Urbanization causes changes in the function and structure of ecosystems. This leads to adaptive and non-adaptive evolution of organisms living in cities. Habitat fragmentation can play an important role, especially for less mobile species like land snails. One evolutionary impact of urban fragmentation that has been understudied is changes in morphological traits related to sexual selection. The present study aims to investigate the effect of increased urbanization on co-evolution of the male and female reproductive organs in the grove snail (Cepaea nemoralis), a simultaneous hermaphrodite. Grove snails were collected in three different cities in the Netherlands along urban-rural transects. Male (sperm donor) and female (sperm recipient) reproductive traits were measured for 271 individuals. The expectation was that, due to a decrease in population density in urban areas, both the male and female reproductive organs would show changes that can be explained as resulting from reduced mating competition. Our results confirmed that there is an effect on the male spermatophore-producing parts and the female spermatophorereceiving parts. In addition, there was a positive correlation between the size of the male spermatophore-producing and female spermatophore-receiving organs. These findings invite for further research into the biotic and abiotic factors that influence sexually-selected morphological traits in urbanized areas.
Digestive peptidases in the Pacific whiteleg shrimp Penaeus vannamei comprise a set of at least three trypsins, two chymotrypsins, and one metallopeptidase (Mpc1), with trypsin and chymotrypsin performing 60% of the digestive function. In this exploratory study, we investigated the relative importance of digestive trypsin by silencing trypsin-2 (Try2) using RNA interference (RNAi) and assessing its impact on the expression and activity of other peptidases and the muscle amino acid profile. RNAi was induced by injecting double-stranded RNA of trypsin-2 (dsRNATry2) into the hepatopancreas (also known as the digestive gland), with controls including non-injected specimens and those injected with dsRNA-GFP or NaCl. The bioassays evaluated the effect of single and multiple doses of dsRNA in the gene expression of trypsins, chymotrypsin-B1, and Mpc1, as well as total and specific proteolytic activities. Results showed that, at 120 h post-injection, trypsin-2 expression was significantly lower in the dsRNA-Try2 group compared with noninjected and NaCl-injected controls, whereas no significant difference was detected relative to the dsRNA-GFP group, indicating that a non-specific dsRNA effect cannot be excluded. Other genes (e.g., trypsin-1, trypsin-3, chymotrypsin B1, Mpc1) and proteolytic activity measures showed directionally consistent but non-significant trends. Zymography qualitatively supported reductions in trypsin-associated bands. With repeated dosing, specific trypsin activity decreased, whereas changes in total and chymotrypsin activities varied. Muscle amino acid patterns and epithelial changes in the hepatopancreas suggested possible systemic responses; however, limited replication and pooling precluded statistical inference for these endpoints. No compensatory mechanism for reduced trypsin transcripts was observed.
The snail Biomphalaria glabrata has primarily been studied because it is an intermediate host to the parasite, Schistosoma mansoni, a causative agent of human schistosomiasis. The interaction between B. glabrata and S. mansoni has been extensively researched but the nervous system of B. glabrata is less understood. Of the available studies on the neurobiology of B. glabrata, most have focused on the adult stage with few if any examining the nervous system in embryos. Therefore, this study aimed to fill a gap in our knowledge by studying the development of the nervous system in embryonic B. glabrata. Using immunochemistry, we localized serotonin- and FMRFamide-immunoreactive (IR) elements in the nervous system of B. glabrata embryos, with the serotonin-IR structures appearing prior to those demonstrating FMRFamide-IR. At the time of hatching, there were welldeveloped and distinct serotonin-IR and FMRFamide-IR neural networks present in the headfoot of B. glabrata late veligers. In addition, serotonin was shown to play a role in regulating embryonic rotation.
Zooplankton play an integral role as both food sources for upper trophic levels and grazers on lower trophic levels in aquatic ecosystems. Planktivorous fish can alter zooplankton vertical distribution by directly decreasing the density of zooplankton in particular layers of the water column or by inducing behavioral shifts, such as migration. Few studies have examined the density and vertical distribution of zooplankton across geographically and morphometrically similar lakes with varying fish communities and zooplanktivory intensity. Here we assessed zooplankton vertical distributions during the day in three lakes close in proximity that differed substantially in fish community structure. We hypothesized that, in the presence of zooplanktivorous fish, large-bodied zooplankton would remain deep in the water column during the day as a predator-avoidance tactic and small-bodied zooplankton densities would be high throughout the water column as they are less susceptible to visual predation. We also quantified changes in zooplankton vertical distribution and density that occurred with changes in predation from daytime to nighttime, and over time, including before and after the rapid loss of zooplanktivorous fish in one of the lakes due to the introduction of a piscivorous fish. With high predation pressure from zooplanktivorous fish, the daytime vertical distribution of zooplankton was relatively deeper (below the Secchi depth) and large-bodied zooplankton densities were lower overall. With no fish predation, zooplankton clustered above the Secchi depth and crustaceans were more abundant than rotifers. As climate change and introduced fish species continue to affect lake fish communities, zooplankton communities could also be impacted, with cascading effects on the rest of the food web, thereby affecting lake ecosystem function.
The intestinal microbiota serves as a critical mediator of digestive efficiency, nutrient assimilation, and host-pathogen interactions in aquatic organisms. To systematically investigate microbial community dynamics within integrated aquaculture environments, we conducted a comparative analysis of bacterial assemblages across three distinct ecological niches in a pond : the intestinal tract of the leech Whitmania pigra, benthic sediment, and water column. The results demonstrated significant variation in both the structure and diversity of bacterial communities among W. pigra intestines, sediment, and water. Sediment samples exhibited the highest richness and diversity, which decreased markedly in water samples and were lowest in intestinal samples. In the intestines of W. pigra, the predominant phyla included Firmicutes, Proteobacteria, and Bacteroidota. By contrast, sediment was dominated by Proteobacteria and Bacteroidota, while aquaculture water was characterized by Proteobacteria, Bacteroidota, Cyanobacteria, and Actinobacteriota. At the genus level, Aeromonas, Cetobacterium, and Epulopiscium were prevalent in the intestines, whereas unclassified Bacteroidales and Hydrogenophaga were notable in sediment. In aquaculture water, Planktothrix_NIVA_CYA_15 and Flavobacterium were the dominant genera. Compared with water samples, intestinal bacterial communities showed greater similarity to those in sediment. Traceability analysis further indicated that 41.14% of the intestinal bacterial communities originated from sediment, while 27.35% were derived from water. Overall, bacterial communities in W. pigra intestines, sediment habitats, and aquaculture water exhibited significant differences but were closely interconnected, providing valuable insights for further research on the W. pigra intestinal microbiota and sustainable aquaculture practices.
