Pub Date : 2025-12-14DOI: 10.1016/j.zool.2025.126316
Reuven Yosef , Malamati A. Papakosta , Dimitrios E. Bakaloudis , Jakub Z. Kosicki , Christos G. Vlachos
Egg size is a key determinant of reproductive success in birds, influencing nestling growth, survival, and overall fitness. For Lesser Kestrels Falco naumanni, a small raptor often supported by nest-box programs, we hypothesized that female condition would significantly predict egg size, with higher-quality females producing larger eggs. Thus, over four breeding seasons, we investigated the influence of female condition, expressed as the Scaled Mass Index (SMI), and clutch size on egg dimensions (length, breadth, and volume) in a nest-box population in central Greece. We found that female condition significantly and positively affected both egg breadth and volume but did not influence egg length, and clutch size had no discernible effect on any egg dimension. Among the traits measured, breadth exhibited the highest repeatability, suggesting a stronger genetic component, whereas length and volume were more sensitive to environmental factors. Our findings suggest that conservation efforts should prioritize maintaining or improving female body condition – through, for example, ensuring high habitat quality, adequate food availability, and minimizing stress – to support optimal reproductive investment by female Lesser Kestrels in nest-box populations.
{"title":"Impact of Female Condition on Egg Size in Lesser Kestrels (Falco naumanni)","authors":"Reuven Yosef , Malamati A. Papakosta , Dimitrios E. Bakaloudis , Jakub Z. Kosicki , Christos G. Vlachos","doi":"10.1016/j.zool.2025.126316","DOIUrl":"10.1016/j.zool.2025.126316","url":null,"abstract":"<div><div>Egg size is a key determinant of reproductive success in birds, influencing nestling growth, survival, and overall fitness. For Lesser Kestrels <em>Falco naumanni</em>, a small raptor often supported by nest-box programs, we hypothesized that female condition would significantly predict egg size, with higher-quality females producing larger eggs. Thus, over four breeding seasons, we investigated the influence of female condition, expressed as the Scaled Mass Index (SMI), and clutch size on egg dimensions (length, breadth, and volume) in a nest-box population in central Greece. We found that female condition significantly and positively affected both egg breadth and volume but did not influence egg length, and clutch size had no discernible effect on any egg dimension. Among the traits measured, breadth exhibited the highest repeatability, suggesting a stronger genetic component, whereas length and volume were more sensitive to environmental factors. Our findings suggest that conservation efforts should prioritize maintaining or improving female body condition – through, for example, ensuring high habitat quality, adequate food availability, and minimizing stress – to support optimal reproductive investment by female Lesser Kestrels in nest-box populations.</div></div>","PeriodicalId":49330,"journal":{"name":"Zoology","volume":"174 ","pages":"Article 126316"},"PeriodicalIF":1.6,"publicationDate":"2025-12-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145760663","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-11-01DOI: 10.1016/j.zool.2025.126305
Quang Minh Dinh, Vuong Van Ly, Ton Huu Duc Nguyen
Burrowing behavior in mudskippers represents a key adaptation to intertidal environments, providing shelter from predators, buffering against temperature and salinity fluctuations, and serving as breeding sites. Despite its ecological significance, little is known about the burrow morphology of Scartelaos histophorus, a large mudskipper species widely distributed throughout Southeast Asia. This study investigated the burrow morphology of the mudskipper S. histophorus in the intertidal mudflats of Hiep Thanh, Ca Mau, Vietnam. The study was designed under the hypothesis that the burrow morphology of S. histophorus varies according to environmental parameters such as salinity, pH, and temperature, reflecting adaptive responses to intertidal conditions. A total of 64 burrows were cast and analyzed, revealing four structural types: L-shaped (57.81 %), U-shaped (23.44 %), J-shaped (6.25 %), and complex forms (12.50 %). The number of burrow openings ranged from 1 to 4, while chambers varied from 0 to 5, indicating structural variability. Burrow dimensions showed considerable variability, with total length ranging from 6 to 142 cm and burrow weight from 12.70 to 429.66 g, while depth and mouth diameter were relatively stable. Statistical analyses revealed significant differences in burrow size among structural types, with U-shaped and complex burrows generally larger than L- and J-shaped forms. Environmental variables, including pH, temperature, and salinity, were also significantly associated with burrow characteristics. Direct behavioral observations, including sediment excavation, entrance maintenance, air-bubble injection, and courtship displays, confirmed the ecological functions of different burrow types. These findings demonstrate that S. histophorus exhibits flexible burrowing strategies shaped by both environmental conditions and reproductive requirements, underscoring their adaptive role in sustaining intertidal biodiversity and contributing to a broader understanding of coastal ecosystem resilience at a global scale.
