Species Of Marine Teleost Fishes Research Articles

Further diversity in the origins of fish antifreeze proteins.

Shifts in environmental conditions can impose strong selection for adaptive traits. During the Cenozoic era, as the oceans cooled, many marine teleost fish species were at risk of freezing. This led to the independent emergence of distinct ice-binding antifreeze proteins (AFPs). The report in this issue by Graham and Davies reveals the development of AFP genes in shorthorn and longhorn sculpin from a copy of the lunapark gene. The predicted sculpin AFP sequences are unrelated to that of lunapark; the coding sequences for the AFPs appear to have arisen from small portions of the lunapark gene by codon frameshifting along with a series of mutations.

Inferring the extinction risk of marine fish to inform global conservation priorities.

While extinction risk categorization is fundamental for building robust conservation planning for marine fishes, empirical data on occurrence and vulnerability to disturbances are still lacking for most marine teleost fish species, preventing the assessment of their International Union for the Conservation of Nature (IUCN) status. In this article, we predicted the IUCN status of marine fishes based on two machine learning algorithms, trained with available species occurrences, biological traits, taxonomy, and human uses. We found that extinction risk for marine fish species is higher than initially estimated by the IUCN, increasing from 2.5% to 12.7%. Species predicted as Threatened were mainly characterized by a small geographic range, a relatively large body size, and a low growth rate. Hotspots of predicted Threatened species peaked mainly in the South China Sea, the Philippine Sea, the Celebes Sea, the west coast Australia and North America. We also explored the consequences of including these predicted species' IUCN status in the prioritization of marine protected areas through conservation planning. We found a marked increase in prioritization ranks for subpolar and polar regions despite their low species richness. We suggest to integrate multifactorial ensemble learning to assess species extinction risk and offer a more complete view of endangered taxonomic groups to ultimately reach global conservation targets like the extending coverage of protected areas where species are the most vulnerable.

Alternating regimes of shallow and deep-sea diversification explain a species-richness paradox in marine fishes

The deep sea contains a surprising diversity of life, including iconic fish groups such as anglerfishes and lanternfishes. Still, >65% of marine teleost fish species are restricted to the photic zone <200 m, which comprises less than 10% of the ocean's total volume. From a macroevolutionary perspective, this paradox may be explained by three hypotheses: 1) shallow water lineages have had more time to diversify than deep-sea lineages, 2) shallow water lineages have faster rates of speciation than deep-sea lineages, or 3) shallow-to-deep sea transition rates limit deep-sea richness. Here we use phylogenetic comparative methods to test among these three non-mutually exclusive hypotheses. While we found support for all hypotheses, the disparity in species richness is better described as the uneven outcome of alternating phases that favored shallow or deep diversification over the past 200 million y. Shallow marine teleosts became incredibly diverse 100 million y ago during a period of warm temperatures and high sea level, suggesting the importance of reefs and epicontinental settings. Conversely, deep-sea colonization and speciation was favored during brief episodes when cooling temperatures increased the efficiency of the ocean's carbon pump. Finally, time-variable ecological filters limited shallow-to-deep colonization for much of teleost history, which helped maintain higher shallow richness. A pelagic lifestyle and large jaws were associated with early deep-sea colonists, while a demersal lifestyle and a tapered body plan were typical of later colonists. Therefore, we also suggest that some hallmark characteristics of deep-sea fishes evolved prior to colonizing the deep sea.

Tissue distribution of triphenyltin compounds in marine teleost fishes

Continuous release of the highly toxic triphenyltin compounds (TPT) from antifouling paints and fungicides has caused serious pollution to urbanized coastal marine environments worldwide since the 1960s. Using gas-chromatography mass-spectrometry (GC–MS), this study investigated the distribution profile of TPT in 15 types of tissues of four marine teleost fish species collected from Hong Kong waters. Concentrations of TPT in various tissues had a significant positive correlation with protein contents in the tissues (r = 0.346, p < 0.001) and, to a lesser extent with lipid contents (r = 0.169, p = 0.020). Highest concentrations of TPT were consistently found in liver, ranging from 1074.9 to 3443.7 ng/g wet weight; whereas fish scales always contained the least concentration of TPT in all species, ranging from 10.4 to 48.5 ng/g wet weight. Through mass balance models and regression analyses, muscle tissues were found to contribute most to the total TPT body burden, and the average TPT concentration of both dorsal and ventral muscles was identified as the best predictor for estimating TPT burden in the entire fish. Hence, further investigations of bioaccumulation and biomagnification of TPT in fishes should adopt this modelling approach in estimating its total body burden in individual fish.

