Issues
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Cover image
Cover Image
Cover: A distinct feature of freshwater mayfly nymphs is an elaborate abdominal cuticular extension, commonly referred to as tracheal gills. The tracheal gills possess ventilation as well as respiratory function, and have long been speculated to participate in ion regulation. Nowghani et al. (pp. 3997–4006) provide evidence that the tracheal gills of Hexagenia rigida ( pictured) participate in the regulation of salt and water balance by directly measuring Na+ uptake at the gills in real time. The integrated function of H. rigida nymph tracheal gills, alimentary canal and Malpighian tubules provides new insight into the ionoregulatory strategies of freshwater arthropods. Photo credit: Chun Chih Timothy Chen.
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REVIEW
Ammonia and urea handling by early life stages of fishes
Summary: We review the metabolic, morphological and physiological features unique to embryonic and larval fishes that are necessary to cope with an amino acid-fuelled metabolism and lack of a functional gill.
Studying emotion in invertebrates: what has been done, what can be measured and what they can provide
Summary: Recent work has adapted methods for assessing emotions in humans and other animals, to invertebrates, with intriguing results. This Review interprets and discusses their utility with respect to the evolution and neurobiology of emotion.
SHORT COMMUNICATION
Waiting for the Sun: the circannual programme of reindeer is delayed by the recurrence of rhythmical melatonin secretion after the arctic night
Summary: Exposure to constant light or constant darkness accelerates the onset of spring physiology in overwintering reindeer; this has implications for current models of circannual time-keeping in mammals.
Humeral loads during swimming and walking in turtles: implications for morphological change during aquatic reinvasions
Summary: Turtle humeri experience reduced torsional loads during swimming compared with terrestrial walking. Such reductions may have facilitated the transition from tubular to flattened limb bones in secondarily aquatic tetrapods.
METHODS & TECHNIQUES
Bringing the analysis of animal orientation data full circle: model-based approaches with maximum likelihood
Summary: A new statistical package developed in R for the maximum likelihood analysis of animal orientation data. Both simulated and empirical examples are provided for demonstration.
RESEARCH ARTICLES
Re-oxygenation after anoxia induces brain cell death and memory loss in the anoxia-tolerant crucian carp
Highlighted Article: Anoxia-tolerant crucian carp sustain brain cell death during early re-oxygenation, as well as impaired memory, although damage is transient and does not diminish learning ability.
Functional morphology of terrestrial prey capture in salamandrid salamanders
Summary: Functional trade-offs of the hyobranchial apparatus result in lower tongue-projection distance, velocity, acceleration and power in semi-aquatic and aquatic salamandrids compared with terrestrial specialists.
Beneficial effects of a heat wave: higher growth and immune components driven by a higher food intake
Summary: Damselfly larvae benefit from a heat wave by increasing growth rate and immune components, which can be attributed to an increase in food intake.
Metabolic costs imposed by hydrostatic pressure constrain bathymetric range in the lithodid crab Lithodes maja
Highlighted Article: Hyperbaric limitation of depth range suggests the incorporation of hydrostatic pressure into a complex model of environmental tolerance, where energy limitation constrains biogeographic range, and into the metabolic framework for ecology and evolution.
Frequency organization of the Johnston’s organ in male mosquitoes (Diptera, Culicidae)
Summary: Male mosquitoes possess at least eight groups of auditory neurons distinct in frequency tuning. They gradually amplify receptor potentials in a non-spiking mode. Individual frequencies range from 85 to 470 Hz.
O2 binding and CO2 sensitivity in haemoglobins of subterranean African mole rats
Summary: Haemoglobin–O2 binding properties of African mole rats reveal low specific CO2 sensitivities compared with humans that predictably safeguard O2 uptake and transport under hypoxic and hypercapnic conditions.
Induced parental care in a poison frog: a tadpole cross-fostering experiment
Summary: Placement of unrelated tadpoles on adult poison frogs triggers a cascade of parental behaviours involving tadpole transport and spatial memory use in both sexes, despite the asymmetric parental sex roles.
The metabolic costs of fighting and host exploitation in a seed-drilling parasitic wasp
Editors' Choice: Fights between parasitoid females require little energy, but drilling through seeds to access hosts is expensive. Females avoid metabolic costs by reusing holes drilled by rivals (superparasitism).
Hydrodynamic function of dorsal fins in spiny dogfish and bamboo sharks during steady swimming
Summary: The function of dorsal fins varies among shark species, and these fins can act in either a stabilizing or thrust-generating role.
Upper thermal limits of growth in brook trout and their relationship to stress physiology
Summary: Elevated temperature (>22°C) reduces growth rate and induces endocrine and cellular stress responses of brook trout. Daily temperature oscillation around a mean temperature of 21°C decreases growth and increases heat shock proteins.
Early gametogenesis in the Pacific oyster: new insights using stem cell and mitotic markers
Summary: Alkaline phosphatase activity and immunochemistry reveal that oyster germline cells are located in the gonad duct outer edge during the resting period and proliferate very early during the next sexual cycle.
Strategies of ionoregulation in the freshwater nymph of the mayfly Hexagenia rigida
Summary: Freshwater mayfly nymphs regulate salt and water balance using the alimentary canal, Malpighian tubules and tracheal gills, and data provide the first direct evidence that the tracheal gills are ion transport organs.
Silica-induced fibrosis: an ancient response from the early metazoans
Highlighted Article: Investigation of the molecular mechanism of an ancient physiological behaviour in sponges in which engulfed quartz particles are fibrogenic and the process is cytokine mediated as in human fibrosis.
Natural epigenetic variation within and among six subspecies of the house sparrow, Passer domesticus
Summary: Genome-wide DNA methylation variation in subspecies of house sparrow is largely independent of subspecies designation and does not follow differences in habitat, but is associated with several other biological phenomena such as morphology, sex and commensalism.
Plausible link between circa‘bi’dian activity rhythms and circadian clock systems in the large black chafer Holotrichia parallela
Summary: The large black chafer Holotrichia parallela has an endogenous circa‘bi'dian rhythm, which is seemingly produced by the circadian clock system. The 2-day periodicity appears in both the laboratory and the field.
Mitochondrial capacity, oxidative damage and hypoxia gene expression are associated with age-related division of labor in honey bee (Apis mellifera L.) workers
Summary: Changes in mitochondrial activity and hypoxia gene expression in the head, thorax and abdomen of honey bee workers are associated with the nurse bee to forager transition.
Function of the hypobranchial muscles and hyoidiomandibular ligament during suction capture and bite processing in white-spotted bamboo sharks, Chiloscyllium plagiosum
Summary: Hypobranchial muscles of bamboo sharks allow for storage and release of elastic strain energy during suction feeding, which is facilitated by a four-bar linkage that links jaw and hyoid depression.
Variation in developmental trajectories of physiological and somatic traits in a common songbird approaching fledging
Summary: Developmental trajectory just prior to fledging in songbirds may be hardwired across natural and experimentally manipulated environmental conditions, but shows oxidative stress cost.
Sex hormones and the development of sexual size dimorphism: 5α-dihydrotestosterone inhibits growth in a female-larger lizard (Sceloporus undulatus)
Summary: Dihydrotestosterone mimics the effects of testosterone on growth and coloration in a female-larger lizard, and both sexes share downstream regulatory mechanisms required for growth inhibition and enhanced coloration in response to androgens.
CORRESPONDENCE
Using the reactive scope model to redefine social stress in fishes

