Molecular phylogenetics and evolutionary diversification of labyrinth fishes (Perciformes: Anabantoidei)

Labyrinth fishes (Perciformes: Anabantoidei) are primary freshwater fishes with a disjunct African-Asian distribution that exhibit a wide variety of morphological and behavioral traits. These intrinsic features make them particularly well suited for studying patterns and processes of evolutionary diversification. We reconstructed the first molecular-based phylogenetic hypothesis of anabantoid intrarelationships using both mitochondrial and nuclear nucleotide sequence data to address anabantoid evolution. The mitochondrial data set included the complete cytochrome b, partial 12S rRNA, complete tRNA Val, and partial 16S rRNA genes (3332 bp) of 57 species representing all 19 anabantoid genera. The nuclear data set included the partial RAG1 gene (1494 bp) of 21 representative species. The phylogenetic analyses of a combined (mitochondrial+nuclear) data set recovered almost fully resolved trees at the intrafamily level with different methods of phylogenetic inference. Phylogenetic relationships at this taxonomic level were compared with previous morphology-based hypotheses. In particular, the enigmatic pike-head (Luciocephalus) was confidently placed within the "spiral egg" clade, thus resolving the long-standing controversy on its relative phylogenetic position. The molecular phylogeny was used to study the evolution of the different forms of parental care within the suborder. Our results suggest that the evolution of breeding behavior in anabantoids is highly correlated with phylogeny, and that brood care evolved three times independently from an ancestral free spawning condition without parental care. Ancestral character state reconstructions under maximum parsimony and maximum likelihood further indicated that both bubble nesting and mouthbrooding have evolved recurrently during anabantoid evolution. The new phylogenetic framework was also used to test alternative biogeographic hypotheses that account for the disjunct African-Asian distribution. Molecular divergence time estimates support either a drift vicariance linked to the breakup of Gondwana or Late Mesozoic Early Tertiary dispersal from Africa to Asia or vice versa.     

Ontogenetic features of Luciocephalus (Perciformes, Anabantoidei) with a revised hypothesis of anabantoid intrarelationships

The anatomy of the anabantoid fish Luciocephalus is reinvestigated and the ontogeny of certain character complexes is described for the first time. Luciocephalus possesses the following previously unrecognized or equivocally interpreted anatomical characters: a clearly separate ectopterygoid bone, pharyngeal processes of the basioccipital, a toothless pharyngeal process of the parasphenoid, an infrapharyngobranchial I and an endoskeletal mental ossification. In addition, aspects of the ontogeny of the hyopalatine arch in the belontiids Belontia, Trichogaster and Ctenops are described. Species of these three genera all possess an ectopterygoid bone previously thought to be lacking in the family Belontiidae. The significance of the results for reconstructing interrelationships of the anabantoid families and the phylogenetic position of Luciocephalus is discussed. A revised hypothesis of anabantoid intrarelationships is presented. Four synapomorphic characters indicate that Luciocephalus is more closely related to the Belontiidae (including Osphronemus) rather than forming the sister group of all other anabantoids.     

Morphological and biochemical variations in the gills of 12 aquatic air-breathing anabantoid fish

All fish species in the Anabantoidei suborder are aquatic air-breathing fish. These species have an accessory air-breathing organ, called the labyrinth organ, in the branchial cavity and can engulf air at the surface of the water to assist in gas exchange. It is therefore necessary to examine the extent of gill modification among anabantoid fish species and the potential trade-offs in their function. The experimental hypothesis that we aimed to test is whether anabantoid fishes have both morphological and functional variations in the gills among different species. We examined the gills of 12 species from three families and nine genera of Anabantoidei. Though the sizes of the fourth gill arch in three species of Trichogaster were reduced significantly, not all anabantoid species had morphological and functional variations in the gills. In these three species, the specific enzyme activity and relative protein abundance of Na(+)/K(+)-ATPase were significantly higher in the anterior gills as compared with the posterior gills and the labyrinth organ. The relative abundance of cytosolic carbonic anhydrase, an indicator of gas exchange, was found to be highest in the labyrinth organ. The phylogenetic distribution of the fourth gill's morphological differentiation suggests that these variations are lineage specific, which may imply a phylogenetic influence on gill morphology in anabantoid species.     