Length-weight relationships of four marine fish species caught in the South China Sea

Length–weight relationships are described for four marine teleost fish species caught in the South China Sea. A total of 625 individuals were collected from April to August 2007 and November 2012 using a bottom trawl (mesh size, 3.9 cm) and longline fishing. The values of parameters a and b ranged from 0.004612 to 0.02137 and 3.019 to 3.371, respectively. The high r2 values (all >.950) indicate that these relationships are robust and will be appropriate for use in fisheries management of these species.

Genetic identification of anisakid nematodes isolated from largehead hairtail (Trichiurus japonicus) in Korea

The nematode species belonging to genus Anisakis occur at their third larval stage in numerous marine teleost fish species worldwide and known to cause accidental human infection through the ingestion of raw or undercooked fish or squids. They may also draw the attention of consumers because of the visual impact of both alive and dead worms. Therefore, the information on their geographical distribution and clear species identification is important for epidemiological survey and further prevention of human infection. For identification of anisakid nematodes species isolated from largehead hairtail (Trichiurus japonicus), polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) analysis of internal transcribed spacers of ribosomal DNA were conducted. Mitochondrial cytochrome c oxidase subunit 2 gene was also sequenced, and phylogenetic analysis was conducted. From the largehead hairtail (n = 9), 1259 nematodes were isolated in total. Most of the nematodes were found encapsulated throughout the viscera (56.2 %, 708/1259) or moving freely in the body cavity (41.5 %, 523/1259), and only 0.3 % (4/1259) was found in the muscles. By PCR-RFLP, three different nematode species were identified. Anisakis pegreffii was the most dominantly found (98.7 %, 1243/1259) from the largehead hairtail, occupying 98.7 % (699/708) of the nematodes in the mesenteries and 98.1 % (513/523) in the body cavity. Hybrid genotype (Anisakis simplex × A. pegreffii) occupied 0.5 %, and Hysterothylacium sp. occupied 0.2 % of the nematodes isolated in this study. The largehead hairtail may not significantly contribute accidental human infection of anisakid nematode third stage larvae because most of the nematodes were found from the viscera or body cavity, which are not consumed raw. But, a high prevalence of anisakid nematode larvae in the largehead hairtail is still in concern because they may raise food safety problems to consumers. Immediate evisceration or freezing of fish after catch will be necessary before consumption.

Transcriptome analysis of dormant tomonts of the marine fish ectoparasitic ciliate Cryptocaryon irritansunder lowtemperature.

BackgroundCryptocaryon irritans, a species of obligatory ciliate ectoparasite, can infect various species of marine teleost fish. Cryptocaryon irritans that fall to the seabed or aquarium bottom in winter can form “dormant tomonts” and wake up when the temperature rises the next year. Abundant studies and analyses on the dormant tomonts were carried out at the transcriptome level, in order to investigate the molecular mechanism of C. irritans tomonts entering the dormant state under low-temperature conditions.MethodsThe paired-end sequencing strategy was used to better assemble the entire transcriptome de novo. All clean sequencing reads from each of the three libraries (Group A: untreated blank control; Group B: treated for 24 h at 12 °C; and Group C: developed for 24 h at 25 °C) were respectively mapped back to the transcriptome assembly using the bioinformatics software.ResultsIn this study, 25,695,034, 21,944,467, and 28,722,875 paired-end clean reads were obtained respectively from the three cDNA libraries of the C. irritans tomont by Illumina paired-end sequencing technology. A total of 25,925 unique transcript fragments (unigenes) were assembled, with an average length of 839 bp. Differentially expressed genes (DEGs) were scrutinized; in Group B/A pairwise comparison, 343 genes presented differential expression, including 265 up-regulated genes and 78 down-regulated genes in Group B; in Group C/A pairwise comparison, there were 567 DEGs, including 548 up-regulated genes and 19 down-regulated genes in Group C; and in Group B/C pairwise comparison, 185 genes showed differential expression, including 145 up-regulated genes and 40 down-regulated genes in Group B.ConclusionsThis is the first transcriptomic analytical study of the C. irritans tomonts under low temperature. It can be concluded that most of the genes required for its cell survival under low temperature, or for cell entry into a deeper dormancy state were discovered, and that they might be considered as candidate genes to develop the diagnostic and control measures for cryptocaryoniasis.Electronic supplementary materialThe online version of this article (doi:10.1186/s13071-016-1550-1) contains supplementary material, which is available to authorized users.

