A phylogeny of Cichlidogyrus spp. (Monogenea, Dactylogyridea) clarifies a host-switch between fish families and reveals an adaptive component to attachment organ morphology of this parasite genus
© Messu Mandeng et al. 2015
Received: 18 May 2015
Accepted: 29 October 2015
Published: 10 November 2015
Parasite switches to new host species are of fundamental scientific interest and may be considered an important speciation mechanism. For numerous monogenean fish parasites, infecting different hosts is associated with morphological adaptations, in particular of the attachment organ (haptor). However, haptoral morphology in Cichlidogyrus spp. (Monogenea, Dactylogyridea), parasites of African cichlids, has been mainly linked to phylogenetic rather than to host constraints. Here we determined the position of Cichlidogyrus amieti, a parasite of species of Aphyosemion (Cyprinodontiformes, Nothobranchiidae) in the phylogeny of its congeners in order to infer its origin and assess the morphological changes associated with host-switching events.
The DNA of specimens of C. amieti isolated from Aphyosemion cameronense in Cameroon was sequenced and analyzed together with that of Cichlidogyrus spp. from cichlid hosts. In order to highlight the influence of the lateral transfer of C. amieti on the haptoral sclerotised parts we performed a Principal Component Analysis (PCA) to compare the attachment organ structure of C. amieti to that of congeners infecting cichlids.
Cichlidogyrus amieti was found to be nested within a strongly supported clade of species described from Hemichromis spp. (i.e. C. longicirrus and C. dracolemma). This clade is located at a derived position of the tree, suggesting that C. amieti transferred from cichlids to Cyprinodontiformes and not inversely. The morphological similarity between features of their copulatory organs suggested that C. amieti shares a recent ancestor with C. dracolemma. It also indicates that in this case, these organs do not seem subjected to strong divergent selection pressure. On the other hand, there are substantial differences in haptoral morphology between C. amieti and all of its closely related congeners described from Hemichromis spp..
Our study provides new evidence supporting the hypothesis of the adaptive nature of haptor morphology. It demonstrates this adaptive component for the first time within Cichlidogyrus, the attachment organs of which were usually considered to be mainly phylogenetically constrained.
KeywordsPhylogeny Lateral transfer Cichlidogyrus amieti Aphyosemion Nothobranchiidae Cichlidae Cameroon Africa
Teleost fishes of the order Cyprinodontiformes, commonly called cyprinodonts, or rivulines, livebearers and killifishes [1–3], are well known ornamental fishes. American representatives like xiphos (Xiphophorus Heckel, 1848) and guppies (Poecilia Bloch & Schneider, 1801) have been adopted as model species featuring in an increasing number of laboratory studies [4–6]. This is also the case for some African representatives, such as species belonging to Nothobranchius Peters, 1868 [7–10]. They are also established models in ecology and evolutionary biology [11–16] and parasitology [17, 18]. Evolutionary-parasitological research on these fishes often deals with monogeneans, a species-rich clade of mostly ectoparasitic flatworms. Fish-monogenean systems are established models to study the evolution of host-parasite interactions (e.g. [19, 20]). A diverse fauna of gyrodactylid monogeneans has been described from cyprinodontiform hosts in both the Neotropics  and Africa . The first dactylogyridean monogenean parasites from African cyprinodonts were described by Birgi and Euzet  on the gills of some species of Aphyosemion Myers, 1924 sampled in different localities [Kala, Zamakoe and Yaoundé (Central Region)] in Cameroon. Members of this fish genus in general inhabit narrow, shallow and slowly-flowing forest streams [3, 24]. One of these killifish monogenean species, Cichlidogyrus amieti Birgi & Euzet , was isolated from the gills of Aphyosemion cameronense (Boulenger, 1903) and Aphyosemion obscurum (Ahl, 1924), two