Delane C. Kritsky

Phylogeny and a revised classification of the Monogenoidea Bychowsky, 1937 (Platyhelminthes)

A hypothesis (CI=57.3%) on the evolutionary relationships of families comprising the class Monogenoidea is proposed based on 141 character states in 47 homologous series and employing phylogenetic systematics. Based on the analysis, three subclasses, the Polyonchoinea, Polystomatoinea and Oligonchoinea, are recognised. The analysis supports independent origins of the Montchadskyellidae within the Polyonchoinea and of the Neodactylodiscidae and Amphibdellatidae within the order Dactylogyridea (Polyonchoinea); the suborder Montchadskyellinea is raised to ordinal status and new suborders Neodactylodiscinea and Amphibdellatinea are proposed to reflect these origins. The Gyrodactylidea (Polyonchoinea) is supported by three synapomorphies and comprises the Gyrodactylidae, Anoplodiscidae, Tetraonchoididae and Bothitrematidae. The analysis supports recognition of the Polystomatoinea comprising Polystomatidae and Sphyranuridae. Evolutionary relationships within the Oligonchoinea indicate independent origins of three ordinal taxa, the Chimaericolidea (monotypic), Diclybothriidea (including Diclybothriidae and Hexabothriidae) and Mazocraeidea (with five suborders). The suborder Mazocraeinea comprises the Plectanocotylidae, Mazocraeidae and Mazoplectidae, and is characterised by two synapomorphies. The suborder Gastrocotylinea, characterised by presence of accessory sclerites in the haptoral sucker, is divided into two infraorders, the monotypic Anthocotylina infraorder novum and Gastrocotylina. Two superfamilies of the Gastrocotylina are recognised, the Protomicrocotyloidea and Gastrocotyloidea; the Pseudodiclidophoridae is considered incertae sedis within the Gastrocotylina. The suborder Discocotylinea comprises the Discocotylidae, Octomacridae and Diplozoidae and is supported by four synapomorphies. The monotypic Hexostomatinea suborder novum is proposed to reflect an independent origin of the Hexostomatidae within the Mazocraeidea. The terminal suborder Microcotylinea comprises four superfamilies, the Microcotyloidea, Allopyragraphoroidea, Diclidophoroidea and Pyragraphoroidea. The analysis supports incorporation of the Pterinotrematidae in the Pyragraphoroidea and rejection of the monotypic order Pterinotrematidea. The following taxa are also rejected for reasons of paraphyly and/or polyphyly: Articulonchoinea, Bothriocotylea, Eucotylea, Monoaxonematidea, Tetraonchidea, Gotocotyloidea, Anchorophoridae and Macrovalvitrematidae. The Sundanonchidae, Iagotrematidae and Microbothriidae were not included in the analysis because of lack of pertinent information regarding character states.

Coevolution of the Monogenoidea (Platyhelminthes) based on a revised hypothesis of parasite phylogeny.

A revised hypothesis for the phylogeny of the Subclass Polyonchoinea (Monogenoidea) was constructed employing phylogenetic systematics. The Acanthocotylidae (formerly of the Order Capsalidea) is transferred to the Order Gyrodactylidea based on this analysis. The new phylogeny is used to determine coevolutionary relationships of the familial taxa of Monogenoidea with their hosts. The coevolutionary analysis suggests that the Monogenoidea apparently underwent sympatric speciation or dispersal while parasitic on ancestral Gnathostomata, resulting in two primary clades: the Polyonchoinea and the Oligonchoinea + Polystomatoinea. The two parasite clades apparently cospeciated independently with divergence of the Chondrichthyes and Osteichthyes. In the Polyonchoinea, the clade associated with Chondrichthyes experienced primary extinction within the Holocephala, but coevolved into the Loimoidae and Monocotylidae in the Galeomorphii and Squalea (Elasmobranchii), respectively. Within the Osteichthyes, polyonchoineans experienced primary extinction with the divergence of Sarcopterygii, Polypteriformes and Acipenseriformes. They demonstrate primary dispersal from the Neopterygii into the Squalea (as Amphibdellatinea), Actinistia (as Neodactylodiscinea) and Urodela (as Lagarocotylidea). Secondary dispersals of polyonchoineans occurred in the Gyrodactylidae to the Polypteriformes, Urodela and Anura; in the Acanthocotylidae to the Myxinoidea and Squalea; in the Capsalidae to the Acipenseriformes and Elasmobranchii; and in the Monocotylidae to the Holocephala. The Oligonchoinea and Polystomatoinea developed upon divergence of the Chondrichthyes and Osteichthyes. Oligonchoineans cospeciated within the Chondrichthyes, with the Chimaericolidea developing within the Holocephala and the ancestor of the Diclybothriidea + Mazocraeidea within the Elasmobranchii. Two cases of primary dispersal occurred within this clade: the Diclybothriidae to the Acipenseriformes and the ancestor of mazocraeidean families to the Neopterygii (both Osteichthyes). Secondary dispersal within the Oligonchoinea includes host switching of the common ancestor of Callorhynchocotyle (Hexabothriidae) to the Holocephala. Polystomatoineans coevolved within the Osteichthyes, but experienced primary extinctions in the Actinopterygii, Actinistia, Dipnoi and Amniota. Coevolution of the Sphyranuridae and Polystomatidae occurred with divergence of the Urodela and Anura, respectively. Secondary dispersal of Polystomatids to the Urodela, Dipnoi and Amniota is suggested. A preliminary phylogenetic analysis of the Polystomatoinea suggests that primary extinction with secondary dispersal of polystomatids to the Dipnoi may not be necessary to explain extant parasite distributions, since Concinnocotyla (Concinnocotylinae) appears to represent the sister taxon of the remaining Polystomatidae + Sphyranuridae.

