Pharyngeal Teeth Research Articles

Morphology of the digestive tract of Barbus xanthopterus and Ctenopharyngodon idella

The aim of this study is to detected the morphology of the alimentary canal in twofreshwater fish species, Gattan Barbus xanthopterus and Grass carp Ctenopharyngodo idellawhich belonged to cyprinidae.. Increasing in mouth width with body length. Generallypharyngeal teeth arranged according to the following formulas. Gattan : 4-3-2 and 2-3-4Grass carp: 2-5 and 4-2. Variations in the shape, size of pharyngeal teeth were noticed. Theyappear short and wide compact in gattan, but hard and serrated, comb like in grass carp.Different intestinal length were seen indicating differ in feeding natures.

Ontogenetic development of the digestive system and growth in coral trout (Plectropomus leopardus)

Histological studies were used to describe the ontogenetic development of the digestive tract and accessory glands in coral trout, Plectropomus leopardus, from the time of hatching to 54days after hatching (DAH). According to the structural changes in the digestive system, four significant stages were established: the endotrophic stage (Stage I), the endo-exotrophic stage (Stage II) and the exotrophic stage (subdivided into Stages III and IV). The first stage spanned from hatching to the onset of exotrophic feeding at 2DAH. During this stage, the digestive system started to differentiate into the buccopharynx, the oesophagus, the incipient stomach, the midgut, the hindgut and the rectum. During Stage II (2–3DAH), the coral trout larvae mouth opening reached a 0.24±0.05mm gape size, much smaller than most teleosts. Therefore, first-feeding coral trout must feed on small prey like protozoa or small size rotifers (Brachionus rotundiformis). Stage III (3–19DAH) started after the depletion of the yolk sac. During this stage, goblet cells, taste buds and pharyngeal teeth appeared. The pharyngeal teeth may be a sign that the larvae can feed on some live prey with a hard outer cover, such as copepods. Eosinophilic supranuclear vacuoles and lipid vacuoles were found in the hindgut and midgut, respectively, indicating the beginning of protein and lipid absorption. The last stage (after 19DAH) started when the gastric glands and pyloric caeca were formed. Gastric glands were only observed in the cardiac and fundic stomach and not in the pyloric region. The appearance of gastric glands and pyloric caeca could be regarded as the sign for coral trout to start weaning. The ultrastructure of the liver in the 54-DAH coral trout larvae proved that the liver was crucial for lipid storage and metabolism. This study suggested a relatively rapid development of the digestive system in coral trout and provided a theoretical basis for the nutritional requirements and digestive capacity of coral trout.

GSP-37, a novel goldfish scale matrix protein: identification, localization and functional analysis

A novel noncollagenous acidic protein was identified from the scales of goldfish (Carassius auratus), a freshwater teleost. Using an in vitro calcium phosphate crystallization assay, the EDTA-soluble fraction from these scales was screened for crystallization inhibitory activity, and a highly phosphorylated glycoprotein, named goldfish scale protein (GSP)-37, was isolated through 5 HPLC purification steps. The cDNA for GSP-37 has an open reading frame encoding a precursor protein, consisting of a signal peptide and GSP-37, with 19 and 137 amino acid residues, respectively. The C-terminal region of GSP-37 contains the RGD consensus sequence for cell adhesion. Although native GSP-37 strongly inhibited crystallization, alkaline phosphatase treatment dramatically reduced its inhibitory activity. Reverse transcription-PCR analysis revealed that GSP-37 is expressed only in scales but not in other calcified tissues, bones or pharyngeal teeth. In situ hybridization demonstrated that GSP-37-expressing cells were localized in the central regions of regenerating scales, where organic matrices were actively synthesized and were not stained with either alkaline phosphatase or tartrate-resistant acidic phosphatase, osteoblastic and osteoclastic cell markers, respectively. Immunohistochemical analyses showed that GSP-37 is localized in the uppermost region of the bony layer of the scale, which is thought to correspond to the enamel or enameloid layer of vertebrate teeth. All these data strongly indicate that GSP-37 is deeply associated with calcification in fish scales.

