Co-occurrence of Naobranchia lizae (Copepoda) and Metamicrocotyla macracantha (Monogenea), gill parasites of the striped mullet Mugil cephalus.

The copepod Naobranchia lizae (Kroyer, 1863) and the monogenean Metamicrocotyla macracantha (Alexander, 1954; Koratha, 1955) are gill parasites found on the striped mullet (Mugil cephalus) in the Charleston Harbor Estuarine System (South Carolina, USA). Branchial distribution of each species was studied in mono- and bispecific conditions. No preference for the right or left side of the fish host was observed for either species in either condition. Both species exhibited heterogeneous distribution among the gill arches, with a preference for arch I. N. lizae exhibited intraspecific competition and a saturation threshold in both mono- and bispecific conditions. A shift in niche toward the posterior arches was observed for M. macracantha only in bispecific infection. Interspecific competition was detected exclusively on the posterior arches, where M. macracantha seemed out-competed by N. lizae. The data indicated that both neutral and negative interactions played a role in determining the distribution of N. lizae and M. macracantha individuals on the gill arches of M. cephalus.