The Rab5A gene of marine fish, large yellow croaker (Larimichthys crocea), and its response to the infection of Cryptocaryon irritans.

Rab GTPases, members of the Ras superfamily, encode monomeric G-proteins. Rab proteins regulate key steps in membrane traffic transport and endocytic pathway of host immune responses. Rab5A is involved in immune regulation, particularly in T cell migration and macrophage endocytosis in higher vertebrates. However, little is known of the molecular structure of Rab5A gene in marine teleost fish species and its expression profile during the parasite infection. In this study, the full-length cDNA sequence and genomic structure of Rab5A gene of the large yellow croaker (Larimichthys crocea) (LycRab5A), one of the most economical marine fishes, were identified and characterized. The LycRab5A protein, containing the ATPase/GTPase binding motifs and the effector molecules binding motifs, was highly homologous to that of other animals. The expression plasmid containing LycRab5A cDNA fused with GST was engineered and transformed into Escherichia coli to produce recombinant protein GST-LycRab5A, which was purified to prepare a polyclonal antibody specifically against LycRab5A. Subcellular localization revealed that LycRab5A expressed in the membrane and cytoplasm. Based on real-time PCR and Western blot analysis, we found that both mRNA and protein of LycRab5A were expressed in all tissues we examined; especially it was highly expressed in blood and gill. Interestingly, both mRNA and protein of LycRab5A were substantially up-regulated when parasitic ciliate protozoan (Cryptocaryon irritans) was infected. The expression of LycRab5A was reached to the maximal level at 24h after infection. The line of evidence suggested that LycRab5A might play an important role in large yellow croaker defense against parasite infection. Moreover, on the basis of protein interaction, it was found that the LycRab5A interacted with myosin light chain (designated as LycMLC), a crucial protein in the process of phagocytosis. This discovery might contribute better understanding to the molecular events involved in fish immune responses.

Delta-8 desaturation activity varies among fatty acyl desaturases of teleost fish: High activity in delta-6 desaturases of marine species

The benefits of dietary fish and fish oil are derived from n-3 long-chain polyunsaturated fatty acids (LC-PUFA) that have beneficial effects in a range of human diseases and pathologies such as cardiovascular and other inflammatory disorders, neural development and neurological pathologies. The precursor of n-3 LC-PUFA, 18:3n-3 does not have the same beneficial effects prompting interest in the pathways of endogenous synthesis of LC-PUFA in vertebrates. The LC-PUFA biosynthesis pathway classically involves Δ6 and Δ5 fatty acyl desaturases (Fad), but it was recently shown that Δ6 Fad in mammals also displayed Δ8 activity demonstrating a possible alternative "Δ8-pathway" for the synthesis of LC-PUFA. Our primary hypothesis was that Δ8 desaturase activity would be a common feature of vertebrate Δ6 Fads, and so the aim of the present study was to determine the ability of teleostei Fads for Δ8 desaturation activity. To this end, cDNAs for Fads from a range of freshwater, diadromous and marine teleost fish species were assayed for Δ8 activity in the heterologous yeast expression system. In summary, the present study has demonstrated that Δ8 desaturation activity was also a characteristic of fish orthologs, although the activity varied notably between freshwater/diadromous and marine fish species, with the latter possessing Fads2-like proteins with Δ8 activity far higher than mammalian FADS2. The data showed that, generally, the fish Fad are technically υ-3 desaturases, with new double bonds introduced 3C beyond a pre-existing double bond. However, the ability of zebrafish and rabbitfish Fads, previously characterised as Δ6/Δ5 bifunctional desaturases, to introduce non-methylene interrupted double bonds in 20:3n-3 and 20:2n-6 suggested that a novel combination of regioselectivity modes operates within these enzymes.

