The infracommunty or parasites or unromis cyanea (Pisces: Pomacentridae) was studied along the ontogenetic development in the North coast of Havana, Cuba. The objectives were: a- to prove that the core species appears before the strange and stochastic species and they are responsible for the structure in the infracommunity, b- to determine if there is a relationship among the ecological describers of the parasitic infracommunity with the total length. A total of 278 specimens of C. cyanea were captured during the dry season (April) of 2010. The body size range was from 1.5 to 11.5 cm including juvenile and adults. We collected 2 861 parasite specimens belonging to 20 taxa: Crustacea (5), Nematoda (5), Trematoda (4), Cestoda (2), Monogenea (2), Turbellaria (1) and Ciliophora (1). The taxa Tetraphyllidea and Anilocra chromis constituted the core of the parasitic infracommunity. The sequence of appearance and persistence of these taxa during the ontogenetic development, supported the hypothesis of the core species. The changes in the infracommunity, from 6 cm body size, could be the result of an accumulative effect combined with changes of the diet that caused the ingestion of new parasite infective stages. We concluded that the ontogenetic development of C. cyanea constitutes an important variable in the formation of the parasitic infracommunity.