{"title":"Burrow morphology and environmental–behavioral correlates of Scartelaos histophorus in intertidal mudflats of Ca Mau, Vietnam","authors":"Quang Minh Dinh, Vuong Van Ly, Ton Huu Duc Nguyen","doi":"10.1016/j.zool.2025.126305","DOIUrl":"10.1016/j.zool.2025.126305","url":null,"abstract":"<div><div>Burrowing behavior in mudskippers represents a key adaptation to intertidal environments, providing shelter from predators, buffering against temperature and salinity fluctuations, and serving as breeding sites. Despite its ecological significance, little is known about the burrow morphology of <em>Scartelaos histophorus</em>, a large mudskipper species widely distributed throughout Southeast Asia. This study investigated the burrow morphology of the mudskipper <em>S. histophorus</em> in the intertidal mudflats of Hiep Thanh, Ca Mau, Vietnam. The study was designed under the hypothesis that the burrow morphology of <em>S. histophorus</em> varies according to environmental parameters such as salinity, pH, and temperature, reflecting adaptive responses to intertidal conditions. A total of 64 burrows were cast and analyzed, revealing four structural types: L-shaped (57.81 %), U-shaped (23.44 %), J-shaped (6.25 %), and complex forms (12.50 %). The number of burrow openings ranged from 1 to 4, while chambers varied from 0 to 5, indicating structural variability. Burrow dimensions showed considerable variability, with total length ranging from 6 to 142 cm and burrow weight from 12.70 to 429.66 g, while depth and mouth diameter were relatively stable. Statistical analyses revealed significant differences in burrow size among structural types, with U-shaped and complex burrows generally larger than L- and J-shaped forms. Environmental variables, including pH, temperature, and salinity, were also significantly associated with burrow characteristics. Direct behavioral observations, including sediment excavation, entrance maintenance, air-bubble injection, and courtship displays, confirmed the ecological functions of different burrow types. These findings demonstrate that <em>S. histophorus</em> exhibits flexible burrowing strategies shaped by both environmental conditions and reproductive requirements, underscoring their adaptive role in sustaining intertidal biodiversity and contributing to a broader understanding of coastal ecosystem resilience at a global scale.</div></div>","PeriodicalId":49330,"journal":{"name":"Zoology","volume":"173 ","pages":"Article 126305"},"PeriodicalIF":1.6,"publicationDate":"2025-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145433553","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-11-01DOI: 10.1016/j.zool.2025.126303
Marcelo F. Bonino, Félix B. Cruz
Understanding what determines species distribution is a central goal in biogeography and macroecology, particularly in the context of ongoing environmental change. In this study we explored how intrinsic (biological) and extrinsic (environmental) factors influence the distribution of Liolaemus lizards occurring east of the Andes, and evaluated the extent to which their distribution patterns support Rapoport's rule. We analyzed 38 species, spanning Argentina from 52°S to 23°S, covering about 50 % of the genus distribution from sea level to 4300 masl. We used two main approaches, polygons and ecological niche models (ENMs), to evaluate the role of intrinsic factors such as critical thermal minimum (CTmin), thermal tolerance range, body size, and diet; and extrinsic factors including temperature, precipitation, elevation, and vegetation index. Our results show that CTmin is a strong predictor of range size under the ENMs approach, suggesting that greater cold tolerance is associated with broader distributions. Under the polygon approach, broader ranges correlated with colder, drier climates with pronounced seasonality. Although diet showed a weak tendency for narrower ranges in herbivorous species, it was a poor predictor overall. Thermal tolerance range, expected to increase with latitude under the climatic variability hypothesis, did not show a significant association with range size, and thus Rapoport’s rule was not supported. Furthermore, taxonomic uncertainties may obscure biogeographic patterns, particularly in widely distributed species that might represent species complexes not yet formally described. These findings highlight the combined role of biological and environmental factors, challenge the general applicability of Rapoport’s rule in Liolaemus, and underscore cold tolerance as a key distribution driver.
