Biology subjects

Duncan, N.

Publications and source records attributed to Duncan, N..

8 recordsLinked to original sources

bioRxiv2026

In vitro fertilisation procedure assisted with computer vision models for organic Senegalese sole (Solea senegalensis) culture

Reproductive dysfunction remains a major challenge for Senegalese sole (Solea senegalensis) aquaculture. Hormone-induced ovulation and in vitro fertilisation (IVF) are currently used to overcome the absence of natural courtship behaviours in captivity. This study investigates the feasibility of hormone-free IVF and behaviour-based prediction of ovulation as alternative strategies to enhance reproductive outcomes. We selected males using computer-assisted sperm analysis to assess sperm motility and quality for IVF trials. IVF trials were conducted using selected males and naturally ovulated eggs collected from females during evening hours across six experimental nights in two groups. Fish behaviour was continuously recorded using underwater cameras, and a convolutional neural network was developed to automatically detect Rest the Head (RTH) and Locomotor Activity (LA) behaviours. These behavioural counts, together with timing information, were used as features to train a logistic regression model for predicting ovulation events. Hormone-free IVF achieved fertilization rates up to 44% with 18% hatching success, producing viable larvae without hormonal intervention. Both groups showed significantly elevated RTH and LA during ovulation nights compared to non-ovulation nights, with peak activity occurring between 18:00-19:00 hours. The behavioural prediction model correctly identified ovulation with 82-85% accuracy and an area under the curve of 0.95. These findings demonstrate that sperm-quality-based male selection combined with automated behaviour analysis provides a practical, non-invasive approach for hormone-free reproduction in organic flatfish aquaculture.

animal behavior and cognition↗

bioRxiv2025

Adaptation to warm environments with a fast pace of life in a marine predatory snail

Understanding how latitudinal temperature variation shapes local adaptation of life history strategies is crucial for predicting future responses to warming. Contrasting predictive frameworks explain how growth and other life history traits may respond to differing selective pressures across latitude. However, these frameworks have rarely been explored within the context of fluctuating environmental temperatures across longer (i.e., seasonal) time scales experienced in nature. Furthermore, consequences of growth differences for other aspects of fitness, including reproductive output, remain unclear. Here, we conducted a long-term (17-month) simulated reciprocal transplant experiment to examine local adaptation in two populations of the predatory marine snail Urosalpinx cinerea separated by 8.6{degrees} latitude (1000 km). We reared F1 offspring under two seasonally fluctuating temperature regimes ("warm" and "cold", simulating field thermal conditions experienced by low and high latitude populations, respectively), quantifying temporal patterns in growth, maturation, and reproductive output. We identified striking divergence in life-history strategies between populations in the warm regime, with offspring from the low latitude population achieving greater growth in their first year, and high reproductive output coupled with reduced growth in their second year. In contrast, the high latitude population grew slower in their first year, but eventually attained larger sizes in their second year, at the expense of reduced reproductive output. Responses were consistent with this in the cold regime, although growth and reproductive output was reduced in both populations. Our data provides support for adaptive divergence across latitude consistent with the Pace-of-Life hypothesis, with the low latitude population selected for a fast-paced life characterized by rapid development and early reproduction. In contrast, the high latitude population exhibited slower growth and delayed maturation. Our results highlight the potential limitations of short-term comparisons of growth without considering processes over longer time scales that may exhibit seasonal temperature variation and ontogenetic shifts in energy allocation and imply a radical reshaping of physiological performance and life history traits across populations under climate change.

ecology↗

bioRxiv2022

Coyotes in New York city carry variable dog genomic ancestry and influence their interactions with humans

Coyotes are ubiquitous on the North American landscape as a result of their recent expansion across the continent. They have been documented in the heart of some of the most urbanized cities, such as Chicago, Los Angeles, and New York City. Here, we explored the genomic composition of coyotes in the New York metropolitan area to investigate if genomic demography and admixture differs from expected for urban-dwelling canids. We identified moderate-to-high estimates of relatedness among coyotes living in Queens and adjacent neighborhoods, suggestive of a relatively small population. Although we found low background levels of domestic dog ancestry across most coyotes in our sample, we identified a male suspected to be a first-generation coyote-dog hybrid, as well as his two putative backcrossed offspring that carried approximately 25% dog ancestry. The male coyote-dog hybrid and one backcrossed offspring each carried two mutations that are known to increase human-directed hypersociability in dogs and gray wolves. An additional, unrelated coyote with little dog ancestry also carries two of these mutations. These genetic patterns suggest that gene flow from domestic dogs may become an increasingly important consideration as coyotes continue to inhabit metropolitan regions.

evolutionary biology↗

bioRxiv2021

Recombinant Fsh and Lh therapy for spawning induction of previtellogenic and early spermatogenic arrested teleost, the flathead grey mullet (Mugil cephalus)

