Distribution Of Larvae Research Articles

A global, historical database of tuna, billfish, and saury larval distributions

Knowing the distribution of fish larvae can inform fisheries science and resource management in several ways, by: 1) providing information on spawning areas; 2) identifying key areas to manage and conserve; and 3) helping to understand how fish populations are affected by anthropogenic pressures, such as overfishing and climate change. With the expansion of industrial fishing activity after 1945, there was increased sampling of fish larvae to help better understand variation in fish stocks. However, large-scale larval records are rare and often unavailable. Here we digitize data from Nishikawa et al. (1985), which were collected from 1956–1981 and are near-global (50°N–50°S), seasonal distribution maps of fish larvae of 18 mainly commercial pelagic taxa of the families Scombridae, Xiphiidae, Istiophoridae, Scombrolabracidae, and Scomberesocidae. Data were collected from the Pacific, Atlantic, and Indian Oceans. We present four seasonal 1° × 1° resolution maps per taxa representing larval abundance per grid cell and highlight some of the main patterns. Data are made available as delimited text, raster, and vector files.

The Application of DNA Barcoding in Crustacean Larvae Identification from the Zhongsha Islands, South China Sea

Marine crustaceans are known as a group with high morphological diversity and great economic value. Most species have planktonic larval stages that are difficult to identify to species level using traditional approaches because of insufficient morphological diagnostic characters or taxonomic descriptions. We used DNA barcoding and molecular species identification to investigate the species diversity and distribution of crustacean larvae in the Zhongsha Islands waters, South China Sea. In total, 108 sequences were obtained from crustacean larvae collected in the Zhongsha Islands waters in 2019 using vertical hauls between the depths of 5 and 200 m. The molecular classification approach confirmed that 108 sequences represented crustaceans typical to the South China Sea, with 70 species identified, representing 43 genera, 23 families, and 4 orders. However, the cytochrome c oxidase subunit I gene sequences of only 27 species identified from the larval samples matched with available sequences taken from adults in GenBank. The comparison of K2P distances yielded a notable gap of 3.5–10.7% between intraspecific and interspecific distances across the sequence dataset. More than 80% of the crustacean larvae species belonged to the order Decapoda, and they displayed marked differences in their distributionsin the Zhongshan Islands waters. The orders Calanoida and Amphipoda were represented by the fewest species, which were recorded only at the edge of the Zhongsha Atoll.

Climate Change Will Fragment Florida Stone Crab Communities

Many marine species have been shown to be threatened by both ocean acidification and ocean warming which are reducing survival, altering behavior, and posing limits on physiology, especially during earlier life stages. The commercially important Florida stone crab, Menippe mercenaria, is one species that is affected by reduced seawater pH and elevated seawater temperatures. In this study, we determined the impacts of reduced pH and elevated temperature on the distribution of the stone crab larvae along the West Florida Shelf. To understand the dispersion of the larvae, we coupled the multi-scale ocean model SLIM with a larval dispersal model. We then conducted a connectivity study and evaluated the impacts of climate stressors by looking at four different scenarios which included models that represented the dispersion of stone crab larvae under: 1) present day conditions as modelled by SLIM for the temperature and NEMO-PISCES for the pH, 2) SSP1-2.6 scenario (-0.037 reduction in pH and +0.5°C compared to present-day conditions), 3) SSP2-4.5 scenario(-0.15 reduction in pH and +1.5°C) and 4) SSP5-8.5 scenario (-0.375 reduction in pH and +3.5°C). Our results show a clear impact of these climate change stressors on larval dispersal and on the subsequent stone crab distribution. Our results indicate that future climate change could result in stone crabs moving north or into deeper waters. We also observed an increase in the number of larvae settling in deeper waters (defined as the non-fishing zone in this study with depths exceeding 30 m) that are not typically part of the commercial fishing zone. The distance travelled by larvae, however, is likely to decrease, resulting in an increase of self-recruitment and decrease of the size of the sub-populations. A shift of the spawning period, to earlier in the spring, is also likely to occur. Our results suggest that habitats in the non-fishing zone cannot serve as a significant source of larvae for the habitats in the fishing zone (defined as water depth< 30 m) since there is very little exchange (< 5% of all exchanges) between the two zones. These results indicate that the stone crab populations in Florida may be susceptible to community fragmentation and that the management of the fishery should consider the potential impacts of future climate change scenarios.

