Electivity Index Research Articles

A contribution to the knowledge on the diet and food preferences of Darevskia praticola (Reptilia: Lacertidae)

The Meadow lizard (Darevskia praticola s.l.) is one of the more poorly-studied lizard species in Europe, and no detailed data on its diet is available. We investigated a total of 180 faecal samples of D. praticola s.l. from two locations in Bulgaria, and conducted a comparison between sex and age groups (adult males, adult females, and immatures). In addition, the correlations between the consumed prey and the available resources were also analysed. Food selectivity was analysed by comparing the faecal samples with pit-fall trap samples on the basis of abundance of prey items from particular operational taxonomic units (OTUs). Results indicate that the diet of the Meadow lizard contains mainly arthropods (insects and spiders) and the most abundant prey items belong to Araneae, Auchenorrhyncha, and Coleoptera. According to the used electivity indices none of the OTUs are highly preferred by D. praticola s.l., but Formicidae are the most avoided OTU for all sex/age groups. Differences in food preferences can be found between adults and immatures, while differences among males and females seem to be insignificant. The lack of clear differentiation between males and females could be a result of their similar size and locomotor ability. In conclusion, our results reveal that Darevskia praticola s.l. is a generalist and it shows no food specialization due to its narrow spatial niche.

Feeding ecology of Neoarius leptaspis in the Rawa Biru Lake, Merauke, Indonesia

Abstract. Wibowo DN, Rukayah S, Wahayu NL, Mote N. 2022. Feeding ecology of Neoarius leptaspis in the Rawa Biru Lake, Merauke, Indonesia. Biodiversitas 23: 1327-1335. A few studies have been carried out on Neoarius leptaspis (Bleeker, 1862), however, its feeding ecology was not examined, especially for the sample from Rawa Biru Lake, Merauke, Papua, Indonesia. Therefore, this study aims to analyze the feeding ecology of N. leptaspis at 8 sampling sites in the lake, which were sampled in the morning and evening. The parameters observed were natural food diversity, mouth width ratio, intestine length ratio, stomach fullness and content, preponderance index, and electivity index. The result showed that 25 plankton species were observed in the waters. Neoarius leptaspis has a mouth width ratio of approximately 75% of head width. The full stomach was observed in the samples collected in the evening, where the diets were dominated by animal materials as indicated by the indexes of preponderance and electivity. The mouth width ratio, feeding periodicity, intestine length, and dominant diets were similar to the previous reports on the same species from other regions. This showed that N. leptaspis is a predatory fish species based on the feeding ecology data, which provides essential information for fisheries and conservation.

Do Birds of a Feather Always Flock Together? Assessing Differences in Group and Individual Zoo Enclosure Usage by Comparing Commonly Available Methods

Data on zoo enclosure usage provide meaningful evaluation of husbandry and welfare but for social species, group-level data may not capture individual occupancy preferences. Determining zone occupancy using group data may give an inaccurate assessment of enclosure suitability for each individual. We compared three formulae (traditional and modified Spread of Participation Index and Electivity Index) to determine how estimations of space usage compare between individuals and their group overall. Two flamingo flocks at two zoos were sampled with enclosures separated into discrete zones. Counts of where each bird in the flock was located at each minute of sampling were compared against the number of minutes that randomly selected individual flamingos spent in each zone. Overall, there was little difference in preferred zone occupancy when flock data were compared to individual data. Group data suggested that flamingos were more consistent in their enclosure usage, with individual data showing wider overall usage of enclosures. Individual Electivity Index (EI) values suggested zone underuse whereas group EI suggested zone overuse. As a proxy for welfare measurement, we recommend both group-level and individual monitoring of space use to provide a complete picture of how individuals within a social group occupy their space and choose where to be.

