Zoological Studies最新文献

Twin-tail ornamental goldfish have a bifurcated caudal fin with a morphology that is extremely divergent from the conventional body plan of the vertebrates. Here, we investigate the musculoskeletal histology of this bifurcated caudal fin. From some of the investigated twin-tail goldfish, we found a twin-tail goldfish specific muscle (hereafter referred to as the "medial caudal muscle") between left and right bifurcated caudal fin skeletons. Our immunohistochemical analyses revealed that the medial caudal muscle showed laterally biased distribution patterns of the slow and fast muscle fibers. Similar distribution patterns were also commonly observed in several deep muscles of wild-type goldfish as well as zebrafish, suggesting that these muscle fiber distribution patterns are formed by the same molecular developmental mechanisms even though their morphologies are highly diverged. These findings provide empirical evidence to consider how the histological features of a newly emerged morphology are influenced by selective pressures and pre-existing developmental mechanisms.

Biological specialization plays a central role in species coexistence. While many studies focus on hummingbird pollination, research on the effects of morphological traits of both hummingbirds and plants on the specialization of interaction networks remains scarce. In this study, we aim to address the following questions: i) does the dominance of ornithophilous plant species increase the specialization of hummingbird-plant interaction networks?; ii) do ornithophilous plants exhibit a greater diversity of interactions with hummingbirds compared to non-ornithophilous plants?; iii) do the beak size and body weight of hummingbirds influence the diversity of their interactions? Research was conducted on hummingbird-plant interactions in the Neotropical region. We investigated hummingbird-plant interactions in the Neotropical region by compiling 24 networks from the literature, comprising 1,182 interactions between 34 hummingbird species and 326 plant species. We found no effect of ornithophilous plant dominance on the structure (connectance and modularity) of the networks. However, species-level interactions were influenced by morphological attributes of both plants and hummingbirds. Interaction similarity among plant species was greater for ornithophilous plants than for non- ornithophilous plants. Additionally, beak size positively influenced the degree and specialization of hummingbird interactions. Our findings demonstrate that the morphological characteristics of hummingbird and plant species directly influence the diversity of interactions in Neotropical hummingbird-plant networks and species specialization.

This study aimed to establish reference intervals for red and white blood cell counts, hematocrit levels, mean corpuscular volume, and 25 key plasma biochemistry parameters in captive and wild whale sharks (Rhincodon typus). Blood samples were collected from the caudal vein (CV) and dorsal cutaneous vein (DCV) of 30 wild sharks caught in fixed nets off the Kochi Prefecture coast, Japan, and from 24 captive sharks between 2007-2023. Samples were obtained from restrained captive and wild sharks as well as unrestrained captive sharks trained for husbandry. Comparative analyses considered three factors: captivity status (wild vs. captive sharks under restraint), blood sampling sites (CV vs. DCV under restraint), and handling methods (DCV sampling under restrained vs. unrestrained conditions). Analysis of captivity status revealed significant differences in 12 of 29 parameters, with triglyceride levels significantly lower in wild sharks, possibly indicating nutritional deficiencies due to their prolonged migrations. Comparisons of blood sampling sites revealed significant differences in 11 parameters, including red and white blood cell counts and hematocrit levels, with most CV-derived parameters being higher than those from the DCV. A strong correlation (r > 0.7) was found between the CV and DCV for 19 parameters, indicating predictive values between these vessels. Additionally, the relationship between RBC, Ht, and MCV indicates that the RBC and MCV results may not be entirely reliable and should therefore be interpreted with caution. In the handling method comparison, eight parameters exhibited significant differences; specifically, aspartate aminotransferase, ammonia, and creatine phosphokinase levels were likely influenced by stress effects, including restraint-induced muscle damage. These findings emphasize the importance of unrestrained blood collection, facilitated through husbandry training, for accurate blood parameter evaluations. Integrating statistical results across the three studied factors allowed for the establishment of reference intervals, means, and medians for whale sharks, contributing to health management in captive sharks and conservation in wild populations.

