Systematic Biology Advance Access published June 27, 2012 Running Head: EVOLUTION OF PHARYNGOGNATHOUS PERCOMORPH FISHES The Evolution of Pharyngognathy: A Phylogenetic and Functional Appraisal of the Pharyngeal Jaw Key Innovation in Labroid fishes and Beyond Peter C. Wainwright1, W. Leo Smith2, Samantha A. Price1, Kevin L. Tang3, John S. Sparks4, Lara A. Ferry5, … Although this scenario is one of the most well-known examples of an evolutionary key innovation (cited in Futuyma's [11] "Evolutionary Biology", the most widely-used textbook in the field), it has never been evaluated adequately. Nelson JS: Fishes of the world. Homologous muscles have radically changed their relative activity periods while pharyngeal jaw kinematics have been modified relatively little. Miya M, Satoh PS, Nishida M: The phylogenetic position of toadfishes (order Batrachoidiformes) in the higher ray-finned fish as inferred from partitioned Bayesian analysis of 102 whole mitochondrial genome sequences. PubMed Central  Indeed, biomechanical studies of lower jaw shapes [6, 7] quantitatively demonstrated that the labrid functional diversity in lower jaw was well comparable to that of all ray-finned fishes. This distinction might have evolved because the large size and high metabolic rate of mammals makes it difficult to harvest cytoplasm at a rate that can satisfy their nutritional needs, whereas for smaller insects it is more challenging to retain enough food in the gut for the long periods needed to digest fiber. For example, cichlids have colonized many ecosystems such as lakes and rivers that may have provided unique opportunities for those lineages. Red elements are the upper and lower pharyngeal jaws. [42]). Studi e Ricerche sui Giacimenti Terziari di Bolca. Gonochoristic reproduction (reproduction involving two separate sexes) is very common in ancient lake endemics, with self-fertilization as a special case. C R Biologies. Based on the possession of similar complex cuticularized jaws and shared ultrastructural similarities of the epidermis with the syndermates, Micrognathozoa may also be a member of Gnathifera. (a) Here the mandibular (blue) and hyoid (green) arches before being involved in the jaws. The drawing modified from Liem & Greenwood [32]. They are believed to have originated, in a similar way to oral jaws, as a modification of the fifth gill arch which no longer has a respiratory function. Price, Kevin L. Tang, John S. Sparks, Lara Ferry , Kristen L. Kuhn, Ron I. Eytan, Thomas J. Based on molecular analyses, various relationships among the labroid families have been so far proposed [14, 20, 21]. The present analyses were conducted based on the long nucleotide sequences more than six times the lengths of those so far used (13,933 bp). In addition, however, ancient lake endemics are often seen as highly specialized forms that will not easily be able to survive outside of their original habitat, in competition with nonendemic forms. Also, both agree that the lower jaw resides in the ancestral position of the mandibular arch, whereas the upper jaw stems from the forward extension (in front of the mouth opening) of the maxillary part of the mandibular arch (see also THE SKELETON | Bony Fish Skeleton). This explains why the guts of such animals are dominated by the small intestine. Fish Sci. Short PCR reaction conditions followed Miya & Nishida [38]. An unresolved trichotomy is indicated by an arrow, and topological incongruities among the datasets are denoted by open arrowheads (dataset #1 vs. #2) and filled arrowheads (dataset #1 vs. #3). Extended persistence of such subdivided populations might, through genetic drift and population bottlenecks, lead to reproductive isolation between these subpopulations, so that when lake levels rise again, the 2–3 reproductively isolated units might have become different species. Richards WJ, Leis JM: Labroidei: development and relationships. For example, BIC can be large if individuals of different age or size classes use different diets, or if males and females use different diets. Plug flow reactors provide a high rate of digestion but are usually not particularly efficient, and so are best suited to animals with a readily digestible diet such as carnivores and nectar-feeding birds. The percentages for the branches in the consensus trees represent the Bayesian posterior probabilities, which are the rough equivalent of a maximum likelihood search with bootstrapping [53]. doi: 10.1016/j.ydbio.2012.08.026 In doing so, we would be able to evaluate "key innovation" hypothesis in a more rigorous manner using statistical test [15, 16]. The small intestine of many animals most closely approximates this strategy. The independent occurrence of such evolutionary succession (evolution of specialized PJA followed by trophic radiation) appears to support the idea that the evolution of the specialized PJA provided these lineages with the morphological "potential" for trophic radiations. An increase in BIC could occur in a number of different ways. It is interesting fact that the complex "labroid" PJA evolved multiply in the Percomorpha history (other than the two lineages recognized here, two fossil labroid families have been recognized so far from the lower Middle Eocene [ca. We assumed that all of the model parameters were unlinked and rate multipliers were variable across partitions. Jaws evolved in fishes over 460 million years ago. Our analysis demonstrated entirely different relationships