Osteoglossomorph Fishes Research Articles

A new species of Osteoglossomorpha (Actinopterygii: Teleostei) from the Upper Cretaceous Nemegt Formation of Mongolia: Paleobiological and paleobiogeographic implications

Compared to abundant dinosaur faunas, fish materials are scarce in the Nemegt Formation (Maastrichtian) of Mongolia except for isolated centra assigned to the Hiodontidae (Osteoglossomopha). Here we report new additional fish materials collected from the Nemegt Formation. They include skull parts (quadrate, premaxilla, and dentary), isolated and articulated centra, and a caudal fin. New specimens appear to be the same taxon as the previously reported samples from the Nemegt Formation based on morphological similarities in the abdominal centra. However, all specimens represent a new genus and species of osteoglossomorph fish, Harenaichthys lui gen. et sp. nov. Phylogenetic analysis reveals that Harenaichthys is a basal member of the osteoglossomorphs instead of being included in the hiodontids. The comparison of Harenaichthys with Chinese osteoglossomorph Xixiaichthys tongxinensis and a fish centrum found along with the theropod dinosaur Raptorex kriegsteini supports a previous conclusion that R. kriegsteini comes from the Nemegt Formation. Unusual monospecific occurrences of Harenaichthys in many localities allow us to understand their paleoecology and paleobiogeography better. In addition, the pathologic features seen on some centra of Harenaicthys indicate that they suffered from various diseases in life.

Molecular Evolution of clock Genes in Vertebrates.

Circadian rhythms not only influence the overall daily routine of organisms but also directly affect life activities to varying degrees. Circadian locomotor output cycle kaput (Clock), the most critical gene in the circadian rhythm feedback system, plays an important role in the regulation of biological rhythms. Here, we aimed to elucidate the evolutionary history of the clock gene family in a taxonomically diverse set of vertebrates, providing novel insights into the evolution of the clock gene family based on 102 vertebrate genomes. Using genome-wide analysis, we extracted 264 clock sequences. In lobe-finned fishes and some basal non-teleost ray-finned fishes, only two clock isotypes were found (clock1 and clock2). However, the majority of teleosts possess three clock genes (two clock1 genes and one clock2 gene) owing to extra whole-genome duplication. The following syntenic analysis confirmed that clock1a, clock1b, and clock2 are conserved in teleost species. Interestingly, we discovered that osteoglossomorph fishes possess two clock2 genes. Moreover, protein sequence comparisons indicate that CLOCK protein changes among vertebrates were concentrated at the N-terminal and poly Q regions. We also performed a dN/dS analysis, and the results suggest that clock1 and clock2 may show distinct fates for duplicated genes between the lobe-finned and ray-finned fish clades. Collectively, these results provide a genome-wide insight into clock gene evolution in vertebrates.

Four type I IFNs, IFNa1, IFNa2, IFNb, IFNc, and their receptor usage in an osteoglossomorph fish, the Asian arowana, Scleropages formosus

In fish, type I IFNs are classified into three groups, i.e. Group I, Group II and Group III, which are further divided into seven subgroups according to the number of conservative cysteines, phylogenetic relationship, and probably their receptor complexes. In the present study, four type I IFNs and four cytokine receptor family B members (CRFBs) were identified in the Asian arowana, Scleropages formosus, an ancient species in the Osteoglossomorpha with commercial and conservation values. According to multiple sequence alignment and phylogenetic relationship, the four type I IFNs are named as IFNa1, IFNa2, IFNb and IFNc, with the former two belonging to Group I, and the latter two to Group II. The four receptors are named as CRFB1, CRFB2, CRFB5a and CRFB5b. The IFNs and their possible receptor genes are widely expressed in examined organs/tissues, and are induced following the stimulation of polyinosinic polycytidylic acid (polyI:C) in vivo. It was found that IFNa1, IFNa2, IFNb and IFNc use preferentially the receptor complexes, CRFB1 and CRFB5b, CRFB1 and CRFB5b, CRFB2 and CRFB5a, and CRFB2 and CRFB5b, respectively, indicating the evolutionary diversification in the interaction of type I IFNs and their receptors in this ancient fish species, S. formosus.

