of mature proglottid of C. multispelaeum n. sp. anterior to cirrus sac. B. Cross section of mature proglottid of C. multispelaeum n. sp. at level of ovarian isthmus. C. Cross section of mature proglottid of C. katzi n. sp. anterior to cirrus sac. D. Cross section of mature proglottid of C. katzi n. sp. slightly posterior to ovarian isthmus. Abbreviations: O, ovary; T, testis; VF, vitelline follicle.