Which index should I use? A comparison of indices for enclosure use studies

Enclosure use assessments have gained popularity as one of the tools for animal welfare assessments and Post Occupancy Evaluations. There are now a plethora of studies and enclosure use indices available in published literature, and identification of the most appropriate index for each research question is often challenging. The benefits and limitations of four different enclosure use indices; Original and Modified Spread of Participation Index (SPI), Entropy, and Electivity Index were compared. Three artificial data sets were developed to represent the challenges commonly found in animal exhibits, and these indices were applied to these contrived enclosure settings. Three of the indices (Original SPI, Modified SPI, and Entropy) were used to assess a single measure of enclosure use variability. When zones within an exhibit were comparable in size, all three indices performed similarly. However, with less equal zone sizes, Modified SPI outperformed Original SPI and Entropy, suggesting that the Modified formula was more useful for assessing overall enclosure use variability under such conditions. Electivity Index assessed the use of individual zones, rather than the variability of use across the entire exhibit, and therefore could not be compared directly to the other three indices. This index is therefore most valuable for assessing individual resources, especially after exhibit modifications.

Unplanned 30-Day Readmission Rates for Autosomal Dominant Polycystic Kidney Disease: Insight from the Nationwide Readmissions Database

Introduction: Among end-stage kidney disease (ESKD) patients on dialysis with autosomal dominant polycystic kidney disease (ADPKD), relatively little is known about the epidemiology and risk factors for 30-day readmissions in the USA. Therefore, we evaluated the 30-day unplanned readmission rates and predictors and inpatient care costs among ESKD patients with and without ADPKD using a nationally representative, all-payer database. Methods: We utilized the Nationwide Readmissions Database from 2013 to 2018 to identify patients admitted for ESKD on dialysis with and without ADPKD using ICD-9 and ICD-10 codes. The primary outcome was a 30-day, unplanned readmission rate. Secondary outcomes were readmission reasons and timing, mortality, cost of hospitalization and rehospitalization, and adjusted predictors of readmissions. We used χ² tests, t tests, and Wilcoxon rank-sum tests for descriptive analyses and survey logistic regression to calculate adjusted odds ratios and 95% confidence intervals for associations with readmissions adjusting for confounders. Results: From 2013 to 2018, in a cohort of 1,404,144 hospitalizations with ESKD on dialysis as the primary and secondary diagnosis on index admission, there were 8,213 (0.58%) patients with ADPKD and 1,395,932 patients without ADPKD. Those who had ADPKD during index admissions had fewer 30 days readmissions (18.8 vs. 23.8%, p < 0.0001). The cost of hospitalizations and readmissions in ESKD on-dialysis patients with ADPKD was higher than non-ADPKD patients. Compared to ESKD patients without ADPKD who were readmitted, readmitted ADPKD patients were more likely to be younger with a lower Elixhauser Comorbidity Index (ECI) score; have received kidney transplant, lower source of income, elective index admissions, private insurance; and be discharged routinely, admitted in hospitals with larger bed size, in teaching hospitals, and less likely to get admitted through the emergency department. Younger age (<75 years), higher ECI score, longer length of stay, Medicare and Medicaid insurance, self-pay, discharge to a short-term hospital, specialized care, home health care, and against medical advice were associated with significantly increased odds of readmission. ADPKD patients were 31% less likely to get readmitted and 43% less likely to die during readmissions. Discussion/Conclusion: Nationwide, ESKD on-dialysis patients with ADPKD were less likely to have 30-day readmission than patients without ADPKD. Inpatient mortality during readmissions in patients admitted with ESKD on dialysis was lower with ADPKD as compared to those without ADPKD at the cost of higher health care expenses.

Food habits of belida fish (Notopterus notopterus, Pallas 1769) in Sei Gesek Reservoir, Bintan Regency, Riau Island, Indonesia