Implications of domestication and rearing conditions for the behaviour of cultivated fishes

Farmed fishes are often selectively bred for desirable production traits, such as rapid growth, that brings with them behavioural differences. In addition, the striking differences in the environment experienced by wild and cultured fishes offers considerable scope both for unplanned, natural selection for different inherited behavioural phenotypes and for behavioural differences arising from differential experience. In this paper, the evidence that such processes have produced behavioural differences between wild and cultured fishes is reviewed in relation to feeding, antipredator responses, aggression and reproductive behaviour. The reported findings are discussed in relation to the concept of 'behavioural syndromes', or suites of co‐varying behavioural traits that adapt individuals of the same population to spatial and temporal variation in selection regimes. The implications of the behaviour of cultured fishes for their welfare in production cages, for the environmental impact of escapees on wild stocks and for the success of hatchery‐based restocking programmes are considered. The review inevitably concentrates on salmonids, in which such phenomena have been intensively researched.     

Body shape transformation along a shared axis of anatomical evolution in labyrinth fishes (Anabantoidei)

Major morphological transformations, such as the evolution of elongate body shape in vertebrates, punctuate evolutionary history. A fundamental step in understanding the processes that give rise to such transformations is identification of the underlying anatomical changes. But as we demonstrate in this study, important insights can also be gained by comparing these changes to those that occur in ancestral and closely related lineages. In labyrinth fishes (Anabantoidei), rapid evolution of a highly derived torpedo‐shaped body in the common ancestor of the pikehead (Luciocephalus aura and L. pulcher) occurred primarily through exceptional elongation of the head, with secondary contributions involving reduction in body depth and lengthening of the precaudal vertebral region. This combination of changes aligns closely with the primary axis of anatomical diversification in other anabantoids, revealing that pikehead evolution involved extraordinarily rapid change in structures that were ancestrally labile. Finer‐scale examination of the anatomical components that determine head elongation also shows alignment between the pikehead evolutionary trajectory and the primary axis of cranial diversification in anabantoids, with much higher evolutionary rates leading to the pikehead. Altogether, our results show major morphological transformation stemming from extreme change along a shared morphological axis in labyrinth fishes.     

The Upper Triassic fishes from Polzberg bei Lunz, Austria

Carnian (Upper Triassic) fishes from Polzberg bei Lunz have been known since 1886 but no comprehensive account has been published. Eleven species are described nine of which, Saurichthys calcaratus, Polzbergia brochatus, Peltopleurus dirumptus, Habroichthys gregarius, Nannolepis elegans, Phaidrosoma lunzensis, Elpistoichthys pectinatus, E. striolatus and Pholidophoretes salvus are new, and two others, Thoracopterus niederristi Bronn and Gigantopterus telleri Abel, previously little-known.
New supraspecific taxa defined are:the order Polzbergiiformes, the family Thoracopteridae and the genera Polzbergia, Nannolepis, Phaidrosoma, Elpistoichthys and Pholidophoretes.
Habroichthys, Thoracopterus, Gigantopterus and Nannolepis show an unusual skull-roof pattern and are included in the re-defined order Luganoiiformes.
Two new ichthyokentemids considerably extend the known time-range of this family.
The genus Pholidophoretes is intermediate between the Archaeomenidae Goodrich 1909, and the Pholidophoridae sensu stricto Nybelin 1966.
The Polzberg assemblage was probably mainly marine with a small freshwater contribution; it shows less similarity to the Besano and Raibl assemblages than these do to each other.
The Luganoiiformes are probably, but not certainly, monophyletic; relationships within the order are analyzed and a cladogram constructed.
The Platysiagiformes, Peltopleuriformes, Luganoiiformes and Cephaloxeniformes could all have been derived from a common ancestor at the Perleidus level and are probably offshoots of the perleidid radiation.     

Chromosome numbers, genome sizes, cell volumes and evolution of snake-head fish (family Channidae)

Chromosome number, C-value and cell volume studies were carried out on three species of the genus Channa , viz., C. punctatus, C. striatus and C. gachua . The chromosome number, karyotypic structure and DNA content per cell along with cell volume are reported and described. A series of chromosomal rearrangements are established in three different karyotypes along with polyploidy. Both pericentric inversion and Robertsonian fusion played a major role in chromosome rearrangements. The nuclear DNA content of these three species is within 19-29% of the present-day placental mammals, and is thus lower than the median amount for fishes in general and teleosts in particular. Their lower DNA content suggests that the three species of the family Channidae are highly specialized, and this is supported by their known morphologic, reproductive, behavioural and ecological characteristics.
The evolutionary significance of these chromosomal rearrangements, their origin and their mode of establishment are discussed. A probable phylogenetic model based on karyotype, C-value and chromosomal rearrangements of the genus is presented.     

