ISSN:0006-8977    

DOI:10.1159/000113331

出版商:S. Karger AG    

年代:1997

数据来源: Karger

ISSN:0006-8977    

DOI:10.1159/000113332

出版商:S. Karger AG    

年代:1997

数据来源: Karger

摘要:

Sensory receptor evolution is a function of the array of events in the physical world that are detectable by biological systems. Examples of both conservation and innovation occur across vertebrates in the organization of sensory systems for the reception of photic, positional, chemical, tactile, mechanosensory and electrosensory lateral line, acoustic, and magnetic stimuli. Recent findings in genetics and ontogeny allow new approaches to questions of how new sensory receptors and their corresponding central nervous system pathways evolve, how sensory specialization arises and its effects on other sensory systems, the role of cell-adhesion molecules in the ontogeny of sensory pathways and their topological organization, and the occurrence of reorganization and co-option of developmental modules over sensory system evolution. Relatively simple alterations at the genetic and ontogenetic levels often can result in alterations in the phenotype of far greater complexity.

ISSN:0006-8977    

DOI:10.1159/000113333

出版商:S. Karger AG    

年代:1997

数据来源: Karger

摘要:

In the earliest tetrapods, the fenestra vestibuli was a large hole in the braincase wall bounded by bones of different embryological origins: the otic capsule and occipital arch components, and also, in all except the Devonian Acanthostega, the dermal parasphenoid. This means that the hole lay along the line of the embryonic metotic fissure. Early tetrapod braincases were poorly ossified internally, and no specialized opening for a perilymphatic duct is evident. It is arguable that the earliest tetrapods had neither a perilymphatic duct crossing the otic capsule nor a specialized auditory receptor in a separate lagenar pouch. The primitive tetrapod condition is found in the earliest amniotes, and the separate development of (1) a fenestra vestibuli confined to the limits of the otic capsule, (2) a specialized pressure relief window also derived from components on the line of the metotic fissure, (3) a nonstructural, vibratory stapes and (4) increased internal ossification of the internal walls of the otic capsule, can be traced separately in synapsids, lepidosauromorph diapsids, archosauromorph diapsids, probably turtles, and amphibians. This suggests separate development of true tympanic ears in each of these groups. Developments indicating the existence of a true tympanic ear in amniotes are first found in animals from the Triassic period, and a correlation with the evolution of insect sound production is suggested.

ISSN:0006-8977    

DOI:10.1159/000113334

出版商:S. Karger AG    

年代:1997

数据来源: Karger

摘要:

The ear appears to have arisen early in the evolution of the vertebrates. While there are significant interspecific differences in ear structure, it appears that receptor cell structure and the basic function of the ear and auditory system are similar among all vertebrate groups. In this paper we present the evolution of the sensory hair cells of the ear, the origins of the ear itself, and selected functions of the sense of hearing. We argue that there have been strong selective pressures in most vertebrate groups for the sorts of sound encoding and processing abilities that result in the efficient detection, localization, and identification of sound sources in noisy environments. Many of the encoding and processing strategies underlying these functions are shared as well.

ISSN:0006-8977    

DOI:10.1159/000113335

出版商:S. Karger AG    

年代:1997

数据来源: Karger

摘要:

The general features of the olfactory system are remarkably consistent across vertebrates. A phylogenetic analysis of central olfactory projections indicates that at least three distinct olfactory subsystems may be broadly present in vertebrates and that a fourth, the accessory olfactory or vomeronasal system, arose in tetrapods. The origin and function of the vomeronasal system have been the subject of much controversy, but some conclusions can be drawn. The vomeronasal system did not arise as an adaptation to terrestrial life, as indicated by the presence of a vomeronasal system in modern aquatic amphibians and the increasing paleontological evidence that the last common ancestor of amphibians and amniotes was aquatic. The vomeronasal system is involved in both foraging and reproductive behaviors in reptiles and has been shown to be involved in some pheromonally mediated behaviors in mammals. However, among mammals, some pheromonal responses are not mediated by the vomeronasal system, and the possible involvement of the vomeronasal system in other types of behaviors has not yet been investigated. Thus, the relative functions of the olfactory and vomeronasal systems of tetrapods remain unclear. Other hypotheses that features of the olfactory system are specialized for aquatic chemoreception or for pheromone detection are similarly insupportable. For example, the suggestion that members of the olfactory receptor family can be separated into two groups that function for transduction of air-borne or water-borne odorants is contradicted by the presence of both groups in aquatic amphibians and by a phylogenetic analysis of the sequences for these genes. Interestingly, the putative odorant receptors from the vomeronasal epithelium share little sequence similarity with those from the olfactory epithelium, indicating that these receptors may have been independently co-opted from the larger family of seven transmembrane domain receptors for use in odor transduction. A phylogenetic analysis of the distribution of olfactory receptor cell types indicates that microvillar olfactory receptor cells are widespread among vertebrates and are not restricted to aquatic animals or to the vomeronasal epithelium of tetrapods. Previous suggestions that all microvillar receptor cells are specialized for the detection of pheromones are not tenable. Attempts to recognize features of the olfactory system that are common to all vertebrates and might be specialized for the detection of pheromones vs. more general odorants, or for the detection of water-borne vs. air-borne odorants, are not supported by current evidence.

