nils-herrmann/clean_scirepeval huggingface dataset:
Ultraviolet visual sensitivity in three avian lineages: paleognaths, parrots, and passerines
Venue: Journal of Comparative Physiology A

Ultraviolet (UV) light-transmitted signals play a major role in avian foraging and communication, subserving functional roles in feeding, mate choice, egg recognition, and nestling discrimination. Sequencing functionally relevant regions of the short wavelength sensitive type 1 (SWS1) opsin gene that is responsible for modulating the extent of SWS1 UV sensitivity in birds allows predictions to be made about the visual system’s UV sensitivity in species where direct physiological or behavioral measures would be impractical or unethical. Here, we present SWS1 segment sequence data from representative species of three avian lineages for which visually based cues for foraging and communication have been investigated to varying extents. We also present a preliminary phylogenetic analysis and ancestral character state reconstructions of key spectral tuning sites along the SWS1 opsin based on our sequence data. The results suggest ubiquitous ultraviolet SWS1 sensitivity (UVS) in both paleognaths, including extinct moa (Emeidae), and parrots, including the nocturnal and flightless kakapo (Strigops habroptilus), and in most, but not all, songbird (oscine) lineages, and confirmed violet sensitivity (VS) in two suboscine families. Passerine hosts of avian brood parasites were included both UVS and VS taxa, but sensitivity did not co-vary with egg rejection behaviors. The results should stimulate future research into the functional parallels between the roles of visual signals and the genetic basis of visual sensitivity in birds and other taxa.
Cystic fibrosis transmembrane conductance regulator in the gills of the climbing perch, Anabas testudineus, is involved in both hypoosmotic regulation during seawater acclimation and active ammonia excretion during ammonia exposure
Venue: Journal of Comparative Physiology B

This study aimed to clone and sequence the cystic fibrosis transmembrane conductance regulator (cftr) from, and to determine the effects of seawater acclimation or exposure to 100 mmol l−1 NH4Cl in freshwater on its mRNA and protein expressions in, the gills of Anabas testudineus. There were 4,530 bp coding for 1,510 amino acids in the cftr cDNA sequence from A. testudineus. The branchial mRNA expression of cftr in fish kept in freshwater was low (<50 copies of transcript per ng cDNA), but significant increases were observed in fish acclimated to seawater for 1 day (92-fold) or 6 days (219-fold). Branchial Cftr expression was detected in fish acclimated to seawater but not in the freshwater control, indicating that Cl− excretion through the apical Cftr of the branchial epithelium was essential to seawater acclimation. More importantly, fish exposed to ammonia also exhibited a significant increase (12-fold) in branchial mRNA expression of cftr, with Cftr being expressed in a type of Na+/K+-ATPase-immunoreactive cells that was apparently different from the type involved in seawater acclimation. It is probable that Cl− excretion through Cftr generated a favorable electrical potential across the apical membrane to drive the excretion of $$ {\text{NH}}_{4}^{ + } $$ against a concentration gradient through a yet to be determined transporter, but it led to a slight loss of endogenous Cl−. Since ammonia exposure also resulted in significant decreases in blood pH, [HCO3−] and [total CO2] in A. testudineus, it can be deduced that active $$ {\text{NH}}_{4}^{ + } $$ excretion could also be driven by the exit of HCO3− through the apical Cftr. Furthermore, A. testudineus uniquely responded to ammonia exposure by increasing the ambient pH and decreasing the branchial bafilomycin-sensitive V-type H+-ATPase activity, which suggests that its gills might have low NH3 permeability.
‘No cost of echolocation for flying bats’ revisited
Venue: Journal of Comparative Physiology B