Organogenesis of Ballan Wrasse Labrus Bergylta (Ascanius 1767) Larvae

The organogenesis of ballan wrasse, Labrus bergylta, Ascanius, 1767 larvae was studied during the first 49 days after hatching (DAH) with histological and histochemical methods. During the yolk sac stage (0-9 DAH), a syncytial layer had surrounded the yolk sac. At mouth opening, we distinguished a primordial liver and swim bladder, a buccopharyngeal cavity with gill arch cartilages, an exocrine and endocrine pancreas, and a primordial gastrointestinal tract. By the end of this stage, the heart had become functional, the swim bladder had dilated, olfactory organs and inner ear otoliths had developed, the pituitary gland and thyroid follicle could be distinguished, and the eye had become pigmented. During preflexion (10-25 DAH), the swim bladder had inflated, and the renal corpuscles and tubules had joined the collecting duct towards the urinary bladder. Mucous cells were observed, which may provide secretions that protect against abrasion and pathogens. The density of these cells increased in the buccopharyngeal cavity and oesophagus. During flexion (26-33 DAH), secondary lamellae had developed. Increasing functionality of the digestive system coincided with a shift to the appearance of AB-positive mucous cells in the gill openings and the digestive tract. In addition, pharyngeal teeth had developed, which suggested that food preferences might change to include hard-bodied prey. Stage 4 was mainly characterized by increases in the size and complexity of pre existing organs and structures. At 49 DAH, metamorphosis was complete. The temporal sequence of development of the various systems may provide baseline information for aqua culturists and fish biologists in future studies on fish health, feed, feed development, and cultivation of ballan wrasse.

Augmentation of French grunt diet description using combined visual and DNA-based analyses

Trophic linkages within a coral-reef ecosystem may be difficult to discern in fish species that reside on, but do not forage on, coral reefs. Furthermore, dietary analysis of fish can be difficult in situations where prey is thoroughly macerated, resulting in many visually unrecognisable food items. The present study examined whether the inclusion of a DNA-based method could improve the identification of prey consumed by French grunt, Haemulon flavolineatum, a reef fish that possesses pharyngeal teeth and forages on soft-bodied prey items. Visual analysis indicated that crustaceans were most abundant numerically (38.9%), followed by sipunculans (31.0%) and polychaete worms (5.2%), with a substantial number of unidentified prey (12.7%). For the subset of prey with both visual and molecular data, there was a marked reduction in the number of unidentified sipunculans (visual – 31.1%, combined – 4.4%), unidentified crustaceans (visual – 15.6%, combined – 6.7%), and unidentified taxa (visual – 11.1%, combined – 0.0%). Utilising results from both methodologies resulted in an increased number of prey placed at the family level (visual – 6, combined – 33) and species level (visual – 0, combined – 4). Although more costly than visual analysis alone, our study demonstrated the feasibility of DNA-based identification of visually unidentifiable prey in the stomach contents of fish.

A new recording of the rare priapulid Meiopriapulus fijiensis, with comparative notes on juvenile and adult morphology

Specimens of the rare priapulid genus Meiopriapulus were collected near Jeju Island, Korea. Trunk lengths of adult specimens ranged between 1.92mm and 3.38mm, whereas putative juvenile specimens were smaller, measuring 1.10m and 1.30mm. Adult specimens have a head consisting of an eversible pharynx with 16 to 21 rings of regular pharyngeal teeth and two additional basal rings with modified teeth, and an introvert with 3 rings of sensory scalids and ca. 19 to 22 rings of locomotory scalids. About 13 to 14 irregular rings of trunk scalids are present on the anterior part of the trunk, and a single ring with 32 to 38 preanal hooks is located near the posterior end. Comparison with previous descriptions suggests that the recorded specimens are identical with M. fijiensis, and allows us conclude that specimens of the genus that formerly were collected for molecular sequencing at this locality belong to M. fijiensis as well. Examination of juvenile specimens revealed new information about postembryonic development within the species. Rings of pharyngeal teeth are added during development from a zone in the anterior part of the everted pharynx. Also the numbers of scale-like cover elements on the ornamented sensory scalids increase during development, as well as the numbers of locomotory scalids and trunk scalids. Juvenile morphology has not previously been described in detail from other populations of M. fijiensis, and future studies may reveal differences that would justify a distinction between several species within the genus. In addition to the morphological data, molecular sequence data of COI from 6 specimens and 18S rRNA from 3 specimens has been made available and deposited in GenBank for future molecular taxonomic studies.

