Biology subjects

Julien, A. R.

Publications and source records attributed to Julien, A. R..

5 recordsLinked to original sources

bioRxiv2026

Semen collection, short term storage, and cryopreservation in the Texas horned lizard (Phrynosoma cornutum)

As global reptile populations continue to decline, improving reproductive success in managed populations of listed species, such as Phrynosoma cornutum (the Texas horned lizard) has become increasingly critical for species survival. One understudied area of reproductive research in reptile species is gamete collection and storage, a crucial component for maintaining genetic diversity. In Texas, semen was collected from wild P. cornutum (n = 20) in June 2025. Semen collection was performed via electroejaculation (EEJ) under alfaxalone anesthesia. Prior to semen collection, snout-vent-lengths (SVL) and weights were recorded and testes measurements were taken using a portable ultrasound. Average sperm motility and concentration across all lizards was 83.7% and 85.7 x 106 sperm/mL, respectively. While lizards with longer SVLs had higher sperm motility, weight and testis size did not affect sperm parameters. Samples were extended in INRA96 and divided for use in cold-storage longevity or cryopreservation trials. Samples under cold-storage conditions were assessed for motility daily for 10 days. Motility was not significantly reduced until 48 hours post-collection and maintained 19% motility at day 10. For cryopreservation, samples were diluted 1:1 in INRAFreeze cryopreservation media and frozen in liquid nitrogen, then immediately thawed. Average post-thaw sperm motility was 13.9%, with the highest post-thaw motility recorded at 38.2%. This is the first report of semen storage and cryopreservation in Phrynosoma and provides valuable insight into semen storage potential in reptile species.

zoology↗

bioRxiv2024

Tracking gonadotropin-releasing hormone-mediated movement in-vivo using quantum dot nanoparticles: insights into pathways leading to sperm release

As the number of conservation breeding programs for at-risk amphibians increase, application of assisted reproductive technologies (ARTs) has likewise grown, with hormone therapy being the most widely utilized technique. Significant interest has been raised for viable alternatives to traditional intracelomic injection for hormone treatment that may be simpler, require less hormone, induce a faster response and be more suitable for animals of different sizes or for minimal contact. We utilized quantum dot (QD) nanoparticles conjugated to GnRHa (GnRHa-QDs) as a means of monitoring exogenous GnRHa dispersal through living Fowlers toads to investigate how delivery route may affect hormone pathway and efficacy after intracelomic, nasal, and oral administration. Real-time GnRHa-QD movement was tracked using in vivo imaging while hormone binding and QD aggregation were validated using fluorescence microscopy and measurements of spermiation responses following the administration of unconjugated GnRHa, unconjugated QDs, and GnRHa-QDs GnRHa alone was found to induce spermiation in 58.3%, 76.9% and 92.3% of males when administered by intracelomic, oral and nasal routes, respectively. When given through intracelomic injection GnRHa-QD caused spermiation and dispersed throughout the abdominal cavity to then aggregate within the brain, heart, liver, gastrointestinal (GI) tract, kidneys, and testes while unconjugated QDs did not. By contrast, GnRHa-QDs administered by oral or nasal routes were observed moving to the tympanic membrane and down the throat to the GI tract of the toads, but only nasal-administered GnRHa-QDs showed organ aggregation and were only found in the kidneys. Unconjugated QDs exhibited similar in vivo signal dispersal as their conjugated counterparts initially but did not aggregate in any organs over time nor induce spermiation. Through the use of novel QD hormone conjugates, in vivo imaging, and histology we were able to gain insight into how hormone pathways and efficacy might be impacted by delivery route which result in variations in physiological response to hormone treatment.

physiology↗

bioRxiv2024

Sperm quality metrics exhibit annual fluctuations in a critically endangered amphibian managed under human care

