Significant Interspecific Differences Research Articles

Climate of origin shapes variations in wood anatomical properties of 17 Picea species.

Variations in hydraulic conductivity may arise from species-specific differences in the anatomical structure and function of the xylem, reflecting a spectrum of plant strategies along a slow-fast resource economy continuum. Spruce (Picea spp.), a widely distributed and highly adaptable tree species, is crucial in preventing soil erosion and enabling climate regulation. However, a comprehensive understanding of the variability in anatomical traits of stems and their underlying drivers in the Picea genus is currently lacking especially in a common garden. We assessed 19 stem economic properties and hydraulic characteristics of 17 Picea species grown in a common garden in Tianshui, Gansu Province, China. Significant interspecific differences in growth and anatomical characteristics were observed among the species. Specifically, xylem hydraulic conductivity (Ks) and hydraulic diameter exhibited a significant negative correlation with the thickness to span ratio (TSR), cell wall ratio, and tracheid density and a significant positive correlation with fiber length, and size of the radial tracheid. PCA revealed that the first two axes accounted for 64.40% of the variance, with PC1 reflecting the trade-off between hydraulic efficiency and mechanical support and PC2 representing the trade-off between high embolism resistance and strong pit flexibility. Regression analysis and structural equation modelling further confirmed that tracheid size positively influenced Ks, whereas the traits DWT, D_r, and TSR have influenced Ks indirectly. All traits failed to show significant phylogenetic associations. Pearson's correlation analysis demonstrated strong correlations between most traits and longitude, with the notable influence of the mean temperature during the driest quarter, annual precipitation, precipitation during the wettest quarter, and aridity index. Our results showed that xylem anatomical traits demonstrated considerable variability across phylogenies, consistent with the pattern of parallel sympatric radiation evolution and global diversity in spruce. By integrating the anatomical structure of the stem xylem as well as environmental factors of origin and evolutionary relationships, our findings provide novel insights into the ecological adaptations of the Picea genus.

Elliptic Fourier analysis of leaf shape of Callicarpa pedunculata and Callicarpa rubella (Lamiaceae)

Leaves play an important role in species discrimination. An elliptic Fourier analysis (EFA) based morphometric technique was used to assess divergence between the poorly differentiated species, Callicarpa pedunculata and C. rubella. Using leaf specimen images from herbarium collections, principal components (PCs) were extracted from the Fourier coefficients and used to describe leaf outline and leaf shape descriptors: circularity, aspect ratio, and solidity. The results indicate that symmetric (54%) and asymmetric (35%) components of the leaves of C. pedunculata and C. rubella are sources of shape variation, as shown in the width and leaf tips among the samples. MANOVA revealed significant interspecific differences (P = 0.03) between C. pedunculata and C. rubella. The jack-knife cross-validation showed 71% of correctly classified species both in C. pedunculata and C. rubella. Furthermore, the results of this study were able to reveal significant leaf shape descriptors like aspect ratio, circularity, and solidity as important diagnostic characters in discriminating C. pedunculata and C. rubella. Thus, in conclusion, leaf serrations, leaf size, and leaf lobes are important characteristics in discriminating between C. pedunculata and C. rubella.

Halogenated aromatic pollutants in routine animal-derived food of south China: Occurrence, sources, and dietary intake risks

Halogenated aromatic pollutants (HAPs) including polychlorinated dibenzo-p-dioxins/furans (PCDD/Fs), polychlorinated biphenyls (PCBs), polybrominated dibenzo-p-dioxins/furans (PBDD/Fs), and polybrominated diphenyl ethers (PBDEs) exhibit diverse toxicities and bio-accumulation in animals, thereby imposing risks on human via animal-derived food (ADF) consumption. Here we examined these HAPs in routine ADFs from South China and observed that PBDEs and PCBs showed statistically higher concentrations than PCDD/Fs and PBDD/Fs. PCDD/Fs and PCBs in these ADFs were mainly from the polluted feed and habitat of animals, except PCDD/Fs in egg, which additionally underwent selective biotransformation/progeny transfer after the maternal intake of PCDD/F-polluted stuff. PBDEs and PBDD/Fs were mostly derived from the extensive use of deca-BDE and their polluted environments. Significant interspecific differences were mainly observed for DL-PCBs and partly for PBDD/Fs and PBDEs, which might be caused by their distinct transferability/biodegradability in animals and the different living habit and habitat of animals. The dietary intake doses (DIDs) of these HAPs via ADF consumption were all highest for toddlers, then teenagers and adults. Milk, egg, and fish contributed most to the DIDs and risks for toddlers and teenagers, which results of several cities exceeded the recommended thresholds and illustrated noteworthy risks. Pork, fish, and egg were the top three risk contributors for adults, which carcinogenic and non-carcinogenic risks were both acceptable. Notably, PBDD/Fs showed the lowest concentrations but highest contributions to the total risks of these HAPs, thereby meriting continuous attention.

