Semiorbiseptum alfredoi Franzese & Ivanov 2020, sp. nov.
Creators: name: Franzese, Sebastian
name: Ivanov, Veronica A.
Publisher: name: Zenodo
Year: 2020
Subjects: Biodiversity
Taxonomy
Animalia
Chordata
Chondrichthyes
Rajiformes
Arhynchobatidae
Semiorbiseptum
Semiorbiseptum alfredoi

description: Semiorbiseptum alfredoi sp. nov.   
 ( Figs. 6–9)   
 Type host. Psammobatis normani McEachran, shortfin sand skate (Rajiformes: Arhynchobatidae).   
 Type locality. Coastal waters off Mar de Ajó, Buenos Aires Province (36°34’S, 54°39’W).   
 Additional locality. Coastal waters off Pinamar, Buenos Aires Province (37°12’S, 54°53’W) and off Caleta Olivia, Santa Cruz Province (46°23’S, 64°20’W).   
 Site of infection. Spiral intestine.   
 Type material. Holotype MACN-Pa 706 (entire worm), 12 paratypes MACN-Pa 707/1–5, 708/1–3, 709, 710, 711/1–2 (9 entire worms, histological sections of 1 mature proglottid, histological sections of 2 scoleces); 4 paratypes IPCAS C-837 /1 (4 entire worms).   
 Prevalence of infection. 50% (5 hosts infected out of 10 examined).   
 Etymology. This species is named in memory of Alfredo Marino Franzese, the first author’s father.   
 Description. Based on 24 specimens prepared as follows: whole mounts of 14 entire worms, serial sections of 1 mature proglottid and 2 scoleces, 7 worms examined with SEM. Worms euapolytic, 5.37–26.81 mm (13.03 mm ± 6.67 mm, 13) long, 420–705 (495 ± 95, 7) wide, maximum width at level of scolex. Proglottids craspedote, 85–187 (143 ± 32, 11) per worm, 84–172 (137 ± 29, 8) immature proglottids, 1–4 (3 ± 1, 8) mature proglottids (Fig. 6A). Scolex 710–1,435 (1059 ± 278, 10) long, composed of 4 stalked bothridia and cephalic peduncle; myzorhynchus absent in adult stage (Figs. 6A,B, 7A). Bothridia facially loculate, 280–445 (363 ± 117, 2) long, 230–360 (267 ± 39, 12) wide. Total number of loculi 13–16 (14 ± 1, 16) (Figs. 6C, 7B). Anterior region of bothridia divided by transverse septa in 4–5 (5 ± 0.4, 19) loculi arranged in a single column, central region divided in 2–3 (2 ± 0.24, 17) loculi delimited by 2–3 semicircular septa with convex surface facing anteriorly, and posterior region divided by transverse septa in 0–3 (2 ± 1, 17) loculi arranged in a single column, followed by 1–4 pairs of loculi delimited by transverse and medial longitudinal septa, arranged in 2 columns, ending in single posteriormost loculus. In some specimens, semicircular septa extend posteriorly, reaching first loculus of posterior part of botridium. Anteriormost loculus 28–55 (40 ± 8, 13) long, 35–83 (54 ± 13, 13) wide, muscular wall 8–10 (9 ± 1, 8) thick. Posteriormost loculus 20–33 (28 ± 4, 9) long, 20–48 (30 ± 9, 9) wide, muscular wall 5–10 (7 ± 2, 8) thick. Transverse, semicircular and longitudinal septa formed distally by transverse muscle bundles with underlying layer of radial muscle, proximal portion formed by radial muscles with proximal fibres ending adjacent to each other, forming triangular gap (Fig. 8). Bothridial stalks 70–150 (104 ± 27, 6) long, 78–98 (88 ± 8, 6) wide, attached to centre of bothridium. Cephalic peduncle 450–1,068 (779 ± 211, 12) long, 88–135 (109 ± 15, 12) wide at posterior end. Apex of scolex covered with acicular to capilliform filitriches. Proximal bothridial surface with acicular filitriches along most of its length, posterior portion also with small gladiate spinitriches (Fig. 7E); proximal bothridial edge covered with acicular filitriches (Fig. 7D). Distal bothridial surface with coniform spinitriches and acicular filitriches (Fig. 7C). Bothridial stalks and cephalic peduncle covered with acicular to capilliform filitriches (Fig. 7F,G).   