The Cone Opsin Repertoire of Osteoglossomorph Fishes: Gene Loss inMormyrid Electric Fish and a Long Wavelength-Sensitive Cone Opsin That Survived 3R.

The Cone Opsin Repertoire of Osteoglossomorph Fishes: Gene Loss inMormyrid Electric Fish and a Long Wavelength-Sensitive Cone Opsin That Survived 3R.

A review of the systematic biology of fossil and living bony-tongue fishes, Osteoglossomorpha (Actinopterygii: Teleostei)

ABSTRACT The bony-tongue fishes, Osteoglossomorpha, have been the focus of a great deal of morphological, systematic, and evolutionary study, due in part to their basal position among extant teleostean fishes. This group includes the mooneyes (Hiodontidae), knifefishes (Notopteridae), the abu (Gymnarchidae), elephantfishes (Mormyridae), arawanas and pirarucu (Osteoglossidae), and the African butterfly fish (Pantodontidae). This morphologically heterogeneous group also has a long and diverse fossil record, including taxa from all continents and both freshwater and marine deposits. The phylogenetic relationships among most extant osteoglossomorph families are widely agreed upon. However, there is still much to discover about the systematic biology of these fishes, particularly with regard to the phylogenetic affinities of several fossil taxa, within Mormyridae, and the position of Pantodon. In this paper we review the state of knowledge for osteoglossomorph fishes. We first provide an overview of the diversity of Osteoglossomorpha, and then discuss studies of the phylogeny of Osteoglossomorpha from both morphological and molecular perspectives, as well as biogeographic analyses of the group. Finally, we offer our perspectives on future needs for research on the systematic biology of Osteoglossomorpha.

Diversification of Hox Gene Clusters in Osteoglossomorph Fish in Comparison to Other Teleosts and the Spotted Gar Outgroup.

An ancient genome duplication (TGD or 3R) occurred in teleost fish after divergence from the lineage leading to gar. This genome duplication is shared by the three extant teleost lineages: Osteoglossomorpha (bony-tongues), Elopomorpha (eels and tarpons), and Clupeocephala (a large clade including salmon, carp, medaka, zebrafish, cichlids, pufferfish, stickleback, and ∼26,000 other species). After TGD, different clupeocephalan species retained different gene duplicates; this is seen clearly in Hox gene clusters but extends to all genes. Since divergent resolution of TGD paralogs is a potential driving force for speciation, it is possible this contributed to diversification of this clade. The extent to which divergent resolution of TGD paralogs occurred within Osteoglossomorpha has not been investigated in detail, and Hox cluster organization has been reported for just two species: Pantodon buchholzi (Pantodontidae) and Scleropages formosus (Osteoglossidae). We applied survey-scale genome sequencing and de novo assembly to three further osteoglossomorph taxa: Osteoglossum bicirrhosum (Osteoglossidae), Chitala ornata (Notopteridae), and Gnathonemus petersii (Mormyridae). We find that each retained more Hox genes than clupeocephalan taxa (excluding those that underwent additional genome duplication), but fewer than eels. Several Hox genes are missing in all teleosts, including duplicates of two Hox genes present in the slow evolving pre-TGD genome of the spotted gar. We find divergent resolution through individual gene losses, and whole cluster losses have been rampant across osteoglossomorphs, despite their extant species paucity. We suggest that reciprocal gene loss following TGD was probably insufficient to drive the exceptional diversification of teleosts.

The expansion of Arapaima cf. gigas (Osteoglossiformes: Arapaimidae) in the Bolivian Amazon as informed by citizen and formal science

The giant osteoglossomorph fish Arapaima cf. gigas was introduced to the northern Bolivian Amazon over a half century ago and now contributes significantly to commercial fisheries. Despite this, little is known regarding its current distribution and invasion potential. Here, we address this knowledge gap using two complementary methods: interviewing key informants and examining fisheries landing records in the principal landing site (Riberalta). Both interviews and landing data revealed that the species represents approximately 50% of the total commercial catches, and that it now occupies approximately 340 km 2 of floodplain lakes in the Beni, Orthon and Madre de Dios River basins. The annual yield is estimated at 258 t, equivalent to 0.76 kg/ha/year. The current geographic distribution represents approximately one-quarter (24%) of floodplain lakes in the lower Bolivian Amazon, suggesting high fisheries potential of the species if it would also colonize the remaining Mamore and Itenez River basins. The potential for negative ecosystem impacts of the A. cf. gigas invasion seems likely, considering the large body size, life history and feeding ecology of this species, but has not yet been clearly demonstrated. Factors that might limit further expansion are natural barriers (waterfalls) in the lower Mamore, and periodic cold temperature conditions in the Mamore and Itenez River basins.

