Semi-aquatic Animals Research Articles

First photon-counting detector computed tomography in the living crocodile: a 3D-Imaging study with special reference to amphibious hearing

BackgroundCrocodiles are semi-aquatic animals well adapted to hear both on land and under water. Currently, there is limited information on how their amphibious hearing is accomplished. Here, we describe, for the first time, the ear anatomy in the living crocodile using photon-counting detector computed tomography (PCD-CT) and 3D rendering. We speculate on how crocodiles, despite their closed ear canals, can use tympanic hearing in water that also provides directional hearing.Material and MethodsA Cuban crocodile (Crocodylus rhombifer) underwent photon-counting detector computed tomography (PCD-CT), under anesthesia and spontaneous respiration. In addition two seven-month-old C. rhombifer and a juvenile Morelet´s crocodile (Crocodylus moreletii) underwent micro-computed tomography (µCT) and endoscopy. One adult Cuviérs dwarf caiman (Paleosuchus palpebrosus) was micro-dissected and video-recorded. Aeration, earflap, and middle ear morphology were evaluated and compared after 3D modeling.Results and DiscussionPCD-CT and µCT with 3D rendering and segmentation demonstrated the anatomy of the external and middle ears with high resolution in both living and expired crocodiles. Based on the findings and comparative examinations, we suggest that the superior earflap, by modulating the meatal recess together with local bone conduction, may implement tympanic hearing in submerged crocodiles, including directional hearing.

Physiological and behavioral responses of northern elephant seals (Mirounga angustirostris) to global change among three northern California rookeries

The California coast provides a unique study system for investigating the effects of warming and habitat quality on the thermoregulatory capacity of the northern elephant seal (NES). In California, island rookeries such as the offshore site at the Farallon Islands National Wildlife Refuge are experiencing habitat loss and reduced suitable haul-out surfaces due to erosion from storm events. Extreme weather events are increasing in frequency and severity with global change. Semi-aquatic animals face a unique thermal challenge. They possess adaptations to conserve heat when immersed in cold water during deep dives but must compensate for such heat-conserving properties of their physiology when transitioning to heat exposure on land. Therefore, these animals must precisely thermoregulate with physiological and behavioral adjustments across a broad thermal range. We investigated how environmental variables affect seal thermoregulation at three northern California rookeries, the southeast Farallon Island (SEFI), Point Reyes National Seashore (PORE) and Año Nuevo State Park (ANSP). Infrared thermography was used to determine seal skin surface temperature and weather data was collected at each site. We found that average surface temperature increases with solar radiation, maximum surface temperature decreases with increasing wind speed, and thermal window area percentage decreases with relative humidity and increases with ambient temperature. Climatic variation may present physiological and behavioral challenges for marine mammals that experience significant life-history stages on land. Such ongoing findings will be fundamental in predicting climate change vulnerabilities and will be critical in mitigating the impacts of anthropogenic warming and promoting resilience in these populations. Carol Baird Graduate Student Award for Field Research; The Neubacher Fund for Marine Science at Point Reyes National Seashore. This is the full abstract presented at the American Physiology Summit 2023 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

An Overview on Lutra lutra

European Otter (Lutra lutra), is an aquatic and semi-aquatic animal from the carnivores and sub-family from Lutrinae of the Mustelidea family that lives alongside rivers and wetlands. Lutra lutra is an indicator species, and its loss somehow threatens human life, because one species is the head of the food chain and its loss is a sign of environmental degradation of other species. It has good distribution in Iran and the world, including Eurasia and North Africa. Lutra lutra has appearance characteristics such as a large body, cylindrical shape, a wide snout with long and thick mustaches, small ears and eyes, the tail is long and tubular, which at the base becomes wide and thick, the hands and feet are short and there is a curtain among the fingers, the hair is soft and dense, brown to brownish, under the chin and white throat. In recent years, widespread deaths have occurred in several aquatic mammal populations, which has reduced the population of Lutra lutra compared to the past. Due to various reasons such as loss of prey, indiscriminate hunting, contamination caused by agricultural pesticides, especially chlorine toxins, industrial pollution, and floods, its population is rapidly declining and has been totally destroyed in some areas.