Sei Gesek Reservoir is located in Bintan Regency, Riau Island Province. The reservoir is one source of water for the community in Tanjungpinang City. One of the freshwater fish that inhabit the Sei Gesek Reservoir is the belida fish (Notopterus notopterus). The objective of this study was to the Relative Length of the Gut (RLG), type and food composition of belida fish (N. notopterus), and food comparative in the digestive tract of the belida fish (N. notopterus) with food resources in the substrate Sei Gesek reservoir, Bintan Regency, Riau Island. The method used in this research was the survey method. A sampling of belida fish (N. notopterus) was carried out in three months according to the fishing grounds. The data analysis used is Relative Length of the Gut (RLG), Index of Preponderance (IP), and Index of Electivity (E). The result showed that the total fish caught was 30, there were 16 males and 14 females. The relative length of the gut female and male belida fish (N. notopterus) were 0.21 and 0.25 respectively. Based on the relative length of the gut value, belida fish (N. notopterus) was classified as a carnivore. The food types of belida fish (N. notopterus) were fish, crustaceans, microalgae, macrophytes, annelids, nematodes, and detritus. Index of preponderance showed that the main food of belida fish (N. notopterus) in Sei Gesek Reservoir was small fish based on sex, the month of capture, and body length measurement. Index of electivity showed that the food type from the microalgae is Asterionella sp. and Closterium sp. not selected by belida fish (N. notopterus) as food.

The composition of haypiles of Turuchan pika (Preliminary analysis)

The species composition and abundance of plants in the Turuchan pika habitat and in its haypiles were studied in the talus surrounded by taiga on the Primorsky ridge. With the Ivlev’s Electivity Index, it was found that the pika was selective in collecting food: Veratrum nigrum and Urtica dioica, being relatively rare in the habitat, were highly preferred and abundant in the haypiles. The bulk of the haypiles also consisted of 4 species (Rubus matsumuranus, Sambucus sibirica, Populus tremula, Spiraea media) with a high abundance in the habitat and collected proportionally with their abundance. Many plant species being abundant in the habitat were not stored by pikas.

Habitat use and conservation threats to Wild Water Buffalo Bubalus arnee (Mammalia: Artiodactyla: Bovidae) in Koshi Tappu Wildlife Reserve, Nepal

Wild Water Buffalo (WWB) Bubalus arnee is an endangered species and a protected animal in Nepal. The remaining WWB population is located in Koshi Tappu Wildlife Reserve (KTWR), and it appears to have low viability under prevailing conditions. We assessed the habitat use and conservation threats to wild water buffalo in KTWR. For habitat analysis the quadrant method was used. Eighty-four quadrants of 25 m2 for trees, 168 quadrants of 10m2 for shrubs and 336 quadrants of 1 m2 for herbs were laid out in the study area. Ivlev’s electivity index (IV) was calculated to assess the use of different habitat components. The important Value Index (IVI) was used for vegetation assessment. A relative threat ranking method was used to assess conservation threats for wild buffalo and their habitats. Wild buffalo mostly preferred habitats with distance to water resources less than 500 m (IV= 0.4), less than 25 % crown coverage (IV= 0.39) and more than 75 % ground coverage (IV= 0.42). The trees species Phyllanthus emblica, Acacia catechu, shrub species Mimosa pudica and the herb species Brachiaria distachya, Vetiveria zizanioides, Imperata cylindrica, and Saccharum spontaneum were preferred by WWB in the study area. Among the different plant categories, we found that Acacia catechu was the most preferred tree species (IVI= 156.95), Mimosa pudica the most preferred shrub species (IVI= 58.68), and Imperata cylindrica the most preferred herb species (IVI= 64.73). Major conservation threats perceived by local stakeholders for wild buffaloes were overgrazing by cattle and genetic swamping through crossbreeding with domestic buffalo. Therefore, conservation of grass species through control of grazing, and prevention of cross breeding are measures supported by this study. Additionally, site-specific conservation strategies should be adopted, based on identified threats in the study area.

Diet Electivity and Preferences for Food Resources in Chiasmocleis leucosticta (Anura: Microhylidae)

Predator–prey interactions are complex relationships between both participants. Although many food items are available in the environment for a frog, it can choose to feed on one item instead of another, depending on several aspects of the prey, such as size, availability, abundance, mobility, and palatability. In this study we compared the frequency of each food item we observed in stomachs of the frog Chiasmocleis leucosticta with the availability of leaf litter arthropods we collected at the same place and time that of the frogs through Ivlev's electivity index. We verified that the electivity for ants and mites as food items in the diet of the population from Reserva Florestal de Morro Grande is an actual preference. Chiasmocleis leucosticta seems to elect smaller sized genera, such as Solenopsis and Pheidole, and avoid bigger and more aggressive ants, such as Pachycondyla, Camponotus, and Odontomachus. Also, we suggest that for C. leucosticta or even for other Microhylidae there is reason to believe that alkaloids are obtained as part of the diet; related studies on the biochemistry of this family, genus, and species are encouraged.

