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Abstract. Growth of the shallow-water gorgonian Lophogorgia ceratophyta was investigated in an infralittoral station located in La Spezia Gulf, Ligurian Sea. Mean annual height growth rate was estimated to be 2.57 cm · a-1. The fractal dimension of the colonies was found to gradually evolve in complexity, exhibiting a simpler branching pattern in younger specimens. The maintenance of a low, invariable ramification complexity as an optimal choice in managing relationships between water and the colony's living tissues is also discussed. 相似文献
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Tae-Yoon S. Park Ji-Hoon Kihm Jusun Woo Yong-Yi Zhen Michael Engelbretsen Jongsun Hong Suk-Joo Choh Dong-Jin Lee 《《地质学报》英文版》2016,90(3):827-837
Five species, Lipopora lissa Jell and Jell, 1976, Lipopora daseia Jell and Jell, 1976, Tretocylichne perplexa Engelbretsen, 1993 from Australia, Cambroctoconus orientalis Park, Woo, Lee, Lee, Lee, Han and Chough, 2011 from China, and Cambroctoconus kyrgyzstanicus Peel, 2014 from Kyrgyzstan, belonging to the Cambrian stem-group cnidarians have been documented in the fossil record. Cambroctoconus coreaensis sp. nov., interpreted here as a stem-group cnidarian, from the Seokgaejae section in the Daegi Formation, Taebaek Group (Cambrian Series 3), Taebaeksan Basin, central-eastern Korean Peninsula, has a slender cup-shaped skeleton. A cladistic analysis produced 21 most parsimonious trees, which invariably placed the six stem-group cnidarians below the crown-group, but their relationships within the stem-group are unresolved. Nine out of the 21 trees suggest a monophyletic relationship for the Cambrian stem-group cnidarians, whereas in six other trees a monophyly of Cambroctoconus and Tretocylichne appeared as the sister-group to the crown-group cnidarians with Lipopora at the most basal branch. This result may reflect the fact that crown-group cnidarians evolved in the Precambrian, and suggests that the diversity of stem-group cnidarians was a result of an independent radiation in the Cambrian. 相似文献
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Coral reefs are increasingly threatened worldwide by a variety of biological and physical factors, including disease, bleaching and ocean acidification. Understanding levels of connectivity among widespread populations can assist in conservation efforts and the design of marine protected areas, as larval dispersal scales affect population demography. This study examined genetic connectivity and morphological variation of the broadcast spawning coral Montastraea cavernosa (L., 1767) among five locations in the Caribbean and Western Atlantic. Analysis of mtDNA and nuclear rRNA internal transcribed spacers, at both the local and regional scale, revealed that the majority of variation existed within locations rather than among them. Likewise, the majority of pairwise comparisons were non‐significant between sites and locations. These results suggest that moderate to high gene flow occurs within and among populations of M. cavernosa in the Western Atlantic. The phylogeographic signature and significant pairwise comparisons among several locations, however, indicate that populations are also partially maintained through self‐seeding and that gene flow may be restricted over large geographic distances. Additionally, while some anatomical variation is likely attributable to phenotypic plasticity, variations in skeletal morphology between Jamaica and other locations correspond with significant pairwise genetic distances and the presence of private sequence types (limited to a single location), suggesting selection to local environmental conditions. 相似文献
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Liu Yunhuan Li Yong Shao Tiequan Zhu Zhixin Yu Bo Wang Zhuo Zhang Wanqian Li Rongxi 《Frontiers of Earth Science》2007,1(1):1-11
The appearance of coelenterates marks the real beginning of metazoan evolution. It therefore has a prominent position in the
origin and evolutionary history of organisms, and is also a pivotal question of evolutionary biology. Punctatus is an extinct, ancient marine animal from the early stage of the Cambrian explosion, occurring at the lowermost Cambrian
of both Kuanchuanpu (Ningqiang, Shaanxi) and Maidiping (Emei, Sichuan) areas. Punctatus has been studied for many years since the discovery of its fragments. Systematic and phylogenetic analysis has long been
limited because of the rarity of complete specimens. In order to improve research into Punctatus, more than ten thousand globular fossils were recovered by means of “Chemistry Retting”. On the basis of the study of these
globular fossils, a series of Punctatus fossils with cone parts and finely preserved soft-tissue mouthparts and fossilized metazoan embryo were recovered. Through
research on characteristics such as shape, modality and structure of these fossils symbiotic with Punctatus emeiensis, the author found many possible embryo fossils including the evidence of gastrula-stage animal fossils. The sequence of fetation
might have appeared on the corolliform oral region of Punctatus emeiensis. A study of the soft tissues, functional morphology and the sequence of embryo fossils shows evidence that Punctatus resembles coelenterate polyps in systematic classification. Perhaps it also represents an ancestor of the coelenterate with
an original tentacle. A comparison with the real “tentacle animal” found in the Chengjiang Fauna, shows that the original
tentacle is very tiny and its function range is limited. This reveals the primitive nature of the animal. Although the original
tentacle is so small, it does exist, representing the first big step towards the real flexible tentacle with a strong function
from the early evolving tentacle.
