Dietary-morphological relationships of fishes in Liangzi Lake, China

Species in Liangzi Lake were clustered into four trophic groups: Hemiramphus kurumeus and Hemiculter bleekeri bleekeri fed predominantly on terrestrial insects; Carassius auratus auratus and Abbottina rivularis on non-animal food; Hypseleotris swinhonis, Ctenogobius giurinus, Pseudorasbora parva and Toxabramis swinhonis on cladocerans or copepods; Culterichthys erythropterus on decapod shrimps. Gut length, mouth width, mouth height, gill raker length and gill raker spacing, varied widely among species. With the exception of three species pairs ( H. swinhonis, C. giurinus; C. erythropterus, H. kurumeus; T. swinhonis, H. bleekeri bleekeri ), principal components analysis of morphological variables revealed over-dispersion of species. Canonical correspondence analysis of dietary and morphological data revealed five significant dietary-morphological correlations. The first three roots explained > 85% of the total variance. The first root reflected mainly the relationship of gut length to non-animal food, with an increase in gut length associated with an increase in non-animal food. The second root was influenced strongly by the relationship of the gill raker spacing to consumption of copepods, with an increase in gill raker spacing associated positively with copepods in the diet. The third root was influenced by the relationship of mouth gape to consumption of fish and decapod shrimps, with an increase in mouth gape associated with more fish and decapod shrimps in the diet. These significant dietary-morphological relationships supported the eco-morphological hypotheses that fish morphology influence food use, and morphological variation is important in determining ecological segregation of co-existing fish species.     

Feeding ecology of larval and juvenile black seabream (Acanthopagrus schlegeli) and Japanese seaperch (Lateolabrax japonicus) in Tolo Harbour, Hong Kong

Black seabream, Acanthopagrus schlegeli, and Japanese seaperch, Lateolabrax japonicus, are important commercial species in the coastal waters of western Pacific Ocean, including Japan, Korea and China. In Hong Kong, larvae and juveniles of these two species occur in bays and estuaries during late winter and spring. This study reports on the ontogenetic changes in food habits in larvae and juveniles of these species in an artificial rocky shore area. Copepods and cladocerans were the most numerous food items for black seabream. There was a shift to larger and benthic prey as the fishes grew. Japanese seaperch <2.1cm fed predominantly on copepods and cladocerans, while larger prey were added as fish size increased. Japanese seaperch >6.0cm were piscivorous. Maximum prey width increased with fish standard length and mouth gape width in both species. Overall, black seabream showed greater diet breadth than did Japanese seaperch. In black seabream, diet breadth increased with fish size. In Japanese seaperch, diet breadth increased with size for fishes <4.0cm, then decreased as the fishes became piscivorous. Prey selectivity in black seabream was determined using information on prey availability in plankton samples. In general, preference was stronger for cypris larvae, Penilia avirostris and decapod larvae than for copepods and podonids. In recent years, overfishing and environmental degradation have led to the decline of fish populations in Tolo Harbour. Absence of fishes with empty gut indicates that inner Tolo Harbour is still an important nursery area for these two commercial species.     

Digestive tract morphology of the Neotropical piscivorous fish Cichla kelberi (Perciformes: Cichlidae) introduced into an oligotrophic Brazilian reservoir

Despite being one of the most well-known cichlid fish of importance to artisanal and sport fishing, and among the largest fishes in the Neotropics, data on digestive tract anatomy of peacock basses (Cichla spp.) are largely lacking, especially for non-native populations. In this paper, we describe for the first time the digestive tract morphology of Cichla kelberi, a voracious piscivore that was introduced in the 1950s into an oligotrophic and physically low-complex impoundment in Brazil. Peacock basses were collected between 1994 and 2002 in Lajes Reservoir, through gillnets (25 to 55mm mesh; 20-50 x 2m), seines (10 x 2.5m; 8.0mm mesh), cast nets and angling. All the fishes were kept on ice in the field and then transferred to the laboratory, where they were identified, measured, weighed and dissected for digestive tract analyses. The Index of Relative Importance-IRI was calculated for diet characterization while linear and non-linear regressions were performed to assess growth patterns of four morphological characters related to feeding (e.g. mouth width, mouth height, stomach length and intestine length) and the number of gill rakers during the C. kelberi ontogeny. Most digestive tract structures were directly related to the piscivorous diet of C. kelberi, indicating that peacock bass is a diurnal, bathypelagic and gape-size limited predator that feeds largely on shallow-water prey species within the littoral zone. Mouth width and height grew allometrically (b > 1) with the size of peacock bass, broadening the size range in which prey can be eaten, but especially for predators smaller than -400mm of total length. Differently, stomach and intestine lengths increased isometrically (b = 1), which could constrain prey consumption for adult C. kelberi, especially those at advanced stages of gonadal maturation. The presence of longer-drawn, sharp and furcated gill rakers in C. kelberi may be related to increased prey retention in the resource-limited Lajes Reservoir, but further studies are necessary whether such features are randomly triggered by genetic or phenotypic anomalies, or effectively bring ecological advantages to the predator. In addition to contribute to improve the current biological knowledge on peacock basses, our results can be also useful to further comparisons on whether those morphological features related to feeding will change with transitions on prey consumption by C. kelberi and/or with the particular conditions of the invaded ecosystem.     