related species . This discovery raised questions regarding the specificity of species belonging to Cichlidogyrus Paperna . Indeed, no representative of Cichlidogyrus had, at that time, ever been collected from a fish not belonging to Cichlidae . Birgi and Euzet  therefore hypothesized that the presence of C. amieti on the above mentioned two African cyprinodonts was probably the result of a lateral transfer from cichlid fishes. Switches to new host species represent a substantial risk to, e.g., aquaculture and fisheries [27, 28]. They are also of fundamental scientific interest , e.g. in understanding disease transmission , host biogeography [30, 31] and the relationship between niche specialization and host range . Several analyses on phylogeny and evolution of host specificity of the monogenean gill parasites of African cichlids have been conducted [33–36]. However, congeners infecting non‐cichlids such as Cichlidogyrus amieti have not yet been included in these analyses. Hence the aspect of host-switching over larger phylogenetic distances was not looked into. Moreover, Pariselle et al. [19, 31] raised the question of the origin of Cichlidogyrus spp. described from cichlid hosts in Africa. Based on fossil, genetic and parasitic evidence, the authors hypothesized that cichlids may have originated from Madagascar [37, 38] after the Gondwanan split and subsequently dispersed over Africa, Central and South America, India and the Middle East across various marine pathways [31, 38–40]. In this case, these teleosts would have encountered salinities that resulted in the loss of their ectoparasitic monogeneans (probably representatives of Malagasy Insulacleidus Rakotofiringa & Euzet  or one of their ancestors) which show a poor tolerance to salinity and osmotic variations . It is then likely that cichlids, after reaching the African continent, have been newly colonized by an ancestor species of Cichlidogyrus, presumably transferred from a currently unspecified African fish. From there, the ancestor of Cichlidogyrus evolved and specialized on members of Cichlidae , and became host-specific (i.e. oioxenous ). As C. amieti is known to infect representatives of Cyprinodontiformes, it could be possible that these fish represent the origin of the first host-switch to cichlids from which the present-day species-rich assemblage of Cichlidogyrus spp. on old world cichlids arose. Indeed, similar radiation episodes following a switch to a new host family have been identified in monogeneans, for example in Gyrodactylus . In gyrodactylids, host-switching is even considered an important speciation mechanism . It has been suggested for a range of monogeneans that colonization of different hosts is associated with morphological adaptations, in particular to the attachment organ ( and references therein). However, morphological analysis linked the structure of haptoral hard parts in Cichlidogyrus to phylogenetic rather than to host-related constraints . Parasites belonging to Cichlidogyrus infecting non-cichlid hosts have never been taken into account in this context. Therefore, the influence of phylogenetically distant host-switches on haptoral morphology and speciation of Cichlidogyrus remains to be tested.
This paper therefore aims at determining the position of C. amieti in the phylogenetic tree of Cichlidogyrus spp. using molecular analyses. This will allow testing whether the putative switch between cyprinodonts and cichlids happened early in the history of Cichlidogyrus, seeding its radiation, or whether it rather represents a more recent event. If C. amieti is phylogenetically close to the species that first host-switched onto a cichlid, it should be situated close to the root of the tree of Cichlidogyrus spp. If C. amieti (or its ancestor) originated from a lateral transfer from a cichlid species, it should be closely related to a species of Cichlidogyrus found on that cichlid.
Determining the origin of C. amieti will also allow us to compare it morphologically to its closely related congeners, hence assessing the changes associated with a host-switch between fish families.
