{"title":"Ontogenetic Changes in the Endocast and Endosseous Labyrinth of the Siamese Freshwater Crocodile (<i>Crocodylus siamensis</i> Schneider, 1801) from Thailand.","authors":"Parinya Thanoi, Kanyarat Saenghong, Komsorn Lauprasert","doi":"10.6620/ZS.2026.65-42","DOIUrl":"https://doi.org/10.6620/ZS.2026.65-42","url":null,"abstract":"<p><p>Ontogenetic changes in the brain and sensory systems play an essential role in shaping behavioral performance and ecological specialization in vertebrates; however, these developmental pathways are inadequately recorded in endangered crocodylians. Here, we present the first quantitative analysis of endocast and endosseous labyrinth development across ontogeny in the Siamese freshwater crocodile (<i>Crocodylus siamensis</i>), a critically endangered species from Southeast Asia. Using high-resolution computed tomography (CT) and three-dimensional reconstruction, we examined six skulls representing juvenile, subadult, and adult growth stages. Our findings reveal a consistent pattern of allometric scaling, correlated with marked morphological changes in sensory-related neuroanatomical structures. Juveniles display strongly curved forebrains and proportionally prominent olfactory regions, which is in line with their early reliance on chemosensory cues. As skull size increases, the encephalic endocast becomes longer and straighter, while regions corresponding to the midbrain and hindbrain show proportional morphological changes associated with visual processing and motor coordination, suggesting ontogenetic changes in regions associated with visual processing and motor coordination. Parallel ontogenetic transformations are also observed in the endosseous labyrinth, including increased lagena dimensions and more pronounced semicircular canal curvature in adults. These changes are consistent with ontogenetic variation in structures associated with auditory and vestibular functions. Strong correlations between dorsal cranial length and both endocast and labyrinthine parameters suggest that sensory-related neuroanatomical morphology in <i>C. siamensis</i> follows a consistent ontogenetic scaling pattern. These findings establish an important neuroanatomical baseline for understanding sensory ecology in this endangered crocodilian and provide a comparative framework for interpreting fossil crocodylian neuroanatomy, with implications for conservation biology, functional morphology, and paleoneurology.</p>","PeriodicalId":49331,"journal":{"name":"Zoological Studies","volume":"65 ","pages":"e42"},"PeriodicalIF":1.4,"publicationDate":"2026-09-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC13677278/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"149225179","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Zoological StudiesPub Date : 2026-09-11eCollection Date: 2026-01-01DOI: 10.6620/ZS.2026.65-41
Romain Sabroux
{"title":"<i>Maageninum kanakorum</i> gen. nov., sp. nov.: a New Caledonian Pycnogonid (Arthropoda: Pycnogonida) with Puzzling Affinities.","authors":"Romain Sabroux","doi":"10.6620/ZS.2026.65-41","DOIUrl":"https://doi.org/10.6620/ZS.2026.65-41","url":null,"abstract":"<p><p>The taxonomic classification of sea spiders (Arthropoda: Pycnogonida) includes 11 distinct families, mostly characterized by different combinations of presence/absence of the cephalic appendages, the characters they display (number of articles, terminal claw, distribution of spines, etc.), and the position of gonopores in both sexes and of the cement gland pores in males. However, about 20 nominal species could not be confidently classified, and a few others were only tentatively assigned to one of these families. These taxa represent an interesting challenge to review, reshape and expand the Pycnogonida taxonomy, and thus to apprehend more comprehensively the phylogeny of the group. In this contribution, <i>Maageninum kanakorum</i> gen. nov., sp. nov. is described based on two males and two females that were sampled at 220-232 m depth in a single location off southeast of New Caledonia in 2011 during the EXBODI expedition (Tropical Deep-Sea Benthos program). A fragment of the gene coding for the first unit of the cytochrome oxidase was sequenced for three of these specimens for the purpose of DNA barcoding, and the gonopores were investigated in both sexes through scanning electron microscopy. Due to its unique combination of characters, the genus <i>Maageninum</i> cannot be confidently attributed to any of the known pycnogonid families based on the sole morphological characters: absence of chelifores; palps reduced to two articles only present in males; ovigers two-articled in males, or reduced to a conspicuous unarticulated bud in females; gonopores carried on the ventral surface of coxae 2 in legs 2-4, both in males and females. For this reason, it is to be regarded as <i>incertae sedis</i> until its position is resolved by future phylogenetic studies.</p>","PeriodicalId":49331,"journal":{"name":"Zoological Studies","volume":"65 ","pages":"e41"},"PeriodicalIF":1.4,"publicationDate":"2026-09-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC13659617/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"149185194","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Zoological StudiesPub Date : 2026-09-11eCollection Date: 2026-01-01DOI: 10.6620/ZS.2026.65-35