Dental shape evolution of the giant panda (Ailuropoda, Ursidae) during the Quaternary

ABSTRACT The giant panda is well known to have unique dentition, adapted to bamboo exclusive diet. The teeth are used to cut and grind the bamboo. However, it is unclear how these teeth evolved through geographical time. Here, we present the first geometric morphometric analysis of all cheek teeth of the giant panda, based on the large fossil collection of the giant panda teeth found from the Pleistocene deposits of southern China. Our analyses reveal the substantial intraspecific variation of the giant panda teeth, but no significant interspecific differences in Ailuropoda, supporting the basic function of the giant panda teeth has already formed since the Early Pleistocene. Among the cheek teeth, the premolars show the highest interspecific variation, suggesting a continuous increase in the feeding efficiency of the bamboo diet, which may facilitate the giant panda to grow a larger body size from Early Pleistocene species to A. melanoleuca. The Late Pleistocene A. m. baconi and two modern two subspecies show largely overlapped morphospace for all teeth, and the variation ranges are also similar, suggesting a fully established feeding apparatus and implying a similar diet. Our analyses provide new information on the giant panda evolution and adaptation.

A case study on microplastics pollution characteristics in fouling organisms in typical aquaculture bay, China

Microplastics (MPs) and fouling organisms are prevalent in oceans worldwide. The study aims to investigate the pollution characteristics of MPs in fouling organisms. The study found significant inter-specific differences in the MPs abundance, while the length of MPs is consistent. The average number of MPs in N. exigua is 0.00 ± 0.00. There is a correlation between MPs abundance and weight in sessile group, while gastropods don't. Direct observation has demonstrated that the radulae of N. radula can envelop MPs. Fiber and blue are the predominant forms and colors of MPs found in fouling organisms. It is noteworthy that all film and fragment MPs observed were of a blue hue and had a size limitation of 500 μm. The characteristics of MPs between sessile organisms are more similar than those between gastropods. This study has improved our understanding of the pollution characteristics of MPs in fouling organisms, specifically gastropods.

Functional Activity of the Blood System in Two Migratory Bat Species of the Urals.

Functional activity of the blood system was studied in two migratory Ural species, Vespertilio murinus Linnaeus, 1758 and Pipistrellus nathusii Keyserling et Blasius, 1839. A multivariate nonparametric ANOVA of red blood parameters showed significant interspecific differences (p < 0.05) between the migrating bats and the resident species pond bat. A certain genetically determined multidirectionality in the mobilization of emergency regulation mechanisms of the lymphoid blood system was observed in bats.

How wet are water plants? Determination of macrophyte leaf water repellency

Leaf water repellency (LWR) is a very important plant trait that influences plant performance in many different ways in different habitats. Being always in contact with water, the conditions for aquatic plants (macrophytes) are very different than for terrestrial plants and many of the advantages of high water repellency are less relevant for submerged macrophyte leaves. This paper is the first to determine the LWR of submerged leaves of 6 common macrophyte species by measurements of a contact angle between a water droplet and the leaf surface. Contact angles varied between 30° and 80°, classifying all species as hydrophilic. Yet significant interspecific differences were found. Differences between the ab- and adaxial leaf sides were small. The presence of a biofilm changed contact angles across species by about 20° in a positive or negative direction, depending on periphyton mass. Potential ecological effects of variation in LWR are discussed for macrophytes and manipulation of the biofilm by the plants to optimize LWR is hypothesized.