Barbus cyclolepis Heckel, 1837 (Teleostei: Cyprinidae)’in beslenmesi ve Istranca Deresi (İstanbul, Türkiye)’ndeki makroomurgasız faunası ile ilişkisi

The aims of the study are to determine what the organisms Barbus cyclolepis consume as food in its feeding environments and to compare prey consumption with prey abundance in the environment. The study was conducted in the Istranca Stream located in Istanbul (Turkey) during the spring and summer of 2012. A total of 142 B. cyclolepis specimens were captured and it is determined that 94 of them had full digestive tracts. Diet analyses of B. cyclolepis showed that its food spectrum consisted of 11 different food types, and the species was found to feed on insects, mainly Diptera (IRI%= 92.26%). The most abundant macroinvertebrate organisms in the environment were Diptera and Gastropoda. The electivity index of B. cyclolepis was positive for Diptera in the spring (E= 0.49), but the value was below the expected value of 0.6 for high selectivity. The electivity values for other macroinvertebrate groups, consumed in low proportions, were negative. In summer, the fish fed on Diptera, Plecoptera, and Trichoptera, but a high electivity index value was found only for Trichoptera (E= 0.87). Results showed that B. cyclolepis mainly consumed Diptera as food and did not consume Gastropoda, although it is the second most abundant macroinvertebrate group in the environment. A relationship was determined between the proportion of food groups consumed in the digestive tracts of fish and the ratios of macroinvertebrates in the environment, and as a result, it was specified that the fish was selective on Diptera.

What’s on the Menu for the Resident Brown Trout in a Rich Limestone Stream?

Examination of brown trout seasonal diet variation and investigation of terrestrial prey importance in a food-rich stream using four indices of prey importance (number and weight abundance, frequency of occurrence, index of relative importance) revealed that aquatic prey constituted the major part of the diet (&gt;90%) throughout the examined period. Despite Gammaridae being the most abundant in the environment, other less abundant organisms appeared to be important prey, including terrestrial organisms, with maximum consumption in September. The electivity index showed a positive selection of rare prey types; Tokeshi’s model revealed a specialist strategy for most of the population, except for those of 1+ age, who were inclining to generalist strategy. Diet diversity increased throughout April to October, and ages 1+ and 2+ exhibited a more diverse diet than older ages. Diet overlap between age classes was considerable, with less overlap observed in the later season. This pattern of differentiation in the diet of brown trout age classes and their feeding plasticity over seasonal scales, as observed in this food-rich stream, provides a starting point for further examination of this topic in streams with similar or different food richness and availability.

Selectivity of zooplanktonic preys in Heterobranchus longifilis larvae and fry

The present study was carried out to study the preferred prey in the larval and post-larval stages of Heterobranchus lonsifilis.Two hundred and forty larvae and fry of H. longifilis aged 2 to 23 days were stored in aquariums of 8 liters, fasted for 24 hours at the end of which they were fed to satiety with freshly collected zooplankton from fishponds. The day after feeding, the fish were euthanized and stored for stomach contents examination. The results showed that the zooplanktonic population density of the station ponds was 1356.73 individuals / L. This stand is composed of Cladocerans (455.85 individuals /l), nauplii (289.11 individuals / l), Rotifers (255.47 individuals / l), Copepodites (182.21 individuals / l) and Copepods adults (174.07 individuals /l). Furthermore, examination of stomach contents showed that adult Copepods were the most frequent and abundant prey category in stomach contents in terms of frequency of occurrence (66.7%) and numerical percentage (48.25%). In addition, these preys (adult copepods) constituted the preferred zooplankton prey in larvae and post-larvae of H. longifilis with an electivity index (E) equal to +0.5. Apart from the first size classes in which no prey has been observed in the stomach contents, the food preferences of H. longifilis larvae and fry do not vary with the size of the individuals. This study showed that adult copepods were the preferred zooplankton prey of H. longifilis larvae and fry.

