Morphometrical categorization of <i>Phyllobothrium delphini</i> (Cestoidea, Tetraphyllidea) cysts from Fraser's dolphin, <i>Lagenodelphis hosei</i> (Cetacea, Delphinidae)

Abstract

The larvae of phyllobothriid cestode worms found in marine mammals have been classified as either "delphinii group" or "grimaldii group". The first group has been divided into 11 morphotypes by previous studies. However, these categories are vague and often overlap, as they were described from different host species within a wide geographical range. The goal of this study is to simplify the categorization of larval shape and size based on samples obtained from a single host species. Eleven Fraser's dolphin Lagenodelphis hosei Fraser, 1956 stranded on the coast of Uruguay in November 2001 and subsequently died. From these animals, 190 cysts of Phyllobothrium delphini (Bosc, 1802) were obtained from the perigenital blubber of one female and one male. The prevalence of P. delphini was 18.18%, density was 159.38 larvae/kg of perigenital blubber, mean intensity was 95 and mean abundance was 17.27. The following measurements were taken: total length (BL), width and thickness of cysts, neck length (NL), scolex length, scolex width, external diameter of the suckers, and the ratio BL/NL. In order to facilitate further identification of these phyllobothriid cysts, they were grouped into three categories according to shape and size: category "A" (22.35%, neck always straight); category 'B' (62.35%, all with curved neck); category 'C' (15.30%, U-shaped or with projections from the wall of the cyst, also curved neck). These morphological differences could correlate to time spent in the host. One other larval form (Tetrabothrius sp.) was also found in the blubber of these dolphins.