Larvae Research Articles

Developmental histology of the liver in the Balkan crested newt Triturus ivanbureschi (Caudata: Salamandridae)

The liver, a crucial organ for metabolic processes, has a generally uniform histological structure across amphibian taxa. However, ontogenetic changes, particularly those related to biphasic life cycle and metamorphosis, are less documented. Here, we explored and described the liver histology of an emerging model organism, the Balkan crested newt (Triturus ivanbureschi) at three ontogenetic stages: larval, juvenile (just after metamorphosis) and adult. At the larval stage, the liver is characterized by hepatocytes containing large lipid droplets, poorly developed basement membranes in the blood vessels, and a lack of melanin-rich macrophage centers. Juveniles show transitional characteristics between larvae and adults. Lipid droplets in hepatocytes are abundant, but also, at the juvenile stage the well-developed basement membrane of blood vessels and melanomacrophages are present, as in adults. The presence of lipid droplets in hepatocytes during larval and juvenile stages suggests the liver's role in fat storage and energy provision during development and growth. Melanomacrophages, which synthesize melanin, perform phagocytosis, and neutralize free radicals, have been found in juveniles (after metamorphosis) and increase with age. The biphasic life cycle and liver histology transition in Triturus newts provide an insight in changes in liver histology and make them a suitable model for studying fat deposition regulation and the evolution of the immune system in terrestrial vertebrates.

Insecticidal effect of two Turkish entomopathogenic nematode isolates against Tribolium castaneum (Herbst) larvae and adults at different conditions

Red flour beetle, Tribolium castaneum (Herbst.), is the most common pest of stored grains and products. Aerial and contact pesticides are used to control this pest. However, the red flour beetle has also developed significant resistance to phosphine, the main fumigant currently in use worldwide. The adverse effects of pesticides on non-target organisms, groundwater contamination, residues on food crops, and the emergence of insect resistance to chemicals have compelled the industry to prioritize the development of alternative control measures. Entomopathogenic nematodes find application in various agricultural systems. The insecticidal effect of two isolates of Steinernema feltiae Filipjev (Nematoda: Steinernematidae) and Heterorhabditis bacteriophora Poinar (Nematoda: Heterorhabditidae) against the different stages of T. castaneum. The entomopathogenic nematode isolates were examined at four concentrations (0, 250, 500, and 1000 IJs/ml) with a distilled water at 15 and 25 ± 1 °C temperatures. Results revealed that both S. feltiae (A-16) caused with 92.33% mortality rate while H. bacteriophora (O-7) caused with 76.77% mortality in the last instar larvae of the red flour beetle while these two species caused 75.38% and 66.85% mortality in adults, at 25 °C. The effect of nematodes decreased as the temperature decreased. According to results, the mortality rate of T. castaneum larvae treated with S. feltiae (A-16) with (54.62%) was significantly higher than that of H. bacteriophora (O-7) with (32.13%) 96 h after inoculation at 15 °C. The data indicated that 1000 IJs/ml was the most effective concentration of tested EPN isolates for all larval and adult stages.In this study, our findings indicate that S. feltiae (A-16) and H. bacteriophora (O-7) can be used as effective biological control agents against both the larval and adult stages of the red flour beetle. The results demonstrate that EPNs are promising candidates for biocontrol of T. castaneum. This information is useful in designing future biological control programs.

The TOP-2/condensin II axis silences transcription during germline specification in C. elegans.

In C. elegans, the germline is specified via a preformation mechanism that relies on the PIE-1 protein's ability to globally silence mRNA transcription in germline precursor cells, also known as the P lineage. Recent work from our group has identified additional genome silencing events in C. elegans during oogenesis and in starved L1 larvae, and these require the condensin II complex, topoisomerase II (TOP-2), and components of the H3K9me/heterochromatin pathway. Interestingly, silencing in oocytes also requires PIE-1, but this is not the case in starved L1s. Here, we ask if additional genome silencing components besides PIE-1 are required to repress gene expression in the P lineage of early embryos, and we find that condensin II and TOP-2 are required and the H3K9me/heterochromatin pathway is not. We show that depletion of TOP-2/condensin II activates the normally suppressed RNA polymerase II to inappropriately transcribe somatic genes in the P lineage. We also present evidence that while both PIE-1 and TOP-2/condensin II are required for genome silencing in the P lineage, PIE-1 can silence transcription independently of TOP-2/condensin II when misexpressed in somatic cells. Thus, in oocytes, all three genome silencing systems (TOP-2/condensin II, H3K9me, and PIE-1) are operational while in both early embryos and starved L1s two of the three are active. Our data show that multiple, redundantly acting genome silencing mechanisms act in a mix and match manner to repress transcription at different developmental stages in the C. elegans germline.