Rural landscape dynamics over time and its consequences for habitat preference patterns of the grey partridge Perdix perdix.

Intensification of agricultural practices has drastically shaped farmland landscapes and generally caused a decline in spatial and temporal heterogeneity, thus leading to changes in habitat quality and food resources and a decline for most farmland birds Europe-wide. The relationship between complex landscape changes and habitat preferences of animals still remains poorly understood. Particularly, temporal and spatial changes in diversity may affect not only habitat choice but also population sizes. To answer that question, we have looked into a severely declining typical farmland bird species, the grey partridge Perdix perdix in a diverse farmland landscape near Vienna to investigate the specific habitat preferences in respect to the change of agricultural landscape over two decades and geographic scales. Using a dataset collected over 7.64 km² and between 2001 and 2017 around Vienna, we calculated Chesson’s electivity index to study the partridge’s change of habitat selection over time on two scales and between winter and spring in 2017. Although the farmland landscape underwent an ongoing diversification over the two decades, the grey partridges declined in numbers and shifted habitat use to less diverse habitats. During covey period in winter, partridges preferred also human infrastructure reservoirs such as roads and used more diverse areas with smaller fields than during breeding where they selected harvested fields but surprisingly, avoided hedges, fallow land and greening. Known as best partridge habitats, those structures when inappropriately managed might rather function as predator reservoirs. The avoidance behaviour may further be a consequence of increasing landscape structuring and edge effects by civilisation constructions. Besides, the loss in size and quality of partridge farmland is altered by crop choice and pesticides reducing plant and insect food. With declining breeding pairs, the grey partridge does not seem to adjust to these unsustainable landscape changes and farmland practices.

A new electivity index for diet studies that use count data

AbstractElectivity indices summarize the results of field‐based feeding studies by comparing the relative abundance of a potential prey item with its relative prevalence in the diet of a predator. We developed a new electivity index based on odds ratios calculated from counts of individual prey taxa in ambient samples and in the gut of a predator. Many indices of electivity have been developed, though the literature lacks consensus on which is the best. Why use our index instead of one of these? Most of the extant indices lack the means for assessing uncertainty, treat proportions determined from count data as fixed rather than estimates, and ignore the skewness inherent in binomial data. The new index is calculated by Bayesian estimation from the binomial distributions of proportions in ambient samples and gut contents, providing full likelihoods of the index and its components. Indices from groups of predators can be aggregated without bias using the log odds ratio. Using simulated data, we show how the credible intervals of the index shrink with increasing numbers of total ambient and consumed prey and become increasingly asymmetrical as the index approaches its limits (0 and 1). Applying the method to diet data for an endangered planktivorous fish, we show how aggregating among fish and among samples was necessary to overcome the limitations imposed by low counts and high variability among individual fish. The indices for the smallest of five prey taxa varied inversely with total prey abundance, consistent with optimal foraging theory.

Do macrophytes act as restaurants for fishes in a tropical beach? An approach using stomach content and prey availability analyses

Tropical sandy beaches have low primary productivity, thus depend on external food sources. Generally, allochthonous macrophytes, form the basis of these food webs, also may influence factors such as fish’s abundance, richness, species composition, and biomass. However, the role of such drifting macrophytes to the feeding ecology of fishes in tropical sandy beaches is uncertain. We aim to explain if this microhabitat acts as restaurants for fishes in a tropical sandy beach by performing stomach content and prey availability analyses using Stellifer punctatissimus as a model because it has an association with drifting macrophytes mainly on sandy beaches along the northeastern Brazilian coast. The most consumed prey was amphipods, which were eaten in a specialist way, especially by the smaller fishes. The prey availability along with electivity index suggested that this species may choose amphipods. Seasonal variations suggest that the fishes did not locate suitable prey as an effect of the availability, this can be also explained by optimal foraging theory and compensatory growth. Here, we redefined the S. punctatissimus trophic guild as zooplanktivorous, highlighting drifting macrophytes as restaurants for fishes in a tropical sandy beach as they are the main source of food.

