A stable isotope analysis of the dietary patterns of the aquatic apex predator, the African tigerfish (Hydrocynus vittatus).

Stable isotope analyses, specifically δ13 C and δ15 N, are useful tools increasingly used to understand ecosystem function, food web structures, and consumer diets. Although the iconic tigerfish Hydrocynus vittatus is regarded as an apex predator in southern African freshwater systems, little information is available regarding their feeding behavior and how this may change with growth or differ between ecosystems, with most information stemming from stomach content analyses (SCA). The aim of the present study was to address this lack of information through a baseline study of the diet of large and small tigerfish in various lentic and lotic ecosystems in South Africa using stable isotope methods. Fish and various food web components and food sources were collected from two river and two lake ecosystems in South Africa. The δ13 C and δ15 N values for all samples were determined and multivariate analyses and Bayesian analytical techniques applied to determine the feeding ecology of H. vittatus and how this may differ with size and habitat type. Analyses revealed a substantial difference in the type and abundance of food sources contributing to the diet of H. vittatus between ecosystems, most prominently between the lotic systems, where less dietary specialization was observed, and lentic systems where more specialization was observed. Furthermore, there was a distinct difference in diet between small and large tigerfish, especially in the lotic system, indicating an ontogenetic diet shift as tigerfish grow and further supporting previous SCA studies. This is the first study of its kind on the African continent for H. vittatus and the findings illustrate the value of stable isotope analysis in providing in-depth information into the feeding ecology of consumers and how this may differ between size classes and habitat types.

Feeding ecology of Ellochelon vaigiensis (Quoy & Gaimard, 1825) living in the Mekong Delta, Vietnam.

Ellochelon vaigiensis (squaretail mullet) adapts to a wide salt spectrum, grows quickly and is easy to raise with other species, so it is the object of attention in aquaculture. Information on the biology and ecology of the species, diet, in particular, is still scattered. Here, we explore the feeding habit, feeding intensity, and food composition of the squaretail mullet. A total of 942 fish (526 males and 416 females) were collected from November 2020 to October 2021 at four coastal sites in the Mekong Delta, Vietnam. The squaretail mullet is an algi-omnivorous fish, as their relative gut length (1.81) falls into the range 1-3, and the diet is mostly based on algae. The feeding intensity is high due to the high value of the fullness index (4.39 ± 0.08%). The fullness index did not vary by sampling site and month, while RGL and FI changed depending on sex. Bacillariophyta (49.13%), detritus derived from organic matter (30.37%), and Cyanophyta (18.39%) are the dominant food items in the diet composition of E. vaigiensis, in which detritus is the most important food with the highest IRI index. Besides, Euglenophyta (1.00%), Chlorophyta (0.95%), Paramecium (0.06%), Copepoda (0.04%), Rotatoria (0.03%), Polychaeta (0.02%), and Cladocera (0.01%) are also recorded and ranked based on their biovolume. Some differences in diet composition are observed between immature and mature at different seasons and their interactions. Our results increase the knowledge about the feeding ecology of squaretail mullet and can help the sustainable management of this commercially important fish species.

The present status, distribution, demography, and diet of the Dahl's Jird / Status atual, distribuição, demografia e dieta do Jird de Dahl

Meriones dahli (Shidlovsky, 1962) was previously accepted to be a subspecies of M. meridianus (Pallas, 1773). However, it was later suggested that they are geographically isolated from each other. Although hybridological studies and differences in certain external characteristics support the idea that M. dahli is a separate species, there are still doubts on its species status, and the exact range of its distribution is not known. In this paper, we provide some taxonomic information about the species, and compare these with the information given in previous studies. We argue that some differences exist among Armenian population regarding external measurements. Recent studies indicate that M. dahli is currently only distributed in Turkey, as an endemic mammal species. We provide predictions about the distribution of M. dahli, and report the estimated population size to its maximum value. Food preference studies for this species, conducted under laboratory conditions, are also introduced for the first time. We discuss the ecological data obtained from field studies, and emphasize that the habitat of M. dahli is about to disappear. Consequently, the protection status of this species should urgently be changed to the CR category and conservation studies must be carried out immediately.

Meriones dahli (Shidlovsky, 1962) foi previamente aceito como uma subespécie de M. meridianus (Pallas, 1773). No entanto, mais tarde, foi sugerido que eles estão geograficamente isolados um do outro. Embora estudos hibridológicos e diferenças em certas características externas apoiem a ideia de que M. dahli é uma espécie separada, ainda há dúvidas sobre o status de sua espécie, e a extensão exata de sua distribuição não é conhecida. Neste artigo, fornecemos algumas informações taxonômicas sobre as espécies e as comparamos com as informações fornecidas em estudos anteriores. Argumentamos que existem algumas diferenças entre a espécie armênia em relação às medidas externas. Estudos recentes indicam que M. dahli está atualmente distribuído apenas na Turquia como uma espécie endêmica de mamífero. Fornecemos previsões sobre a distribuição de M. dahli e relatamos o tamanho estimado da população em seu valor máximo. Estudos de preferência alimentar para essa espécie, conduzidos em condições de laboratório, também são introduzidos pela primeira vez. Discutimos sobre os dados ecológicos obtidos em estudos de campo e enfatizamos que o habitat de M. dahli está prestes a desaparecer. Consequentemente, o status de proteção dessa espécie deve ser alterado com urgência para a categoria CR, e estudos de conservação devem ser realizados imediatamente.