Characteristics of the Labi-labi Habitat (Amyda cartilaginea) in the Tawun Ngawi Tourism Park

Labi-labi is a type of soft shell turtle that lives in fresh water. Labi-Labi is also a semi-aquatic animal that often spends its life in the waters. The population of turtles in the wild is widely used by the community for sale or consumption. Therefore, over time, people made conservation efforts to prevent the extinction of the turtles. One of the turtle conservation is the Tawun Ngawi Tourism Park. This tourist park is one of the conservation of the turtles and also the artificial habitat of the turtles. As a place for the conservation of turtles, of course the Tawun Tourism Park must be in accordance with the natural habitat of the turtles. The existence of this study aims to determine the characteristics and suitability level of the artificial habitat in the Tawun Tourism Park area. Then the method of conducting this research was carried out by direct observation by measuring the existing biotic and abiotic parameters and analyzed according to the suitability of their natural habitat. So that the result is that the artificial habitat in the Tawun Ngawi Tourism Park has characteristics that are in accordance with the natural habitat of the turtles. Then the hope for further research needs to be explored further regarding the habitat characteristics of the labi-labi in the wild.

Ceratozetidae (Acari: Oribatida) from lower Miocene mexican amber, including a new species of Trichoribates

Trichoribates roynortoni Ojeda and Rivas sp. n. Is described based on one adult specimen preserved in estuarine stratified lower Miocene amber from the Campo La Granja mines, La Quinta Formation, Chiapas Mexico, which includes mostly estuarine aquatic and semiaquatic animals, but also an important amount of soil arthropods. This taxon is the first record for the Ceratozetidae family (Acari: Sarcoptiformes: Oribatida) and represents an addition to the few Acari reported for the Chiapas amber.

Freshwater Reservoir, Ecological Traps and Source-Sink Dynamics

Odonata are biodiversity indicators that adequately represent many aquatic and semi-aquatic animal species. We recorded over two field seasons a rich lentic community of Odonata (18 species) in a large artificial freshwater reservoir (ca. 55 ha) built 40 years ago. The release of water from the dam in summer for crop irrigation leads to the desiccation of large parts of the reservoir, which prevents the reproduction of half of the species of this Odonata community. We identify two adaptations that allow eight species to cope with desiccation, i.e., a precocious breeding period allowing the emergence of adults before the retreat of water, or a delayed adult emergence due to egg diapause from oviposition to the end of winter. The reservoir acts thus as an ecological trap for individuals of 10 species that developed elsewhere and were attracted to the site without successfully breeding there. As consequence of the local population extinction at each generation, the presence of individuals of these 10 species at the reservoir depends on source-sink population dynamics in the landscape. In the context of global warming that encourages the creation of artificial freshwater reservoirs, the multiplication of such sinks could threaten the persistence in the landscape of species maladapted to desiccation.

First report of molecular taxonomic analyses of European beaver metazoan parasites from Hungary

European beaver (Castor fiber L. 1758) is the biggest rodent species living in Europe. Beavers are semi-aquatic animals; they are defecating directly into the water; thus, they have an important role in spreading parasites related to water (e.g., protozoa and flukes). The first specimens of this once extinct rodent species in Hungary turned up in Szigetköz (upper flow of the Hungarian Danube) in 1991 dispersed from Austria. The reintroduction to Hungary started in 1996, and the population slowly increased in number up to around 4000 individuals, but the knowledge about their parasites is lacking. This is the first report on the metazoan parasites of beavers in Hungary and their molecular taxonomy. In the 5-year study, 47 beavers were trapped in four locations and euthanized with permission. Three different metazoan parasites were collected: larvae and adults of Platypsyllus castoris beetles, nymphs and adults of Schizocarpus sp. mites and eggs and adults of Stichorchis subtriquetrus flukes. From these three parasite species, molecular taxonomic studies were also carried out. The low number of metazoan parasites species detected in Hungarian beavers compared to other European countries (e.g., Poland) might be attributed to host population bottleneck effect during reintroduction. As parasites represent a significant component of the biodiversity and ecosystem, the conservation efforts should focus not only on host species but also on their parasites.