Dentition of eight species of Mediterranean Sea Gobiidae: do dentition characters of gobies reflect phylogenetic relationships?

Oral and pharyngeal dentition was analysed in eight Mediterranean species of five different genera using scanning electron microscopy (SEM). Number, position, shape and size of teeth in the jaws and the pharyngeal tooth plates were used as a basis for comparison among taxa. Three different groups could be established based on the dental morphology among the species investigated and homoplasy due to feeding ecology cannot be considered the reason for similarity among them. The established groups are suggested to reflect phylogenetic relationships and correspond with the scarce published data on the topic.

Homozygosity Mapping and Candidate Prioritization Identify Mutations, Missed by Whole-Exome Sequencing, in SMOC2, Causing Major Dental Developmental Defects

Inherited dental malformations constitute a clinically and genetically heterogeneous group of disorders. Here, we report on a severe developmental dental defect that results in a dentin dysplasia phenotype with major microdontia, oligodontia, and shape abnormalities in a highly consanguineous family. Homozygosity mapping revealed a unique zone on 6q27-ter. The two affected children were found tocarry a homozygous mutation in SMOC2. Knockdown of smoc2 in zebrafish showed pharyngeal teeth that had abnormalities reminiscent of the human phenotype. Moreover, smoc2 depletion in zebrafish affected the expression of three major odontogenesis genes: dlx2, bmp2, and pitx2.

Teeth before jaws? Comparative analysis of the structure and development of the external and internal scales in the extinct jawless vertebrateLoganellia scotica

Traditional hypotheses posit that teeth evolved from dermal scales, through the expansion of odontogenetically competent ectoderm into the mouth of jawless vertebrates. The discovery of tooth-like scales inside thelodonts, an extinct group of jawless vertebrates, led to the alternative hypothesis that teeth evolved from endodermal derivatives and that there exists a fundamental developmental and phylogenetic distinction between oral/pharyngeal and external odontodes. We set out a test of this latter hypothesis, examining the development of scales of the thelodont Loganellia scotica using synchrotron radiation X-ray tomographic microscopy (SRXTM). We reveal that the internal scales are organized into fused patches and rows, a key distinction from the discrete dermal scales. The pattern of growth of oral scale patches is polarized, but not along a particular vector, whereas pharyngeal scale rows grew along a vector. Our test of the phylogenetic distribution of oral and pharyngeal scales and teeth in vertebrates indicates that odontodes are first expressed in an external position. Internal scales, where present, are always located near to external orifices; the sequential development of pharyngeal scales in Loganellia is peculiar among thelodonts and other stem gnathostomes. It represents a convergence on, rather than the establishment of, the developmental pattern underpinning tooth replacement in jawed vertebrates. The available evidence suggests that internal odontodes evolved through the expansion of odontogenic competence from external to internal epithelia.

The homology of odontodes in gnathostomes: insights from Dlx gene expression in the dogfish, Scyliorhinus canicula

BackgroundTeeth and tooth-like structures, together named odontodes, are repeated organs thought to share a common evolutionary origin. These structures can be found in gnathostomes at different locations along the body: oral teeth in the jaws, teeth and denticles in the oral-pharyngeal cavity, and dermal denticles on elasmobranch skin. We, and other colleagues, had previously shown that teeth in any location were serially homologous because: i) pharyngeal and oral teeth develop through a common developmental module; and ii) the expression patterns of the Dlx genes during odontogenesis were highly divergent between species but almost identical between oral and pharyngeal dentitions within the same species. Here we examine Dlx gene expression in oral teeth and dermal denticles in order to test the hypothesis of serial homology between these odontodes.ResultsWe present a detailed comparison of the first developing teeth and dermal denticles (caudal primary scales) of the dogfish (Scyliorhinus canicula) and show that both odontodes develop through identical stages that correspond to the common stages of oral and pharyngeal odontogenesis. We identified six Dlx paralogs in the dogfish and found that three showed strong transcription in teeth and dermal denticles (Dlx3, Dlx4 and Dlx5) whereas a weak expression was detected for Dlx1 in dermal denticles and teeth, and for Dlx2 in dermal denticles. Very few differences in Dlx expression patterns could be detected between tooth and dermal denticle development, except for the absence of Dlx2 expression in teeth.ConclusionsTaken together, our histological and expression data strongly suggest that teeth and dermal denticles develop from the same developmental module and under the control of the same set of Dlx genes. Teeth and dermal denticles should therefore be considered as serial homologs developing through the initiation of a common gene regulatory network (GRN) at several body locations. This mechanism of heterotopy supports the 'inside and out' model that has been recently proposed for odontode evolution.