With the expansion and diversification of global aquaculture, efforts continue to develop new bio-technologies for assisted reproduction in species that present reproductive dysfunctions. Flathead grey mullet (Mugil cephalus) held in intensive conditions in the Mediterranean region, display a severe reproductive dysfunction, where males do not produce fluent milt and females are arrested at previtellogenesis or early stages of vitellogenesis. In the present study, weekly injections of species-specific single-chain recombinant gonadotropins (rGths); follicle stimulating hormone (rFsh) (6 to 12 g kg-1 doses) and luteinizing hormone (rLh) (2.5 to 24 g kg-1 doses) were administered to induce vitellogenesis, from previtellogenesis / early vitellogenesis to the completion of vitellogenic growth in females and enhance spermatogenesis to produce adequate volumes of sperm from non-fluent males. During the experiment, all treated females (n = 21) developed oocytes in late vitellogenesis with 603 {+/-} 8 m diameter and all treated males produced fluent sperm. To induce oocyte maturation, ovulation and spawning, females were treated with either (i) a priming dose of 30 g kg-1 of rLh and a resolving dose of 40 mg kg-1 of progesterone (P4), (ii) priming and resolving doses of 30 g kg-1 of rLh, or (iii) priming and resolving doses of 40 mg kg-1 of P4 given 24:05 {+/-} 0:40 h apart. Females were placed in spawning tanks with rGth treated males that had fluent sperm. Spontaneous spawns of fertilised eggs were obtained after inducing with rLh + P4 or rLh + rLh (priming and resolving injections) with a spawning success of the 85% (8 of 9 females) and 100% (n = 6), respectively. The eggs collected from the tanks presented 64 {+/-} 22% fertilization with embryo development and 57 {+/-} 24 % hatching. The treatment P4 + P4 had a lower ovulation success (50 % - 3 of 6 females) and spawning success (17 %) with no fertilised eggs. Success was independent of the initial gonadal stage of females. In comparison, control females did not show any advance in gonadal development from initial stages and control males did not produce fluent sperm. The present results confirm the possibility of controlling oogenesis from previtellogenesis to the completion of maturation and fertilised tank spawning using exclusively rFsh and rLh in a teleost species.

physiology↗

bioRxiv2021

The non-steroidal anti-inflammatory drug nimesulide kills Gyps vultures at concentrations found in the muscle of treated cattle.

Throughout South Asia, cattle are regularly treated with non-steroidal anti-inflammatory drugs (NSAIDs) and their carcasses are left for scavengers to consume. Residues of the NSAID diclofenac in cattle carcasses caused widespread mortality and catastrophic population declines in three species of Gyps vulture during the 1990s and 2000s. Diclofenac is now banned, but other NSAIDs are used in its place. Different lines of evidence, including safety testing in Gyps vultures, have shown that some of these other NSAIDs are toxic, or probably toxic, to vultures. The NSAID nimesulide is widely available and commonly used, and has been found in dead vultures with signs of renal failure (i.e. visceral gout) and without the presence of diclofenac and/or other vulture-toxic NSAIDs. Nimesulide is therefore probably toxic to vultures. Here, we report safety testing of nimesulide in Gyps vultures. In a controlled toxicity experiment, we gave two vultures the maximum likely exposure of nimesulide calculated from initial pharmacokinetic and residue experiments in cattle. Two other control birds were given an oral dose of water. Both vultures dosed with nimesulide died within 30 h, after showing outward signs of toxicity and increases in biochemical indicators of renal failure. Post-mortem examinations found extensive visceral gout in both vultures. Both control vultures survived without biochemical indicators of renal failure. With this evidence, we call for an immediate and comprehensive ban of nimesulide throughout South Asia to ensure the survival of the regions Critically Endangered vultures. More generally, testing the impacts of drugs on non-target species should be the responsibility of the pharmaceutical industry, before their veterinary use is licensed.

pharmacology and toxicology↗

bioRxiv2020

Low sperm to egg ratio required for successful in vitro fertilisation in a pair-spawning teleost, Senegalese sole (Solea senegalensis)