{"title":"Biological and environmental drivers of Liolaemus species distribution: A case story East of the Andes","authors":"Marcelo F. Bonino, Félix B. Cruz","doi":"10.1016/j.zool.2025.126303","DOIUrl":"10.1016/j.zool.2025.126303","url":null,"abstract":"<div><div>Understanding what determines species distribution is a central goal in biogeography and macroecology, particularly in the context of ongoing environmental change. In this study we explored how intrinsic (biological) and extrinsic (environmental) factors influence the distribution of <em>Liolaemus</em> lizards occurring east of the Andes, and evaluated the extent to which their distribution patterns support Rapoport's rule. We analyzed 38 species, spanning Argentina from 52°S to 23°S, covering about 50 % of the genus distribution from sea level to 4300 masl. We used two main approaches, polygons and ecological niche models (ENMs), to evaluate the role of intrinsic factors such as critical thermal minimum (CTmin), thermal tolerance range, body size, and diet; and extrinsic factors including temperature, precipitation, elevation, and vegetation index. Our results show that CTmin is a strong predictor of range size under the ENMs approach, suggesting that greater cold tolerance is associated with broader distributions. Under the polygon approach, broader ranges correlated with colder, drier climates with pronounced seasonality. Although diet showed a weak tendency for narrower ranges in herbivorous species, it was a poor predictor overall. Thermal tolerance range, expected to increase with latitude under the climatic variability hypothesis, did not show a significant association with range size, and thus Rapoport’s rule was not supported. Furthermore, taxonomic uncertainties may obscure biogeographic patterns, particularly in widely distributed species that might represent species complexes not yet formally described. These findings highlight the combined role of biological and environmental factors, challenge the general applicability of Rapoport’s rule in <em>Liolaemus</em>, and underscore cold tolerance as a key distribution driver.</div></div>","PeriodicalId":49330,"journal":{"name":"Zoology","volume":"173 ","pages":"Article 126303"},"PeriodicalIF":1.6,"publicationDate":"2025-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145433555","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-11-01DOI: 10.1016/j.zool.2025.126306
Mohamed A.M. Alsafy , Samir A.A. El-Gendy , Ahmed M. Rashwan , Samar M. Ez Elarab , Manal Seif , Neveen E.R. El-Bakary , Ahmed A. El-Mansi , Mamdouh B. Eldesoqui , Amal F. Dawood , Catrin S. Rutland , Valentina Kubale
Understanding how feeding strategies influence oral morphology is fundamental to fish functional anatomy and trophic ecology. However, comparative data on tongue structure across dietary groups remain scarce in teleosts. This study examined tongue morphology in Boops boops (bogue), an omnivorous teleost with opportunistic feeding habits, and Pagrus pagrus (red porgy), a carnivorous benthic feeder with specialized prey preferences. By selecting species with distinct trophic niches, we aimed to elucidate how tongue architecture reflects dietary adaptations within teleosts. Morphometric analysis supported by light and scanning electron microscopy revealed that the bogue exhibited a higher tongue length-to-body weight ratio (34.1 %) than the red porgy (14.3 %). In contrast, the red porgy showed a greater tongue length-to-body length ratio (7.1 % vs. 5.4 %) and consistently broader tongue dimensions. The bogue tongue was sword-shaped with a pointed apex, while the red porgy’s tongue featured a rounded apex. Papillary patterns differed markedly: the bogue displayed gustatory structures including fungiform papillae at the apex, mixed filiform and fungiform papillae in the body, and volcano-like filiform papillae at the root. In contrast, the red porgy exhibited predominantly mechanical structures, such as filiform papillae at the apex, dome-like filiform papillae in the body, and dome-to scale-like papillae at the root. Histologically, both species shared a common organization of mucosa, submucosa (with connective and adipose tissues), ento-glossal hyaline cartilage, and striated muscle fibers. However, the bogue’s tongue showed stratified squamous epithelium with gustatory papillae, apical taste buds, and nerve endings. At the same time, the red porgy had abundant mucous cells and mechanical papillae concentrated at the root. Additionally, vascular channels with nucleated erythrocytes were observed in both species. These findings highlight distinct structural specializations of the tongue associated with omnivorous versus carnivorous feeding modes, offering new insights into the functional morphology and evolutionary adaptation of oral structures in teleost fishes.