Cletocamptus cubaensis n. sp. (Harpacticoida, Canthocamptidae) from Cuba with taxonomic notes on the species

Abstract A new species of harpacticoid copepod, Cletocamptus cubaensis n. sp., from a marine aquarium in Cuba, previously identified with the highly polymorphic Cletocamptus deitersi (Richard, 1897), is described herein. A revision of the Cuban material showed that, despite the morphological similarity to Cletocamptus deitersi, there are significant interspecific differences in several microcharacters that were not taken into account in the previous species determination, such as integumental sensilla and pores, and ornamentation of segments, mouthparts, swimming legs, prosome, and urosome. Additionally, some other differences were observed in the relative length and shape of the apophysis of the endopod of P3 in males, the armature complement of the second segment of endopod P2 in males (with four setae instead of three), the ornamentation and length of the caudal rami in both sexes, and the ornamentation of the anal operculum (with 8 spinules). Similarity to other species is discussed, along with brief comments on the morphological similarities and differences between the new species from Cuba and Cletocamptus nudus Gómez, 2005 recorded from Brazil and Colombia, C. schmidti Mielke, 2000 known from the Galapagos archipelago, and C. samariensis Fuentes-Reinés, Zoppi de Roa &amp; Torres, 2015 from Colombia.

Domestication over Speciation in Allopolyploid Cotton Species: A Stronger Transcriptomic Pull.

Cotton has been domesticated independently four times for its fiber, but the genomic targets of selection during each domestication event are mostly unknown. Comparative analysis of the transcriptome during cotton fiber development in wild and cultivated materials holds promise for revealing how independent domestications led to the superficially similar modern cotton fiber phenotype in upland (G. hirsutum) and Pima (G. barbadense) cotton cultivars. Here we examined the fiber transcriptomes of both wild and domesticated G. hirsutum and G. barbadense to compare the effects of speciation versus domestication, performing differential gene expression analysis and coexpression network analysis at four developmental timepoints (5, 10, 15, or 20 days after flowering) spanning primary and secondary wall synthesis. These analyses revealed extensive differential expression between species, timepoints, domestication states, and particularly the intersection of domestication and species. Differential expression was higher when comparing domesticated accessions of the two species than between the wild, indicating that domestication had a greater impact on the transcriptome than speciation. Network analysis showed significant interspecific differences in coexpression network topology, module membership, and connectivity. Despite these differences, some modules or module functions were subject to parallel domestication in both species. Taken together, these results indicate that independent domestication led G. hirsutum and G. barbadense down unique pathways but that it also leveraged similar modules of coexpression to arrive at similar domesticated phenotypes.

Factors limiting the spread of middle- and low-altitude fishes to the Qinghai-Tibet plateau

The distribution pattern of species is determined by the environment and their adaptability to the environment. Qinghai-Tibet Plateau has become a natural laboratory for studying adaptive evolution due to its extreme environmental characteristics such as low temperature, low oxygen, high salinity and high ultraviolet radiation (UVR). Fish are sensitive to the environmental stress, so they are ideal materials for studying high-altitude adaptation of animals. Previous studies have mainly focused on the adaptability of plateau species, but the reasons why plain species cannot spread to the plateau have been ignored. In this study, stress experiments and histological experiments were used to compare the tolerance of six Barbini fishes (family: Cyprinidae) distributed at different altitudes and regions to low temperature, low oxygen, salinity and UVR. Results showed that the tolerance of fishes to high-altitude environmental stress factors was closely related to the environmental stress of their main habitats. The high-altitude fish Gymnocypris eckloni had strong tolerance to all stress factors, while the other five fishes from middle and low altitudes could not adapt to single or multiple stress factors, with significant interspecific differences. Among these factors, middle- and low-altitude fishes showed common low tolerance to UVR, suggesting that high UVR, the factor lacking at low altitude areas, plays an important role. Moreover, during the uplift of the Qinghai-Tibet Plateau, Schizothorax fish disappeared from the middle of the plateau. We speculate that this was caused by its intolerance to the increasingly extreme plateau environment, especially salinity.

Combined use of biomarkers to assess the impact of untreated wastewater from the Danube River, Serbia.

In this study a battery of bioassays, both in vivo (metals and metalloids concentrations, erythrocyte morphometry, comet assay, micronucleus assay, and histopathological analyses) on vimba bream Vimba vimba (L., 1758) and white bream Blicca bjoerkna (L., 1758), and in vitro (treatment of HepG2 cells with native water samples) was applied to assess the harmful potential of untreated wastewater. Faecal indicator bacteria were quantified to assess the microbiological water quality. Vimba bream had significantly higher Fe concentrations in both liver and muscle, while white bream had higher Ca and Cu concentrations in liver. Vimba bream had a significantly higher level of DNA damage in both liver and blood cells, in comparison to white bream. Low levels of micronucleus and nuclear abnormalities were observed in both species. Erythrocytes morphometry did not show significant interspecific differences. Histopathological analyses revealed a similar response of the studied species, with a significantly higher presence of ceroid pigments in the liver of vimba bream. Treatment of HepG2 cells revealed the high genotoxic potential of water downstream of the discharge point. The results of this study clearly demonstrate the importance of effect-based monitoring, in order to enforce more efficient management of natural resources and implementation of wastewater treatment systems.

