Interspecific and sexual differences in riverine distribution of tropical eels Anguilla spp.

A total of 261 individuals of the four tropical eel species, Anguilla celebesensis, Anguilla marmorata, Anguilla bicolor pacifica and Anguilla interioris, were collected from 12 locations around Sulawesi Island, Indonesia, to gain knowledge about the riverine distribution of tropical eels. Anguilla marmorata was predominant in the lower reaches of Poso River (94·4% of total eel catch in the sampling area), Poso Lake (93·3%), three small inlet rivers of Tomini Bay (100%) and Laa River (92·3%). Anguilla celebesensis occurred frequently in the inlet rivers of Poso Lake (63·5%). Anguilla bicolor pacifica and Anguilla interioris were rare (1.5% and 0.4%, respectively). Otolith Sr:Ca ratio electron-probe micro analysis (EPMA) for individual migratory histories revealed that 15 A. celebesensis caught in Poso Lake and its inlet rivers were categorized into 14 river eels (Sr:Ca < 2·5) showing upstream migration seemingly at their elver stage and only one sea eel (Sr:Ca ≥ 6·0) that stayed in the marine habitat for the majority of its life after recruiting to Sulawesi Island before its late upstream migration. In A. marmorata, 19 examined eels from Poso Lake and its inlet rivers were all river eels, while 17 eels from the lower reaches of Poso River were two river eels, six sea eels and nine estuarine eels (2·5 ≤ Sr:Ca <6·0) that mostly lived in the brackish water. The sex ratio of A. celebesensis was highly skewed towards a dominance of females (99%). In A. marmorata, females were predominant in Poso Lake (95·2%), its inlet rivers (94·7%) and Laa River (100%), while males were more frequent in the lower reaches of Poso River (76·5%) and small inlet rivers of Tomini Bay (94·1%). These results indicate that the riverine distribution pattern of tropical eels differs among species and between sexes. This article is protected by copyright. All rights reserved.

Age and growth of migrating tropical eels, Anguilla celebesensis and Anguilla marmorata.

The age and growth of migrating tropical eels, Anguilla celebesensis and Anguilla marmorata from central Sulawesi, Indonesia, were examined. Migrating eels (63 A. celebesensis and 38 A. marmorata) were obtained from weirs near the Poso Lake outlet and non-migrating eels (35 A. celebesensis and 119 A. marmorata) were captured by baited hooks, eel pots, scoop net and electro-fishing in the Poso River system, Laa River system, Baluga River, Tongku River and Padapu River from February 2009 to October 2010. In both species, the proportion of eels with opaque otolith edges showed a single peak in July, suggesting that one annulus (a pair of translucent and opaque zones) was formed each year in their otoliths. Mean ± s.d. and range of total length (LT ) and age was 785·2 ± 114·9 (585-1083) mm and 7·5 ± 1·6 (5-11) years in migrating female A. celebesensis and 1132·2 ± 173·7 (800-1630) mm and 11·6 ± 3·3 (7-23) years in A. marmorata. The age of migrating female eels was negatively correlated with annual growth rate, 100·7 ± 17·2 (68·1-145·0) mm year-1 in A. celebesensis and 97·9 ± 19·3 (66·6-131·6) mm year-1 in A. marmorata, but there was no significant correlation between the LT and annual growth rate in either species. The annual growth rates of these female tropical eels were typically higher than those of temperate anguillid species, suggesting a latitudinal cline in growth rate in the genus Anguilla reflecting the environmental conditions of their growth habitat.

Geographic distribution and environmental control of vertebral count in Ammodytes spp. along the northern Pacific coast of Japan.

To examine species composition and population structures in sand lance (Ammodytidae) along the northern Pacific coast of Japan, genetic analysis were carried out for specimens collected in 2014 from Otsuchi Bay, Iwate, Ishinomaki Bay, Miyagi, off Soma, Fukushima and Ise-Mikawa Bays, Aichi. The samples consisted of Ammodytes japonicus and Ammodytes heian, of which the latter is a recently described species. Neither species exhibited significant genetic differences among localities. Only A. japonicus was found in the most southern locality at Aichi, but it decreased northward to <90% in Miyagi and Fukushima and the two species occurred almost evenly in Iwate suggesting a latitudinal cline in their species composition along the northern Pacific coast of Japan, off Tohoku. The vertebral counts differed between A. japonicus and A. heian with modes of 65 and 63, respectively, but this characteristic did not differ significantly within a locality (Iwate). This suggests that the vertebral counts of Ammodytes spp. in Japanese waters are probably strongly determined by the environment than by a species-specific genetic trait.