Larva migrans in BALB/c mice experimentally infected with Toxocara cati ensured by PCR assay

BackgroundToxocara cati, the cat roundworm, is a parasitic nematode that known to cause toxocariasis in intermediate hosts and humans. In this study, we characterized the dynamics of T. cati larvae migration in BALB/c mice after inoculation with eggs and ensured the migration detecting the larval DNA by a PCR. To evaluate the dynamics of larval migration and distribution, twenty-four BALB/c mice were orally inoculated with 2500 T. cati infective eggs and the visceral organs of the infected animals were examined by pepsin digestion and microscopic parasite counts, followed by PCR at day 1 to 28 post-inoculation.ResultsThe PCR assays were successfully used for detection of T. cati larvae in tissue samples and T. cati larvae and the DNAs were found in the liver, lungs, heart, kidneys and the brain. We detected T. cati in 92.2% of tissue samples by PCR, 30% higher than the conventional pepsin digestion technique.ConclusionOur findings demonstrated that the PCR assay is a sensitive and specific for the detection of T. cati larvae. Therefore, it could become a useful tool for the investigation of the dynamics of larval migration and Toxocara infection in murine model.

Mosquito larva distribution and natural Wolbachia infection in campus areas of Nakhon Ratchasima, Thailand

Objective: To determine the prevalence of mosquito larvae in campus areas and the infection rate of endosymbiotic bacteria, Wolbachia in mosquito larvae. Method: The mosquito larvae samples were collected in residential areas and academic buildings of Suranaree University of Technology located in Northeastern Thailand during 2017-2018. Mosquito species identification was performed using GLOBE mosquito protocols and Rattanarithikul & Panthusiri’s keys. The gene encoding for the surface protein of Wolbachia was amplified by PCR and confirmed by DNA sequencing. Results: Armigeres sp. is the highest proportion of mosquito larvae followed by Culex spp., Aedes albopictus, Aedes aegypti, and Toxorynchites spp., respectively. Aedes aegypti have breeding sites mostly in the containers found indoors, whereas the main breeding sites of Aedes albopictus were found in both outdoors and indoors. The House Index and Breteau Index for Aedes spp. was more than 5% and 20%, respectively, in both areas, indicating that these areas are dengue sensitive. The highest proportion of Wolbachia infection was found in the larvae of Culex spp. (86.21%), followed by Aedes albopictus (69.23%) and rarely detected in Aedes aegypti (9.09%). Conclusion: The present study reported the first natural infection of Wolbachia in mosquito larvae in Thailand. Our result suggested that the mosquito species containing higher proportion of Wolbachia are less likely to be vectors for dengue. Therefore, Wolbachia transfection in mosquito larvae could be applied as a biocontrol for dengue and other mosquito-borne disease prevention.

Insight into Trichinella britovi Infection in Pigs: Effect of Various Infectious Doses on Larvae Density and Spatial Larvae Distribution in Carcasses and Comparison of the Detection of Anti-T. britovi IgG of Three Different Commercial ELISA Tests and Immunoblot Assay.