Settling and transport properties of grass carp and silver carp eggs in the water-hardened phase: Implications for resource protection and invasion control during early life period

Grass carp and silver carp eggs have no swimming ability in the water-hardened phase and need to drift for tens or even hundreds of hours before complete incubation. A full comprehensive understanding of the settling and transport properties of eggs is crucial for the resource protection and invasion control of Four Major Chinese Carps (FMCCs) during their early life stages. Artificial eggs have been used extensively in previous field and flume experiments; however, our understanding of the settling and transport properties of real eggs in the water-hardened phase remains limited. In the present study, a series of column and flume experiments were conducted in stagnant and moving water, respectively. In light of the differences in settling characteristics, caution should be exercised when applying research results obtained from artificial eggs having the closest diameter and specific gravity as real eggs. Compared with grass carp and silver carp eggs in the water-hardening phase, egg diameters in the water-hardened phase were 36% and 33% greater, respectively, and egg hydrostatic settling velocities were 31% and 40% lower, respectively. Significant interspecific differences between the two species exist in terms of egg size and hydrostatic settling velocity. Based on linear mixed effects analysis of dominant transport trajectories and regression analysis between suspending rate and flow velocity, 0.30 m/s can be considered as critical drifting velocity in uniform flow. Adaptive management schemes are discussed to promote resource protection and invasion control of FMCCs during the early life stages. The results of the present study enhance our understanding of drifting egg movement and provide insights that could facilitate the comprehensive management of FMCCs.

Effect of hyposaline stress on the release of dissolved organic carbon from five common macroalgal species

Macroalgae are important primary producers in coastal waters; they have high carbon sink potential and are often subjected to hyposaline stress in their natural habitats. The effect of hyposaline stress on dissolved organic carbon (DOC) release from macroalgae remains to be studied in depth. In this study, five common intertidal macroalgae in coastal waters of Fujian Province, China—Pyropia haitaneisis, Gracilaria lemaneiformis, Sargassum thunbergii, Enteromorpha prolifera, and Ulva lactuca—were used as research materials to investigate the effects of 6-h hyposaline treatments (5 PSU, 0 PSU) on the growth, DOC release rate, photosynthesis, respiration, and contents of carbon (C), nitrogen (N), and phosphorus (P). Our results showed that, although there were significant interspecific differences in the tolerance of the five species of macroalgae to low salinity, the DOC release rate of macroalgae increased overall with decreasing salinity, while the photosynthetic rate showed the opposite trend. Hyposaline treatments reduced the net photosynthetic rate of macroalgae, as the net photosynthetic rate of all five species decreased by more than 50% and 75% under the 5 PSU and 0 PSU treatments, respectively. The tissue C contents of P. haitaneisis, G. lemaneiformis, and E. prolifera increased significantly with decreasing salinity, by 6.90%, 40.15%, and 43.80% at 0 PSU, respectively. However, the tissue C contents of S. thunbergii and U. lactuca were not influenced or were slightly decreased by low salinity. These results suggest that short-term hyposaline treatment has a dual effect on organic carbon accumulation of macroalgae by inhibiting photosynthetic carbon fixation and increasing DOC release, and this in turn may have a large impact on the carbon cycle in macroalgae enrichment areas.

Two new species of Bryocamptus (Copepoda, Harpacticoida, Canthocamptidae) from the Russian Arctic and comparison with Bryocamptusminutus (Claus, 1863).

Two new species of Bryocamptus Chappuis, 1929 from the Russian Arctic from the Bryocamptusminutus species group are described: Bryocamptusputoranus sp. nov. and Bryocamptusabramovae sp. nov. A complete morphological comparison of the new species with the type species Bryocamptusminutus (Claus, 1863) was carried out. Significant interspecific differences were shown at the level of microcharacters, such as integumental sensillae and pores, ornamentation of segments of mouthparts and swimming legs, and pores on swimming legs. A significant correlation has also been shown in the shape of the caudal rami of the females and the antennules of the males, which is likely caused by an evolutionary sexual arms race. Bryocamptusputoranus sp. nov. and B.minutus have a similar structure of caudal rami, but completely different male antennules, which may indicate a convergent origin of modifications and highlights the importance of depicting male antennules in the species descriptions.