Sample collection and PCR amplification
Specimens of Aphyosemion spp. from some forest streams of the central and southern plateau and the littoral plain of Cameroon were caught using a dipnet of 2 mm x 2 mm mesh size, and immediately transferred into an empty container for freezing or into 96° alcohol for fixation and conservation. In the laboratory, fishes were dissected; gills from both sides were removed, placed in glass Petri dishes and examined under a Wild dissecting microscope. Fish identifications were done following Amiet  and Sonnenberg . The studied specimens of Cichlidogyrus amieti were collected from the gills of A. obscurum captured in the locality of Mbalelon (03°33’54”N, 011°22’07”E, 695 m), A. cameronense from the localities of Oman II (03°37’45”N, 011°27’40”E, 720 m), Nkol Ngbwa (02°56’53”N, 011°50’07”E, 693 m) and Nkong (03°32’58”N, 011°25’00”E, 700 m) and A. exiguum from Nkong. They were individually placed in-between slide and coverslip, in a drop of water and examined under a Leica DM2500 microscope equipped with a LEICA DFC425 video camera. Parasite identification was performed using the morphology and size of sclerotized parts of the attachment apparatus (haptor) and that of the genitalia (vagina and male copulatory organs) following the original description of Birgi and Euzet . While some individuals were fixed and mounted in a mixture of glycerin and ammonium picrate  for further morphological study, three adult specimens (fixed alive together with the host and preserved in alcohol) were prepared for PCR amplification following the protocol of Marchiori et al. , i.e., directly without DNA extraction. Standard PCR was performed with two primers specific to the D1-D2 domain of the large subunit region (LSU) of the 28S ribosomal gene: C1 (forward; 5’-ACCCGCTGAATTTAAGCAT-3’) and D2 (reverse; 5’-TGGTCCGTGTTTCAAGAC-3’) . The amplification protocol began with 2 min at 93 °C for initial denaturation followed by 40 cycles of 30 s at 93 °C, 30 s at 56 °C for annealing, 1 min 30 s at 72 °C for extension, with a final 5 min extension step at 72 °C. The different reagents’ final concentrations were as follows: GoTaq Flexibuffer (Promega) 1x, MgCl2 2.5 mM, PCR nucleotide mix, 0.2 nM of each DNTP, forward and reverse primers 1 μM each, GoTaq (Promega) DNA polymerase 2 U, template DNA 0.2 μg (between 1.6and 3 μl depending on the DNA extract concentration), nuclease-free water to 20 μl. Sequencing was performed using the same primers as in initial PCR amplification: C1 and D2. Purification was performed with an Agencourt® AMPure® PCR purification kit following the manufacturer’s recommendations.
List of monogenean species used in this study including their host species and accession numbers for the LSU 28S rDNA sequences
GenBank Accession Number
Cichlidogyrus aegypticus Ergens, 1981 
Tilapia guineensis (Günther, 1862)
Cichlidogyrus amieti Birgi & Euzet, 1983 
Aphyosemion cameronense (Boulenger, 1903)
Cichlidogyrus amphoratus Pariselle & Euzet, 1996 
Tilapia guineensis (Bleeker, 1862)
Cichlidogyrus arthracanthus Paperna, 1960 
Tilapia guineensis (Günther, 1862)
Cichlidogyrus cirratus Paperna, 1964 
Oreochromis niloticus (Linnaeus, 1758)
Cichlidogyrus cubitus Dossou, 1982 
Tilapia guineensis (Günther, 1862)
Cichlidogyrus digitatus Dossou, 1982 
Tilapia guineensis (Günther, 1862)
Cichlidogyrus douellouae Pariselle, Bilong & Euzet, 2003 