The present status, distribution, demography, and diet of the Dahl's Jird / Status atual, distribuição, demografia e dieta do Jird de Dahl

Meriones dahli (Shidlovsky, 1962) was previously accepted to be a subspecies of M. meridianus (Pallas, 1773). However, it was later suggested that they are geographically isolated from each other. Although hybridological studies and differences in certain external characteristics support the idea that M. dahli is a separate species, there are still doubts on its species status, and the exact range of its distribution is not known. In this paper, we provide some taxonomic information about the species, and compare these with the information given in previous studies. We argue that some differences exist among Armenian population regarding external measurements. Recent studies indicate that M. dahli is currently only distributed in Turkey, as an endemic mammal species. We provide predictions about the distribution of M. dahli, and report the estimated population size to its maximum value. Food preference studies for this species, conducted under laboratory conditions, are also introduced for the first time. We discuss the ecological data obtained from field studies, and emphasize that the habitat of M. dahli is about to disappear. Consequently, the protection status of this species should urgently be changed to the CR category and conservation studies must be carried out immediately.

Meriones dahli (Shidlovsky, 1962) foi previamente aceito como uma subespécie de M. meridianus (Pallas, 1773). No entanto, mais tarde, foi sugerido que eles estão geograficamente isolados um do outro. Embora estudos hibridológicos e diferenças em certas características externas apoiem a ideia de que M. dahli é uma espécie separada, ainda há dúvidas sobre o status de sua espécie, e a extensão exata de sua distribuição não é conhecida. Neste artigo, fornecemos algumas informações taxonômicas sobre as espécies e as comparamos com as informações fornecidas em estudos anteriores. Argumentamos que existem algumas diferenças entre a espécie armênia em relação às medidas externas. Estudos recentes indicam que M. dahli está atualmente distribuído apenas na Turquia como uma espécie endêmica de mamífero. Fornecemos previsões sobre a distribuição de M. dahli e relatamos o tamanho estimado da população em seu valor máximo. Estudos de preferência alimentar para essa espécie, conduzidos em condições de laboratório, também são introduzidos pela primeira vez. Discutimos sobre os dados ecológicos obtidos em estudos de campo e enfatizamos que o habitat de M. dahli está prestes a desaparecer. Consequentemente, o status de proteção dessa espécie deve ser alterado com urgência para a categoria CR, e estudos de conservação devem ser realizados imediatamente.

The present status, distribution, demography, and diet of the Dahls Jird

Abstract Meriones dahli (Shidlovsky, 1962) was previously accepted to be a subspecies of M. meridianus (Pallas, 1773). However, it was later suggested that they are geographically isolated from each other. Although hybridological studies and differences in certain external characteristics support the idea that M. dahli is a separate species, there are still doubts on its species status, and the exact range of its distribution is not known. In this paper, we provide some taxonomic information about the species, and compare these with the information given in previous studies. We argue that some differences exist among Armenian population regarding external measurements. Recent studies indicate that M. dahli is currently only distributed in Turkey, as an endemic mammal species. We provide predictions about the distribution of M. dahli, and report the estimated population size to its maximum value. Food preference studies for this species, conducted under laboratory conditions, are also introduced for the first time. We discuss the ecological data obtained from field studies, and emphasize that the habitat of M. dahli is about to disappear. Consequently, the protection status of this species should urgently be changed to the CR category and conservation studies must be carried out immediately.

Resumo Meriones dahli (Shidlovsky, 1962) foi previamente aceito como uma subespécie de M. meridianus (Pallas, 1773). No entanto, mais tarde, foi sugerido que eles estão geograficamente isolados um do outro. Embora estudos hibridológicos e diferenças em certas características externas apoiem a ideia de que M. dahli é uma espécie separada, ainda há dúvidas sobre o status de sua espécie, e a extensão exata de sua distribuição não é conhecida. Neste artigo, fornecemos algumas informações taxonômicas sobre as espécies e as comparamos com as informações fornecidas em estudos anteriores. Argumentamos que existem algumas diferenças entre a espécie armênia em relação às medidas externas. Estudos recentes indicam que M. dahli está atualmente distribuído apenas na Turquia como uma espécie endêmica de mamífero. Fornecemos previsões sobre a distribuição de M. dahli e relatamos o tamanho estimado da população em seu valor máximo. Estudos de preferência alimentar para essa espécie, conduzidos em condições de laboratório, também são introduzidos pela primeira vez. Discutimos sobre os dados ecológicos obtidos em estudos de campo e enfatizamos que o habitat de M. dahli está prestes a desaparecer. Consequentemente, o status de proteção dessa espécie deve ser alterado com urgência para a categoria CR, e estudos de conservação devem ser realizados imediatamente.