Neural innovations and the diversification of African weakly electric fishes

In African mormyrid fishes, evolutionary change in a sensory region of the brain established an ability to detect subtle variation in electric communication signals. In one lineage, this newfound perceptual ability triggered a dramatic increase in the rates of signal evolution and species diversification. This particular neural innovation is just one in a series of nested evolutionary novelties that characterize the sensory and motor systems of mormyrids, the most speciose group of extant osteoglossomorph fishes. Here we discuss the behavioral significance of these neural innovations, relate them to differences in extant species diversity, and outline possible scenarios by which some of these traits may have fueled diversification. We propose that sensory and motor capabilities limit the extent to which signals evolve and, by extension, the role of communication behavior in the process of speciation. By expanding these capabilities, neural innovations increase the potential for signal evolution and species diversification.

A new Cretaceous osteoglossomorph fish from Gansu Province, China

ABSTRACT Several specimens of a fossil fish recently collected from Cretaceous deposits near Changma, Gansu Province, China, are here described as a new genus and species of osteoglossomorph, Shuleichthys brachypteryx. This fish is a stem osteoglossomorph that cannot be included in either the Hiodontiformes or Osteoglossiformes without making either order polyphyletic. The fossils from the Changma locality are exceptionally well preserved, and allow many details of the anatomy of the new fish to be described, including the presence of a postpelvic bone, which was previously only known to be present in the living Hiodon. The relationships of the osteoglossomorph fishes are still not well resolved, and the addition of the new species to previous phylogenetic analyses causes even less resolution to be found. However, the new species appears to be more derived than Lycoptera and Paralycoptera, two other well-known stem osteoglossomorphs.

Functional morphology and biomechanics of the tongue‐bite apparatus in salmonid and osteoglossomorph fishes

The tongue-bite apparatus and its associated musculoskeletal elements of the pectoral girdle and neurocranium form the structural basis of raking, a unique prey-processing behaviour in salmonid and osteoglossomorph fishes. Using a quantitative approach, the functional osteology and myology of this system were compared between representatives of each lineage, i.e. the salmonid Salvelinus fontinalis (N = 10) and the osteoglossomorph Chitala ornata (N = 8). Divergence was found in the morphology of the novel cleithrobranchial ligament, which potentially relates to kinematic differences between the raking lineage representatives. Salvelinus had greater anatomical cross-sectional areas of the epaxial, hypaxial and protractor hyoideus muscles, whereas Chitala had greater sternohyoideus and adductor mandibulae mass. Two osteology-based biomechanical models (a third-order lever for neurocranial elevation and a modified four-bar linkage for hyoid retraction) showed divergent force/velocity priorities in the study taxa. Salvelinus maximizes both force (via powerful cranial muscles) and velocity (through mechanical amplification) during raking. In contrast, Chitala has relatively low muscle force but more efficient force transmission through both mechanisms compared with Salvelinus. It remains unclear if and how behavioural modulation and specializations in the post-cranial anatomy may affect the force/velocity trade-offs in Chitala. Further studies of tongue-bite apparatus morphology and biomechanics in a broader species range may help to clarify the role that osteology and myology play in the evolution of behavioural diversity.

