A new species of Amiculucestus (Eucestoda: Lecanicephalidea: Eniochobothriidae) from the cownose ray, Rhinoptera bonasus (Myliobatiformes: Rhinopteridae) in the Western Atlantic.

This study describes, on morphological and molecular grounds, Amiculucestus bonasussp. nov., a parasite of the cownose ray Rhinoptera bonasus from the Western Atlantic. The new species is assigned to Amiculucestus Jensen & Caira, 2022 based on the presence of key diagnostic features such as protandry, presence of an inverted J-shaped cirrus sac, and absence of a seminal receptacle. It can be distinguished from all four other valid species of this genus (i.e., A. calli Jensen & Caira, 2022; A. australiensis Jensen & Caira, 2022; A. herzogae Jensen & Caira, 2022; and A. penghuensis Jensen & Caira, 2022) by the width of the terminal female-mature proglottid, gravid proglottid and ovary, and the combination of other morphometric attributes, such as number of testes, width of the terminal male-mature proglottid and posterior-most immature proglottid, and length of the gravid strobila and ovarian lobe. Phylogenetic analyses of the D1-D3 region of the 28S rDNA gene provide molecular evidence supporting its status as a new species of Amiculucestus. Amiculucestus bonasussp. nov. is the fifth valid species of this genus and the first identified in the Southwestern Atlantic.