首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献,搜索用时 78 毫秒
1.
2.
The parasitoid wasp family Ichneumonidae is one of the most species-rich groups of organisms, but its fossil record remains very poorly studied, which impedes inferences of the origin of its diversity. We here describe two new fossil genera and five new species of Ichneumonidae from the Eocene Green River Formation: Carinibus molestus gen. et sp. nov., Ichninsum appendicrassum gen. et sp. nov., Mesoclistus? yamataroti sp. nov., Scambus? mandibularis sp. nov., and Scambus? parachuti sp. nov. The newly described Mesoclistus? yamataroti represents the first record of the subfamily Acaenitinae from this fossil locality. In addition, we revise the ten previously described fossil ichneumonids from the Green River Formation, following a conservative approach when re-assessing their taxonomic positions: we keep the current placement of six revised fossils, but express the uncertainty in genus-assignment according to open nomenclature rules: Eclytus? lutatus Scudder, Glypta? transversalis Scudder, Pimpla? eocenica Cockerell, Phygadeuon? petrifactellus Cockerell, Plectiscidea? lanhami Cockerell and Rhyssa? juvenis Scudder. We exclude three fossil genera from their current subfamilies and place them within Ichneumonidae incertae subfamiliae: Eopimpla Cockerell, Lithotorus Scudder and Tilgidopsis Cockerell. Furthermore, we move Tryphon amasidis Cockerell and LeVeque to the new genus Trymectus gen. nov. In the light of these revisions, we discuss the importance of careful taxonomic placement of fossils and difficulties in ichneumonid palaeontology caused by host-related homoplasies and a lack of knowledge about the age of the recent subfamilies.  相似文献   

3.
Small collections of leptostracans (4 specimens and 1 defective specimen) was collected with the help of the epibenthic sledge (EBS) in August 2012 in the deep-sea basin at depth 5245–5421 m in the region to east of the Kuril-Kamchatka Trench during the Russian-German KuramBio expedition. All these specimens relate to two new species of genera Sarsinebalia and Nebaliella from family Nebaliidae. Sarsinebalia pseudotyphlops sp. nov. differ from S. kunyensis, S. cristoboi and S. urgorrii by compound eyes gud. Eyes of S. pseudotyphlops have not discernible ommatidia and pigment. S. pseudotyphlops differ from S. typhlops and S. biscayensis by next characteristic: supra-orbital plate of S. pseudotyphlops reach only basal third of eye dorsally; antennular flagellum is 1.6 length of antennular scale; S. pseudotyphlops has 2-segmented endopod of maxilla 2; lateral border of furcal rami is by this species smooth, without set; exopod of pleopod 1 has by S. pseudotyphlops with 7 small and 2 long spines on dorsolateral border and 1 stout spine and 4 very long setae on apex; protopod of pleopod 4 has by S. pseudotyphlops on distal border between exopod and endopod nearly rectangular process. Moreover, S. pseudotyphlops differ from two other species of compound and arming of pleopods 5 and 6. Nebaliella kurila sp. nov. separate from the other species of Nebaliella the unique characters of compound articles 1 and 2 on peduncle of antenna, exopod of pleopod 1, and minimal value for this genus ratio length of pleopod 6 to length of pleonite 6. Moreover, N. kurila has carina on anterolateral lower corner of carapace; ratio of the rostral flange to exposed keel 1:1; 6-segmented palp of maxilla 1 and endopod of toracopod 8; and has not proximalventral tuberculate process on rostrum and stout spinulose process on article 2 of mandibular palp.  相似文献   

4.
5.
A multivariate morphometric study of the genus Nicoraepoa was carried out to examine patterns of morphological variation among the species and to identify additional characters to allow a clearer delimitation among species. Nicoraepoa is a taxonomically complex genus comprising seven species endemic to South America. Although most of the species are well delimited, two of them, N. andina and N. chonotica, are morphologically similar and very difficult to separate. The morphological variation among species, with overlapping morphological characters, pseudovivipary and possible hybridization make species boundaries unclear. In the present paper, sixty-seven characters were scored for a total of 216 specimens and analyzed using ordination, cluster and discriminant analyses. Based on multivariate results, we recognized species groups and morphological diagnostic characters that allow clearer species delimitation. As a result, N. chonotica has been transferred to N. andina as a subspecies that inhabit southern Patagonia. Other taxa could be recognized and delimited by diagnostic characters: N. erinacea, N. pugionifolia, N. stepparia, N. subenervis subsp. spegazziniana and N. subenervis subsp. subenervis. Moreover, we discuss the possibility that a new species from Bolivia, based on only one specimen, closely related to N. subenervis should be ascribed in Nicoraepoa.  相似文献   

