Molecular phylogeny of species of Ligophorus (Monogenea: Dactylogyridae) and their affinities within the Dactylogyridae

The taxonomic framework of Ligophorus, monogenean specialists of the gills of grey mullets (Mugilidae), is evaluated and its interspecific relationships are assessed for the first time using molecular data. The position of Ligophorus within the paraphyletic Ancyrocephalinae is re-assessed based on newly sequenced species. Furthermore, the relationship between morphometric and genetic interspecific similarities is evaluated. Partial 28S and complete ITS1 rDNA sequences from representatives of 14 of the 16 nominal species of Ligophorus from the Mediterranean, Black and Azov Seas were analysed together with published sequences of members of the Dactylogyridae. The phylogenetic analyses of the Dactylogyridae (i) confirmed the position of Ligophorus within the marine Ancyrocephalinae; (ii) revealed a sister relationship between Ergenstrema and Ligophorus, whose species are all exclusive parasites of grey mullets; and (iii) substantiated the affinities of Ergenstrema with the marine Ancyrocephalinae. The phylogenetic analysis restricted to Ligophorus confirmed the distinct status of the included species. The ITS1 region provided the highest divergence between species and phylograms with the strongest branch support. Both the 28S and ITS1 phylograms revealed two main clades. One included species from hosts with Mediterranean and NE Atlantic distribution and another was formed by species parasitising several Liza spp., including Lz. haematocheilus from the Northwestern Pacific, and Mugil cephalus, which suggests an origin outside the Mediterranean for the latter clade. The phylogenetic evidence presented herein indicated that a combination of host-switching and lineage duplication events accounted for the diversification of this genus in the Mediterranean basin. The agreement between molecular and morphological interspecific similarities observed in Ligophorus supports the validity of morphometric characters used for species identification.     

Molecular phylogeny and speciation patterns in host-specific monogeneans (Cichlidogyrus,Dactylogyridae) parasitizing cichlid fishes (Cichliformes,Cichlidae) in Lake Tanganyika

Cichlidogyrus (including Scutogyrus) is the most speciose dactylogyridean monogenean genus known from African and Levantine cichlid fishes (Cichlidae). While its taxonomy is well established, little is known about the phylogenetic relationships and evolutionary history of this ectoparasite, especially from hosts belonging to one of the most impressive vertebrate radiations, the cichlid fishes from the East African Great Lakes and surrounding hydrological systems. Phylogenetic inference based on DNA sequences of the nuclear 18S, internal transcribed spacer 1 and 28S rDNA genes revealed that Cichlidogyrus parasitizing mainly West African cichlid tribes is paraphyletic with respect to species parasitizing hosts belonging to the East African cichlid radiation, which constitute a well-supported monophylum. Members of Cichlidogyrus from tylochromine and oreochromine hosts that colonised Lake Tanganyika only recently, cluster with their non-Lake Tanganyika relatives, indicating that they colonised Lake Tanganyika with their current host species, and did not jump over from any of the many cichlid species already present in the lake. The diversification of Cichlidogyrus in Lake Tanganyika seems to be driven by failure to diverge in old lineages of cichlids, cospeciation in more recently evolved ones, and host switching followed by parasite duplication at the level of the various host tribes. Evaluation of host specificity and structural evolution of haptoral and reproductive organs in Lake Tanganyika Cichlidogyrus revealed that strict specialist species together with larval hook size represent the ancestral state of haptor configuration, suggesting that members of Cichlidogyrus in this system evolved from a very simple form to a more complex one similarly to their West African congeners. Generalist species among Cichlidogyrus with a sclerotized vagina parasitizing ancient Lake Tanganyika lineages seem to have developed a different hook configuration, most probably to ensure successful colonisation of new, phylogenetically unrelated hosts.     

Territoriality of the omnivorous butterflyfish, Chaetodon auriga (Chaetodontidae)

Butterflyfish research has focused on corallivorous species, with little attention paid to the other, equally abundant, omnivorous and planktivorous species. This study sought to explore the nature of ranging behaviour of the omnivorous butterflyfish, Chaetodon auriga, across two geographic regions. Pairs of C. auriga defended non-overlapping territories, ranging in area from 97.44 m² to 2281.64 m². Mean territory area varied among study sites while remaining consistent between geographic regions. Most of the variation in territory area was explained by variation in butterflyfish density, while damselfish density, total fish density, and percent sand cover inside territories were also correlated with territory area. Benthic assemblages of territories did not mirror study sites, suggesting that territory establishment is non-random. At all study sites, Chaetodon auriga exhibited significant selection in its patterns of habitat resource use. These results highlight the importance of research on generalist butterflyfishes as damage to coral reef ecosystems continues to threaten their specialist counterparts.     