Habitat selection of Himalayan Musk Deer Moschus leucogaster (Mammalia: Artiodactyla: Moschidae) with respect to biophysical attributes in Annapurna Conservation Area of Nepal

Himalayan or White-bellied Musk Deer Moschus leucogaster, an IUCN indexed endangered species, is distributed in isolated pockets in the Himalaya. The deer population is decreasing owing to several pressures that include habitat loss and fragmentation, and poaching. It is essential to identify preferred habitat characteristics to support appropriate management strategies for conserving this endangered species. This study was carried out in the Nysheang basin of Annapurna Conservation Area of Nepal to identify habitats preferred by the musk deer. Habitat field parameters were collected using transect surveys. To analyze vegetation use and availability, nested quadrate plots size 20 m2 were established. Ivlev’s electivity index (IV) (-1 to +1) was employed to determine habitat preference, and one-way ANOVA (F) and chi-square tests (χ2) were used to examine different habitat parameters. Similarly, the importance value index (IVI) of the vegetation was calculated. Our results showed that the Himalayan Musk Deer strongly preferred habitats at 3601–3800 m altitude (IV= 0.3, F= 4.58, P &lt;0.05), with 21–30º slope (IV= 0.2, F= 4.14, P &lt;0.05), 26–50 % crown cover (IV= 0.25, F= 4.45, P &lt;0.05), 26–50 % ground cover (IV= 0.15, F= 4.13, P &lt;0.05), and mixed forest (IV= 0.29, χ2= 28.82, df= 3, p &lt;0.001). Among the trees, Abies spectabilis (IVI= 74.87, IV= 0.035) and Rhododendron arboretum (IVI= 55.41, IV= 0.02) were the most preferred, while Rhododendron lepidotum, Cassiope fastigiata (IV= 0.35) and Berberis aristata (IV= 0.25) were the most preferred shrubs, and Primula denticulata (IV= 0.87) and Primula rotundifolia (IV= 0.31) were the most preferred herbs. These preferred habitat conditions should be maintained and conserved to sustain a viable population of deer in the study area. Further studies will be required to assess the effects of climate change on habitat suitability.

Размерно-возрастные различия биоэкологии Mesobuthus eupeus (C.L. Koch, 1839) (Arachnida, Scorpiones, Buthidae) в Азербайджане

The biotopical distribution, size and age structure of the population, nocturnal activity rhythm and feeding of the mottled scorpion (Mesobuthus eupeus) were studied. The research was conducted on the left bank of the Pirsagat river (Shirvan plain, Istern Azerbaijan). All discovered individuals of scorpions were divided into 5 size and age groups by the length of the metasome. The biotopical distribution of the mottled scorpion had a pronounced aggregated character with the formation of local clusters (settlements) in which 5 types of ratios of size and age groups were identified. It was found that individuals of II groups and I have unimodal, III and IV groups bimodal, and V group trimodal character of the rhythm of nocturnal activity. As the size of scorpions increases, the breadth of the nutrition spectrum increases, and the intensity of nutrition decreases. The index of electivity in II groups and I had negative values, and from III to V groups for some taxa of preys positive values. Representatives of the orders Isopoda (Crustacea), Aranei (Arachnida), Hymenoptera and Lepidoptera (Insecta) play a leading role in the nutrition of individuals of all size- age groups. As the size of scorpions increases, the proportion of members of the orders Hymenoptera, Blattodea and Collembola in their diet decreases. Representatives of the orders Coleoptera and Orthoptera are noted in the diet of scorpions from group III to V groups. Representatives of the orders Pulmonata (Gastropoda), Lumbricidae (Oligochaeta), Scolopendromorpha (Chilopoda), and Solifugae (Arachnida) are present in the diet only in individuals of IV and V groups.

