Limnology and Freshwater Biology

New report of Craspedacusta sowerbii (Lankester, 1880) medusae in Belgium

Pajak J., Pajak B. — Thu, 19 Feb 2026 00:00:00 +0800

The jellyfish Craspedacusta sowerbii (Lankester, 1880) is known to be an invasive species in freshwater worldwide, except in Antarctica. In Belgium, C. sowerbii was first recorded in 1939 by Damas in the River Meuse. Since then, few further Belgian observations of this species have been made. Here, we report the presence and determine the gender of C. sowerbii medusae in an artificial pond in Forrières, in southern Belgium. This is the first record of this species in the province of Luxembourg. Our findings suggest that the population consists exclusively of females.

Assessing the effects of dietary and waterborne commercial salt on the performance and welfare of common carp

Shamal R.H., Nasreen M.A., Hevar A.H., Hawraz F.M., Kazhy J.S. — Thu, 19 Feb 2026 00:00:00 +0800

This study investigated the effects of salt additives in water and diet on the physiological and health parameters of common carp (Cyprinus carpio L.). Fingerlings (~50 g) were divided into seven groups: a control group (G1), three water treatment groups (G2_A–_C; 4, 8, and 12 g L⁻¹ salt), and three diet treatment groups (G3_A–_C; 5, 10, and 15 g kg⁻¹ dietary salt). All fish were fed a standard diet containing 28% crude protein at 3% body weight per day. Results revealed that G1 had the highest values for lymphocyte and monocyte counts, mean corpuscular hemoglobin (MCH), mean corpuscular volume (MCV), cholesterol, triglycerides, low-density lipoprotein cholesterol (LDL), albumin, total protein, and several somatic indices. G2_B exhibited significantly higher potassium and sodium levels, while G3_A showed elevated white blood cell (WBC), granulocytes, liver enzyme activities (Alanine aminotransferase activity (ALT), aspartate aminotransferase activity (AST)), creatinine, glucose, chloride, and various somatic indices. G2_A and G2_Bgroups had increased red blood cells (RBC), hemoglobin, hematocrit, and body weight index. The findings indicate that using 12 g L⁻¹ salt in rearing water and 15 g kg⁻¹ salt in the diet can enhance growth and health performance in Cyprinus carpio. This study provides important insights into salt-induced physiological responses in carp and offers practical recommendations for aquaculture practices.

Influence of sex and body size on selected morphometric traits of Metopograpsus frontalis (Miers, 1880) from Southern Vietnam

Thu, 19 Feb 2026 00:00:00 +0800

A total of 167 specimens of Metopograpsus frontalis (105 males and 62 females) were collected monthly from intertidal mudflats in Ganh Hao, Ca Mau Province, Southern Vietnam, from July to October 2025. Selected morphometric traits, including carapace width from left to right (CW_L–R), carapace width from right to left (CW_R–L), manus width (MW2, MW3), pollex width (PW5), and dactyl width (DW7), were measured with a 0.01-mm vernier caliper. Generalized linear models were fitted to evaluate the effects of sex and body size, using Gaussian models for CW and Gamma models with a log link for MW, PW, and DW. We found no significant sex-related differences in CW_L–Rand CW_R–L (p > 0.05), whereas MW2, MW3, PW5, and DW7 were significantly larger in males (p<0.001). Sex coefficients (β=0.156–0.257) corresponded to rate ratios (RR) of 1.17–1.29, indicating that male claws were 17–29% larger after adjusting for CW_L–R and CW_R–L. Both CW variables had strong positive effects (β=0.054–0.070; RR=1.06–1.07; and p<0.001). All Gamma models showed χ²/df<1, confirming good model fit without overdispersion. These results provide quantitative evidence of sex-related variation in morphometric traits of M. frontalis and establish a morphometric baseline for future ecological and evolutionary studies of mangrove crabs in the Mekong Delta.

