BMC Zoology最新文献

Background: The development of larger monogeneans and their survival on more active hosts is thought to have led to the emergence of haptoral suckers and, in some instances, anchors, enabling a more stable anchorage. Because of their strict host specificity, the morphological variation of anchors in genus Diplorchis (Monogenea: Polystomatidae) may be determined to a large degree by adaptation to the host species, its habitat and ecological environment to ensure stable attachment.

Methods: In this study, we estimated the interspecific and intraspecific differences of haptoral anchors and other morphological characteristics in six recorded species of Diplorchis and one unidentified species parasitizing Sylvirana maosonensis (Bourret, 1937) in China using geometric morphometrics.

Results: Geomorphometric analyses revealed significant differences in the shape and size of the anchors among the seven species, indicating that the morphological differences in anchors can be used as a basis for species identification within the genus Diplorchis. In addition, we found that the same Diplorchis species collected from different localities not only differed significantly in anchor form, but also in body size and haptor size, as well as haptoral sucker size. This may reflect the effect of different habitat environments on biological/behavioral activities of the same host, thus further affecting the stable attachment of flatworms within species. Interestingly, in two species collected from the same localities, we found no significant differences in anchor or sucker size, while body size and haptor size all differed significantly. Meanwhile, the significant differences in anchor shape may suggest that the attachment mechanism of the different Diplorchis species is related to the variation in anchor shape.

Conclusions: From the perspective of morphological adaptation to the environment, the study not only indicated that the morphological variation of Diplorchis anchors can be used as an auxiliary tool to distinguish species, but also found that the morphological differences in the anchors were influenced by factors such as host species, habitat and ecological environment. This may provide a basis for a better understanding of host-parasite interaction.

Background: Spiders are highly adaptable hunters found in nearly all terrestrial ecosystems and play an important role in biological control by preying on pest insects. Spiders' body size and shape are vital for their survival, particularly in prey capture, and these morphological features are often utilized in cladistic analyses. This study employed geometric morphometrics to investigate prosoma shape and size variations between two populations of Nigma conducens spiders and between sexes within each population. Principal Component Analysis (PCA) explored shape variation, while Canonical Variate Analysis (CVA) compared shape differences between populations and sexes. Multivariate regression analysis was used to check for allometry.

Results: MANOVA results revealed significant shape variations in spider prosoma between the two populations and between sexes, though the degree of these differences was small. The considerable overlap in individual shapes between populations may indicate a response to microhabitat similarity. Additionally, sexual dimorphism was observed in the prosoma shape of N. conducens, likely due to sexual selection or adaptive divergence related to different microhabitats. Size differences between sexes were insignificant in either population, particularly in the first, suggesting that prosoma size does not contribute to reproductive success. Moreover, the non-allometric relationship indicated that shape variations between the populations were independent of size.

Conclusion: Overall, these findings highlight the complexity of morphological adaptations in N. conducens in response to ecological pressures and sexual selection.

Background: The Mandarin Duck (Aix galericulata) has recently been recognized as a partial migrant in China. The resident population of this species is primarily recorded in southern China, which is not only the traditional wintering range, but also the southernmost breeding sites. However, little information is known about their abundance and habitat requirements during breeding periods. This study provided the first report on the structure of the resident population and the habitat used during the post-breeding period at a tributary of the Wu River in Guizhou Province, Southwest China, which was one of the recently identified breeding sites within the traditional wintering range.

Results: A total of 36 Mandarin ducks were recorded among 15 sites, and the mean population density was estimated to be 3.51 ± 3.06 ind./km. The observed adults sex ratio of males to females was 0.44:1. At the microhabitat scale, the results of logistic regression models indicated that the key habitat variables included the distance to the nearest forest edge (dist.forest), opening extent of valley (deg.valley) and distance to the nearest human settlement (dist.settlement). The Mandarin Duck preferred to use foraging sites near forest edges, where dense marginal growth of woodland and shrubs was present.

Conclusion: These findings suggested that dense vegetation along rivers could play a positive, important role in habitat use by the resident population of Mandarin ducks. Compared to traditional breeding ranges, both adults and ducklings of this species were more likely to experience human-related disturbances due to the limited availability of ancient trees outside villages. This information will contribute to provide baseline knowledge on the resident population of Mandarin ducks, and enhance understanding of the causes and consequences of breeding partial migration.