Head-shape polymorphism in Japanese eels Anguilla japonica in relation to differences of somatic growth in freshwater and brackish habitats.

The age, total length (L(T)), head shape and skull shape were investigated for 379 Japanese eels Anguilla japonica sampled in freshwater and brackish areas of the Kojima Bay-Asahi River system, Okayama, Japan, to learn about the differentiation process of head-shape polymorphism. The relative mouth width (ratio of mouth width to L(T)) of A. japonica > 400 mm L(T) collected in fresh water was significantly greater than that of fish collected in brackish water. Growth rates of mouth width and the distance from the snout to the midpoint of the eyes (the ratio of width and distance to age, respectively) were not significantly different between freshwater and brackish-water samples, whereas the somatic growth rate (the ratio of L(T) to age) of freshwater samples was significantly lower than that of brackish-water eel samples. These results suggest that the factors affecting head and somatic growth of A. japonica are not identical. According to these results and feeding patterns in each habitat reported by another study, it is suggested that somatic growth appears to play a significant role in the differentiation process of the head-shape polymorphism in A. japonica, with the slow-growing fish in fresh water becoming broad-headed and the fast-growing fish in brackish water becoming narrow-headed.

Morphological and physiological changes of female tropical eels, Anguilla celebesensis and Anguilla marmorata, in relation to downstream migration.

The morphological and physiological characteristics of migrating and non-migrating female tropical eels, Anguilla celebesensis and Anguilla marmorata were examined in relation to their downstream migration on central Sulawesi Island, Indonesia. Migrating eels (64 A. celebesensis and 37 A. marmorata) were obtained from weirs set near the outlet area of Poso Lake and non-migrating eels (21 A. celebesensis and 21 A. marmorata) were sampled by set-lines and eel pots in Poso Lake, its inlet rivers, and in the La River system during February 2009 to October 2010. In both species, values of eye index, pectoral-fin length index, gonado-somatic index (I(G)), hepato-somatic index, swimbladder-somatic index and cardio-somatic index of migrating eels were significantly higher than those of non-migrating eels and the gut-somatic index values of the migrating eels were significantly lower than that of non-migrating eels. When silvering stages of eels were classified by the silvering index for Anguilla japonica, in A. celebesensis, all non-migrating eels were Y1 stage and the migrating eels consisted of Y2, S1 and S2 stages eels. In A. marmorata, the non-migrating eels consisted of Y1 and Y2 eels, and the migrating eels consisted of Y2 and S1 eels, but there were no S2 eels. Results of principal component analysis (PCA) of morphological and physiological variables suggested that these characteristics changed drastically between the Y1 and Y2 stages in A. celebesensis, while A. marmorata showed a gradual change with silvering, which differs from the temperate species A. japonica. The mean ±S.D. I(G) value of migrating A. celebesensis (6.9 ± 1.8, 3.3-11.4) was very high and that of A. marmorata (3.1 ± 0.8, 1.8-5.7) was comparatively low. The very different rates of maturation that were found between these two species provide support for the hypothesis that the reproductive characteristics of silver eels can reflect their migration scale.

Depth distribution and biological characteristics of the European eel Anguilla anguilla in Lough Ennell, Ireland.

Using a longline survey, a total of 196 European eels Anguilla anguilla were collected at different depths in Lough Ennell (maximum depth 30 m), central Ireland. The catch per unit of effort of A. anguilla that were caught from 1 to 25 m depths was lowest at 0.5-5.0 m and greatest at the deepest depth range (22.5-25.0 m). Sub-samples of A. anguilla from depths of <15 m showed little or no difference in size, sex ratio, age, growth rate, condition factor, length-mass relationship, gonado-somatic index, fin index or eye index with fish from depths of >15 m. All fish examined were female yellow-phase A. anguilla that had ages from 7 to 20 years (mean +/-s.d. = 10.3 +/- 2.9 years), with growth rates from 24.0-60.8 mm year(-1) (mean +/-s.d. = 40.7 +/- 8.5 mm year(-1)). Variations in the growth rates were greater in the shallow group than that of the deep group. This study suggested that deeper regions are important feeding habitats for A. anguilla and that fish in this lake were growing moderately fast compared to similar habitats and areas in the species' range.