Nanozinc as an emerging nanopollutant: sublethal effects on the invasive freshwater bivalve Limnoperna fortunei (Dunker, 1857)

Ale A., Rojas Molina F.M., Montalto L., Andrade V.S. — Thu, 19 Feb 2026 00:00:00 +0800

Zinc oxide nanoparticles (ZnONP) are among the most widely produced nanomaterials worldwide given their unique properties, despite their nanotoxicity has been poorly addressed. In parallel, environmental concern has risen because of increasing amounts of them reaching the environmental matrices, whereas the aquatic ones are one of the main final sinks. As key non-target species, we aimed to expose the invasive freshwater bivalve Limnoperna fortunei to sublethal concentrations of ZnONP (0, 0.025, 0.25, and 2.5 mg/L) to evaluate tissue damage and oxidative stress-related markers in the soft tissue. After a 96 h-exposure, the alkaline phosphatase enzyme activity increased after 0.025 mg/L, and the alanine aminotransferase activity decreased at 2.5 mg/L. Aspartate aminotransferase enzyme activity also decreased at 0.25 and 2.5 mg/L. In terms of oxidative stress, only superoxide dismutase activity increased after exposure to the lowest nanozinc concentration. We concluded that nanozinc may pose a threat to the aquatic biota in a context that lacks proper regulation and control for nanopollutants, and that the toxicity mechanisms in this species are mainly related to tissue damage, even at environmentally relevant concentrations, as the lowest one tested.

Morphometric analysis of selected claw traits in Tubuca forcipata (Ocypodidae) from Southern Vietnam

Dai V.C., Duong L.C., Huynh H.N.G., Vo V.T.K., Nguyen Q.L., Vo L.T.T., Dinh Q.M. — Thu, 19 Feb 2026 00:00:00 +0800

A total of 233 specimens of the fiddler crab Tubuca forcipata (189 males and 44 females) were collected monthly from intertidal mudflats in Dam Doi and Hoa Binh, Ca Mau Province, Southern Vietnam, from July to October 2025. Selected morphometric traits, comprising the carapace width left-to-right (CW_L–R), the carapace width right-to-left (CW_R–L), the manus widths (MW2 and MW3), the pollex width (PW5), and the dactyl width (DW7), were measured to 0.01 mm. Generalized linear models with a gamma distribution and log link were used for trait comparisons; cheliped traits were analyzed with sex and the carapace width (CW_L–R or CW_R–L) as predictors. The carapace width did not differ by sex (p > 0.05), whereas MW2, MW3, PW5, and DW7 were significantly larger in males after adjusting for the carapace width (β_sex = 0.156–0.257; rate ratios (RR) = 1.17–1.29; p < 0.001). The carapace width had strong positive effects on all cheliped traits (β_CW = 0.054–0.070; RR ≈ 1.06–1.07; p < 0.001). Model diagnostics showed χ²/df < 1, indicating no overdispersion. These results demonstrate pronounced sex-linked functional dimorphism in the chelae of T. forcipata despite similar overall body size, providing a quantitative morphometric baseline for ecological and evolutionary studies of mangrove crabs in the Mekong Delta.

Variability of Coregonus peled (Gmelin, 1789) fecundity in the middle part of the Ob River (Western Siberia, Russia) and the influence of environmental temperature on it

Mishakin A.V., Khakimov R.M., Zavgorodniaia О.А., Interesova E.A. — Thu, 19 Feb 2026 00:00:00 +0800