This field study investigated the population structure, distribution pattern and habitat utilization of Yellow-wattled Lapwings. The line transect method was used to estimate the density of Yellow-wattled Lapwings. An average of 394 individuals including 77 chicks of Yellow-wattled Lapwings have been registered with an average density of 38 birds per km. The outcome of the GLM analysis exhibited, that Bakshi Ka Talab had the highest lapwing count while, Malihabad had the lowest lapwing count. A significant lapwing count in the year 2021 was confirmed. The winter season had the lowest lapwing counts, whereas the summer season had the highest values. Moreover, the largest lapwing counts were estimated in uncultivated while, the lowest lapwing count was documented in river habitat types. There was a significant difference in the mean flock size across the seasons and the habitat types. Being sighted in flocks of various sizes the distribution pattern was found to be clumped in Yellow-wattled Lapwings. The results of the factorial ANOVA showed a significant difference in the habitat utilization of Yellow-wattled Lapwings across study sites, years, seasons and habitat types. Uncultivated habitat types were the most utilized habitat types during summer seasons.

Background: The crested ibis, a species that relies on wetland ecosystems for survival, was once found throughout East Asia but has declined to near extinction in Korea, Russia, and Japan, except China. Artificial propagation of seven individuals found in Yangxian, Shaanxi Province, China has resulted in a stable population. Furthermore, South Korea and Japan are working on restoring populations through donations from China. Artificial propagation began in 2008, and in 2019, 40 individuals born between 2014 and 2018 were released into the natural habitat for the first time. We conducted this study to analyze the habitat environment, home range, and habitat usage patterns of a 2016-born male and a 2017-born female who attempted to reproduce naturally for the first time.

Results: After forming a breeding pair on April 3, 2020, the pair made two breeding attempts, built a nest in Pinus densiflora, and succeeded in hatching the chicks, but failed to raise them. The home range analysis showed that the area was 1.777-2.425 km² for MCP 100%, and 0.347-2.085 km² for 95% KDE. Meanwhile, the core habitat ranged from 0.007 to 0.296 km² (KDE 50%), indicating differences depending on the time of year and the individual being studied. Breeding pairs were estimated to spend over 50% of their recorded occurrences within 50 m during nesting for incubation, resting, and other activities. They mainly used in paddy fields, but from April to June, when onions and garlic were growing, they searched for food in fields, cemeteries, reservoirs, and other areas.

Conclusion: Breeding pairs have increasingly become more active near the nest, and Changnyeong-gun, where they were released, has large agricultural land suitable for crested ibis habitat. However, there is a problem that during the breeding season from April to June, most paddy fields are maintained as garlic and onion fields, which are then converted back for rice cultivation from May to June through double-cropping. Accordingly, for stable laying and rearing, it is necessary to contemplate how to maintain rice paddies, which serve as feeding grounds in the core habitats.

Background: Kuruma shrimp (Marsupenaeus japonicus) is a commercially important crustacean and a valuable global food source. This study employed scanning electron microscopy (SEM) to explore the morphology and morphometric features of the Marsupenaeus japonicus cephalothoracic structures, including antennules, antennas, scaphocerite, rostrums, and eye stalks. The primary focus was on understanding the role of each part, especially through the examination of setae, which are crucial for chemoreception and defense. Additionally, energy dispersive X-ray spectroscopy (EDX) analysis was utilized to identify the elemental composition of these structures.

Material and methods: The samples from the heads of fifteen Marsupenaeus japonicus were studied by gross morphology and morphometry, SEM, and EDX analysis. This study is the first to integrate both SEM and EDX techniques for a detailed analysis of these cephalothoracic structures, offering an innovative approach to understanding both morphological and elemental characteristics.

Results: Marsupenaeus japonicus exhibited two antennules and two antennae. The antenna featured four basal segments: basicerite, ischiocerite, merocerite, and carpocerite, each with distinctive articulations and setae distribution. The antennule, with three segments covered by plumose setae, displayed curved cone-shaped flagellae. The scaphocerite, resembling a paddle, showcased plumose setae, while the rostrum exhibited dorsal and ventral spines, lateral grooves, and unique setal arrangements. Setal measurements across structures revealed diverse lengths and widths, indicating functional specialization. The compound eyes were connected to an optic stalk adorned with plumose setae. EDX analysis revealed higher percentages of calcium and phosphorus in the spear-like structures of the scaphocerite, rostrum, and antenna, respectively.

Conclusion: This investigation provides a thorough examination of the intricate morphological features of the cephalothoracic region of Marsupenaeus japonicus, shedding light on its sensory and defensive capabilities. The novel application of both SEM and EDX not only deepens our insights into these structures but also lays the groundwork for future studies using this dual approach to explore crustacean morphology, with potential advantages for sustainable aquaculture and the conservation of marine ecosystems.

