Influence of incubation temperature and embryonic motility on the growth of members of Caiman yacare (Daudin, 1802)

This study aimed to evaluate whether skeletal development of the Pantanal Caiman (Caiman yacare) is similarly influenced by temperature variation and controlled increases in embryo motility. All eggs were incubated at 90% humidity and 29 °C for the first 45 days. Thereafter, the incubation temperature was either maintained at 29 °C and embryos were treated with 4-aminopyridine (4-AP) on days 46, 47, 48, and 49 (Group I, 29 °C 4-AP, n = 15); maintained at 29 °C (n = 14; Group II); or at 33 °C (n = 14, Group III). Embryonic movement was measured using an Egg Buddy® digital monitor on days 30, 35, 42, 49, 56, and 60, at which point embryos were euthanized and samples were collected for analysis. No differences were observed between groups with varying incubation temperatures. In contrast, embryonic motility was greater in embryos treated with 4-AP (P < 0.001) on day 49, and this was associated with higher proportions of snout-vent and hand lengths. This study demonstrates for the first time that pharmacologically induced increases in embryo motility result in phenotypic changes to the proportion of elements during prenatal ontogeny, thereby effectively altering the adaptation of the species to specific environments.

Age-related Changes in the Response of Embryonic Motility to Acute Hypoxia During the Third Quarter of Chick Embryogenesis

Environmental factors may affect the growth, size, phenotype, behavior, and other characteristics of avian embryos at different developmental stages; however, the roles of individual embryonic physiological systems in these effects remain largely unclear. Embryonic motility is an important component of the prenatal development observed almost throughout embryogenesis and may be a precursor of post-hatching motor behavior. The influences of the environment on the development of motor behavior during embryogenesis (notably the embryonic motility affected by hypoxia) remain poorly studied. Consequently, using the chick embryo, we investigated the effect of acute hypoxia (10% or 5% О2 for 20 or 40 min) on embryonic cyclic motility at incubation days (D) 10, 12, 14, and 15 using in vivo video recording. Hypoxia inhibited motility; specifically, the average duration of activity and inactivity phases during hypoxic exposure were shortened and prolonged, respectively. Age-related changes in the responses to 10% and 5% O2 differed. The time course of the motility response to acute hypoxia varied during the D10-15 period and demonstrates that the embryo was capable of recovering motility under hypoxia. The recovery was likely enhanced with age due to maturation of regulatory capacity.

A system for the determination of planar force vectors from spontaneously active chicken embryos

Generally, a combination of kinematic, electromyographic (EMG), and force measurements are used to understand how an organism generates and controls movement. The chicken embryo has been a very useful model system for understanding the early stages of embryonic motility in vertebrates. Unfortunately, the size and delicate nature of embryos makes studies of motility during embryogenesis very challenging. Both kinematic and EMG recordings have been achieved in embryonic chickens, but two-dimensional force vector recordings have not. Here, we describe a dual-axis system for measuring force generated by the leg of embryonic chickens. The system employs two strain gauges to measure planar forces oriented with the plane of motion of the leg. This system responds to forces according to the principles of Pythagorean geometry, which allows a simple computational program to determine the force vector (magnitude and direction) generated during spontaneous motor activity. The system is able to determine force vectors for forces >0.5 mN accurately and allows for simultaneous kinematic and EMG recordings. This sensitivity is sufficient for force vector measurements encompassing most embryonic leg movements in midstage chicken embryos allowing for a more complete understanding of embryonic motility. Variations on this system are discussed to enable nonideal or alternative sensor arrangements and to allow for translation of this approach to other delicate model systems.