Feeding habits and seasonal trophic guilds structuring fish community in the bay mouth region of a tropical estuarine habitat

Understanding trophic relationships of fish in estuarine ecosystem is an important element for sustainable resource management. This study examined the feeding habits of 29 dominant fish species, characterized the trophic guilds, assessed the impact of season and clarified the role of diets in structuring the fish community in the mouth region of Pattani Bay, Thailand. Samples of 5792 fishes collected monthly by gillnets from March 2019 to February 2020 were used for stomach content analyses. It was found that the number of food types and fullness index differed between fish taxa (P < 0.001). Most fishes were specialist feeders feeding on specific food components and were categorized into five trophic guilds: piscivore, shrimp-fish feeder, polychaete feeder, zooplanktivore and planktivore. Six species were piscivorous, considered as apex predators, that fed almost entirely on fishes. High diet overlaps among some species (>0.6) were recorded. Not much variation in seasonal guilds was observed: four guilds in the dry season, three in the moderate rainy season and four in the rainy season. Some species remained in the same guild the whole year round, but some fishes changed seasonally. Two fish communities from different regions of the bay were segregated based on feeding habits. The inner bay community comprised mainly copepod and plankton feeders, but there were more piscivores in the deeper bay mouth area. Results from this study help us to understand the feeding habits and trophic guilds of dominant fish species at the mouth of this tropical estuarine bay.     

Ecological structure of tropical fish assemblages in wet-zone streams of Sri Lanka

The introduction of four fish species into a depauperate stream system in central Sri Lanka provided a 'natural experiment' that enabled us to determine the ecological structure of wet-zone stream fish assemblages. All the species indigenous to this 'introduction' stream system also co-occur naturally with the introduced species in nearby streams. Analyses of habitat use and dietary requirements revealed that most species in the assemblages were segregated on the basis of macrohabitat, microhabitat and food, regardless of origin of the fishes. Macrohabitat and microhabitat utilizations by species were similar in each stream of the 'introduction' system despite differences in stream conditions. Thus species distributions, relative to each other in ecological space, were consistent among streams, and with the combined data. High overlaps along the resource axes of velocity, depth, substratum and food were few. A major proportion of the high overlaps was due to associations with introduced species; especially Barbus nigrofasciatus and Barbus cumingii. The other two introduced species, Barbus titteya and Rasbora vaterifloris , were more specialized, and interacted relatively less with indigenous species. The indigenous species, however, exhibited pronounced complementarity along three resource axes representing depth, velocity and food. Rasbora vaterifloris and B. nigrofasciatus grew to larger sizes in one stream which had fewer indigenous species, suggesting competitive release. In this stream, the most common indigenous species was a dietary specialist that fed on diatoms, and B. nigrofasciatus , which fed heavily on diatoms in other streams, switched to feeding more on macrophytes. Overall, the data suggest that these assemblages are predictable, co-evolved systems with competition serving as an important structuring force that reinforces species segregation.     