Behaviour of fish by-catch in the mouth of a crustacean trawl

The behaviour of fish by-catch was recorded and characterized by in situ observations in the mouth of a crustacean trawl using an underwater camera system with artificial light, at depths between 106 and 461 m, along the central coast of Chile. The groups or species studied were rattails (family Macrouridae), Chilean hake Merluccius gayi gayi, sharks (orders Carcharhiniformes and Squaliformes), skates (family Rajidae), flatfishes (genus Hippoglossina) and small benthopelagic and demersal fishes (orders Osmeriformes, Stomiiformes, Gadiformes, Ophidiiformes and Perciformes). The fish behaviour was categorized in terms of (1) position in the water column, (2) initial orientation with respect to the trawl, (3) locomotion and (4) swimming speed with respect to the trawl. Rattails, sharks, skates and flatfishes were passive in response to the trawl and showed similar behavioural patterns, with most fishes observed sitting or touching the bottom with no swimming or other activity. Merluccius gayi gayi was the most active species, displaying a wide combination of behavioural responses when the trawl approached. This species showed several behavioural patterns, mainly characterized by swimming forward at variable speed. A fraction of small bentho-pelagic and demersal fishes also showed an active behaviour but always at lower speed than the trawl. The species-specific differences in behaviour in the mouth of the trawl suggest that improvements at the level of the footrope can be made to reduce by-catch, especially of passive species.     

Developmental cycle of the thorny-headed worm, Acanthocephalus lucii (Echinorhynchidae)]

The organogenesis of Acanthocephalus lucii was followed and its developmental periods established. In the organism of the intermediate host Asellus aquaticus the larva of A. lucii has three developmental stages: acantor, preacantella and acantella. At the average daily temperature of 25 degrees the developmental period from the egg to acantella completes within 19 days, at 22 degrees--in 32 days, at 19 degrees--in 51 days, at 18 degrees--in 60 days, at 15-16 degrees--in 72 days and at 15 degrees--in 89 days. In the intestine of fishes the worms become mature in three weeks after the infection. The excretion of eggs by females into the environment begins in 36-39 days after the worms have reached sexual maturity. The whole development of the worm in the definitive host lasts 57 to 60 days.     

A phylogenetic analysis of egg size,clutch size,spawning mode,adult body size,and latitude in reef fishes

Theoretical treatments of egg size in fishes suggest that constraints on reproductive output should create trade-offs between the size and number of eggs produced per spawn. For marine reef fishes, the observation of distinct reproductive care strategies (demersal guarding, egg scattering, and pelagic spawning) has additionally prompted speculation that these strategies reflect alternative fitness optima with selection on egg size differing by reproductive mode and perhaps latitude. Here, we aggregate data from 278 reef fish species and test whether clutch size, reproductive care, adult body size, and latitudinal bands (i.e., tropical, subtropical, and temperate) predict egg size, using a statistically unified framework that accounts for phylogenetic correlations among traits. We find no inverse relationship between species egg size and clutch size, but rather that egg size differs by reproductive mode (mean volume for demersal eggs = 1.22 mm³, scattered eggs = 0.18 mm³, pelagic eggs = 0.52 mm³) and that clutch size is strongly correlated with adult body size. Larger eggs were found in temperate species compared with tropical species in both demersal guarders and pelagic spawners, but this difference was not strong when accounting for phylogenetic correlations, suggesting that differences in species composition underlies regional differences in egg size. In summary, demersal guarders are generally small fishes with small clutch sizes that produce large eggs. Pelagic spawners and egg scatterers are variable in adult and clutch size. Although pelagic spawned eggs are variable in size, those of scatterers are consistently small.     

