Ruhnkebothrium mattisi, Caira & Bueno & Jensen, 2021

Caira, Janine N., Bueno, Veronica & Jensen, Kirsten, 2021, Emerging global novelty in phyllobothriidean tapeworms (Cestoda: Phyllobothriidea) from sharks and skates (Elasmobranchii), Zoological Journal of the Linnean Society 193, pp. 1336-1363 : 1342-1345

RUHNKEBOTHRIUM MATTISI SP. NOV.

( FIGS 2A–C , 3 )

ZooBank registration: 79276324-95ED-41AC-8B82- 544744F596AB.

Description: [Based on two whole mature worms, one partial mature worm (hologenophore), one detached mature proglottid, three detached gravid proglottids, three detached dehisced proglottids, and two scolices examined with SEM.] Worms euapolytic, acraspedote, 33.6–36.2 mm long; proglottids 127–145 in total number; maximum width at level of scolex or terminal proglottid. Scolex consisting of four bothridia, 1043– 1223 long, 1121–1743 wide. Bothridia consisting of small, simple anterior loculus ( Fig. 3B ) and expansive, highly folded posterior loculus ( Figs 2A , 3A ), 1043–1223 (1111 ± 98; 2; 3) long, 509–878 (692 ± 179; 2; 4) wide, sessile anteriorly, free posteriorly; anterior loculus 69–94 (78 ± 10; 2; 5) long, 74–96 (87 ± 8; 2; 6) wide. Cephalic peduncle lacking. Neck 2255–3245 long. Distal surface of anterior loculus with slender gladiate spinitriches and capilliform filitriches ( Fig. 3D ); distal surface of anterior, narrow portion of posterior loculus with slender gladiate spinitriches and capilliform filitriches ( Fig. 3E, F ); distal surface of posterior loculus with dispersed slender gladiate spinitriches and densely arranged capilliform filitriches ( Fig. 3G ); capilliform filitriches becoming less dense near margins of distal surfaces of posterior loculus; rim of distal surface of posterior loculus with small band of papilliform filitriches only ( Fig.3C ). Proximal bothridial surface with extremely slender gladiate spinitriches and capilliform filitriches ( Fig. 3H ). Neck ( Fig. 3I ) and strobila with capilliform filitriches arranged in narrow, convex scutes. Immature proglottids wider than long, becoming longer than wide with maturity ( Fig. 2B ), 120–142 in number. Mature proglottids three to seven in number. Terminal proglottid 1326–2448 long, 1420– 1585 wide; length-to-width ratio 0.9–1.5:1 ( Fig. 2C ). Testes 211–306 (256 ± 44; 3; 5) in total number, 43–78 (59 ± 16; 3; 5) in number in post-poral field, 47–70 (56 ± 8; 2; 8) long, 58–86 (73 ± 8; 2; 8) wide. Vas deferens minimal, coiled medial to cirrus sac. Cirrus sac narrowly oblong (sensu Clopton, 2004), slightly curved anteriorly, 588–623 long, 118–155 wide, thin walled, containing coiled cirrus; cirrus armed with spinitriches. Genital pores irregularly alternating, 62–68% of proglottid length from posterior end; genital atrium shallow. Vagina surrounded by glandular cells, weakly sinuous, extending from ootype along midline of proglottid to anterior margin of cirrus sac, then laterally along anterior margin of cirrus sac to open into common genital atrium anterior to cirrus. Ovary at posterior of proglottid, H-shaped in frontal view, 421–808 long, 737–810 wide, tetralobed in crosssection; ovarian margins digitiform. Vitellarium follicular; follicles somewhat irregular in shape, arranged in two lateral bands; each band consisting of multiple columns of follicles, extending throughout length of proglottid, interrupted dorsally and ventrally by terminal genitalia, not interrupted by ovary. Uterus medial, ventral, sacciform, extending from ovarian isthmus to cirrus sac; uterine duct entering uterus at mid-level. Excretory vessels 4, arranged in one dorsal and one ventral pair on each lateral margin of proglottid. Detached mature proglottids 2477 long, 1782 wide, length-to-width ratio 1.4:1; genital pore 63% of proglottid length from posterior end; testes 229 in total number, 66 in post-poral field, 77–93 (87 ± 7; 1; 4) long, 77–87 (82 ± 4; 1; 4) wide; cirrus sac 562 long, 124 wide; ovary 615–701 long, 578–606 wide. Detached gravid proglottids (two from same host) 3514–5395 long, 1773–2001 wide, length-to-width ratio 2.0– 2.7:1; genital pore 51–60% of proglottid length from posterior end; testes degenerated; cirrus sac 627–740 long, 191–203 wide; ovary 766–807 long, 807–869 wide; oncospheres spherical, 22–26 (24 ± 1; 2; 8) long, 21–26 (25 ± 2; 2; 8) wide, too densely packed to assess whether packaged in cocoons. Detached dehisced proglottids (four from three different hosts) 2938–3947 (3407 ± 416; 4) long, 1096–1394 (1228 ± 150; 4) wide, length-to-width ratio 2.5–3.1 (2.8 ± 0.2; 4):1; genital pore 50–53% (50 ± 2; 4) of proglottid length from posterior end; testes degenerated; cirrus sac 554–689 (623 ± 68; 3) long, 162–217 (194 ± 29; 3) wide; ovary 638–721 (690 ± 36; 4) long, 477–894 (689 ± 175; 4) wide.