Density of Limnoperna fortunei larval stages in a cascade of subtropical reservoirs: spatiotemporal variation and environmental influences.

The golden mussel (Limnoperna fortunei) is an invasive bivalve that has established itself in several South American river systems, impacting ecosystem functioning. Reservoir cascades provide their larvae with the means of rapid dispersal, but the relationship between environmental variables and larval stage structure remains unclear. In this study, the density of three L. fortunei larval stages and quantitative detection using DNA are analyzed in a cascade of five reservoirs in the upper Uruguay River Basin and associated with spatiotemporal variation in environmental parameters. The analysis of L. fortunei eDNA presence and absence in freshwater systems appears to be a valuable mapping tool; however, no significant link was found between the eDNA magnitude and the overall larval density. The increase in larval density was related to the fluctuation of environmental parameters over a year, with the highest average larval densities observed in the CN and ITA reservoirs, though no significant difference was observed between the five reservoirs, where D-shaped larvae predominated. During winter, larval density decreased significantly, however, other variables also contribute to species activity and development in the upper Uruguay River Basin reservoirs and may be considered limiting factors. The relationships between environmental parameters were evaluated using a multivariate model. The interaction between reservoir area and precipitation, water temperature, electrical conductivity, and dissolved oxygen had a significant effect on larval density but showed specific influences on each larval stage. Any increase in density was regulated by dissolved oxygen and electrical conductivity content at all larval stages. Furthermore, total phosphorus affected the density of F1 and F3 larvae. The interaction between reservoir area and precipitation, nitrate content, phosphate concentrations, and water temperature had the most influence on the density of F2 and F3 larval stages; the F1 stage was mainly affected by calcium concentrations. The isolated effect of precipitation also contributed to the density of F2 and F3 larvae. Our findings shed light on the interaction between different phases of golden mussel larvae and the main nutrients found in reservoirs, which may be a determining factor in the rise in density of the non-native species in these systems.

Transcriptomic analysis of sexually dimorphic cypris larvae of the rhizocephalan barnacle Peltogasterella gracilis

Peltogasterella gracilis (Cirripedia: Rhizocephala), a crustacean parasite of hermit crabs, displays genotypic sex determination. Its larvae are planktonic, and female larvae settle on the host. Subsequently, the females control the host's behavior by spreading a root-like structure called “the interna” within the host's body, and form sacs containing eggs called “the externae” outside the host's body. On the other hand, male larvae settle on immature externae and become dwarf males. The cypris larvae of P. gracilis show sexual dimorphism in size and morphology. However, there is no understanding of the molecular mechanisms underlying the sexual dimorphism observed at the larval stage. Here, we conducted a transcriptome analysis and compared the expression of genes in male and female cyprids to better understand their sexual differentiation and settlement processes. A total of 2870 differentially expressed transcripts, comprising 456 female- and 2414 male-biased transcripts were identified. Among the male-biased ones, ionotropic glutamate receptor-, heat shock protein-, acetylcholine-, and homeobox-, cuticle-related transcripts were included. Additionally, 29 gene ontology terms were associated with the sex-specific traits. The present study improves our understanding of sex determination, sexual differentiation, and settlement processes of rhizocephalans.

Comparative study on a unique architecture of the brook lamprey liver and that of the hagfish and banded houndshark liver.