Sarotherodon galilaeus (Linnaeus, 1758)
Cichlidogyrus dracolemma Řehulková, Mendlová & Šimková, 2013 
Hemichromis letourneuxi Sauvage, 1880
Cichlidogyrus ergensi Dossou, 1982 
Tilapia guineensis (Günther, 1862)
Cichlidogyrus falcifer Dossou & Birgi, 1984 
Hemichromis fasciatus Peters, 1857
Cichlidogyrus halli (Price & Kirk, 1967) 
Sarotherodon galilaeus (Linnaeus, 1758)
Cichlidogyrus longicirrus Paperna, 1965 
Hemichromis fasciatus Peters, 1857
Cichlidogyrus njinei Pariselle, Bilong Bilong & Euzet, 2003 
Sarotherodon galilaeus (Linnaeus, 1758)
Cichlidogyrus pouyaudi Pariselle & Euzet, 1994 
Tylochromis intermedius (Boulenger, 1916)
Cichlidogyrus sclerosus Paperna & Thurston, 1969 
Oreochromis niloticus (Linnaeus, 1758)
Cichlidogyrus tiberianus Paperna, 1960 
Tilapia guineensis (Bleeker, 1862)
Cichlidogyrus yanni Pariselle & Euzet, 1996 
Tilapia guineensis (Bleeker, 1862)
Haliotrema cromileptis Young, 1968 
Epinephelus coioides (Hamilton, 1822)
Haliotrema johnstoni Bychowsky & Nagibina, 1970 
Upeneus luzonius Jordan & Seale, 1907
Ligophorus chabaudi Euzet & Suriano, 1977 
Mugil cephalus Linnaeus, 1758
Ligophorus cephali Rubtsova et al., 2006 
Mugil cephalus Linnaeus, 1758
Thaparocleidus asoti (Yamaguti, 1937 )
Parasilurus asotus (Linnaeus, 1758)
Siganus fuscescens (Houttuyn, 1782)
Principal Component Analysis (PCA)
A PCA, using Statistica 9, was performed with “standardised” measurements to avoid morphometrical differences possibly due to developmental stage of the examined parasite or the influence of temperature on the size of the sclerites [55, 56]: i.e. the length of all sclerotized haptoral parts were divided by that of uncinuli pair II (= pair V sensu Mizelle ), which is supposed to keep its larval size (see ). The following characters were used in this analysis: total length of uncinuli I [I], III [VI], IV [VII], V [IV], VI [III], VII [II]; dorsal transverse bar: total length, maximum width, distance between auricles and auricle length; ventral transverse bar: branch total length and maximum width; total length of (ventral and dorsal) anchor, and the length of their blade, shaft, guard and point. Ten specimens of each of the following species of Cichlidogyrus were considered: C. cf. bychowskii (Markevich ) (see remark below) collected on the gills of an Hemichromis bimaculatus Gill, 1862 (MRAC 74155-63 voucher specimen) from the Congo River at Bokalakala (2°08'00"S, 16°22'00"E) in the Democratic Republic of Congo; C. euzeti Dossou & Birgi  and C. longicirrus Paperna  on H. cf. elongatus from a small stream near Idenao (4°13’24”N, 8°59’18”E) (both) and Soo River on the road between Abang and Adjap (3°19’21”N, 11°28’55”E) and Ossa Lake near Dizangué (3°46’43”N, 10°00’02”E) (respectively) in Cameroon; C. falcifer Dossou & Birgi  on H. fasciatus Peters, 1852 from Banjul on the Casamance River in the Gambia (13°26’51”N, 16°35’09”W); C. sanseoi Pariselle & Euzet  and C. teugelsi Pariselle & Euzet  both on H. fasciatus from a small stream near Kounoukou (4°49'37"N, 6°24'04"W) (misspelled Kounougou in the original description) in Ivory Coast. The voucher specimen of C. amieti we deposited in the invertebrate collection of the Royal Museum for Central Africa (Tervuren, Belgium) (MRAC 37784, host: A. cameronense, locality: Nkol Ngbwa) was used for supplementary observations.
Fish were handled in respect with the Cameroon National Ethical Committee Reg. Num. FWAIRD 0001954.
