Search Results (97)

Larval rearing is a critical phase in shellfish-hatchery production. Thus, optimizing larval survival, growth, and settlement is essential for reliable seed output. This study investigated the effect of rearing density on larvae and settlement performances of the carpet shell clam Ruditapes decussatus in captivity. Furthermore, the influence of natural biofilm-based microalgae on larvae settlement and post-larvae performance was also investigated herein. Three larval rearing densities (10, 20, and 40 larvae mL⁻¹) were studied during larvae development, and four settlement densities (35, 70, 100, and 140 larvae cm⁻²) were tested during larvae settlement and metamorphosis. The effect of biofilm-based microalgae on larvae settlement and post-larvae pattern was tested at a standard settlement density (70 larvae cm⁻²). High larval density significantly reduced survival (18% at 40 larvae mL⁻¹) compared with lower densities (26% and 23% at 20 and 10 larvae mL⁻¹, respectively). Significantly higher settlement rate (36% and 33%) and spat yield were observed at 35 and 70 larvae cm⁻², respectively, compared to high densities (100 and 140 larvae cm⁻²). Remarkably, post-larvae reared under the biofilm treatment showed faster growth performances compared to untreated (control) ones. These findings indicated that lower larval and settlement densities enhance survival and settlement rates. Natural biofilm promoted post-larval growth, and therefore, its use can be an effective strategy to improve R. decussatus hatchery outcomes. Full article

Sichuan bream (Sinibrama taeniatu), an endemic small economic fish in the upper Yangtze River, has achieved captive breeding breakthroughs. To advance standardized and large-scale aquaculture, this study investigated intestinal development, enzyme activities, gut microbiota, and its interactions with rearing water microbiota across six developmental stages (G1–G6) from hatching to sexual maturity of Sichuan bream. Results showed its progressive refinement of external morphology and intestinal developing into multiple flexures. Histology examination revealed four foregut layers with continuously increasing villus height. Digestive enzyme analysis revealed significantly higher activity of trypsin compared to that of amylase and lipase (p < 0.05). 16S rRNA sequencing identified Proteobacteria, Firmicutes, Bacteroidota, Actinobacteriota, and Fusobacteria as the dominant phyla in both gut and rearing water microbiota. Gut communities shifted from Proteobacteria-dominance (C₁–C₅) to Firmicutes-dominance (C6). The microbial source tracking analysis indicated water contributed to gut microbiota of Sichuan bream, particularly during G3. This study clarified the intestinal development patterns and gut microbiota colonization dynamics of Sichuan bream. The findings provide reference materials for the research on the growth patterns and host–microbe interaction of Sichuan bream. They lay a theoretical foundation for the protection and utilization of Sichuan bream resources, ultimately aiding in their proliferation and release. Full article

The overexploitation of wild populations for the marine ornamental trade necessitates optimized captive breeding, particularly for iconic species like the clownfish Amphiprion ocellaris. This study investigated the social behavior and cognitive abilities of juvenile clownfish in relation to artificial rearing practices. Using modified three-tank tests, we assessed social preference and cognition ability in two size groups: Small-bodied Group (SG: 2.0–2.5 cm) and Large-bodied Group (LG: 3.5–4 cm). The results indicated that clownfish have the following: (a) Strong Social Preference: Both SG and LG exhibited significant preference for areas near conspecifics (SPI > 0), with SG showing significantly higher SPI values than LG. (b) Developmental Stage Differences: SG demonstrated a stronger tendency to cluster tightly near conspecifics. LG showed wider exploration patterns and greater movement. (c) Cognition Ability: SG showed renewed interest towards a novel fish after habituation to a familiar fish, while LG displayed a stronger preference for the familiar fish. These findings suggest that clownfish juveniles possess advanced sociality and basic cognition ability. Furthermore, the observed shift in social interaction preference with developmental stages informs optimal timing for grading practices to minimize artificial rearing stress. This study provides some behavioral insights for optimizing large-scale artificial rearing protocols for clownfish, reducing pressure on wild populations. Full article