Although the liver of the lamprey, a group of cyclostomes that diverged the earliest among vertebrates, has abundant bile ducts in the larval stage, which degenerate during metamorphosis, there is no comparative study on its architecture with other early diverged vertebrates in terms of the morphological evolution of vertebrate livers. The present study was undertaken to compare the characteristics of the brook lamprey liver with those of the hagfish and banded houndshark, which have the portal triad type liver architecture, and to discuss its evolution. Although the liver of the brook lamprey had two-cell cords of hepatocytes lined by sinusoids in the ammocoetes larval stage, intrahepatic bile ducts around portal veins penetrated into the liver parenchyma with convolution and gradual reduction in diameter. They also faced dilated sinusoids. The epithelial cells had characteristic intercellular spaces. These characteristics were distinct from those of bile ducts in the hagfish and banded houndshark livers. Although the liver architectures of the hagfish and banded houndshark were similar, the latter penetrated the intrahepatic bile ducts more deeply along the portal veins than the former, in which intrahepatic bile ducts were restricted near the hilum. After metamorphosis, bile ducts degenerated in brook lampreys. These data indicate that the liver architecture of the ammocoetes larva is unique in the parenchymal distribution of bile ducts, their sinusoidal facing, and morphology among extant vertebrates. The periportal distribution of intrahepatic biliary structures may have been established prior to the divergence of the cyclostomes and gnathostomes.

Proteomic analysis of extracellular vesicles and extracellular vesicle-depleted excretory-secretory products of Toxocara canis and Toxocara cati larval cultures

Toxocara canis and Toxocara cati are parasitic nematodes in the order Ascaridida, which inhabit the small intestines of dogs and cats, respectively, as adults. Although often nonpathogenic as adults, nematodes within this genus are capable of causing widespread disease throughout the host while in a larval stage, during which time larvae migrate throughout the body in a process termed larva migrans. Larvae are also capable of surviving within host tissues in an encysted arrested stage, without immune clearance by the host. The ability of larvae to survive within host tissues during migration and encystment may be attributed to immunomodulatory molecules released by the excretory cells of larvae in excretory-secretory (ES) products. ES products of parasites contain a variety of molecules, including proteins, lipids, and extracellular vesicles (EVs). Toxocara excretory-secretory (TES) products have been studied to some degree, with proteomic analysis of TES proteins described previously; however, investigation of the EVs within TES is lacking, despite the suggested role for these molecules in host interaction and potential immunomodulation. To further characterize the protein cargo within EVs in TES, EVs were isolated from larval cultures of T. canis and T. cati via ultrafiltration, with concurrent collection of EV-depleted TES filtrate for additional study. Isolated EVs and EV-depleted TES from both T. canis and T. cati were submitted for proteomic analysis by liquid chromatography tandem mass spectrometry (LC-MS/MS). Proteomic identification results revealed 140 proteins across all samples, with 16 shared by all samples, and 76 total proteins shared between T. canis and T. cati, present within EVs and EV-depleted TES. There were 17 proteins shared exclusively by EV samples, and 15 were shared exclusively between EV-depleted TES samples. Many shared proteins were associated with the host immune response. Several proteins were specific to either T. canis or T. cati, highlighting the potential use of these proteins as diagnostic tools in the differentiation of etiologic agents in cases of toxocariasis. The results of this study build upon previously reported proteomic evaluations of TES, contributing new information in regards to newly identified proteins, EV protein cargo within TES, and potential immunomodulatory functions of these proteins.

Evaluation of inhibitory, immunomodulatory, survival, and growth effects of host-derived Weissella confusa on Macrobrachium rosenbergii challenged with Vibrio parahaemolyticus

Macrobrachium rosenbergii is a highly valuable prawn species in aquaculture due to its current growing demand in the market. However, various bacterial diseases caused by Vibrio parahaemolyticus have been observed to induce mortality in larval, juvenile, and adult stages of M. rosenbergii. While antibiotics are commonly used to manage these diseases, they contribute to antimicrobial resistance, a global concern with serious environmental and health implications. Consequently, the scientific community is exploring host-derived beneficial microorganisms as functional feed additives, offering eco-friendly alternatives that boost shrimp and prawn immunity. The purpose of this study was to examine the effects of host-derived beneficial microorganisms from the gut of M. rosenbergii, on the inhibition, immunomodulation, survival, and growth of M. rosenbergii when exposed to V. parahaemolyticus. The result of this study showed that Weissella confusa C6, a lactic acid bacterium isolated from the gut of M. rosenbergii, significantly inhibits the growth of V. parahaemolyticus R1 as demonstrated in agar well diffusion assay and co-culture assay. Additionally, it showed immunomodulatory effects, indicated by elevated total hemocyte count (THC) and phenoloxidase (PO) activity during the bacterial challenge test. Furthermore, supplementing the diet with W. confusa led to significant improvements in M. rosenbergii, including increased survival rates, weight gain, specific growth rate, better feed conversion ratio, and reduced density of V. parahaemolyticus in the prawn's gut. Therefore, it can be considered a viable option for use as a feed supplement in prawn farming, enhancing M. rosenbergii's immune system, disease resistance, and overall health.

