Phoreiobothrium sp.

Marmolejo-Guzman, Linda Yacsiri G., Iv, David, Hern, an G., andez-Mena, Castellanos-Martínez, Sheila & Aguirre-Macedo, M. Leopoldina, 2022, Linking phenotypic to genotypic metacestodes from Octopus maya of the Yucatan Peninsula, International Journal for Parasitology: Parasites and Wildlife 19, pp. 44-55 : 53

4.6. Phoreiobothrium sp.

Individuals of this cestode morphotype species were previously identified as Echeneibothrium sp. (Guill´en-Hern´andez et al., 2018a). Due to the poor morphological development of these plerocercoid larvae, a more detailed morphological characterization was not possible. Plerocercoids at this developmental stage lack visible structures that allow application of relevant taxonomic keys ( Fig. 2P–Q ; Fig. 3F) ( Khalil et al., 1994). Likewise, there was the only specimen found in the entire sampling (n = 60 octopuses); however, this individual has two important characteristics: four quadrangular bothria and one oral sucker. According to Hochberg (1990), there are species of this genus that have been described in approximately 30 species of cephalopods around the world.

When searching for the resulting sequence of the individual found in O. maya , in the BLAST, the results yielded a 100% agreement in identity and coverage with Phoreibothrium sp. which suggests that the individual found in O. maya belongs to this genus. According to Palm and Caira (2008), the larvae of the order Onchoproteocephalidea are different from their adult counterparts since when they change hosts they can develop more complex structures than those presented in their previous host. This suggests that the individual found in O. maya , although morphologically very different from the adult, the results of the comparison in the BLAST in identity and coverage conclude a 100% compatibility.

The genus Phoreibothrium is part of the order Onchoproteocephalidea (Caira et al., 2017) . Currently there are 14 reported species of Phoreibothrium (Caira and Jensen, 2017), of which seven of them are restricted to requiem sharks ( Carcharhinidae ) and five to hammerhead sharks ( Sphyrna ) ( Owens, 2008), all of them present in waters of the Atlantic Ocean, Gulf of Mexico, Pacific Ocean, coasts of Australia, and the Indian Ocean ( Caira and Reyda, 2005). This genus is mainly characterized by the shape of the scolex, which has four bothria, each of them divided into a loculi that contain a pre-hook and a posterior loculi that are separated by a pair of hooks that are often triptych ( Caira and Jensen, 2015). Given the above, it is stated here that the individual found in O. maya belongs to a species of the genus Phoreibothrium .

The phylogenetic analyses showed that the Phoreiobothrium sp. of O. maya were nested without genetic differences with the adult stage of Phoreiobothrium sp. from Opsanus beta in the northern part of the Gulf of Mexico ( Olson et al., 2010). This phylogenetic result can affirm that both specimens belong to the same organism.

Figures

Fig. 2. Schematic drawings and photographs of the stained specimens of cestode parasitizing Octopus maya. Trypanorhyncha (A–D): A- Eutetrarhynchus sp.; B. Kotorella pronosoma; C- Nybelinia sp.; D- Prochristianella sp. Onchoproteocephalidea (E–G): E- Acanthobothrium sp.; F- Phoreiobothrium sp.; G- Prosobothrium sp.- Abbreviations: as = apical sucker; bot = bothridia cc = calcareous corpuscles; lo = loculi; pb = pars bulbosa; pbo = pars bothrialis; ppb = pars postbulbosa; ps = pedunculus scolecis; pv = pars vaginalis; sc = scolex; sp = septa; st = strobilo; vel = velum.