Inter and intraspecific variability of dieldrin accumulation in Cucurbita fruits: New perspectives for food safety and phytomanagement of contaminated soils

Due to past agricultural practices, it is common to identify arable soils contaminated with persistent and potentially toxic organochlorine pesticides (OCPs). Occurrence of OCPs, including dieldrin, in vegetables can lead to chronic exposure of the consumers. Some market vegetables, particularly the Cucurbitaceae, are known to accumulate high OCP concentrations. Dieldrin concentration in Cucurbita fruits can exceed the Maximal Residue Limit (MRL) resulting in cultivation and sale restrictions for market gardeners. To assess the intra- and interspecific variability of Cucurbitaceae species for low dieldrin concentration in fruits could be a solution.Here, 24 varieties from seven Cucurbitaceae species were cultivated outdoors in large pots, until fruiting, in soils historically contaminated with dieldrin. More than 330 fruits were harvested and analyzed for determining the inter and intraspecific variability of dieldrin accumulation. Significant interspecific differences occurred with mean fruit concentration ranging between 4.2 ± 7.0 and 85.0 ± 19.4 μg dieldrin kg−1 fresh weigh (FW) in watermelons (C. lanatus L.) and cucumbers (C. sativus L.), respectively. Intraspecific differences only occurred for Cucurbita pepo L. with mean concentration ranging between 4.9 ± 1.1 and 70.3 ± 3.6 μg dieldrin kg−1 FW for the varieties Noire maraîchère and Orélia, respectively. For this plant species, the influence of soil concentration, plant exposure time and biomass on fruit dieldrin concentration depended mainly on varieties.

Interspecific differences and ecological correlations of ultraviolet radiation tolerance in low- and high-altitude fishes

Ultraviolet radiation (UVR) is a ubiquitous environmental factor and with complex and diverse effects on organisms, and the UVR tolerance of species varies due to selection, adaptation and evolution. This study aimed to improve our understanding of the interspecific differences in UVR tolerance of fishes. First, we compared skin histology between high-altitude fishes and their low-altitude relatives. Second, we assessed the skin histological changes of 22 fish species after UVR exposure and quantified their damage levels. Finally, the factors affecting the difference in UVR tolerance among fishes were studied. Thin or absent scales was a common characteristic of high-altitude fishes in different taxonomic groups, but other skin structure parameters (the thickness of the dermis and epidermis, the size and number of mucous and club cells) did not show convergence. After UVR exposure, the size and number of mucous cells and club cells in the experimental fishes were generally reduced, but the changes in epidermal and dermal thickness varied among species. The change rata of melanin area was strong negatively correlated with the level of damage, indicating that increased melanin was helpful to reduce UVR damage. On the whole, the skin histological changes of high-altitude fishes after UVR exposure did not differ from those of low-altitude fishes. However, the epidermis and dermis of Gymnocypris eckloni and Oncorhynchus mykiss, which had the highest UVR tolerance, were nonpathologically thickened, indicating that they may contribute to UVR tolerance. There were significant interspecific differences in UVR tolerance among the experimental fishes, with high-altitude and cold water fishes showing stronger UVR tolerance. Interestingly, some low-altitude cold water fish (e.g., O. mykiss) also showed high UVR tolerance, suggesting that besides high-altitude adaptation, low-temperature adaptation also may play an important role in organismal adaptation to UVR.

Hydrological Drivers for the Spatial Distribution of Wetland Herbaceous Communities in Poyang Lake

Hydrological processes are known as major driving forces in structuring wetland plant communities, but the specific relationships are not always well understood. The recent dry conditions of Poyang Lake (i.e., the largest freshwater lake in China) are having a profound impact on its wetland vegetation, leading to the degradation of the entire wetland ecosystem. We developed an integrated framework to quantitatively investigate the relationship between the spatial distribution of major wetland herbaceous communities and the hydrological regimes of Poyang Lake. First, the wetland herbaceous community classification was built using a support-vector machine and simultaneous parameter optimization, achieving an overall accuracy of over 98%. Secondly, based on the inundation conditions since 2000, four hydrological drivers of the spatial distribution of these communities were evaluated by canonical correspondence analysis. Finally, the hydrological niches of the communities were quantified by Gaussian regression and quantile methods. The results show that there were significant interspecific differences in terms of the hydrological niche. For example, Carex cinerascens Ass was the most adaptable to inundation, while Triarrhena lutarioriparia + Phragmites australis Ass was the least. Our integrated analytical framework can contribute to hydrological management to better maintain the wetland plant community structure in the Poyang Lake area.