Investigating the effect of social grouping on the behaviour of captive leopards

Big cats are both popular and well represented in zoological collections worldwide, and there is considerable interest in evidence-based studies to develop best practice husbandry guidelines. The majority of big cat species, including the leopard Panthera pardus are typically solitary in the wild, whereas in zoos they are sometimes maintained as pairs or larger groups. This study investigates the behaviour of six leopards housed as a trio, a pair, and singleton in the Parco Faunistico Valcorba, Italy. Behavioural data were collected using instantaneous focal sampling at one-minute intervals with continuous recording for events, and Electivity Index was used to assess the use of each enclosure zone by individual leopards. Poisson regressions were used to determine whether individual leopard, weather and decibel levels were predictors of behaviour change. Overall, the Poisson regressions were significant for all behaviours except allogrooming. Both affiliative and aggressive behaviours were observed most frequently in the recently mixed trio, and these were often initiated by the male. By contrast, the pair of leopards rarely interacted with one another. Irrespective of condition, leopards tended to overutilize a few key zones in their exhibits and did not use their enclosures evenly. However, there were differences in zone overlap: the pair housed leopards appeared to use different zones to one another, whilst the trio of leopards appeared to use similar zones. These data suggest that group housing may be a viable housing strategy for leopards, provided that the animals are given the opportunity to avoid each other should they choose to do so. However, personality and compatibility of leopards is likely to be a confounding factor that must be considered when developing group-housing husbandry strategies. Further studies with a focus on group housing of other felid species would be valuable to evidence-base their captive husbandry.

Makanan dan Kebiasaan Makan Siput Gonggong (Laevistrombus turturella) di Perairan Pulau Penyengat Kota Tanjungpinang

&lt;strong&gt;Food and Feeding Habits of Dog Conch (&lt;em&gt;Laevistrombus turturella&lt;/em&gt;) on Penyengat Island, Tanjungpinang&lt;/strong&gt;. Dog conch (Laevistrombus turturella) in Tanjungpinang, including commodities of high economic value. The purpose of this study was determine the ratio of the length of gut and the total body length, type of food and feeding habits of dog conch on the Penyengat Island, Tanjungpinang, Riau Islands. The study was conducted from May to November 2019. The sampling location was determined based on the purposive sampling method. The station were divided into 3 stations based on 1) the catch zone of the dog conch, 2) the characteristics of the dog conch habitat and 3) activities along the coast. Analysis of the data were provided the ratio of the length of gut and the total body length, index of preponderance, Viscero Somatic Index (VSI), total organic matter and index of electivity. The results showed that the ratio of the length of gut and the total body length of the dog conch were 1,53; 1,60; 1,66 and classified as an omnivore based on the ratio of the length of gut and the total body length. Types of dog conch food that have been found were detritus and microalgae class &lt;em&gt;Bacillariophyceae, Chlorophyceae,&lt;/em&gt; and &lt;em&gt;Crustaceans&lt;/em&gt;. The feeding habits of dog conch were detritus with the index of preponderance of 65-70% as the main food. VSI values were ranged from 24,27 to 36,35%. Value Index of electivity were ranged from 0,99-1% or close to 1.

Dynamic microhabitat shifts in space and time of caddisfly larvae (Insecta: Trichoptera) in a first\u2010order calcareous mountain stream

By studying substrate (choriotope) preferences of 25 caddisfly taxa in the Schreierbach stream, a calcareous, first order tributary of the Ybbs river (Lower Austria), we aimed on (1) detecting microhabitat preferences in space and time, (2) to relate this information with ontogenetic choriotope shifts, and (3) to explore relationships between feeding guilds and choriotopes chosen. For this, we took six sets of bi-monthly multi-habitat samples of larvae at three stream sections (360 samples). Densities were highest in Drusinae juveniles (53.60 %), Micrasema morosum (15.14 %), Drusus discolor (13.31 %) and D. monticola (4.46 %), and were significantly higher in the upper stream section (1900 ± 1039 larvae m− 2) than in the central (205 ± 23) and lower (141 ± 22). Ivlev electivity indices revealed preferences for Macrolithal in Rhyacophila spp. and Tinodes dives, for Microlithal in Drusinae juveniles, for Megalithal and Phytal in filtering Drusinae and Micrasema, and for Xylal and Akal in Limnephilinae. A cluster analysis of choriotope electivity yielded five clusters, corresponding with functional feeding types. At the instar level, the chosen grain size increased with increasing instar in some species. Observed habitat shifts in space and time reflected the interaction of instar-specific choriotope choice and longitudinal translocations.