Soil dwelling springtails are resilient to extreme drought in soil, but their reproduction is highly sensitive to small decreases in soil water potential

Understanding the physiology and ecology of springtails and their responses to environmental conditions in the soil is important for many aspects of soil ecology. Many springtails spend most of their lives in the soil where humidity is high, and several euedaphic species are considered semi-aquatic animals. Climate models predict that summer soil moisture in many regions will decrease in the future, and our aim with this laboratory study was to investigate the importance of soil water potentials in the range between field capacity to the wilting point on the survival, growth and reproduction of the euedaphic springtail, Folsomia candida Willem. Our results show that reproduction was, by far, the most sensitive life-history trait. Reproduction stopped already at very modest soil water potentials (-15 kPa), which did not influence body water content or growth. These results suggest that recruitment in populations of F. candida is restricted to periods where soil moisture is high. Body growth and activities of juveniles and adults, however, may continue in moderately dry soil until the soil water potential reaches ca. −100 kPa. Should severe drought occur, normal body functions are paused, but surviving adults and juvenile individuals would contribute to the resilience of this species at low soil moisture. We discuss the implications of drought for the ecological functions of springtails.

A non-invasive, DNA-based method for beaver species identification in Finland

For the ability to control an invasive species and to protect an ecologically similar native species it is essential to map the exact distributions of both species. This is difficult if the species are so morphologically similar that their identification in the field is almost impossible. In Finland, the invasive North American beaver Castor canadensis is spreading towards the range of the native Eurasian beaver Castor fiber and at present, these species are partly sympatric. Effective management of these morphologically similar species requires an efficient method for species identification, ideally one that is non-invasive. Non-invasive genetic methods are used in a wide variety of wildlife species, for example in the research of large carnivores. Feces are a good source of DNA for terrestrial animals, but for the semi-aquatic animals like beavers, feces are not the best option. However, environmental DNA (eDNA) has been successfully used to detect species non-invasively in aquatic and terrestrial environments. We developed a non-invasive, eDNA-based method to map the distribution of the beaver species in Finland and to investigate within-species genetic diversity. The eDNA was obtained from the feed remains (wood chips) from beaver forage sites. With the help of Citizen science, wood chip samples were collected from different parts of Finland. We used our eDNA method to identify the ranges of both beaver species. Additionally, the presence of Eurasian beavers in south-east Finland was proven for the first time. Our non-invasive eDNA method is an effective way to accurately identify the ranges of both beaver species and will allow for the control of the invasive North American beaver and conservation of the native Eurasian beaver in Finland.

First report on parasites of European beavers in the Slovak Republic.

European beaver (Castor fiber L. 1758) is the biggest rodent living in Europe. It is a semi-aquatic animal known for building dams and burrows. European beaver is a potential host for a wide range of parasites and other infectious diseases. In Slovakia, there is an increasing number of beavers but the data about their parasitic fauna are missing. Our work is the first documentation about the beaver's parasitofauna in Slovakia. In a 1-year study, we collected and examined 19 beaver fecal samples from the vicinity of beaver burrows inhabiting three particular localities at the Danube, Topľa, and Laborec rivers in Slovakia. In these fecal samples, 4 different species of intestinal endoparasites were detected as follows: oocysts of Cryptosporidium, cysts of Giardia, eggs of Stichorchis subtriquetrus, and eggs and larvae of Travassosius rufus. Parasites were confirmed only in samples collected at river Topľa. Based on our results, we can conclude that European beaver can be an important source of parasitic contamination of surface waters especially in the localities shared by people.

Mortality dynamics and fossilisation pathways of a new metoposaurid-dominated multitaxic bonebed from India: a window into the Late Triassic vertebrate palaeoecosystem

ABSTRACT A new bonebed recovered from the Late Triassic of India contains various macro- and microfossils, unionid bivalves and coprolites. The macrofossils include more than 700 identifiable skeletal specimens of 27 metoposaurid, four phytosaur and two rhynchosaur individuals whereas the microfossils comprise about 500 isolated teeth of varied chondrichthyans, dipnoans, actinopterygians, archosauriforms, and several non-mammalian cynodonts. The bonebed is a monodominant, multitaxic, parautochthonous, time-averaged, attritional assemblage. The Tiki floodplain was populated by highly diverse animal communities occupying terrestrial, semi-aquatic and aquatic realms, where scavenging and/or predation were common. Two distinct biostratinomic modes deduced are – (i), natural death, decomposition, and differential pre-burial modifications of the large terrestrial and semi-aquatic animals, and (ii) breaching of banks during flooding events, mass death, and high energy deposition of sediment load including various aquatic fishes and unionids. Similar REE patterns of a representative sample set of bone specimens and their encasing matrices suggest same diagenetic condition and a single burial event. The MREE enrichment, cerium and uranium content indicate reducing burial microenvironment for the studied fossil specimens. The Late Triassic scenario comprised highly dynamic animal communities that had different mortality dynamics and fossilisation pathways depending on the habitats and palaeobehaviour of the animals.