Møller and Erritzøe (2017) reported that birds killed by collisions with vehicles had on average relatively smaller brains than birds killed by other causes, which were not identified. Despite concerns about the method used to assess brain mass, we reanalyzed the published data of Møller and Erritzøe (2017) after excluding extraneous species and confirmed a subtle tendency for birds killed by vehicular collision to have somewhat small brains. Some groups of birds (owls, hawks, garden birds and migratory species) did not reflect the overall result. Surprisingly there was no effect of age or sex, whereas one would expect inexperienced immature birds and females in breeding condition to be vulnerable. Overall, plots of brain mass in birds killed by vehicular collisions and other causes greatly overlap, and in some species, individuals killed by collisions have relatively larger brains. That is, the tendency for birds hit by vehicles to be relatively smaller brained is not universal, nor in any species is there an absolute difference in brain size between the two categories. It is possible that in the short time birds have interacted with moving vehicles that selection has acted on brain size to avoid collisions, although we suggest that slightly larger brains might represent an innate tendency to avoid rapidly approaching objects. An interesting question from their study is what was the cause of mortality in the birds not hit by vehicles. Likely sources of mortality of birds post-nestling stage include depredation (natural and house cats) and collisions with windows and other human structures. In fact, relatively large-brained birds might be more susceptible to collisions with windows or being caught by cats (i.e., the other sources of mortality), for which having a relatively larger brain would not appear to mitigate these sources of mortality.

Temperature is one of the main abiotic factors that influence the growth, reproduction, food availability, distribution, and survival of many species of marine ectotherms. Megastraea undosa and Megathura crenulata are gastropod mollusks with economic, commercial, and biomedical importance that are part of the kelp forest community in the temperate waters of the northern Pacific of Mexico. As knowledge about the thermal biology of these two species is scarce, this study aimed to determine the effect of different acclimation temperatures on the thermal biology and metabolic scope of these two species. 120 M. undosa juveniles were collected from the wild and acclimated to four temperatures (13, 16, 19, and 22°C ± 1°C), while 90 M. crenulata juveniles were cultured in an aquaculture facility (Stellar Biotechnologies, Inc) and acclimated to three temperatures (17, 20, and 23°C ± 1°C). Subsequently, experiments were performed to determine the thermal tolerance, thermal window, thermal safety margin, future thermal safety margin, and thermal metabolic scope of these species. The thermal tolerances of both species were relatively similar (M. undosa juveniles: CT_max = 25.3, 21.0, 25.4 and 27.4°C, CT_min = 6.0, 9.2, 16.3 and 17.3°C; M. crenulata juveniles: CT_max = 27.7, 28.1 and 28.8°C, CT_min = 11.2, 12.1 and 14.7°C). Both species had a small thermal window area (M. undosa: 77.2°C²; M. crenulata: 65.25°C²). The values of the thermal safety margin and the future thermal safety margin of both species were lower during the summer than winter. The optimal temperature proxies of M. undosa and M. crenulata juveniles were 16 and 20°C, respectively. This study shows that the two species of marine gastropods could be moderately affected by ocean warming, being forced to modify their current distribution patterns. The data on thermal limits and optimal temperatures can be used to initiate and maximize the cultivation of both species, which would also help mitigate the impact of overfishing on natural populations.

Terrestrial isopods are important to forest soils, breaking down decaying plant material and aiding in nutrient recycling. Despite their ecological significance, studies on their diversity and dynamics in Neotropical dry forests are limited. This research investigated the seasonality of the alpha and beta diversity of terrestrial isopod assemblages in a protected fragment of Tropical Dry Forest in the Colombian Caribbean. We sampled isopods in 1 m2 units of litter, and recorded soil and litter temperatures, and moisture during twelve field trips conducted between June 2018 and March 2019 in rainy, transition, and dry climatic seasons. A total of 867 individuals belonging to four families, six genera, and eight species were collected. Alpha diversity did not show significant differences across seasons. However, abundance was significantly influenced by seasonality, soil temperature, litter temperature, and soil moisture. Moreover, species richness was affected by soil moisture and litter temperature. Our results highlight pronounced seasonality in the isopod assemblage, characterized by balanced variation in beta diversity, with higher abundance during the transition and rainy seasons. The observed increase in the variables, correlated with higher total beta diversity, underscores their role as drivers of seasonal dynamics in assemblage structure. Soil temperature and moisture significantly influenced balanced variation component of beta diversity. The identified seasonal pattern likely results from the historical adaptive processes of these species to the conditions of the tropical dry forest. Nonetheless, effective conservation strategies are essential to mitigate the impacts of climate change on edaphic arthropod assemblages in this ecosystem.

