Otobothrium muscatense n. sp. (Trypanorhyncha: Otobothriidae) from Rhabdosargus sarba (Forsskål) (Sparidae), with new locality records of larval trypanorhynchs off the Sultanate of Oman.

In the evaluation of the larval trypanorhynch fauna off the Sultanate of Oman, a total of 188 bony fishes belonging to 16 species were studied, which led to the description of a new species with the establishment of new host and locality records. A new otobothriid species, Otobothrium muscatense n. sp., is described from Rhabdosargus sarba (Forsskål). Based on scolex morphology and tentacular armature, the new species closely resembles the small-sized Otobothrium Linton, 1890 species described as Otobothrium cysticum (Mayer, 1842) and O. crenacolle Linton, 1890. However, it differs from them in the basal armature by a more robust shape of the first principal and the triangular shape of the billhooks as well as by the retractor muscle originating in the posterior part of the tentacle sheath, attaching to a thickening of the tentacle sheath wall, with a muscular branch continuing and attaching at front part of the bulb. It differs from the other species of Otobothrium by size, the combination of six principal hooks and a single intercalary hook in the metabasal armature, and the plane of reflection through the tentacle surfaces. New locality records of the tentaculariids Nybelinia indica Chandra, 1986, Heteronybelinia yamagutii (Dollfus, 1960), Tentacularia coryphaenae Bosc, 1797, and Mixonybelinia lepturi Palm, 2004, together with the lacistorhynchids Pseudogrillotia multiminacantha Palm, 2004 and Callitetrarhynchus gracilis (Rudolphi, 1819), and the pseudotobothriid Parotobothrium balli (Southwell, 1929) off the Muscat region are established. Of the reported species, especially P. multiminacantha and M. lepturi occurring in Trichiurus lepturus L. further demonstrate the relatedness between the Indonesian and the northwestern Indian Ocean fauna, increasing the number of joint records between Indonesia and Omani waters to 14 species.