Type 2 vomeronasal receptor expression in the olfactory organ of African lungfish, Protopterus annectens.

The olfactory organ of tetrapods, with few exceptions, comprises the main and accessory organs: olfactory epithelium (OE) and vomeronasal organ (VNO). Unlike tetrapods, teleost fish lack a VNO. However, lungfish, a type of sarcopterygian fish closely related to tetrapods, possesses a lamellar OE similar to the OE of teleosts and a recess epithelium (RecE) resembling the amphibian VNO.

Severe Bottleneck Impacted the Genomic Structure of Egg-Eating Cichlids in Lake Victoria.

Within 15,000 years, the explosive adaptive radiation of haplochromine cichlids in Lake Victoria, East Africa, generated 500 endemic species. In the 1980s, the upsurge of Nile perch, a carnivorous fish artificially introduced to the lake, drove the extinction of more than 200 endemic cichlids. The Nile perch predation particularly harmed piscivorous cichlids, including paedophages, cichlids eat eggs and fries, which is an example of the unique trophic adaptation seen in African cichlids.

Localized Expression of Olfactory Receptor Genes in the Olfactory Organ of Common Minke Whales.

Baleen whales (Mysticeti) possess the necessary anatomical structures and genetic elements for olfaction. Nevertheless, the gene () repertoire has undergone substantial degeneration in the cetacean lineage following the divergence of the Artiodactyla and Cetacea. The functionality of highly degenerated mysticete s within their olfactory epithelium remains unknown.

In situ hybridization analysis of odorant receptor expression in the olfactory organ of the pig-nosed turtle Carettochelys insculpta.

The turtle olfactory organ consists of upper (UCE) and lower (LCE) chamber epithelium, which send axons to the ventral and dorsal portions of the olfactory bulbs, respectively. Generally, the UCE is associated with glands and contains ciliated olfactory receptor neurons (ORNs), while the LCE is devoid of glands and contains microvillous ORNs. However, the olfactory organ of the pig-nosed turtle Carettochelys insculpta appears to be a single olfactory system morphologically: there are no associated glands; ciliated ORNs are distributed throughout the olfactory organ; and the olfactory bulb is not divided into ventral and dorsal portions.

Expression of type 1 vomeronasal receptors in the olfactory organ of the African lungfish, Protopterus dolloi.

The vomeronasal organ is an olfactory organ found in amphibians and higher vertebrates. Type 1 vomeronasal receptors, one of the major olfactory receptors in vertebrates, are expressed in the vomeronasal organ in mammals. In amphibians and fish, they are expressed in the olfactory epithelium.

Plastic loss of motile cilia in the gills of in response to high CO or terrestrial environments.

The evolutionary transition of vertebrates from water to land during the Devonian period was accompanied by major changes in animal respiratory systems in terms of physiology and morphology. Indeed, the fossil record of the early tetrapods has revealed the existence of internal gills, which are vestigial fish-like traits used underwater. However, the fossil record provides only limited data on the process of the evolutionary transition of gills from fish to early tetrapods.

Type 1 vomeronasal receptor expression in juvenile and adult lungfish olfactory organ.

Lungfish are the most closely related fish to tetrapods. The olfactory organ of lungfish contains lamellae and abundant recesses at the base of lamellae. Based on the ultrastructural and histochemical characteristics, the lamellar olfactory epithelium (OE), covering the surface of lamellae, and the recess epithelium, contained in the recesses, are thought to correspond to the OE of teleosts and the vomeronasal organ (VNO) of tetrapods.

c-fos expression in the olfactory epithelium of the East African cichlid (Haplochromis chilotes) in response to odorant exposure.

Fishes use olfaction to gain varied information vital for survival and communication. To understand biodiversity in fishes, it is important to identify what receptors individual fish use to detect specific chemical compounds. However, studies of fish olfactory receptors and their ligands are still limited to a few model organisms represented primarily by zebrafish.

Type 1 vomeronasal receptors expressed in the olfactory organs of two African lungfish, Protopterus annectens and Protopterus amphibius.

Lungfish are the fish related most closely to tetrapods. The olfactory organ of lungfish contains two distinct sensory epithelia: the lamellar olfactory epithelium (OE) and the recess epithelium (RecE). Based on their ultrastructural and histological characteristics, the lamellar OE and the RecE are considered to correspond respectively to the teleost OE and a primitive vomeronasal organ (VNO).

SINEs as Credible Signs to Prove Common Ancestry in the Tree of Life: A Brief Review of Pioneering Case Studies in Retroposon Systematics.