from the various ones with high statistical support, whereas none of the previous relationships was supported with high statistical value, probably owing to short sequences (2,222 bp at longest). [31], more than ten genes have been so far recognized which putatively influence teleost pharyngeal jaw. Parameter values and trees were sampled every 1,000 generations, and the samples before the convergence of the Markov chain were discarded for each run. Although the precise relationships between the platyzoans remain uncertain at the moment, several tentative conclusions can be drawn (Halanych, 2004; Jenner, 2004b; Funch et al., 2005). The acanthocephalans or spiny-headed worms are generally small endoparasites (not more than a few millimeters, although one species of up to 80 cm is known) that derive their name from the possession of a spiny proboscis with which they attach inside their host. Terms and Conditions, [14]). 1982, 472: 1-19. Mol Phylogenet Evol. Also, the larger guts needed for processing leaves are costly to maintain and transport, and even more costly to transport when filled with slowly digesting bulky foods. The family Pseudochromidae (represented by Labracinus cyclophthalma, underlined in Fig. Thus, what originally began with a ventilatory function eventually became utilized for suction feeding, indicating that the current use in feeding is an exaptation. Nevertheless, there is a growing body of evidence that nonadaptive mechanisms, or at least mechanisms not directly under natural selective pressures, may be responsible for a large part of the cladogenesis. R.A. Jenner, in Evolution of Nervous Systems, 2007. 2002, Orlando: Academic Press, 33-55. An adaptation in some teleost fishes is the development of a second set of jaws known as pharyngeal jaws, which develop from visceral arch elements that support the gills in other fishes (see footnote A in Chapter 2 for the four terms visceral arches, pharyngeal arches, branchial arches and gill arches). The widely-accepted taxonomic hypothesis (monophyletic Labroidei) assumed that the evolution of the specialized PJA occurred only once during the percomorph evolution, a situation that has prevented the famous evolutionary example from being examined from the aspect of historical repeatability. Google Scholar. It will be worthwhile to study the molecular mechanisms underlying the morphological modifications, which would reveal molecular basis for the probable key innovations. They provide no unambiguous support for the monophyly of Gnathifera. Mol Phylogenet Evol. The evidence supporting this includes the fact that most of the elements of the jaws (skeletal elements, muscles, etc.) The resultant phylogenies indicated that the Labridae and the remaining three labroid families have diverged basally within the Percomorpha, and monophyly of the suborder was confidently rejected by statistical tests using Bayes factors. In labrids, eg, mollusks are crushed between the pharyngeal teeth and the shell fragments ejected from the mouth before the soft parts are swallowed. In these latter dentitions, shape and increased complexity (e.g., size, curvature, multiple cusps) arise through the process of replacement. PubMed Google Scholar. Schluter D: The ecology of adaptive radiation. Syst Biol. Boll Mus Civ di St Nat Verona. Maddison DR, Maddison WP: MACCLADE: Analysis of Phylogeny and Character Evolution, version 4.03. An interesting exception among birds is geese, which are both folivorous and exceptionally strong flyers. That is to say, although the present phylogeny demonstrated that the three labroid families, Cichlidae, Pomacentridae, and Embiotocidae, formed a well-supported monophyletic group (clade B) without non-labroid taxa, there remains a possibility that some non-labroid taxa would break into the group when more extensive taxon sampling is conducted. Hulsey et al. 2004, 31: 351-362. pharyngeal jaw functional morphology would provide a basis for investigating several questions regarding the evolutionary origin and significance of this specialization in the diversification of teleost fishes. At the one extreme are cytoplasm consumers, which avoid dietary fiber through selective feeding (e.g., Figure 1(n)), or else eat large amounts of fibrous plants and selectively assimilate the cell contents while defecating the tough cell wall components more or less intact (e.g., the giant panda, Figure 1(o)). MrBayes unnecessarily estimated transitional changes (A ↔ G or C ↔ T) when RY-coding was employed, which simply imposed fixed nucleotide compositions on R (A + G) and Y (C + T) during the calculation. Miya M, Takeshima H, Endo H, Ishiguro NB, Inoue JG, Mukai T, Satoh TP, Yamaguchi M, Kawaguchi A, Mabuchi K, Shirai SM, Nishida M: Major patterns of higher teleostean phylogenies: a new perspective based on 100 complete mitochondrial DNA sequences. Mol Phylogenet Evol. Inoue JG, Miya M, Tsukamoto K, Nishida M: Complete mitochondrial DNA sequence of the Japanese anchovy, Engraulis japonicus. The first hypothesis for the origins of jaws is the neoclassical hypothesis, which asserts that the jaw first evolved for stronger ventilation and then to grasp prey. Bellwood DR: A new Eocene fossil fish, Sorbinia caudopunctata Gen. et Sp. Although minimally proposed to include platyhelminths, gnathostomulids, rotifers, and acanthocephalans, the broadest definition of this clade additionally includes entoprocts, cycliophorans, and micrognathozoans, and potentially