Semiorbiseptum, Franzese & Ivanov, 2020

Franzese, Sebastian & Ivanov, Veronica A., 2020, A new genus of Rhinebothriidea from species of Psammobatis (Rajiformes: Arhynchobatidae) off Argentina, Zootaxa 4803 (2), pp. 355-372 : 357-358

publication ID	https://doi.org/ 10.11646/zootaxa.4803.2.7
publication LSID	lsid:zoobank.org:pub:32379908-BED1-40A3-B77D-D43A8BD5FA33
persistent identifier	https://treatment.plazi.org/id/EC0799C1-96EC-4DF8-932F-2CA0FE2244DD
taxon LSID	lsid:zoobank.org:act:EC0799C1-96EC-4DF8-932F-2CA0FE2244DD
treatment provided by	Plazi
scientific name	Semiorbiseptum
status	gen. nov.

Treatment

Semiorbiseptum gen. nov.

( Figs. 1A View FIGURE 1 , 2–9 View FIGURE 2 View FIGURE 3 View FIGURE 4 View FIGURE 5 View FIGURE 6 View FIGURE 7 View FIGURE 8 View FIGURE 9 )

Type species. Semiorbiseptum mariae sp. nov.

Additional species. Semiorbiseptum alfredoi sp. nov.

Etymology. The name Semiorbiseptum is derived from the Latin “semiorbis”, meaning semicircle, referring to the shape of septa present in the central area of the distal bothridial surface.

Diagnosis. Rhinebothriidea . Worms euapolytic, proglottids craspedote, non-laciniate. Scolex with four bothridia and cephalic peduncle. Bothridia stalked, with clear anterior-posterior orientation, loculate distal bothridial surface with an anterior column of loculi divided by transverse septa, central semicircular septa and posterior loculi divided by transverse and medial longitudinal septa. Transverse, semicircular and longitudinal septa formed distally by transverse muscle bundles with underlying layer of radial muscle, and proximally by radial muscles with proximal end of fibres adjacent to each other, forming a triangular gap. Testes in two columns anterior to cirrus sac, one layer deep in cross-section. Vas deferens enters cirrus sac dorsally, on its proximal half. Genital pores lateral, irregularly alternating. Cirrus covered with spinitriches. Ovary in posterior end of proglottid. Vagina opening anteriorly to cirrus sac into genital atrium. Vitellarium follicular, vitelline follicles in 2 lateral bands. Uterus saccate medioventral. Two pairs of osmoregulatory ducts. Eggs subspherical. Parasites of Psammobatis ( Rajiformes : Arhynchobatidae ).

Remarks. Semiorbiseptum gen. nov. is considered to be a rhinebothriidean by having facially loculated bothridia borne on stalks and cirrus covered with spinitriches ( Figs. 2B,C,F View FIGURE 2 , 3A View FIGURE 3 , 6B,C,E View FIGURE 6 , 7A,B View FIGURE 7 ). It can be distinguished from all other genera in the order by having a particular arrangement of loculi and septa on the distal bothridial surface, i.e. each bothridium is divided into three contiguous regions with a particular pattern of loculation, including unique semicircular septa in the middle region (see graphic summary in Fig. 1 View FIGURE 1 ). Furthermore, Semiorbiseptum gen. nov. differs from Clydonobothrium Euzet, 1959 , Echeneibothrium van Beneden, 1850 , Notomegarhynchus Ivanov & Campbell, 2002 , Phormobothrium Alexander, 1963 , Pseudanthobothrium Baer, 1956 and Tritaphros Lönnberg, 1889 by lacking a myzorhynchus in the adult stage. The new genus can be distinguished from Alveobothrium Boudaya, Neifar & Euzet, 2018 , Anthocephalum Linton, 1890 , Biotobothrium Tan, Zhou & Yang, 2009 , Cairaeanthus Kornyushin & Polyakova, 2012 and Clydonobothrium by the lack of marginal bothridial loculi ( Fig. 1A,C,D,F,G,H View FIGURE 1 ). Whereas the margins of the bothridia are uniform and entire in Semiorbiseptum gen. nov., they are posteriorly bifid in Cairaeanthus and Divaricobothrium Caira, Healy, Marques & Jensen, 2017 ( Fig. 1A,G,J View FIGURE 1 ). Semiorbiseptum gen. nov. differs from Ruptobothrium Coleman, Beveridge, & Campbell, 2019 by lacking separate bothridial lobes ( Fig. 1A,S View FIGURE 1 ). Also, the bothridia are longer than wide in Semiorbiseptum gen. nov., as opposed to the wider than long bothridia in species of Alveobothrium , Barbeaucestus Caira, Healy, Marques & Jensen, 2017 , Escherbothrium Berman & Brooks, 1994 , Phormobothrium and Tritaphros ( Fig. 1A,D,E,L,N,W View FIGURE 1 ). The new genus differs from Biotobothrium , Crassuseptum Eyring, Healy & Reyda, 2012 , Pseudanthobothrium , Scalithrium Ball, Neifar & Euzet, 2003 and Tritaphros by having a conspicuous anterior-posterior orientation of bothridia ( Fig. 1A,F,I,T,W View FIGURE 1 ). In addition, Semiorbiseptum gen. nov. differs from Crassuseptum , Echeneibothrium , Mixobothrium Coleman, Beveridge & Campbell, 2019 and Stillabothrium Healy & Reyda, 2016 by having a cephalic peduncle, and from Spongiobothrium Linton, 1889 and Sungaicestus by lacking seminal receptacle. Finally, Semiorbiseptum gen. nov. can be distinguished from Rhinebothroides by having a symmetrical ovary, and from Anindobothrium , Crassuseptum , Rhabdotobothrium Euzet, 1953 and Rhodobothrium Linton, 1890 by lacking postvaginal testes.