Sympatric spawning of Anguilla marmorata and Anguilla japonica in the western North Pacific Ocean.

Extensive collections were made of the larvae of the temperate Japanese eel Anguilla japonica and the tropical giant mottled eel Anguilla marmorata in an overlapping area of the North Equatorial Current region of the western North Pacific Ocean. Collections of 189 A. marmorata and > 2500 A. japonica larvae during nine surveys from 1991 to 2007 showed that these two anguillid eels have similar spawning areas just west of the southern West Mariana Ridge. In July to August 2006 and August 2007, morphologically and genetically identified A. marmorata preleptocephali were mainly collected between 14.5-15 degrees N and 142-142.5 degrees E, where A. japonica preleptocephali were also caught in some of the same net tows. Fewer A. marmorata preleptocephali, however, were collected (n = 31) compared to those of A. japonica (n = c. 165), and fewer small larvae of A. marmorata were collected per tow than A. japonica (n = 1-10 and 1-294, respectively), suggesting relatively smaller spawning aggregations of A. marmorata. The distribution of preleptocephali and small larvae was wider in longitude in A. marmorata (131- 143 degrees E) than in A. japonica (137-143 degrees E), while the latitudinal range was almost the same (12-17 degrees N). Although spawning by these two species overlaps both spatially and temporally, the tropical eels of the North Pacific population of A. marmorata probably have a much longer spawning season with fewer spawners, at least in summer, and recruit to a much wider latitudinal range of growth habitats.

Influence of water temperature and feeding regime on otolith growth in Anguilla japonica glass eels and elvers: does otolith growth cease at low temperatures?

The influences of water temperature and feeding regime on otolith growth in Anguilla japonica glass eels and elvers were investigated using individuals reared at 5, 10, 15, 20, 25 and 30 degrees C and in fed or unfed conditions at salinity 32 after their otoliths were marked with alizarin complexone (ALC). To eliminate the difficulty of observing the edges of otoliths with optical (OM) or scanning electron (SEM) microscopes, three to 10 individuals were sampled from each tank at 10, 20 and 30 days during the experiment and reared for an additional 10 days at 25 degrees C after their otoliths were marked a second time. Otolith growth and the number of increments were measured using both OM and SEM. Most A. japonica commenced feeding after 10 days at 20-30 degrees C or after 20 days at 15 degrees C, but no feeding occurred at 5 and 10 degrees C. No otolith growth occurred at 5 and 10 degrees C except in two individuals with minimal increment deposition at 10 degrees C. Otolith growth was proportional to water temperature within 15-25 degrees C and not different between 25 and 30 degrees C. At 15, 25 and 30 degrees C, the mean otolith growth rate in fed conditions was higher than in unfed conditions. The number of increments per day was significantly different among water temperatures (0.00-0.01 day(-1) at 5 and 10 degrees C, 0.43-0.48 day(-1) at 15 degrees C and 0.94-1.07 day(-1) at 20-30 degrees C). These results indicated that otolith growth in A. japonica glass eels and elvers was affected by temperature and ceased at < or =10 degrees C under experimental conditions. Hence, future studies analysing the otoliths of wild-caught A. japonica glass eels and elvers need to carefully consider the water temperatures potentially experienced by the juveniles in the wild.

Morphological and meristic evaluation of the population structure of Anguilla marmorata across its range.

