Parallel life history evolution in mouthbrooding cichlids from the African Great Lakes

The existence of ancient deep-water lakes provides an opportunity to study the independent adaptation of aquatic organisms to pelagic, benthic, and rocky shore habitats. With improving resolution of their phylogenetic relationships, the many cichlid fish species endemic to the African Great Lakes Malawi, Tanganyika, and Victoria provide a significant resource for the comparative study of such evolutionary processes. Here, we show that cichlid lineages colonizing rocky shores and pelagic habitats in the different lakes have independently evolved larger eggs and lower fecundities than benthic lineages, suggesting parallel adaptive life-history evolution. By contrast, other pelagic teleost fishes in both marine and freshwater habitats, including African lakes, typically produce large numbers of very small eggs. Our results also suggest that decreased fecundity and increased egg size not only occurred independently in each lake but occurred independently in the colonization of rocky and pelagic habitats.     

Gambusia affinis: dispersal due to floods and its failure to colonize new water bodies in Shahjahanpur District (U.P.).

In villages of District Shahjahanpur, 122 decentralized Gambusia multiplication ponds were established to cover the need of the entire district. Profuse breeding of Gambusia was observed in these ponds. The fishes are being successfully used in mosquito control all over the district. In July 1990 there was a widespread flood due to which 70 Gambusia multiplication ponds were affected and the fish was washed away in large numbers, leaving only a scanty population in the flood-affected ponds. We utilized this opportunity to study the natural dispersal and colonization of Gambusia in different aquatic habitats. The study revealed that Gambusia was either not found in most habitats or was present in very small numbers, and on its own Gambusia was unable to eliminate the local fauna to become a dominant species. Predatory fishes and birds played a major role in eliminating Gambusia. Gambusia is therefore unlikely to pose any ecological hazard in vector-control programmes.     

Small-scale field experiments accurately scale up to predict density dependence in reef fish populations at large scales

Field experiments provide rigorous tests of ecological hypotheses but are usually limited to small spatial scales. It is thus unclear whether these findings extrapolate to larger scales relevant to conservation and management. We show that the results of experiments detecting density-dependent mortality of reef fish on small habitat patches scale up to have similar effects on much larger entire reefs that are the size of small marine reserves and approach the scale at which some reef fisheries operate. We suggest that accurate scaling is due to the type of species interaction causing local density dependence and the fact that localized events can be aggregated to describe larger-scale interactions with minimal distortion. Careful extrapolation from small-scale experiments identifying species interactions and their effects should improve our ability to predict the outcomes of alternative management strategies for coral reef fishes and their habitats.     

The interruption of thyroid and interrenal and the inter-hormonal interference in fish: does it promote physiologic adaptation or maladaptation?

Endocrines, the chief components of chemical centers which produce hormones in tune with intrinsic and extrinsic clues, create a chemical bridge between the organism and the environment. In fishes also hormones integrate and modulate many physiologic functions and its synthesis, release, biological actions and metabolic clearance are well regulated. Consequently, thyroid hormones (THs) and cortisol, the products of thyroid and interrenal axes, have been identified for their common integrative actions on metabolic and osmotic functions in fish. On the other hand, many anthropogenic chemical substances, popularly known as endocrine disrupting chemicals, have been shown to disrupt the hormone–receptor signaling pathways in a number fish species. These chemicals which are known for their ability to induce endocrine disruption particularly on thyroid and interrenals can cause malfunction or maladaptation of many vital processes which are involved in the development, growth and reproduction in fish. On the contrary, evidence is presented that the endocrine interrupting agents (EIAs) can cause interruption of thyroid and interrenals, resulting in physiologic compensatory mechanisms which can be adaptive, though such hormonal interactions are less recognized in fishes. The EIAs of physical, chemical and biological origins can specifically interrupt and modify the hormonal interactions between THs and cortisol, resulting in specific patterns of inter-hormonal interference. The physiologic analysis of these inter-hormonal interruptions during acclimation and post-acclimation to intrinsic or extrinsic EIAs reveals that combinations of anti-hormonal, pro-hormonal or stati-hormonal interference may help the fish to fine-tune their metabolic and osmotic performances as part of physiologic adaptation. This novel hypothesis on the phenomenon of inter-hormonal interference and its consequent physiologic interference during thyroid and interrenal interruption thus forms the basis of physiologic acclimation. This interfering action of TH and cortisol during hormonal interruption may subsequently promote ecological adaptation in fish as these physiologic processes ultimately favor them to survive in their hostile environment.     