Seasonal Plasticity of Auditory Saccular Sensitivity in the Vocal Plainfin Midshipman Fish,Porichthys notatus

The plainfin midshipman fish, Porichthys notatus, is a seasonally breeding species of marine teleost fish that generates acoustic signals for intraspecific social and reproductive-related communication. Female midshipman use the inner ear saccule as the main acoustic endorgan for hearing to detect and locate vocalizing males that produce multiharmonic advertisement calls during the breeding season. Previous work showed that the frequency sensitivity of midshipman auditory saccular afferents changed seasonally with female reproductive state such that summer reproductive females became better suited than winter nonreproductive females to encode the dominant higher harmonics of the male advertisement calls. The focus of this study was to test the hypothesis that seasonal reproductive-dependent changes in saccular afferent tuning is paralleled by similar changes in saccular sensitivity at the level of the hair-cell receptor. Here, I examined the evoked response properties of midshipman saccular hair cells from winter nonreproductive and summer reproductive females to determine if reproductive state affects the frequency response and threshold of the saccule to behaviorally relevant single tone stimuli. Saccular potentials were recorded from populations of hair cells in vivo while sound was presented by an underwater speaker. Results indicate that saccular hair cells from reproductive females had thresholds that were approximately 8 to 13 dB lower than nonreproductive females across a broad range of frequencies that included the dominant higher harmonic components and the fundamental frequency of the male's advertisement call. These seasonal-reproductive-dependent changes in thresholds varied differentially across the three (rostral, middle, and caudal) regions of the saccule. Such reproductive-dependent changes in saccule sensitivity may represent an adaptive plasticity of the midshipman auditory sense to enhance mate detection, recognition, and localization during the breeding season.

Development of a sensitive and quantitative diagnostic assay for fish nervous necrosis virus based on two-target real-time PCR

The aim of the present work was to develop two new independent SYBR Green I-based real-time PCR assays for both detection and quantification of betanodavirus, an RNA virus that infects several species of marine teleost fish causing massive mortalities in larvae and juveniles. The assays utilized two pairs of primers targeting highly conserved regions of both the RNA molecules forming the betanodavirus genome: RNA1 encoding the RNA-dependent RNA polymerase (RdRP) and RNA2 encoding the coat protein (CP). The specificity of amplifications was monitored by the melting analysis and agarose gel electrophoresis of the amplified products. The applicability of these assays was confirmed with 21 betanodavirus strains, covering all the four main clades. In addition, a BLAST (NCBI) search with the primer sequences showed no genomic cross-reactivity with other viruses. The new assays were able to quantify concentrations of betanodavirus genes ranging from 10(1) to 10(8) copies per reaction. The intra-assay coefficients of variation (CV) of threshold cycle (Ct) values of the assays were 1.5% and 1.4% for CP and RdRP RNAs, respectively. The inter-assay CVs of Ct values were 2.3% and 2.4% for CP and RdRP RNAs, respectively. Moreover, regression analysis showed a significant correlation (R2>0.97) between genome number, as determined by real-time PCR assays and the corresponding virus titer expressed as TCID50/ml of two different betanodavirus strains propagated in cell culture. The two assays were compared with a previously established one-step RT-PCR assay and with the classical virus isolation test and found to be more sensitive. In conclusion, the developed real-time RT-PCR assays are a reliable, specific and sensitive tool for the quantitative diagnosis of betanodavirus.

Characterization and comparison of fatty acyl Δ6 desaturase cDNAs from freshwater and marine teleost fish species

Fish are the most important dietary source of the n-3 highly unsaturated fatty acids (HUFA), eicosapentaenoic (EPA) and docosahexaenoic acid (DHA), that have particularly important roles in human nutrition reflecting their roles in critical physiological processes. The objective of the study described here was to clone, functionally characterize and compare expressed fatty acid desaturase genes involved in the production of EPA and DHA in freshwater and marine teleost fish species. Putative fatty acid desaturase cDNAs were isolated and cloned from common carp ( Cyprinus carpio) and turbot ( Psetta maximus). The enzymic activities of the products of these cDNAs, together with those of cDNAs previously cloned from rainbow trout ( Oncorhynchus mykiss) and gilthead sea bream ( Sparus aurata), were determined by heterologous expression in the yeast Saccharomyces cerevisiae. The carp and turbot desaturase cDNAs included open reading frames (ORFs) of 1335 and 1338 base pairs, respectively, specifying proteins of 444 and 445 amino acids. The protein sequences possessed all the characteristic features of microsomal fatty acid desaturases, including three histidine boxes, two transmembrane regions, and N-terminal cytochrome b 5 domains containing the haem-binding motif, HPGG. Functional expression showed all four fish cDNAs encode basically unifunctional Δ6 fatty acid desaturase enzymes responsible for the first and rate-limiting step in the biosynthesis of HUFA from 18:3n-3 and 18:2n-6. All the fish desaturases were more active towards the n-3 substrate with 59.5%, 31.5%, 23.1% and 7.0% of 18:3n-3 being converted to 18:4n-3 in the case of turbot, trout, sea bream and carp, respectively. The enzymes also showed very low, probably physiologically insignificant, levels of Δ5 desaturase activity, but none of the products showed Δ4 desaturase activity. The cloning and characterization of desaturases from these fish is an important advance, as they are species in which there is a relative wealth of data on the nutritional regulation of fatty acid desaturation and HUFA synthesis, and between which substantive differences occur.