Yeison Vega, Mariajose Hernández-Caballero, Shinichi Nakahara, Pierre Boyer, Vanessa Díaz-S, Oscar Jaime, Oscar Mahecha-J, Tomasz W Pyrcz
{"title":"Life Woven in Mist: Immature stages and morphology of Andean Pronophilina butterflies from the Eastern Cordillera of Colombia (Satyrinae: Satyrini).","authors":"Yeison Vega, Mariajose Hernández-Caballero, Shinichi Nakahara, Pierre Boyer, Vanessa Díaz-S, Oscar Jaime, Oscar Mahecha-J, Tomasz W Pyrcz","doi":"10.6620/ZS.2026.65-35","DOIUrl":"https://doi.org/10.6620/ZS.2026.65-35","url":null,"abstract":"<p><p>The subtribe Pronophilina comprises the most diverse lineage of Andean butterflies, with 59 genera and approximately 650 described species. Most studies on this group have focused on adults, highlighting a substantial gap in knowledge regarding the immature stages of the majority of species. Here, we document immatures stages of five Pronophilina species (<i>Idioneurula erebioides,</i> <i>Daedalma drusilla</i>, <i>Pedaliodes ochrotaenia</i>, <i>P. nebris</i>, <i>P. guicana</i>) for the first time. Additionally, we document immature stages of two additional species (<i>Lymanopoda samius</i>, <i>Junea doraete</i>) from the Eastern Cordillera in Colombia, building on earlier studies on these two taxa. The methodology involved systematic searches for eggs and larvae on potential host plants in the field. Collected larvae were photographed and monitored in the laboratory. Data on their interactions with host plants and parasitoids are presented. This approach allowed a comprehensive characterization of the life cycles, host plant associations, and larval behavior of each instar, providing valuable insights into the biology and ecology of this group of butterflies.</p>","PeriodicalId":49331,"journal":{"name":"Zoological Studies","volume":"65 ","pages":"e35"},"PeriodicalIF":1.4,"publicationDate":"2026-09-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC13659618/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"149185224","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Zoological StudiesPub Date : 2026-09-11eCollection Date: 2026-01-01DOI: 10.6620/ZS.2026.65-34
Fei Xia, Cheng Yang, Min Liu, Lan Liu, Xinqing Zheng, Xinming Liu
{"title":"<i>Tubastraea candidiflora</i> sp. nov. (Scleractinia: Dendrophylliidae): a New Sun Coral Species from Fujian, Southeastern China.","authors":"Fei Xia, Cheng Yang, Min Liu, Lan Liu, Xinqing Zheng, Xinming Liu","doi":"10.6620/ZS.2026.65-34","DOIUrl":"https://doi.org/10.6620/ZS.2026.65-34","url":null,"abstract":"<p><p>The genus <i>Tubastraea</i> Lesson, 1830 comprises azooxanthellate corals commonly known as sun corals. Based on specimens collected from Dongshan Island, southeastern China, we describe a new species, <i>Tubastraea candidiflora</i> sp. nov. The species is distinguished from most congeners by the combination of pure white tentacles, a Pourtalès plan, a phaceloid to weakly branching colony form, and strongly differentiated costae. Pairwise comparisons of three commonly used markers (<i>COI</i>, IGR, and rDNA) show substantial rDNA divergence from congeners (<i>p</i>-distance = 2.61-6.09%). Phylogenetic analyses of the concatenated three-marker dataset recover the Dongshan specimens as a distinct lineage, and an independent UCE phylogenomic dataset recovers the same clade with strong support. Together, the morphological and molecular evidence supports <i>T. candidiflora</i> sp. nov. as a distinct species and expands current knowledge of <i>Tubastraea</i> diversity in subtropical China.</p>","PeriodicalId":49331,"journal":{"name":"Zoological Studies","volume":"65 ","pages":"e34"},"PeriodicalIF":1.4,"publicationDate":"2026-09-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC13659616/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"149185202","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Zoological StudiesPub Date : 2026-09-11eCollection Date: 2026-01-01DOI: 10.6620/ZS.2026.65-43
Lal Biakzuala, Hmar Tlawmte Lalremsanga
