Echeneibothrium williamsi Carvajal & Dailey, 1975

Franzese, Sebastián, Mutti, Leonardo D., Tropea, Carolina & Ivanov, Verónica A., 2022, Morphological study of members of the genus Echeneibothrium (Cestoda: Rhinebothriidea: Echeneibothriidae) from rajiform skates of the Argentine Sea and analysis of the phylogenetic relationships within the family Echeneibothriidae, Zoologischer Anzeiger 299, pp. 1-20 : 12-13

publication ID	https://doi.org/ 10.1016/j.jcz.2022.05.002
publication LSID	lsid:zoobank.org:pub:2B1478CC-D510-4637-A784-D5283821EF7D
persistent identifier	https://treatment.plazi.org/id/039EC10C-5B0D-FFFA-FCB3-D077FBC1F880
treatment provided by	Felipe
scientific name	Echeneibothrium williamsi Carvajal & Dailey, 1975
status

Treatment

3.3. Echeneibothrium williamsi Carvajal & Dailey, 1975 View in CoL ( Figs. 1C View Fig ; 5E View Fig ; 8B View Fig ; 9 View Fig ; 10 View Fig )

3.3.1. Emended description

Based on whole mounts of 13 complete mature worms, 2 scoleces and 2 strobila, serial sections of 1 mature proglottid and 1 scolex, and SEM of 6 worms (25 specimens in total). Worms euapolytic, 4.3–9.1 mm (6.2 mm ± 1.8 mm, 9) long by 510–880 (681 ± 139, 7) wide, maximum width at level of scolex. Strobila composed of 32–76 (55 ± 15, 7) AML, anteriormost loculus; AS, apical sucker; L, length; PML, posteriormost loculus; W, width; *The authors did not specify whether measurement was taken from the terminal proglottid.

deep in cross-section ( Fig. 9C View Fig ). Cirrus sac oval, 150–205 (183 ± 16, 11) long by 95–125 (109 ± 10, 11) wide, containing coiled cirrus covered by spinitriches. Vas deferens dorsal, highly coiled, entering cirrus sac through its medial margin ( Fig. 9E View Fig ). Genital pores marginal, 42–58% (49 ± 4, 11) of proglottid length from posterior end.

Vagina thick-walled, extending from ootype along midline of proglottid to anterior margin of cirrus sac, then laterally along anterior margin of cirrus sac to common genital atrium ( Fig. 9B View Fig ); vaginal sphincter and seminal receptacle absent ( Fig. 9B, E View Fig ). Ovary near posterior end of proglottid, H-shaped in dorso-ventral view ( Fig. 9B View Fig ), tetralobed in cross-section ( Fig. 9D View Fig ), symmetric or asymmetric (50% of specimens with each type). Aporal lobe longer than poral lobe in asymmetric ovary, poral lobe 285–413 (327 ± 36, 10) long, aporal lobe 300–403 (341 ± 37, 10) long by 100–210 (149 ± 39, 9) wide at ovarian isthmus. Mehlis’ gland posterior to ovarian isthmus, 30–55 (46 ± 9, 6) in diameter ( Fig. 9B View Fig ). Vitelline follicles 10–38 (24 ± 8, 7, 35) long by 20–58 (38 ± 10, 7, 35) wide in 8 total columns; 2 dorsal columns and 2 ventral columns on each lateral margin of proglottid ( Fig. 9C, D View Fig ), extending uninterrupted along entire proglottid ( Fig. 9B, E View Fig ). Uterus sacciform, occupying midline of proglottid, from level of ootype to anterior margin of proglottid ( Fig. 9B View Fig ). Two pairs of osmoregulatory ducts, 1 dorsal pair and 1 ventral pair; dorsal ducts narrower than ventral ducts ( Fig. 9C, D View Fig ).

craspedote proglottids in number, 30–74 (53 ± 15, 7) immature, 2–3 (2 ± 0.5, 7) mature ( Fig. 1C View Fig ). Scolex with 4 stalked bothridia and apical myzorhynchus ( Figs. 9A View Fig ; 10A View Fig ). Bothridia facially loculated, 288–370 (325 ± 28, 11) long by 163–320 (278 ± 46, 11) wide. Distal bothridial surface divided by 10 (10 ± 0, 7) marginal septa into an anteriormost loculus and 9 (9 ± 0, 7) marginal loculi ( Figs. 9A View Fig ; 10A View Fig ); anteriormost loculus 35–80 (62 ± 17, 5) long by 58–78 (70 ± 8, 5) wide. Marginal septa formed distally by marginal muscle bundles and uninterrupted underlying radial muscles with same orientation as adjacent radial muscles ( Fig. 5E View Fig ). Bothridial stalks 125–235 (190 ± 36, 9) long by 75–150 (102 ± 24, 9) wide. Neck 60–113 (79 ± 14, 10) wide. Myzorhynchus consisting of elongated AMSP (sensu Caira et al. 1999) and apical organ (AO), not observed in fully everted form, 48–83 (60 ± 11, 7) wide when partially retracted. AMSP mostly retractable; AO invaginable with glandular cells ( Fig. 9A View Fig ). Proximal bothridial surface covered by gladiate spinitriches ( Fig. 10F View Fig ), muscular band of bothridial rim covered by papilliform filitriches ( Fig. 10G View Fig ). Distal bothridial surface covered by gladiate spinitriches interspersed with acicular filitriches ( Fig. 10E View Fig ). Stalks with acicular filitriches. AMSP with acicular filitriches along its entire length ( Fig. 10D View Fig ), anteriormost region with band of gladiate spinitriches interspersed with acicular filitriches ( Fig. 10C View Fig ). AO surface not observed with SEM. Neck with acicular filitriches.