Currently, the insertions of SINEs (and other retrotransposed elements) are regarded as one of the most reliable synapomorphies in molecular systematics. The methodological mainstream of molecular systematics is the calculation of nucleotide (or amino acid) sequence divergences under a suitable substitution model. In contrast, SINE insertion analysis does not require any complex model because SINE insertions are unidirectional and irreversible.

Alternative splicing plays key roles in response to stress across different stages of fighting in the fish Betta splendens.

Background: Aggression is an evolutionarily conserved behavior critical for animal survival. In the fish Betta splendens, across different stages of fighting interactions, fighting opponents suffer from various stressors, especially from the great demand for oxygen. Using RNA sequencing, we profiled differential alternative splicing (DAS) events in the brains of fish collected before fighting, during fighting, and after fighting to study the involvement of alternative splicing (AS) in the response to stress during the fight.

New Sex Chromosomes in Lake Victoria Cichlid Fishes (Cichlidae: Haplochromini).

African cichlid fishes harbor an extraordinary diversity of sex-chromosome systems. Within just one lineage, the tribe Haplochromini, at least 6 unique sex-chromosome systems have been identified. Here we focus on characterizing sex chromosomes in cichlids from the Lake Victoria basin.

Remarkable diversity of vomeronasal type 2 receptor (OlfC) genes of basal ray-finned fish and its evolutionary trajectory in jawed vertebrates.

The vomeronasal type 2 receptor (V2R, also called OlfC) multigene family is found in a broad range of jawed vertebrates from cartilaginous fish to tetrapods. V2Rs encode receptors for food-related amino acids in teleost fish, whereas for peptide pheromones in mammals. In addition, V2Rs of teleost fish are phylogenetically distinct from those of tetrapods, implying a drastic change in the V2R repertoire during terrestrial adaptation.

A transcriptomic reevaluation of the accessory olfactory organ in Bichir (Polypterus senegalus).

Fish possess one olfactory organ called the olfactory epithelium (OE), by which various chemical substances are detected. On the other hand, tetrapods possess two independent olfactory organs called the main olfactory epithelium (MOE) and vomeronasal organ (VNO), each of which mainly detects general odorants and pheromones, respectively. Traditionally, the VNO, so-called concentrations of vomeronasal neurons, was believed to have originated in tetrapods.

Genomic Signatures for Species-Specific Adaptation in Lake Victoria Cichlids Derived from Large-Scale Standing Genetic Variation.

The cichlids of Lake Victoria are a textbook example of adaptive radiation, as >500 endemic species arose in just 14,600 years. The degree of genetic differentiation among species is very low due to the short period of time after the radiation, which allows us to ascertain highly differentiated genes that are strong candidates for driving speciation and adaptation. Previous studies have revealed the critical contribution of vision to speciation by showing the existence of highly differentiated alleles in the visual opsin gene among species with different habitat depths.

Platypus and echidna genomes reveal mammalian biology and evolution.

Egg-laying mammals (monotremes) are the only extant mammalian outgroup to therians (marsupial and eutherian animals) and provide key insights into mammalian evolution. Here we generate and analyse reference genomes of the platypus (Ornithorhynchus anatinus) and echidna (Tachyglossus aculeatus), which represent the only two extant monotreme lineages. The nearly complete platypus genome assembly has anchored almost the entire genome onto chromosomes, markedly improving the genome continuity and gene annotation.

Conserved keratin gene clusters in ancient fish: An evolutionary seed for terrestrial adaptation.

Type I and type II keratins are subgroups of intermediate filament proteins that provide toughness to the epidermis and protect it from water loss. In terrestrial vertebrates, the keratin genes form two major clusters, clusters 1 and 2, each of which is dominated by type I and II keratin genes. By contrast, such clusters are not observed in teleost fish.

Comparative genomic analyses illuminate the distinct evolution of megabats within Chiroptera.

The revision of the sub-order Microchiroptera is one of the most intriguing outcomes in recent mammalian molecular phylogeny. The unexpected sister-taxon relationship between rhinolophoid microbats and megabats, with the exclusion of other microbats, suggests that megabats arose in a relatively short period of time from a microbat-like ancestor. In order to understand the genetic mechanism underlying adaptive evolution in megabats, we determined the whole-genome sequences of two rousette megabats, Leschenault's rousette (Rousettus leschenaultia) and the Egyptian fruit bat (R.

Inactivation of ancV1R as a Predictive Signature for the Loss of Vomeronasal System in Mammals.

The vomeronasal organ (VNO) plays a key role in sensing pheromonal cues, which elicits social and reproductive behaviors. Although the VNO is highly conserved across mammals, it has been lost in some species that have evolved alternate sensing systems during diversification. In this study, we investigate a newly identified VNO-specific gene, ancV1R, in the extant 261 species of mammals to examine the correlation between genotype (ancV1R) and phenotype (VNO).