Postnatal persistence of episodic spontaneous rapid-body-movement bursts and twitches in the cuttlefish, Sepia officinalis

Measurements made under microscopic examination of spontaneous motility shortly before and after hatching in the cuttlefish, Sepia officinalis, revealed a developmental continuity wherein bursts of vigorous mantle contractions lasting a few seconds at most, often associated with irregular twitching of the tentacles and head (but less often of the eyes or chromatophores), follow each other at variable intervals ranging from less than 5 s to many minutes. Releasing the animals prematurely into sea water had no qualitative effect on visible movements but augmented their incidence considerably if done several days before hatching, while reducing it if done shortly prior to hatching. That this was not an age effect is suggested by the lack of any difference between the two groups after their emergence from the egg capsule. The temporal patterning of these stereotyped ‘rapid-body-movements’, defined here as an immature subclass of ‘motorically active sleep’, differed both quantitatively and qualitatively from the repetitive bouts of swimming (‘active wakefulness’) that also occur episodically in hatchlings but not in embryos. Similar to endothermic vertebrates, sleep bursts in cuttlefish rapidly became much less frequent with increasing age as the incidence of wake-like behaviour increased. Spontaneous embryonic motility, c.q., active sleep, thus appears to constitute an ontogenetically and phylogenetically primordial behavioural state which continues without discontinuity into postnatal life, with classical ‘rapid-eye-movement’, c.q., ‘paradoxical’ sleep, being a later appearing special case.

Embryonic motility and hatching success of Ambystoma maculatum are influenced by a symbiotic alga

To augment O2 supply through the jelly mass and egg capsule, embryonic yellow-spotted salamanders ( Ambystoma maculatum (Shaw, 1802)) take advantage of a unicellular alga, Oophila ambystomatis . Convective currents from surface cilia, however, may also enhance O2 transport, whereas muscular contractions could either enhance delivery or contribute to O2 consumption. Embryonic motion is, therefore, potentially vital to salamander development. We examined embryonic motility across multiple developmental stages, survivorship, and hatching timing in response to different algal levels by rearing salamander egg masses under three different diel light cycles: 24 h dark, 12 h light, and 24 h light per day. Embryos raised in continuous light hatched synchronously and at slightly earlier developmental stages than embryos raised in the dark or in 12 h light per day. We removed eggs at multiple stages to examine embryonic rotation and muscular contraction rates under 180 min periods of both light and dark. Rotational movements occurred more frequently in alga-free than in algae-inhabited eggs, and more frequently in algae-inhabited eggs in the dark than in light. At later developmental stages, muscular contractions were more frequent in embryos from algae-inhabited egg masses in light than those in the dark; thus embryos with less O2 reduced muscular activity, thereby reducing energy consumption when O2 availability was compromised.

Fast Locomotor Burst Generation in Late Stage Embryonic Motility

We examined muscle burst patterns and burst frequencies for a distinct form of repetitive leg movement recently identified in chick embryos at embryonic day (E)18 that had not been previously studied. The aim was to determine if burst frequencies during repetitive leg movements were indicative of a rhythm burst generator and if maturing muscle afferent mechanisms could modulate the rhythm. Electromyographic recordings synchronized with video were performed in ovo during spontaneous movement at E15, E18, and E20. Multiple leg muscles were rhythmically active during repetitive leg movements at E18 and E20. Rhythmic activity was present at E15 but less well formed. The ankle dorsi flexor, tibialis anterior, was the most reliably rhythmic muscle because extensor muscles frequently dropped out. Tibialis anterior burst frequencies ranged from 1 to 12 Hz, similar to frequencies during fast locomotor burst generation in lamprey. The distribution in burst frequencies at E18 was greatest at lower frequencies and similar to locomotor data in hatchlings. Relative distributions were more variable at E20 and shifted toward faster frequencies. The shell wall anterior to the leg was removed in some experiments to determine if environmental constraints associated with growth contributed to frequency distributions. Wall removal had minimal impact at E18. E20 embryos extended their foot outside the egg, during which faster frequencies were observed. Our findings provide evidence that embryonic motility in chick may be controlled by a fast locomotor burst generator by E15 and that modulation by proprioceptors may emerge between E18 and E20.