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531.
《Current biology : CB》2022,32(23):5069-5082.e13
Download : Download video (27MB) 相似文献
532.
533.
The hypothesis that growth in Pacific salmon Oncorhynchus spp. is dependent on previous growth was tested using annual scale growth measurements of wild Chinook salmon Oncorhynchus tshawytscha returning to the Yukon and Kuskokwim Rivers, Alaska, from 1964 to 2004. First-year marine growth in individual O. tshawytscha was significantly correlated with growth in fresh water. Furthermore, growth during each of 3 or 4 years at sea was related to growth during the previous year. The magnitude of the growth response to the previous year's growth was greater when mean year-class growth during the previous year was relatively low. Length (eye to tail fork, L ETF ) of adult O. tshawytscha was correlated with cumulative scale growth after the first year at sea. Adult L ETF was also weakly correlated with scale growth that occurred during freshwater residence 4 to 5 years earlier, indicating the importance of growth in fresh water. Positive growth response to previous growth in O. tshawytscha was probably related to piscivorous diet and foraging benefits of large body size. Faster growth among O. tshawytscha year classes that initially grew slowly may reflect high mortality in slow growing fish and subsequent compensatory growth in survivors. Oncorhynchus tshawytscha in this study exhibited complex growth patterns showing a positive relationship with previous growth and a possible compensatory response to environmental factors affecting growth of the age class. 相似文献
534.
D.M. PEARSON 《Zoological Journal of the Linnean Society》1982,74(1):35-67
The relationships of the Devonian palaeonisciform fish Cheirolepis are examined and the early evolutionary trends within the Actinopterygii and the Osteichthyes are considered.
Cheirolepis is the most primitive known actinopterygian. The contemporary stegotrachelid palaeonisciforms are more advanced in their cranial and locomotor anatomy. The general directions of these advances are similar to those subsequently displayed by later palaeonisciforms over the stegotrachelids themselves. Cheirolepis , furthermore, possesses many characters which can be logically interpreted as primitive for the Osteichthyes by extrapolation of trends in actinopterygian and sarcopterygian lineages. 11 is the most primitive known osteichthyan.
The Osteichthyes are considered to have arisen from a micromerically-scaled acanthodian or acanthodian-like ancestor at the end of the Silurian period. 相似文献
Cheirolepis is the most primitive known actinopterygian. The contemporary stegotrachelid palaeonisciforms are more advanced in their cranial and locomotor anatomy. The general directions of these advances are similar to those subsequently displayed by later palaeonisciforms over the stegotrachelids themselves. Cheirolepis , furthermore, possesses many characters which can be logically interpreted as primitive for the Osteichthyes by extrapolation of trends in actinopterygian and sarcopterygian lineages. 11 is the most primitive known osteichthyan.
The Osteichthyes are considered to have arisen from a micromerically-scaled acanthodian or acanthodian-like ancestor at the end of the Silurian period. 相似文献
535.
During daily monitoring in Yongho Bay off Busan, Korea in 2019, an isolate of the dinoflagellate genus Heterocapsa was established in clonal culture. Light and electron microscopic examination revealed that the isolate was ellipsoid in shape, exhibiting a thecal plate arrangement (Po, cp, X, 5′, 3a, 7″, 6c, 5s, 5‴, 2ʹʹʹʹ) consistent with most other Heterocapsa species. A large, elongated nucleus was positioned on the left side of the cell, a single reticulate chloroplast was located peripherally, and a single, starch-sheathed, spherical pyrenoid was present in the episome or near the cingulum. Morphologically, the isolate most closely resembles H. circularisquama and H. illdefina. Transmission electron microscopic examination of whole mounts revealed that the isolate had two body scale types, one of which was a complex, three-dimensional, fine structure distinct from other Heterocapsa species, whereas the other simpler type was structurally similar to the scales of H. horiguchii. Molecular phylogeny based on rRNA sequences revealed that the isolate was distantly related to morphologically similar species, but formed a sister lineage to H. horiguchii, a species characterized by a similar body scale morphology. Based on morphological, ultrastructural, and molecular data, we proposed it as a new species, Heterocapsa busanensis sp. nov. 相似文献
536.
