Distribution of coccidians (Sporozoa: Coccidiida) in various systematic groups of fishes

There are about 250 coccidian species associated with fishes. They belong to 8 genera (Calyptospora, Cryptosporidium, Crystallospora, Eimeria, Epieimeria, Goussia, Isospora, Octosporella) and 3 families (Calyptosporidae, Cryptosporidiidae, Eimeriidae). Two genera are represented by great number of species associated with fishes: Eimeria--157 and Goussia--69 species. Most diverse fauna of coccidians was found in fishes of the class Actinopterigii; fishes of the class Elasmobranchii have significantly less number of coccidians. These parasites have never been recorded on the class Holocephali. Coccidian have been recorded in 55 orders of fishes. Within the Actinopterigii, the richest coccidian fauna is recorded from Cypriniformes and Perciformes. Accumulated data on host associations proves that coccidian species have mainly a restricted hosts specificity.     

The Covert World of Fish Biofluorescence: A Phylogenetically Widespread and Phenotypically Variable Phenomenon

The discovery of fluorescent proteins has revolutionized experimental biology. Whereas the majority of fluorescent proteins have been identified from cnidarians, recently several fluorescent proteins have been isolated across the animal tree of life. Here we show that biofluorescence is not only phylogenetically widespread, but is also phenotypically variable across both cartilaginous and bony fishes, highlighting its evolutionary history and the possibility for discovery of numerous novel fluorescent proteins. Fish biofluorescence is especially common and morphologically variable in cryptically patterned coral-reef lineages. We identified 16 orders, 50 families, 105 genera, and more than 180 species of biofluorescent fishes. We have also reconstructed our current understanding of the phylogenetic distribution of biofluorescence for ray-finned fishes. The presence of yellow long-pass intraocular filters in many biofluorescent fish lineages and the substantive color vision capabilities of coral-reef fishes suggest that they are capable of detecting fluoresced light. We present species-specific emission patterns among closely related species, indicating that biofluorescence potentially functions in intraspecific communication and evidence that fluorescence can be used for camouflage. This research provides insight into the distribution, evolution, and phenotypic variability of biofluorescence in marine lineages and examines the role this variation may play.     

Importance of live coral habitat for reef fishes

Live corals are the key habitat forming organisms on coral reefs, contributing to both biological and physical structure. Understanding the importance of corals for reef fishes is, however, restricted to a few key families of fishes, whereas it is likely that a vast number of fish species will be adversely affected by the loss of live corals. This study used data from published literature together with independent field based surveys to quantify the range of reef fish species that use live coral habitats. A total of 320 species from 39 families use live coral habitats, accounting for approximately 8 % of all reef fishes. Many of the fishes reported to use live corals are from the families Pomacentridae (68 spp.) and Gobiidae (44 spp.) and most (66 %) are either planktivores or omnivores. 126 species of fish associate with corals as juveniles, although many of these fishes have no apparent affiliation with coral as adults, suggesting an ontogenetic shift in coral reliance. Collectively, reef fishes have been reported to use at least 93 species of coral, mainly from the genus Acropora and Porities and associate predominantly with branching growth forms. Some fish associate with a single coral species, whilst others can be found on more than 20 different species of coral indicating there is considerable variation in habitat specialisation among coral associated fish species. The large number of fishes that rely on coral highlights that habitat degradation and coral loss will have significant consequences for biodiversity and productivity of reef fish assemblages.     

Lower sensitivity of cyprinid fishes to three acetylcholinesterase inhibitor pesticides: an evaluation based on no-effect concentrations

Researchers have suggested that cyprinid fishes are less sensitive to chemical stress than comparable fish families, yet few empirically based evaluations of this hypothesis have been conducted. In this study, we developed a generalized linear mixed model in which the no-effect concentrations (NECs; threshold concentration below which no effect on survival is predicted during prolonged exposure) of 29 fish species from 13 families exposed to an acetylcholinesterase inhibitor pesticide (carbaryl, chlorpyrifos, or malathion) were used as the response variable. The corresponding specific somatic maintenance (SSM) rates, as a size-independent proxy for fish metabolism and a categorical variable regarding whether the species is a cyprinid, were used as the predictor variables. We included SSM rates in the analysis because previous work demonstrated that they are negatively correlated with NECs. Our results indicate that the NECs for cyprinid fishes were significantly higher than those for other fishes, suggesting that cyprinids are indeed less sensitive to the three studied pesticides. Although the SSM rates were negatively related with the NECs, the actual relationship between the two was not clear, implying that the importance of SSM rates may depend on the taxonomic group tested.     

