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641.
The new genus 2Burmasphex is proposed for two fossil species, 2Burmasphex sulcatus sp. nov. and 2Burmasphex pilosus sp. nov., described from Myanmar Cretaceous amber. It exhibits many plesiomorphic features in relation to the extant Apoidea and is here provisionally allocated in the extinct family 2Angarosphecidae. 相似文献
642.
《Journal of Asia》2023,26(2):102060
A new Mesozoic webspinner (Embiodea) is described and figured based on a moderately well-preserved male in mid-Cretaceous (earliest Cenomanian) amber from northern Myanmar. Perissoclothoda myrrhokaris gen. et sp. nov. is the second fossil representative of the putatively primitive family Clothodidae. It differs from the Cretaceous and more recent Embiodea in several plesiomorphic characters, namely a quadrate mentum, approximately oval submentum, subgenae not meet medially (thus a ventral bridge or gula is lacking), completely symmetrical terminalia, and dimerous cerci. This new find sheds further light on the diversity and morphological disparity of fossil webspinners during the Late Mesozoic.www.zoobank.org/urn:lsid:zoobank.org:pub:11A49D4A-4042-4AA3-858F-919E1A84B879. 相似文献
643.
Michael G. Boegle Susanne Schneider Beate Mannschreck Arnulf Melzer 《Hydrobiologia》2007,586(1):155-166
644.
Karl Dahmen 《International Review of Hydrobiology》1999,84(3):271-286
Mesozooplankton production was estimated by using a new sampling technique and two alternative calculation methods. In essence, production estimates are based on significantly higher abundances. The contribution of juvenile stages to copepod and fish dynamics was generally low, so that the omission of juvenile stages in budgets will result in a small error. The situations reported in this study present a unique food web szenario, which in detail, however, was strongly dependent on methodology. Furthermore, relations between trophic levels were considered with respect to vertical distribution. 相似文献
645.
The first fossil species of a Melissotarsus ant is described (Melissotarsus ethiopiensis n. sp.), suggesting that Ethiopian amber could be cenozoic rather than cretaceous. This hypothesis is supported by a Fourier transform infrared spectroscopy (FTIR) analysis of the amber itself, suggesting a weak maturation of the fossil resin, and a revision of the pyrolysis–gas chromatography–mass spectrometry (PY-GC-MS) analysis done by Schmidt and his collaborators in 2010, in an article in which the deposit was described for the first time. 相似文献
646.
647.
Selectivity of fishing gears used in the Baltic Sea cod fishery 总被引:1,自引:0,他引:1
Niels Madsen 《Reviews in Fish Biology and Fisheries》2007,17(4):517-544
The Baltic cod (Gadus morhua) plays a very significant role in the Baltic Sea ecosystem being the major fish top predator and the most important commercial
species for the Baltic Sea fishing industry. Consequently the management and understanding of the exploitation pattern of
the stock is of major importance. Technical regulations, improving the selectivity of cod, have been a major management strategy
and the Baltic Sea is likely to be the area where most fishing gear selectivity studies, focussing on size selectivity, have
been conducted over time. The methodology for conducting and analysing selectivity data has been significantly improved in
recent years. The subject is reviewed since the choice of methodology can have a significant effect on the interpretation
of the outcome of selectivity experiments. Factors affecting the selectivity of trawl and gill nets are considered. Alternative
ways to improve the size and species selectivity of trawls using selective devices are reviewed. Selectivity parameters from
available literature are listed and the correlations of selectivity parameters to the mesh size for different gears are estimated.
The historical legislation on selectivity is reviewed and the expected selectivity for trawls is estimated. Management considerations
concerning the mortality of escaping and discarded fish and wider management impacts have to be considered if improving selectivity.
The review is ended by conclusions including reflections on needed research in the future. 相似文献
648.
We used electrophoretically identified material to assess the geographical distributions, life cycles and interspecific hybridization
of two sibling species of the Mysis relicta species group (sp. I and sp. II) in the northern Baltic region. In the Gulf of
Finland, sp. I prevails in inshore waters and sp. II in the open sea; the distributions overlap in the outer archipelago zone.
In the Gulf of Bothnia, only sp. II was found in the southern part (Bothnian Sea), whereas the two species coexist throughout
the northerly Bothnian Bay. Both the local and large-scale distributions are salinity-related, but salinity alone does not
explain the differences. The two species exhibit different patterns of geographical variation in their life histories. In
strict sympatry in the north they have identical two-year life cycles with winter breeding. Further south (Gulf of Finland),
sp. I exhibits a predominantly one-year winter-breeding cycle, whereas sp. II breeds throughout the year. The patterns comply
with the concept of a great phenotypic flexibility and environmental control of life history characteristics in the Mysis
relicta group, and make a contrast to the stable life cycle of the congeneric M. mixta. F1 hybrids between the two M. relicta
group species were found at a low frequency (0.6%) in the Bothnian Bay, but not in other areas of sympatry.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
649.
David Peris Xavier Delclòs Bjarte Jordal 《Biological reviews of the Cambridge Philosophical Society》2021,96(6):2476-2488
Insect–fungus mutualism is one of the better-studied symbiotic interactions in nature. Ambrosia fungi are an ecological assemblage of unrelated fungi that are cultivated by ambrosia beetles in their galleries as obligate food for larvae. Despite recently increased research interest, it remains unclear which ecological factors facilitated the origin of fungus farming, and how it transformed into a symbiotic relationship with obligate dependency. It is clear from phylogenetic analyses that this symbiosis evolved independently many times in several beetle and fungus lineages. However, there is a mismatch between palaeontological and phylogenetic data. Herein we review, for the first time, the ambrosia system from a palaeontological perspective. Although largely ignored, families such as Lymexylidae and Bostrichidae should be included in the list of ambrosia beetles because some of their species cultivate ambrosia fungi. The estimated origin for some groups of ambrosia fungi during the Cretaceous concurs with a known high diversity of Lymexylidae and Bostrichidae at that time. Although potentially older, the greatest radiation of various ambrosia beetle lineages occurred in the weevil subfamilies Scolytinae and Platypodinae during the Eocene. In this review we explore the evolutionary relationship between ambrosia beetles, fungi and their host trees, which is likely to have persisted for longer than previously supposed. 相似文献
650.
The chemical character and burial of phosphorus in shallow coastal sediments in the northeastern Baltic Sea 总被引:1,自引:0,他引:1
The chemical composition and vertical distribution of sediment phosphorus (P) in shallow coastal sediments of the northeastern
Baltic Sea (BS) were characterized by sequential extraction. Different P forms were related to chemical and physical properties
of the sediments and the chemistry of pore water and near-bottom water. Sediment P composition varied among the sampling sites
located in the Archipelago Sea (AS) and along the northern coast of the Gulf of Finland (GoF): the organic rich sites were
high in organic P (OP), while apatite-P dominated in the area affected by sediment transportation. Although the near-bottom
water was oxic, the sediments released P. Release of P was most pronounced at the site with high sediment OP and reduced conditions
in the sediment-water interface, indicating that P had its origins in organic sources as well as in reducible iron (Fe) oxyhydroxides.
The results suggest that even though these coastal areas are shallow enough to lack salinity stratification typical for the
brackish BS, they are vulnerable to seasonal oxygen (O2) depletion and P release because of their patchy bottom topography, which restricts mixing of water. Furthermore, coastal
basins accumulate organic matter (OM) and OP, degradation of which further diminishes O2 and creates the potential for P release from the sediment. In these conditions, an abundance of labile OP may cause marked
efflux of P from sediment reserves in the long-term. 相似文献