Tiger beetles serve as bioindicators of ecosystem health but are under increasing threat from habitat loss and population decline. Ex situ conservation via captive breeding offers promise for species lacking viable wild populations. We evaluated laboratory rearing from egg to adult for eight Korean tiger beetle species to determine the developmental period per developmental stage, mortality rates, larval burrow entrance size, and head–pronotum morphological characteristics under controlled laboratory conditions. High mortality (37.5–80%) occurred during the transition from the pre-pupa to pupa stage, suggesting that mass larval production is needed to offset losses. Reared-type adults of most tiger beetle species tended to be smaller in body length than wild-type adults. Species-specific behaviors (e.g., feeding habits in Cephalota chiloleuca) and the overwintering times of spring–fall and summer species are different, indicating that uniform rearing protocols are suboptimal. Our findings suggest the importance of species-specific adjustment of rearing methods (feeding frequency, overwintering timing) to increase the success of ex situ conservation methods for tiger beetles. In addition, the larval burrow entrance size offered limited utility for species identification in mixed-species habitats, whereas the color of the head and pronotum was considered helpful in identifying some tiger beetle species. Full article

The captive breeding of marine ornamental fish with specialized larval requirements—such as Chaetodontoplus mesoleucus—remains a major bottleneck in aquaculture, largely due to the lack of techniques tailored to their unique morphological and nutritional needs. The global marine ornamental aquaculture market is valued at approximately USD 2.15 billion annually; however, only around 10% of marine ornamental species are currently supplied through captive breeding, highlighting a substantial technological gap. The artificial propagation of C. mesoleucus is particularly challenging due to the species’ small mouth gape and high nutritional demands during early development. To address this issue, we evaluated the effects of three live-prey types—Euplotes sp., Brachionus sp., and Bestiolina coreana—as well as a mixed diet containing all three, on larval performance. From 3 days post-hatch, larvae were fed each prey type at equal densities (15–20 individuals/mL), and water quality was carefully maintained to minimize external influences. Survival and total length were assessed at 14 dph. At the end of the trial, the mixed-diet group showed the highest survival rate (36.2 ± 5.6%), whereas larvae fed only B. coreana exhibited the greatest total length (7.4 ± 1.2 mm) and a high metamorphosis rate (97.8%). These findings demonstrate that prey selection significantly influences the early survival and growth in C. mesoleucus larvae and highlight the critical role of copepods in promoting growth performance. However, as larval biomass was not quantified, the findings should be interpreted with caution, and future studies incorporating biomass assessments are needed to draw more conclusive inferences. The successful mass rearing of this species supports the feasibility of captive production to reduce wild harvesting, protect coral-reef biodiversity, and promote sustainable ornamental aquaculture. Full article

Game-farmed quails that are currently raised in captivity and released in hunting preserves are not attractive for many hunters because of their low antipredator instinct, which is due to the fact that in most cases, these farm-reared quails are hybrids between European common (Coturnix coturnix) and Japanese (Coturnix japonica) quails, with the latter having been selectively bred for docility. This study aimed at assessing the antipredator response of game-farmed and Japanese quails by performing three tests: human approach test, simulated aerial predator approach test and tonic immobility test. Thirty game-farmed quails (average body weight: 133 g) and thirty Japanese quails (323 g) were subjected to the tests. For each genotype of quail, fifteen males and fifteen females were used. In the human approach test, the distance at which quails moved was greater for game-farmed quails than for Japanese ones (37.4 vs. 19.6 m, p < 0.001). In the simulated aerial predator approach test, female quails of the Japanese species crouched down at the longest distance with respect to the predator (9.83 m), whereas no significant difference existed for this trait among the other three groups (6.84 m, on average). The percentage of quails flying when the predator got closer was higher for the Japanese species than for the game-farmed quails (23.3 vs. 3.33%, p = 0.023). Fewer inductions were needed to cause tonic immobility in the game-farmed quails than in the Japanese ones (3.10 vs. 4.10, p = 0.009), but then, the duration of the tonic immobility response did not differ significantly between the two genotypes. No effect of sex was detected in the human approach and tonic immobility tests. In conclusion, as compared with Japanese quails, game-farmed quails showed more fearful behaviour when confronted with a human being. Full article