Ontogenetic changes in pharyngeal morphology correlate with a diet shift from arthropods to dreissenid mussels in round gobies ( Neogobius melanostomus)

The potential of predators to regulate populations of dreissenid mussels ( Dreissena polymorpha and Dreissena rostriformis bugensis) has been addressed since early in the dreissenid invasion of North America. Round gobies ( Neogobius melanostomus) larger than approximately 60 mm have been shown to prey extensively on dreissenids, whereas smaller round gobies feed mainly on aquatic insects and crustaceans. We propose that ontogenetic changes in pharyngeal morphology may contribute to this diet shift in round gobies. Pharyngeals of 69 round gobies ranging from 31 to 164 mm total length were investigated using light microscopy and scanning electron microscopy. Areas of lower pharyngeals and pharyngobranchial 2 increased allometrically with fish length. Pharyngeals of round gobies smaller than 50 mm contained narrow (< 0.1 mm diameter) papilliform teeth that are consistent with eating soft-bodied prey. By the time round gobies reached approximately 80 mm in length, pharyngeals contained larger diameter (0.3–0.5 mm) molariform teeth typical of those found in molluscivorous fish. Pharyngeal teeth of the largest round gobies also showed considerable wear. Although changes in pharyngeal morphology may contribute to the previously described diet shift in round gobies as they age, genetic and environmental factors both likely influence pharyngeal remodeling and therefore merit further investigation.

Effect of thyroid hormones on the development of pharyngeal dentition in roach Rutilus rutilus (Cyprinidae, Cypriniformes)

Development of teeth on the pharyngeal bones of roach Rutilus rutilus and the effect of thyroid hormones on this development are investigated. The addition of exogenous triiodothyronine leads to accelerated development of the teeth, but the deficit of triiodothyronine (provoked by the addition of thiourea in the media) stimulates the retardation of this development. Change of developmental rate of the organism leads to change in the definitive state of the pharyngeal teeth formula. Owing to accelerated development, the number of teeth significantly decreases, and the formulas 5–5, 5–4, and 4–4 appear instead of the typical formula 6–5 in the control group and in the fish from natural populations. Retarded development of the organism leads to increased frequency of occurrence of the formula 6–6. The directed asymmetry in the numbers of pharyngeal teeth with the formula (6–5), most likely, is connected with different types of teeth development on the left and right pharyngeal bones.

Morphological variation of the palatal organ and chewing pad of catostomidae (Teleostei: Cypriniformes)

We studied the morphology and shape variation of the palatal organ and chewing pad of sucker fishes, family Catostomidae. The palatal organ is a muscularized structure that forms a large mass on the roof of the posterior part of the buccopharyngeal cavity in cypriniform fishes. It functions in coordination with the branchial arches to separate food items from inorganic debris during feeding. The palatal organ exhibits considerable variability in morphology among catostomids. It is shorter, narrower, and thinner in species of the subfamily Cycleptinae (e.g., Cycleptus elongatus) than in other catostomid subfamilies. The thickest and widest palatal organ is seen in species of the subfamily Ictiobinae (e.g., Ictiobus cyprinellus). The shape and size of the palatal organ generally varies between these extremes in species of subfamily Catostominae (e.g., Catostomus and Moxostoma species). Principal components analysis and analysis of variance has differentiated means of various palatal organ measurements for each monophyletic subfamily and tribe of Catostomidae with statistical significance. These results corroborate previously established typological classification of catostomids based on pharyngeal tooth count, pharyngeal tooth morphology, and diet. A keratinized chewing pad forms on the posterior surface of the palatal organ in catostomids or on a skeletal process in cyprinids and serves as an occlusion surface for pharyngeal teeth. The chewing pad is lunate in catostomids and generally ovoid in cyprinids. It is absent from the species of loaches (e.g., botiids, cobitids, and nemacheilids) and gyrinocheilids examined. A synonymy of terms used in the past to describe the palatal organ and chewing pad of Cypriniformes is provided.