Lungfish evolution and development

The first vertebrates recognizable as tetrapods appeared in the mid-Devonian. It is generally agreed that their ancestors were lobe-finned fish. What is not agreed is how close either of the extant groups of lobe-finned fish, lungfish or coelacanths, is to the actual ancestor of the tetrapods. The soft anatomy of living lungfish shares many similarities with that of living amphibians. Many of these similarities are not present in either coelacanths or any members of the other extant bony fish group, the ray-finned fishes. Many very well preserved lungfish from the Devonian possess specialized features that would appear to exclude them from being ancestral to tetrapods. I am hypothesizing that lungfish in the Devonian may have included metamorphosis in their life cycle and that neoteny in some species may have been an early corollary. These reproductively mature neotenous lungfish would not have had the specialised features of metamorphosed adults. Fossils of these neotenous forms may have more closely resembled the tetrapod ancestral lobe-finned fish, currently believed to be a panderichthiad fish. Living lungfish have a number of larval features, which suggest paedomorphosis. Also of significance is the very large genome of living lungfish, which, in urodele amphibians, is a feature correlated with neoteny. Our current knowledge of the thyroid axis in the lungfish, Neoceratodus forsteri, is consistent with neoteny in amphibians, but the only Devonian fossil considered to be a larval lungfish bears no resemblance to living lungfish or to panderichthiads. The enigmatic phylogenetic relationship of lungfish with the first tetrapods remains, but the hunt for other forms of larval Devonian lungfish is on!     

Helminths of Antarctic fishes

Antarctic fishes are represented by sharks, skates (Chondrichthyes) and bony fishes (Teleostei). Teleosts play an important role in the completion of life cycles of many helminth species. They serve as either definitive or intermediate and paratenic hosts. Chondrichthyes are definitive hosts only. Seventy three helminth species occur as the adult stage in fishes: Digenea (45), Cestoda (14), Nematoda (6), Acanthocephala (8), Also, 11 larval stages of Cestoda (7) and Nematoda (4) are known, together with 7 species of Acanthocephala in the cystacanth stage. One digenean species, Otodistomum cestoides, matures in skates. Among cestodes maturing in fishes only one, Parabothriocephalus johnstoni, occurs in a bony fish, Macrourus whitsoni. Antarctic Chondrichthyes are not infected with nematodes and acanthocephalans. Cestode larvae from teleosts belong to Tetraphyllidea (parasites of skates), and Tetrabothriidae and Diphyllobothriidae (parasites of birds and mammals). Larval nematodes represent Anisakidae, parasites of fishes, birds and mammals. Acanthocephalan cystacanths mature in pinnipeds and birds. The majority of parasites maturing in Antarctic fishes are endemics. Only 4 digenean and one nematode species, Hysterothylacium aduncum, are cosmopolitan. All acanthocephalans, almost all digeneans, the majority of cestodes and some nematodes occur mainly or exclusively in benthic fishes. Specificity of the majority of helminths utilizing teleosts as intermediate and/or paratenic hosts is low. Among parasites using fishes as definitive hosts, all Cestoda, most Digenea and Nematoda, and almost all Acanthocephala have a range of hosts restricted to one order or even to 1-2 host species.     

Fish Species Distribution in Seagrass Habitats of Chesapeake Bay are Structured by Abiotic and Biotic Factors

Abstract

Seagrass habitats have long been known to serve as nursery habitats for juvenile fish by providing refuges from predation and areas of high forage abundance. However, comparatively less is known about other factors structuring fish communities that make extensive use of seagrass as nursery habitat. We examined both physical and biological factors that may structure the juvenile seagrass-associated fish communities across a synoptic-scale multiyear study in lower Chesapeake Bay. Across 3 years of sampling, we collected 21,153 fish from 31 species. Silver Perch Bairdiella chrysoura made up over 86% of all individuals collected. Nine additional species made up at least 1% of the fish community in the bay but were at very different abundances than historical estimates of the fish community from the early 1980s. Eight species, including Silver Perch, showed a relationship with measured gradients of temperature or salinity and Spot Leiostomus xanthurus showed a negative relationship with the presence of macroalgae. Climate change, particularly increased precipitation and runoff from frequent and intense events, has the potential to alter fish–habitat relationships in seagrass beds and other habitats and may have already altered the fish community composition. Comparisons of fish species to historical data from the 1970s, our data, and recent contemporary data in the late 2000s suggests this has occurred.