The population structure of the giant mottled eel Anguilla marmorata was evaluated using statistical analysis of 21 morphological characters among 13 representative localities across the Indo-Pacific region and as far north as Japan. There were no clear differences in 15 proportional and six vertebral characters using principal component analysis. The total number of vertebrae (N(V)) of A. marmorata at these localities had the widest variation among the morphological and meristic characters examined. A statistical analysis of the N(V) of 1238 specimens from 14 localities that included previously published data found significant differences among Micronesia, French Polynesia and other localities, and between localities in the North Pacific and South Pacific regions. Few differences were detected between specimens from the Indian Ocean and the North Pacific or South Pacific regions. The differences in N(V) among some regions and the population genetic studies of this species indicate that there are at least four populations of A. marmorata (North Pacific, Micronesia, Indian Ocean and South Pacific), which appear to include metapopulation structures in the Indian Ocean and South Pacific. This population structure is consistent with the ocean current patterns in each region and the evolution of migration loops of each spawning population.

Shear properties of the temporomandibular joint disc in relation to compressive and shear strain.

Shear stress can result in fatigue, damage, and irreversible deformation of the temporomandibular joint disc. Insight into the dynamic shear properties of the disc may give insight into the mechanism inducing tissue failure due to shear. We tested the hypothesis that the dynamic shear properties of the disc depend on the amount of shear and compressive strain. Twenty-four porcine discs were used for dynamic shear tests. The specimens were clamped between the plates of a loading apparatus under compressive strains of 5%, 10%, and 15%. Dynamic shear was applied to the specimen by a sinusoidal strain of, respectively, 0.5%, 1.0%, and 1.5%. Both the dynamic elasticity and viscosity were proportional to compressive strain and inversely proportional to shear strain. These shear characteristics suggest a significant role of compressive and shear strain on the internal friction of the disc.

Dynamic properties of bovine temporomandibular joint disks change with age.

The temporomandibular joint disk exhibits morphological and biochemical age-related changes. However, the possible age-related changes of the dynamic viscoelasticity in the disk are unclear. We tested the hypothesis that the dynamic viscoelastic properties of the disk change with age. Thirty-six disks from young-adult, adult, and mature-adult cattle were used for dynamic tensile tests. In all disks, the magnitudes of the complex modulus, the storage modulus, and the loss modulus increased as the frequency increased. The mature-adult disks had higher values of these moduli than did the younger disks. The loss tangent ranged from 0.1 to 0.3, which means that the disk has relatively large elasticity and relatively small viscosity. It was concluded that both the elasticity and viscosity of the disk increase with age. This may reflect age-related changes in biochemical composition.

Biomechanical response of bovine temporomandibular joint disc to prolonged tensile stress.

This study was designed to evaluate the influence of prolonged tensile stress on the viscoelasticity of the temporomandibular joint (TMJ) disc. Twenty discs from 10, 3-year-old cattle were used. Tensile stress of 1.5 MPa was applied to specimens from the discs for 10, 20, 40 and 60 min. Following the prescribed period of tension for creep, the specimens were removed from the tension device and any recovery observed for 20 min. In all specimens, strain increased at the onset of stress application and reached almost steady conditions after 5 min. Although, the strain became slightly larger when the creep time was longer, no significant differences were found in the strains between any two tests with different periods of creep. The residual strain increased significantly with creep duration, and similarly the degree of recovery decreased significantly. In 10- and 20-min creep tests, the residual strains were 0.1 and 1.0%, the specimens in 40- and 60-min tests revealed irreversible changes in length. It was concluded that continuous loading for >40 min causes creep damage in bovine TMJ disc, and that prolonged sustained tension affects the recovery of joint homeostasis.

Viscoelastic properties and residual strain in a tensile creep test on bovine temporomandibular articular discs.

This study was designed to evaluate the creep characteristics and residual strain of bovine temporomandibular joint (TMJ) discs in tension. Twenty discs were divided into three specimens each: central, lateral and medial regions. Tension of 1.0 MPa was applied and sustained for 20 min to the specimens from 10 right-side discs, and tension of 1.5 MPa to specimens from 10 left-side discs. After the period of tension for creep, the specimens were removed from the tension devices and restoration observed for 20 min. Time-dependent creep curves showed a marked change in strain during the initial 5s. The essential time delay in strain ceased after 2 min, and strain reached an almost steady level after 3 min. At a tensile stress of 1.5 MPa, a strain of 14.5% on average was produced after 20 min creep in the central specimens; peripheral specimens showed strains of 12.4% on average. There were significant differences in strain between the central and peripheral specimens. The residual strain after 20 min restoration was 0.93% on average and there were no significant regional differences. This creep feature could be well represented by a generalized linear viscoelastic model. It was concluded that the regional differences in viscoelasticity might be caused by the complicated articulating functions of the TMJ, and that the residual strain caused by sustained stress could be an important factor in disc deformation.