Differential gene expression responsible for caste determination at both larval and adult stages of Bombus terrestris

Differential gene expression responsible for caste determination at both larval and adult stages of Bombus terrestris

A modified matrix model captures the population dynamics for the primary vector of Lyme disease in North America

AbstractLyme disease, the most prevalent tick‐borne disease in North America, is caused by the bacterium Borrelia burgdorferi, and in the eastern and central United States, it is spread to humans by the black‐legged tick (Ixodes scapularis). Due to the complex, multiyear and multihost life cycle of this species, a matrix modeling approach is needed to effectively estimate subseasonal, multistage survival and transition dynamics in order to better understand and predict when population growth is high. Of the three questing tick life stages (larvae, nymphs, and adults), nymphs are most often associated with transmitting the bacteria to humans, and previous work suggests a mix of abiotic and biotic drivers are associated with nymph abundance. However, understanding tick population growth requires understanding mortality and transition probabilities for each stage and each stage may be individually and uniquely impacted by climate and host availability. A larval tick, for example, may experience warming temperatures differently than nymph or adults, because they are present on the landscape at different times. Here, we describe and validate a model that accounts for field sampling design and evaluates abiotic (temperature, relative humidity, precipitation) and biotic (host abundance) drivers of variation in tick population growth. To account for the drivers of subseasonal and interannual variability in demography, phenology, and population density, we built stage‐structured population models that account for variability in meteorology and host population abundance throughout the full tick lifecycle. Our model is fit and validated with 11 years of tick and host data from the northeastern United States. In this context, we found that a four‐stage model that includes unique transitions to and from a dormant, overwintering nymph state outperforms a model that only includes the three questing stages, and that incorporating the abundance of the predominant host species, Peromyscus leucopus, and weather variables improved predictions and model fit. Additionally, the model accurately predicted all three questing stages at sites different than where they were calibrated, showing that this model structure is generally transferable. Overall, this model lays a foundation for the real‐time iterative forecasting of tick populations needed to effectively protect public health.

Identifying insect predators using camera traps reveal unexpected predator communities in oilseed rape fields

Cameras are common tools for ecologists studying species abundance, richness, and interactions. They are mainly used to study large animals but are increasingly used to study invertebrates. Camera traps could be a powerful tool to identify and quantify the natural enemies, such as predators, of specific agricultural pests. This knowledge can then be applied to adapt farming practices to favour the predators identified and improve conservation biocontrol.Here, cameras were used to identify predators of two insect pests of oilseed rape (Brassica napus): the pollen beetle (Brassicogethes aeneus) and the brassica pod midge (Dasineura brassicae). These insects are spring pests of oilseed rape and are both susceptible to predation by ground-dwelling arthropods during their development cycle. The objectives of this study were to 1) identify the predators of the pest species, and 2) investigate the hypothesis that the diel activity periods of the predators match the timing of pest larval presence on the ground. Field observations were conducted in two locations over two consecutive years in the UK.In contrast to previous reports, our data collected using cameras showed that larval stages of predatory beetles are responsible for most of the predation events and that adult stages were not frequently observed feeding on the prey. Our data also showed that the traditional method, using pitfall traps, failed to detect the presence of large numbers of beetle larvae. Interestingly, the pests dropped to the ground and were therefore most susceptible to predation at the time when predators were most active.These results give new insight on the predators of the two most important spring pests of oilseed rape in Europe. This knowledge can be used by practitioners to develop framing practices targeted on enhancing the abundance of the larval stages of these beneficial arthropods to better control the pests in a more sustainable way.