Paperna  found and re-described on Hemichromis bimaculatus in southern Ghana, a species of Cichlidogyrus he named C. bychowskii only based on haptoral sclerotized parts morphology. Due to the fact that this was the only species already described on this cichlid, that Paperna did not know the morphology of its copulatory organ (no drawing in the original description and description done in Russian ), that the haptoral sclerotized parts are quite similar in all Cichlidogyrus spp. from hosts belonging to Hemichromis, and according to Řehulková et al. , we think that Paperna  confused the species of Cichlidogyrus living in Africa (Ghana) on H. bimaculatus with C. bychowskii described from a dead fish from the Leningrad aquarium . The latter parasite, which possesses a spirally coiled copulatory organ , has never been recovered from H. bimaculatus nor on the closely related H. letourneuxi in the wild in Africa. Then we consider that either Markevich’ identification of the host was wrong, or the parasite he described was laterally transferred from another cichlid host present in that aquarium. Consequently, C. bychowskii, of which neither type nor voucher specimens have been deposited in any museum, should be considered as a numen nudum. In this study the parasite species collected from H. bimaculatus, although morphologically related to C. dracolemma Řehulková et al., , does not necessarily belong to the latter parasite species which was described from H. letourneuxi. Pending genetic comparison, we therefore used C. cf. bychowskii to designate the parasites we collected from H. bimaculatus from the Congo River basin.
Eleven species of Aphyosemion Myers, 1924 (Cyprinodontiformes, Nothobranchiidae) were captured: Aphyosemion loennbergii (Boulenger, 1903) (266 specimens), A. koungueense (Sonnenberg, 2007) (5 specimens), A. omega (Sonnenberg, 2007) (85 specimens), A. riggenbachi (Ahl, 1924) (18 specimens), A. ahli Myers, 1933 (86 specimens), A. raddai Scheel, 1975 (83 specimens), A. exiguum (Boulenger, 1911) (100 specimens), A. amoenum Radda & Pürzl, 1976 (71 specimens), A. obscurum (46 specimens), A. cameronense (133 specimens) and A. batesii (Boulenger, 1911) (61 specimens). The parasite Cichlidogyrus amieti was recovered from the gills of only three of them: A. obscurum captured in the locality of Mbalelon (2 worms), A. cameronense from the localities of Oman II (2 worms) and Nkol Ngbwa (23 worms), and A. exiguum from Nkong (3 worms). This is the first record of C. amieti on A. exiguum.
A 827 base pair alignment for the 28S rDNA region of the nuclear genome was obtained after trimming the ends of each sequence. The three newly sequenced specimens of C. amieti have the same haplotype (GenBank accession number KT945076). This unique sequence was then aligned and compared to 17 other Cichlidogyrus sequences available in GenBank (Table 1). Sequences from other dactylogyridean representatives, namely Tetrancistrum sp., Haliotrema cromileptis Young , H. johnstoni Bychowsky & Nagibina , Ligophorus chabaudi Euzet & Suriano , L. cephali Rubtsova et al.  and Thaparocleidus asoti (Yamaguti ) (Table 1), were used to root the tree.
Relative to the outgroup taxa, all the species of Cichlidogyrus appeared grouped in a monophyletic assemblage supported by high bootstrap values (100, 86 and 99 % for ME, MP and ML respectively). Cichlidogyrus pouyaudi Pariselle & Euzet  occupied a basal position in this group (bootstrap values, 75, 71 and 67 %) being the sister species of all the other species of Cichlidogyrus as already observed by Mendlová et al. .
Four clusters with high bootstrap support were apparent. One cluster was made up of C. ergensi Dossou , C. tiberianus Paperna , C. douellouae Pariselle, Bilong & Euzet, , C. aegypticus Ergens , C. arthracanthus Paperna  and C. cubitus Dossou  (bootstrap values 81, 88 and 73 %). Another cluster was made up of C. yanni Pariselle & Euzet  and C. digitatus Dossou  (78, 79 and 77 %), a third one of C. amphoratus Pariselle & Euzet  and C. sclerosus Paperna & Thurston,  (98, 96 and 93 %) and the last one of C. falcifer, C. longicirrus, C. dracolemma and C. amieti. Within this last cluster, C. falcifer was the sister species of C. longicirrus, C. dracolemma and C. amieti (99, 96 and 94 %) while C. longicirrus was sister to C. dracolemma and C. amieti (98, 94 and 97 %). These four clusters were not supported by high bootstrap values. Three other species: C. cirratus Paperna , C. njinei Pariselle, Bilong & Euzet  and C. halli Price & Kirk  did not appear related to any group or species.