Elena Tassistro Davide Paolo Bernasconi Paola Rebora Maria Grazia Valsecchi Laura Antolini 《Biometrical journal. Biometrische Zeitschrift》2020,62(3):836-851
The illness-death model is the simplest multistate model where the transition from the initial state 0 to the absorbing state 2 may involve an intermediate state 1 (e.g., disease relapse). The impact of the transition into state 1 on the subsequent transition hazard to state 2 enables insight to be gained into the disease evolution. The standard approach of analysis is modeling the transition hazards from 0 to 2 and from 1 to 2, including time to illness as a time-varying covariate and measuring time from origin even after transition into state 1. The hazard from 1 to 2 can be also modeled separately using only patients in state 1, measuring time from illness and including time to illness as a fixed covariate. A recently proposed approach is a model where time after the transition into state 1 is measured in both scales and time to illness is included as a time-varying covariate. Another possibility is a model where time after transition into state 1 is measured only from illness and time to illness is included as a fixed covariate. Through theoretical reasoning and simulation protocols, we discuss the use of these models and we develop a practical strategy aiming to (a) validate the properties of the illness-death process, (b) estimate the impact of time to illness on the hazard from state 1 to 2, and (c) quantify the impact that the transition into state 1 has on the hazard of the absorbing state. The strategy is also applied to a literature dataset on diabetes. 相似文献
537.
《African Journal of Aquatic Science》2013,38(4):393-401
The present study, conducted between May 2012 and September 2013, aimed to determine the distribution of groundwater invertebrates in the Bamoun tableland, Cameroon. A total of 216 samples taken from 30 wells in four localities – Foumban, Foumbot, Kouoptamo and Magba – contained 80 invertebrate taxa belonging to Crustacea, Oligochaeta, Arachnida, Insecta, Nematoda, Tardigrada, and Gastropoda. The community was relatively rich, diverse, and was dominated by crustaceans. The distribution of groundwater fauna was influenced mainly by local factors, especially those related to the physical structure of wells such as the presence of a margin, a closing system, and total depth. At the regional scale, elevation and season were the only factors influencing the distribution of fauna. Further research needs to be conducted to highlight the relationship between groundwater invertebrates and human impacts in rural areas. 相似文献
538.
SERGE BERTHIER ERIC CHARRON JULIE BOULENGUEZ 《Insect Science》2006,13(2):145-158
The morphological structure and optical properties of the wings of 14 species of Morphidae have been investigated. Most of the scales of the iridescent species of Morphidae (Lepidoptera) present a very particular structure. The ground scales, responsible for the major part of the optical properties, are covered by a very regular set of longitudinal ridges. The ridges themselves are constituted by a superposition of lamellae that act locally as a multilayered structure. This very specific morphology leads to both interferences and diffraction effects. The first one is responsible of the brilliant blue coloration of the males, while the second one diffracts this colored light at a very large angle. These two phenomena give to the butterfly a very effective long-range communication system. The morphological characteristics of the scales of the various species are presented in detail. Two types of optical measurement were performed on the iridescent wings of 14 different species of Morphidae: spectroscopic measurements under various incidences and gonioscopic measurements for a given incidence angle and wavelength. The first allows a determination of the index of refraction of the cuticular material. The second leads to the drawing of spatial diffraction maps. It shows that most of the reflected light is diffracted laterally over a very large angle (90° 〈 0 〈 120°, according to the different species) and that this repartition depends of the polarization of incident light. As predicted by previous calculations, the dissymmetric structure of the ridge is responsible for the separation of the polarization modes in the various diffraction orders. 相似文献
539.
A. S. Downing S. Hajdu O. Hjerne S. A. Otto T. Blenckner U. Larsson M. Winder 《Ecology letters》2014,17(10):1219-1227
Scale is a key to determining which processes drive community structure. We analyse size distributions of phytoplankton to determine time scales at which we can observe either fixed environmental characteristics underlying communities structure or competition‐driven size distributions. Using multiple statistical tests, we characterise size distributions of phytoplankton from 20‐year time series in two sites of the Baltic Sea. At large temporal scales (5–20 years), size distributions are unimodal, indicating that fundamental barriers to existence are here subtler than in other systems. Frequency distributions of the average size of the species weighted by biovolume are multimodal over large time scales, although this is the product of often unimodal short‐term (<1 year) patterns. Our study represents a much‐needed structured, high‐resolution analysis of phytoplankton size distributions, revealing that short‐term analyses are necessary to determine if, and how, competition shapes them. Our results provide a stepping‐stone on which to further investigate the intricacies of competition and coexistence. 相似文献
540.
Pedro Henrique Pereira Braga Steven Kembel Pedro Peres-Neto 《Global Ecology and Biogeography》2023,32(5):747-765