{"title":"Comparative functional tongue morphology in male omnivorous bogue (Boops boops) and carnivorous red porgy (Pagrus pagrus) in relation to feeding habits: A study using light microscopy, scanning electron microscopy, and morphometric analysis","authors":"Mohamed A.M. Alsafy , Samir A.A. El-Gendy , Ahmed M. Rashwan , Samar M. Ez Elarab , Manal Seif , Neveen E.R. El-Bakary , Ahmed A. El-Mansi , Mamdouh B. Eldesoqui , Amal F. Dawood , Catrin S. Rutland , Valentina Kubale","doi":"10.1016/j.zool.2025.126306","DOIUrl":"10.1016/j.zool.2025.126306","url":null,"abstract":"<div><div>Understanding how feeding strategies influence oral morphology is fundamental to fish functional anatomy and trophic ecology. However, comparative data on tongue structure across dietary groups remain scarce in teleosts. This study examined tongue morphology in <em>Boops boops</em> (bogue), an omnivorous teleost with opportunistic feeding habits, and <em>Pagrus pagrus</em> (red porgy), a carnivorous benthic feeder with specialized prey preferences. By selecting species with distinct trophic niches, we aimed to elucidate how tongue architecture reflects dietary adaptations within teleosts. Morphometric analysis supported by light and scanning electron microscopy revealed that the bogue exhibited a higher tongue length-to-body weight ratio (34.1 %) than the red porgy (14.3 %). In contrast, the red porgy showed a greater tongue length-to-body length ratio (7.1 % vs. 5.4 %) and consistently broader tongue dimensions. The bogue tongue was sword-shaped with a pointed apex, while the red porgy’s tongue featured a rounded apex. Papillary patterns differed markedly: the bogue displayed gustatory structures including fungiform papillae at the apex, mixed filiform and fungiform papillae in the body, and volcano-like filiform papillae at the root. In contrast, the red porgy exhibited predominantly mechanical structures, such as filiform papillae at the apex, dome-like filiform papillae in the body, and dome-to scale-like papillae at the root. Histologically, both species shared a common organization of mucosa, submucosa (with connective and adipose tissues), ento-glossal hyaline cartilage, and striated muscle fibers. However, the bogue’s tongue showed stratified squamous epithelium with gustatory papillae, apical taste buds, and nerve endings. At the same time, the red porgy had abundant mucous cells and mechanical papillae concentrated at the root. Additionally, vascular channels with nucleated erythrocytes were observed in both species. These findings highlight distinct structural specializations of the tongue associated with omnivorous versus carnivorous feeding modes, offering new insights into the functional morphology and evolutionary adaptation of oral structures in teleost fishes.</div></div>","PeriodicalId":49330,"journal":{"name":"Zoology","volume":"173 ","pages":"Article 126306"},"PeriodicalIF":1.6,"publicationDate":"2025-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145520740","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-10-24DOI: 10.1016/j.zool.2025.126304
De-Li Xu, Xiao-Kai Hu
The immune system plays a crucial role in protecting animals from the attack of pathogens and hence determines their survival. However, animals’ immunity is influenced by many environmental factors. Cage feeding density is one of the most important factors influencing immune function in animals. To test whether high cage feeding density would suppress animals’ immunity, female striped hamsters (Cricetulus barabensis) were divided into the One/Cage, Two/Cage, and Three/Cage groups. Phytohaemagglutinin (PHA) responses were higher in the One/Cage group than the other two groups, implying that cellular immunity was suppressed by high cage feeding density. The numbers of white blood cell (WBC) and lymphocytes (LYMF), the coagulation ability indicated by blood platelet count (PLT), mean platelet volume (MPV) and platelet distribution width (PDW) were the highest in the Three/Cage group among the three groups, implying the occurrence of the fight and injury in the high cage feeding density. Other immunological parameters including the masses of thymus and spleen, intermediate granulocytes (MID), neutrophil granulocytes (GRAN) were all not impacted by cage feeding density. Total body fat mass, the levels of blood glucose, leptin and corticosterone did not differ among the three groups, and these parameters were not correlated with PHA responses, WBC, LYMF, MID and GRAN except that LYMF was positively correlated with blood glucose levels, indicating that the changes in immunity might not be caused by the energy status and stress hormone in hamsters. Suppression of cellular immunity and the increase of WBCs, LYMF under high feeding density might help us to understand the adverse effect of high population density on animals’ survival in the wild. Our findings may also provide some useful information on animal welfare, laboratory animals preparation and wildlife management.