6.
The tadpole shrimp Triops cancriformis (Branchiopoda, Eucrustacea) is often referred to as a “living fossil.” This term implies that the morphology of a species has barely changed for hundreds of millions of years; in the case of T. cancriformis, for about 200 million years. In 1938, Trusheim documented fossil notostracans from the Upper Triassic of southern Germany (237–200 million years) and named them T. cancriformis minor due to their small size compared to modern forms of T. cancriformis. We compared the ontogenetic sequence of the fossil forms to that of modern forms. Fossil material came from the Museum Terra Triassic in Euerdorf and originated from the same geological formation (the Hassberge Formation) as the Trusheim material, which is considered to be nearly entirely lost. The specimens were documented using cross-polarized light and processed into high-resolution images. Fluorescence microscopy was used to document exuviae and carcasses of extant representatives of T. cancriformis. Both forms showed an elongation and similar trends in the length/width ratio of the shield during ontogeny. However, differences were found in the starting point of the developmental processes. Fossil forms start out with a more roundly shaped shield, which becomes more elliptical, while extant forms already start with a more elliptical shield shape. Further differences between extant and fossil forms were found upon comparing shield to trunk ratios. All differences are highly significant statistically. These differences in ontogeny cast severe doubt on the interpretation that T. cancriformis has been static for 237 million years. While the term “living fossil” is misleading and its use should be discouraged in general, it seems to be especially inappropriate to apply it to T. cancriformis.  相似文献   

7.
8.
Extant sea otters (Enhydra lutris) are remarkably well understood in terms of behavior, ecology, and interactions with humans, but the evolutionary history of this charismatic marine mammal is limited owing to a fragmentary fossil record. Disagreements over the generic assignment of various fossil otter remains to members of the tribe Enhydrini, and limited geochronologic data for these records have impeded attempts to interpret the evolutionary biogeography of Enhydra. A well-preserved femur of Enhydra sp. from a middle Pleistocene horizon within the Merced Formation of northern California is the oldest record of Enhydra in the Pacific with robust geochronologic age control. Bracketing 87Sr/86Sr dates indicate an age of 620–670 ka. Reappraisal of the geochronologic age of various occurrences of Enhydrini indicate dispersal of Enhydra into the Pacific through the Bering Strait no earlier than the middle Pleistocene. Somewhat older early Pleistocene fossils of Enhydra from Alaska and England suggest an Arctic or North Atlantic origin of the Enhydra lineage.  相似文献   

9.
The species status of a rare species Eumicrotremus eggvinii from the family Cyclopteridae has been revalidated. Some authors considered its specimens as males of close species E. spinosus. In the Zoological Institute collection, males of E. spinosus that are morphologically similar with females of this species have been found. This is evidence of absence of sexual dimorphism in E. spinosus. In new samplings from waters of the Franz Josef Land archipelago (Barents Sea), a specimen of E. eggvinii was found and described. The opinion of some authors that individuals of E. eggvinii represent males of E. spinosus is refuted. A new finding widens the species area to the northeastern limits of the Barents Sea. The number and character of distribution of bone plaques remain reliable taxonomic characters.  相似文献   

10.
11.
Relationships among numerous specimens of Drepanocladus angustifolius (35 specimens), Drepanocladus lycopodioides (71 specimens), and Drepanocladus turgescens (102 specimens) are analysed based on the nuclear internal transcribed spacers 1 and 2 (ITS) and a portion of glyceraldehyde 3-phosphate dehydrogenase (gpd), and the plastid rpl16 G2 intron. Molecular data suggest that neither species is monophyletic as well as significant incongruence among molecular markers. No statistical support for recombination (ITS, gpd) was found. For some D. lycopodioides and D. turgescens specimens, the molecular information even suggests that they belong to the wrong one of these two species. All such specimens were collected in south Swedish areas where the two species are frequently found growing together and where sporophytes are often common. The occurrence of all such specimens only in these geographical areas is statistically unlikely and suggests that hybridisation occasionally occurs here. While molecular information suggests that the species are not monophyletic, geographical signals could be found for both D. angustifolius and D. turgescens.  相似文献   