THE PHYLOGENETIC STATUS OF THE ANCYROCEPHALIDAE BYCHOWSKY, 1937 (MONOGENEA: DACTYLOGYROIDEA)

Phylogenetic analysis of selected subfamily and family taxa within the Dactylogyroidea indicates that the Ancyrocephalidae Bychowsky, 1937, is unnatural. The family contains both poly- and paraphyletic features. The analysis supports the previous elevation of the Pseudomurraytrematinae to family status and suggests that revision of the Ancyrocephalidae is necessary. Two options for revision are provided; that of returning the taxon to subfamily status within the Dactylogyridae is preferred, requiring a change in status of the Heterotesiidae to a subfamily within the Dactylogyridae.

Context of diversification of the viviparous Gyrodactylidae (Platyhelminthes, Monogenoidea)

Using four criteria proposed a decade ago by Brooks & McLennan to identify a case of adaptive radiation indicates that the evolutionary history of the viviparous clade of the Gyrodactylidae is dominated by nonvicariant processes. The viviparous clade, with 446 species, has significantly more species than its sister clade (one species), and high species richness was shown to be an apomorphic trait of only the viviparous gyrodactylids within the Gyrodactylidae. Reconciliation of the phylogenetic tree of the viviparous Gyrodactylidae with that of its hosts showed a low probability for cospeciation suggesting that adaptive modes of speciation and not vicariance were predominant during the historical diversification of the clade. The proposed hypothesis suggests that the Gyrodactylidae originated on the South American continent about 60 Mya after geographical dispersal and host switching of its common ancestor to demersal freshwater catfishes by a marine ancestor. Development of hyperviviparity and the consequent loss of ‘sticky’ eggs in conjunction with other symplesiomorphic and apomorphic features allowed rapid diversification coupled with high dispersal to new host groups and geographical areas by viviparous members of the Gyrodactylidae.

MODE OF TRANSMISSION, HOST SWITCHING, AND ESCAPE FROM THE RED QUEEN BY VIVIPAROUS GYRODACTYLIDS (MONOGENOIDEA)

Compared to other monogenoidean groups, viviparous gyrodactylids exhibit extraordinary species diversity and broad host range. It has been suggested that this evolutionary success is associated with a suite of morphological and life-history traits that include, in part, continuous transmission (i.e., ability to infect new hosts throughout the gyrodactylid life cycle). Experiments were conducted to explore the putative adaptive advantage of continuous transmission within viviparous gyrodactylids during colonization of new host resources. Differences in infrapopulation growth, such as abundance, prevalence, and duration of the infection, of Gyrodactylus anisopharynx on 3 species of fish—Corydoras paleatus and Corydoras ehrhardti (both natural hosts) as well as Corydoras schwartzi (a host not known to harbor G. anisopharynx)—held under isolated and grouped conditions were determined. Results showed that infrapopulations of G. anisopharynx on C. paleatus and C. schwartzi had higher growth when the parasite had the opportunity for host transfer (grouped hosts). Infrapopulations of G. anisopharynx on isolated and grouped C. ehrhardti showed an opposite trend, although differences in mean duration and maximum abundance were not statistically different. Results obtained from experiments with C. paleatus and C. schwartzi support the hypothesis that continuous transmission in viviparous gyrodactylids enhances colonization success, probably by allowing initial avoidance of Red Queen dynamics. The absence of statistical differences between infrapopulations on isolated and grouped C. ehrhardti suggests that parasite dynamics may be influenced by factors other than continuous transmission in this host.