The peled, Coregonus peled, is a widespread species of the Coregonidae in Northern Eurasia. Its numbers remain relatively high throughout the Ob River basin. This species is environmentally plastic. Its fecundity varies widely, both across different water bodies and within the same water body during different observation periods. Hydrological conditions influence the reproductive capacity of peled, with higher fecundity in high-water years. This study aimed to analyze the fecundity of peled migrating upstream to the middle part of the Ob River for natural reproduction and detection the relationship between its fluctuations and environmental temperature. We identified that peled, which comes to spawn in the middle part of the Ob River, reaches sexual maturity at the age of three years. However, individuals aged five to six years form the basis of the spawning stock, comprising up to 70% of the total. The reproductive capacity of peled is highly variable. Individual absolute fecundity ranges from 11.3 to 58.0 thousand eggs, increasing with age, standard length, total weight, body weight, and Fulton and Clark indexes. Individual absolute fecundity ranges from 36 to 103 eggs per gram of body weight and correlates with total weight and Fulton indexes. Peled reproductive capacity indicators vary significantly between years. Overall, the individual relative fecundity of this species in age groups of 5+ years and older has decreased by 41–47% compared to the mid-20th century. There was a relationship between the reproductive capacity of peled migrating to the middle part of the Ob River for spawning and the environmental temperature in the lower part of the Ob River, where fish were feeding before the spawning migration begins: relatively high July temperatures are associated with lower individual absolute fecundity indicators for the most numerous age groups. Thus, global warming may have a negative impact on the reproductive capacity of peled in the Ob River basin.

Trophic structure and functional feeding groups of macroinvertebrates in a section of the Gallinazo tropical stream

Saldaña-Escorcia R., Castañeda-Sanguino C.E., Salas-Ospino V.A. — Thu, 19 Feb 2026 00:00:00 +0800

Aquatic macroinvertebrates play crucial roles in ecosystem processes such as grazing, decomposition, and mineralization. Classifying these organisms into functional feeding groups (FFGs) enables a more comprehensive understanding of energy and matter flow through trait-based approaches, complementing traditional taxonomic methods. The study analyzed the trophic structure and FFG variation of aquatic macroinvertebrates in a section of a tropical stream, located in the municipality of Aguachica, Colombia. Sampling was carried out during the rainy season in May and the dry season in July 2024, during which the composition and abundance of macroinvertebrate feeding groups were analyzed. Physical and chemical parameters were measured both in situ and ex situ at strategically selected stations based on accessibility and location. Macroinvertebrates were collected using Surber and D-type nets and identified to the family level. They were then assigned to functional feeding groups. Ecological indices and multivariate statistical analyses were applied to evaluate ecosystem attributes. Results revealed seasonal variations in water parameters, including lower dissolved oxygen and higher chemical oxygen demand during the dry season, suggesting potential organic pollution. Macroinvertebrate richness was higher during the dry season, with Caenis sp. and Tanypodinae sp. being dominant, while Drepanotrema sp. and Physa sp. were more abundant during the rainy season, reflecting eutrophic conditions. The P/R index indicated heterotrophic dominance, and low CPOM/FPOM ratios pointed to limited riparian cover. These findings underscore the importance of implementing conservation strategies to mitigate anthropogenic pressures and preserve the ecological integrity of freshwater ecosystems.

Bioactivities of freshwater sponges and their associated bacteria: a review

Adkar U.S., Chhabda P.J., Harkal A.D., Rao P.R., Devdhe G.R. — Thu, 19 Feb 2026 00:00:00 +0800

This review aims to provide an overview of the biological activities of freshwater sponges and their microbes associated with them. Freshwater sponges, despite their ecological significance and potential as reservoirs of bioactive compounds, remain underexplored compared to their marine counterparts. This review highlights the bioactivities of eight freshwater sponge extracts, among them being Ochridaspongia rotunda (Arndt,1937), Ephydatia fluviatilis (Linnaeus,1759), Oncosclera asiatica (Manconi & Ruengsawan,2012), Metania reticulata (Bowerbank,1863), Drulia browni (Bowerbank,1863), Drulia cristata (Weltner,1895), Drulia uruguayensis (Bonetto & Ezcurra de Drago,1969), and Eunapius carteri (Bowerbank,1863).Various extracts, including those obtained using methanol, acetone, aqueous, ethyl acetate, and methylene chloride, were employed in previous studies to evaluate a range of bioactivities. Observed bioactivities include antibacterial, antifungal, anti-quorum sensing, antiplasmodial, acetylcholinesterase inhibition, and anticancer properties, which are determined either from the crude extracts of the sponges themselves or by their associated microbes.