In their Review, Katie Gilmour and colleagues redefine the ambiguous concept of social stress by using the reactive scope model as a framework to explain the divergent physiological phenotypes of dominant and subordinate fishes.
JEB grants to support junior faculty

Learn about the grants that we launched in 2023 to support junior faculty from two of our awardees: Erin Leonard, Early-Career Researcher (ECR) Visiting Fellowship recipient, and Pauline Fleischmann, Research Partnership Kickstart Travel Grant recipient. The next deadline to apply is 6 June 2025.
Thirteen-lined ground squirrels survive extraordinarily low blood oxygen

Brynne Duffy and colleagues reveal that thirteen-lined ground squirrels are true hypoxia champions surviving extreme low blood oxygen, down to just 34% oxygen, when they emerge briefly from hibernation.
The Company of Biologists Workshops

For the last 15 years, our publisher, The Company of Biologists, has provided an apt environment to inspire biology and support biologists through our Workshops series. Read about the evolution of the Workshop series and revisit JEB's experience with hosting the first Global South Workshop.
Fast & Fair peer review

Our sister journal Biology Open has recently launched the next phase of their Fast & Fair peer review initiative: offering high-quality peer review within 7 working days. To learn more about BiO’s progress and future plans, read the Editorial by Daniel Gorelick, or visit the Fast & Fair peer review page.