Morphospace of lanternfish larvae and their interplay with oceanographic conditions from the southeastern Pacific Ocean

Lanternfish larval morphology is highly variable probably due to their adaptations to highly variable environmental conditions throughout ontogeny. To study the morphological variability of the larval stage of lanternfishes, samples were collected from the southeast Pacific Ocean between 2014 and 2022. Of the 24 species, nine belonged to the subfamily Lampanyctinae, two to the subfamily Diaphinae, one to the subfamily Notolychinae, one to the subfamily Gymnoscopelinae and 11 to the subfamily Myctophinae. A principal component analysis indicated the presence of body shapes varying from a slender and curved body, and upper jaw oriented downwards, with relatively rounded eyes, to taxa with robust bodies, particularly both the head and trunk, and elongated eyes in a dorsal-ventral plane (PC1 33%). Also, specimens varied from having short jaw, short snout, and slender body, to specimens with larger jaw (reaching behind the eye) and taller snout and trunk (PC2, 23%). Allometric effects were related to variations in body curvature and thickness (Diaphus theta, 12.9%), the curvature of the body and position of the eyes (Lampanyctodes hectoris, 25.1%), lengthening of the jaw and increase in eye size (Diogenichthys atlanticus, 24.6%), and a narrower body and smaller eyes (Hygophum bruuni, 20.5%). Four of the five subfamilies showed covariation between morphometrics and environmental conditions. Diaphinae, Gymnoscopelinae and Lampanyctinae body shape covaried with mean sea temperature of the water column, while Myctophinae larval shape covaried with mean salinity. In conclusion, this study quantifies shape variations during early lanternfish ontogeny from the southeastern Pacific Ocean, identifying main differences and allometric changes between the subfamilies belonging to Myctophidae, with a covariation between the shape of most lanternfish larvae and the environmental conditions experienced by myctophid early stages.

Distribution and genetic diversity of Bombyx mori nucleopolyhedrovirus in mass-reared silkworms in Thailand

Silk is an economically and culturally important product of Thailand that is threatened by the outbreaks of the Bombyx mori nucleopolyhedrovirus (BmNPV) in silkworm rearings. BmNPV infects the larval stages of the silkworm Bombyx mori, causing fatal viral infection and preventing the larvae from reaching the pupal stage. Numerous BmNPV isolates have been described from silk producing countries from all over the world. In this study, the geographic distribution of BmNPV in Thailand was analyzed by collecting 18 samples from different regions. The BmNPV samples were analyzed by PCR and whole genome sequencing was performed for eight specimens. Their genome size ranged from 125,888 bp to 126,783 bp, comprising 138 open reading frames. Although the sequenced BmNPV genomes could be phylogenetically differentiated, a correlation between geographic and genetic distance was not observed indicating a close relationship between the BmNPV from Thailand.

Morphological variation in first-formed shells of the Ordovician Paucicrura–Diceromyonia brachiopod lineage of North America

Abstract First-formed shells of several species of Dalmanellidae (Brachiopoda) from the Ordovician (Katian) of North America were measured and compared: Cincinnetina multisecta, Diceromyonia tersa, Diceromyonia storeya, Paucicrura corpulenta, Paucicrura rogata, and Paucicrura sillimani. Sizes and structures of the first-formed shells suggest that members of this family had planktotrophic subadults, with some species showing indications of only an unshelled larval stage and others showing both a larval stage and a shelled juvenile stage. This differs from modern rhynchonelliformean brachiopods, which all possess only a lecithotrophic larval stage. The range of sizes of first-formed shells of most studied species are similar, but P. sillimani of Baffin Island, Canada (middle Katian), has a significantly larger first-formed shell that formed during an extended juvenile stage. This may have enabled the species to colonize newly exploitable habitats during an interval of rapid sea level rise in Laurentia during the Katian. This plasticity of developmental modes in the Dalmanellidae shows not only that using distantly related modern brachiopods as an analog for extinct Paleozoic lineages may be misleading, but also that development can vary within a single lineage and that timing of developmental stages should not be considered a reliable character for use in phylogenetic studies of brachiopods.