Parental care in the rocky intertidal: a case study of adaptation and exaptation in Mediterranean and Atlantic blennies

Summary The main features of the behavioural ecology of rocky intertidal species are compared both within families — though concentrated on blennies — and between habitats. It is suggested that, at the behavioural level, the reduction of vertical and swimming elements in the male sexual and agonistic displays of Blennioidei may constitute an adaptation to typical intertidal conditions, especially in those species that inhabit areas exposed to strong wave action. The other aspect which is discussed is the prevalence of parental care in rocky intertidal fishes. In these fishes parental care is much more frequent than for marine fishes as a whole. Taken alone, this could also suggest that guarding evolved as an adaptation during the process of colonization of these habitats. The hypothesis proposed in this paper is that guarding was already present in the ancestors of the resident species, at least in the majority of cases. Many differences in interhabitat studies may express the action of the environment, not as an agent of natural selection, but as a filter, which prevented some groups from invading a given habitat and, at the same time, made colonization easier for other groups. When a number of taxa that colonized a given habitat display clear similarities in their behaviour and their biology, adaptation is not necessarily demonstrated. There is evidence in the literature to support the hypothesis that those traits were already present in the ancestors of the rocky intertidal resident fishes, thus being best viewed as exaptations.     

Evolutionary patterns in tropical marine reef fish feeding

The majority of tropical reef fishes are acanthopterygians. Most of them are percomorphs and thus are likely monophyletic. In accordance to modern systematics, the primitive types among the latter are large-mouthed suction feeders. Species from advanced families often have biting oral jaws with a reduced number and complexly shaped teeth. Mouth sizes decrease from the primitive towards the advanced reef fishes when ranked according to increasing family numbers (Nelson 1984). To create a functional resource axis, Randall's (1967) and Hobson's (1974) data on tropical reef fish feeding were re-interpreted by ranking food items from mobile to sessile prey. The primitive paracantho pterygian and acanthopterygian reef fishes are large-mouthed, suction-feeding predators on mobile prey. Most of the advanced, small-mouthed species are browsers and grazers, but often feed on mobile prey too. Obligatory specialists (monophagous and unable to switch) seem to be relatively rare among modern reef fishes. The trends stated above indicate a wealth of parallel developments in many advanced families of reef fishes towards small, often biting oral jaws. This parallelism may be the result of comparable regimes of selection pressures in reefs and of the need for newly evolved species to establish themselves within the already existing guilds.     

The evolution of diadromy in fishes (revisited) and its place in phylogenetic analysis

Diadromy is a term used to describe migrations of fishes between fresh waters and the sea; these migrations are regular, physiologically mediated movements which occur at predictable life history phases in each diadromous species, they involve most members of a species' populations, and they are usually obligatory. Around 250 fish species are regarded as diadromous. A review of the life history strategies amongst families of fishes that include diadromous species provides little support for a suggested scenario for their evolution that involves: (1) evolution of anadromy via amphidromy from fishes of marine origins, and (2) evolution of catadromy through amphidromy from fishes of freshwater origins, even though these scenarios seem intuitively reasonable. The various forms of diadromy appear to have had multiple independent origins amongst diverse fish groups. There is increasing confidence that behavioural characteristics of animals are heuristic in gener ating and interpreting phylogenies. However, examination of fishes shows wide variability of diadromous life histories within closely related families and genera, within species, and there is even ontogenetic variation in patterns of behaviour by individual fish. In addition, there is multiple loss of diadromy in many diadromous fish species in which the life history becomes restricted to fresh waters. This variation suggests that diadromy is a behavioural character of dubious worth in determining phylogenetic relationships. Moreover, it appears to have been an ancestral condition in some fish families, such as Anguillidae, Salmonidae, Galaxiidae, Osmeridae, and others, and perhaps in the whole salmonoid/osmeroid/galaxioid complex of families. This, too, makes diadromy of dubious worth in phylogenetic analysis     

