The shrimp Macrobrachium amazonicum (Heller, 1862) is a widely distributed native species in South America. This study presents an updated geographic distribution of the species through a systematic review of primary and secondary data, as well as reports of new native and non-native occurrences. The distribution extends approximately 4976 km, from the Maracaibo hydrographic ecoregion (Venezuela) to Lower Paraná (Argentina), between the latitudes 10°40’37”N and 27°20’31”S, and about 5226 km, from the Tuira River (Panama) to the Northeastern Atlantic hydrographic region (Rio Grande do Norte, Brazil), between the longitudes 79°31’30”W and 35°12’7”W. Covering much of South America and 2 hydrographic ecoregions in Panama, geographic expansion was detected with new continental and coastal records, both in native and non-native areas. New occurrences were recorded in the hydrographic ecoregions of Gurupi (Maranhão, Brazil); Lower Piranhas-Açu (Rio Grande do Norte, Brazil); Middle São Francisco (Bahia, Brazil); Upper Tocantins (Goiás, Brazil); Middle Paraguay (Mato Grosso do Sul, Brazil); Tarauacá (Amazonas, Brazil); Maracaibo, Trinidad, and Orinoco (Venezuela); Magdalena-Sinu (Colombia); Chagres (Panama); and the High Andes of the Amazon (Bolivia). The new record in Maracaibo extended the species’ range by 361 km to the north, and in Chagres, Panama, in Central America, by 51 km to the west. M. amazonicum exhibited the neotropical distribution which was already known for the species. Evidence of anthropogenic introduction in Brazilian reservoirs is supported by the absence of records in connection sites with the Orinoco and Amazon basins, which are geologically separated from the La Plata basin. The wide distribution of the species highlights its high adaptability to various environments.

The aim of this study was to understand the relationship between acoustic characteristics and body size of Korean rockfish Sebastes schlegelii in order to better estimate the body length of S. schlegelii by passive acoustic techniques. In this study, S. schlegelii, with a body length ranging from 21.7 to 24.8 cm (mean ± SD = 23.33 ± 0.93 cm) and a body weight of 144.2 to 250.3 g were selected as subjects. The aim was to explore the relationship between the acoustic characteristics of the fish and their standardized lengths through aquarium experiments. The vocalization frequency exhibited a main peak at around 150 Hz, a sub-peak at approximately 100 Hz, and the primary vocalization band extended from 100 to 350 Hz, with a pulse duration of 15.2 ± 2.4 ms. The results indicated that the peak frequency was negatively correlated with the standardized length, swim bladder length, width, and height (p <0.001). This research contributes to the understanding of the relationship between acoustic properties and body size and suggests the potential utility of passive acoustic monitoring techniques for estimating the body lengths of target species.

Polysaccharides exhibit a multitude of biological activities, including antioxidant, antitumor, immunoregulatory, hepatoprotective, and anti-inflammatory effects, but it is not known whether such effects occur in fish. Head kidney macrophages from turbot Scophthalmus maximus L. were isolated and cultured to examine the responsiveness to natural polysaccharides as potential immune stimulators. Polysaccharides used in the research included Echinacea purpurea polysaccharide (EPP), Astragalus polysaccharide (APS), lentinan (LNT), seaweed polysaccharide (SPS), and laminarin (LAM). The test compounds were added to the cultures and assessed for their effects on the growth and immunomodulatory functions of the cells. Based on the results of cell activity, reactive oxygen species, and nitic oxide assays, APS was selected as an immune stimulator. After addition of APS to the culture medium, a comprehensive proteomic analysis was conducted to identify signaling pathways responsible for the immune effects on macrophages. Specific immune pathway proteins were upregulated in cells in response to the addition of APS, including macrophage migration inhibitory factor, myosin-α, metalloproteinase inhibitor, and collagenase type III. In particular, compared with non-stimulated cells, the expression level of the TLR22 receptor was significantly increased in stimulated macrophages (p < 0.01). A KEGG pathway analysis indicated that relevant pathways were activated, including TNF, PI3K-Akt, and NF-κB signaling pathways. ELISA and qRT-PCR analysis also indicated that APS reduced IL-1β and TNF-α levels in the cells following lipopolysaccharide (LPS) stimulation. These data suggest that APS produced an immunoprotective effect on the head kidney macrophages of turbot at 800 µg ml-1, and enhanced cell proliferation. Our results provide evidence for anti-inflammatory properties of APS. As such, APS could be a candidate immunopotentiating agent for fish.

Hard substrate and vertical relief are limited habitat resources for reef-associated species in many regions. On the West Florida Shelf (WFS) of the Gulf of Mexico, red grouper Epinephelus morio act as ecosystem engineers by excavating sediments to expose limestone bedrock. Excavations can exceed 25 m in diameter and 2 m in depth and are among the most abundant WFS seafloor features at depths between 40 and 110 m. As part of a survey of hard-bottom habitats and associated reef fish assemblages, 1203 excavations were identified in WFS waters along the Florida Panhandle between 2014 and 2019. These excavations often contained subsided artificial reef material within their interior and infrequently included E. morio among observed fishes. We video-identified red snapper Lutjanus campechanus excavating sediments around 2 subsided artificial reefs in 2015 and 2017 for a total of approximately 56 min of excavation activity. A total of 24 excavation events were documented around a tire pile in 2015, and 5 were documented around a pyramid-shaped reef module in 2017. These observations help to explain the subsidence of artificial reefs and apparent excavation around their bases despite the scarcity of previously known excavating species. This suggests that L. campechanus might be ecosystem engineers on the WFS.

Few studies have explored the relationship between benthic and planktonic assemblages in reservoirs, despite their role in food chains and maintaining ecological functions. Macroinvertebrates play a crucial role in food webs and contribute about 42% of whole-lake secondary productivity. Therefore, their status is vital for maintaining good ecological functions. In this study, we selected Nanwan Reservoir, a eutrophic thermally stratified reservoir in China, to evaluate the community of macroinvertebrates in different seasons and explore the relationships between macroinvertebrate assemblages and different planktonic groups, including phytoplankton, protozoans, rotifers, and planktonic crustaceans. Cyanophyta and Bacillariophyta dominated the phytoplankton assemblages, and their proportions varied with seasons. The bad community of macroinvertebrates in summer, autumn, and winter could be attributed to the excessive growth of Cyanophyta or other phytoplankton. Based on the results of partial least squares regression, an algorithm used for prediction, we determined that the excessive growth of algae, crustaceans, protozoans, and Cyanophyta was detrimental to the development of macroinvertebrates, and was indicative of high nutrient loads in the reservoir. However, the growth of Bacillariophyta, Chrysophyta, and Euglenophyta was advantageous to macroinvertebrate assemblages and indicated a better ecological condition of the reservoir. The results of partial least squares structural equation modeling demonstrated close associations between phytoplankton and both zooplankton and macroinvertebrates, indicating their interdependence in this reservoir system. Our study results imply that the status of macroinvertebrates can be predicted by the abundance of some planktonic assemblages, and cost savings from selecting one of the planktonic groups to monitor ecological conditions could be accomplished in future studies.