There is limited information available on the Trichinella britovi (T. britovi) muscle larvae (ML) distribution in pig muscle and the humoral immune response of pigs infected with moderate doses of this parasite; therefore, this study investigated the infectivity of a Polish strain of T. britovi for pigs, the antibody response of this host to various doses of T. britovi, and the efficiency of three different commercial ELISA kits and an immunoblot assay at detecting anti-T. britovi IgG. No significant differences in terms of the infection level of particular muscles or of whole carcasses between pigs infected with 3000 and those infected with 5000 ML of T. britovi were observed. The highest intensity of T. britovi infection was reported in the diaphragm pillars. The larvae of T. britovi showed homogeneous distribution with respect to the muscle side. Statistically, specific IgG antibodies against excretory–secretory (ES) antigens of Trichinella ML were first detected by all ELISA protocols on day 36 post infection; however, individual pig results showed some differences between the three tests applied. A significant increase in the level of anti-T. britovi IgG was observed between days 36 and 41 post infection, and from day 45 until day 62 after T. britovi infection, production of these antibodies reached its plateau phase. No positive correlation was found between the anti-T. britovi IgG level and the larvae density in 15 different muscles. Sera of T. britovi-infected pigs showed reactivity with T. britovi ML ES antigens of 62, 55, and 52 kDa. The results provide novel information on spatial larvae distribution in muscles and the humoral immune response of pigs exposed to two different doses of a Polish strain of T. britovi, extend knowledge on serological diagnostic tools which may be introduced in veterinary practice for the detection of T. britovi infections in pig production, and offer practical solutions for meat hygiene inspectors in the field at sampling sites when examining pig carcasses for Trichinella.

Habitat characteristics and spatial distribution of Anopheles mosquito larvae in malaria elimination settings in Dembiya District, Northwestern Ethiopia

The persistence and productivity of larval habitat is a major factor that regulates adult Anopheles mosquitoes’ density and malaria transmission intensity. A study on Anopheles mosquitoes breeding habitat diversity, distribution, characteristics and larval density in different seasons across various habitat types is important to design effective larval control strategies. This study was aimed to investigate the Anopheles species composition, the productivity of larval breeding habitats, and their spatial distribution in selected localities of Dembiya District. A longitudinal study on characteristics and productivity of Anopheles larval breeding habitats was conducted from June 2018 to May 2019 in selected localities of Dembiya District. Anopheles larvae were collected using standard WHO dipper (350 ml capacity) and droppers depending on the size of the breeding habitats. Physicochemical characteristics of breeding habitats were measured and Anopheles mosquitoes were identified by using morphological keys and polymerase chain reaction (PCR). Logistic regression was used to assess the association of environmental factors with the presence or absence of Anopheles mosquitoes larvae. A total of 1,629 Anopheles larvae and 185 pupae were collected from both localities. These comprise Anopheles arabiensis, An. pharoensis, An. coustani, An. christyi, An. squamosus, An. demeilloni, An. danicalicus, and An. cinereus. The highest density of Anopheles larvae was collected from at a drying water canal (14.7 ± 3.5 larvae/dip) and the lowest larval density was recorded in rain water pools (0.2 ± 0.2 larvae/dip). The presence or absence of Anopheles larvae were significantly associated with physical characteristics of the breeding habitats such as turbidity (mid turbid) (AOR = 66.03; 95% CI: 2.01-2168.24, p = 0.019) and presence of grasses (AOR = 12.62; 95% CI: 1.29-122.78, p = 0.029). This study indicated that breeding sites persist and support Anopheles mosquito breeding activities and impact malaria control and elimination programs. Incorporating vector control strategies targeting Anopheles larvae as a part of malaria intervention strategies could enhance the malaria control and elimination program in the study area.