Morphology, fine structure, biochemistry, and function of the spermatic ducts in marine fish

The spermatic ducts and the testicular efferent ducts were investigated in different marine teleost fish species ( Diplodus sargus, Mullus barbatus, Thalassoma pavo, Trachinus draco, Uranuscopus scaber, Sparisoma cretense, Synodon saurus). From the morphological, histological, fine structural and biochemical investigations it appeared that the testicular main ducts and spermatic ducts of the investigated marine fish have the following functions: storage of spermatozoa, monosacharide synthesis for nutrition of spermatozoa, synthesis of steroid glucuronides, synthesis of seminal plasma proteins, formation of a ionic gradient in the seminal fluid and phagocytotic activity. Species-specific differences were only found in the morphology of the gonads and in the histology of the spermatic duct epithelium.

A study of the structure and function of the pronephros in the larvae of the turbot (Scophthalmus maximus) and the herring (Clupea harengus)

Unlike most other vertebrate groups, the nephrons of the pronephroi in the larval stages of both species of marine teleost fishes were found to have an internal glomus and no nephrostomes. A novel technique, which exploited the transparency of pelagic fish larvae, was used to investigate pronephric function. Fluorescein‐labelled inulin was injected into the heart and its progress through the blood circulation and pronephric systems was recorded by confocal microscopy and quantified by image analysis. Urine flow rates (UFR) were calculated from the time course of changes in bladder volume. The ratio of inulin fluorescence in the bladder to that in the dorsal aorta was then used as a factor, with UFR, to calculate glomerular filtration rate (GFR). The relative performance of the larval pronephroi, in terms of mass‐related UFR (1.4–6.3 nl • mg−1 • h−1) and GFR (3–17 nl • mg−1 • h−1), was similar to that of the kidneys of adult fishes.

Stimulants of Feeding Behavior in Fish: Analyses of Tissues of Diverse Marine Organisms.

Analyses of the free amino acids, quaternary amines, guanido compounds, nucleotides, nucleosides, and organic acids in extracts of tissues from 10 species of marine teleost fishes and 20 species of invertebrates are reported. With multidimensional scaling techniques, the relative concentrations of the above chemicals in fishes, molluscs, and crustaceans are shown to cluster into separate taxon-specific groups. The greatest differences are between the fishes and the two groups of invertebrates. Similarities are more evident between the molluscs and crustaceans where eight of the nine most abundant substances are identical: i.e., betaine, taurine, trimethylamine oxide, glycine, alanine, proline, homarine, and arginine. The major tissue components in the fishes and invertebrates are correlated with compounds previously shown to stimulate feeding behavior in 35 species of fish. Glycine and alanine are major tissue components and are also the two most frequently cited feeding stimulants in the 35 species. Molluscs and crustaceans each contain high concentrations of five of the most frequently cited stimulants (glycine, alanine, proline, arginine, and betaine); these substances all occur in much lower concentrations in fish. Some minor tissue components, such as tryptophan, phenylalanine, aspartic acid, valine, and uridine 5`-monophosphate, are, however, important feeding stimulants for some fish species. Stimulants for herbivores and carnivores are often different. Several major feeding stimulants are substances that serve as "compensatory solutes," stabilizing enzymes and structural proteins.

Morphological analysis of the fish heart ventricle: Myocardial and connective tissue architecture in teleost species

Light and scanning electron microscopy were used to study the structure of the heart ventricle in three species of marine teleost fishes: the hake (Merluccius merluccius), the angler fish (Lophius piscatorius) and the sea bream (Pagellus centrodontus). Our findings show the ventricle to be shaped differently in each species: tubular in the hake, saccular in the angler fish and pyramidal in the sea bream. From a structural viewpoint, interest was centered on two aspects: organization of the myocardial fibres and arrangement of connective tissue. In hake and angler fish ventricles, the myocardium was exclusively trabecular in nature, whereas the bream ventricle, in addition to trabecular myocardium, presented a thin compact layer. Muscle fibres showed precise patterns of organization at the level of the ventricular orifices. With the techniques used the intramyocardial connective tissue was detected in the following ventricular zones: i) at the level of subepicardial and subendocardial spaces, ii) surrounding the myocardial fascicles, and iii) surrounding individual myocardial cells. According to this structural study, the pyramidal ventricle of the fish should be considered as a ventricular pump with greater efficiency.

