The relationship between Lobatostoma hanumanthai and L. kemostoma (Trematoda: Aspidogastridae) parasitological indexes and the ontogenetic diet variation of Trachinotus marginatus from the Rio Grande do Sul coast, Brazil

Abstract

The prevalence, mean intensity of infection and mean abundance of the parasites Lobatostoma hanumanthai and L. kemostoma (Aspidogastrea) in 100 individuals of Trachinotus marginatus from the Rio Grande do Sul coast were used to investigate the existence of a relationship between the parasitological indexes (PI) and the ontogenetic diet variation of the host. Clusters analyses and the "K-means†algorithm were used and show that six host length classes dendrograms produce the same results as previously established for smaller length fish. Other limits are obtained for larger fish when Lobatostoma PI are used as criterion. The absence of Lobatostoma may be related to the fact that the pharyngeal teeth are not fully formed in the smallest fishes. Therefore, the smallest fishes are inapt to the mollusks consumption. Variations in the PI of the two Lobatostoma species can also be connected to ontogenetic variations in the fish diet.