{"title":"Influence of cage feeding density on immune function in female striped hamsters","authors":"De-Li Xu, Xiao-Kai Hu","doi":"10.1016/j.zool.2025.126304","DOIUrl":"10.1016/j.zool.2025.126304","url":null,"abstract":"<div><div>The immune system plays a crucial role in protecting animals from the attack of pathogens and hence determines their survival. However, animals’ immunity is influenced by many environmental factors. Cage feeding density is one of the most important factors influencing immune function in animals. To test whether high cage feeding density would suppress animals’ immunity, female striped hamsters (<em>Cricetulus barabensis</em>) were divided into the One/Cage, Two/Cage, and Three/Cage groups. Phytohaemagglutinin (PHA) responses were higher in the One/Cage group than the other two groups, implying that cellular immunity was suppressed by high cage feeding density. The numbers of white blood cell (WBC) and lymphocytes (LYMF), the coagulation ability indicated by blood platelet count (PLT), mean platelet volume (MPV) and platelet distribution width (PDW) were the highest in the Three/Cage group among the three groups, implying the occurrence of the fight and injury in the high cage feeding density. Other immunological parameters including the masses of thymus and spleen, intermediate granulocytes (MID), neutrophil granulocytes (GRAN) were all not impacted by cage feeding density. Total body fat mass, the levels of blood glucose, leptin and corticosterone did not differ among the three groups, and these parameters were not correlated with PHA responses, WBC, LYMF, MID and GRAN except that LYMF was positively correlated with blood glucose levels, indicating that the changes in immunity might not be caused by the energy status and stress hormone in hamsters. Suppression of cellular immunity and the increase of WBCs, LYMF under high feeding density might help us to understand the adverse effect of high population density on animals’ survival in the wild. Our findings may also provide some useful information on animal welfare, laboratory animals preparation and wildlife management.</div></div>","PeriodicalId":49330,"journal":{"name":"Zoology","volume":"173 ","pages":"Article 126304"},"PeriodicalIF":1.6,"publicationDate":"2025-10-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145366164","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-09-01DOI: 10.1016/j.zool.2025.126295
Lam V. Nguyen , Phuong T. Dang , Van V. Mai , Loi X. Tran
Shifting of the locomotor mode from an aquatic thrust to a ground reaction force enabled vertebrates moving on land, which happened at the same time as fin-to-limb evolution. Early stages of this evolution are little known due to scattered fossil records. Oxudercine gobies, exhibiting the full spectrum of terrestriality and terrestrial locomotor behavior, provide a unique window to understand how the form and function of the pectoral fins were modified during the water-to-land transition. In the present study, the musculoskeletal system of pectoral fins of three mudskippers [Oxuderces nexipinnis (low terrestrial), Scartelaos histophorus (moderate terrestrial), and Periophthalmodon septemradiatus (high terrestrial)] and the out-group species (Oxyeleotris urophthalmus) were examined. There are some anatomical modifications endowing crutching on land including: the robust and triangular cleithrum; the stiff and elongated radials and fin rays; the development of the coracoid process, the radial process, and the coraco-radialis; the two hinge-like structures; the differentiated muscular system inclining in various angles; and well-developed adductor muscles. These configurations are correlated with the degree of terrestriality. Of these anatomical modifications, the presence of the coracoid process, the radial process, and the coraco-radialis could endow terrestrial movement in early oxudercine gobies. In addition, fin rays of early oxudercine gobies could prevent them from sinking into the unconsolidated substrates which could be analogous to the condition in sarcopterygian fishes. In general, this study shows the gradual evolution of the muscular and skeletal systems of the pectoral fins in the oxudercine gobies during water-to-land transitions.