How Nemo finds home: the neuroecology of dispersal and of population connectivity in larvae of marine fishes

Nearly all demersal teleost marine fishes have pelagic larval stages lasting from several days to several weeks, during which time they are subject to dispersal. Fish larvae have considerable swimming abilities, and swim in an oriented manner in the sea. Thus, they can influence their dispersal and thereby, the connectivity of their populations. However, the sensory cues marine fish larvae use for orientation in the pelagic environment remain unclear. We review current understanding of these cues and how sensory abilities of larvae develop and are used to achieve orientation with particular emphasis on coral-reef fishes. The use of sound is best understood; it travels well underwater with little attenuation, and is current-independent but location-dependent, so species that primarily utilize sound for orientation will have location-dependent orientation. Larvae of many species and families can hear over a range of ~100-1000 Hz, and can distinguish among sounds. They can localize sources of sounds, but the means by which they do so is unclear. Larvae can hear during much of their pelagic larval phase, and ontogenetically, hearing sensitivity, and frequency range improve dramatically. Species differ in sensitivity to sound and in the rate of improvement in hearing during ontogeny. Due to large differences among-species within families, no significant differences in hearing sensitivity among families have been identified. Thus, distances over which larvae can detect a given sound vary among species and greatly increase ontogenetically. Olfactory cues are current-dependent and location-dependent, so species that primarily utilize olfactory cues will have location-dependent orientation, but must be able to swim upstream to locate sources of odor. Larvae can detect odors (e.g., predators, conspecifics), during most of their pelagic phase, and at least on small scales, can localize sources of odors in shallow water, although whether they can do this in pelagic environments is unknown. Little is known of the ontogeny of olfactory ability or the range over which larvae can localize sources of odors. Imprinting on an odor has been shown in one species of reef-fish. Celestial cues are current- and location-independent, so species that primarily utilize them will have location-independent orientation that can apply over broad scales. Use of sun compass or polarized light for orientation by fish larvae is implied by some behaviors, but has not been proven. Use of neither magnetic fields nor direction of waves for orientation has been shown in marine fish larvae. We highlight research priorities in this area.     

Variability of the behavioral laterality in Teleostei (Pisces)

Factors causing variability of behavioral laterality in Teleostei are reviewed. The laterality has been revealed in many fish species belonging to various families. The best ever demonstrated example of the laterality is the different use of the right and left eyes when a fish responds to different visual objects. Magnitude and sign of the laterality differ in fishes of different species, gender, and age. Also, an observed laterality depends on how familiar a stimulus is to fishes and what it means to them, as well as their motivational level and various behavioral traits. Therefore, comparisons of the laterality among different fish species should be based on experimental methods that also take into account those behavioral differences among them that are not directly linked to the laterality.     

Parent-touching behavior by young fishes: incidence,function and causation

Synopsis Parent-touching behavior by young fishes occurs in a number of species. Most reports have been from the family Cichlidae, but this may reflect the major concentration of studies on these species. The behavior appears to serve a trophic function in many species, but may also serve to maintain cohesion of family groups, to keep adults in a parental state, or to communicate the motivational state of the young (e.g. fear, hunger). It has been suggested that prolactin may regulate the behavior and epidermal mucus condition in parental fish involved in such behavior, but the evidence is not conclusive. There appear to be similarities between cases of parent-touching as a trophic behavior, and mucus- and/or scale-feeding by cleaning symbionts or predators. Studies of this behavior hold promise for investigating interrelationships between endocrinology and behavior, and ecology and behavior.     