Certain problems of the taxonomy of monogeneans of the order Dactylogyridea (Platyhelminthes: Monogenea)

Different taxonomic problems of the Dactylogyridea Bychowsky, 1937 are discussed. From the recent point of view, all old genera need a careful revision. Taxa of higher ranks should be analysed taking into account their host phylogeny and zoogeography. The order Tetraonchidea Bychovsky should be disband and all its families should be moved to the Dactylogyridea. The aberrant families Montchadskyellidae and Anoplodiscidae also belong to the Dactylogyridea. Dactylogyrideans are most similar to the primitive monogeneans.     

Behavioral and ecological correlates of foureye butterflyfish, Chaetodon capistratus, (Perciformes: Chaetodontidae) infected with Anilocra chaetodontis (Isopoda: Cymothoidae)

We observed the behavior and ecology of Chaetodon capistratus infected and uninfected with the ectoparasitic isopod Anilocra chaetodontis to assess whether there may be parasite induced alterations in host biology, host defenses against infection, and/or pathology related to infection. We also examined habitat related differences in infection rates. Infected fish had higher rates of interaction with conspecifics and spent more time in low flow environments (which might improve transmission of juvenile parasites to new hosts). Butterfly fish without isopods were chased more frequently by damselfishes, fed more, and had larger territories. Time spent near conspecifics, and fish condition and gonadosomatic index did not vary between infected and uninfected fish. These results suggest that foureye butterfly fish behavior is altered by the isopod parasite in order for the isopods to more easily gain mates or transmit offspring to new hosts.     

Evidence for extensive cryptic speciation in trematodes of butterflyfishes (Chaetodontidae) of the tropical Indo-West Pacific

Molecular data from the cytochrome c oxidase subunit I (cox1) mitochondrial DNA gene and the second internal transcribed spacer (ITS2) nuclear rDNA region were used to test the current morphologically-based taxonomic hypothesis regarding species of Monorchiidae (Hurleytrematoides) from chaetodontid and tetraodontid fishes from six sites in the tropical Indo-West Pacific (TIWP): Heron and Lizard Islands off the Great Barrier Reef (GBR, Australia), Moorea (French Polynesia), New Caledonia, Ningaloo Reef (Australia) and Palau. The 16 morphospecies analysed differed from each other by a minimum of 55 bp (9.1%) over the mitochondrial cox1 and 8 bp (1.6%) over the ITS2 DNA regions. For two species, Hurleytrematoides loi and Hurleytrematoides sasali, specimens from the same host species in sympatry differed at levels comparable to those between pairs of distinct morphospecies for both cox1 and ITS2 sequences. We take this as evidence of the presence of combinations of cryptic species; however, we do not propose new species for these taxa because we lack identified morphological voucher specimens. For seven species, Hurleytrematoides coronatum, Hurleytrematoides deblocki, Hurleytrematoides faliexae, H. loi, Hurleytrematoides morandi, H. sasali and Hurleytrematoides sp. A, samples from some combinations of localities had base pair differences that were equal to or greater than differences between some pairs of distinct morphospecies for one or both cox1 and ITS2 sequences. For three species, H. coronatum, H. loi and H. morandi, one haplotype differed from every other haplotype by more than the morphospecies benchmark. In these cases morphological specimens could not be distinguished by morphology. These data suggest extensive cryptic richness in this genus. For the present we refrain from dividing any of the morphospecies. This is because there is a continuum of levels of intra- and interspecific genetic variation in this system, so that distinguishing the two would be largely arbitrary.     

Pteragogus turdus,a new species of wrasse (Perciformes: Labridae) from the Indo-West Pacific Ocean

Ichthyological Research - Pteragogus turdus sp. nov. (Labridae) is described on the basis of 65 specimens (18.5–81.4 mm in standard length: SL) from the eastern Indian Ocean (Western...     

Hox genes from the Polystomatidae (Platyhelminthes, Monogenea)

Hox genes form a multigenic family that play a fundamental role during the early stages of development. They are organised in a single cluster and share a 60 amino acid conserved sequence that corresponds to the DNA binding domain, i.e. the homeodomain. Sequence conservation in this region has allowed investigators to explore Hox diversity in the metazoan lineages. Within parasitic flatworms only homeobox sequences of parasite species from the Cestoda and Digenea have been reported. In the present study we surveyed species of the Polyopisthocotylea (Monogenea) in order to clarify Hox identification and diversification processes in the neodermatan lineage. From cloning of degenerative PCR products of the central region of the homeobox, we report one ParaHox and 25 new Hox sequences from 10 species of the Polystomatidae and one species of the Diclidophoridae, which extend Hox gene diversity from 46 to 72 within Neodermata. Hox sequences from the Polyopisthocotylea were annotated and classified from sequence alignments and Bayesian inferences of 178 Hox, ParaHox and related gene families recovered from all available parasitic platyhelminths and other bilaterian taxa. Our results are discussed in the light of the recent Hox evolutionary schemes. They may provide new perspectives to study the transition from turbellarians to parasitic flatworms with complex life-cycles and outline the first steps for evolutionary developmental biological approaches within platyhelminth parasites.     