The remarkable larval morphology of Rhaebo nasicus (Werner, 1903) (Amphibia: Anura: Bufonidae) with the erection of a new bufonid genus and insights into the evolution of suctorial tadpoles

Tadpoles serve as crucial evidence for testing systematic and taxonomic hypotheses. Suctorial tadpoles collected in Guyana were initially assigned to Rhaebo nasicus through molecular phylogeny. Subsequent analysis of larval and adult morphological traits revealed synapomorphies within the clade encompassing R. nasicus and R. ceratophrys, prompting the recognition of a new genus described herein as Adhaerobufo. The new genus is distinguished from other bufonids by specific phenotypic traits including an enlarged, suctorial oral disc with distinct papillae arrangements, and the presence of certain muscles and narial vacuities at the larval stage. However, only a few adult external characteristics (e.g., enlarged eyelids, infraocular cream spot), seem to be reliably discriminative from related genera. This study underscores the significance of larval morphology in anuran systematics and offers new insights into the evolution of suctorial and gastromyzophorous larvae within bufonids.

Effects of Rearing Temperature on Growth and Survival of Blackthroat Seaperch, Doederleinia berycoides (Hilgendorf, 1879), Post-Flexion Larvae and Juveniles

In post-flexion larval and juvenile stages of hatchery-reared blackthroat seaperch Doederleinia berycoides (Hilgendorf, 1879), the influence of water temperature on growth and survival was examined to identify the optimal rearing temperatures. Temperature treatments were conducted separately for pelagic post-flexion larvae (32 days post hatching [dph]) and settled juveniles (69 dph). Fish were transferred to four replicate 30 L tanks (30 larvae or 15 juveniles per tank) and reared for 15 days under five temperatures (13, 16, 19, 22 and 25 °C) maintained by using heaters and coolers. The mean survival rates (± SD) of post-flexion larvae were high (>73 %) for all temperatures (13 °C: 73.3 ± 6.9 %, 16 °C: 76.7 ± 6.8 %, 19 °C: 80.8 ± 10.7 %, 22 °C: 79.2.7 ± 2.8 %, 25 °C: 71.7 ± 4.4 %). Growth increased at higher temperatures and was significantly faster at 22 and 25 °C (P < 0.05) than lower temperatures. For juveniles, mean survival rates were significantly higher at 16–25 °C (>90%: 16 °C: 91.7 ± 1.7 %, 19 °C: 95.0 ± 3.2 %, 22 °C: 91.7 ± 1.7 %, 25 °C: 91.7 ± 5.0 %) than at 13 °C (71.7 ± 7.9 %) (P < 0.05). Juvenile growth, like that of post-flexion larvae, was faster at 22 and 25 °C. These results suggest that maintaining a high rearing temperature (22–25 °C) is important for enhancing the growth for post-flexion larvae and juveniles of blackthroat seaperch and reducing the rearing period to the size of release seedlings.

Assessment of Biological Characteristics of Red Spider Mite (Tetranychus urticae) Koch on Brinjal

Red spider mite, Tetranychus urticae Koch passed through five stages viz., egg, larva, protonymph, deutonymph and adult with three short resting stages known as quiescent stages which termed as nymphochrysalis, deutochrysalis and teleiochrysalis. The incubation period of egg was 3.28 ± 1.10 days with 0.13 ± 0.01 mm diameter in size. The average length and breadth of larva, nymphochrysalis, protonymph, deutochrysalis, deutonymphs, teleiochrysalis, adult male and adult female stage were 0.14 ± 0.01 and 0.10 ± 0.01; 0.19 ± 0.01 and 0.12 ± 0.01; 0.20 ± 0.01 and 0.12 ± 0.01; 0.24 ± 0.02 and 0.13 ± 0.01, 0.29 ± 0.02 and 15 ± 0.02, 0.35 ± 0.03 and 0.18 ± 0.01, 0.43 ± 0.04 and 0.19 ± 0.01; and 0.47 ± 0.02 and 0.22 ± 0.01 mm, respectively. The mean duration of male and female larva, nymphochrysalis, protonymph, deutochrysalis, deutonymphs, teleiochrysalis and adult was 2.07 ± 0.73 and 2.36 ± 0.22, 0.58 ± 0.32 and 0.68 ± 0.22, 2.23 ± 0.35 and 2.92 ± 0.81, 0.70 ± 0.35 and 0.76 ± 0.39, 2.12 ± 0.44 and 2.56 ± 0.51, 0.77 ± 0.19 and 0.87 ± 0.37 and 7.12 ± 0.93 and 11.08 ± 0.86 days, respectively. Female of T. urticae occupied 2.48 ± 0.96, 5.32 ± 0.99 and 2.35 ± 0.84 days as pre-oviposition, oviposition and post-oviposition period, respectively. Total life period of male and female was 19.14 ± 2.06 and 23.85 ± 1.65 days, respectively. The average fecundity and hatching percentage were 47.60 ± 6.13 days and 91.11 ± 4.14 per cent, respectively with 1 : 2.50 sex ratio.