{"title":"Musculoskeletal comparison of the pectoral fin in mudskippers (Gobiidae: Oxudercinae)","authors":"Lam V. Nguyen , Phuong T. Dang , Van V. Mai , Loi X. Tran","doi":"10.1016/j.zool.2025.126295","DOIUrl":"10.1016/j.zool.2025.126295","url":null,"abstract":"<div><div>Shifting of the locomotor mode from an aquatic thrust to a ground reaction force enabled vertebrates moving on land, which happened at the same time as fin-to-limb evolution. Early stages of this evolution are little known due to scattered fossil records. Oxudercine gobies, exhibiting the full spectrum of terrestriality and terrestrial locomotor behavior, provide a unique window to understand how the form and function of the pectoral fins were modified during the water-to-land transition. In the present study, the musculoskeletal system of pectoral fins of three mudskippers [<em>Oxuderces nexipinnis</em> (low terrestrial), <em>Scartelaos histophorus</em> (moderate terrestrial), and <em>Periophthalmodon septemradiatus</em> (high terrestrial)] and the out-group species (<em>Oxyeleotris urophthalmus</em>) were examined. There are some anatomical modifications endowing crutching on land including: the robust and triangular cleithrum; the stiff and elongated radials and fin rays; the development of the coracoid process, the radial process, and the coraco-radialis; the two hinge-like structures; the differentiated muscular system inclining in various angles; and well-developed adductor muscles. These configurations are correlated with the degree of terrestriality. Of these anatomical modifications, the presence of the coracoid process, the radial process, and the coraco-radialis could endow terrestrial movement in early oxudercine gobies. In addition, fin rays of early oxudercine gobies could prevent them from sinking into the unconsolidated substrates which could be analogous to the condition in sarcopterygian fishes. In general, this study shows the gradual evolution of the muscular and skeletal systems of the pectoral fins in the oxudercine gobies during water-to-land transitions.</div></div>","PeriodicalId":49330,"journal":{"name":"Zoology","volume":"172 ","pages":"Article 126295"},"PeriodicalIF":1.6,"publicationDate":"2025-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145208877","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-09-01DOI: 10.1016/j.zool.2025.126294
Michael R. Minicozzi , Shannon Hansen , Michael Akland , Ana Braga , Owen Kyle , C. Loren Buck , Miriam Ashley-Ross , Alice C. Gibb
Aquatic and amphibious fishes produce a variety of behaviors when stranded on land, including a ballistic movement called a tail-flip jump. Although recent studies have examined jump performance (distance) in several cyprinodontiform species, less is known about the diversity of behaviors produced by teleosts when stranded on land. Here, seven species from four major teleost lineages (individual n = 4–12) were manually stranded in a terrestrial arena for two-minute trials. From videos of the trials, the number of jumps, flops (movements <1 body length), displacement (total and mean), latency (time to onset of movement), and percent time moving were quantified for each individual. A principal components analysis of these variables was used to define four “behavioral spaces:” species that produced effective displacement and spent the majority of the trial period moving (Danio); species that produced less effective displacement and spent the majority of the trial period moving (Pseudomugil); species that produced less effective displacement and spent little time moving (Umbra); and species that produced effective displacement, but spent little time moving (Kryptolebias). Based on the literature and metabolic data collected for this study, it appears that the ability to extract oxygen from air (vs. water) predicts the amount of time spent moving when stranded on land. Air-breathing fishes appear to adopt a “wait and see strategy,” while species that lack the ability to breathe air move immediately and frequently, likely an attempt to return to the water as quickly as possible.
{"title":"Flip or flop? Behavioral response to stranding in fish representing six teleost orders","authors":"Michael R. Minicozzi , Shannon Hansen , Michael Akland , Ana Braga , Owen Kyle , C. Loren Buck , Miriam Ashley-Ross , Alice C. Gibb","doi":"10.1016/j.zool.2025.126294","DOIUrl":"10.1016/j.zool.2025.126294","url":null,"abstract":"<div><div>Aquatic and amphibious fishes produce a variety of behaviors when stranded on land, including a ballistic movement called a tail-flip jump. Although recent studies have examined jump performance (distance) in several cyprinodontiform species, less is known about the diversity of behaviors produced by teleosts when stranded on land. Here, seven species from four major teleost lineages (individual n = 4–12) were manually stranded in a terrestrial arena for two-minute trials. From videos of the trials, the number of jumps, flops (movements <1 body length), displacement (total and mean), latency (time to onset of movement), and percent time moving were quantified for each individual. A principal components analysis of these variables was used to define four “behavioral spaces:” species that produced effective displacement and spent the majority of the trial period moving (<em>Danio</em>); species that produced less effective displacement and spent the majority of the trial period moving (<em>Pseudomugil</em>); species that produced less effective displacement and spent little time moving (<em>Umbra</em>); and species that produced effective displacement, but spent little time moving (<em>Kryptolebias</em>). Based on the literature and metabolic data collected for this study, it appears that the ability to extract oxygen from air (vs. water) predicts the amount of time spent moving when stranded on land. Air-breathing fishes appear to adopt a “wait and see strategy,” while species that lack the ability to breathe air move immediately and frequently, likely an attempt to return to the water as quickly as possible.</div></div>","PeriodicalId":49330,"journal":{"name":"Zoology","volume":"172 ","pages":"Article 126294"},"PeriodicalIF":1.6,"publicationDate":"2025-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145158775","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-09-01DOI: 10.1016/j.zool.2025.126296
Marko Maričić, Vukašin Bjelica, Ana Golubović
Bite force is a biomechanical trait that serves as a valuable proxy for assessing ecological interactions, feeding specialisations, and evolutionary pressures. Chelonians are a unique model system in studies of masticatory performances due to their akinetic skull and lack of teeth. It is known that body size, head morphology and sex-related differences influence bite performance of some chelonian species. In this study, we investigated the variation in bite force within and among five populations of the European pond turtle (Emys orbicularis) in Serbia. We examined relationship of bite force with phenotypic traits such as body size, head dimensions, body condition and muscle strength, as well as body temperature and seasonality. Bite force was measured in the field (N = 209) with an adapted digital force sensor. Our results showed significant differences in bite force across populations, suggesting that local ecological conditions may play a crucial role in shaping bite performance. In particular, turtles from more diverse and structurally complex environments, and turtles sharing their habitat with non-native pond sliders (Trachemys scripta ssp.) exhibited higher bite forces. We also detected a positive association between bite force and maximal pulling force, volumetric body condition index, body size and head height. Surprisingly, sex, cloacal temperature and seasonality were not significant predictors of bite force. Despite the challenges of measuring maximal performance under field conditions, our findings illustrate how variation in functional traits can reflect both intrinsic factors and ecological context, with implications for the study of biomechanical adaptations across animal taxa.