A note on Aaptosyax grypus, a very rare, unique cyprinid fish

Rainboth (1991) described a new cyprinid fish, Aaptosyax grypus, from the Mekong River in Thailand, establishing a new monotypic genus. I was very interested in his figures of the species, which was similar to Chanos chanos in general appearance, and visited the fishermen’s base at Khong Chiam, eastern Thailand, several times from April 1998 to January 1999. Then I obtained a total of ten specimens of A. grypus: two from Khong Chiam and eight from the lower reaches near Khone Falls, Laos. All specimens were adult and larger than 700 mm in standard length (SL). One specimen was obtained in August (Khong Chiam), while the others were all obtained from the end of November to December, which may be the spawning season of the species, when the temperature of the Mekong decreases to 20 C, the coolest period (see ‘‘Ecological notes’’). Since Rainboth (1991) first described the superficial characters of A. grypus in detail, little biological information has accumulated for this species (e.g., it is categorized as ‘‘Data Deficient’’ in the IUCN Red List; Kottelat 1996). Here, I report some of the anatomical characteristics and other biological aspects of this very rare fish. Although the specimen for anatomical observation was not kept, another specimens were deposited in Lake Biwa Museum, Shiga, Japan [LBM 1210014953 (740 mm SL), 1210014954 (916 mm SL); tissue for DNA analysis, 1210015335; pharyngeal teeth, 1210026911, 1210047434; all from the Mekong River, Laos]. Mouth parts. In most free-swimming cyprinid fishes, the upper jaw can protrude through the action of the kinethmoid (Alexander 1966). In A. grypus, however, the upper jaw curves strongly and the postero-dorsal end of the premaxillary is supported by a large, curved, arched plate (probably corresponding to the kinethmoid) posteriorly, limiting the antero-posterior movement of the premaxillary. This structure seems to be associated with the biting jaw movement of this species, instead of protrusion (Fig. 1). Weberian ossicles. The claustrum is tightly connected to the supraneural by ligamentous tissue, in contrast to its free state in other cyprinid fishes (Fig. 1). There are also differences in the base of the scaphium and intercalarium, which are not pointed but wide. The connection of the tripus to the air bladder is remarkable. There is no flexible elongation of the transformer process in the end of the tripus; the latter is located free in a thick ligamentous mass that fills the gap between the air bladder and the os suspensorium anteriorly and the vertebral column dorsally. This thick mass is covered with an overhanging curtain from the centrum. There is neither a sagittally running slit in the antero-dorsal corner of the tunica externa nor a thinned area of the tunica interna coinciding with the slit in the tunica externa of the air bladder, which are widely seen in cyprinid fishes (Alexander 1962); these imply that pressure transmission is less effective. All of these characters suggest that the Weberian ossicles of A. grypus are incomplete in communicating sound from the air bladder to the inner ear. Filamentous bones. In lower teleosts, such as Sardinops and other clupeoid fishes, a dense growth of filamentous bones called the osseous brush and the filamentiferous rod (Phillips 1942) develops in the dorso-anterior region of the vertebral column. These bones are not generally found in cyprinid fishes. However, A. grypus possesses well-developed dense filamentous bones similar to those of clupeoids, which are attached to the posterior region of the neurocranium and extend into the trunk muscles (Fig. 1). Y. Tomoda (&) 415-76 Hamabun, Imazu, Takashima, Shiga 520-1604, Japan