Parasites, fossils and geologic history: Historical biogeography of the South American freshwater croakers, Plagioscion spp. (Teleostei, Sciaenidae)

A hypothesis on the historical biogeography of the freshwater croakers, Plagioscion spp. (Teleostei: Sciaenidae), is developed based on data from the phylogeny of their monogenoidean parasites (Platyhelminthes), the geology of South America and the fossil record. Analyses suggest that the common ancestor of Plagioscion spp. colonized freshwater concomitantly with the common ancestor of their parasites, Euryhaliotrema spp. Colonization probably occurred via a marine transgression through western Venezuela that developed about 20 million years ago (Mya). This transgression with its postulated highly variable temporal and spatial salinity conditions most likely represented the facilitating event associated with freshwater colonization. A less likely alternative, that colonization occurred via the Mar del Plata in southern South America, is not supported by the geographical distributions and putative phylogeny of extant species of Plagioscion.

DACTYLOGYRIDS (PLATYHELMINTHES: MONOGENOIDEA) PARASITIZING BUTTERFLY FISHES (TELEOSTEI: CHAETODONTIDAE) FROM THE CORAL REEFS OF PALAU, MOOREA, WALLIS, NEW CALEDONIA, AND AUSTRALIA: SPECIES OF EURYHALIOTREMATOIDES N. GEN. AND ALIATREMA N. GEN

Seven species of Euryhaliotrematoides n. gen. and 1 species of Aliatrema n. gen. (Monogenoidea; Dactylogyridae) are described and reported from the gills of 15 species of butterfly fishes (Chaetodontidae) from the coral reefs of Moorea (French Polynesia), Wallis (Wallis and Futuna), Heron and Lizard (Australia), Palau (Micronesia), and New Caledonia: Aliatrema cribbi n. sp. from Chaetodon auriga, Chaetodon lunula, Chaetodon trifasciatus, Chaetodon ulietensis, Chaetodon vagabundus, Forcipiger flavisissimus, and Heniochus chrysostomus; Euryhaliotrematoides annulocirrus n. comb. from C. auriga, C. lunula, and C. vagabundus; Euryhaliotrematoides aspistis n. sp. from C. auriga, Chaetodon citrinellus, C. lunula, Chaetodon reticulatus, C. ulietensis, and C. vagabundus; Euryhaliotrematoides berenguelae n. sp. from C. citrinellus, Chaetodon ornatissimus, and F. flavisissimus; Euryhaliotrematoides grandis n. comb. from C. auriga, C. citrinellus, Chaetodon ephippium, Chaetodon kleinii, Chaetodon lineolatus, C. lunula, C. ornatissimus, C. trifasciatus, C. vagabundus, and H. chrysostomus; Euryhaliotrematoides microphallus n. comb. from C. auriga, C. citrinellus, C. ephippium, C. kleinii, C. lunula, C. ornatissimus, C. reticulatus, Chaetodon trifascialis, C. trifasciatus, C. vagabundus, F. flavisissimus, and H. chrysostomus; Euryhaliotrematoides pirulum n. sp. from C. auriga, C. citrinellus, C. lunula, C. trifasciatus, and C. vagabundus; and Euryhaliotrematoides triangulovagina n. comb. from C. auriga, C. citrinellus, C. kleinii, C. lunula, C. ornatissimus, C. vagabundus, F. flavisissimus, H. chrysostomus, and Hemitaurichthys polylepis. All reports of previously described species are new locality records. With exceptions of E. grandis and E. annulocirrus on C. auriga and C. lunula and E. triangulovagina and E. microphallus on C. auriga, all reports are new host records. Haliotrema hainanensis and H. affinis are considered junior subjective synonyms of E. triangulovagina and E. annulocirrus, respectively. Aliatrema n. gen. is characterized by marine dactylogyrids with tandem gonads (germarium pretesticular), haptoral hooks with upright acute thumbs, a coiled copulatory organ with counterclockwise rings and funnel-shaped base but lacking an accessory piece, and a dextral vaginal pore. Euryhaliotrematoides n. gen. is characterized by marine dactylogyrids having tandem gonads (germarium pretesticular), haptoral hooks with upright acute thumbs, a coiled copulatory organ with counterclockwise rings and funnel-shaped base, a vas deferens looping the left intestinal cecum, and a dextral vaginal pore.