Distribution, abundance, and species composition of fish larvae and juveniles of Gobiidae in the Cimaja estuary, Palabuhanratu, Indonesia

Cimaja estuary has been well known as a fishing ground for fish larvae and juveniles of amphidromous fishes. The local people call this group of fish impun and collect them frequently for consumption. However, no information about fish diversity and recruitment of amphidromous goby in the Cimaja estuary is known. Therefore, this study aims to reveal species composition, recruitment pattern, and estimation of the abundance of fish larval and juvenile amphidromous goby in the Cimaja estuary day and night. Sampling was performed monthly during the new moon period from December 2020 to February 2021. Fish specimens were identified to the lowest taxon level through a morphological approach. A total of 23,331 larvae and juveniles of Gobiidae were collected, and most of them were Sicyopterus spp. The juvenile stage (11.9-21.8 mm BL) comprised 95.6% of the catches, postflexion larvae (6.9-11.8 mm BL) contributed 3.5% to the total yield and 0.9% of the total capture consisting of flexion larvae (3.9-6.8 mm BL). Gobiid fishes are preferred to recruit and migrate into the Cimaja river during the day than at night time (p < 0.05), and their movement to the upstream are synchronized with the tidal cycle.

Microbial regulation of intestinal motility provides resistance against helminth infection

Soil-transmitted helminths cause widespread disease, infecting ~1.5 billion people living within poverty-stricken regions of tropical and subtropical countries. As adult worms inhabit the intestine alongside bacterial communities, we determined whether the bacterial microbiota impacted on host resistance against intestinal helminth infection. We infected germ-free, antibiotic-treated and specific pathogen-free mice, with the intestinal helminth Heligmosomoides polygyrus bakeri. Mice harboured increased parasite numbers in the absence of a bacterial microbiota, despite mounting a robust helminth-induced type 2 immune response. Alterations to parasite behaviour could already be observed at early time points following infection, including more proximal distribution of infective larvae along the intestinal tract and increased migration in a Baermann assay. Mice lacking a complex bacterial microbiota exhibited reduced levels of intestinal acetylcholine, a major excitatory intestinal neurotransmitter that promotes intestinal transit by activating muscarinic receptors. Both intestinal motility and host resistance against larval infection were restored by treatment with the muscarinic agonist bethanechol. These data provide evidence that a complex bacterial microbiota provides the host with resistance against intestinal helminths via its ability to regulate intestinal motility.

Distribution Patterns of Reef Fish Larvae in the Dipolog Srait, Philippines

The composition, abundance and distribution of reef fish were strongly influenced by the trends in salinity, temperature and mixing regimes of the water during the three oceanographic cruises conducted in the vicinity of the marine reserve networks of Dipolog Strait. Forty-seven families of reef fish larvae were identified. Carangidae, Labridae, Scaridae, Gobiidae and Apogonidae were the top five most abundant larvae comprising 64.7 % of the total number of reef fish larvae collected. Shifts in the dominance of the top five most abundant reef fish families occurred primarily between the northeast and southwest monsoons coinciding with the changes in the temperature profiles of the water column. Abundance of reef fish larvae showed variability across the three sampling periods due to the succession of the dominant species of reef fish larvae. Fluctuations in salinity brought about by the transition from Northeast to Southwest monsoon period could explain the variation. Density distribution of reef fish larvae significantly increased with the increasing depth of the mixed layer during northeast monsoon period. The downwelling off the coast of southern Negros in February and April cruises contributed to the high abundance of reef fish larvae in this part of the strait, while the uniform mixing of the water column in June 2010 at southwest monsoon resulted in the weakening of density gradient of reef fish larvae.The study demonstrated the variable responses of the reef fish larvae to the gradients of chlorophyll in the Dipolog Strait. A better understanding on the retention mechanism of reef fish larvae along the coast of southern Negros, where the main marine reserve networks exist, is provided by the present study.