A new early cyprinin from Oligocene of South China

Here we describe °Huashancyprinus robustispinus, gen. et sp. nov, a fossil cyprinin fish from the Oligocene of Ningming Basin, Guangxi, South China. It differs from all other cyprinin fishes in the following apomorphic characters: extremely robust last unbranched dorsal and anal fin rays with very fine serrations along posterior edge, the crowns of pharyngeal teeth A2 and A3 with a number of deep grooves on the lateral wall, rather large A3, and relatively deep infraorbital 2. Among the members of the Tribe Cyprinini sensu stricto, it mostly resembles the extant genus Cyprinus, particularly to species Cyprinus micristius and C. fuxianensis, which are restricted to Yunnan, southwestern China. The discovery of the cyprinin °Huashancyprinus from southern China, along with the previously known late Eocene °Cyprinus maomingensis, indicates an early branching of the Cyprininae (Cyprinidae) in this area.

Guianacara dacrya, a new species from the rio Branco and Essequibo River drainages of the Guiana Shield (Perciformes: Cichlidae)

A new species of Guianacara is described from tributaries of the Essequibo River and the rio Branco in Guyana and northern Brazil. Guianacara dacrya, new species, can be diagnosed from all congeners by the possession of a unique infraorbital stripe and by the shape of the lateral margin of the lower pharyngeal jaw tooth plate. Guianacara dacrya can be further distinguished from G. geayi, G. owroewefi, G. sphenozona and G. stergiosi by the possession of a thin midlateral bar, from G. cuyunii by the possession of dusky branchiostegal membranes and from G. oelemariensis by the possession of two supraneurals. This species differs from most congeners by the presence of white spots on the spiny portion of the dorsal fin, the placement of the midlateral spot, the presence of filaments on the dorsal, anal and in rare cases the caudal-fin and from at least the Venezuelan species by several morphometric variables. Guianacara dacrya is known from the Essequibo, Takutu and Ireng River basins of Guyana and possibly from the rio Uraricoera in the rio Branco basin in Brazil. A key to the species is provided.

The evolution of pharyngeal bones and teeth in Gobioninae fishes (Teleostei: Cyprinidae) analyzed with phylogenetic comparative methods

The subfamily Gobioninae is a subgroup in the specious fish family Cyprinidae, which bears high diversity in morphological and ecological dimensions and has its most components distributed in East Asia. In this study, the pharyngeal bones and teeth of 39 species belonging to 19 genera of the Gobioninae were examined, with the phylogenetic comparative method (PCM) and correlation methods employed to analyze the character evolution. Three characters on pharyngeal bones (shape of the pharyngeal bones, extension for attachment of the pharyngo-cleithralis internus posterior (PCIP) muscle, and teeth-bearing area) and six characters of pharyngeal teeth (shape of the five teeth in the main row, number of rows of the teeth) were identified and compared. When the character states were mapped on a molecular phylogenetic tree, it was found that, to adapt to different masticatory operations, different Gobioninae species have various morphological types of pharyngeal bones and teeth: some have intermediate pharyngeal bones bearing multiple rows of diverse teeth (conical, coarsely compressed, and compressed), others have broad pharyngeal bones bearing a single row of molar teeth, and still others have narrow pharyngeal bones bearing a single row of extremely compressed teeth. Tests on the phylogenetic signal and evolutionary associations revealed that evolution of the examined characters was all phylogenetically constrained and correlated. Owing to the homoplasy in evolution, it was suggested that the conventional method of using pharyngeal bones and teeth for phylogenetic reconstruction of cyprinid fishes should not be encouraged.

Ancestral and derived attributes of the dlx gene repertoire, cluster structure and expression patterns in an African cichlid fish