Alarm signals in fishes

Summary the evolutionary questions surrounding alarm signalling remain unresolved, but we should now have a better understanding of the elements that must be considered in the balance sheet. The amplification that may occur in alarm signalling may be a key to understanding its evolution. The benefit to receivers will often go far beyond the response of a few nearby schoolmates over a few minutes, the response that has traditionally been measured. Distant fish may receive the signal by secondary transmission, and individuals that are not even present at the time may learn about predator stimuli through cultural transmission. These effects, such as learned response to predator odour or avoidance of an area, may persist for days or much longer, and work on invertebrates implies that there may be the potential for changes in morphology and life history. Thus one signal, such as release of alarm pheromone, could alter predation risk for many individuals over long periods of time. Anything that increases the total benefit to receivers will affect the evolutionary balance sheet. Increase in number of benefits and beneficiaries of a signal will increase the likelihood that the sender will receive adequate kin-selection benefits to drive the evolution of alarm displays. Likewise, to have many individuals avoiding predation would increase the post-signal benefits, such as reduced predation in the region (Trivers, 1971), to senders that survived.Similarly, anything that decreases the cost or increases the direct benefit to the sender will favour alarm signalling. Alarm signals that do double duty as predator deterrents, or aposematic displays, and distress signals that call in mobbers or secondary predators will have lower net cost than signals that only exist to warn others. It may be common for the sender's display to evolve primarily in response to direct benefits to the sender while the reaction of conspecific receivers is selected by their survival. Selection on receivers that reduces their response threshold will make signalling cheaper for the sender.The variety of life histories and biological adaptations in the fishes, combined with the potential of several different, independently evolved alarm signals should provide many avenues of approach and potential research subjects for examining the evolution of these systems.There have been many interesting effects reported in other groups of animals that may occur in fishes and which would extend both the biological interest of these systems and their generality. I have mentioned the morphological and life cycle responses found in invertebrates. Birds show deceitful alarm signalling (Munn, 1986; Moller, 1988), in which senders give false alarm calls to distract receivers from food or other resources. Audience effects occur in domestic chickens (Marler, 1986); they are more likely to give an alarm call if with a companion than when alone. Vervet monkeys assess the reliability of individual signallers and tend to ignore signals from untrustworthy individuals (Cheney and Seyfarth, 1988). Birds can acquire and transmit the identity of individual predators that prey on their species, in contrast to other individuals of the same predatory species that do not (Conover, 1987).The many effects of alarm signalling that have been documented or proposed in fishes or other organisms indicate that this phenomenon must be taken into account in any examination of foraging tactics or predator-prey interaction or any of the several areas of decision making that could be influenced by information on predation risk. Alarm signalling is probably much more widespread than was previously thought. Alarm pheromones are not just an obscure feature of the ostariophysans, although that group alone includes over 6000 species, but also occur in various forms in darters (150 species), gobies (2000 species), sculpins (300 species) and perhaps others. Distress sounds occur in over 24 families (Myrberg, 1981). Alarm calls occur in at least some holocentrids (60 species) and possibly in cods (only 55 species, but some economic value). Visual alarm signals have been reported in gobies (2000 species) and bioluminescent displays in a batrachoidid (65 species). Yet only a small fraction of fishes have been carefully examined for alarm or distress signalling. If we multiply the range of effects by the number of potential species involved, we have a subject area of some general importance in understanding the interactions between prey and predators.The prime requirement in this field, as in so many others, is for carefully designed studies, particularly in the wild, that take account of the whole suite of possible effects that may occur in alarm signalling. These studies should try to include all the participants in the system, including the predator(s), the signaller, and the various classes of receivers. They should also consider both the ultimate and proximate factors at work in each system. Very often proximate mechanisms can tell us important things about the ultimate factors that may be possible.     

Vulnerability of seamount fish to fishing: fuzzy analysis of life‐history attributes

Despite rather broad definitions, global analysis showed that seamount fishes, particularly seamount‐aggregating fishes, had higher intrinsic vulnerability than other groups of fishes. The pattern was similar when considering only commercially exploited species. Biological characteristics leading to greater vulnerability included a longer life span, later sexual maturation, slower growth and lower natural mortality. The results supported the contention that seamount fishes, especially those that aggregate on seamounts, are highly vulnerable to exploitation and that fishing on seamounts may not be sustainable at current levels and with current methods. A number of seamount populations have already been depleted; more depletion, extirpations, and even species extinctions may follow if fishing on seamounts is not reduced.     

