Semiorbiseptum mariae 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 mariae

description: Semiorbiseptum mariae sp. nov.   
 ( Figs. 2–5)   
 Type host. Psammobatis rudis Günther, smallthorn sand skate (Rajiformes: Arhynchobatidae).   
 Additional host. Psammobatis normani McEachran, shortfin sand skate (Rajiformes: Arhynchobatidae).   
 Type locality. Coastal waters off Isla de los Estados, Tierra del Fuego Province (54°30’S, 65°13’W).   
 Additional locality. Coastal waters off Rio Grande, Tierra del Fuego Province (53°34’ S, 66°32’W) and off Miramar, Buenos Aires Province (39°34’S, 56°16’W).   
 Site of infection. Spiral intestine.   
 Type material. Type material. Holotype MACN-Pa 701 (entire worm), 21 paratypes MACN-Pa 702/1–4, 703, 704/1–13, 705 (12 entire worms, 6 detached gravid proglottids, histological sections of 1 mature proglottid, histological sections of 2 scoleces); 8 paratypes IPCAS C-836 /1 (6 entire worms and 2 detached gravid proglottids).   
 Prevalence of infection. 78% (7 hosts infected out of 9 examined) in P. rudis and 20% (2 hosts infected out of 10 examined) in P. normani.   
 Etymology. This species is named after María Rosa Labonia, the first author’s mother.   
 Description. Based on 31 specimens prepared as follows: whole mounts of 19 entire worms and 8 detached gravid proglottids, serial sections of 1 mature proglottid and 2 scoleces, 9 worms examined with SEM. Worms euapolytic, 4.17–11.17 mm (8.39 mm ± 1.65 mm, 14) long, 420–1,020 (763 ± 204, 12) wide, maximum width at level of scolex. Proglottids craspedote, 71–104 (91 ± 9, 13) per worm, 70–103 (89 ± 8, 13) immature proglottids, 1–3 (1 ± 1, 13) mature proglottids (Fig. 2A). Scolex 530–1,910 (868 ± 369, 15) long, composed of 4 stalked bothridia and cephalic peduncle; myzorhynchus absent in adult stage (Figs. 2A,B, 3A). Bothridia facially loculate, 395–550 (463 ± 61, 5) long, 168–355 (254 ± 50, 15) wide. Total number of loculi 19–23 (21 ± 1, 15) (Fig. 2C). Anterior region of bothridia divided by transverse septa in 7–10 (8 ± 1, 25) loculi arranged in a single column, central region divided in 2–3 (2 ± 0.4, 19) loculi delimited by 2–3 semicircular septa with convex surface facing anteriorly, and posterior region divided by transverse septa in 3–6 (4 ± 1, 15) loculi arranged in a single column, followed by 1–3 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 bothridium. Anteriormost loculus 35–73 (47 ± 10, 15) long, 45–123 (79 ± 21, 15) wide, muscular wall 5–8 (7 ± 1, 6) thick. Posteriormost loculus 20–43 (35 ± 8, 6) long, 28–60 (49 ± 12, 6) wide, muscular wall 5–8 (6 ± 1, 6) 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. 4). Bothridial stalks 110–250 (182 ± 49, 11) long, 68–125 (100 ± 18, 11) wide, attached to centre of bothridium. Cephalic peduncle 163–915 (418 ± 218, 12) long, 73–145 (116 ± 22, 12) wide at posterior end. Apex of scolex covered with capilliform filitriches (Fig. 3E). Proximal bothridial surface with gladiate spinitriches interspersed with capilliform filitriches (Fig. 3D) and acicular filitriches on the edge (Fig. 3C). Distal bothridial surface covered by coniform spinitriches interspersed with acicular filitriches (Fig. 3B). Bothridial stalks and cephalic peduncle with capilliform filitriches (Fig. 3F,G).   
Immature proglottids initially wider than long, becoming longer than wide with maturity. Mature proglottids (excluding terminal proglottid) longer than wide, 420–570 (494 ± 55, 5) long (velum not included in proglottid length), 250–325 (276 ± 35, 5) wide, velum 35–65 (51 ± 11, 5) long, covering 5–7% (6 ± 1, 5) of adjacent proglottid. Terminal mature proglottid 550–950 (761 ± 113, 18) long, 183–295 (244 ± 31, 18) wide, length to width ratio 1: 2–4 (3 ± 0.3, 18) (Fig. 2D). Mature proglottids covered by capilliform filitriches (Fig. 3H). Testes oval, 20–32 (24 ± 3, 12) per proglottid, 20–50 (33 ± 7, 12, 60) long, 38–65 (52 ± 6, 12, 60) wide, arranged in 2 columns, anterior to cirrus sac (Fig. 2D), 1 layer deep in cross-section (Fig. 5A). Cirrus sac oval to pyriform, 86–145 (109 ± 20, 8) long, 48–75 (61 ± 9, 8) wide, containing coiled cirrus covered with spinitriches; vas deferens dorsal, highly coiled, entering dorsally at proximal half of cirrus sac (Figs. 2D,F, 5C). Genital pores marginal, 36–47% (40 ± 3, 14) 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. 2D,F, 5B). Ovary near posterior end of proglottid, H-shaped in dorsoventral view (Fig. 2D,E), symmetric, tetralobed in cross-section (Fig. 5D), 85–260 (160 ± 41, 11, 22) long, 75–125 (100 ± 17, 8) wide at ovarian isthmus. Mehlis’ gland posterior to ovarian isthmus, 30–43 (36 ± 6, 4) in diameter (Fig. 2E). Vitelline follicles 10–23 (13 ± 3, 10, 50) long, 14–35 (21 ± 5, 10, 50) 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. 2D,F, 5B). Uterus sacciform, occupying midline of proglottid, from level of ovarian isthmus to near anterior margin of proglottid (Fig. 2D). Two pairs of osmoregulatory ducts, 1 dorsal, 1 ventral. Detached gravid proglottids 1.53– 2.11 mm (2 mm ± 0.2 mm, 8) long, 300–450 (371 ± 59, 8) wide. Unembryonated eggs subspherical, 28–38 (31 ± 3, 4, 20) long, 20–28 (23 ± 2, 4, 20) wide (Fig. 2G).
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 358-362, DOI: 10.11646/zootaxa.4803.2.7, http://zenodo.org/record/3909195