Will ocean acidification affect the digestive physiology and gut microbiota of whelk *Brunneifusus ternatanus*?

To understand the physiological responses of the Brunneifusus ternatanus to future ocean acidification (OA), histology, enzyme activity and gut bacterial composition at different pH levels (Control : C group, pH 8.1; Exposure period : EP group, pH 7.3) for 28 days were studied under laboratory conditions. Microbiota composition was analyzed using 16S rRNA gene amplicon sequencing. Enzyme activities of trypsin (TRY), lipase (LPS), amylase (AMS), and lysozyme (LZM) were used as biochemical indicators, as well as weight gain rate (WGR), specific growth rate (SGR) as growth indicators. The stress caused by OA resulted in alterations to the intestine, including partially swollen and degranulated enterocytes and rough endoplasmic reticulum (RER). The relative abundance of the core phylum in the acidified group changed significantly, showing an increase in Tenericutes and a decrease in Proteobacteria. Firmicutes/Bacteroides ratio declined from 4.38 in the control group to 1.25 in the EP group. We found that the enzymes TRY, LPS, and AMS activities were inhibited at reduced pH, which was positively correlated with the dominant genera Mycoplasma and Bacteroides; while LZM activities showed a significant increment, but showing a strong negative correlation. Furthermore, both WG and SRG values showed a depression at low pH lever. These results suggest that if anthropogenic CO2 emissions continue to accelerate, OA could lead to a negative impact on the whelk health, also compromising their growth performance and even survival. These findings will benefit the future risk assessments of OA or other related emerging environmental issue

A Glycoprotein in Shells of Conspecifics Induces Larval Settlement of the Pacific Oyster Crassostrea gigas

Settlement of larvae of Crassostrea gigas on shell chips (SC) prepared from shells of 11 different species of mollusks was investigated. Furthermore, the settlement inducing compound in the shell of C. gigas was extracted and subjected to various treatments to characterize the chemical cue. C. gigas larvae settled on SC of all species tested except on Patinopecten yessoensis and Atrina pinnata. In SC of species that induced C. gigas larvae to settle, settlement was proportionate to the amount of SC supplied to the larvae. When compared to C. gigas SC, all species except Crassostrea nippona showed lower settlement inducing activities, suggesting that the cue may be more abundant or in a more available form to the larvae in shells of conspecific and C. nippona than in other species. The settlement inducing activity of C. gigas SC remained intact after antibiotic treatment. Extraction of C. gigas SC with diethyl ether (Et2O-ex), ethanol (EtOH-ex), and water (Aq-ex) did not induce larval settlement of C. gigas larvae. However, extraction of C. gigas SC with 2N of hydrochloric acid (HCl-ex) induced larval settlement that was at the same level as the SC. The settlement inducing compound in the HCl-ex was stable at 100°C but was destroyed or degraded after pepsin, trypsin, PNGase F and trifluoromethanesulfonic acid treatments. This chemical cue eluted between the molecular mass range of 45 and 150 kDa after gel filtration and revealed a major band at 55 kDa on the SDS-PAGE gel after staining with Stains-all. Thus, a 55 kDa glycoprotein component in the organic matrix of C. gigas shells is hypothesized to be the chemical basis of larval settlement on conspecifics

The effect of aquarium color background on the survival, growth performance, body coloration, and enzymatic activity of laboratory cultured Cherax quadricarinatus juveniles

The effect of different background colors (red, yellow, blue, green, white, and black) on crayfish Cherax quadricarinatus juveniles was evaluated over a 50-day rearing period. Survival, growth, body color, and enzymatic activity were assessed. At the experiment's conclusion, survival, growth, and weight were calculated. Body color was analyzed using Lab color composition, and enzyme activities (amylase, lipase, superoxide dismutase, catalase) were assessed in the dissected hepatopancreas. Results showed no effect of background color on survival rate (P > 0.05). However, crayfish reared against black and red backgrounds exhibited significantly higher weight, growth rate, and condition factor compared to those on white and yellow backgrounds (P < 0.05). Background color also influenced body color, with deeper coloration observed on claws, tail, and abdomen against white, yellow, green, red, black, and blue backgrounds. Crayfish on white and yellow backgrounds showed similar coloration (ΔE = 1.69), in contrast to specimens cultured against the blue background (ΔE = 23.94). The amylase (AMS) activity varied, with the highest in black backgrounds and the lowest in blue. Lipase (LPS) activity did not differ significantly except for lower activity in the blue and green background. Superoxide dismutase (SOD) activity was highest in the red background and lowest in the green background. Catalase (CAT) activity varied significantly, with the highest in red and black groups and inhibitory activity in green. Further research is needed to understand the underlying mechanisms behind enzymatic activity variations due to background color. The effect of environmental conditions on body color modification should be considered in C. quadricarinatus juvenile culture. Dark backgrounds are recommended for growth, while light backgrounds should be avoided