12.
It is known that the genus Waminoa (order Acoela, Family Convolutidae) associates with anthozoans (Scleractinia, Octocorallia, Zoantharia) and feeds on the mucus of their host. Despite the close relationship between Waminoa and its host species, it is known from phylogenetic analyses of sequences of the internal transcribed spacer 2 of ribosomal DNA (ITS-2) that photosymbiotic Symbiodinium isolated from Waminoa are different from the Symbiodinium of their anthozoan hosts. Additionally, Waminoa inherit their Symbiodinium and Amphidinium via vertical transmission. In the current study, we looked for and collected Waminoa from different anthozoan hosts from the Ryukyu Archipelago in southern Japan, and then examined the Symbiodinium of Waminoa as well as hosts’ Symbiodinium, and utilized sequences of the hyper-variable non-coding region of the plastid minicircle (psbAncr) in order to re-examine the diversity of Symbiodinium within Waminoa. In the resulting psbAncr phylogenetic tree, all Symbiodinium within Waminoa comprised a unique group within Clade C, all with the same genotype in the psbAncr phylogenetic tree. Our results reconfirm that most Waminoa host their own lineage of Symbiodinium, and demonstrate that Waminoa are also found on azooxanthellate anthozoan hosts, as we found Waminoa on Siphonogorgia sp., expanding their potential known habitat. Additionally, two Symbiodinium from Waminoa from both shallow (4 m) and mesophotic (32 m) depths were not included in main group of Symbiodinium from Waminoa in the ITS-2 phylogenetic tree, although we could not acquire psbAncr sequences for these specimens. Therefore it is possible that undetected Symbiodinium diversity may yet exist within Waminoa, and future work at shallow to mesophotic depths examining both zooxanthellate and azooxanthellate hosts may find more Waminoa and Symbiodinium diversity.  相似文献   

13.
In congenital hyperinsulinism of infancy (CHI), the loss of K-ATP channels (composed of Kir6.2 and SUR1 subunits) in β cells induces permanent insulin secretion and severe hypoglycaemia. By contrast, Sur1 ?/? mice do not present such defects. We have investigated the impact of Sur1 gene inactivation on mouse islet cell morphology, structure and basic physiology. Pancreata were collected from young, adult and old wild-type (WT) and Sur1 ?/? mice. After immunostaining for hormone, the total endocrine tissue, cell proportion, cell size and intra-insular distribution, hormone content and Glut-2 expression were quantified by morphometry. Basic physiological parameters were also measured. In young Sur1 ?/? mice, the total endocrine tissue and proportion of β cells were higher (P<0.05) than in WT mice, whereas the proportion of δ cells was lower (P<0.01). In old Sur1 ?/? mice, α cells were frequently located in the central regions of islets (unlike WT islets) and their proportion was increased (P<0.05). Glut-2 protein and mRNA levels were lower in old Sur1 ?/? islets (P<0.02). Insulinaemia, fasting insulin and glucagon contents were equivalent in both groups of pancreata. Thus, the islets of Sur1 ?/? mice present morphological modifications that have not been described in CHI and that might reflect an adaptive mechanism controlling insulin secretion in these mice.  相似文献   

14.
Phylogenetic analysis based on osteological characters of some Neogene and Recent phasianids is performed. Phylogenetic tree shows close relationships of Plioperdix with Ammoperdix and Tologuica with Excalfactoria. Chauvireria is at the base of the clade (Alectoris + (Coturnix + (Excalfactoria + Tologuica))). Palaeoperdix is relatively close to the lineage of large pheasants.  相似文献   

15.
16.
17.
18.
19.
Analysis of abnormal phenotypes produced by different types of mutations has been crucial for our understanding of gene function. Some floxed alleles that retain a neomycin-resistance selection cassette (neo cassette) are not equivalent to wild-type alleles and provide useful experimental resources. Pax6 is an important developmental gene and the aim of this study was to determine whether the floxed Pax6 tm1Ued (Pax6 fl ) allele, which has a retained neo cassette, produced any abnormal eye phenotypes that would imply that it differs from the wild-type allele. Homozygous Pax6 fl/fl and heterozygous Pax6 fl/+ mice had no overt qualitative eye abnormalities but morphometric analysis showed that Pax6 fl/fl corneas tended be thicker and smaller in diameter. To aid identification of weak effects, we produced compound heterozygotes with the Pax6 Sey-Neu (Pax6 ?) null allele. Pax6 fl/? compound heterozygotes had more severe eye abnormalities than Pax6 +/? heterozygotes, implying that Pax6 fl differs from the wild-type Pax6 + allele. Immunohistochemistry showed that the Pax6 fl/? corneal epithelium was positive for keratin 19 and negative for keratin 12, indicating that it was abnormally differentiated. This Pax6 fl allele provides a useful addition to the existing Pax6 allelic series and this study demonstrates the utility of using compound heterozygotes with null alleles to unmask cryptic effects of floxed alleles.  相似文献   

20.
THE mi-1 (poky) strain of Neurospora crassa is a relatively stable, respiration-deficient mutant, which exhibits cyto-plasmically-inherited reduction of growth rate and aberrations in the mitochondrial eytochrome system. In young cultures of mi-1, the cells accumulate up to sixteen times the amount of cytochrome c present in wild-type Neurospora and cytochromes b and a are not detectable spectroscopically in these same cells1. In sexual crosses the mi-1 mutation is transmitted only through the cytoplasm of the protoperithecial parent and the pleiotropic mi-1 phenotype is caused by an alteration in a cytoplasmic gene2, presumably in the mitochondrial DNA.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号