Sexual dimorphism of external morphological characters in some deepwater skates (Rajidae,Rajiformes, Chondrichthyes) of the North Atlantic

Our studies of the external morphology of five species of deepwater skates (Amblyraja jenseni, Bathyraja pallida, B. richardsoni, Rajella bigelowi, and R. kukujevi) showed that their males and females differ significantly in 9 characters in the first species, 14 characters in the second, 11 characters in the third and fourth, and 10 characters in the fifth. Sexual differences occur most frequently in the length of the first gill slit (in four species out of five), the length of the nasal curtain, the mouth width, and the length of the third gill slit (in three species out of five), the width and length of the disc, the length of the first and second dorsal fin bases, the tail height at the tip of the ventral fin, the length of the fifth gill slit, the distance between the first and fifth gill slits, the interspiracular distance, the preanal length, distance from the tip of the snout to the maximum disc width, and the interorbital distance (in two species out of five).     

Morphological correlates with diet of fish assemblages in brush park fisheries of tropical estuaries

Brush park fishery in Negombo estuary, Sri Lanka is a traditional fishing practice which relies on fishes attracted to artificial woody fish aggregation devices. This study investigates whether constituent species in these brush parks exhibit morphological variations in relation to their dietary habits. Fishes caught in brush parks were sampled from April 2014 to April 2016 covering rainy, intermediate and dry seasons. There were 817 specimens of 46 species belonging to 24 families. From each specimen, 17 morphological attributes were determined and diet composition of each species was analyzed in terms of relative biovolume. Trophic index of each species estimated from the proportions of dietary items and their possible trophic level in the community was significantly related to two body proportions (Maximum body height/Maximum body width and Total length/ Maximum body height) which described shape of fish. Principal component analysis of morphometric attributes and dietary habits indicated that the species in the higher trophic levels are characterized by slender, long-body shapes and those occupy lower trophic levels are predominantly laterally compressed with deep body shapes. As such, structure of coexisting species in brush parks of Negombo estuary is predominantly along the trophic dimension and is related to morphological traits of constituent species. The predictive power of ecomorphological correlates with diets of fish species other than mugilids which are attracted to brush parks, can therefore be considered as a useful tool for conducting rapid ecological assessment.     

Depauperate freshwater fish communities in Sabah: the role of barriers to movement and habitat quality

Up to 30 species of fish were generally found in medium-sized rainforest streams in Sabah, Malaysia. However, depauperate fish communities were found in two streams above large (>8 m) waterfalls (five and nine species) and in two very small streams located in deep forest (five and six species). A fifth stream with small cascades and waterfalls had a faunal list of 12 species. Species resident above waterfalls were predominantly herbivores while fishes in the two forest streams were from a variety of trophic groups. Abundance and biomass of fishes above waterfalls were significantly lower than all other sites. A translocation experiment was performed in one stream to distinguish between the hypotheses that fish communities above waterfalls were determined solely by colonization ability and were unsaturated with species or that they were limited by habitat quality or food. Seven species (775 individuals) were trans located into one isolated section and four species (570 individuals) into another. Species that were trans located included trophic groups that were not represented by resident species. Twelve months after translocation, only four and one trans located species were collected in the two sections, all at greatly reduced densities. After 20 months, the number of species were three and two, respectively. One trans located species, Rasbora sumatrana , had increased in abundance from 12 months and juveniles were present in the population. Individuals of other trans located species appeared to be remnants of stocked populations. Abundance and biomass of resident species fluctuated widely between years. Interpretation of results was complicated by a large flood which substantially changed habitat conditions about a month after translocations were performed. It is suggested that two different factors were responsible for depauperate communities: movement barriers for waterfall sites and physicochemical conditions and/or habitat availability at other sites.     

Morphology–diet relationships in four killifishes (Teleostei, Cyprinodontidae, Orestias) from Lake Titicaca

This study explores the relationship between morphology and diet in four Andean killifishes ( Orestias ) from Lake Titicaca that are known to differ in habitat use. Species that fed preferentially on amphipods ( Orestias albus ) or molluscs ( Orestias luteus ) separated in multivariate space from other species that feed on cladocera and algae ( Orestias agassii and Orestias jussiei ). Generally, specimens feeding on cladocera were characterized by a short, blunt nose with a small mouth; whereas, specimens feeding on amphipods exhibited a long snout with a large mouth. Specimens including molluscs in their diet tended to have a larger posterior part of the head and the larger opercles than others; while the occurrence of substratum in gut content was generally related to a short but deep head. The present analysis suggests that the littoral O. jussiei has an intermediate phenotype and diet between the pelagic ( O. agassii ) and benthic ( O. albus and O. luteus ) species. Results suggest that resource partitioning was occurring and that several morphological traits relate to characteristics of the diet, and it is inferred that the benthic, the pelagic and the littoral zones in the lake host different prey communities constituting distinct adaptive landscapes.     