Immature proglottids initially wider than long, becoming longer than wide with maturity. Subterminal mature proglottid 408–685 (503 ± 91, 7) long (velum included) by 265–360 (309 ± 35, 7) wide; velum 18–38 (28 ± 7, 7) long, covering 2–5% (3 ± 1, 8) of adjacent proglottid. Terminal mature proglottid 705–1230 (912 ± 161, 12) long by 240–365 (297 ± 41, 12) wide; width to length ratio 1: 3–4 (3 ± 1, 12) ( Fig. 9B View Fig ). Mature proglottids covered by acicular filitriches. Testes oval, 13–20 (16 ± 2, 8) per proglottid, 33–65 (49 ± 7, 8, 40) long by 50–98 (69 ± 11, 8, 40) wide, arranged in 2 columns anterior to cirrus sac ( Fig. 9B View Fig ), 1 layer

3.3.2. Taxonomic summary

Type host: D. chilensis ( Guichenot, 1848) , yellownose skate ( Rajiformes : Rajidae ).

Additional host: D. brevicaudatus ( Marini, 1933) , short tail yellownose skate ( Rajiformes : Rajidae ).

Type locality: South Pacific Ocean , between latitudes 32 ◦ 28 ′ S and 37 ◦ 15 ′ S (between Papudo and Talcahuano, Chile) .

Additional localities: Puerto Montt (41 ◦ 28 ′ S, 72 ◦ 56 ′ W), Chiloe ´Island (42 ◦ 33 ′ S, 73 ◦ 56 ′ W) GoogleMaps , Calbuco (41 ◦ 46 ′ S, 73 ◦ 07 ′ W), Niebla / Valdivia (39 ◦ 52 ′ S, 73 ◦ 23 ′ W) and Vina ˜del Mar (33 ◦ 01 ′ S, 71 ◦ 33 ′ W), Chile GoogleMaps . San Jorge Gulf (46 ◦ 13 ′ S, 66 ◦ 26 ′ W), Santa Cruz Province, Argentina GoogleMaps . Tolhuin (54 ◦ 29 ′ S, 65 ◦ 59 ′ W) and Río Grande (53 ◦ 31 ′ S, 67 ◦ 48 ′ W), Tierra del Fuego Province, Argentina GoogleMaps .

Site of infection: Spiral intestine.

Voucher material: 19 vouchers MACN-Pa No. 741/1–14, 742/1–4, 743 (13 whole mature worms, 2 scoleces, 2 strobila, and histological sections of 1 mature proglottid and 1 scolex).

Prevalence of infection: 60% (6 hosts infected out of 10 examined).

3.3.3. Remarks

The newly collected specimens of E. williamsi allowed for an emended description of the species, including the modification of the total length range and length ranges of some structures (i.e., bothridia, anteriormost loculus, bothridial stalks, testes and cirrus sac), width ranges of other structures (i.e., bothridia, bothridial stalks, neck, myzorynchus, testes and cirrus sac), and number of proglottids. The emended description also includes information omitted in the original description and redescription on the length of some structures (i.e., velum of subterminal proglottid and vitelline follicles), width of other structures (i.e., vitelline follicles), number of immature and mature proglottids, disposition of musculature in bothridial septa, percentage of the terminal proglottid covered by the velum, width to length ratio of the terminal proglottid, position of the vas deferens entrance into the cirrus sac, diameter and position of Mehlis’ glands, disposition of vitelline follicles within each lateral band, presence of osmoregulatory ducts, and the pattern of microtriches on neck and mature proglottid surfaces ( Table 4).

The emended description agrees with the original description by Carvajal & Dailey (1975) and disagrees with the redescription by Bueno & Caira (2017) in that there is no apical sucker on the distal bothridial surface. The corresponding structure is considered as an anteriormost loculus rather than an apical sucker because it has two straight lateral posterior margins and one straight central posterior margin rather than a single rounded posterior margin ( Fig. 8B View Fig ), which is the feature proposed by Caira et al. (1999) and Caira & Jensen (2021) to differentiate both structures. In addition, papilliform instead of acicular filitriches were found on the muscular band of the proximal bothridial surface, and acicular instead of capilliform filitriches were found on the distal bothridial surface. Finally, and contrary to the redescription by Bueno & Caira (2017), we failed to observe any kind of interruption of vitelline follicles at the cirrus sac or ovary level and we detected intraspecific variability in ovarian symmetry.