Molecular phylogeny of Kalyptorhynchia (Rhabdocoela,Platyhelminthes) inferred from ribosomal sequence data

With 556 species described to date, Kalyptorhynchia includes about one‐third of all species of rhabdocoel flatworms. In this study, we present the first molecular phylogenetic analysis of this taxon. The final analysis comprises 110 species. These represent 11 of the 17 known families. The largest family (241 known species), Polycystididae, is represented by nine of 10 subfamilies and 33 of the 58 genera. Sequence data from 18S rDNA and 28S rDNA were analysed using maximum likelihood and Bayesian approaches. Of the two taxa traditionally recognised within Kalyptorhynchia, Eukalyptorhynchia and Schizorhynchia, only Schizorhynchia is monophyletic. All eukalyptorhynch families, except Cicerinidae, are monophyletic. On the other hand, two of the three schizorhynch families included are not monophyletic. Within Polycystididae, the traditional taxonomy was not reflected in our phylogenetic analyses and most subfamilies are polyphyletic. These results suggest that current classification, mostly based on characters of the genital system, suffers from homoplasy. Where possible, a revised classification, taking into account these new findings, is given.     

Dentition patterns among Pacific and Western Atlantic butterflyfishes (Perciformes,Chaetodontidae): relationship to feeding ecology and evolutionary history

Synopsis The jaw dentition of fifteen species of Pacific and Western Atlantic chaetodontid butterflyfishes was examined in light of their feeding habits and phylogenetic relationships. The ancestral tooth pattern is typical of many of the butterflyfishes, and variations on this basic pattern involve changes in the arrangement, length and number of teeth, and tooth shape to a lesser extent. Many of the more derived conditions can be explained by simple changes in relative jaw shape and size. Despite what appears to be adequate time for evolutionary changes to occur between the Pacific and Western Atlantic faunas, many species retain the generalized tooth arrangement permitting efficient exploitation in a very generalized manner. However, Pacific species as a whole show more specialized morphologies for hard coral feeding than do Western Atlantic species. Cases of parallel and divergent evolution are identified between and among the two faunas. Most morphological change associated with feeding in butterflyfishes is confined to the anterior region of the head, and particularly a few key elements. Suggestions for future morphological studies on the chaetodontids are outlined.     

Molecular phylogeny and speciation of the surfperches (Embiotocidae, Perciformes).

Labroid fishes include a variety of families, such as wrasses (Labridae), odacids (Odacidae), damselfishes (Pomacentridae), parrotfishes (Scaridae), cichlids (Cichlidae), and surfperches (Embiotocidae). With only 23 species, the small embiotocid family exhibits a remarkably low species diversity compared to the large species diversity of the Cichlidae. Using mitochondrial DNA sequences of all 14 extant embiotocid genera, we established a molecular phylogeny of the family and compared it with a previously proposed morphological phylogeny. Genetic differentiation among embiotocids was compared to that among cichlids. Although species numbers are extremely different between these two families, the degrees of genetic differentiation within each family was found to be very similar.     

Sperm ultrastructure in Myxinidocotyle and Acanthocotyle (Platyhelminthes, Monogenea, Acanthocotylidae)

Spermatozoa of Myxinidocotyle californica from the hagfish Eptatretus stoutii and of Acanthocotyle lobianchi from the skate Raja clavata show a similar ultrastructure: two axoncmes of the 9 + 1 type in parallel with the nucleus-and one mitochondrion. In the released Acanthocotyle spermatozoa nucleus and mitochondrion both have a triangular cross-section. No cortical microtubules are present. The ultrastructure of these two acanthocotylid spermatozoa thus corresponds to sperm pattern 2 according to Justine et al. (1985). This pattern is derived from the more primitive pattern 1, which in the Monogenea is found only in the Oligonchoinea Bychowsky, 1937 or the Polyopisthocotylea sensu Justine et al.     