ISSN:0006-8977    

DOI:10.1159/000113336

出版商:S. Karger AG    

年代:1997

数据来源: Karger

摘要:

Vertebrates possess four distinct chemosensory systems distinguishable on the basis of structure, innervation and utilization: olfaction, taste, solitary chemoreceptor cells (SCC) and the common chemical sense (free nerve endings). Of these, taste and the SCC sense rely on secondary receptor cells situated in the epidermis and synapsing on sensory nerve fibers innervating them near their base. The SCC sense occurs in anamniote aquatic craniates, including hagfish, and may be used for feeding or predator avoidance. The sense of taste occurs only in vertebrates and is always utilized for feeding. The SCC system achieves a high degree of specialization in two teleosts: sea robins (Prionotus) and rocklings (Ciliata). In sea robins, SCCs are abundant on the three anterior fin rays of the pectoral fin which are free of fin webbing and are used in active exploration of the substrate. Behavioral and physiological studies show that this SCC system responds to feeding cues and drives feeding behavior. It is connected centrally like a somatosensory system. In contrast, the specialized SCC system of rocklings occurs on the anterior dorsal fin which actively samples the surrounding water. This system responds to mucus substances and may serve as a predator detector. The SCC system in rocklings is connected centrally like a gustatory system. Taste buds contain multiple receptor cell types, including a serotonergic Merkel-like cell. Taste receptor cells respond to nutritionally relevant substances. Due to similarities between SCCs and one type of taste receptor cell, the suggestion is made that taste buds may be compound sensory organs that include some cells related to SCCs and others related to cutaneous Merkel cells. The lack of taste buds in hagfish and their presence in all vertebrates may indicate that the phylogenetic development of taste buds coincided with the elaboration of head structures at the craniate-vertebrate transition.

ISSN:0006-8977    

DOI:10.1159/000113337

出版商:S. Karger AG    

年代:1997

数据来源: Karger

摘要:

Sensory systems that detect weak electric fields initially evolved as a primitive vertebrate character and have subsequently been lost and ‘re-evolved’ a number of times in various taxa. As such, they provide unique examples of evolutionary parallelism and convergence in vertebrate sensory systems. Electrosensory systems have additionally proven to be admirable models for investigating the fundamental strategies by which nervous systems interpret environmental signals as the basis for organizing behavi

ISSN:0006-8977    

DOI:10.1159/000113338

出版商:S. Karger AG    

年代:1997

数据来源: Karger

摘要:

Eyes are the preeminent source of sensory information for the brain in most species, and many features of eyes reflect evolutionary solutions to particular selective pressures, both from the nonbiological environment and from other animals. As a result, the evolution of eyes, among all the sense organs, has attracted considerable attention from scientists. Paired eyes in the three major phyla, vertebrates, arthropods and mollusks, have long been considered to be classic examples of evolutionary convergence. At the macroscopic level, this must be true since they arise from different tissues and have evolved radically different solutions to the common problem of collecting and focusing light. However, opsin, the light-absorbing receptor protein, has a significant amount of shared DNA sequence homology across the phyla, and recently it has been discovered that some part of ocular development in different phyla is coordinated by a homologous gene, Pax-6. So, although eyes from diverse phyla are clearly not homologous, neither can they be viewed as resulting solely from convergence. Instead, this shows that homology at the molecular level of organization does not predict homology at the organ or organismic level. The presence of homologous constituent molecules in nonhomologous structures reminds us that molecules are not eyes.

ISSN:0006-8977    

DOI:10.1159/000113339

出版商:S. Karger AG    

年代:1997

数据来源: Karger

ISSN:0006-8977    

DOI:10.1159/000113340

出版商:S. Karger AG    

年代:1997

数据来源: Karger