The historical biogeography of the freshwater knifefishes using mitogenomic approaches: A Mesozoic origin of the Asian notopterids (Actinopterygii: Osteoglossomorpha)

The continental distributions of freshwater fishes in the family Notopteridae (Osteoglossomorpha) across Africa, India, and Southeast Asia constitute a long standing and enigmatic problem of freshwater biogeography. The migrational pathway of the Asian notopterids has been discussed in light of two competing schemes: the first posits recent transcontinental dispersal while the second relies on distributions being shaped by ancient vicariance associated with plate-tectonic events. In this study, we determined complete mitochondrial DNA sequences from 10 osteoglossomorph fishes to estimate phylogenetic relationships using partitioned Bayesian and maximum likelihood methods and divergence dates of the family Notopteridae with a partitioned Bayesian approach. We used six species representing the major lineages of the Notopteridae and seven species from the remaining osteoglossomorph families. Fourteen more-derived teleosts, nine basal actinopterygians, two coelacanths, and one shark were used as outgroups. Phylogenetic analyses indicated that the African and Asian notopterids formed a sister group to each other and that these notopterids were a sister to a clade comprising two African families (Mormyridae and Gymnarchidae). Estimated divergence time between the African and Asian notopterids dated back to the early Cretaceous when India–Madagascar separated from the African part of Gondwanaland. Thus, estimated time of divergence based on the molecular evidence is at odds with the recent dispersal model. It can be reconciled with the geological and paleontological evidence to support the vicariance model in which the Asian notopterids diverged from the African notopterids in Gondwanaland and migrated into Eurasia on the Indian subcontinent from the Cretaceous to the Tertiary. However, we could not exclude an alternative explanation that the African and Asian notopterids diverged in Pangea before its complete separation into Laurasia and Gondwanaland, to which these two lineages were later confined, respectively.

Fossil Mooneyes (Teleostei: Hiodontiformes, Hiodontidae) from the Eocene of western North America, with a reassessment of their taxonomy

Abstract The skeletal anatomy of fossil hiodontids from western North America is examined based on newly-prepared specimens, including several specimens that were prepared using the acid transfer method and some using the ‘lost fossil’ technique. This study resulted in many new interpretations and clarifications, such as the presence of a curved tubular nasal bone and a posterodorsal spine on the opercle of ‘† Eohiodon ’, as found in extant Hiodon . We also further describe the variation of the caudal skeleton that has been known in both fossil and extant Hiodon . For instance, the neural spine of preural one is most often fully developed (as it is in a minority of extant Hiodon specimens), although in some specimens it is rudimentary, as it is in most specimens of living taxa. We review the characters that have been used in recent analyses of relationships of osteoglossomorph fishes. After correcting the descriptions of the fossil taxa, we could find no valid synapomorphies to separate the genus † Eohiodon from the genus Hiodon . Therefore, we conclude that † Eohiodon should be regarded as a synonym of Hiodon .

Description of a new Eocene osteoglossid fish and additional information on †Singida jacksonoides Greenwood and Patterson, 1967 (Osteoglossomorpha), with an assessment of their phylogenetic relationships

A new genus and species of osteoglossomorph fish is described from the Eocene Mahenge site in north central Tanzania. The new species is sympatric with the previously described osteoglossomorph †Singida jacksonoides, but is easily distinguished from it by the presence in the new species of teeth on the jaws and entopterygoid. The new species shares characters with the Heterotidinae, such as the two arms of the preopercle being of similar length and the posterior end of the maxilla lying on the dentary, and other characters with the Osteoglossinae (including †Phareodus), for example the enlarged pectoral fin ray and the shape of the opercular bone. New specimens of †S. jacksonoides also have been recovered from the site, providing more information on the osteology of this fish. The relationships of these two Mahenge osteoglossomorphs are assessed, with both fishes placed within the Osteoglossidae, but of uncertain position in the family. Addition of the new species to previous cladistic data sets, and the revised information for †S. jacksonoides, causes the subfamily Osteoglossinae to be nonmonophyletic. © 2005 The Linnean Society of London, Zoological Journal of the Linnean Society, 2005, 144, 213–228.

The novel «tongue-bite apparatus» in the knifefish family Notopteridae (Teleostei: Osteoglossomorpha): are kinematic patterns conserved within a clade?

