ABSTRACT Intraspecies variability of lumbosacral vertebrae is a known phenomenon in mammals, yet its association with motor function remains poorly understood, particularly in novel laboratory models. The spiny mouse has become a promising model organism for investigating central nervous system regeneration. This study provides an analysis of overground locomotion features in adult spiny mice with different lumbosacral vertebral formulae (VC7‐VT13‐VL5‐VS5 vs. VC7‐VT13‐VL6‐VS4––VL5 and VL6 groups, respectively). General features of locomotor kinematics, their dependence on speed, locomotor gait types, and several anatomical parameters were compared. Multiple locomotor gaits were observed in spiny mice; the most frequently used were trot, canter, and gallop. A decrease in step cycle duration, stance duration, limb step width, perineum oscillation amplitude, and toe‐heel angle, together with an increase in relative and absolute swing duration with increasing speed, was revealed. Animals from the VL6‐group showed significantly lower perineum oscillation amplitude in trot. No intergroup differences in hindlimb length and pelvic metrics were observed; however, a higher lumbar region length was found in the VL6‐group. We suggest that the observed differences in stepping parameters during locomotion in spiny mice with the VL6‐group formula may be related to spine biomechanics, or linked to differences in the neuronal control of locomotion, which requires further investigation.
ABSTRACT Understanding critical thermal tolerance and physiological stress responses is crucial to evaluating fish resilience to environmental changes. This study evaluated the critical thermal maximum (CTmax) and minimum (CTmin) under normoxic (sufficient oxygen supply; dissolved oxygen (DO) > 6.0 mg/L) and hypoxic (deficient oxygen supply; DO < 2.0 mg/L) conditions in long‐whiskered catfish ( Mystus gulio ), a commercially important, climate‐sensitive estuarine species from the Bay of Bengal. Under normoxia, CTmax and CTmin were recorded as 41.8 ± 0.24°C and 11.6 ± 0.33°C, respectively, while under hypoxia, CTmax and CTmin were 36.9 ± 3.44°C and 13.5 ± 0.36°C, respectively. Dissolved oxygen levels decreased notably at CTmax under hypoxia, while free CO 2 levels showed the opposite trend. At CTmax and CTmin, oxygen saturation was significantly reduced ( p < 0.05) under hypoxia compared to both normoxia and the starting point. Oxygen consumption and opercular respiratory rates rose significantly at CTmax under hypoxia. Hemato‐biochemical parameters revealed notable changes, with significantly lowered levels of hemoglobin and red blood cell counts, while levels of glucose, cholesterol, and white blood cell count increased significantly under hypoxic conditions in both CTmax and CTmin. Erythrocytic cellular and nuclear abnormalities were more prevalent under hypoxia in both CTmax and CTmin. Water quality parameters also fluctuated with temperature changes. M. gulio recovered successfully immediately before CTmax and CTmin when oxygen was restored, and the temperature increment was stopped. These findings demonstrate the reduced thermal tolerance of M. gulio under hypoxia and highlight significant physiological and cellular stress responses, revealing key mechanisms in the species’ adaptive capacity under environmental stressors.
ABSTRACT Marine organisms often respond to chemical cues released by conspecifics, and such cues can trigger reproductive behavior. In abalone, gamete release by one individual may stimulate spawning in nearby individuals. In this study, gonadal suspensions prepared from the ovaries and testis of disk abalone Haliotis discus discus were incubated for approximately 1 h at different temperatures and then exposed to sexually mature individuals to evaluate their egg‐laying‐ and sperm‐release‐inducing activity, as well as the quality of the resulting gametes. Suspensions incubated at room temperature (20 ± 0.3°C) or at 40°C generally retained their egg‐laying‐ and sperm‐release‐inducing activity relative to freshly prepared suspensions. However, egg‐laying‐inducing activity of the ovarian suspension in females appeared to begin to decline at 40°C, although the difference from the control was not statistically significant ( p = 0.086). Overall, the inducing activity of the gonadal suspensions decreased sharply at 50°C, at which egg laying and sperm release were significantly reduced. However, when gametes obtained after exposure to the gonadal suspensions were artificially fertilized, fertilization rates did not differ significantly among treatment groups. These results indicate that incubation temperature had little effect on subsequent fertilization success. In contrast, the gamete‐release‐inducing activity of components present in the gonadal suspensions was sensitive to heating, with a marked decline at 50°C. The findings provide insight into the thermal sensitivity of gamete‐release‐inducing activity in abalone gonadal suspensions and may contribute to a better understanding of chemical communication during reproduction in marine invertebrates.
ABSTRACT In sika deer Cervus nippon , the corpus luteum (CL), which is formed after ovulation, secretes progesterone, which is essential for establishing and maintaining pregnancy. Typically, one CL develops per pregnancy; however, some cervids exhibit multiple CLs even when carrying a singleton. In sika deer, secondary CLs are observed in approximately 80% of pregnant females; however, their absence in some females suggests that they may not be essential for maintaining pregnancy. In this study, we investigated whether secondary CLs support progesterone secretion and facilitate earlier conception. This study was conducted in Nishiokoppe‐mura, Hokkaido, Japan. Uteri and ovaries were collected from 1620 wild sika deer ( C. n. yezoensis ) (> 1 year old), legally harvested through hunting and population control operations, and the number and size of CLs were measured. Fetal size was measured to estimate conception dates. The pregnancy rate was 94.1%, and the twinning rate was 0.93%. Females carrying a single fetus had 1–5 CLs, whereas those carrying twins had 2–4 CLs. The mean number of CLs in females carrying one fetus was 1.86, with secondary CLs occurring in 83.1% of all cases. Notably, the estimated median conception date was significantly earlier in females with secondary CLs than in those with only one CL, with a difference of approximately 20 days. These results suggest that when luteal function is inadequate during the early breeding season, sika deer develop secondary CLs to support progesterone secretion and allow for early conception. This adaptation may result in optimal birth timing and serve to enhance reproductive success.
The association between species' habitat preferences (e.g., aquatic, terrestrial, arboreal) and traits related to body temperature regulation and water balance has been relatively well studied in anurans. However, whether such associations hold for species occupying the same general habitat while differing in other relevant functional attributes remains poorly explored. Here, we studied the thermal and hydric physiology of five Neotropical frogs (Leptodactylus podicipinus, L. fuscus, L. mystacinus, L. macrosternum, and L. luctator) differing in body size and degree of association with water bodies, but known to co-occur in the same general habitat. We measured area-specific rates of evaporative water loss, skin resistance, area-specific water uptake, dehydration tolerance, thermal preference, thermal tolerance, and optimal temperature for locomotion. Area-specific rates of water loss and gain scaled negatively with body size, indicating strong allometric effects on water exchange. This size dependence, coupled with differences in dehydration tolerance, suggests alternative strategies for coping with desiccation, in which larger frogs rely on lower area-specific water loss to minimize desiccation risks, whereas smaller species compensate for their higher area-specific water loss through greater dehydration tolerance. In contrast, thermal preference and upper thermal tolerance showed limited interspecific variation and were unrelated to body size. Differences in thermal tolerance breadth were driven primarily by variation in lower thermal limits and showed no association with habitat preference. Field body temperatures were consistently lower than thermal preferences but remained within optimal ranges for performance. Our results indicate that even closely related species sharing the same habitat differed markedly in water balance strategies, highlighting how body size, dehydration tolerance, and thermal physiology interact to shape ecological performance.