Biomechanical behaviour of bovine temporomandibular articular discs with age.

The purpose was to evaluate age-associated changes in the creep and restoration properties of bovine temporomandibular joint (TMJ) discs under and after sustained tensile stress. Forty discs were obtained from 7- and 10-year-old cattle, referred to as the adult and mature adult groups, respectively. Tension of 1.0 MPa was applied and sustained for 20 min to specimens from ten right discs and of 1.5 MPa to specimens from ten left discs. After the period of tension for the study of creep, the specimens were removed from the tension devices and their restoration observed for 20 min. For comparative purposes the relevant results for a young adult group were recruited from data on 3-year-old bovine TMJ discs reported in a previous study on viscoelastic properties. In all the specimens the time-dependent creep curves showed a marked change in strain during the initial 5 s, but the elastic moduli at the onset of stress were significantly larger in the mature adult group than in the other groups. After 20-min creep, the strains were decreased in relation to the age of the specimen and were significantly smaller in the mature adult than in the young adult. With regard to regional differences, the medial specimens exhibited significantly smaller strains than the central ones in all three age groups. Furthermore, the residual strains after 20-min restoration also decreased slightly with age. It is concluded that the bovine TMJ disc becomes stiff and acquires the capacity to recover from continuous deformation during growth and maturation. These findings suggest that the TMJ disc can modify its viscoelasticity in order to withstand extrinsic functional stresses.

Molecular phylogeny and evolution of the freshwater eel, genus Anguilla.

A molecular phylogenetic analysis was conducted on all of the known catadromous eel species of the genus Anguilla to assess their relationships and evolutionary history. The analyses of a total of 1427 bp of the mitochondrial 16S ribosomal RNA and 1140 bp of the complete cytochrome b gene sequences suggested that the genus Anguilla was monophyletic in origin, with A. borneensis as the most basal species. Four clades/species groups that correspond to their geographical ranges were indicated, Indo-Atlantic (three species), Oceania (two species), tropical Pacific (two species), and Indo-Pacific (five species), with ambiguous positions for A. japonica and A. reinhardti. This grouping conflicts with that of a previous morphological study, since the broad undivided maxillary and short-fin type, which were thought to be phylogenetically important, were paraphyletic in the molecular analysis. However, the molecular phylogeny and the present geographic distribution of species suggested historical dispersion of the genus Anguilla according to the Tethys corridor hypothesis, which proposed that anguillid eels originated near present-day Indonesia and dispersed westward along paleo-circumglobal equatorial currents. The westward-moving strain entered the paleo-Atlantic through the Tethys Sea and was ancestral to present-day European and American species.

Identification of rat and human cytochrome P450 forms involved in the metabolism of the thromboxane A2 receptor antagonist (+)-S-145.

(+)-S-145 [5-(+)-(Z)-7-[(1R, 2S, 3S, 4S)-3-phenylsulfonylaminobicyclo[2.2.1]hept-2-yl]-heptenoic acid] and its beta-oxidized metabolites [two [bisnor or dihydro (DH)-bisnor] or four (tetranor) carbon-shortened products at the carboxyl side chain] are hydroxylated at the C-5 or C-6 position of the bicyclo ring by microsomal monooxygenases. We investigated the oxidative metabolism of (+)-S-145 and its beta-oxidized metabolites with liver microsomes from rats and humans to identify which cytochrome P450 (P450) forms are involved in these reactions. In rats, phenobarbital or dexamethasone treatment significantly increased 5- and 6-hydroxylation activities toward (+)-S-145 and its beta-oxidized metabolites, suggesting the involvement of P4503A forms. Immunoinhibition studies suggested that P4503A2 was mainly responsible for the 5-hydroxylation of (+)-S-145, bisnor, and DH-bisnor and the 6-hydroxylation of bisnor and tetranor. Furthermore, P4502C6, a phenobarbital-inducible 2C form in the rat, was involved in the 6-hydroxylation of (+)-S-145, bisnor, and DH-bisnor. P4502C11, the major constitutive form (male rats), was partly involved in the 5-hydroxylation of DH-bisnor and the 6-hydroxylation of bisnor and DH-bisnor. Reconstitution studies with purified human enzymes and immunoinhibition studies suggest that P4503A4 is primarily involved in the 5-hydroxylation of (+)-S-145 and bisnor and the 6-hydroxylation of tetranor; P4502C9/10 mainly catalyzed the 5-hydroxylation of tetranor and the 6-hydroxylation of (+)-S-145. Results of the present study indicated that the same subfamily P450 forms are responsible for the oxidative metabolism of (+)-S-145 in rats and humans. P4503A enzymes were shown to be involved in the formation of 6-hydroxy tetranor, the main metabolite of S-1452 in vivo.