Osteoglossomorph fishes are unique in possessing a specialized feeding mechanism, the tongue-bite apparatus (TBA) involving the hyoid apparatus. The TBA is associated with two unique behaviour patterns – raking and open-mouth chewing – used to disable and macerate prey. The kinematics of these two behaviours was compared in two species of knifefishes (family Notopteridae) Xenomystus nigri (Günther, 1868) and Chitala ornata (Gray, 1831) using high-speed video (250 frames s−1). Both univariate and multivariate analyses indicated that there were significant interspecific differences in both raking and open-mouth chewing. Raking can be divided into three stages; the preparatory phase, power stroke, and recovery phase. During the power stroke posterior motion of the pectoral girdle and neurocranial elevation both appear to play a major role in prey reduction. In Xenomystus the power stroke involves significantly greater levels of neurocranial elevation (35°) and pectoral girdle motion (38% of head length; 9.5°) than that found inChitala (neurocranial elevation 11°; pectoral girdle motion 11% of head length and 5°). Indeed,Xenomystus represents the most extreme raking behaviour of any osteoglossomorph thus far studied. Temporal displacement variables demonstrated that the power stroke in Xenomystus is significantly faster than in Chitala. Although some of the interspecific differences might be size related, these data suggest that a greater degree of difference exists in these highly specialized behaviours than previous work has demonstrated. These findings support the notion that biomechanical duplication (an additional ligament found in osteoglossomorphs) could be linked to increased functional versatility.

The novel ‘tongue-bite apparatus’ in the knifefish family Notopteridae (Teleostei: Osteoglossomorpha): are kinematic patterns conserved within a clade?

Osteoglossomorph fishes are unique in possessing a specialized feeding mechanism, the tongue-bite apparatus (TBA) involving the hyoid apparatus. The TBA is associated with two unique behaviour patterns – raking and open-mouth chewing – used to disable and macerate prey. The kinematics of these two behaviours was compared in two species of knifefishes (family Notopteridae) Xenomystus nigri (Gunther, 1868) and Chitala ornata (Gray, 1831) using high-speed video (250 frames s−1). Both univariate and multivariate analyses indicated that there were significant interspecific differences in both raking and open-mouth chewing. Raking can be divided into three stages; the preparatory phase, power stroke, and recovery phase. During the power stroke posterior motion of the pectoral girdle and neurocranial elevation both appear to play a major role in prey reduction. In Xenomystus the power stroke involves significantly greater levels of neurocranial elevation (35°) and pectoral girdle motion (38% of head length; 9.5°) than that found inChitala (neurocranial elevation 11°; pectoral girdle motion 11% of head length and 5°). Indeed,Xenomystus represents the most extreme raking behaviour of any osteoglossomorph thus far studied. Temporal displacement variables demonstrated that the power stroke in Xenomystus is significantly faster than in Chitala. Although some of the interspecific differences might be size related, these data suggest that a greater degree of difference exists in these highly specialized behaviours than previous work has demonstrated. These findings support the notion that biomechanical duplication (an additional ligament found in osteoglossomorphs) could be linked to increased functional versatility.

Tongue Bite Apparatus of Osteoglossomorph Fishes: Variation of a Character Complex

Osteoglossomorpha were first defined on the basis of two characters: (1) the parasphenoid-tongue bite apparatus (TBA); and (2) the presence of processes associated with the second hypobranchial and/or basibranchial element of the ventral gill arches. These two characters have continued to be cited as unambiguous support of the monophyly of this group of basal teleostean fishes. The TBA has been vaguely defined as a ‘‘bite’’ of gill arch dentition against that of the parasphenoid and palatoquadrate bones. Historical definitions include both plesiomorphic (e.g., enlarged teeth on palatoquadrate bones and gill arches) and apomorphic (e.g., enlarged teeth on the parasphenoid and a direct connection between the sternohyoideus muscle and the ventral gill arch skeleton) character states. Also, the processes associated with the second gill arches are likely components of the osteoglossomorph TBA by providing an additional attachment surface for the sternohyoideus (i.e., in addition to the sternohyoideus-urohyal connection). There is variation both of presence and form of these processes within osteoglossomorphs. To use both the presence or absence of a TBA as well as its component characters in systematic analyses artificially weights the value of this character complex. This character complex should not be used in place of, and especially not in addition to, its component characters.