Echolocation is energetically costly for resting bats, but previous experiments suggested echolocation to come at no costs for flying bats. Yet, previous studies did not investigate the relationship between echolocation, flight speed, aerial manoeuvres and metabolism. We re-evaluated the ‘no-cost’ hypothesis, by quantifying the echolocation pulse rate, the number of aerial manoeuvres (landings and U-turns), and the costs of transport in the 5-g insectivorous bat Rhogeessa io (Vespertilionidae). On average, bats (n = 15) travelled at 1.76 ± 0.36 m s−1 and performed 11.2 ± 6.1 U-turns and 2.8 ± 2.9 ground landings when flying in an octagonal flight cage. Bats made more U-turns with decreasing wing loading (body weight divided by wing area). At flight, bats emitted 19.7 ± 2.7 echolocation pulses s−1 (range 15.3–25.8 pulses s−1), and metabolic rate averaged 2.84 ± 0.95 ml CO2 min−1, which was more than 16 times higher than at rest. Bats did not echolocate while not engaged in flight. Costs of transport were not related to the rate of echolocation pulse emission or the number of U-turns, but increased with increasing number of landings; probably as a consequence of slower travel speed when staying briefly on ground. Metabolic power of flight was lower than predicted for R. io under the assumption that energetic costs of echolocation call production is additive to the aerodynamic costs of flight. Results of our experiment are consistent with the notion that echolocation does not add large energetic costs to the aerodynamic power requirements of flight in bats.
HIF-1α regulation in mammalian hibernators: role of non-coding RNA in HIF-1α control during torpor in ground squirrels and bats
Venue: Journal of Comparative Physiology B

A potential role for non-coding RNAs, miR-106b and antisense hypoxia inducible transcription factor-1 (HIF-1α), in HIF-1α regulation during mammalian hibernation was investigated in two species, the thirteen-lined ground squirrel (Ictidomys tridecemlineatus) and the little brown bat (Myotis lucifugus). Both species showed differential regulation of HIF-1α during hibernation. HIF-1α protein levels increased significantly in skeletal muscle of both species when animals entered torpor, as well as in bat liver. HIF-1α mRNA levels correlated with the protein increase in bat skeletal muscle and liver but not in squirrel skeletal muscle. Antisense HIF-1α transcripts were identified in skeletal muscle of both hibernators. The expression of antisense HIF-1α was reduced in skeletal muscle of torpid bats compared with euthermic controls, suggesting that release of inhibition by the antisense RNA contributes to regulating HIF-1α translation in this tissue during torpor. The expression of miR-106b, a microRNA associated with HIF-1α regulation, also decreased during torpor in both skeletal muscle and liver of bats and in ground squirrel skeletal muscle. These data present the first evidence that non-coding RNA provides novel post-transcriptional mechanisms of HIF-1α regulation when hibernators descend into deep cold torpor, and also demonstrate that these mechanisms are conserved in two divergent mammalian orders (Rodentia and Chiroptera).
Thermoregulatory changes anticipate hibernation onset by 45 days: data from free-living arctic ground squirrels
Venue: Journal of Comparative Physiology B

Hibernation is a strategy of reducing energy expenditure, body temperature (Tb) and activity used by endotherms to escape unpredictable or seasonally reduced food availability. Despite extensive research on thermoregulatory adjustments during hibernation, less is known about transitions in thermoregulatory state, particularly under natural conditions. Laboratory studies on hibernating ground squirrels have demonstrated that thermoregulatory adjustments may occur over short intervals when animals undergo several brief, preliminary torpor bouts prior to entering multiday torpor. These short torpor bouts have been suggested to reflect a resetting of hypothalamic regions that control Tb or to precondition animals before they undergo deep, multiday torpor. Here, we examined continuous records of Tb in 240 arctic ground squirrels (Urocitellus parryii) prior to hibernation in the wild and in captivity. In free-living squirrels, Tb began to decline 45 days prior to hibernation, and average Tb had decreased 4.28 °C at the onset of torpor. Further, we found that 75 % of free-living squirrels and 35 % of captive squirrels entered bouts of multiday torpor with a single Tb decline and without previously showing short preliminary bouts. This study provides evidence that adjustments in the thermoregulatory component of hibernation begin far earlier than previously demonstrated. The gradual reduction in Tb is likely a component of the suite of metabolic and behavioral adjustments, controlled by an endogenous, circannual rhythm, that vary seasonally in hibernating ground squirrels.
Testosterone dynamics during encounter: role of emotional factors
Venue: Journal of Comparative Physiology A