Grant's gazelles (Nanger granti) are classified as of least concern by the IUCN, although their number is declining due to several factors. A few research studies have been conducted on Grant's gazelle in Ethiopia. Thus, the present study was carried out to determine the population size and habitat association of Grant gazelle in the Ene Forest of western Ethiopia, comprising the dry and wet seasons. The study area was stratified into four habitats: woodland, mixed woodland, riverine forest, and grassland habitats. The data were collected using the direct observation technique. The data were analyzed using descriptive statistics and Pearson's chi-square (χ²) test. The average estimated Grant gazelle population was 136 ± 23 individuals, with a density of 9/km². The adult male-to-adult female sex ratio was 1:1.40 and 1:1.26 during the wet and dry seasons, respectively. The largest herd size (N = 6) was observed during the wet season, and the smallest (N = 4) was observed during the dry season. The highest numbers of Grant gazelles were observed in the grassland habitat during the wet season and in the woodland during the dry season. More Gazelles (N = 65) were observed in the woodland habitat compared to the other habitat types. The continued existence of the Grant's gazelle population in the area and the suitability of the environment depend significantly on ongoing assessments of habitat change and management intervention.

Background: The Yangtze finless porpoise (Neophocaena asiaeorientalis asiaeorientalis) is critically endangered and has suffered from extensive habitat loss and fragmentation. Knowledge of its habitat preference could assist the conservation of the species and associated ecosystem. In the present study, spatiotemporal variations and driving factors of habitat use of a Yangtze finless porpoise population were studied in a 30-km section of the Yangtze mainstream. Seasonal variation in porpoise occurrences was observed based on visual surveys conducted from 2022 to 2023, with five surveys during the dry season and seven surveys during the wet season. Biological and environmental factors were synchronously sampled in both seasons. The maximum entropy model (MaxEnt) was applied to get the effects of biological and environmental variables on porpoise habitat preference.

Results: Within the study area, high-suitability habitats of the finless porpoises accounted for 19.0% and 15.4% of the area during the dry and wet seasons, respectively. The high-suitability habitat shifted from the mainstream in the dry season to the sandbar head and tributary area in the wet season. In the dry season, variables influencing the distribution were phytoplankton biomass, water velocity, and zooplankton biomass, which contributed 97.05% variation in the MaxEnt modeling. In the wet season, water depth, surface water temperature, and zooplankton biomass accounted for 97.69% variation of the distribution. Above results highlight that food availability plays an important role in porpoises distribution regardless of seasons, particularly in the dry season. This is because plankton is the primary food source for filter-feeding and omnivorous fish, especially those in the upper-middle layer which are frequently preyed on by finless porpoises.

Conclusion: Suitable areas for finless porpoises, particularly those with high suitability, differed significantly across seasons at a fine-scale in the Yangtze mainstream. Seasonal variations in habitat were driven by different factors. But food availability plays an important role in porpoises distribution regardless of seasons, particularly in the dry season. These results suggest prioritizing conservation of the finless porpoise in the dry season when fish resources are relatively scarce. Measures including monitoring and evaluating prey resources should be considered. More attention should also be paid on management of shipping in the dry season given that the high-suitability habitat of the finless porpoises shifts to the mainstream.

Background: The tropical gar (Atractosteus tropicus), a member of the Lepisosteidae family, is native to regions extending from southeastern Mexico to southern Costa Rica. This species serves as a unique bridge between tetrapods and teleosts due to its phylogenetic position, slow evolutionary rate, dense genetic map, gene similarities with humans, and ease of laboratory cultivation. As a taxonomic sister group to teleosts like the zebrafish (Danio rerio), known for its high regenerative capacity, it remains unclear whether the tropical gar shares a similar ability for regeneration.

Results: This study aims to elucidate the caudal fin regeneration process in tropical gar through skeletal and histological staining methods. Juvenile specimens were observed over a two-month period, during which they were fed brine shrimp, and anesthetized with 1% eugenol for caudal fin amputation. Samples were collected at various days post-amputation (dpa). Alcian blue and alizarin red staining were used to highlight skeletal regeneration, particularly the formation of new cartilage, while histological staining with hematoxylin and eosin was performed to observe tissue regeneration at the amputation site.

Conclusions: The findings reveal a remarkable ability for caudal fin regeneration in juvenile tropical gar. Given the Garfish evolutionary relationship with teleosts, this opens new avenues for research into tissue regeneration across different groups of Actinopterygii.