Kinematics of the Tongue-Bite Apparatus in Osteoglossomorph Fishes

ABSTRACT Osteoglossomorph fishes are characterized by the possession of three sets of jaws used during the capture, maceration and swallowing of prey. One of these jaw systems is a remarkable tongue-bite apparatus used during the intraoral crushing and shredding of prey. Kinematics of the tongue-bite apparatus were quantified, using 200 frames s−1 video and film records of feeding in three genera of osteoglossomorph fishes (Osteoglossum, Pantodon and Notopterus) to examine the biomechanics and function of this mechanical system. Two distinct chewing behaviors associated with the tongue-bite apparatus were identified: raking and open-mouth chewing. In all three species, raking behavior involves holding the prey firmly in the mandibular jaws while the teeth of the tongue-bite apparatus are moved into the prey. However, other aspects of raking behavior are significantly different among the species: for example, only Notopterus uses extensive posterior movement of the pectoral girdle to pull basihyal teeth through the prey. In both Osteoglossum and Pantodon there is little motion of the pectoral girdle, and neurocranial elevation plays the major mechanical role in prey reduction, but there are also kinematic differences between Osteoglossum and Pantodon during raking. The kinematics of open-mouth chewing behavior are also significantly different among the three species. Thus, osteoglossomorph fishes share a similar morphology of the tongue-bite apparatus derived from a common ancestor, but have acquired independent kinematic specializations associated with its use.

Functional morphology of the "tongue-bite" in the osteoglossomorph fish Notopterus.

Osteoglossomorph fishes are characterized by having three sets of jaws: a mandibular jaw apparatus (MJA) anteriorly, a pharyngeal jaw apparatus (PJA) posteriorly, and a tongue-bite apparatus (TBA) associated with basihyal and parasphenoid teeth. The TBA is a novel complex feature of the head that characterizes osteoglossomorph fishes and provides a case study in the origin of novel functions and roles in the vertebrate musculoskeletal system. The function of the tongue-bite in the osteoglossomorph fish Notopterus was characterized by using high-speed cinematography and electromyography. The tongue-bite is used during intraoral prey processing to shred and disable prey. Two distinct uses of the TBA were defined on the basis of kinematic and electromyographic profiles: raking and open-mouth chewing. During raking behavior, the prey is held fixed in the MJA, the neurocranium is elevated, and the pectoral girdle is retracted. The adductor mandibulae, hypaxialis, epaxialis, and posterior intermandibularis muscles are all highly active, but only very low activity is observed in the sternohyoideus muscle. During open-mouth chewing behavior, the prey is located within the oral cavity, posterior pectoral girdle rotation is less than during raking, and the levator operculi muscle shows relatively high activity. We propose that a shearing action of the basihyal (moved anteroposteriorly by the posterior intermandibularis and hypaxial muscles) with respect to the neurocranium (elevated by epaxial muscles) is the critical aspect of the tongue-bite in Notopterus. The body muscles (epaxials and hypaxials) provide the main power for the tongue-bite. We hypothesize that lack of sternohyoideus activity during intraoral prey processing, posterior pectoral girdle rotation, and a long-fibered posterior intermandibularis muscle are novel structures associated with the tongue-bite apparatus within osteoglossomorph fishes.

Considérations sur la position systématique des genres fossiles Leptolepis et Allothrissops au sein des Téléostéens primitifs

Summary. — The author shows on osteological basis that Leptolepis could not be the ancestor of the teleost super-orders Osteoglossomorpha, Clupeomorpha and Elopomorpha but represents an early ofshoot of the teleost super-order Protacanthopterygii. It is also established that Allothrissops is not a primitive osteoglossomorph fish nor the ancestor of the Ichthyodectiformes but a close relative of Leptolepis belonging also to the Leptolepioidei. Elopomorpha and Protacanthopterygii seem to arise from the Pholidophoridae and Osteoglossomorpha and Clupeomorpha from the Ichthyokentemidae ancestors of Ichthyokentema.

Hyoid and ventral gill arch musculature in osteoglossomorph fishes

Hyoid and ventral gill arch musculature in osteoglossomorph fishes