鲱科鱼类消化系统和鳔的比较研究

本文对鲱科5亚科、9属9种鱼类的消化系统和鳔作了比较研究。鲱科鱼类主食浮游生物、硅藻和有机碎屑。口小。齿小或退化。鳃耙发达,细长数多,具滤食作用。有些种类具咽上器官。胃呈Y型和U型。斑(鱼祭)的幽门胃壁肌肉屡增厚,它们主食浮游植物,肠长而盘曲多。所有鲱科鱼类均具幽门盲囊,鳔分支向前经耳囟延伸至内耳区,有些有后鳔管孔通外界。鳔有3式型和2亚型。     

Changes in the small intestine of Schistosoma mansoni-infected mice fed a high-fat diet

The consumption of a high-fat diet modifies both the morphology of the small intestine and experimentally tested effects of schistosomiasis mansoni. However, whether a schistosomiasis infection associated with a high-fat diet causes injury to the small intestine has never been investigated. Mice were fed either a high-fat or a standard-fat diet for 6 months and were then infected with Schistosoma mansoni cercariae. Physical characteristics of the intestinal tissue (mucosal thickness, small intestinal villi length and height, and abundance of goblet cells and enterocytes on the villous surface) and the distribution of granulomas along the intestinal segments and their developmental stage were measured at the time of sacrifice (9 or 17 weeks post-infection). The group fed a high-fat diet exhibited different granuloma stages, whereas the control group possessed only exudative granulomas. The chronically infected mice fed a high-fat diet exhibited higher granuloma and egg numbers than the acutely infected group. Exudative, exudative/exudative-productive and exudative-productive granulomas were present irrespective of diet. Computer-aided morphometric analysis confirmed that villus length, villus width, muscular height and submucosal height of the duodenal and jejunal segments were affected by diet and infection. In conclusion, a high-fat diet and infection had a significant impact on the small intestine morphology and morphometry among the animals tested.     

三种共栖蝙蝠的回声定位信号特征及其夏季食性的比较

2005年6至9月,对桂林市郊区两个山洞中高颅鼠耳蝠(Myotissiligorensis)、菲菊头蝠(Rhinolo-phuspusillus)和黑髯墓蝠(Taphozousmelanopogon)的回声定位叫声特征和食性进行分析,并结合其形态特征与野外观察,推断其捕食生境和捕食策略。研究结果发现:黑髯墓蝠体型最大,声音特征属短调频型多谐波,一般为4个谐波,能量主要集中在第二谐波上,主频率为(32·84±1·17)kHz,选择鞘翅目和双翅目昆虫为主要食物;高颅鼠耳蝠(长调频型)和菲菊头蝠(长恒频-调频型),体型都较小,主频率分别是(84·44±8·13)kHz和(110·78±1·65)kHz,以双翅目昆虫为主要食物;而菲菊头蝠则以鞘翅目和双翅目昆虫为主要食物。上述结果证明,高颅鼠耳蝠、菲菊头蝠和黑髯墓蝠在声音和食物组成等方面出现了明显分化。     

Freshwater fishes of thailand as experimental intermediate hosts for Capillaria philippinensis

Bhaibulaya M., Indra-Ngarm S. and Ananthapruti M. 1979. Freshwater fishes of Thailand as experimental intermediate hosts for Capillaria philippinensis. The International Journal for Parasitology9: 105–108. Nine species of freshwater fishes from Thailand have been exposed to infection with embryonated eggs of Capillaria philippinensis. The eggs were fed to fishes with food or through a polyethylene tube. After 10–30 days larvae capable of establishing intestinal capillariasis in Mongolian gerbils were recovered from six fish species: Cyprinus carpio, Puntius gonionotus, Aplocheilus panchax, Gambusia holbrookii, Rasbora borapelensis, and Trichopsis vittatus. Larvae were not recovered from Tilapia nilotica, Osteochilus hasseltii and Trichogaster trichopterus. Five human cases of intestinal capillariasis have been reported from widely scattered areas of Thailand and the natural intermediate and definitive hosts remain to be determined.     