咬合力是一种生物力学特征，可以作为评估生态相互作用、捕食专业化和进化压力的有价值的代理。由于龟类动物的颅骨不动且没有牙齿，因此在研究咀嚼行为方面是一个独特的模型系统。已知身体大小，头部形态和性别相关的差异影响某些龟种的咬伤性能。在这项研究中，我们调查了在塞尔维亚的欧洲池龟（Emys orbicularis）的五个种群内和之间的咬合力的变化。我们研究了咬合力与身体大小、头部尺寸、身体状况和肌肉力量、体温和季节等表型性状的关系。在现场用适应的数字力传感器测量咬合力（N = 209）。我们的研究结果显示，不同种群的咬合力存在显著差异，表明当地的生态条件可能在塑造咬合力方面起着至关重要的作用。特别是，来自更多样化和结构复杂环境的海龟，以及与非本地池塘滑梯（Trachemys scripta ssp.）共享栖息地的海龟表现出更高的咬合力。我们还发现咬合力与最大拉力、体积身体状况指数、身体尺寸和头高呈正相关。令人惊讶的是，性别、肛管温度和季节并不是咬合力的显著预测因子。尽管在野外条件下测量最大性能存在挑战，但我们的研究结果说明了功能性状的变化如何反映内在因素和生态环境，这对动物分类群的生物力学适应研究具有重要意义。
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Pub Date : 2025-08-19DOI: 10.1016/j.zool.2025.126293
Marangaby Mahamat , Luis F. De León , Mery L. Martínez
An organism's ability to produce viable offspring, or reproductive fitness, often depends on several environmental and ecological factors such as temperature, food availability and predation. Changes in these factors can act as stressors, forcing organisms to optimize energy allocation, resulting in trade-offs. In this study, we investigate the reproductive biology of the South American electric fish Brachyhypopomus occidentalis, examining whether perceived predation risk can influence reproductive output. We sampled four populations during the reproductive season at two pairs of sites with differing levels of predation risk across independent river drainages. We assessed several traits including sexual dimorphism and reproductive traits such as gonad mass, fecundity, and gamete morphology parameters. Our findings reveal physical sexual dimorphism, with males being larger and heavier than females. Individuals from low predation risk sites were significantly larger, had heavier gonads, and exhibited higher gonadosomatic indices. Females from low predation risk sites invested more in gonad development, showing increased relative and absolute fecundities and higher oocyte counts at each maturity stage. Collectively, our results strongly suggest that predation risk plays a significant role in shaping reproductive strategies in electric fishes and also underscore how ecological pressures can drive variation in reproductive investment across fish populations.