Evolution of the freshwater eels.

The freshwater anguillid eels have an unusual life history and world-wide distribution. Questions about the phylogenetic relationships of this group and how their long spawning migrations and larval phase may contribute to their global distribution have not been addressed. This paper is first presentation of molecular phylogeny of Anguilla species, and based on this phylogenetic tree we suggest new aspect of the evolution of this group. Namely, ancestral eels originated during the Eocene or earlier, in the western Pacific Ocean near present-day Indonesia. A group derived from this ancestor dispersed westward, probably by larval transport in the global circum-equatorial current through the northern edge of the Tethys Sea. This group split into the ancestor of the European and American eels, which entered into the Atlantic Ocean, and a second group, which dispersed southward and split into the east African species and Australian species. Thus the world-wide distribution of the eel family can be understood from knowledge of continental drift, ocean currents, a specialized larva and evolutionary forces favoring dispersal and speciation of segregated gene pool.

Interaction between human polymorphonuclear leucocytes and bacteria released from in-vitro bacterial biofilm models.

The interactions between phagocytic cells (polymorphonuclear leucocytes) and Escherichia coli cells released from a biofilm model formed in vitro on the surface of cotton threads in an artificial medium were compared with those of phagocytes and bacteria released from a newly developed in-vitro biofilm model. This new model of bacterial biofilm on the surface of cotton threads was developed by soaking cotton threads in rat carboxymethylcellulose pouch exudate and culturing E. coli in the exudate. The structure of the biofilm model and the surface structure of the bacteria in the biofilm resembled those observed in vivo in infected pouches, and they were quite different from those observed with the biofilm model in artificial medium. Both bacteria released from biofilm models in an artificial medium and those from biofilms in rat carboxymethylcellulose pouch exudate, in vitro, were almost equally resistant to killing by phagocytes. The sensitivity of these bacteria to phagocytosis was no different from that of normal bacteria grown in artificial medium. Bacteria from both models were also less sensitive to the killing activity of H2O2. Electronmicroscopy showed that bacteria from both models had some products that interacted with ruthenium red on their surfaces, but the respective quantities of these products differed.

Third complement component in cerebrospinal fluid in neuro-Behçet's syndrome. Conversion patterns by crossed immunoelectrophoresis.

Thirteen cerebrospinal fluid specimens (CSFs) from 10 patients with neuro-Behçet's syndrome (nB) were examined for the presence of conversion products of C3 protein by means of crossed immunoelectrophoresis. C3 conversion products were found in 4 CSFs from nB patients, and the proportions of the split products to the total immunoprecipitate zones were 17, 34, 61 and 63%, respectively. CSFs with C3 conversion patterns showed higher C3 protein (beta 1C/A) levels compared with those with non-conversion, whereas the differences of C4 protein (beta 1E) levels were unremarkable. CSF with C3 conversion patterns also showed apparent inflammatory characteristics indicating blood-CSF barrier involvement which would be deduced from increased alpha 2-macroglobulin and IgA, both being regarded as sensitive internal barrier parameters: but IgA measurement was much higher than usually expected values. It is suggested that the increase in CSF C3 might be initiated by accelerated consumption of complement through the alternative pathway, leading to hypersynthetic or hyperinflux response in CSF.