Received September 4, 2012; accepted May 5, 2013     

Parasitic Crustacea of fishes from the north-east Atlantic Ocean

Fish from the north-east Atlantic, including neighbouring aquens are host of 3 species of Branchiura, 163 Copepoda, 37 Isopoda, 2 Amphipoda, and 1 of parasitic Cirripedia. Chondrichthyes have more species of parasitic crustaceans than Osteichthyes. Many specific parasites of Osteichthyes and the facultative parasites of fish include species of crustaceans to fish of both classes. 165 species of parasitic crustaceans are found in benthic and near-benthic fish, and 55 in pelagic fish. The greatest variety of species parasitic crustaceans is found in fishes in the North Sea (139); it is much smaller in the Baltic Sea (15). Endemic species constitute 15% of the total number of parasitic crustacean. The irregular distribution of parasitic crustaceans is among others connected with the biology and ecology of both hosts and their parasites.     

γ射线控制华支睾吸虫囊蚴感染性的效果

用0－0．20kGy钴－60γ射线对含华支睾吸虫囊蚴的鱼体和从鱼体中分离所得的囊蚴（离体囊蚴）分别进行照射，观察照射囊蚴在宿主（动物）体内发育的能力。囊蚴以灌胃法感染豚鼠或大鼠。用粪检虫卵和尸剖动物检查虫体的生物学方法，判定控制华支睾吸虫囊蚴感染性的最小有效剂量。结果表明，照射离体囊蚴的最小有效剂量为0．05kGy。照射鱼体组织内囊蚴的半数致死量为0．05kGy，最小有效剂量为0．15kGy。我国北方、中部和南方的该虫株囊蚴对钴－60γ射线的敏感性无显著差异，认为用钴－60γ射线0．15kGy剂量可完全控制鱼体中华支睾吸虫囊蚴的感染性，因而辐照技术可作为预防医学中的一种方法。     

Studies on the use of cobalt-60 gamma irradiation to control infectivity of Clonorchis sinensis metacercariae.

The purpose of the present study was to observe the survival and development of Clonorchis sinensis metacercariae in their final hosts after Cobalt-60 gamma irradiation of isolated metacercariae or the parasite in fish. Guinea pigs or albino rats were orally infected with irradiated metacercariae by gavage. Bioassay, fecal examination for ova, and necropsy of infected animals, were the methods used for the estimation of minimum effective dose of gamma irradiation to control infectivity of the metacercariae. Results showed that the minimum effective irradiation dose for isolated metacercariae was 0.05 kGy. The LD50 of the irradiation dose for metacercariae in fish was 0.05 kGy, and the minimum effective dose was 0.15 kGy. No significant difference in radiation susceptibility to Co-60 gamma irradiation was found among C. sinensis metacercariae in fishes collected at different localities in northern, middle or southern parts of China. The present finding suggests that irradiation of fish by 0.15 kGy could control infectivity of C. Sinensis metacercariae and thus be adopted as a control measure in preventing infections.     

Assessing Freshwater Habitat of Adult Anadromous Alewives Using Multiple Approaches

Abstract

After centuries of disturbance, environmental professionals now recognize the need to restore coastal watersheds for native fish and protect the larger ecosystems on which fish and other aquatic biota depend. Anadromous fish species are an important component of coastal ecosystems that are often adversely affected by human activities. Restoring native anadromous fish species is a common focus of both fish and coastal watershed restoration. Yet restoration efforts have met with uneven success, often due to lack of knowledge about habitat availability and use. Using habitat surveys and radio tracking of adult anadromous alewives Alosa pseudoharengus during their spring spawning migration, we illustrate a method for quantifying habitat using multiple approaches and for relating mobile fish distribution to habitat. In the Ipswich River, Massachusetts, measuring habitat units and physical conditions at transects (width, depth, and velocity) provided an ecological basis for the interpretation of landscape patterns of fish distribution. Mapping habitat units allowed us to efficiently census habitat relevant to alewives for the entire 20.6 river kilometers of interest. Our transect data reinforced the results of the habitat unit survey and provided useful, high-resolution ecological data for restoration efforts. Tagged alewives spent little time in riffle–run habitats and substantial time in pools, although the locations of pool occupancy varied. The insights we provide here can be used to (1) identify preferred habitats into which anadromous fish can be reintroduced in order to maximize fish survival and reproduction and (2) pinpoint habitat types in urgent need of protection or restoration.