Egg size, first instar behaviour and the ecology of Lepidoptera

There is striking variation in egg size among Lepidoptera. Part of the explanation could be a link between egg size and larval feeding ecology.
The relationship between absolute egg size and aspects of feeding ecology for different Lepidoptera families from different temperate regions is examined. Species that overwinter in the egg stage have larger eggs. There are significant differences in egg size with respect to feeding specificity but different families show different patterns. Woody plant feeders have larger eggs than herb feeders. There is little effect of proximity of the egg to the plant part that is eaten.
Patterns in the behaviour and survival of newly hatched larvae of 42 spp. of British Lepidoptera and their relationship to egg and larval size and to food plant characteristics are examined. Patterns in egg size with respect to feeding ecology are similar to those described above. There is a strong correlation between egg size and the size of newly hatched larvae. Newly hatched larvae survived for a mean of 1–20 days without food. Survival is not correlated with larval weight. Grass feeders survive longer than herb and woody plant feeders; the species surviving the longest feeds on lichens. Newly hatched larvae moved at a mean speed of 0.7-267.8 cm h^-1. Speed is not correlated with larval weight or survival time. Grass feeders move faster than woody plant feeders which, in turn, move faster than herb feeders. Woody plant feeders tend to move upwards, grass feeders downwards and herb feeders both upwards and downwards. The proportion of larvae silking is negatively correlated with larval weight.
The strong links between egg size and larval feeding ecology and between feeding ecology and larval behaviour are discussed. It is surprising that larval body size does not appear to constrain the speed of movement, nor tolerance to starvation.     

The host specificity of Lepeophtheirus pectoralis (Müller, 1776) (Copepoda: Caligidae)

The host specificity of Lepeophtheirus pectoralis (Müller) was examined experimentally by exposing different fish species to infection by artificially reared copepodid larvae. Copepodids which were hatched from eggs of adults parasitic on plaice ( platessae copepodids) preferred plaice to all other fishes tested, whereas copepodids which were hatched from eggs of adults parasitic on flounder ( flesi copepodids) preferred flounder to all other fish species. These behavioural differences suggest that two strains of L. pectoralis exist, one ( platessae ) adapted to plaice as its host and the other ( flesi ) to flounder. Comparison of an experimentally derived order of host preference with a table of occurrence obtained from the literature, suggests that a third strain of L. pectoralis , adapted to dab as its host, might also occur.
The process of infection by L. pectoralis copepodids is also described. It comprises a host location phase, during which the copepodid enters the habitat of its flatfish hosts and locates a host individual, and an attachment phase. The host location phase appears to be governed by changes in the activity of the copepodid and by its positively rheotactic response to water currents produced by the host. The attachment phase is probably based on the response of the copepodid to chemical factors produced by the host.     

Acoustic communication and the evolution of hearing in fishes

Fishes have evolved a diversity of sound-generating organs and acoustic signals of various temporal and spectral content. Additionally, representatives of many teleost families such as otophysines, anabantoids, mormyrids and holocentrids possess accessory structures that enhance hearing abilities by acoustically coupling air-filled cavities to the inner ear. Contrary to the accessory hearing structures such as Weberian ossicles in otophysines and suprabranchial chambers in anabantoids, sonic organs do not occur in all members of these taxa. Comparison of audiograms among nine representatives of seven otophysan families from four orders revealed major differences in auditory sensitivity, especially at higher frequencies (> 1 kHz) where thresholds differed by up to 50 dB. These differences showed no apparent correspondence to the ability to produce sounds (vocal versus non-vocal species) or to the spectral content of species-specific sounds. In anabantoids, the lowest auditory thresholds were found in the blue gourami Trichogaster trichopterus, a species not thought to be vocal. Dominant frequencies of sounds corresponded with optimal hearing bandwidth in two out of three vocalizing species. Based on these results, it is concluded that the selective pressures involved in the evolution of accessory hearing structures and in the design of vocal signals were other than those serving to optimize acoustic communication.     

A DESCRIPTION OF THE CORAL STRUCTURE OF TUTIA REEF (PANGANYIKA TERRITORY, EAST AFRICA), AND ITS FISH FUNA

The origin and structure of Tutia Reef, a coral reef off the Tanganyika coast, is described. It is concluded that the reef is formed in part from the cutting back flat of the older reef 14 ft above the level of the present reef, and in part from seaward growth of the reef.
Based on lines of quadrats down three sides of the reef an assessment of the cover of living coral on the reef is made, and the distribution of the dominant corals of the reef described. It is suggested that, contrary to the views of Crossland (1902, 1903), many East African coral reefs are undergoing seaward growth.
The distribution of the fishes on the reef is described, and a correlation is shown with the distribution of living coral on the reef. Many species of fishes have restricted distribution on the reef.
The feeding relationships of the fishes are discussed, and the total fish biomass divided into separate feeding categories. Tutia Reef has a low biomass of herbivorous fishes compared with the results from Eniwetok Atoll obtained by Odum & Odum (1955). This is considered to be due to the fact that Tutia Reef exhibits characteristics of an outer reef, deriving much of its energy from plankton, not those of an enclosed and almost autotrophic logoon.     