Morphological characterization of the alimentary tract of Antarctic fishes and its relation to feeding habits

Summary Morphological and morphometric characteristics of the alimentary tract in 22 species of carnivorous antarctic fishes were studied. It is shown that all of these species have similar, well-developed Y-shaped stomachs with generally thick (0.5–1.0 mm) walls. The relative stomach lengths are also similar, ranging from 9.8 to 22.2% of body length. Relative intestine lengths, a characteristic frequently used as an indicator of the kind of food eaten by a species, are also remarkably similar among most species (31 to 67%). Notothenia gibberifrons, a conspicuous benthos feeder, has a significantly longer intestine (91%), probably as an adaptation to the quantity of undigestible material (mud) incorporated with its faunal prey. These values fit within or below the limits (60–150$) of relative intestine length described in the literature for carnivorous fishes. The number of pyloric caecae is in general relatively low and fairly constant in each species. It is concluded that the morphological features studied could represent similar adaptations of these antarctic fishes to a similar carnivorous diet.     

广东发现二种局部白化蝙蝠

动物的白化主要是由于动物的黑色素细胞缺乏或者黑色素生成发生障碍所导致的一种体色异常现象。白化现象有完全白化和局部白化两种,部分白化指皮肤、毛发等的局部白化;完全白化是指由于完全缺少黑色素,皮肤和毛发白色,眼睛红色,可     

Relationships between height and girth of mangroves and soil-water conditions in the Mary and Hawkesbury River estuaries,eastern Australia

Abstract The height and diameter at breast height (DBH) of mangroves on the Hawkesbury River, New South Wales and the Mary River, Queensland were related to soil-water salinity, soil-water content and distance from the mouth of the estuary. On the Hawkesbury River, both Avicennia marina and Aegiceras corniculatum declined in height and DBH with increasing soil-water salinity and soil-water content, and increased in height with distance from the mouth of the estuary. Both species showed an extensive range of all variables. On the Mary River, where species diversity was higher, no relationship was found between the height and DBH of A. marina and A. corniculatum and soil-water salinity and soil-water content. Both species increased in height with increasing distance from the mouth of the estuary, a characteristic shared with all other species studied (Excoecaria agallocha, Ceriops tagal var. australis, Rhizophora stylosa). The results suggest that growth characteristics of mangroves are not a simple response to salinity gradients in diverse systems and that other variables such as nutrient availability may be important controls on mangrove growth.     

Partitioning of food resources among Sillago japonica, Ditremma temmincki, Tridentiger trigonocephalus, Hippocampus japonicus and Petroscirtes breviceps in an eelgrass, Zostera marina, bed

We carried out dietary analysis on five numerically abundant fishes, Sillago japonica, Ditremma temmincki, Tridentiger trigonocephalus, Hippocampus japonicus and Petroscirtes breviceps in an eelgrass bed in Kwangyang Bay, Korea. Comparisons between species demonstrated that the dietary composition of each fish species was significantly different from that of every other species. Although gammarid amphipods and caprellid amphipods were consumed by all species, their individual contributions to each species' diet varied. Furthermore, polychaetes contributed to the diets of S. japonica and T. trigonocephalusand crab larvae were consumed byD. temmincki. Algae and eelgrass were not consumed by four fish species and made only a minimal contribution to the diet of P. breviceps. The diet of each fish species except H. japonicus underwent size-related changes; smaller fishes consumed gammarid amphipods, mysids and copepods, while larger fishes ate polychaetes, gastropods, isopods and other fishes. Differences in the prey organisms consumed of each individual species could be often related to differences in mouth length and width. S. japonica, D. temmincki, T. trigonocephalus, and P. breviceps underwent also a significant diel changes that could be related to differences in foraging behavior and/or prey availability. Thus, use of vision to detect prey would account for the greater daytime consumption of copepods by S. japonica and of crab larvae by D. temmincki, whereas the nocturnal emergence of gammarid amphipods, polychaetes and isopods from the substrate explained their greater consumption by S. japonica, D. temmincki, T. trigonocephalusand P. breviceps at night. Dietary breadth was greater for species with larger mouth dimensions.     