Received April 3, 2011; accepted January 9, 2012     

Survey of Anisakis larvae in marine fish of Taiwan

A survey on the prevalence and intensity of larval anisakid infection in some species of marine fishes sold in the markets at Tan-shui in northern Taiwan was carried out from May to August 1980. The general infection rate was 37.7% with an average of 14.2 larvae per fish. A total of 13 species of examined fishes were found with Anisakis larvae, these were Argyrosomus argentatus, Caranx djeddaba, Diploprion bifasciatum, Evynnis cardinalis, Lethrinus haematopterus, Megalops cyprinoides, Nemipterus virgatus, Paraplagusia formosana, Plectorhinchus pictus, Rastrelliger chrysozonus, Saurida tumbil, Scolopsis vosmeri, and Trichiurus haumela. The highest intensity of Anisakis larvae was obtained in E. cardinalis with an average of 80.3 larvae per fish; the next was in N. virgatus (76.2 larvae/fish). The parasite could not be found in the other 20 species of fishes examined.     

Seamounts are hotspots of pelagic biodiversity in the open ocean

The identification of biodiversity hotspots and their management for conservation have been hypothesized as effective ways to protect many species. There has been a significant effort to identify and map these areas at a global scale, but the coarse resolution of most datasets masks the small-scale patterns associated with coastal habitats or seamounts. Here we used tuna longline observer data to investigate the role of seamounts in aggregating large pelagic biodiversity and to identify which pelagic species are associated with seamounts. Our analysis indicates that seamounts are hotspots of pelagic biodiversity. Higher species richness was detected in association with seamounts than with coastal or oceanic areas. Seamounts were found to have higher species diversity within 30–40 km of the summit, whereas for sets close to coastal habitat the diversity was lower and fairly constant with distance. Higher probability of capture and higher number of fish caught were detected for some shark, billfish, tuna, and other by-catch species. The study supports hypotheses that seamounts may be areas of special interest for management for marine pelagic predators.     

Distribution of freshwater snails in family-based VAC ponds and associated waterbodies with special reference to intermediate hosts of fish-borne zoonotic trematodes in Nam Dinh Province, Vietnam

Fish-borne zoonotic trematodes, such as Clonorchis sinensis, heterophyids and others, constitute a public health concern in parts of northern Vietnam and infections with these trematodes are often thought to be linked to fish culture. One common fish culture system is the integrated fish-livestock (VAC) ponds where individual households have 1 or more ponds. Fish fry, mainly of various carp species, produced in hatcheries, not necessarily local, are introduced into nursery ponds and after approximately 6 weeks, juvenile fishes are transferred to household ponds, referred to as grow-out ponds. Grow-out ponds are usually fertilized with organic debris, including animal excreta, to stimulate algal growth and subsequently fish growth. This paper describes the distribution of freshwater snails and occurrence of trematode infections in these in VAC ponds and associated habitats as part of a major study on risk factors of FZT infections in cultured fish in two communes, Nghia Lac and Nghia Phu, Nghia Hung District, Nam Dinh Province. The area is under intense rice cultivation with an extensive canal network supplying fields and also household VAC ponds. A total of 16 snail species was found and four were widely distributed i.e. Angulyagra polyzonata, Melanoides tuberculata, Bithynia fuchsiana and Pomacea insularum. Snail diversity and counts were higher in nursery ponds than in grow-out ponds. Species of the families Thiaridae and Viviparidae were more abundant than other species in VAC ponds while species of the Bithyniidae, Stenothyridae and Planorbidae dominated in rice fields and small canals. Trematode infections were found in eight snail species and among these M. tuberculata had the highest overall prevalence of infection (13.28%). No trematode infections were found in species of the Viviparidae and Ampullaridae except for metacercariae. Parapleurolophocercous and pleurolophocercous cercariae constituted the most common type of cercariae recovered, contributing 40.6% of all infections followed by echinostome cercariae (35.0%) and xiphidiocercariae (17.3%). Bithynia fuschiana and M. tuberculata had the most diverse trematode fauna. C. sinensis was not recorded in this study. The VAC pond system in this area, is very important for transmission of minute intestinal trematodes while they play little role in transmission of C. sinensis as its intermediate hosts, bithynid snails, rarely occur in these ponds. From a public health perspective this is positive as the effects of infections with intestinal trematodes are considered mild. On the other hand it is possible that even such subtle effects could have importance in public health as transmission is very intense in the area. And this in combination with the aquaculture importance, reduced marketability of fishes with high metacercariae loads, warrants that control efforts against these trematodes are initiated to reduce transmission in this production system.     