Correlation of Bone Density in Semi‐Aquatic and Aquatic Animals with Ecological and Dietary Specializations

A successful transition from a terrestrial to an aquatic environment requires the acquisition of unique adaptations that fit the distinct habitat. Pachyosteosclerosis is a combination of pachyostosis (thickening of cortical bone) and osteosclerosis (thickening of medullary bone). This accumulation of bone increases the density and weight of the animals that exhibit these characters. Pachyosteosclerosis is commonly found in aquatic and semiaquatic animals such as sirenians (sea cows), odobenids (walruses), otariids (sea lions), phocids (true seals) and cetaceans (whales). Increased bone density occurred early in the transition from a terrestrial to a marine environment, present before many of the other morphological characters such as flukes, flippers and fins and behavioral characters such as oscillatory swimming associated with aquatic life appear. Pachyosteosclerosis helps to counteract buoyancy, allowing taxa to remain submerged longer in order to feed while expending little energy. This is clearly demonstrated in sirenians, which are known to feed on sea grasses in shallow waters near the coastline. In most other aquatic mammals, such as modern cetaceans, pachyosteosclerosis is followed by an osteoporosis‐like bone lightening for increased swimming speeds that allows for the active hunting of fast‐moving prey. Pinnipeds live in a wide range of habitats (from cold to warm waters, from marine to fresh water) and demonstrate varying feeding mechanisms, ranging from filter feeding to bottom feeding to catching fast prey. Increased bone density is seen in multiple species of seals in different geological ages from the Miocene (~ 23mya) to present. The morphological and ecological significance for seals with thicker bones is that they swim slower and hunt in shallower water, while seals with lighter bones swim faster and hunt fast moving prey. Bone microstructural disparity allows different species of seals to successfully live in sympatric habitats due to their ecological and dietary specializations. Bone density is one vital character that can be used to predict the specific ecological niche and feeding preference for pinnipeds. Some early hominids, such as Homo erectus, have been shown to have increased density in the bones also. These heavier, thicker bones would make it easier for early Homo to hunt in coastal waters for littoral food sources and would compensate for the lack of stability from bipedalism.Support or Funding InformationFunding Provided by Torres Advanced Enterprise Solutions LLC and Just‐Julian Fellowship

On the Strength of Hair across Species

Summary The hair of mammals varies in diameter across species from ∼60 μm in humans to over ∼400 μm in giraffes and elephants. Here, we establish that the tensile strength of hair generally decreases with increasing diameter. Although there is a commonality in the morphology of the hair in such differing species as they all possess a cortex surrounded by cuticles, there are also significant differences in the hierarchical structure that contribute to the observed differences in strength. In this work, the internal structure of the hair from different species is examined, with some unique peculiarities in javelina and capybara hair uncovered. The dimensional dependence of hair strength is compared using Weibull predictions. The good correlation of the strength of hair using such Weibull analysis suggests that the failure strength is dictated by the probability distribution of flaws within the cortex.

“Animal style” before the pharaohs: Egyptian predynastic rock-art and handicraft representationism as a palaeogeographical source (return to the problem)

The prehistoric petroglyphs of large moisture-loving and semi-aquatic animals (such as elephants, giraffes, hippos, and crocodiles) in the wadis of the Egyptian Eastern Desert have been considered by some scholars of the past as one of the most important evidence, which supported the theory that the North African climates in the Antiquity were humid in comparison to that of the present day. Modern scholars, however, generally deny the actual existence of this fauna and interpret symbolically the rock-drawings found far away from the Nile. The author who has previously suggested that in the period between the 7th and the 4th millennium BC there was a huge lake situated between the present Asyut and Fayum, uses the petroglyphs found in the Eastern Desert as a source, which helps him to reconstruct the climate of the Egyptian Nile basin as well as some hydrological issues at the period of the mid-Holocene.