A molecular phylogeny of the freshwater-fish genus Rasbora (Teleostei: Cyprinidae) in Sri Lanka reveals a remarkable diversification—And a cryptic species

The diversity of the freshwater-fish genus Rasbora (Cyprinidae) on Sri Lanka (five species) is high compared with the four species reported from the peninsula of India, from which the island's cyprinid fauna is derived. The paucity of characters by which species of Rasbora can be phenotypically distinguished renders field identification difficult, adversely affecting the estimation of populations and distributions, with consequences for conservation and management, increasing also the risk of taxonomic inflation. From a sampling of 90 sites across Sri Lanka and based on phylogenetic and haplotype analyses of sequences of cox1 and cytb mitochondrial, and rag1 and irbp nuclear markers, we review the species diversity and phylogeography of Rasbora on the island. Molecular analyses recover, in addition to the five species previously reported, a new (cryptic) species: Rasbora adisi sp. nov. Uncorrected pairwise cox1 genetic distances between species range from 2.0 to 12.3 percent. The Sri Lankan diversification derives from a common ancestor which arrived from India during a sea-level low-stand in the mid-Miocene (15.1 Ma [95% HPD: 11.5–19.8 Ma]), when the present-day island was subaerially connected to the Indian subcontinent by a broad isthmus. This gave rise to a clade comprising five species—R. adisi sp. nov.,Rasbora armitagei, Rasbora microcephalus, Rasbora naggsi and Rasbora wilpita—with a crown age of 9.9 Ma (95% HPD: 7.1–13.3 Ma) and to a clade comprising Indian and Sri Lankan populations of Rasbora dandia, which themselves are reciprocally monophyletic. Morphological analysis of 334 specimens discriminates between most species which, however, are most reliably diagnosed by chromatic characters. The four endemic species exhibit a pattern of inter-basin dispersal via headwater capture, followed by vicariance, explaining the high diversity of the genus on the island.     

Intraspecific variation in Gape–prey size Relationships and Feeding Success During Early Ontogeny in Red Drum, Sciaenops Ocellatus

The relationship between predator gape and prey consumption in laboratory-reared larva and field-caught early juvenile red drum, Sciaenops ocellatus, was investigated in light of the hypothesis that feeding success varies throughout the early life history intervals of marine fishes. We expected the feeding ability of red drum to be more strongly constrained by mouth gape in smaller fish and expected this ability to improve with gape size. To test this hypothesis, field-caught, early juvenile red drum were examined to determine the relationship between gape size and prey size consumed. In field-caught early juveniles, gape (height and width) and prey size consumed (length and width) increased linearly with standard length (SL); however, mean width of prey consumed was only 20–47% of gape width. Furthermore, when regressed on SL, gape width yielded a higher slope than prey width. To further test this hypothesis on less developed, pre-metamorphic fish, age-specific differences in gape, number of prey and size of prey consumed prior to metamorphosis were determined from laboratory-reared red drum larvae. Similar patterns were observed for gape height– and gape width–SL relationships in laboratory-reared red drum larvae. Size of consumed prey increased from three days from hatching (dfh) to 18dfh. The percentage of feeding larvae also increased from 3% at 3dfh to 97% at 18dfh. In both field-caught, early juvenile red drum and laboratory-reared larvae, there was little evidence that the size of prey consumed was constrained by mouth gape. It is hypothesized that besides gape size, the development of other features of the feeding mechanism (e.g., hyoid and opercular series) influences prey-capture performance prior to settlement in marine fishes.     

Threats to Fish and Fisheries of Kangsabati Reservoir,West Bengal,India

Fishes belonging to the Orders Beloniformes, Cypriniformes, Perciformes, Siluriformes and Synbranchiformes are usually found in the Kangsabati reservoir of West Bengal, India. In recent years among the trapped fishes fishermen failed to get certain fish species which were available to them in the last decade. This prompted us to conduct a survey of ichthyofauna of the said reservoir in respect to the water parameters, keeping in view the anthropogenic activity-induced pollution scenario. It is revealed that the fishes belonging to the species Xenentodon cancila, Nemacheilus savona, Sillaginopsis panijus, Pangasius sutchi, Colisa sota, Mystus cavasius, Mystus seenghala and Mastacembelus armatus are completely absent in the survey area. It is most likely that the eutrophication-induced causes especially, variations in composition and density of plankton as well as the undesirable changes in physical and chemical properties of the water have forced these fishes to migrate elsewhere.