Vertical distribution patterns of early stages of mesopelagic fishes along 110 °E, south-east Indian Ocean

This study examines vertical distribution of the early stages of mesopelagic fishes in the south-eastern Indian Ocean and oceanographic factors that may affect it. This investigation along the 110 °E transect formed part of the second International Indian Ocean Expedition (IIOE-2). Depth-stratified samples to 500 m depth of early stages of mesopelagic fishes were obtained by means a multinet EZ-1 m2. This net captured larvae and transforming stages, but juveniles and adults were also caught, particularly at night. Diel vertical patterns of the different species and stages were analysed relative to the oceanographic conditions encountered at the 20 stations along the transect. This paper provides the ranges of vertical occurrence and weighted mean depth for larvae (135 taxa), and post-metamorphic stages (75 taxa) of fishes caught during the survey. Despite the varying vertical profiles of oceanographic parameters encountered, there were consistent patterns within species and families along the transect, with broader vertical distribution of larvae at the southern stations, where the upper mixed layer was deeper. During both day and night, larval stages of all the species were concentrated in the epipelagic zone, with some differences in terms of weighted mean depth (WMD) between taxa, but with no significant differences in vertical location between day and night. Transforming and juvenile-adult stages, however, presented a wider vertical distribution range than larval stages, and showed important differences among families and species. For example, Myctophidae and Phosichthyidae species presented the highest concentrations in the upper 50–100 m at night, and a much deeper distribution during the day, thereby indicating night vertical migration behaviour of transforming and juvenile-adult stages. By contrast, during these stages the Gonostomatidae Cyclothone spp. and the Sternoptychidae Argyropelecus spp. occurred deeper than the epipelagic layer during both day and night. Although these vertical patterns concur with results from other oceans, the WMD along 110 °E was slightly deeper than that observed in other areas, such as the eastern Atlantic, possibly related to water transparency in this oligotrophic part of the world's oceans.

Molecular Characterization and Expression Analysis of Putative Class C (Glutamate Family) G Protein-Coupled Receptors in Ascidian Styela clava.

Simple SummaryAscidians, known as the closest invertebrate relative to the vertebrate group, have a biphasic life cycle including the larval and sessile adult stages with strong adaptability to diverse environments. The nervous system of ascidians plays an essential role in its adaption to the external environment, but the molecular mechanisms underlying this process still need to be further clarified. The Class C G protein-coupled receptors (GPCRs) are a group of cell surface sensors for neurotransmitters and external chemicals, playing important functions in neurotransmission. We systematically characterized the putative Class C GPCRs in an important invasive ascidian species Styela clava and then analyzed their expression levels during different developmental stages and distribution in swimming larvae and multiple tissues of the adults. Our study suggests that S. clava Class C GPCRs potentially function as important molecules during neurotransmission related to physiological and morphogenetic changes in larvae and adults.In this study, we performed the genome-wide domain analysis and sequence alignment on the genome of Styela clava, and obtained a repertoire of 204 putative GPCRs, which exhibited a highly reduced gene number compared to vertebrates and cephalochordates. In this repertoire, six Class C GPCRs, including four metabotropic glutamate receptors (Sc-GRMs), one calcium-sensing receptor (Sc-CaSR), and one gamma-aminobutyric acid (GABA) type B receptor 2-like (Sc-GABABR2-like) were identified, with the absence of type 1 taste and vomeronasal receptors. All the Sc-GRMs and Sc-CaSR contained the typical “Venus flytrap” and cysteine-rich domains required for ligand binding and subsequent propagation of conformational changes. In swimming larvae, Sc-grm3 and Sc-casr were mainly expressed at the junction of the sensory vesicle and tail nerve cord while the transcripts of Sc-grm4, Sc-grm7a, and Sc-grm7b appeared at the anterior trunk, which suggested their important functions in neurotransmission. The high expression of these Class C receptors at tail-regression and metamorphic juvenile stages hinted at their potential involvement in regulating metamorphosis. In adults, the transcripts were highly expressed in several peripheral tissues, raising the possibility that S. clava Class C GPCRs might function as neurotransmission modulators peripherally after metamorphosis. Our study systematically characterized the ancestral chordate Class C GPCRs to provide insights into the origin and evolution of these receptors in chordates and their roles in regulating physiological and morphogenetic changes relevant to the development and environmental adaption.

Host transmission dynamics of first- and third-stage Angiostrongylus cantonensis larvae in Bullastra lessoni.