BackgroundCichlid fishes have undergone rapid, expansive evolutionary radiations that are manifested in the diversification of their trophic morphologies, tooth patterning and coloration. Understanding the molecular mechanisms that underlie the cichlids' unique patterns of evolution requires a thorough examination of genes that pattern the neural crest, from which these diverse phenotypes are derived. Among those genes, the homeobox-containing Dlx gene family is of particular interest since it is involved in the patterning of the brain, jaws and teeth.ResultsIn this study, we characterized the dlx genes of an African cichlid fish, Astatotilapia burtoni, to provide a baseline to later allow cross-species comparison within Cichlidae. We identified seven dlx paralogs (dlx1a, -2a, -4a, -3b, -4b, -5a and -6a), whose orthologies were validated with molecular phylogenetic trees. The intergenic regions of three dlx gene clusters (dlx1a-2a, dlx3b-4b, and dlx5a-6a) were amplified with long PCR. Intensive cross-species comparison revealed a number of conserved non-coding elements (CNEs) that are shared with other percomorph fishes. This analysis highlighted additional lineage-specific gains/losses of CNEs in different teleost fish lineages and a novel CNE that had previously not been identified. Our gene expression analyses revealed overlapping but distinct expression of dlx orthologs in the developing brain and pharyngeal arches. Notably, four of the seven A. burtoni dlx genes, dlx2a, dlx3b, dlx4a and dlx5a, were expressed in the developing pharyngeal teeth.ConclusionThis comparative study of the dlx genes of A. burtoni has deepened our knowledge of the diversity of the Dlx gene family, in terms of gene repertoire, expression patterns and non-coding elements. We have identified possible cichlid lineage-specific changes, including losses of a subset of dlx expression domains in the pharyngeal teeth, which will be the targets of future functional studies.

Scale and tooth phenotypes in medaka with a mutated ectodysplasin-A receptor: implications for the evolutionary origin of oral and pharyngeal teeth

Ectodermal contribution to the induction of pharyngeal teeth that form in the endodermal territory of the oropharyngeal cavity in some teleost fishes has been a matter of considerable debate. To determine the role of ectodermal cell signaling in scale and tooth formation and thereby to gain insights in evolutionary origin of teeth, we analyzed scales and teeth in rs-3 medaka mutants characterized by reduced scale numbers due to aberrant splicing of the ectodysplasin-A receptor (edar). Current data show that, in addition to a loss of scales (83% reduction), a drastic loss of teeth occurred in both oral (43.5% reduction) and pharyngeal (73.5% reduction) dentitions in rs-3. The remaining scales of rs-3 were irregular in shape and nearly 3 times larger in size relative to those of the wild-type. In contrast, there was no abnormality in size and shape in the remaining teeth of rs-3. In wild-type medaka embryos, there was a direct contact between the surface ectoderm and rostral endoderm in pharyngeal regions before the onset of pharyngeal tooth formation. However, there was no sign of ectodermal cell migration in the pharyngeal endoderm and hence no direct evidence of any ectodermal contribution to pharyngeal odontogenesis. These data suggest differential roles for Eda-Edar signaling in the induction and growth of scales and teeth and support the intrinsic odontogenic competence of the rostral endoderm in medaka.

Two new species of freshwater fishes of the genus Alburnoides, A. fangfangae and A. devolli (Actinopterygii: Cyprinidae), from the Adriatic Sea Basin in Albania

Two new species of the genus Alburnoides are described from the river Seman drainage in the eastern Adriatic Sea basin in Albania. Both species have a pharyngeal tooth formula of 2.5–4.2. Alburnoides fangfangae, which occurs in the upper Osum river system, is distinguished from other members of the genus by a combination of characters including 11½–13½ anal fin branched rays, small scales numbering 46–53 in the total pored lateral line, total vertebrae usually 40 (20+20 and 21+19) or 41 (21+20 and 20+21), caudal peduncle depth 43–48% body depth at dorsal fin origin, usually a mostly or completely scaleless ventral keel, the mouth with a curved and only slightly slanted cleft and a produced fleshy snout, the interorbital width 1.3–1.5 times the eye diameter, a weakly ossified preethmoid, and a depressed and considerably expanded anterior tip of the basihyal (a unique feature among the western European Alburnoides). Alburnoides devolli, which is described from the upper Devoll river system, differs in having 11½–13½ anal fin branched rays, larger scales numbering 44–48 in the total pored lateral line, total vertebrae usually 40 (20+20), caudal peduncle depth 35–43% body depth at dorsal fin origin, usually a mostly or completely scaled ventral keel, the mouth with a straight and upturned cleft, the interorbital width 1.1–1.4 times the eye diameter, a completely ossified preethmoid, and a narrow, very deeply indented anterior tip of the urohyal (a unique feature among the western European Alburnoides). A comparison with Alburnoides species from River Danube and Prespa, Ohrid, and Skadar lakes is provided.