Modularity in attachment organs of African Cichlidogyrus (Platyhelminthes: Monogenea: Ancyrocephalidae) reflects phylogeny rather than host specificity or geographic distribution

Abstract

Cichlidogyrus spp. (Monogenea, Ancyrocephalidae) are common parasites of cichlid fishes from Africa and the Levant. They display important morphological variation in their attachment apparatus and infect a broad host spectrum throughout a wide geographic range. Thus, they offer an interesting model to investigate to what extent the phenotypic variability of the attachment organ among congeners is related to host specificity, geographic/ environmental components, or phylogeny. A geometric morphometric approach was carried out to analyse the shape variation of sclerotized structures of the attachment organ within 66 African species of the genus Cichlidogyrus. The interspecific shape comparison supports the presence of three main morphological configurations, each consisting of a given combination of particular sclerite shapes. Moreover, data emphasize strong coordination and integration (shape co-variation) among the different sclerites jointly forming the attachment organ. Although attachment apparatuses are usually considered to be the result of adaptive processes and must be adapted to the hosts and local environmental conditions, we found no relationship between these clusters and host specificity or geographical distribution. Nevertheless, groups are partially congruent with those obtained with the molecular phylogeny of a subset of species, suggesting a phylogenetic constraint rather than an adaptation to either hosts or environment. Because of the necessity to form a functional entity, modularity within attachment organ imposes important evolutionary constraint. This provides new insights into the evolvability of attachment organs, as well as into the morphological basis of host specificity and host-parasite co-evolutionary interaction in helminth parasites.

Ancyrocephalidae (Monogenea) of Lake Tanganyika: I: Four new species of Cichlidogyrus from Ophthalmotilapia ventralis (Teleostei: Cichlidae), the first record of this parasite family in the basin

“…3). The 71 species of Cichlidogyrus presently described from Africa and the Levant can be clustered in four morphological groups, according to the length of their uncinuli (POUYAUD et al 2006, PARISELLE & EUZET 2009, VIGNON et al 2011. Cichlidogyrus vandekerkhovei sp.…”

“…However, despite the great number of studies on Cichlidae of Lake Tanganyika, studies on their parasite fauna, especially on their monogenean flatworms, are practically inexistent as in many tropical biomes throughout the world (WHITTINGTON 1998, BAKKE et al 2002, HUYSE et al 2006, VANHOVE et al 2011). However, monogeneans are known to depict a considerable biological diversity -the average number of species per host is more than six in West Africa (PARISELLE et al 2003b) -and they usually depict high host specificity, parasitizing a single or few closely related host species.…”

Phenotypic plasticity in haptoral structures of Ligophorus cephali (Monogenea: Dactylogyridae) on the flathead mullet (Mugil cephalus): a geometric morphometric approach

“…The shape changes modelled onto a TPS can be separated into two parts, the uniform and non-uniform components (Rohlf and Slice, 1990). The former (U1 and U2) express global variations in shape, whereas the latter describe local shape changes at different geometric scales (Vignon et al, 2011). To visualize localized anchor shape differences, TPS deformation grids and grey-scaled coded Jacobian expansion factors, which measure the degree of local expansion or contraction of the grid (black for factors >1, indicating expansion; grey for factors between 0 and 1, indicating contraction) were used (Bookstein, 1993;Viscosi and Cardini, 2011).…”

“…This coordination among parts of the haptor could be due to host specificity and the attachment mechanism (Vignon et al, 2011). Klingenberg (2008) suggested that this kind of morphological covariationcan be a substantial player determining the evolutionary potential of traits within populations.…”

“…Many monogeneans are characterized as being highly specific, restricted to certain gill arches and certain parts of gill filaments, and having developed different strategies in adapting to this microhabitat (Whittington and Kearn, 1991;Vignon et al, 2011). This adaptive process suggests that the high morphological variability of attachment organs in monogeneans is possibly linked to host specificity .…”