gastrotrichs and myzostomids. In cichlid fish, the presence of additional pharyngeal jaws has been cited as possible reasons for the unusual plasticity of head morphologies in this group. CAS  jaw evolution. We also thank the following individuals and institutions for their help in collecting the specimens: J. Paxton, M. McGrouther, T. Mukai, and Iriomote Station, Tropical Biosphere Research Center, University of the Ryukyus. Löytynoja A, Milinkovitch MC: A hidden Markov model for progressive multiple alignment. Most fish gill arches already have muscle attachments that aid in swallowing and breathing. Diet quality varies not only between herbivores and carnivores, but also within these groups. Development and resorption of bone and cartilage of the lower jaws associated with tooth development was analysed using transmission electron and light microscopy18. [42]) so as to amplify the entire mitogenome in two reactions. In that case, their conservation is of more than local relevance. Large guts ease the limit on the rate of consumption by herbivores, and help to compensate for the low digestibility of plants by increasing the time that food is exposed to digestive enzymes and absorptive tissue of the gut. Finally, the strategies of digestion are sometimes classified using chemical reactor theory. Numerals beside internal branches indicate Bayesian posterior probabilities (PPs) (shown as percentages) for dataset #1/#2/#3. Very few birds (3% of living species) eat leaves, probably because birds have a high metabolic rate, and hence higher energetic requirements than can readily be satisfied by a poor-quality diet. Sharks and rays exhibit teeth (often in multiple rows) or tooth plates on their cartilaginous oral jaws, and mammalian teeth are confined to a single row at the oral jaw margin. The first four arches still function as gills. Speciation is associated with adaptations for specialised feeding, with the scales of some species even serving as a source of food for other cichlids. In more advanced actinopterygians, the pharyngeal jaws take on the main role in processing food in addition to transport. 1993, 2: 158-165. Interestingly, evolutionary radiations in jaw forms and head shape (see Fig. Specialization can also be a verb, the evolutionary process of becoming more specialized. 2005, 85: 289-306. According to Stiassny & Jensen [12], the specialized PJA has seven morphological features including the above three major ones. Pharyngeal jaws allow the ‘regular’ jaws to specialise for prey capture, the pharyngeal jaws doing the breaking up of food. [18], except for the newly added fishes, such as labroids. Neoendemics should not easily leave the cradle in which they originated, otherwise they would acquire a wide distribution and cease to be endemics. Zebrafish. Moreover, there is no independent, corroborative evidence for a monophyletic Labroidei outside of the specialized PJA [12, 13]. WIC is the average variance of prey sizes found within individuals’ diets, whereas BIC is the variation between individuals. 1996, 117: 159-174. 1996, 9: 641-670. Figure 4.7. 2000, Oxford: Oxford University Press. Johan Nylander. 2002, 51: 917-929. The quantity–quality framework has also helped to make sense of differences in the distributions of feeding types among birds and mammals. First, extant endemic diversity is higher in the littoral than in the sublittoral or in the pelagic of the East African lakes (the deeper waters of the African lakes, below ca. These studies reveal a surprising and long-lasting plasticity between dental and sensory organs that spans the continuum of craniofacial organ patterning and regeneration. 1994, 369: 684-685. In a series of studies Anker (*1989) described in some detail, the morphology of the cichlid head skeleton, including joints and presence of cartilage grading into bone in the hyoid, branchial basket and jaw skeletons of Astatotilapia elegans; three stages in the development of the mandibular joint in another teleost, the Japanese medaka Oryzias latipes, are illustrated in Figure 1.9. nov., from Monte Bolca, Italy. Topological differences among results from the three datasets were shown only in the trichotomy and five internal branches denoted by arrowheads in Fig. 2001, 67: 474-481. Our analysis used the whole mitochondrial genome sequences (>13,000 bp per species), and confirmed the independent origins of the two diversified families by statistical tests using Bayes factors. In this study, we combined an analysis of functional diversity among … According to Stiassny & Jensen [12], typical labroid PJA has seven features (three of them shown in Fig. Hulsey CD: Function of a key morphological innovation: fusion of the cichlid pharyngeal jaw. As ventilation increases, prey would be sucked in and potentially consumed. members of Beloniformes), will shed light on overlooked evolutionary implications. Figure 1. resemble those of other branchial arches. A whole series of potential intrinsic factors that could cause or allow rapid speciation in particular animal groups have been proposed. The ND6 gene was also excluded because of its heterogeneous base composition and consistently poor phylogenetic performance [17]. Platyzoa encompasses noncoelomate lophotrochozoans. This transition was marked by major changes to the structure of the pharynx, including the evolution of a robust pharyngeal skeleton composed of cellular cartilage.
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