{"title":"Sexual Dimorphism, Intrapopulation Phenotypic Variation and Matrilineal Genetic Diversity of <i>Naja kaouthia</i> Lesson, 1831 (Reptilia: Squamata: Elapidae) from Mizoram, Northeast India.","authors":"Lal Biakzuala, Hmar Tlawmte Lalremsanga","doi":"10.6620/ZS.2026.65-43","DOIUrl":"https://doi.org/10.6620/ZS.2026.65-43","url":null,"abstract":"<p><p><i>Naja kaouthia</i> Lesson, 1831 is a common and widely distributed venomous snake in South and Southeast Asia. The species is regarded as having a high degree of phenotypic plasticity and variability in venom composition across its distributional range. Limited information is available on this complex species in the context of population studies and systematics, and population studies, particularly in northeast India, are scarce. In this study, we explore sexual dimorphism and potential intraspecific morphological variation within the population of <i>N. kaouthia</i> from Mizoram, northeast India, while also aiming to enrich the systematic data and reappraise the matrilineal genetic diversity across various geographical locations. Sexually dimorphic traits are identified in both meristic and morphometric characters. We hypothesise that male-biased sexual selection for success in male-male rivalry may be the cause of sexual dimorphism in head size and shape in this species. Our mitochondrial phylogeny (<i>16s</i>, <i>cytb</i> and <i>cox1</i>) recovered two well-supported South Asian and Southeast Asian clades within <i>N. kaouthia</i> with a wide genetic divergence (4.4%) between them. Our study also revealed intraspecific variation in the hood markings from the examined population, which warrant more studies to determine whether these variants are randomly distributed or reflect geographic structure and lineage differentiation.</p>","PeriodicalId":49331,"journal":{"name":"Zoological Studies","volume":"65 ","pages":"e43"},"PeriodicalIF":1.4,"publicationDate":"2026-09-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC13677277/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"149225175","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Zoological StudiesPub Date : 2026-09-02eCollection Date: 2026-01-01DOI: 10.6620/ZS.2026.65-40
Chia-Hao Chang
{"title":"Exposure to Predators Induces Phenotypic Plasticity in Cone Opsin Expression Profiles but not in Eye Size of Female Trinidad Guppies.","authors":"Chia-Hao Chang","doi":"10.6620/ZS.2026.65-40","DOIUrl":"10.6620/ZS.2026.65-40","url":null,"abstract":"<p><p>Teleost fish display very diverse visual systems through evolutionary adaptation and phenotypic plasticity to the variable light of aquatic environments. Whether predator presence influences eye size in prey is controversial because though larger eyes endow better optics, they also consume more energy and are more conspicuous. Moreover, whether predation alters the visual spectra of prey is unclear. Predation profoundly affects inter-populational divergence of male coloration and female mating preference in the Trinidad guppy (<i>Poecilia reticulata</i>). In this study, newborn guppies were raised under predation or control conditions, which revealed that although eye size did not differ between the treatments, predator presence induced plasticity in cone opsin expression profiles, potentially impacting female mate choice and predator sensitivity, as well as circumventing the costs of having large eyes. This study also lends support to the sensory drive model in guppy by evidencing how predation acts simultaneously on both male coloration and female visual spectra, reducing the survival of bright males, but also making them less attractive to females.</p>","PeriodicalId":49331,"journal":{"name":"Zoological Studies","volume":"65 ","pages":"e40"},"PeriodicalIF":1.4,"publicationDate":"2026-09-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC13621300/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"149082609","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Zoological StudiesPub Date : 2026-09-02eCollection Date: 2026-01-01DOI: 10.6620/ZS.2026.65-38
Julian J C Cordial, Mark K M Casindac, Emmanuel R C de Chavez
