The early Cambrian pentamerous microfossil Olivooides/Punctatus in South China, which is characterized by a diagnostic stellate tubular apex, has been well-known for its almost complete development sequence that can b...The early Cambrian pentamerous microfossil Olivooides/Punctatus in South China, which is characterized by a diagnostic stellate tubular apex, has been well-known for its almost complete development sequence that can be confidently traced from embryos and hatched juveniles, to conical adults. However, its zoological affinity remains highly controversial. Here we describe the internal microanatomic structures of the soft-body inside the peridermal theca of Olivooides multisulcatus Qian, 1977, including interradial pairs of tentacles, adradial and perradial frenula, perradial oral marginal lappets and twins of perradial gastric saccule-like humps as well as a circular velarium with striated coronal muscles. Particularly, one specimen shows bifurcated velarial canals along the bell aperture. Both the components of the soft-body and the external theca （or cyst） are arranged in perfect pentaradial symmetry. These characteristics are more compatible with those of living cubomedusans and co-occurring Cambrian athecate embryonic cubozoans. Concerning the presence of peridermal theca, Olivooides most likely represents an extinct thecate stem-group cubomedusae but devoid of both perradial eyes and specialized pedalia. The well-grown soft body inside the peridermal tube displays a set of mixed features of both polyp and medusa.展开更多
In order to study the segregated distribution of the three most abundant jellyfish species in the southern Gulf of Mexico, a total of 85 stations were sampled during an oceanographic cruise from 19 May to 18 June 2006...In order to study the segregated distribution of the three most abundant jellyfish species in the southern Gulf of Mexico, a total of 85 stations were sampled during an oceanographic cruise from 19 May to 18 June 2006. Trawling took place from surface to a maximum depth of 200 m, using a Bongo net with a 61 cm mouth diameter and 333 and 500 μm mesh sizes. Temperature and salinity were recorded. Samples were preserved in 4% formalin, neutralized with sodium borate, and changed to 70% ethylic alcohol after 24 hours for conservation. The jellyfish data were standardized to 100 m<sup>3</sup> of filtered water. A total of 10,610 jellyfish were collected from the 333 μm mesh size net, of which eight species represented 88.49% of the total density: Aglaura hemistoma, Liriope tetraphylla, Nausithoe punctata, Clytia hemisphaerica, Persa incolorata, Obelia spp., Clytia folleata and Eutima gracilis. The former three species are the subject of this study. The results obtained indicate that the high density areas of these three species have a segregated distribution. Segregation values (White’s index) recorded between pairs of specie were very high: L. tetraphylla - A. hemistoma, 0.88;L. tetraphylla - N. punctata, 0.86 and A. hemistoma - N. punctata, 0.84. The spatial distribution of the high density areas of these species fits well with the three hydrodynamically different areas: A. hemistoma in Campeche Bank, L. tetraphylla on the Campeche and Tabasco shelves and N. punctata in Campeche Bay. This spatial distribution pattern corresponds to their main habitat and reproductive habits of the species, as well as the influence of the hydrodynamics that dominate each area.展开更多
基金supported by the Natural Science Foundation of China(NSFC grant 41272019,41372021)the "973 project" of the Ministry of Science and Technology of China"(2013CB835002, 2013CB837100)+1 种基金the "111 project" of the Programs of Introducing Talents of Discipline to Universities(No: W20136100061)the MOST Special Fund from the State Key Laboratory of Continental Dynamics,Northwest University,China
文摘The early Cambrian pentamerous microfossil Olivooides/Punctatus in South China, which is characterized by a diagnostic stellate tubular apex, has been well-known for its almost complete development sequence that can be confidently traced from embryos and hatched juveniles, to conical adults. However, its zoological affinity remains highly controversial. Here we describe the internal microanatomic structures of the soft-body inside the peridermal theca of Olivooides multisulcatus Qian, 1977, including interradial pairs of tentacles, adradial and perradial frenula, perradial oral marginal lappets and twins of perradial gastric saccule-like humps as well as a circular velarium with striated coronal muscles. Particularly, one specimen shows bifurcated velarial canals along the bell aperture. Both the components of the soft-body and the external theca （or cyst） are arranged in perfect pentaradial symmetry. These characteristics are more compatible with those of living cubomedusans and co-occurring Cambrian athecate embryonic cubozoans. Concerning the presence of peridermal theca, Olivooides most likely represents an extinct thecate stem-group cubomedusae but devoid of both perradial eyes and specialized pedalia. The well-grown soft body inside the peridermal tube displays a set of mixed features of both polyp and medusa.
文摘In order to study the segregated distribution of the three most abundant jellyfish species in the southern Gulf of Mexico, a total of 85 stations were sampled during an oceanographic cruise from 19 May to 18 June 2006. Trawling took place from surface to a maximum depth of 200 m, using a Bongo net with a 61 cm mouth diameter and 333 and 500 μm mesh sizes. Temperature and salinity were recorded. Samples were preserved in 4% formalin, neutralized with sodium borate, and changed to 70% ethylic alcohol after 24 hours for conservation. The jellyfish data were standardized to 100 m<sup>3</sup> of filtered water. A total of 10,610 jellyfish were collected from the 333 μm mesh size net, of which eight species represented 88.49% of the total density: Aglaura hemistoma, Liriope tetraphylla, Nausithoe punctata, Clytia hemisphaerica, Persa incolorata, Obelia spp., Clytia folleata and Eutima gracilis. The former three species are the subject of this study. The results obtained indicate that the high density areas of these three species have a segregated distribution. Segregation values (White’s index) recorded between pairs of specie were very high: L. tetraphylla - A. hemistoma, 0.88;L. tetraphylla - N. punctata, 0.86 and A. hemistoma - N. punctata, 0.84. The spatial distribution of the high density areas of these species fits well with the three hydrodynamically different areas: A. hemistoma in Campeche Bank, L. tetraphylla on the Campeche and Tabasco shelves and N. punctata in Campeche Bay. This spatial distribution pattern corresponds to their main habitat and reproductive habits of the species, as well as the influence of the hydrodynamics that dominate each area.