{"title":"Reproductive investment in the knifefish Brachyhypopomus occidentalis","authors":"Marangaby Mahamat , Luis F. De León , Mery L. Martínez","doi":"10.1016/j.zool.2025.126293","DOIUrl":"10.1016/j.zool.2025.126293","url":null,"abstract":"<div><div>An organism's ability to produce viable offspring, or reproductive fitness, often depends on several environmental and ecological factors such as temperature, food availability and predation. Changes in these factors can act as stressors, forcing organisms to optimize energy allocation, resulting in trade-offs. In this study, we investigate the reproductive biology of the South American electric fish <em>Brachyhypopomus occidentalis</em>, examining whether perceived predation risk can influence reproductive output. We sampled four populations during the reproductive season at two pairs of sites with differing levels of predation risk across independent river drainages. We assessed several traits including sexual dimorphism and reproductive traits such as gonad mass, fecundity, and gamete morphology parameters. Our findings reveal physical sexual dimorphism, with males being larger and heavier than females. Individuals from low predation risk sites were significantly larger, had heavier gonads, and exhibited higher gonadosomatic indices. Females from low predation risk sites invested more in gonad development, showing increased relative and absolute fecundities and higher oocyte counts at each maturity stage. Collectively, our results strongly suggest that predation risk plays a significant role in shaping reproductive strategies in electric fishes and also underscore how ecological pressures can drive variation in reproductive investment across fish populations.</div></div>","PeriodicalId":49330,"journal":{"name":"Zoology","volume":"172 ","pages":"Article 126293"},"PeriodicalIF":1.6,"publicationDate":"2025-08-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144896230","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-06-14DOI: 10.1016/j.zool.2025.126283
Mariana B.J. Picasso , María Clelia Mosto , Alejandro M. Tudisca , Laura M. Biondi
The jaw muscle architecture is crucial for understanding how muscle morphology influences diet and feeding behavior in birds, yet ontogenetic scaling patterns and their characteristics in herbivorous species remain understudied. This study examines the physiological cross-sectional area (PCSA) and fiber length of the jaw muscles in Rhea americana, an herbivorous bird whose chicks are insectivorous during early stages. The main jaw muscles of 19 Rhea americana specimens across four ontogenetic stages were analyzed, including the depressor mandibulae (a jaw depressor) and the adductor mandibulae externus, pseudotemporalis, and pterygoideus lateralis (primarily jaw adductors). Both architectural parameters showed a negative allometric scaling and only significant differences in PCSA were found between immature ages and between these and adulthood in certain adductor muscles. These variations suggest increasing force demands in adductor muscles as chicks transition from an insectivorous to an herbivorous diet. The lower PCSA in early-staged chicks reflects the reduced force required for insectivory, while the increasing PCSA with age enables force generation needed for detaching plants in adults. In comparison to other avian diets, the herbivory of greater rhea seems to be linked to a lower force-generating capacity in the adductor muscle group. This study contributes to expanding the knowledge on avian jaw musculature by exploring postnatal ontogenetic changes and their potential relationship with dietary shifts while providing morphological data that can serve as a comparative basis for understanding the link between diet and morphology in birds.
{"title":"Jaw muscle architecture in the greater rhea (Rhea americana): Morphological patterns and postnatal ontogeny in an herbivorous bird","authors":"Mariana B.J. Picasso , María Clelia Mosto , Alejandro M. Tudisca , Laura M. Biondi","doi":"10.1016/j.zool.2025.126283","DOIUrl":"10.1016/j.zool.2025.126283","url":null,"abstract":"<div><div>The jaw muscle architecture is crucial for understanding how muscle morphology influences diet and feeding behavior in birds, yet ontogenetic scaling patterns and their characteristics in herbivorous species remain understudied. This study examines the physiological cross-sectional area (PCSA) and fiber length of the jaw muscles in <em>Rhea americana</em>, an herbivorous bird whose chicks are insectivorous during early stages. The main jaw muscles of 19 <em>Rhea americana</em> specimens across four ontogenetic stages were analyzed, including the depressor mandibulae (a jaw depressor) and the adductor mandibulae externus, pseudotemporalis, and pterygoideus lateralis (primarily jaw adductors). Both architectural parameters showed a negative allometric scaling and only significant differences in PCSA were found between immature ages and between these and adulthood in certain adductor muscles. These variations suggest increasing force demands in adductor muscles as chicks transition from an insectivorous to an herbivorous diet. The lower PCSA in early-staged chicks reflects the reduced force required for insectivory, while the increasing PCSA with age enables force generation needed for detaching plants in adults. In comparison to other avian diets, the herbivory of greater rhea seems to be linked to a lower force-generating capacity in the adductor muscle group. This study contributes to expanding the knowledge on avian jaw musculature by exploring postnatal ontogenetic changes and their potential relationship with dietary shifts while providing morphological data that can serve as a comparative basis for understanding the link between diet and morphology in birds.</div></div>","PeriodicalId":49330,"journal":{"name":"Zoology","volume":"171 ","pages":"Article 126283"},"PeriodicalIF":1.6,"publicationDate":"2025-06-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144306973","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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