Ty p e h o s t: S p h y r n a l e w i n i 1 o f t h e s c a l l o p e d hammerhead complex (sensu Naylor et al., 2012) ( Carcharhiniformes: Sphyrnidae ).

Type locality: Gulf of Mexico off Pensacola, FL, USA (30°03′25.26″N, 87°00′13.01″W) .

Additional localities: Gulf of Mexico off Horn Island, MS, USA (30°13′59.37″N, 88°40′10.79″W); Atlantic Ocean, FL, USA (28°00′18″N, 80°04′18″W) .

Site of infection: Spiral intestine.

Type material: Holotype (mature worm, USNM no. 1638656), four paratype detached proglottids (one mature, USNM no. 1638657; one gravid, USNM no. 1638658; two dehisced, USNM nos 1638659 and 1638660); two paratypes [one complete mature worm, LRP no. 10295; one partial mature worm (hologenophore) LRP no. 8304]; three paratype detached proglottids (two gravid, LRP nos 10296 and 10297; one dehisced, LRP no. 10298); two paratypes (immature worm SEM vouchers, LRP nos 10274 and 10299).

Sequence data: GenBank accession KF865889, hologenophore LRP no. 8304 (TE-86; DEL-6).

Etymology: This species is named after the late Dr Tom Mattis, not only for providing some of the type material, but also for his life-long interest in cestode taxonomy.

Provisional name: New genus 10 n. sp. 1 of Caira et al. (2014).

Figures

Figure 2. Line drawings of adults of Ruhnkebothrium (specimen accession numbers in parentheses). A, scolex of Ruhnkebothrium mattisi (LRP no. 10295). B, whole worm of Ru. mattisi (LRP no. 10295). C, mature proglottid of Ru. mattisi (USNM no. 1638656). D, scolex of Ruhnkebothrium bajaense (CNHE no. 10662). E, mature proglottid of Ru. bajaense (CNHE no. 10662).

Figure 3. Scanning electron micrographs of Ruhnkebothrium mattisi. A, scolex. B, detail of anterior loculi. C, distal surface of rim of posterior loculus. D, distal surface of anterior loculus. E, distal surface of anterior-most region of posterior loculus adjacent to anterior loculus. F, distal surface of posterior loculus as it expands. G, distal surface of expanded region of posterior loculus. H, proximal surface of posterior loculus. I, scutes on surface of neck.