This study investigated the effects of feeding striped beakfish (Oplegnathus fasciatus) newly hatched larvae on the survival and growth of kawakawa (Euthynnus affinis) larvae and juveniles, as well as their relative growth patterns. Fertilized eggs of kawakawa were reared in 1 m³ experimental tanks until 13 days post-hatch (dph). From 3 to 8 dph, larvae were fed enriched rotifers, and from 9 to 12 dph, they were assigned to two experimental groups: one receiving only a formulated diet and the other receiving a combination of the formulated diet and 10,000 striped beakfish newly hatched larvae every day in each tank. The group fed newly hatched larvae exhibited approximately 36% greater growth than the group fed only the formulated diet. However, survival at 13 dph was approximately 34% lower, suggesting that further investigation is needed to determine the optimal feeding quantity of newly hatched larvae. The relative growth patterns of larvae and juveniles reared in a commercial 30 m³ tank showed morphological traits characteristic of scombrid fish, such as a longer preanal length and upper jaw length. Growth patterns varied at three key body lengths (notochord length or standard length; 3, 8–10, and 30 mm), as well as at their corresponding standard lengths. In kawakawa, the upper jaw exhibited early accelerated growth compared to other scombrid species. This characteristic is believed to facilitate the early onset of piscivory under captive conditions. Full article

Background/Objectives: European Brown Hare Syndrome (EBHS) is an acute and highly contagious viral disease of hares that causes considerable economic losses on wild and captive-reared hares. No preventive treatments are currently available to defeat the disease. Immunoprophylactic and biosafety measures could be applied to prevent EBHS only in captive-reared hares, where vaccination is proposed as an effective strategy. Due to the lack of a cellular substrate for virus growth, commercially available vaccines are autovaccines produced from inactivated liver suspensions of hares dead for EBHS. Therefore, using a recombinant vaccine based on VP60 major capsid protein seems a viable alternative to overcome such a problem. Methods: the 6xHis C-terminal tagged VP60 protein of EBHSV was expressed and produced in baculovirus, purified by affinity chromatography and the self-assembled recombinant (rEVP60-His₆) protein. To establish the protective properties of rEVP60-His₆-based VLPs, hares were immunised with 50 and 100 µg of VLPs and parenterally challenged with EBHSV. Results: all hares vaccinated with 100 µg of VLPs survived after the experimental infection, demonstrating the excellent protective ability of this prototype VLPs-based vaccine. Conclusions: self-assembled EBHSV rEVP60-His₆ protein was successfully produced following a rapid, simple, low-cost protocol. Although the protective efficacy of such VLPs were experimentally demonstrated, some key aspects remain to be clarified, including the duration of protection, the entity of the antibody response, and the ability to stimulate cell-mediated response. Last, an additional aspect to be evaluated is whether the use of an adjuvant can determine whether its presence improves the performance of the recombinant VLPs vaccine. Full article

Laying additional clutches of eggs, or renesting, can provide birds with more opportunities to breed each season, ultimately increasing reproductive potential. This is important for long-lived species like cranes, that produce relatively few offspring annually. The reintroduced Eastern Migratory Population (EMP) of endangered Whooping Cranes relies on releases of captive-reared juveniles for population growth. Using long-term nest monitoring data, we assessed the renesting propensity of 105 unique pairs of Whooping Cranes during 2005–2024 (n = 359). We used a two-tiered analysis of binomial generalized linear mixed-effects models to evaluate the effects of 15 individual covariates, related to parental age or experience, nest management geography, or chronology. Overall, 37.3% of pairs renested following failed first nesting attempts. We documented higher renesting rates from breeding females that were older or had more years of nesting experience (37.1% increase for each unit increase in female age), pairs outside of the regions in which captive-reared cranes were released (264.0% increase in “other” region compared to Necedah), or that had nests fail earlier in the season (10.1% decline for each day later in the season a first nest failed). Additionally, when eggs were collected from first nests as a part of nest management, pairs were more likely to renest (69.4% renested) than if their nest failed naturally (27.3% renested). Low rates of natural reproduction limit growth rates in the EMP, so understanding effects of management actions and limitations on breeding are important conservation tools which can be applied to other endangered species. Full article