Evolutionary changes of multiple visual pigment genes in the complete genome of Pacific bluefin tuna

Tunas are migratory fishes in offshore habitats and top predators with unique features. Despite their ecological importance and high market values, the open-ocean lifestyle of tuna, in which effective sensing systems such as color vision are required for capture of prey, has been poorly understood. To elucidate the genetic and evolutionary basis of optic adaptation of tuna, we determined the genome sequence of the Pacific bluefin tuna (Thunnus orientalis), using next-generation sequencing technology. A total of 26,433 protein-coding genes were predicted from 16,802 assembled scaffolds. From these, we identified five common fish visual pigment genes: red-sensitive (middle/long-wavelength sensitive; M/LWS), UV-sensitive (short-wavelength sensitive 1; SWS1), blue-sensitive (SWS2), rhodopsin (RH1), and green-sensitive (RH2) opsin genes. Sequence comparison revealed that tuna''s RH1 gene has an amino acid substitution that causes a short-wave shift in the absorption spectrum (i.e., blue shift). Pacific bluefin tuna has at least five RH2 paralogs, the most among studied fishes; four of the proteins encoded may be tuned to blue light at the amino acid level. Moreover, phylogenetic analysis suggested that gene conversions have occurred in each of the SWS2 and RH2 loci in a short period. Thus, Pacific bluefin tuna has undergone evolutionary changes in three genes (RH1, RH2, and SWS2), which may have contributed to detecting blue-green contrast and measuring the distance to prey in the blue-pelagic ocean. These findings provide basic information on behavioral traits of predatory fish and, thereby, could help to improve the technology to culture such fish in captivity for resource management.     

广西淡水鱼携带异形科吸虫囊蚴的调查研究

目的了解广西淡水鱼异形科吸虫感染情况。方法使用消化法对从桂北的阳朔县及桂南的南宁市、马山县、扶绥县和宾阳县等地采集的淡水鱼进行检查。结果共检查各种鱼类316尾,分属鲤科33种、Centropomidae科和丽鱼科各1种。鲤科鱼33种中有28种、Centropomidae科的Coreoperca whiteheadi 1种带有异形吸虫囊蚴。共检出后殖吸虫、扇棘单睾吸虫、钩棘单睾吸虫和台湾棘带吸虫等4种异形吸虫囊蚴,其感染率分别为28.2%、27.5%、44.3%和10.8%。桂北检查112尾,后殖吸虫感染率为78.6%;桂南检查204尾,钩棘单睾吸虫感染率最高,为63.2%,其次为扇棘单睾吸虫42.7%和台湾棘带吸虫16.7%,后殖吸虫为0.5%。结论广西各地淡水鱼异形吸虫感染非常普遍和严重,尤以桂南为甚。异形吸虫与华支睾吸虫感染方式相同、流行区域重叠及虫卵形态相似,临床上要注意其鉴别诊断。     

Parasites of sticklebacks (Actinopterygii: Gasterosteidae) from South-Eastern Baltic Sea (Poland)

A total of 142 individuals of Gasterosteus aculeatus L. and 22 individuals of Pungitius pungitius (L.) from several areas of the coastal waters of the Gdańsk Bay both brackish- and freshwater were examined for parasites. The survey was carried out within 1988-1991. Six parasite species, namely: Gyrodactylus arcuatus, Apatemon gracilis, Sphaerostomum bramae, Phyllodistomumfolium, Neoechinorhynchus rutili, and Argulus foliaceus were recovered from sticklebacks caught in freshwater habitats; while the other 4 parasites: Apatemon annuligerum, Bothriocephalus sp., Schistocephalus solidus, Proteocephalus percae occurred only in fish from brackish-water areas. Additional 5 parasites: Trichodina domerguei, Diplostomum pungitii, Diplostomum spathaceum, Rhaphidascaris acus, and Thersitina gasterostei were recorded in fishes from both habitats.     

L-Kynurenine, an amino acid identified as a sex pheromone in the urine of ovulated female masu salmon

Many animals employ sex pheromones to find mating partners during their reproductive seasons. However, most sex pheromones of vertebrates remain to be identified. Over the past 20 years, steroids and prostaglandins have been identified as sex pheromones in several fishes. These pheromones are broadly termed "hormonal pheromones" because they or their precursors act as hormones in these fishes. Hitherto, no other type of sex pheromone has been unambiguously identified in teleost fish. Here we report the identification of a "nonhormonal pheromone" in teleost fish. The urine of the reproductively mature female masu salmon (Oncorhynchus masou) contains a male-attracting pheromone. Bioassay-guided fractionation yielded an active compound that was identical to L-kynurenine in spectral and chromatographic properties. L-Kynurenine is a major metabolite of L-tryptophan in vertebrates. This pheromone elicits a male-specific behavior at even picomolar concentrations; its electrophysiological threshold is 10(-14) M. L-Kynurenine is a reasonable substance for female masu salmon to advertise their readiness for mating.