{"title":"Land Snail Diversity and Community Assemblage in Biak-Na-Bato National Park, San Miguel, Bulacan, Philippines.","authors":"Julian J C Cordial, Mark K M Casindac, Emmanuel R C de Chavez","doi":"10.6620/ZS.2026.65-38","DOIUrl":"10.6620/ZS.2026.65-38","url":null,"abstract":"<p><p>Karst ecosystems are critical refugia for various invertebrates including land snails. In the Philippines, data on these mollusks are insufficient amidst wide-scale habitat destruction due to uncurbed tourism and mineral extraction activities. To address this research gap, land snail diversity and community assemblage in the historic Biak-Na-Bato National Park (BNBNP), San Miguel, Bulacan were examined. A total of 32 5 × 5 m quadrats were randomly set around the vicinity of four accessible caves: Santol, Bahay Paniki, Cuarto-Cuarto, and Aguinaldo, during dry and wet seasons. Environmental variables including altitude, temperature, relative humidity, soil moisture, soil pH, soil exchangeable calcium, number of trees, diameter of trees, canopy cover, and leaf litter depth were measured. From a total of 2,834 land snails sampled, 42 species and 13 families were identified. From these, 23 were classified as macro (> 5 mm) and 18 as micro (< 5 mm) land snails, and one as a slug. Moreover, 37 (88.10%) were native species while 5 (11.90%) were non-native. Bahay Paniki recorded the highest species richness but lowest diversity (27 species/ qD = 5) whereas Aguinaldo exhibited the highest overall diversity (23 species/qD = 12). Relatively high sample coverage values (> 0.95) suggest increasing sampling effort to detect rare species. PERMANOVA and NMDS showed significant difference in community assemblage between sites. <i>Cyclophorus appendiculatus</i> attained the highest contribution (34.03%) to site dissimilarity. Land snail assemblages were influenced by temperature, soil pH, soil calcium, number of trees, tree diameter at breast height, and soil moisture based on CCA. The GLMM identified soil pH as the strongest predictor of species richness, while abundance was best explained by a combination of canopy cover, number of trees, soil moisture, soil pH, and temperature. This study reveals BNBNP's distinct malacofaunal diversity, underscoring its significance as a karst ecosystem that warrants continued conservation.</p>","PeriodicalId":49331,"journal":{"name":"Zoological Studies","volume":"65 ","pages":"e38"},"PeriodicalIF":1.4,"publicationDate":"2026-09-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC13621302/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"149082576","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Zoological StudiesPub Date : 2026-09-02eCollection Date: 2026-01-01DOI: 10.6620/ZS.2026.65-39
Ayesha Herath, Inoka Karunaratne
{"title":"Bee Pollinators Enhance B-onion Seed Production in the Dry Zone of Sri Lanka.","authors":"Ayesha Herath, Inoka Karunaratne","doi":"10.6620/ZS.2026.65-39","DOIUrl":"10.6620/ZS.2026.65-39","url":null,"abstract":"<p><p>Production of B-onion (<i>Allium cepa</i>), a key cash crop in Sri Lanka, falls short of consumer demand due to limited quality seeds and high cost of commercial seeds. This study investigated the role of insect pollination on B-onion seed production in the dry zone, Sri Lanka, focusing on key pollinators, seed yield, weight and germinability. Experimental plots were established in a home garden in Sigiriya, selecting 50 umbels; 25 opened to insects and 25 covered. Diurnal insect visits and floral resources were observed. Seed yield and germinability were compared between opened and covered flowers. <i>Halictus lucidipennis</i> was the highest frequent visitor, followed by <i>Apis cerana</i> and <i>A. florea</i>. Nesting sites of <i>H. lucidipennis</i> were observed within the plots. Bee visitation was higher between 8:00-9:00 am, coinciding with pollen foraging, while nectar foraging remained throughout the day. The species-specific foraging patterns highlighted that <i>H. lucidipennis</i> and <i>A. cerana</i> were most active around 8:00-9:00 am for pollen foraging, whereas <i>A. florea</i> preferred midday (between 12:00-1:00 pm) for nectar foraging. <i>Apis cerana</i> preferred nectar foraging around 4:00-5:00 pm. Open umbels had significantly higher seed number and weight than covered umbels (<i>P</i> = 0.00). Germination percentage was also significantly higher in open-pollinated seeds than covered seeds using both petri dish and envelope methods (<i>P</i> = 0.02 and <i>P</i> = 4.007e-06), with longer seedlings after eight days (<i>P</i> = 0.00 and <i>P</i> = 4.499e-11). These findings highlight the importance of bees in enhancing B-onion seed production. Future research should assess next-generation plant vigor and compare pollinator efficiency.</p>","PeriodicalId":49331,"journal":{"name":"Zoological Studies","volume":"65 ","pages":"e39"},"PeriodicalIF":1.4,"publicationDate":"2026-09-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC13621299/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"149082624","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Zoological StudiesPub Date : 2026-08-12eCollection Date: 2026-01-01DOI: 10.6620/ZS.2026.65-37
