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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

Site of infection: Spiral intestine.

Voucher material: 20 vouchers MACN-Pa No. 737/1–10, 738, 739, 740/1–8 (17 whole mature worms, and histological sections of 1 mature proglottid and 2 scoleces).

Prevalence of infection: 80% (8 hosts infected out of 10 examined).

3.2.3. Remarks

The newly collected specimens of E. multiloculatum allowed for an emended description of the species, including the modification of length ranges of some structures (i.e., bothridia, anteriormost loculus, testes, cirrus sac, ovarian poral and aporal lobe), width ranges of other structures (i.e., neck, myzorynchus and cirrus sac), and genital pore position. The emended description also includes information omitted in the original description and redescription on the length of some structures (i.e., posteriormost loculus, velum of subterminal proglottid and vitelline follicles), width of other structures (i.e., posteriormost loculus and 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, location 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 shows a straight posterior margin rather than a rounded posterior margin ( Fig. 8A of the present study and Fig. 7 of Bueno & Caira 2017), which is the feature proposed by Caira et al. (1999) and Caira & Jensen (2021) to differentiate both structures. In addition, the emended description is consistent with that by Carvajal & Dailey (1975), but not with that by Bueno & Caira (2017), in that there is a medial longitudinal septum in bothridia, as demonstrated in histological sections of bothridial musculature ( Fig. 5D of the present study). 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.

Figures

Fig. 8. Light micrographs of anteriormost loculus of Echeneibothrium spp. (A) Echeneibothrium multiloculatum Carvajal & Dailey, 1975 from Dipturus brevicaudatus (voucher MACN-Pa No. 737/5). (B) Echeneibothrium williamsi Carvajal & Dailey, 1975 from Dipturus brevicaudatus (voucher MACN-Pa No. 741/13). Arrowheads indicate the posterior margin (A) and the central posterior and lateral posterior margins (B).

Fig. 7. Scanning electron micrographs of Echeneibothrium multiloculatum Carvajal & Dailey, 1975 from Dipturus brevicaudatus. (A) Scolex, small letters indicate the location of details shown in Fig. 7B–D. (B) Distal bothridial surface. (C) Proximal bothridial surface. (D) Surface of anteriormost region of the apical modification of scolex proper (AMSP), small letter indicates the location of detail shown in Fig. 7E. (E) Detail of the surface of anteriormost region of the AMSP. (F) Neck surface.

Fig. 5. Septal musculature of bothridium of Echeneibothrium spp. (A) Longitudinal section of bothridium of Echeneibothrium cristinae sp. nov. from Bathyraja cousseauae (paratype MACN-Pa No. 736/22). (B) Transverse section of bothridium of Echeneibothrium cristinae sp. nov. from Bathyraja cousseauae (paratype MACN-Pa No. 736/23). (C) Longitudinal section of bothridium of Echeneibothrium multiloculatum Carvajal & Dailey, 1975 from Dipturus brevicaudatus (voucher MACN-Pa No. 738). (D) Transverse section of bothridium of Echeneibothrium multiloculatum Carvajal & Dailey, 1975 from Dipturus brevicaudatus (voucher MACN-Pa No. 739). (E) Longitudinal section of bothriudium of Echeneibothrium williamsi Carvajal & Dailey, 1975 from Dipturus brevicaudatus (voucher MACN-Pa No. 743). Abbreviations: lmb, longitudinal muscle bundles; l, loculus; mls, medial longitudinal septum; mmb, marginal muscle bundles; ms, marginal septum; rm, radial muscle; tmb, transverse muscle bundles; ts, transverse septum.