Haliotrema Abaddon N. SP. (Monogenoidea: Dactylogyridae) from the Gills of Wild and Maricultured West Australian Dhufish Glaucosoma Hebraicum (Teleostei: Glaucosomatidae), in Australia

Haliotrema abaddon n. sp. (Dactylogyridae) is described from the gills of West Australian dhufish Glaucosoma hebraicum (Teleostei: Glaucosomatidae), from the Indian Ocean near Fremantle, Western Australia. The parasite is recorded from cultured dhufish and from a major portion of the known geographic distribution of its host. In cultured dhufish, H. abaddon causes branchitis and hyperplasia and metaplasia of the lamellar epithelial cells and may be a limiting factor in the development of an economically feasible mariculture industry. Comparable prevalences and densities of the parasite on wild and cultured dhufish were observed. In heavily infested captive fish, clusters of eggs (egg strands) appear to restrict blood flow to localized regions of the gills as a result of entanglement of egg filaments with secondary gill lamellae. Hatching of oncomiracidia occurs in 7–10 days at 20–25 C.

Studies on monogenetic trematodes. XXXIX. Exotic species of Monopisthocotylea with the proposal of Archidipkctanum gen.n. and Longi-haptor gen.n.

The family Diplectanidae Bychowsky, 1957, and the genera Ancylodiscoides Yamaguti, 1937, Heteroncocleidus Bychowsky, 1957, and Trianchoratus Price and Berry, 1966, are emended. Archidiplectanum gen. n. and Longihaptor gen. n. are proposed and the following new species are described: Ancylodiscoides caecus from an unidentified fish (USNM No. 202610), Thailand; Archidiplectanum archidiplectanum from Gnathonemus petersi (Gunther), western Africa; Heteroncocleidus gracilis from Colisa labiosa (Day), India; Longihaptor longihaptor from Cichla ocellaris Bloch and Schneider, Brazil; Urocleidoides amazonensis and U. catus (both) from Phractocephalus hemiliopterus (Bloch and Schneider), Brazil; U. megorchis from Sorubim lima (Bloch and Schneider), La Plata Drainage to the Magdalena, S. A.; U. robustus from an unidentified South American catfish; and U. variabilils from Symphysodon discus Heckel, Brazil. Trianchoratus acleithrium Price and Berry, 1966, is redescribed. Conspicuous survival of immediately ancestral and liaison species of some Monopisthocotylea is suggested by present information, part of which is contributed by this investigation. Such information implies that the barriers between different genera, subfamilies, and even families are becoming less formidable and in some cases apparently are disappearing. It is postulated that when a comprehensive number of monopisthocotylean species are described, genera and higher taxa may insensibly intergrade with cne another as segments in a continuous succession of species that differ radically only at remotely separated points. On a generic level this phenomenon is illustrated in the Ancyrocephalinae by the originally disjunct genera Cleidodiscus Mueller, 1934 (Mizelle and Hughes, 1938), Urocleidoides Mizelle and Price, 1964 (Mizelle, Kritsky and Crane, 1968), and Urocleidus Mueller, 1934 (Mizelle and Hughes, 1938). Cleidodiscus and Urocleidus, being typically Nearctic genera, occur on fishes very different from those in the Neotropical Region that harbor species of Urocleidoides. The genus Cleidodiscus is characterized by a sinistral vagina (when present) and a proximally articulated cirrus and accessory piece. Urocleidoides is distinguished principally by a sinistral or ventral vagina (when present) and usually a proximally nonarticulated cirrus (coiled shaft) and accessory piece. Principal characteristics of Urocleidus are a 1 Present address: Department of Zoology, University of Illinois, Urbana

Diplectanids infesting the gills of the barramundi Lates calcarifer (Bloch) (Perciformes: Centropomidae), with the proposal of Laticola n. g. (Monogenoidea: Diplectanidae)

Four species of the Monogenoidea, Laticola lingaoensis n. sp., L. latesi (Tripathi, 1957) n. comb. [previously Pseudorhabdosynochus latesi (Tripathi, 1957) Kritsky & Beverley-Burton, 1986], L. paralatesi (Nagibina, 1976) n. comb. [previously Diplectanum paralatesi Nagibina, 1976] and Diplectanum penangi Liang & Leong, 1991, are reported from the gills of Lates calcarifer (Centropomidae) from the South China Sea (new geographical records for L. latesi and D. penangi). Collections from off Bathurst Island, Northern Territory, Australia, represent a new geographic record for L. paralatesi; Chilka Lake, Orissa, India, is established as the type-locality for L. latesi. Laticola n. g. (Diplectanidae) is proposed for species with a spoon-shaped copulatory organ with two to four concentric incomplete ridges in the base. Laticola lingaoensis, the type-species of Laticola, is described, and L. latesi and L. paralatesi are redescribed based on specimens from the South China Sea. Pseudorhabdosynochus monosquamodiscusi Balasuriya & Leong, 1995 and Pseudorhabdosynochus yangjiangenesis Wu & Li, 2005 are considered junior subjective synonyms of L. latesi and L. paralatesi, respectively.