Given the importance of angiostrongyliasis as an emerging infectious disease of humans, companion animals, and wildlife, the current study focused on the transmission dynamics of first- and third-stage larvae of the parasitic nematode, Angiostrongylus cantonensis. The migration of infective larvae and their subsequent distribution within the Lymnaeidae snail, Bullastra lessoni, were investigated over time using microscopic examination of histological sections and fresh tissue. Snails were divided into four anatomical regions: (i) anterior and (ii) posterior cephalopedal masses, (iii) mantle skirt and (iv) visceral mass. The viability of free-swimming third-stage larvae, after their release from snail tissues, was evaluated in vitro by propidium iodide staining and infectivity by in vivo infection of Wistar rats. Snails were sequentially dissected over time to assess the number and anatomical distribution of larvae within each snail and hence infer their migration pathway. Herein, ongoing larval migratory activity was detected over 28 days post-infection. A comparison of infection rates and the larval distribution within the four designated snail regions demonstrated a significant relationship between anatomical region and density of infective larvae, with larvae mostly distributed in the anterior cephalopedal mass (43.6 ± 10.8%) and the mantle skirt (33.0 ± 8.8%). Propidium iodide staining showed that free-swimming third-stage larvae retained viability for between 4 and 8 weeks when stored under laboratory conditions. In contrast to viability, larval infectivity in rats remained for up to 2 weeks only. Knowledge gained from the current work could provide information on the development of new approaches to controlling the transmission of this parasite.

FEATURES OF THE DISTRIBUTION OF TRICHINELLA LARVAE IN THE MUSCLES OF SPONTANEOUSLY INFECTED RED FOXES (VULPES VULPES)

The issues related to the distribution of trichinella larvae in various groups of skeletal muscles of animals are quite relevant, as they are of great importance for the diagnosis of trichinosis. There is a lot of contradictory information in scientific papers about the distribution of trichinella larvae in the muscles of spontaneously infected predatory mammals. The purpose of our research was to study the distribution of trichinella larvae in various skeletal muscle groups in spontaneously infected red foxes (Vulpes vulpes). Detection of trichinella larvae was carried out by compressor trichinelloscopy and by the method of digesting muscle tissue in artificial gastric juice. Capsule-forming trichinella (Trichinella spp.) were found in animal muscles. The most intensively affected were the large masticatory muscle (68.1±30.7 larvae in 1 g of muscle tissue), diaphragm (65.3±25.6), intercostal muscles (63.7±23.1) and tongue root muscles (58.9±25.2). A lower intensity of invasion was noted in the splenius (36.6±14.4). In the triceps muscle of the shoulder (2.1±2.2) and the calf muscle (2.9±2.5), a very low intensity of invasion was recorded. Trichinella larvae were not found in the latissimus dorsi muscle, trapezius muscle, biceps femoris muscle, superficial gluteus muscle and middle gluteal muscle. Thus, in the spontaneously infected red foxes studied by us, the highest invasion intensity was noted in the muscles of the trunk and head.

Molecular identification and distribution of insect larvae in the Lower Danube River

As a major component of freshwater ecosystems, insect species play an important role in nutrient cycling and are often used as bioindicators of water pollution. Although extensive studies have characterized insects from freshwater habitats, little is known about the distribution of these species along the Lower Sector of the Danube River. Therefore, this survey conducted in the Danube section within the Romanian territory aimed to identify insect larvae belonging to seven different species of Odonata, Trichoptera, Ephemeroptera, Lepidoptera and Megaloptera by DNA barcoding and to investigate their distribution, density and frequency. A total of 41 quantitative macrozoobenthic samples were collected during two consecutive years (2019 and 2020). Species showed large differences in the distribution and density along different sections, and an overall tendency to populate downstream areas, except for Sialis morio. On the other hand, only Hydropsyche bulgaromanorum, Triaenodes bicolor and S. morio larvae were identified in the upstream section (Sulina branch). These data provide baseline information on the larger range of some of the most common aquatic insects in the Romanian Danube section in relation to several environmental parameters based on the first molecular identification of these species using COI gene sequencing.