Feeding alters the preferred body temperature of Cururu toads, Rhinella diptycha (Anura, Bufonidae).

Ectothermic organisms depend primarily on external heat sources and behavioural adjustments to regulate body temperature. Under controlled conditions, in a thermal gradient, body temperature often clusters around a more or less defined range of preferred body temperatures (Tpref). However, Tpref may be modified in response to environmental parameters and/or physiological state. For example, meal ingestion is sometimes followed by a post-prandial thermophilic response leading to a transient increment in Tpref. Although thought to optimize digestive processes, its occurrence, magnitude, and possible determinants remains scarcely documented for anuran amphibians. Herein, we investigated whether the Cururu toad, Rhinella diptycha, exhibits a post-prandial thermophilic response by monitoring the body temperature of fasting and fed toads while they were maintained in a thermal gradient. We found that the toads' Tpref increased by about 13% from day 2 to 4 after feeding, in comparison with the Tpref recorded under fasting. Also, fed animals exhibited a broader range for Tpref at days 2 and 3 post-prandial, which reflects a greater level of locomotor activity compared to fasting individuals. We conclude that R. diptycha is capable to exhibit a post-prandial thermophilic response under the controlled conditions of a thermal gradient. Although this thermoregulatory adjustment is thought to optimize meal digestion yielding important energetic and ecological benefits, its occurrence in anuran amphibians in nature remains uncertain.

A new species of king cricket Glaphyrosoma Brunner von Wattenwyl, 1888 (Orthoptera: Anostostomatidae: Glaphyrosomatini) from Costa Rica with behavioral observations.

A new king cricket species Glaphyrosoma stephanosoltis sp. nov. (Orthoptera: Anostostomatidae: Glaphyrosomatini) from mid-elevation tropical rainforests of Costa Rica is described. This new species represents the southernmost distribution of the genus Glaphyrosoma Brunner von Wattenwyl, 1888, which is widely distributed throughout Mexico, Guatemala, and Honduras. Biology of the new species is briefly described.

Flexibility is everything: prey capture throughout the seasonal habitat switches in the smooth newt Lissotriton vulgaris.

Transitions between aquatic and terrestrial habitats are significant steps in vertebrate evolution. Due to the different biophysical demands on the whole organism in water and air, such transitions require major changes of many physiological functions, including feeding. Accordingly, the capability to modulate the pre-programmed chain of prey-capture movements might be essential to maintain performance in a new environment. Newts are of special interest in this regard as they show a multiphasic lifestyle where adults change seasonally between an aquatic and a terrestrial stage. For instance, the Alpine newt is capable of using tongue prehension to feed on land only when in the terrestrial stage, but still manages to suction feed if immersed whilst in terrestrial stage. During the aquatic stage, terrestrial feeding always involved grasping prey by the jaws. Here, we show that this seasonal shift in feeding behavior is also present in a species with a shorter terrestrial stage, the smooth newt Lissotriton vulgaris. Behavioral variability increases when animals change from aquatic to terrestrial strikes in the aquatic stage, but prey-capture movements seem to be generally well-coordinated across the feeding modes. Only suction feeding in the terrestrial stage was seldom performed and appeared uncoordinated. Our results indicate that newts exhibit a high degree of seasonal flexibility of the prey-capture behavior. The similarity between movement patterns of suction feeding and terrestrial feeding suggests that only relatively subtle neuromotoric adjustments to the ancestral, suction-feeding motor program are required to successfully feed in the new environment.

Changes in Esophageal Gland Activity During the Life Cycle of Nacobbus aberrans (Nemata: Pratylenchidae).

Electron and light microscopy were used to study the dorsal gland (DG) and the two subventral glands (SvG) of seven developmental phases of Nacobbus aberrans: pre-parasitic second-stage juveniles (J2), parasitic J2, third- (J3) and fourth- (J4) stages, migratory females, young sedentary females, and mature sedentary females. In each developmental phase the level of esophageal gland activity, was estimated by the abundance of organelles associated with secretory pathways, including endoplasmic reticulum, ribosomes, Golgi, multivesicular bodies, and secretory granules. All esophageal glands were metabolically active in all J2 examined, although only in parasitic J2 were there numerous secretory granules in the esophageal gland extensions and ampullae. No evidence of secretory activity was observed in the esophageal glands of the coiled and relatively inactive J3 and J4, nor in migratory females; these stages apparently do not feed. Observations suggest that reserves stored by J2 sustain three ecdyses and the migratory female's search for a feeding site and induction of a syncytium. Feeding activity is resumed in young and mature sedentary females, in which the DG is highly active and enlarged. The SvG are metabolically active, but with little synthesis of secretory granules, suggesting that in sedentary females the SvG may have physiological roles other than digestion.