Species- and Tissue-Specific Synthesis Patterns for Heat-Shock Proteins HSP70 and HSP90 in Several Marine Teleost Fishes

Using metabolic (in vivo) labeling methods and immunoblotting (Western) analysis, we determined the threshold induction temperature for enhanced synthesis of heat-shock proteins (HSP70 and HSP90) and the constitutive levels of these two classes of HSPs, respectively, in brain, gill, and liver of four species of marine teleost fishes acclimatized to a common temperature (10°C). For a given tissue of a species and among tissues of a species, little variation was found in HSP induction temperatures. However, among tissues of a species, the constitutive levels of HSPs differed substantially. Among species, wide variation was found in induction temperature (up to 8°C when averaged for all tissues) and HSP concentration (greater than 10-fobld differences for a single tissue). These results, obtained by analysis of animals from natural populations, contradict many of the assumptions, based largely on in vitro studies of isolated cells and tissues, about the dependence of the HSP threshold induction temperature a...

Characterization and distribution of undersulfated chondroitin sulfate and chondroitin in leptocephalous larvae of elopomorph fishes

Undersulfated chondroitin sulfate (i.e., chondroitin sulfate with sulfate: hexosamine molar ratios ranging from 0.06-0.17) has been identified as a principal glycosaminoglycan (GAG) in whole-body extracts of leptocephalous larvae of four species of marine teleost fishes, representing two orders and three families. These include the eels (Anguilliformes)Ariosoma balearicum (Congridae),Rhechias dubia (Congridae) and Ophichthus sp. (Ophichthidae) and the ladyfish (Elopiformes: Elopidae: Elops saurus). A second GAG found in relatively large amounts in A. balearicum has been identified as chondroitin. Chondroitin and undersulfated chondroitin sulfate formed distinctive precipitates during extraction and were easily separated. Undersulfated chondroitin sulfate also was extracted and purified from early metamorphosing bonefish (Albuliformes: Albulidae: Albula sp.) leptocephali, where it is a minor GAG component, and was shown to be similar in composition to the compounds obtained from eels and ladyfish.

Electrophoretic study of myosin isoforms in white muscles of some teleost fishes

1. 1. White skeletal muscle myosin of four marine teleost fish species (cod, blue whiting, Norway haddock, and spotted wolf-fish) was analyzed by native, SDS-PAGE, and 2-dimensional electrophoresis. 2. 2. Four types of native myosin were present in cod, blu whiting and Norway haddock. The second fastest migrating form was predominant. 3. 3. Myosin from spotted wolf-fish also resolved into four forms. The fastest migrating form was hardly noticeable. The other three were present in apparently similar amounts. 4. 4. In the myosin from each species there were three types of light chains. The pattern of light chains was species specific. 5. 5. Apparently, there was only one type of heavy chain in myosin from cod, Norway haddock and spotted wolf-fish. One preparation of cod showed an extra band of higher electroporetic mobility than the main band. In blue whiting we found two bands present in approximately equal amounts.

Partial Characterization of the Buffering Components of the Red and White Myotomal Muscle of Marine Teleosts, with Special Emphasis on Scombrid Fishes

The buffering capacity (β) of red (RM) and white (WM) myotomal muscle fibers was measured in several species of marine teleost fishes chosen to represent a broad range of locomotory ability and anaerobic capacity. WM β differed significantly among species and correlated with WM anaerobic capacity (lactate dehydrogenase activity). Tunas had the highest WM β, deep-sea fishes had the lowest β, and there were significant differences between tuna and ectothermic species in the same family (Scombridae). WM β was significantly greater than RM β. RM β did not differ intraspecifically. The components that contribute to muscle β were partially characterized by dialyzing muscle homogenates to remove all low-MW (<2,000 daltons) buffers. Thus, β caused by lowMW buffers and the protein-specific buffering capacity were estimated. Low-MW buffers contributed 48% and 67% to total β in RM and WM, respectively. Interspecific differences in WM β were due mainly to differences in low-MW buffers, but also proteins contributed m...