The Problem of Characters Susceptible to Parallel Evolution in Phylogenetic Reconstructions: Suggestion of a Practical Method and Its Application to Cave Animals

We here propose a procedure to treat characters which are susceptible to parallel evolution (in this case, troglomorphisms) as a replacement for the two procedures used so far: to either completely consider or completely disregard these characters. These procedures may lead to one of two opposite errors, respectively, (1) to consider them as true synapomorphies when they are not or (2) to disregard them as true synapomorphies when they are. We suggest herein to recode the characters by splitting each troglomorphic character into as many as the number of taxa which show the given troglomorphic state. For each split character each taxon will have the derived state, while the others will be coded as missing data. We provide three real examples to test our procedure and conclude that it may give results different from those of the other two procedures. This means that our procedure does not repeat the two above "errors." In addition, we believe that the procedure filters the possible biases, resulting in trees in which the troglomorphisms do have phylogenetic signals.     

Diversity in the Monogenea and Digenea: does lifestyle matter?

If the cestodes are excluded, then the parasitic platyhelminths of fishes divide neatly into the external and monoxenous Monogenea and the internal and heteroxenous Digenea. Both groups have apparently had long associations of coevolution, host switching and adaptation with fishes and have become highly successful in their respective habitats. Current estimates of species richness for the two groups suggest that they may be remarkably similar. Here we consider the nature of the diversity of the Monogenea and Digenea of fishes in terms of richness of species and higher taxa to determine what processes may be responsible for observed differences. The Monogenea includes at least two super-genera (Dactylogyrus and Gyrodactylus) each of which has hundreds of species; no comparable genera are found in the Digenea. Possible reasons for this difference include the higher host specificity of monogeneans and their shorter generation time. If allowance is made for the vagaries of taxonomic 'lumping' and 'splitting', then there are probably comparable numbers of families of monogeneans and digeneans in fishes. However, the nature of the families differ profoundly. Richness in higher taxa (families) in the Digenea is explicable in terms of processes that appear to have been unimportant in the Monogenea. Readily identifiable sources of diversity in the Digenea are: recolonisation of fishes by taxa that arose in association with tetrapods; adoption of new sites within hosts; adoption of new diets and feeding mechanisms; adaptations relating to the exploitation of ecologically similar groups of fishes and second intermediate hosts; and adaptations relating to the exploitation of phylogenetic lineages of molluscs. In contrast, most higher- level monogenean diversity (other than that associated with the subclasses) relates principally to morphological specialisation for attachment by the haptor.     

Predators reduce abundance and species richness of coral reef fish recruits via non-selective predation

Predators have important effects on coral reef fish populations, but their effects on community structure have only recently been investigated and are not yet well understood. Here, the effect of predation on the diversity and abundance of young coral reef fishes was experimentally examined in Moorea, French Polynesia. Effects of predators were quantified by monitoring recruitment of fishes onto standardized patch reefs in predator-exclosure cages or uncaged reefs. At the end of the 54-day experiment, recruits were 74% less abundant on reefs exposed to predators than on caged ones, and species richness was 42% lower on reefs exposed to predators. Effects of predators varied somewhat among families, however, rarefaction analysis indicated that predators foraged non-selectively among species. These results indicate that predation can alter diversity of reef fish communities by indiscriminately reducing the abundance of fishes soon after settlement, thereby reducing the number of species present on reefs.     

中国鲀形目鱼类嗅觉器官类型的研究

嗅觉器官是鱼类的一种重要感觉器官,它感受由化学而引起的刺激。各种鱼类的感觉器官是十分不同的,不少学者研究了它的构造及其生理机能。以往对鲀形目鱼的嗅觉器官构造的研究报道甚少,大多注意了它的外鼻孔的形态变化,仅在少数文章(Hora,1975)提到鲀形目鱼的嗅觉器官极不发达。为了弄清它的构造特点,解剖观察了中国鲀形目代表性种类的嗅觉器官,对它们的构造特征进行了比较研究,发现它们在各不同分类阶元有独特的构造。     

The Laterosensory Canal System in Epigean and Subterranean Ituglanis (Siluriformes: Trichomycteridae), With Comments About Troglomorphism and the Phylogeny of the Genus