This study attempts to develop a new theory to explain the varying dynamics of testosterone levels in dominant (winners) and subordinate (losers) males, both pre- and post-encounter. The crux of our new theory consists of the following four theses: (1) the strengthening of testosterone synthesis is a result of not only the existence of challenges, but also of a positive mood before an encounter that is associated with the anticipation of a victory; (2) in situations where the anticipation of victory is present but the positive mood is absent, no rise in testosterone levels will occur; (3) testosterone acts as a “pleasure” hormone and usually releases in situations where the individual achieves or anticipates possible satisfaction; (4) an increased release of testosterone to the blood not only decreases anxiety but also elevates the mood, which increases animal’s/human’s assertiveness and consequently aggressiveness.
Modulation of network pacemaker neurons by oxygen at the anaerobic threshold
Venue: Journal of Comparative Physiology A

Previous in vitro and in vivo studies showed that the frequency of rhythmic pyloric network activity in the lobster is modulated directly by oxygen partial pressure (PO2). We have extended these results by (1) increasing the period of exposure to low PO2 and by (2) testing the sensitivity of the pyloric network to changes in PO2 that are within the narrow range normally experienced by the lobster (1 to 6 kPa). We found that the pyloric network rhythm was indeed altered by changes in PO2 within the range typically observed in vivo. Furthermore, a previous study showed that the lateral pyloric constrictor motor neuron (LP) contributes to the O2 sensitivity of the pyloric network. Here, we expanded on this idea by testing the hypothesis that pyloric pacemaker neurons also contribute to pyloric O2 sensitivity. A 2-h exposure to 1 kPa PO2, which was twice the period used previously, decreased the frequency of an isolated group of pacemaker neurons, suggesting that changes in the rhythmogenic properties of these cells contribute to pyloric O2 sensitivity during long-term near-anaerobic (anaerobic threshold, 0.7–1.2 kPa) conditions.
Ants swimming in pitcher plants: kinematics of aquatic and terrestrial locomotion in Camponotus schmitzi
Venue: Journal of Comparative Physiology A

Camponotus schmitzi ants live in symbiosis with the Bornean pitcher plant Nepenthes bicalcarata. Unique among ants, the workers regularly dive and swim in the pitcher’s digestive fluid to forage for food. High-speed motion analysis revealed that C. schmitzi ants swim at the surface with all legs submerged, with an alternating tripod pattern. Compared to running, swimming involves lower stepping frequencies and larger phase delays within the legs of each tripod. Swimming ants move front and middle legs faster and keep them more extended during the power stroke than during the return stroke. Thrust estimates calculated from three-dimensional leg kinematics using a blade-element approach confirmed that forward propulsion is mainly achieved by the front and middle legs. The hind legs move much less, suggesting that they mainly serve for steering. Experiments with tethered C. schmitzi ants showed that characteristic swimming movements can be triggered by submersion in water. This reaction was absent in another Camponotus species investigated. Our study demonstrates how insects can use the same locomotory system and similar gait patterns for moving on land and in water. We discuss insect adaptations for aquatic/amphibious lifestyles and the special adaptations of C. schmitzi to living on an insect-trapping pitcher plant.
Evidence of red sensitive photoreceptors in Pygopleurus israelitus (Glaphyridae: Coleoptera) and its implications for beetle pollination in the southeast Mediterranean
Venue: Journal of Comparative Physiology A

A very well-documented case of flower-beetle interaction is the association in the Mediterranean region between red bowl-shaped flowers and beetles of the family Glaphyridae. The present study examines the visual mechanisms by which Pygopleurus israelitus (Glaphyridae: Scarabaeoidea: Coleoptera) would perceive the colors of flowers they visit by characterizing the spectral sensitivity of its photoreceptors. Our measurements revealed the presence of three types of photoreceptors, maximally sensitive in the UV, green and red areas of the spectrum. Using color vision space diagrams, we calculated the distribution of beetle-visited flower colors in the glaphyrid and honeybee color space and evaluated whether chromatic discrimination differs between the two types of pollinators. Respective color loci in the beetle color space are located on one side of the locus for green foliage background, whereas in the honeybee the flower color loci surround the locus occupied by green foliage. Our results represent the first evidence of a red sensitive photoreceptor in a flower-visiting coleopteran species, highlighting Glaphyridae as an interesting model group to study the role of pollinators in flower color evolution.
Nematocytes’ activation in Pelagia noctiluca (Cnidaria, Scyphozoa) oral arms
Venue: Journal of Comparative Physiology A