Cultured Senegalese sole (Solea senegalensis) breeders fail to spawn fertilised eggs and this bottleneck could be solved with the implementation of large-scale in vitro fertilisation protocols. However, low production of poor-quality sperm has frustrated the development of in vitro fertilisation protocols. Cultured females were induced to ovulate with a 5 {micro}g kg-1 single injection of gonadotropin releasing hormone agonist (GnRHa) and good quality eggs (82.6 {+/-} 9.2% fertilisation) were stripped 41:57 {+/-} 1:46 h after the injection. Sperm was collected from cultured males, diluted in modified Leibovitz and used fresh to fertilise the eggs. A non-linear regression, an exponential rise to a maximum (R = 0.93, P < 0.0001) described the number of motile spermatozoa required to fertilise a viable egg and 1617 motile spermatozoa were sufficient to fertilise 99 {+/-} 12% ({+/-} 95% CI) of viable eggs. Similar, spermatozoa egg-1 ratios of 592 {+/-} 611 motile spermatozoa egg-1 were used in large-scale in vitro fertilisations with 190,512 {+/-} 38,471 eggs. The sperm from a single male (145 {+/-} 50 {micro}L or 8.0 {+/-} 6.8 x 108 spermatozoa) was used to fertilise the eggs. The mean hatching rate of the large-scale in vitro fertilisations was 70 {+/-} 14 % to provide 131,540 {+/-} 34,448 larvae per fertilisation. When unfertilised eggs were stored at room temperature the percentage of viable eggs decreased gradually and indicated the sooner eggs were fertilised after stripping the higher the viability of the eggs. The collection of sperm directly into a syringe containing modified Leibovitz significantly increased the percentage of motile spermatozoa (33.4 {+/-} 12.2 %) compared to dilution in modified Leibovitz immediately after collection (6.6 {+/-} 4.9 %). Senegalese sole have a pair-spawning reproductive behaviour characterised by external gamete fertilisation in close proximity with no sperm competition. The low spermatozoa egg-1 ratio required for maximum fertilisation was consistent with this reproductive behaviour and strategy. The provision of a large-scale in vitro fertilisation protocol (200 {micro}L of sperm per 100 mL of eggs) will enable the industry to operate sustainably and implement breeding programs to improve production.

physiology↗

bioRxiv2020

Providing recombinant gonadotropin-based therapies that induce complete gametogenesis and produce viable larvae from an immature teleost, flathead grey mullet (Mugil cephalus)

Under intensive captive conditions, wild-caught flathead grey mullet (Mugil cephalus) females remained arrested at early gonad development and no sperm could be obtained from males. With the aim to induce and complete oogenesis, induce the release of sperm and obtain fertilized eggs, adult female and male grey mullet were treated with M. cephalus single-chain recombinant gonadotropins (rGths), follicle-stimulating (rFsh) and luteinizing (rLh) hormones. In Experiment 1, fish were treated with a weekly dose of rFsh (15 g kg-1), which in females significantly (P < 0.001) increased plasma concentration of 17{beta}-estradiol and induced vitellogenic oocyte growth up to a maximum mean diameter of 425 {+/-} 19 m after 9 weeks of treatment. In Experiment 2, fish were treated with weekly injections of both rFsh and rLh at different doses (from 2.5 to 12 g kg-1). Oocyte diameter reached 609 {+/-} 5 m, from which final oocyte maturation and ovulation was induced with 30 g kg-1 of rLh and 40 mg kg-1 of progesterone. Good quality sperm (> 75% motile spermatozoa) was obtained from males in both experiments, and in Exp. 2 the addition of rLh induced the production of higher quantities of sperm that were used to fertilise the eggs. Although fertilisation was low (0.4 %), these fertilized eggs with embryo development produced viable larvae (71% hatching rate). This is the first report in a teleost species, to obtain larvae from eggs that were from immature females induced through to maturation with rGths. In comparison, control females remained arrested as immature fish and control males did not produce sperm. The study demonstrated that both rGths are effective to induce the entire process of oogenesis in sexually immature female grey mullet and to obtain flowing sperm from males, adding more data to confirm the roles of the Gths in teleost gametogenesis. This advance provides the bases of a therapy for the use in the aquaculture of teleost of commercial interest or the conservation of endangered species.

physiology↗

bioRxiv2018

Investigating speech and language impairments in delirium: a preliminary case-control study

Introduction\n\nLanguage impairment is recognized as a diagnostic feature of delirium, yet there is little neuropsychological research on the nature of this dysfunction. Here we hypothesized that patients with delirium show impairments in language formation, coherence and comprehension.\n\nMethods\n\nThis was a case-control study in 45 hospitalized patients (aged 65-97 years) with delirium, dementia without delirium, or no cognitive impairment (N=15 per group). DSM-5 criteria were used for delirium. Speech was elicited during (1) structured conversational questioning, and (2) the \"Cookie Theft\" picture description task. Language comprehension was assessed through standardized verbal and written commands. Interviews were audio-recorded and transcribed.\n\nResults\n\nDelirium and dementia groups scored lower on the conversational assessment than the control group (p<0.01, moderate effect sizes (r) of 0.48 and 0.51, resp.). In the Cookie Theft task, the average length of utterances (i.e. unit of speech), indicating language productivity and fluency, distinguished patients with delirium from those with dementia (p<0.01, r=0.50) and no cognitive impairment (p<0.01, r=0.55). Patients with delirium performed worse on written comprehension tests compared to cognitively unimpaired patients (p<0.01, r=0.63), but not compared to the dementia group.\n\nConclusions\n\nProduction of spontaneous speech, word quantity, speech content and verbal and written language comprehension are impaired in delirious patients compared to cognitively unimpaired patients. Additionally, patients with delirium produced significantly less fluent speech than those with dementia. These findings have implications for how speech and language are evaluated in delirium assessments, and also for communication with patients with delirium.

neuroscience↗