Magnetic fields generated by the DC cables of offshore wind farms have no effect on spatial distribution or swimming behavior of lesser sandeel larvae (Ammodytes marinus)

In the North Sea, the number and size of offshore wind (OW) turbines, together with the associated network of High Voltage Direct Current (HVDC) subsea cables, will increase rapidly over the coming years. HVDC cables produce magnetic fields (MFs) that might have an impact on marine animals that encounter them. One of the fish species that is at risk of exposure to MF associated with OW is the lesser sandeel (Ammodytes marinus), a keystone species of the North Sea basin. Lesser sandeel could be exposed to MF as larvae, when they drift in proximity of OW turbines. Whether MFs impact the behavior of lesser sandeel larvae, with possible downstream effects on their dispersal and survival, is unknown. We tested the behavior of 56 lesser sandeel larvae, using a setup designed to simulate the scenario of larvae drifting past a DC cable. We exposed the larvae to a MF intensity gradient (150-50 μT) that is within the range of MFs produced by HVDC subsea cables. Exposure to the MF gradient did not affect the spatial distribution of lesser sandeel larvae in a raceway tank 50 cm long, 7 cm wide and 3.5 cm deep. Nor did the MF alter their swimming speed, acceleration or distance moved. These results show that static MF from DC cables would not impact behavior of lesser sandeel larvae during the larval period of their life although it does not exclude the possibility that later life stages could be affected.

Bioconversion of fresh chicken excreta by housefly larvae (Musca domestica L.) in relation to excreta sterilisation and carbohydrate addition

Housefly larvae can be reared on manure and used as animal feed. Larvae can utilise proteins and easily digestible carbohydrates and have a largely unknown relation with microorganisms. The hypothesis addressed in this study was that larvae compete with microorganisms for easily digestible carbohydrates such as starch. This was tested by adding starch or (non-digestible) fructo-oligosaccharides (FOS) to unsterilised or heat-sterilised fresh chicken excreta. Experimental substrates were unsterilised excreta (E), sterilised excreta (sE) with either starch (E + star, sE + star) or FOS (E + FOS, sE + FOS). The highest wet yield (9.7 g) and heaviest larvae (13.2 mg) were on sE + star, followed by E (7.2 g and 8.1 mg). Both E + FOS and sE + FOS had minimal yields and larval weights (0.3 and 0.2 g, 2.9 and 1.7 mg) with E + star intermediate (3.3 g and 7.5 mg). Survival differed between diets, sE and E averaged 70%, sE + star 57%, E + star 33% with 9% for E + FOS and sE + FOS. DM bioconversion decreased from E (3.5%), sE + star (3.1%), sE (2.6%), E + star (1%) to E + FOS and sE + FOS (0.1%). Nitrogen bioconversion was highest on sE + star (9.9%) and E (9.3%), lower on sE (6.6%), E + star (4%) and the lowest on E + FOS and sE + FOS (0.5%). Different substrate temperature profiles during the larval growth period and different larval size distributions were found for the different substrates. The results support the hypothesis that larvae compete with microorganisms for an easily digestible carbohydrate (starch).

Assessment of spatial distribution of Plutella xylostella on Cabbage (Brassica oleracea var. capitata)

The present investigation aimed to study the distribution pattern of larvae and pupae of diamondback moth (DMB) on cabbage (Brassica oleracea var. capitata L.). The experiment was laid out in randomized block design at the Horticulture farm, Rajasthan College of Agriculture, Maharana Pratap University of Agriculture and Technology, Udaipur, Rajasthan during rabi 2019–20 and 2020–21. The present study was carried out to understand the pattern and behaviour of the spatial distribution of DBM in cabbage. The prevalence of DBM incidence was recorded in terms of the number of larvae and pupae per plant on ten randomly selected plants in each replication at weekly intervals. The various indices, viz. variance to mean ratio, exponent–K, patchiness index, clumping index, mean colony size, mean clump size, Iwao’s patchiness regression and Taylor’s power law were analyzed to test the dispersion behaviour of diamondback moth. The value of various indices exceeded unity in most of the weekly observations indicating clumped type of distribution of diamondback moth larvae and pupae on cabbage. Clumped distribution behaviour of DBM population can aid the understanding of the pest ecology and its management.