A Mathematical Technique for Estimating Blastodisc:Yolk Volume Ratios instead of Egg Sizes

Egg size alone is a poor and misleading variable in life-history studies. A mathematical technique for estimating yolk and blastodisc volume ratios in fishes, a much more meaningful character, is generated from first principles. The technique is demonstrated with an example of early ontogeny in fishes of the genus Lucania (Pisces: Cyprinodontidae). Wild, adult rainwater killifish, Lucania parva, and bluefin killifish, L. goodei, were collected in Florida and transported to the laboratory, where offspring were reared under controlled conditions. Offspring were sampled at the onset of cleavage, for simple measurements of yolk and blastodisc morphology. Application of mathematical equations allowed estimates of yolk and blastodisc volumes in the two species. No significant differences were found in clutch size, blastodisc volume, or egg density; however, significant differences existed in the absolute yolk investments, and blastodisc:yolk volume ratios. These differences in reproductive investment within the genus Lucania are interpreted by the altricial-precocial life-history model as a possible causal mechanism in the evolution of species within this genus. The mathematical equations presented in this study enabled us to partition reproductive investment into components that are more biologically meaningful than simple egg size.     

Reproductive behaviour and early development of the Drysdale hardyhead, Craterocephalus sp. nov. (Pisces: Atherinidae), from the Alligator Rivers System, Northern Territory, Australia

Craterocephalus sp. nov. showed sexual dimorphism in body shape during the breeding season. Pairing occurred during daylight with a single release of eggs amongst submerged vegetation between sunrise and the early afternoon on the same day. The eggs were demersal, adhesive, spherical (0.87–0.96 mm diameter) and had 12 adhesive filaments (0.5–1.5 mm long) at the animal pole. Approximately 24 oil droplets (0.02–0.08 mm diameter) persisted throughout egg and larval development. Hatching occurred 155–160 h after spawning at 25–27° C.
The yolk-sac larvae were 3.85–3.95 mm notochord length at hatching and began feeding at the surface after absorption of the yolk (3–12 h after hatching). All fin rays were developed in 9.4 mm standard length fry, which moved from midwater to feed on the substrate. Aquarium reared fish first spawned at 30 mm s.L. when 165 days of age.
Features of Craterocephalus reproduction, as they relate to a specific survival strategy, are briefly discussed.     

The diet and infection of fishes in Cavendish Dock, Barrow-in-Furness

Some 934 fishes belonging to ten species were examined in Cavendish Dock, Walney Channel and in the River Duddon in order to study their diet and infection.
Because of the limited number of food species occurring in Cavendish Dock, the diet of fishes examined is similar and composed of twelve different species.
The diet of the flounders in Walney Channel differs markedly from those in the dock.
The infection with parasitic worms of fishes in Cavendish Dock is lower than in other localities.
Fifteen different species of parasitic worms belonging to Trematoda, Cestoda, Nematoda and Acanthocephala were recorded in fishes examined.
Salinity of the dock water influences the composition of the diet and infection of fishes in Cavendish Dock. Raised temperature and salinity are artificially introduced by human activities, and beiig controllable, could serve for experimental ecological investigations in     

Ephemeroptera eggs and their contribution to phylogenetie studies of the order1

Eggs of representative genera of all families of Ephemeroptera except the Palingeniidae were studied. Their external morphology is reviewed, and hypotheses have been proposed to explain the evolution of several chorionic features and types of attachment structure.
The archetypical Ephemeroptera egg is considered to have been round, with a smooth chorion, non-fibrous adhesive layer, funnelform micropyle, and a suprachorionic sperm guide. Subsequent evolution resulted in several different micropyles and many different chorionic sculpturings and attachment structures.
Data obtained from studying the egg stage are utilized as aids to understanding the phytogeny of the Ephemeroptera. The proposed classification divides the order into 21 families arranged into 6 superfamilies.     

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.