The Puerto Rican crested toad (PRCT) is Puerto Ricos only endemic toad and has undergone rapid population decline within the last 40 years. As a hedge against extinction, captive assurance colonies have been established at several zoological institutions for breeding and reintroduction. However, reproductive output has remained low, despite the use of hormone therapies to attempt to bypass missing abiotic cues and stimulate reproductive behaviors. This low output necessitates a better understanding of natural fluctuations in gamete, specifically sperm, quality in captive individuals. To generate an understanding of natural gametic cycles in captive PRCTs, we administered male PRCTs (n = 86) housed under natural temperature and photoperiod cycles with exogenous hormones monthly for one year. Samples were analyzed for motility and concentration to assess variations in sperm quality by month. Spermiation was successfully stimulated every month, but quality fluctuated; sperm motility was highest in June and July, while sperm concentration was highest in December, January, and March. These results indicate that, while hormones can be utilized to stimulate gamete production in PRCTs year-round, sperm quality is not consistent. Furthermore, the seasonal occurrence of peak sperm production of captive males differed from natural peaks reported for wild PRCTs. Our results illustrate the need for more biologically informed strategies for breeding of at-risk anuran populations.

zoology↗

bioRxiv2021

Social boldness in male green anole lizards correlates with baseline vasopressin activity

Across species, individuals within a population differ in their level of boldness in social encounters with conspecifics. This boldness phenotype is often stable across both time and social context (e.g., reproductive versus agonistic encounters). Various neural and hormonal mechanisms have been suggested as underlying these stable phenotypic differences, which are often also described as syndromes, personalities, and coping styles. Most studies examining the neuroendocrine mechanisms associated with boldness examine subjects after they have engaged in a social interaction, whereas baseline neural activity that may predispose behavioral variation is understudied. The present study tests the hypotheses that physical characteristics, steroid hormone levels, and baseline variation in Ile3-vasopressin (VP, a.k.a., Arg8-vasotocin) signaling predispose boldness during social encounters. Boldness in agonistic and reproductive contexts was extensively quantified in male green anole lizards (Anolis carolinensis), an established research organism for social behavior research that provides a crucial comparison group to investigations of birds and mammals. We found high stability of boldness across time, and between agonistic and reproductive contexts. Next, immunofluorescence was used to colocalize VP neurons with phosphorylated ribosomal protein S6 (pS6), a proxy marker of neural activity. Vasopressin-pS6 colocalization within the paraventricular and supraoptic nuclei of the hypothalamus was inversely correlated with boldness of aggressive behaviors, but not of reproductive behaviors. Our findings suggest that baseline vasopressin release, rather than solely context-dependent release, plays a role in predisposing individuals toward stable levels of displayed aggression toward conspecifics by inhibiting behavioral output in these contexts.

neuroscience↗

bioRxiv2021

Social boldness correlates with brain gene expression in male green anoles

Within populations, some individuals tend to exhibit a bold or shy social behavior phenotype relative to the mean. The neural underpinnings of these differing phenotypes - also described as syndromes, personalities, and coping styles - is an area of ongoing investigation. Although a social decision-making network has been described across vertebrate taxa, most studies examining activity within this network do so in relation to exhibited differences in behavioral expression. Our study instead focuses on constitutive gene expression in bold and shy individuals by isolating baseline gene expression profiles that influence social boldness predisposition, rather than those reflecting the results of social interaction and behavioral execution. We performed this study on male green anole lizards (Anolis carolinensis), an established model organism for behavioral research, which provides a crucial comparison group to investigations of birds and mammals. After identifying subjects as bold or shy through repeated reproductive and agonistic behavior testing, we used RNA sequencing to compare gene expression profiles between these groups within various forebrain, midbrain, and hindbrain regions. The ventromedial hypothalamus had the largest group differences in gene expression, with bold males having increased expression of neuroendocrine and neurotransmitter receptor and calcium channel genes compared to shy males. Conversely, shy males express more integrin alpha-10 in the majority of examined regions. There were no significant group differences in physiology or hormone levels. Our results highlight the ventromedial hypothalamus as an important center of behavioral differences across individuals and provide novel candidates for investigations into the regulation of individual variation in social behavior phenotype.

neuroscience↗