Quantitative three-dimensional morphological analysis supports species discrimination in complex-shaped and taxonomically challenging corals

Morphological characters play an important role in species descriptions and are essential for a better understanding of the function, evolution and plasticity of an organism’s shape. However, in complex-shaped organisms lacking characteristic features that can be used as landmarks, quantifying morphological traits, assessing their intra- and interspecific variation, and subsequently delineating phenotypically distinct groups continue to be problematic. For such organisms, three-dimensional morphological analysis might be a promising approach to differentiate morphogroups and potentially aid the delineation of species boundaries, though identifying informative features remains a challenge. Here, we assessed the potential of 3D-based quantitative morphology to delineatea prioriand/or to discriminatea posteriorimorphogroups of complex-shaped and taxonomically challenging organisms, such as corals from the morphologically diverse genusAcropora. Using three closely related coral taxa previously delimited using other lines of evidence, we extracted a set of variables derived from triangulated polygon meshes and medial axis skeletons of the 3D models. From the resulting data set, univariate and multivariate analyses of 3D-based variables quantifying overall shape including curvature, branching, and complexity were conducted. Finally, informative feature selection was performed to assess the discriminative power of the selected variables. Results revealed significant interspecific differences in the means of a set of 3D-based variables, highlighting potentially informative characters that provide sufficient resolution to discriminate morphogroups congruent with independent species identification based on other lines of evidence. A combination of representative features, remarkably represented by curvature, yielded measures that assisted in differentiating closely related species despite the overall morphospaces overlap. This study shows that a well-justified combination of 3D-based variables can aid species discrimination in complex-shaped organisms such as corals and that feature screening and selection is useful for achieving sufficient resolution to validate species boundaries. Yet, the significant discriminative power displayed by curvature-related variables and their potential link to functional significance need to be explored further. Integrating informative morphological features with other independent lines of evidence appears therefore a promising way to advance not only taxonomy but also our understanding of morphological variation in complex-shaped organisms.

Differences in wings may be sufficient to separate the sexes and two species of Gynaikothrips Zimmermann (Thysanoptera: Phlaeothripidae)?

In this study, we use geometric morphometry to discriminate thrips of the species Gynaikothrips uzeli (Zimmerman) and Gynaikothrips ficorum (Marchal) and also to detect sexual dimorphism in these species. Two hundred individuals, one hundred females and one hundred males, from G. uzeli and G. ficorum, were used to verify sexual dimorphism. For interspecific differentiation, two hundred females were used, one hundred individuals of each species. It was possible to observe differences in the shape of the wing between sexes in both species. In G. uzeli, the first two main components explain 92.5% of the total variation of individuals. The first main component explains 87% and the second 5.5 of the total variation of individuals. For G. ficorum, the first two main components explain 78.2% of the total variation of individuals. The first principal component contributed with 62% and the second principal component with 16.2% of the variation of the shape of the wing. Besides, significant interspecific differences were observed in the shape of the wing, where the first two main components were sufficient to explain 86% of the total variation of the individuals. The first principal component explained 76.2% and the second 9.8% of the total variation of the individuals, being possible to verify differences in the shape of the wing of these two species. Geometric morphometry is a viable technique for assessing sexual dimorphism, as well as interspecific differences in the shape of the wings of these species, which are morphologically very similar.

Activity of peptidases and glycosidases of the digestive tract in some species of bony fish of Vietnam

For the first time, the activity and pH dependence of digestive enzymes were studied in fish inhabiting the Mekong Delta: duskyfin glassy perchlet Parambassis wolffii, smallscale croaker Boesemania microlepis, catfish Pangasius macronema, and representatives of the family Cyprinidae. Significant interspecific differences were revealed in the level of peptidase and glycosidase activity providing hydrolysis of protein and carbohydrate food components. The greatest interspecific differences are characteristic of glycosidases: the level of enzymatic activity in Cyprinidae fish exceeds that in P. wolffii by 13.6 times. The differences in the level of peptidase activity in fish of different species are lower: in the case of the activity of stomach enzymes in P. wolffii, the values are 1.8 times higher than those in P. macronema, and in the case of total activity of stomach and intestinal enzymes in the same species, the values are 1.5 times higher. The data obtained confirm the concept that the digestive hydrolase activity depends on the fish feeding spectrum. The activity of intestinal enzymes decreases more significantly in the acidic pH zone than in the basic one. Consequently, acidification of the intestinal environment will negatively affect the digestive processes in these fish species.