The laterosensory system is a mechanosensory modality involved in many aspects of fish biology and behavior. Laterosensory perception may be crucial for individual survival, especially in habitats where other sensory modalities are generally useless, such as the permanently aphotic subterranean environment. In the present study, we describe the laterosensory canal system of epigean and subterranean species of the genus Ituglanis (Siluriformes: Trichomycteridae). With seven independent colonizations of the subterranean environment in a limited geographical range coupled with a high diversity of epigean forms, the genus is an excellent model for the study of morphological specialization to hypogean life. The comparison between epigean and subterranean species reveals a trend toward reduction of the laterosensory canal system in the subterranean species, coupled with higher intraspecific variability and asymmetry. This trend is mirrored in other subterranean fishes and in species living in different confined spaces, like the interstitial environment. Therefore, we propose that the reduction of the laterosensory canal system should be regarded as a troglomorphic (= cave‐related) character for subterranean fishes. We also comment about the patterns of the laterosensory canal system in trichomycterids and use the diversity of this system among species of Ituglanis to infer phylogenetic relationships within the genus. J. Morphol. 278:4–28, 2017. ©© 2016 Wiley Periodicals,Inc.     

Placoderm fishes,pharyngeal denticles,and the vertebrate dentition

The correlation of the origin of teeth with jaws in vertebrate history has recently been challenged with an alternative to the canonical view of teeth deriving from separate skin denticles. This alternative proposes that organized denticle whorls on the pharyngeal (gill) arches in the fossil jawless fish Loganellia are precursors to tooth families developing from a dental lamina along the jaw, such as those occurring in sharks, acanthodians, and bony fishes. This not only indicates that homologs of tooth families were present, but also illustrates that they possessed the relevant developmental controls, prior to the evolution of jaws. However, in the Placodermi, a phylogenetically basal group of jawed fishes, the state of pharyngeal denticles is poorly known, tooth whorls are absent, and the presence of teeth homologous to those in extant jawed fishes (Chondrichthyes + Osteichthyes) is controversial. Thus, placoderms would seem to provide little evidence for the early evolution of dentitions, or of denticle whorls, or tooth families, at the base of the clade of jawed fishes. However, organized denticles do occur at the rear of the placoderm gill chamber, but are associated with the postbranchial lamina of the anterior trunkshield, assumed to be part of the dermal cover. Significantly, these denticles have a different organization and morphology relative to the external dermal trunkshield tubercles. We propose that they represent a denticulate part of the visceral skeleton, under the influence of pharyngeal patterning controls comparable to those for pharyngeal denticles in other jawed vertebrates and Loganellia.     

Homology of the Lateral Eyes of Scorpiones: A Six-Ocellus Model

Scorpions possess two types of visual organs, the median and lateral eyes. Both eyes consist of simple ocelli with biconvex lenses that differ in structure and function. There is little variation in the number of median ocelli across the order. Except for a few troglomorphic species in which the median ocelli are absent, all scorpions possess a single pair. In contrast, the number of pairs of lateral ocelli varies from zero to five across Scorpiones and may vary within species. No attempt has been made to homologize lateral ocelli across the order, and their utility in scorpion systematics has been questioned, due to the variation in number. A recent study examined the number of lateral ocelli among various Asian Buthidae C.L. Koch, 1837 and proposed a “five-eye model” for the family. This model has not been examined more broadly within Buthidae, however, nor compared with the patterns of variation observed among other scorpion families. An eyespot, referred to as an accessory lateral eye, situated ventral or posteroventral to the lateral ocelli, has also been reported in some scorpions. Analysis of its structure suggests it serves a nonvisual function. We present the first comparative study of variation in the lateral ocelli across the order Scorpiones, based on examination of a broad range of exemplar species, representing all families, 160 genera (78%), 196 species (9%), and up to 12 individuals per species. We propose a six-ocellus model for Recent scorpions with four accessory ocelli observed in various taxa, homologize the individual ocelli, and correct erroneous counts in the recent literature. We also investigate the presence of the eyespot across scorpions and discover that it is more widespread than previously recognized. Future work should investigate the genetic and developmental mechanisms underlying the formation of the lateral ocelli to test the hypotheses proposed here.