In order to protect endangered species, many zoos adopt diverse rearing models to achieve optimal conservation outcomes. This study employed metagenomic approaches to assess differences in the fecal microbiome of captive and semi-free-ranging ring-tailed lemurs (Lemur catta). The results show that captivity significantly altered the microbial community structure. The inter-individual variability in the microbial community within the captive-bred (CB) group was lower than that in the semi-free-ranging (FR) group, yet these individuals harbored a higher abundance of potential pathogens (Treponema_D). In contrast, microbial genera associated with fiber degradation and short-chain fatty acid production in the FR group were significantly elevated (Faecalibacterium, Roseburia, and Megamonas) as compared to the CB group. Environmental variations between the two rearing systems led to distinct profiles in microbial functions and carbohydrate-active enzyme gene composition. Notably, the FR group of lemurs exhibited an increased abundance of enzyme genes associated with the degradation of complex polysaccharides (cellulose, hemicellulose, and pectin), suggesting that their diet, rich in natural plant fibers, enhances the capacity of their gut microbiota to extract essential energy and nutrients. Conversely, the CB group displayed a more homogeneous microbial community with a higher prevalence of potential pathogens, implying that a captive lifestyle may negatively impact gastrointestinal health. These findings offer valuable insights into the influence of rearing conditions on gut microbial ecology and its potential implications for the health management of ring-tailed lemurs. Full article

Characterizing genetic diversity and structure is paramount in wildlife conservation management. Surprisingly, however, there are species that, despite being intensively managed, are largely overlooked in terms of genetic makeup. The Barbary partridge (Alectoris barbara), a medium-sized galliform native to northern Africa, is one such exemplary case. Since the early 2000s, a couple of breeding farms in Morocco have been operating using wild breeders. At that time, no genetic data were available for local wild populations, nor had the founders been genetically screened. After two decades, the degree of genetic diversity of wild Barbary partridge populations remains unknown. In this study, we genotyped the mitochondrial DNA control region (ca. 1000 bp) in wild and captive A. barbara populations from Morocco. Overall, we found a high and well-distributed genetic diversity, with a moderate differentiation between captive and wild populations likely attributable to either the sharing of widespread and allegedly ancestral haplotypes or the extensive release of farm-reared individuals. Nevertheless, the occurrence of private haplotypes across all the wild populations calls for separate management. A more comprehensive sampling and the use of genome-wide loci is advisable to achieve a thorough understanding of the genetic diversity of the Barbary partridge and define management units accordingly. Full article

The absence of standardized reference values for wild rodent species underscores the need for comprehensive hematological and biochemical profiles. This study established robust reference intervals (RIs) for Myocastor coypus raised in captivity, analyzing 30 nutrias (10 males, 10 females, and 10 juveniles) at a private farm in northeastern Romania. Leukocyte (WBC) counts averaged 11.85 (10³/µL) in males, 10.51 (10³/µL) in females, and 11.63 (10³/µL) in juveniles, indicating a consistent immune response. Hemoglobin was 11.81 g/dL in males, 11.97 g/dL in females, and 15.42 g/dL in juveniles, with hematocrit levels around 45%. Juveniles displayed higher MCH (38.59 pg) and MCHC (38.58 g/dL), reflecting growth-related adaptations. Platelet counts were lower in adults. Biochemical findings showed lower cholesterol (14.89 mg/dL) and higher glucose (236.26 mg/dL) in juveniles, indicating intense energy metabolism. Total proteins were significantly elevated in juveniles (33.17 g/dL). Creatinine and uric acid levels were higher in adults, although calcium exceeded reference ranges in males (12.04 mg/dL). Hepatic enzyme ALT was higher in males. These findings establish baseline health parameters for captive nutrias, aiding in monitoring and improving rearing practices. Full article