Principal Component Analysis (PCA)
Loadings and explained variance of the first two PC of the PCA conducted on the “standardized” size of sclerites
Origin and host range of Cichlidogyrus amieti
Cichlidogyrus is the most species-rich ectoparasitic dactylogyridean monogenean genus known to parasitize African cichlid fishes. Species are distributed among a wide range of cichlid hosts [33, 58, 78]. The description of C. amieti from the gills of representatives of Cyprinodontiformes by Birgi and Euzet  raises the question whether a species from this fish order could have been the source host at the origin of the Cichlidogyrus radiation in cichlids (see theories on cichlid biogeography above). An alternative explanation is lateral parasite transfer from a cichlid to a killifish host.
Our phylogenetic reconstruction indicates that C. amieti is phylogenetically nested within the parasites from species of Hemichromis Peters, 1857 at a derived position of the tree. Although we cannot rule out incomplete taxon coverage of Central West African Cichlidogyrus, the present results suggest that C. amieti results from a recent transfer from cichlids to nothobranchiids. That is in accordance with the Birgi and Euzet  hypothesis. Such lateral transfer or host-switch can occur between related host species [31, 33, 79], but even between phylogenetically distant host species, both in artificial and natural conditions [19, 20, 80–84].
Aphyosemion spp. inhabit small forest streams [2, 3] where they live in sympatry with Hemichromis spp.. Bilong Bilong , based on morphological features, already hypothesized that C. amieti could derive from Hemichromis’ monogeneans.
Birgi and Euzet  reported that C. amieti was restricted to A. cameronense and A. obscurum, two species belonging to the same lineage (i.e. the A. cameronense group), but differing from one another by their biology and the fact that they are never found together in the same biotope . In this study, C. amieti was also collected from A. exiguum, a species that does not belong to the A. cameronense group. This new host record can be explained by the sympatry of A. exiguum and A. cameronense or A. obscurum and by the relative phylogenetic proximity of these fish species (compared to the phylogenetic distance between species of Aphyosemion and Hemichromis).
Influence of host-switching on haptoral and reproductive morphology
Working on species of Dactylogyrus, Šimková et al.  stated that congeneric monogenean species occupying similar niches tend to have similar attachment organs. This resemblance is due to the fact that they are subject to the same considerable selective pressure imposed by the microhabitat within the host, possibly the gill morphology [92–96]. When these parasites occur on different host species, their attachment organs tend to differ from each other in their morphology and/or size, because different host species may have different gill structures. As pointed out by Šimková et al. , the morphology of the haptor is therefore an important adaptation of parasites to their hosts (host specificity) and to specific sites within their hosts (niche preference).