We describe the ostracod Lissostrandesia fonticola gen. et sp. nov. in the subfamily Cypricercinae McKenzie, 1971, collected from six rheocrenic springs in Japan. The populations sampled were separated by up to 1000 km, and some of them by one or two marine straits, which comprise significant barriers for freshwater animals. Lissostrandesia differs from the other 13 cypricercine genera in (1) lacking a groove and inner list on the anterior inner margin of the left valve; (2) having b and d setae on the fifth limb; (3) having d₁ and d₂ setae on the sixth limb; (4) having a stout attachment of the caudal ramus; (5) having a Triebel's loop on the dorsal branch of the attachment; and (6) having a long free ventral branch, its length more than twice its width, and (7) having a free dorsal branch contributing to a tip on Triebel's loop. These differences were enough to warrant establishment of a new tribe, Lissostrandesiini, to accommodate the new genus. We present a key to the genera in Cypricercinae. The maximum p-distance for the mitochondrial cytochrome c oxidase subunit I (COI) gene among six local populations was 0.662%, a low value indicative of conspecificity. In addition, four populations with sample sizes of 13-21 individuals shared two main COI haplotypes, indicating high apparent connectivity. A trend of decreasing genetic diversity from south to north suggests L. fonticola has had a longer history on Honshu Island and dispersed northward from there. Using the 16S rRNA gene as a marker, we detected the endosymbiotic bacterium Cardinium, a group of "reproduction-manipulating" bacteria, in five populations, suggesting that L. fonticola is parthenogenetic. Passive dispersal is the most likely explanation for the broad distribution of this species across strong geographic barriers.

To identify the worldwide genetic structure, gene flow, and diversity of Culex quinquefasciatus, we conducted phylogeographic and population genetics analyses utilizing publicly available mtDNA sequences. Therefore, the aim of this study was to investigate the genetic structure and diversity of natural populations of C. quinquefasciatus worldwide, using available genetic data reflecting its natural distribution. Our study focused on the cytochrome c oxidase subunit I (COI) gene, mirroring the species' distribution pattern. We examined COI gene sequences from C. quinquefasciatus populations across Asia (n = 1,698), America (n = 334), Africa (n = 30), Oceania (n = 21), and Europe (n = 1), identifying 69 haplotypes. Genetic links were observed between Asian populations and those from other continents. Global genetic diversity was 0.531, varying from 0.095 in Oceania to 0.648 in South America. Neutrality tests indicated demographic expansions at the continental level in the Americas, North America, and Asia, as well as in some countries within these regions. In contrast, at both global and continental levels (South America, Oceania, and Africa), and in most countries within these continents, neutral populations were observed. AMOVA revealed genetic structuring among and within countries, with no genetic isolation observed (R ² = 0.03144; p > 0.05). Despite lower genetic diversity, Asian populations facilitated gene flow with other continents, suggesting a possible native origin of the species in Asia. The dispersal of this mosquito to new regions, coupled with its ability to transmit various arboviruses, underscores its significance as a potential public health threat.

Over 110 specimens of xanthid crabs collected from rocky intertidal habitats in Taiwan and its offshore islands over the past 25+ years were examined in the present study. As a result, 24 species were recognized, distributed across seven subfamilies and 16 genera including one new genus record (i.e., Lioxanthodes Calman, 1909) for Taiwan. Of these recognized species, 14 have been previously reported from Taiwan, whereas five are new records for Taiwan, one new to science, and four unnamed species. The five newly recorded species are Chlorodiella barbata (Borradaile, 1900), Etisus frontalis (Dana, 1852), Lioxanthodes alcocki Calman, 1909, and Macromedaeus quinquedentatus (Krauss, 1843), and Pilodius nigrocrinitus Stimpson, 1859. The new species, Cyclodius taiwanensis sp. nov., is herein described.

Echinostylinos comprises 11 species, among which a single, recently reported record for the South Atlantic. Here we propose two further new species from this ocean basin. Echinostylinos iatapiuna sp. nov. (2300‒3200 m depth, São Paulo Ridge) and Echinostylinos abyssalis sp. nov. (4008 m depth, São Paulo Ridge). The latter pushes the genus' known distribution into the abyssal zone for the first time. The morphologic variation observed in the microscleres of Echinostylinos is briefly discussed, motivating our proposal to transfer Echinostylinos glomeris (Topsent, 1904, as Esperiopsis) to Abyssocladia, a stipitate or likely so, which compound with chelae of cleistochelae morphology to point to the latter genus as its best assignment. An identification key for Echinostylinos spp. is offered (now 13). In addition, a new species of Chondrocladia is described, namely Chondrocladia (Chondrocladia) trisigmata sp. nov. (3250-3270 m depth, south of the Vitória-Trindade seamounts' chain). Finally, some biogeographic considerations are made about abyssal sponge records in the South Atlantic.