Nematocytes’ discharge is triggered to perform both defense and predation strategies in cnidarians and occurs under chemico-physical stimulation. In this study, different compounds such as amino acids and proteins (mucin, albumin, poly-l-lysine, trypsin), sugars and N-acetylate sugars (N-acetyl neuraminic acid, N-acetyl galactosamine, sucrose, glucose, agarose and trehalose), nucleotides (ATP and cAMP), were tested as chemosensitizers of nematocyte discharge in the oral arms of the scyphozoan Pelagia noctiluca, particularly abundant in the Strait of Messina (Italy). Excised oral arms were submitted to a combined chemico-physical stimulation by treatment with different compounds followed by mechanical stimulation by a non-vibrating test probe. Discharge induced by a chemico-physical stimulation was more significant than that obtained after mechanical stimulation alone. A chemosensitizing mechanism, with a dose-dependent effect, was observed after treatment with sugars, amino compounds such as glutathione, nucleotides and mucin, according to that already seen in sea anemones. Such findings suggest that, though Anthozoa and Scyphozoa exhibit different divergence times during the evolutionary process, the discharge activation exhibits common features, probably derived from their last common ancestor.
Adult neurogenesis in the brain of the Mozambique tilapia, Oreochromis mossambicus
Venue: Journal of Comparative Physiology A

Although the generation of new neurons in the adult nervous system (‘adult neurogenesis’) has been studied intensively in recent years, little is known about this phenomenon in non-mammalian vertebrates. Here, we examined the generation, migration, and differentiation of new neurons and glial cells in the Mozambique tilapia (Oreochromis mossambicus), a representative of one of the largest vertebrate taxonomic orders, the perciform fish. The vast majority of new cells in the brain are born in specific proliferation zones of the olfactory bulb; the dorsal and ventral telencephalon; the periventricular nucleus of the posterior tuberculum, optic tectum, and nucleus recessi lateralis of the diencephalon; and the valvula cerebelli, corpus cerebelli, and lobus caudalis of the cerebellum. As shown in the olfactory bulb and the lateral part of the valvula cerebelli, some of the young cells migrate from their site of origin to specific target areas. Labeling of mitotic cells with the thymidine analog 5-bromo-2′-deoxyuridine, combined with immunostaining against the neuron-specific marker protein Hu or against the astroglial marker glial fibrillary acidic protein demonstrated differentiation of the adult-born cells into both neurons and glia. Taken together, the present investigation supports the hypothesis that adult neurogenesis is an evolutionarily conserved vertebrate trait.
Molecular and physicochemical characterization of hemoglobin from the high-altitude Taiwanese brown-toothed shrew (Episoriculus fumidus)
Venue: Journal of Comparative Physiology B

Red-toothed shrews (subfamily Soricinae) exhibit the highest mass-specific rates of O2 consumption recorded among eutherian mammals, though surprisingly no data appears to be available on the functional characteristics of their hemoglobin (Hb). As a first step in addressing this shortcoming, we investigated the O2 binding characteristics of Taiwanese brown-toothed shrew (Episoriculusfumidus) Hb and its temperature and pH dependence in the absence and presence of anionic red blood cell effectors. Although comparative data regarding the intrinsic O2 affinity of other shrew species are currently unavailable, our data suggest that the sensitivity of this high-elevation endemic species’ Hb to allosteric effector molecules is similar to that of the two lowland species of white-toothed (crocidurine) shrews examined to date. The efficient exploitation of blood O2 reserves by E. fumidus appears to be achieved via synergistic modulation of O2 affinity by Cl− and organic phosphates that moreover dramatically lowers the overall enthalpy of oxygenation of their Hb. Oxygen unloading is presumably further enhanced by a relatively high Bohr effect (ΔLog P50/ΔpH = −0.69) and marked reduction in the titratable histidine content (predicted low proton buffering value) of the component globin chains relative to human HbA. Notably, however, the limited data available suggest these latter attributes may be widespread among shrews and hence likely are not adaptations to chronic altitudinal hypoxia per se.
Glucose metabolism in fish: a review
Venue: Journal of Comparative Physiology B