Effect of Different Colored LED Lighting on the Growth and Pigment Content of <i>Isochrysis zhanjiangensis</i> under Laboratory Conditions

Light is one of the most important environmental factors affecting the growth and reproduction of algae. In this study, the effect of various LED colors on the productivity, chlorophyll (Chl-a, Chl-b, and total Chl), protein, and carbohydrate content of Isochrysis zhanjiangensis in indoor culture was investigated. Microalgae monocultures were cultivated under five different colors (red, green, blue, yellow, and white) for twenty-one days. The microalgae cultured under red light exhibited a higher specific growth rate (0.4431 ± 0.0055 µ day−1), and under white light a higher productivity (0.0728 ± 0.0013 g L−1 day−1). The poorest performance was observed under yellow and green lights. Interestingly, green light exhibited the highest levels of chlorophylls (Chl-a, 1.473 ± 0.037 mg L−1; Chl-b, 1.504 ± 0.001 mg L−1; total Chl, 2.827 ± 0.083 mg L−1). The highest protein content was observed under the white light (524.1935 ± 6.5846 mg L−1), whereas the carbohydrate content was remarkably high under the blue light (24.4697 ± 0.0206 mg L−1). This study is important in terms of the selection of light at the appropriate color (wavelength) to increase the content of organic compounds desired to be obtained indoors with the potential for commercially produced cultures

Percentages of post larvae on pepsin and trypsin treated FD HCl-ex of <i>C. gigas</i> SC.

<p>Shaded and open boxes represent pepsin and trypsin treated experiments, respectively. Data are means of 9 replicates and error bars represent standard deviations (SD). Lines connected groups that were compared using Wald test. Asterisks * indicate significantly different groups (p<0.05).</p

SDS-PAGE gel image of <i>C. gigas</i> FD HCl-ex, F1 (fraction 1) and F2 (fraction 2) stained with Stains-all.

<p>SDS-PAGE was performed on 10% polyacrylamide gels; 10 µg protein content was loaded in each lane. M indicates the molecular weight markers. Molecular weights were estimated using the molecular weight marker “Broad Range” (BIORAD).</p

Percentages of post larvae that settled on SC of the different species of mollusks.

<p>Closed squares are means of 6 to 30 replicates and error bars represent standard deviation (SD). Letters indicate results of the post hoc Tukey HSD test of activities within species at 0, 10, 50 and 100 mg. Values connected by the same letter are not significantly different (p≥0.05).</p

Experimental design for the characterization of the settlement inducer in <i>C. gigas</i> SC.

<p>Experimental design for the characterization of the settlement inducer in <i>C. gigas</i> SC.</p

Absorbance and eluted fractions of FD HCl-ex of <i>C. gigas</i> SC after filtration in Superdex 200 10/300 GL column, and the percentages of post larvae at 50, 100 and 200 mg SC equivalent of each of the pooled fractions (F1: 45–150 kDa, F2:1.3–44 kDa, and F3:<1.3 kDa molecular mass ranges).

<p>Vo indicates void volume. Data are means of 6 to 9 replicates and error bars represent standard deviations (SD). Letters indicate results of the post hoc Tukey HSD test. Values connected by the same letter are not significantly different (p≥0.05).</p

ANOVA result of the effect of species and amount of SC on <i>C. gigas</i> larval settlement.

<p> Statistics of the quasi-binomial GLM applied to the output for dependent variable larval settlement. Species refers to the 11 species of SC tested; amount refers to the weight of SC.</p