Fecal glucocorticoid metabolites have been used to evaluate responses to stressors in captive adult polar (Ursus maritimus) and grizzly (Ursus arctos horribilis) bears. However, there is a lack of physiological information on juvenile bears in captivity that could help expand the current understanding of their development and welfare. To address these questions, we tracked fecal glucocorticoid metabolites (FGMs) and behavior for 15 months in two polar bear cubs born at the Detroit Zoo, one who was mother-reared (Astra) and one who was hand-reared (Laerke), and one rescued grizzly bear cub (Jeb) reared at the Zoo. To allow access to a social partner during key developmental stages, Laerke and Jeb were housed together for eight months. Daily opportunistic samples were analyzed for fecal cortisol metabolites using an enzyme immunoassay and compared against behavior, social proximity, and environmental data gathered from 15 min focal observations. Based on a combination of generalized linear mixed models and Wilcoxon and Kruskal–Wallis tests, we found no significant variation in mean FGMs between Astra and Laerke, but both had significantly different mean FGMs compared to Jeb. We found that Laerke had higher FGM concentrations when she spent more time engaged in all-occurrence social negative behaviors and lower FGMs when engaged in social positive behaviors. For Jeb, FGMs were lower when in social proximity and higher following separation from Laerke. These data provide novel insights into the physiological states of juvenile bears during key stages and contribute to the growing body of information on polar and grizzly bear development. Full article

Fish exhibit diverse mechanisms of sex differentiation and determination, shaped by both external and internal influences, often regulated by distinct DNA methylation patterns responding to environmental changes. In S. senegalensis aquaculture, reproductive issues in captivity pose significant challenges, particularly the lack of fertilization capabilities in captive-bred males, hindering genetic improvement measures. This study analyzed the methylation patterns and transcriptomic profiles in gonadal tissue DNA from groups differing in rearing conditions and sexual maturity stages. RRBS (Reduced Representation Bisulfite Sequencing) was employed to detect notable methylation variations across groups, while RNA was extracted and sequenced for differential expression analysis. Our findings suggest that DNA methylation significantly regulates gene expression, acting as a mechanism that can both repress and enhance gene expression depending on the genomic context. The complexity of this epigenetic mechanism is evident from the varying levels of methylation and correlation rates observed in different CpGs neighboring specific genes linked to reproduction. Differential methylation comparisons revealed the highest number of differently methylated CpGs between maturation stages, followed by rearing conditions, and lastly between sexes. These findings underscore the crucial role of methylation in regulating gene expression and its potential role in sex differentiation, highlighting the complex interplay between epigenetic modifications and gene expression. Full article

The scarlet macaw (Ara macao) is a charismatic species that is native to Central and South America and commonly housed in captivity. Gaps in knowledge about these birds’ behavioral ecology in the wild hinders both in situ and ex situ management and conservation efforts for this species. We conducted seventeen days of observations of free-living scarlet macaws in two locations in Costa Rica, in February 2022, with the aims of (1) advancing our knowledge of this species’ natural behavioral ecology, and (2) generating data for comparison with captive macaws to help to inform their ex situ management (e.g., enclosure design and enrichment). Routes were walked within two locations—Bosque Escondido (BE), release area for captive-bred reintroduced individuals and no extant wild population, and Punta Leona (PL), an area of natural habitat within a resort inhabited by wild scarlet macaws—and focal interval sampling of multiple scarlet macaws in a group was used to record behavior and space use. The macaws at both locations were generally active, spent most of their time high in the tree canopy, relied on climbing to move within it, and used a wide variety of supports. The macaws at PL spent significantly more time feeding and locomoting, and less time perching, than those at BE, possibly due to differences in resource availability, rearing conditions, and age. Furthermore, the wild scarlet macaws at PL exhibited a variety of foraging strategies to acquire and manipulate food items within the tree canopy, including frequent use of their feet during manipulation. Despite limitations caused by a small sample size, a short period of observations, and differences between the two populations observed, this study provides insights into the behavioral ecology of scarlet macaws in the wild, which can be used for behavioral assessments of captive macaws while informing their ex situ management, with applications to animal welfare and captive breeding programs. Full article