Molecular phylogeny and possible scenario of ponyfish (Perciformes:Leiognathidae) evolution

The family Leiognathidae, commonly known as ponyfish or slip mouth, comprises three genera, each being characterized mainly by mouth morphology. To date, however, neither the phylogenetic relationships within the family nor monophyly of the genera has been tested. The phylogenetic relationships among 14 species of Leiognathidae, inferred from two protein coding mitochondrial genes (ND4 and 5), indicated monophyly of the studied species form genera Gazza and Secutor, and paraphyly of the genus Leiognathus, with L. equulus occupying a basal branch of the family. The relationships allowed phylogenetic analyses of mouthpart structures and light organ systems. The results suggested that the morphology of the upwardly and forwardly protractile mouth types (latter with canine-like teeth) are phylogenetically informative, and the downwardly protractile mouth type being ancestral in the family. The results also suggested that internal sexual dimorphism of the light organ system was present in the common ancestor of a sister clade to L. equulus, whereas external sexual dimorphism seems to have evolved subsequently in two monophyletic subgroups.     

Functional morphology of the feeding apparatus of ten species of Pacific butterflyfishes (Perciformes,Chaetodontidae): an ecomorphological approach

Synopsis The functional morphology of the feeding apparatus and the feeding ecology of an assemblage of ten species of butterflyfishes was investigated using a comparative ecomorphological approach. Behavioral observations in situ and in vivo, morphological measurements of fresh-killed specimens, scanning electron microscopy, and kinematic modeling were utilized. The fishes show varying degrees of morphological and behavioral specialization and generalization. The more specialized species group according to how they feed, rather than what they feed on. The feeding guild concept is therefore not very instructive in understanding the functional significance of the feeding apparatus. Many of the morphologically specialized butterflyfishes demonstrate evolutionary convergence in feeding morphology. Whereas the more morphologically specialized species do generally have more ecologically specialized diets, these data do not particularly support the ecomorphological hypothesis in that similar diets do not correspond to similar morphologies.     

Phylogeny of the Atlantic and Pacific species of Ligophorus (Monogenea: Dactylogyridae): Morphology vs. molecules

Within ectoparasitic fish monogeneans, the genus Ligophorus contains a high number of species from which several were recently described. The precise determination of their taxonomic status requires robust diagnostic morphologic features that rely predominantly on a restricted set of sclerotized structures. In the present study, these morphological characters were used for the reconstruction of a phylogenetic tree, which was compared with a tree built from molecular data (28S and ITS1 DNA sequences). Thirty-eight morphological characters were used in 29 species of Ligophorus from the Atlantic and Pacific regions and 5 species within close genera of Dactylogyridae. The morphological and molecular phylogenetic trees are congruent and suggest that the genus Ligophorus is monophyletic, and that species parasitizing Liza spp. and Chelon labrosus occupy basal positions. The present study suggests that host switching is a common event in this host–parasite association, because about half of the species infecting the same host species are not close relatives. Following host switching, dispersal with vicariance is probably an important force shaping the present distribution and diversity of Ligophorus. The pattern of occurrence of Ligophorus spp. on Mugil cephalus supports that reproductive isolation and therefore parallel speciation are taking place among these parasitic organisms.     

Functional morphology of the head of Hawaiian and Mid-Pacific butterflyfishes (Perciformes,Chaetodontidae)

Synopsis The functional morphology of the jaws of six species of butterflyfishes was investigated and related to their feeding behaviors. Utilizing observations and measurements of fresh-killed specimens as well as scanning electron microscopy of their dentitions, interspecific differences in the size, shape, orientation of the mouth, dentition, degree and function of jaw protrusion were related to their different feeding behaviors. The jaws of the six species showed a variety of adaptations for feeding on or over the reef as well as a repertoire of modulated jaw movements hitherto unnoticed in many studies. This radiation in morphologies was believed to be due to relatively simple changes of a few structural elements, changes that could occur relatively rapidly in the evolutionary time scale. The benefit of naturalistic observations in such functional morphological studies was emphasized.     

Ultrastructure of Spermiogenesis in Acanthocotyle and Myxinidocotyle (Platyhelminthes,Monogenea, Acanthocotylidae)

Abstract Spermiogenesis was studied by transmission electron microscopy in the acanthocotylid monogeneans Myxinidocotyle californica (from Eptatretus stoutii) and Acanthocotyle lobianchi (from Raja clavata). In Myxinidocotyle and Acanthocotyle, the zone of differentiation shows two 9+‘1’ axonemes, the elongating nucleus and mitochondrion, and a single cortical cytoplasmic microtubule. This single microtubule is found in the mature spermatozoon of both species and was also noted in capsalids. This requires a modified definition of ‘pattern 2’ of spermatozoa which becomes: ‘spermatozoa with two axonemes and no cortical microtubules, except one single element much shorter than the spermatozoon’. A very unusual structure was found in Myxinidocotyle, but not in Acanthocotyle: the centriolar derivative of one of the 9+‘1’ axonemes is made up of 18 diverging singlets of unequal length associated with electron-dense cytoplasm. This seems to be the first case of a centriolar derivative without nine-fold symmetry associated with an axoneme with nine-fold symmetry.