CALCIUM CHANGES IN Bulimulus tenuissimus (MOLLUSCA) EXPERIMENTALLY INFECTED WITH LARVAL Angiostrongylus cantonensis (NEMATODA)

Only in 2018 Bulimulus tenuissimus was incriminated as an intermediate host of Angiostrongylus cantonensis, the causative agent of infections in domestic, wild animals and humans, causing neural angiostrongyliasis or eosinophilic meningitis in humans. The present study aimed to infect the mollusk B. tenuissimus, using L1 larvae of A. cantonensis, under laboratory conditions, and to analyse the changes that occurred in the calcium metabolism of the host mollusk. The infection caused hypercalcification in the shell of B. tenuissimus infected with A. cantonensis, with a 242% increase in the concentration of CaCO3, at the end of the prepatent period, in the shells of infected mollusks and hypercalcemia, especially at the end of the third week of infection (+18.51%) in relation to the control group. The interference of the parasitic nematode in the calcium metabolism of the host mollusk was evidenced, with reductions in tissue deposits and elevation of calcemia and calcium content in the shell.

Parasites Infestations Status in Fish Species from River Orogodo, a Freshwater Municipal Stream, Southern Nigeria

Parasites are ubiquitous and fish are host to some of these parasites that can be zoonotic. Assessing their status and trends is vital in public health safety, and aquatic ecology. The study aimed to identify parasites, assess the prevalence, identify the infection sites and also determine the variation in infection among sexes in fish from River Orogodo, Agbor, Delta State. A total of 780 fish, comprising 23 species belonging to 12 fish families were collected between September 2014 and August 2019 using cast nets of various mesh sizes and funnel entrance traps. Fishes were identified and examined using standard morphological keys. According to established procedures, parasitological indexes were determined by inspecting various external and internal body parts. The overall prevalence recovered was 196 (25.1%) with twenty-two parasites including larvae stages both from external and internal parts of the fish. These include 5 protozoans (Microsporidium gen sp, Trichodina spp, Epistylis sp, Crytobia sp and Chilodonella sp), Myxobolus sp, 5 nematodes (Procamallanus laevionchus, Camallanus sp, Cucullanus sp, contracaecum larvae, Rhabdochona sp); 3 acanthocephalans (Acanthogyrus sp, Neoerchinorhynchus sp and Acanthocephalus sp), 4 cestodes (Monobothroides woodlandi, Wenyonia sp, Proteocephalid sp including plerocercoid larvae); 3 digeneans (Clinostomum sp, Euclinostomum heterostomum, Centrocestus sp, unidentified metacerceriae in the liver). The study revealed that female fish (32.5%) were more infected than their male counterparts (26.4%). The results indicate that fishes in River Orogodo, Delta State are hosts of various external and internal parasites, which may be of public health and aquacultural importance.

In vivo screening of flavonoid compounds revealed quercetin as a potential drug to improve recovery of angiostrongyliasis after albendazole treatment.

Human angiostrongyliasis, caused by consuming the larva stage of Angiostrongylus cantonensis, is an infectious disease involving the central nervous system (CNS) and ophthalmic system. Current treatment of angiostrongyliasis involves albendazole accompanied by analgesics and corticosteroids. However, long-term use of corticosteroids may lead to significant adverse effects. In the current study, we screened through different potentially effective flavonoid compounds and identified quercetin as an effective anti-inflammatory agent in an angiostrongyliasis mouse model. Our results identified that quercetin may reverse the neurological defects in mice with angiostrongyliasis. The brain pathology and inflammatory status were also improved by albendazole-quercetin co-therapy. Further analysis showed that albendazole-quercetin co-therapy had a better therapeutic effect than albendazole or quercetin monotherapy. This therapeutic effect was achieved by inhibiting the brain inflammasome activation and apoptosis. Albendazole-quercetin co-therapy also leads to the inhibition of brain IL-5, possibly leading to improved pathology. Our results here proved that quercetin may serve as a potential adjuvant drug in treating human angiostrongyliasis.