Immature proglottids initially wider than long, becoming longer than wide with maturity. Mature proglottids (excluding terminal proglottid) longer than wide, 353–818 (573 ± 227, 6) long (velum not included in proglottid length), 295–355 (323 ± 26, 6) wide, velum 38–63 (50 ± 10, 6) long, covering 4–8% (6 ± 1, 6) of adjacent proglottid. Terminal mature proglottid 575–1,060 (824 ± 159, 13) long, 183–310 (277 ± 35, 13) wide, length to width ratio 1: 2–6 (3 ± 1, 11) (Fig. 6D). Mature proglottids covered by capilliform filitriches (Fig. 7H). Testes oval, 22–33 (26 ± 3, 9) per proglottid, 18–50 (33 ± 8, 8, 40) long, 32–73 (54 ± 10, 8, 40) wide, arranged in 2 columns, anterior to cirrus sac (Fig. 6D), 1 layer deep in cross-section (Fig. 9A). Cirrus sac oval to pyriform, 91–140 (125 ± 19, 5) long, 58–78 (69 ± 8, 5) wide, containing coiled cirrus covered with spinitriches; vas deferens dorsal, highly coiled, entering dorsally at proximal half of cirrus sac (Figs. 6D,E, 9C). Genital pores marginal, 33–60% (44 ± 8, 10) of proglottid length from posterior end. Vagina thick-walled, surrounded by darkly stained cells distally, extending from oötype along midline of proglottid to anterior margin of cirrus sac, then laterally along anterior margin of cirrus sac to common genital atrium; vaginal sphincter absent (Figs. 6D,E, 9B). Ovary near posterior end of proglottid, Hshaped in dorsoventral view (Fig. 6D,F), symmetric, tetralobed in cross-section (Fig. 9D), 118–188 (150 ± 22, 8, 16) long, 78–163 (137 ± 32, 6) wide at ovarian isthmus. Mehlis’ gland posterior to ovarian isthmus, 38–55 (46 ± 8, 5) in diameter (Fig. 6F). Vitelline follicles 10–22 (16 ± 3, 6, 30) long, 15–35 (25 ± 4, 6, 30) wide, in 1 dorsal and 1 ventral column on each lateral margin of proglottid, extending along entire proglottid, interrupted by vagina and cirrus sac ventrally (Figs. 6D,E, 9B). Uterus sacciform, occupying midline of proglottid, from level of ovarian isthmus to near anterior margin of proglottid (Fig. 6D). Two pairs of osmoregulatory ducts, 1 dorsal, 1 ventral.  
 Remarks. Semiorbiseptum alfredoi sp. nov. can be mainly distinguished from Se. mariae in the number of facial loculi, especially in the anterior region of bothridia. Whereas Se. alfredoi sp. nov. has bothridia divided in 13–16 loculi, with 4–5 loculi in the anterior region, Se. mariae has bothridia divided in 19–23 loculi, with 7–10 loculi in the anterior region (Figs. 2C, 6C). The microthrix pattern also differed between the two species. Filitriches on the proximal bothridial surface of Se. mariae are longer than in Se. alfredoi sp. nov. Gladiate spinitriches are densely arranged along the entire proximal bothridial surface in Se. mariae, whereas they are scattered and restricted to the posterior region of bothridia in Se. alfredoi sp. nov. (Figs. 3D, 7E).
description: Published as part of Franzese, Sebastian & Ivanov, Veronica A., 2020, A new genus of Rhinebothriidea from species of Psammobatis (Rajiformes: Arhynchobatidae) off Argentina, pp. 355-372 in Zootaxa 4803 (2) on pages 363-367, DOI: 10.11646/zootaxa.4803.2.7, http://zenodo.org/record/3909195