Teleost fishes represent a highly diverse group consisting of more than 20,000 species living across all aquatic environments. This group has significant economical, societal and environmental impacts, yet research efforts have concentrated primarily on salmonid and cyprinid species. This review examines carbohydrate/glucose metabolism and its regulation in these model species including the role of hormones and diet. Over the past decade, molecular tools have been used to address some of the downstream components of these processes and these are incorporated to better understand the roles played by carbohydrates and their regulatory paths. Glucose metabolism remains a contentious area as many fish species are traditionally considered glucose intolerant and, therefore, one might expect that the use and storage of glucose would be considered of minor importance. However, the actual picture is not so clear since the apparent intolerance of fish to carbohydrates is not evident in herbivorous and omnivorous species and even in carnivorous species, glucose is important for specific tissues and/or for specific activities. Thus, our aim is to up-date carbohydrate metabolism in fish, placing it to the context of these new experimental tools and its relationship to dietary intake. Finally, we suggest that new research directions ultimately will lead to a better understanding of these processes.
Water balance trumps ion balance for early marine survival of juvenile pink salmon (Oncorhynchus gorbuscha)
Venue: Journal of Comparative Physiology B

Smolting salmonids typically require weeks to months of physiological preparation in freshwater (FW) before entering seawater (SW). Remarkably, pink salmon (Oncorhynchus gorbuscha) enter SW directly following yolk absorption and gravel emergence at a size of 0.2 g. To survive this exceptional SW migration, pink salmon were hypothesized to develop hypo-osmoregulatory abilities prior to yolk absorption and emergence. To test this, alevins (pre-yolk absorption) and fry (post-yolk absorption) were transferred from FW in darkness to SW under simulated natural photoperiod (SNP). Ionoregulatory status was assessed at 0, 1 and 5 days post-transfer. SW alevins showed no evidence of hypo-osmoregulation, marked by significant water loss and no increase in gill Na+/K+-ATPase (NKA) activity or Na+:K+:2Cl− cotransporter (NKCC) immunoreactive (IR) cell frequency. Conversely, fry maintained water balance, upregulated gill NKA activity by 50 %, increased the NKA α1b/α1a mRNA expression ratio by sixfold and increased NKCC IR cell frequency. We also provide the first evidence of photoperiod-triggered smoltification in pink salmon, as fry exposed to SNP in FW exhibited preparatory changes in gill NKA activity and α1 subunit expression similar to fry exposed to SNP in SW. Interestingly, fry incurred larger increases in whole body Na+ than alevins following both SW and FW + SNP exposure (40 and 20 % in fry vs. 0 % in alevins). The ability to incur and tolerate large ion loads may underlie a novel mechanism for maintaining water balance in SW prior to completing hypo-osmoregulatory development. We propose that pink salmon represent a new form of anadromy termed “precocious anadromy”.
Saccadic tracking of targets mediated by the anterior-lateral eyes of jumping spiders
Venue: Journal of Comparative Physiology A

The modular visual system of jumping spiders (Salticidae) divides characteristics such as high spatial acuity and wide-field motion detection between different pairs of eyes. A large pair of telescope-like anterior-median (AM) eyes is supported by 2–3 pairs of ‘secondary’ eyes, which provide almost 360 degrees of visual coverage at lower resolution. The AM retinae are moveable and can be pointed at stimuli within their range of motion, but salticids have to turn to bring targets into this frontal zone in the first place. We describe how the front-facing pair of secondary eyes (anterior lateral, AL) mediates this through a series of whole-body ‘tracking saccades’ in response to computer-generated stimuli. We investigated the ‘response area’ of the AL eyes and show a clear correspondence between the physical margins of the retina and stimulus position at the onset of the first saccade. Saccade frequency is maximal at the margin of AL and AM fields of view. Furthermore, spiders markedly increase the velocity with which higher magnitude tracking saccades are carried out. This has the effect that the time during which vision is impaired due to motion blur is kept at an almost constant low level, even during saccades of large magnitude.