Translated from Journal of Acta Palaeontologica Sinica, 2006, 45(2): 182–194 [译自: 古生物学报] 相似文献
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Medusae in 116 samples collected from the coastal waters of the northern Beibu Gulf during four seasonal oceanographic cruises from October 2017 to August 2018 were analyzed. In total, 34 species were identified. Two of the species are new to science, Proboscidactyla pentacanalis Xu, Chen & Yang sp. nov. and Helgicirrha apapillata Xu, Chen & Wang sp. nov., and three species are newly recorded in the Beibu Gulf, i.e., Hydractinia vacuolata Xu & Huang, 2006, Proboscidactyla flavicirrata Brandnt, 1834 and Phialella macrogona Xu, Huang & Wang, 1985. Collections of the species were deposited at the Third Institute of Oceanography, Ministry of Natural Resources. 相似文献
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Abstract. One of the most critical problems in human efforts to combat consequences of pollution is the proper identification of the initial phases of ecosystem disturbance. Investigation of hydrographic conditions and medusan species composition in the Northern Adriatic region from 1992 to 1997 showed persistence of hypoxic conditions and low numbers of meroplanktonic hydromedusae. The changes observed in the hydromedusan fauna demonstrate one aspect of the long-term consequences of oxygen deficiencies in marine ecosystems: decreased biodiversity. We suggest that the species composition of meroplanktonic hydromedusae may be a useful indicator of the early phase of such changes. 相似文献
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Stefania Puce Giorgio Bavestrello Cristina Gioia Di Camillo & Ferdinando Boero 《Marine Ecology》2009,30(3):313-326
Marine hydroids are markedly seasonal in temperate seas, being extremely sensitive to climatic changes disrupting seasonal patterns. Modifications in the composition, seasonality, bathymetric distribution and reproductive period of hydroid assemblages are useful to evaluate the influence of global warming on the marine ecosystem. The hydroids on the rocky cliff of the Portofino Promontory (Ligurian Sea, Italy) were carefully studied between 1976 and 1983; in particular, in 1980 the study was carried out along a vertical transect. The hydroids were sampled again throughout 2004, with the same techniques and along the same transect. Species diversity decreased slightly in the 2004 survey. Some species present in 1980 had disappeared in 2004, but other species with southern affinity, never recorded from the area, became abundant in 2004. Species that were present in summer in the first period were also present in winter in the second one. Furthermore, shallow summer species widened their bathymetric distribution, reaching deeper levels. These data strongly suggest that the Portofino hydroid assemblage reacted to the water temperature increase found in the Mediterranean Sea. 相似文献
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Lúcia Maria O. Gusmão Xiomara Franchesca G. Diaz Mauro de Melo Jr Ralf Schwamborn Sigrid Neumann‐Leitão 《Marine Ecology》2015,36(1):93-103
Jellyfish are often the most prominent components of plankton, with severe consequences for fisheries and tourism. However, in tropical regions, there is much uncertainty about these consequences due to the lack of basic data. Our objective was to improve the knowledge about jellyfish in the Western Atlantic, with an emphasis on understanding diversity, abundance, and distribution patterns. Samples were collected at 34 stations in 1995 using a 300‐μm‐mesh Bongo net. The 21 species identified belonged to Hydromedusae (11), Siphonophora (nine), and Scyphomedusae (one). The overall mean density was low (5.2 ± 5.3 ind. m?3). Total Hydromedusae biomass was 130.86 mg C m?3, and total Siphonophora biomass was 19.04 mg C m?3. Chelophyes appendiculata (Eschscholtz, 1829) was the most frequent species captured in the oceanic samples, and Aglaura hemistoma (Péron & Lesueur, 1810) was the most common in the neritic region. The latter species is sometimes characterized as a bloom associated with the most polluted and eutrophic river plumes. The main role of jellyfish species in the area is as a higher‐order carnivore. A cross‐shelf significant difference (P < 0.05) was registered, with higher species numbers in oceanic regions and higher densities and biomass in neritic regions. 相似文献