First Insights Into Bacterial Gastrointestinal Tract Communities of the Eurasian Beaver (Castor fiber).

The Eurasian or European beaver (Castor fiber) is the second-largest living rodent after the capybara. It is a semi-aquatic animal known for building dams and lodges. They strictly feed on lignocellulose-rich plants and correspondingly harbor cellulolytic microbial communities in their digestive tract. In this study, the bacterial community composition, diversity, and functional profile of different gut compartments ranging from stomach to colon have been explored. A total of 277 bacterial operational taxonomic units (OTUs) at species level were obtained from the gut systems of two males (juvenile and subadult) and one subadult female beaver. In general, cecum and colon are dominated by Firmicutes and Actinobacteria. High abundance of Bacteroidetes was observed only in male juvenile beaver cecum and colon, suggesting that the bacterial composition changes with age. Within the cecum and colon, members of known cellulase-producing bacterial taxa including the families Ruminococcaceae, Lachnospiraceae, and Clostridiaceae 1 were detected. The presence of putative genes encoding cellulolytic and carbohydrate-degrading enzymes indicated also the degradation of recalcitrant plant material in both gut compartments. The bacterial community in the gut systems of the Eurasian beaver differed from that of the North American beaver. Higher abundance of Actinobacteria and lower abundances of Bacteroidetes were recorded in the Eurasian beaver. Similar differences were obtained to bacterial communities of termites and herbivorous animals such as bovine. The data presented in this study provides the first insight into bacterial communities in the gut system of the Eurasian beaver.

MORPHOMETRIC PARAMETERS OF ERYTHROCYTES IN SEVERAL RODENTIA SPECIES

Red blood cells (RBC) play a leading role in the blood gas transport function and oxygen supply to tissues, and the number and size of RBC have a decisive role in tissue oxygenation. The size of erythrocyte varies significantly among animal species, depending on a number of factors. Data on the effect of various factors (living conditions, lifestyle, systematic affiliation, body weight) on the size of RBC are contradictory. The choice of mammals belonging to the Rodentia order was dictated by their very extensive distribution range and ecological features. A comparative study of the morphometric parameters (surface area and diameter) of RBC was performed for 11 Rodentia species: European beaver ( Castor fiber ), Canadian beaver ( C. canadensis ), nutria ( Myocastor coypus ), muskrat ( Ondatra zibethicus ), rat ( Rattus norvegicus ), chinchilla ( Chinchilla lanigera ), red squirrel ( Sciurus vulgaris ), bank vole ( Myodes glareolus ), European water vole ( Arvicola amphibius ), laboratory mouse ( Mus musculus ) and Syrian hamster ( Mesocricetus auratus ). A direct dependence of the size of erythrocytes on body weight was established, which agrees with the data reported by other researchers. The maximum size of RBC was noted in C. canadensis and C. fiber . Besides, large erythrocytes were detected in all the studied semiaquatic animals. The surface area of erythrocytes in terrestrial rodent species decreased in the following order: C. lanigera – R. norvegicus – S. vulgaris – M. musculus – M. glareolus. The influence of physiological (weight, sex, longevity) and ecological factors (food habits and habitat) on the morphometric parameters of erythrocytes was revealed, while systematic affiliation did not affect cell size.

THE CURRENT SITUATION ANALYSIS AT THE PARASITE FAUNA OF SEMI-AQUATIC CARNIVORES OF THE WEASEL FAMILY IN THE CENTRAL REGION OF THE RUSSIAN FEDERATION