Sicheng Dai, Yongfeng Ye, Jian-Wen Qiu, Yanjie Zhang
{"title":"Two New Species of Intertidal and Subtidal Polychates <i>Owenia</i> (Annelida: Oweniidae) from South China.","authors":"Sicheng Dai, Yongfeng Ye, Jian-Wen Qiu, Yanjie Zhang","doi":"10.6620/ZS.2026.65-37","DOIUrl":"10.6620/ZS.2026.65-37","url":null,"abstract":"<p><p>Marine annelids in the genus <i>Owenia</i> Delle Chiaje 1844 collected from Chinese coastal waters have long been recorded as <i>O. fusiformis</i>, later <i>O. gomsoni</i> Koh and Bhaud 2001 for that from Qingdao and <i>O. collaris</i> Hartman, 1955 from Hong Kong. But combined morphological and molecular evidence reveal two new species of <i>Owenia</i> from the South China coast. <i>Owenia hongkongensis</i> n. sp. (previously recorded as <i>O. fusiformis</i>) inhabits subtidal and intertidal habitats in Hong Kong, and <i>Owenia hainanensis</i> n. sp. (previously recorded as <i>O. fusiformis</i>) inhabits intertidal habitats in Hainan. They are distinguished from each other and from congeners by branchial crown morphology, chaetal microstructure, and methyl green staining patterns. Mitochondrial genomes and nuclear <i>18S</i>, <i>28S</i> and <i>H3</i> sequences of the two new species were obtained via next-generation sequencing. Phylogenetic analyses based on <i>cox1</i>, <i>18S</i>, <i>28S</i> and <i>H3</i> showed that the species from Hong Kong and Hainan are distinct and they differ from previously sequenced <i>Owenia</i> species from other regions. These discoveries challenge the presumed cosmopolitan distribution of <i>O. fusiformis</i> and emphasize the value of integrating morphometrics and molecular data in the delimitation of <i>Owenia</i> species.</p>","PeriodicalId":49331,"journal":{"name":"Zoological Studies","volume":"65 ","pages":"e37"},"PeriodicalIF":1.4,"publicationDate":"2026-08-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC13621301/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"149082569","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Zoological StudiesPub Date : 2026-08-10eCollection Date: 2026-01-01DOI: 10.6620/ZS.2026.65-36
Asami Kajimoto, Ayako Tanaka, Tsuyoshi Ohira, Kenji Toyota
{"title":"Seasonal Dynamics of Sex Ratio, Reproduction, and Parasite-specific Feminization in the Hermit Crab <i>Pagurus filholi</i> at a Fixed Coastal Site in Chiba, Japan.","authors":"Asami Kajimoto, Ayako Tanaka, Tsuyoshi Ohira, Kenji Toyota","doi":"10.6620/ZS.2026.65-36","DOIUrl":"10.6620/ZS.2026.65-36","url":null,"abstract":"<p><p>Reproductive output in intertidal crustaceans is reshaped by seasonal changes in host demography and its interaction with parasitic castration, yet parasite-species-resolved time series remain scarce for hermit crabs. We conducted year-round monitoring of the hermit crab <i>Pagurus filholi</i> at a fixed intertidal site in Chiba Prefecture, Japan, with monthly sampling from January to December 2025. Hosts were sexed and female reproductive status (ovigerous vs. non-ovigerous) was recorded, and rhizocephalan infections were diagnosed by externa morphology and subsequently assigned to <i>Peltogasterella gracilis</i> or <i>Peltogaster postica</i> using DNA barcoding. Across 12 sampling occasions, 3,134 crabs were recorded (1,586 males; 1,548 females). Sex ratio varied significantly among months, shifting from female-biased in December (early winter)-May (late spring) to strongly male-biased in June (early summer)-November (late autumn). The proportion of ovigerous females also showed strong seasonality, peaking in mid-winter, declining through spring, reaching zero in August-September, and increasing again toward winter. Both parasites exhibited sharply seasonal prevalence with a pronounced June peak: for <i>Peltogasterella gracilis</i>, 29/166 in June vs. 8/2,968 in other months, and for <i>Peltogaster postica</i>, 19/166 vs. 36/2,968. Male secondary sexual morphology responded in a parasite-specific manner: infected males were more likely to bear a second pleopod, a female-specific egg-brooding structure, than males without externae, driven primarily by <i>Peltogasterella gracilis</i> (26/28) rather than Peltogaster postica (3/35). Together, these results provide a high-resolution baseline linking reproductive phenology and parasite-specific feminization in a single <i>P. filholi</i> population.</p>","PeriodicalId":49331,"journal":{"name":"Zoological Studies","volume":"65 ","pages":"e36"},"PeriodicalIF":1.4,"publicationDate":"2026-08-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC13586750/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"149009361","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}