Seasonal distribution of fish larvae in mangrove-seagrass seascapes of Zanzibar (Tanzania)

Fish larvae supply in nearshore vegetated habitats, such as seagrass meadows and mangroves, contributes significantly to sustainable fish stocks. Yet, little information is available on distribution patterns of fish larvae in mangrove and seagrass habitats of the western Indian Ocean. The present study investigated the abundance, diversity and assemblage composition of fish larvae in mangrove creeks, inshore seagrass meadows (located adjacent to mangroves) and nearshore seagrass meadows (located in-between mangroves and coral reefs) in two coastal seascapes of Zanzibar (Tanzania) across seasons for 1 year. The highest mean abundances of fish larvae were recorded in mangrove creeks, while nearshore- and inshore seagrass meadows showed similar mean abundance levels. Generally, fish larvae representing 42 families were identified, with the fourteen most abundant families comprising 83% of all specimens. Fish larvae communities were dominated by specimens of the postflexion growth stage in all habitats, except in mangrove creeks in one of the two seascapes (i.e. Chwaka Bay) from April through June when abundances of the preflexion and very small-sized individuals were exceptionally high. Slightly higher fish larvae abundances were observed in mangroves during the southeast monsoon compared to the northeast monsoon, and there were also differences across months within monsoon periods for all three habitats studied. Assemblage composition of larvae did, however, not vary significantly in time or space. Our findings suggest that mangroves and seagrass meadows are highly linked shallow-water habitats with high retention of fish larvae contributing to similarity in assemblage compositions across shallow coastal seascapes. Conservation and management efforts should prioritize connected shallow-water seascapes for protection of fish larvae and to uphold sustainable coastal fisheries.

Does the Kuroshio Current transport planktonic larvae of the hydrothermal-vent crabXenograpsusTakeda &amp; Kurata, 1977 (Decapoda: Brachyura: Grapsoidea)?

AbstractThe grapsoid crab XenograpsusTakeda &amp; Kurata, 1977 inhabiting shallow-water hydrothermal vents shows a limited distribution in the western Pacific, thus providing a good opportunity to observe how a species expands its distribution and establishes and maintains a metapopulation. We analyzed four Japanese populations of Xenograpsus (Kueishan-dao, Showa Iwo-jima, Shikine-jima, and Omuro-dashi) distributed along the Kuroshio Current to assess whether population connectivity is affected by the current. The reconstructed phylogenetic tree indicated that the specimens analyzed belong to a single clade, including X. testudinatusNg, Huang &amp; Ho, 2000 in Kueishan-dao. We could not include genetic data of X. novaeinsularisTakeda &amp; Kurata, 1977 and tentatively refer to the specimens analyzed as X. testudinatus. All four populations shared the two major haplotypes. Statistically significant population differentiation was nevertheless recognized between Showa Iwo-jima and Omuro-dashi, about 1,000 km apart. The number of individuals analyzed in Shikine-jima (N = 11) and Kueishan-dao (N = 5) might not be enough to detect differences. The relative age of population expansion seemed to correlate with the direction of the Kuroshio Countercurrent. Together with knowledge on the distribution of the planktonic larvae, larvae of X. testudinatus stay and mostly contribute to its source population. The Kuroshio Current system occasionally transports the larvae and juveniles, or even adult individuals on floating pumice and other materials, to eventually settle into newly formed habitats after volcanic eruptions, thus expanding the distributional range of the species.