The phylogenetic tree obtained in this study (Fig. 1) suggests that C. amieti clusters within the monophyletic group already proposed by Mendlová et al.  and Řehulková et al. , made up of C. longicirrus, C. dracolemma and C. falcifer, all of them parasitizing Hemichromis spp.. The Cichlidogyrus spp. that parasitize Hemichromis spp. have a highly homogenous configuration of their haptoral sclerotized parts (group B in Vignon et al. ): very large first pair and small pairs III to VII of marginal hooks (= pairs II-III-IV and VI-VII sensu Mizelle ) combined with short auricles that are continuous with the dorsal surface of the dorsal transverse bar (Fig. 3a, b, c and d); this morphological relationship is also well supported by the PCA analysis (Fig. 2). In contrast, in C. amieti all marginal hooks are of similar small size including pair I (group A in Vignon et al. ) (Fig. 3e); this difference is also highlighted by our PCA results where this species is set apart regarding the two axes from all the other ones parasitizing Hemichromis spp. (Fig. 2). Therefore we hypothesize that, as soon as the ancestor of C. amieti (with group B morphology of its haptoral sclerites) colonized a species of Aphyosemion, selective pressures lead to a substantial morphological change in the haptoral sclerites, the most visible being the drastic reduction of the size of marginal hook pair I (Fig. 3 arrows). Vignon et al. , focusing on the same monogenean genus, did not find any evidence of host-related adaptation of the haptor morphology. However, these authors only considered Cichlidogyrus spp. infecting cichlids. The present study, considering also a more distant host-switch, provides new evidence supporting the hypothesis of the adaptive nature of haptor morphology also within Cichlidogyrus in accordance with studies on other monogeneans by Morand et al. [97, 98], Huyse and Volckaert  and Bush et al. .
Rohde and Hobbs  and Šimková et al.  showed that congeneric parasite species living in the same niche presented differences in the morphology or size of their reproductive organs, as a result of random differentiation, which made possible their coexistence according to the hypothesis of reinforcement of reproductive barriers by mate discrimination [102–104]. This is the case for Cichlidogyrus spp. harbored by Hemichromis spp., which are well differentiated from each other by the morphology or size of their reproductive organs (Fig. 4a, b, c and d). Regarding the male copulatory organ (MCO) of C. amieti, we notice that it presents a tubular filiform single-looped penis without swollen portion and with a well-developed heel, and a sharply curved accessory piece with rounded ending [23, 58] (Fig. 4e). It resembles C. dracolemma (Fig. 4e) as pointed out by Řehulková et al. . Therefore we may assume that C. dracolemma or a close relative was transferred from a species of Hemichromis to an Aphyosemion. This suggestion is strongly supported by the close phylogenetic relationship between these two parasite species (Fig. 1). Finally, the specialization of these two parasite species on phylogenetically distant hosts (i.e. cichlid and killifish species) prevented their hybridization, thus explaining why their MCO morphologies have not been affected by selective pressure and thus did not substantially diverge.
Phylogenetic analysis suggests that C. amieti results from a recent host-switch from a cichlid species belonging to Hemichromis. The fact that the haptoral hard parts of C. amieti are of a different morphotype than those of its closely related congeners infecting Hemichromis spp., is the first proof, within Cichlidogyrus, of an adaptive component to haptoral morphology influenced by transfer to a new host. Previously, haptoral morphology of Cichlidogyrus was considered to be mainly phylogenetically constrained. The changes in the haptoral elements after the host-switching event are in stark contrast to the similarity in male genital morphology to the parasites of representatives of Hemichromis. As genital differentiation between monogenean species is thought to be linked to reinforcement of parasite genetic isolation within the same host species, we suggest this similarity is a consequence of C. amieti having speciated as a result of host-switching. This study underscores the potential of Cichlidogyrus as a model to test the influence of ecology and evolution on parasite speciation [19, 78]. The fact that the adaptive component of haptoral morphology of Cichlidogyrus was not inferred when including only species infecting cichlids, also demonstrates the importance of including the full phylogenetic or host range of a parasite clade to reconstruct its speciation mechanisms.
This work was partially funded (2013) by the representation of IRD (Institut de Recherche pour le Développement) in Cameroon through the project « Programme Pilote Régional: Forêt Tropicale Humide d’Afrique Centrale » (PPR FTH-AC). M.P.M.V. is supported by the Czech Science Foundation, Project no. P505/12/G112 (European Centre of Ichthyoparasitology (ECIP) - Centre of excellence). Sequences were produced through the technical facilities of the Centre Méditerranéen Environnement Biodiversité (CeMEB). Authors want to thank W. Boeger and the two anonymous referees for their input to the revised version of the manuscript. This is publication ISE-M 2015-179 SUD.
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