Most members of the Mustelidae family living in the Central Non-Black Earth Region of Russia are the objects of sport and commercial hunting. Some of them are bred in fur farms (mink, polecat) and kept at home as decorative animals. The close contact of a person with various members of the family of mustelids, which increase with the development of urbanization processes, makes significant role of mustelids as sources of dangerous invasions for humans and animals (trichinosis, echinococcosis, etc.). We examined 48 ferrets, 107 American minks, 25 European minks, and 11 otters in order to determine the species composition of animal parasites, in the period 2000–2018. They were examined according to methods commonly used in parasitology about muscle tissue, internal organs, and thoracic and abdominal cavity. Animals for research were obtained from hunters from the Central region of the Russian Federation. Studies have shown that ferrets are invased with 8 species of parasites belonging to two classes: Trematoda (3 species) and Nematoda (5 species). The parasitic fauna of the minks was represented by 15 species of worms: Trematoda (2 species), Cestoda (1 species), Nematoda (12 species). The American mink is infested with 14 helminth species and the European mink with 11 species. Otters were infested with 2 classes of parasites: Trematoda (1 species) and Nematoda (1 species). We explain the high contamination of ferrets and minks of E. perfoliatus by the constant presence of animals at the reservoirs where the intermediate owners of helminths (fish) live. Also, a significant proportion in the diet of many species of weasels are tailless amphibians (frogs), which explains the infection of semi-aquatic animals with an unusual species of trematodes Alaria alata (larvae).

Jumping dynamics of aquatic animals.

Jumping out of water is a phenomenon exhibited by a variety of aquatic and semi-aquatic animals. Yet, there is no common groundwork that clarifies the physical constraints required to jump out of water. In this study, we elucidate the physical conditions required for an animal to jump out of water. More than 100 jumps are analysed over five taxonomic groups. By balancing the power produced by animals with drag-induced dissipation, we expect that maximum jumping height, H, scales with body length, L, as H/ L ∼ L-1/3 ∼ Fr2, where the Froude number, Fr, is a ratio of inertia to gravity. To identify jumping regimes, simplified experiments are conducted by shooting axisymmetric bodies through the water surface. Here, we see a transition in which partial exits scale as H/ L ∼ Fr and complete exits scale as H/ L ∼ Fr2. A bioinspired robotic flapping mechanism was designed to mimic the fast motion of impulsive jumping animals. When exiting water, the robot carries a large volume of fluid referred to as an entrained mass. A theoretical model is developed to predict the jumping height of various water-exiting bodies, which shows that the mass of the entrained fluid relative to the mass of the body limits the maximum jumping height. We conclude that the lack of entrained fluid allows animals to reach extraordinary heights compared to our water-exiting robots.

How Does the Japanese Water Shrew Chimarrogale platycephalus Cross the Concrete Walls of Check Dams?

The concrete walls of check dams are considered a physical barrier for aquatic and semiaquatic animals that inhabit mountain streams. Traveling behaviors around concrete check dams by the Japanese water shrew Chimarrogale platycephalus, a semi-aquatic mammal, were directly observed via radio-tracking in Kamikoshi Stream in central Honshu, Japan. Traveling behaviors were mainly observed on the wet concrete walls and in the backfill sediments of check dams. Chimarrogale platycephalus generally crossed the wall directly, and route selection was affected by the traveling direction of C. platycephalus and the surface wetness of the concrete wall. Detouring behavior around the concrete walls was observed visually only once during the survey period. Using modulation of sounds on a FM receiver, the movements of C. platycephalus were detected in their hiding places along the stream. Some individuals frequently ceased movement within the backfill sediments. Our results suggest that existing concrete check dams do not prohibit the shrew's movements between upstream and downstream of the river and that backfill sediments may be utilized as resting places.

Performance of GPS units for deployment on semiaquatic animals.

Global Positioning System (GPS) technology is widely used in wildlife research to study animal movement and habitat use. In order to evaluate the quality and reliability of GPS data, the factors influencing the performance of these devices must be known, especially for semiaquatic species, because terrestrial and aquatic habitat might affect GPS performance differently. We evaluated the location error and fix success rate of three GPS receiver models in stationary tests and on a semi-aquatic mammal, the Eurasian beaver (Castor fiber). The location error during stationary tests was on average 15.7 m, and increased with increasing canopy closure, slope, and horizontal dilution of precision, potentially leading to the erroneous classification of GPS positions when studying habitat use in animals. In addition, the position of the GPS antenna (flat versus 90° tilted) affected the location error, suggesting that animal behavior affects GPS performance. The fix success rate was significantly higher during stationary tests compared to when GPS units were deployed on beavers (94% versus 86%). Further, GPS receivers did not obtain any positions underwater and underground, the latter potentially allowing the estimation of activity periods in animals that use lodges or burrows as shelter. We discuss the possibilities for data screening, the use of buffer zones along the shoreline, and combination with other data loggers to avoid the erroneous classification of GPS positions when studying habitat use.