Olga Ezhova

Olga Ezhova
Lomonosov Moscow State University | MSU · Department of Invertebrates Zoology

PhD

About

50
Publications
12,168
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101
Citations
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February 2006 - present
Lomonosov Moscow State University
Position
  • Professor (Associate)

Publications

Publications (50)
Article
Full-text available
Trematodes found in the enteropneust hemichordates are described for the first time. Metacercariae have been found in the trunk coelom, in the collar coelom, in the proboscis coelom, and in the glomerulus of the deep-sea torquaratorid Quatuoralisia malakhovi Ezhova et Lukinykh, 2022. This is the first find of parasites in the glomerulus of acorn wo...
Article
Five species of deep-sea acorn worms (Enteropneusta) were found in the Bering Sea during cruises of the RV Akademik M.A. Lavrentyev in 2016, 2018, and 2021. The worms were recorded on slopes of the Volcanologists Massif and in the Komandorsky Graben at depths between 1830 and 4278 m and on the Koryak slope between 419 and 662 m. Four of the species...
Article
The representatives of the main phylogenetic clades of Bilateria are characterized by metamery. In Deuterostomia, metamery is presented in hemichordates and chordates. Sea urchins have 7 metameric coelomic rings located along the oral-aboral axis of the body. A similar coelomic metamery is also a sign of representatives of other classes of echinode...
Article
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Deep-sea hemichordates Torquaratoridae gen. sp. reach high abundance up to 12 spec. m-2 at the depths of 1830-2130 m on the slope of the Volcanologists Massif in the south-western part of the Bering Sea, dominating in the benthic community at these depths. Their abundance exceeds by two orders the values recorded earlier. In order to clarify this p...
Article
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The anatomy of Crinoidea differs from that of the other modern echinoderms. In order to see, whether such differences extend to the axial complex as well, we studied the axial complex of Himerometra robustipinna (Himerometridae, Comatulida) and compared it with modern Eleutherozoa. The axial coelom is represented by narrow spaces lined with squamou...
Article
Full-text available
The gill skeleton of the enteropneust Saccoglossus mereschkowskii consists of a series of tridents. The central prong of each trident bifurcates in its ventral end. The most anterior gill skeletal element has a simple horseshoe shape. Homologues of the elements of the enteropneust gill apparatus were found in the structure of the gill apparatus of...
Article
Internal gonad morphology was examined in two species of elpidiid holothurians, Elpidia heckeri and Kolga hyalina, commonly occurring in the Central Arctic Ocean. The holothurians were sampled in August – September 2012 and in August 2018, at several locations in the Nansen and Amundsen Basins, in areas under the constant ice cover and in areas fre...
Article
Full-text available
Histological examination of a specimen of a deep-sea enteropneusts that belongs to a yet undescribed species (Torquaratoridae gen. sp.) revealed numerous trunk coelomoducts. They open into the genital wing coelom as a typical funnels; short ducts communicate with environment through pores located on the outer side of the genital wings. Total number...
Article
Full-text available
Studies of echinoid microscopic anatomy over the last two centuries have created a number of inaccuracies and mistakes that have accumulated in the descriptions of the intricate organization of the coelomic system of Echinoidea. To clarify the situation, we reconstructed the axial complex and radial complex of the echinoid Strongylocentrotus pallid...
Article
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The absence of axial and pericardial coeloms and the axial organ, presence of a mesocoelomic tentacular apparatus, correspondence of the larval sagittal plane with the madreporic plane of the adult, and some other peculiarities set holothurians apart from all other echinoderms. We studied the holothuroid Chiridota laevis with histological methods a...
Article
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In comparison with Asteroidea, the axial complex of ophiuroids has some important features, which are the result of shifting of the madreporite from the aboral side to the oral side. In contrast to Asteroidea, the stone canal of ophiuroids connects with the water ring from the outside, not from the inside. In Ophiuroidea, the somatocoelomic perihae...
Article
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The madreporite of brittle stars is poorly studied, and the features of its structure are rarely used in the taxonomy. However, it is known that there is diversity in the madreporite structure. But are the ophiuroid madreporites phylogenetically informative? To check this hypothesis, we investigated the structure of the madreporite of 33 species of...
Article
Full-text available
The ultrastructure of the axial organ of Asterias amurensis has been studied The organ is a network of canals of the axial coelom separated by haemocoelic spaces. The axial coelom is lined with two types of monociliary cells: podocytes and musculo-epithelial cells. Podocytes form numerous basal processes adjacent to the basal lamina on the coelomic...
Article
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Metameric gill slits are mysterious structures, unique for Chordata and Hemichordata, and also, perhaps, for the extinct Cambrian Calcichordata. There is a discussed hypothesis of the gill slits origin from the metameric nephridia. According to the hypothesis, the hypothetical metameric deuterostome ancestor had in each segment a pair of coelomoduc...
Article
Full-text available
Several details of the anatomy of the axial complex in brittle stars remain unknown, and there are many mismatching descriptions of its structure in different sources. The comparison of the ophiuroid axial complex with other classes of echinoderms is important for understanding of the phylogenetic relations in Ophiuroidea. We describe the organizat...
Conference Paper
В ходе эволюции мадрепоровая пластинка офиур постепенно поворачивалась с аборальной стороны (где она находится у всех остальных Asterozoa) на оральную сторону вдоль интеррадиуса CD, и это подтверждено исследованиями эмбрионального развития офиур. Такой сдвиг не мог не затронуть – вслед за мадрепоритом – каменистый канал и весь осевой комплекс офиур...
Conference Paper
Full-text available
В ходе эволюции мадрепоровая пластинка офиур постепенно поворачивалась с аборальной стороны (где она находится у всех остальных Asterozoa) на оральную сторону вдоль интеррадиуса CD, и это подтверждено исследованиями эмбрионального развития офиур. Такой сдвиг не мог не затронуть – вслед за мадрепоритом – каменистый канал и весь осевой комплекс офиур...
Conference Paper
Full-text available
В ходе эволюции мадрепоровая пластинка офиур постепенно поворачивалась с аборальной стороны (где она находится у всех остальных Asterozoa) на оральную сторону вдоль интеррадиуса CD, и это подтверждено исследованиями эмбрионального развития офиур. Такой сдвиг не мог не затронуть – вслед за мадрепоритом – каменистый канал и весь осевой комплекс офиур...
Conference Paper
В ходе эволюции мадрепоровая пластинка офиур постепенно поворачивалась с аборальной стороны (где она находится у всех остальных Asterozoa) на оральную сторону вдоль интеррадиуса CD, и это подтверждено исследованиями эмбрионального развития офиур. Такой сдвиг не мог не затронуть – вслед за мадрепоритом – каменистый канал и весь осевой комплекс офиур...
Conference Paper
В ходе эволюции мадрепоровая пластинка офиур постепенно поворачивалась с аборальной стороны (где она находится у всех остальных Asterozoa) на оральную сторону вдоль интеррадиуса CD, и это подтверждено исследованиями эмбрионального развития офиур. Такой сдвиг не мог не затронуть – вслед за мадрепоритом – каменистый канал и весь осевой комплекс офиур...
Article
Full-text available
We describe and illustrate the morphology of unpaired proboscis skeleton and buccal diverticulum of a hemichordate Saccoglossus mereschkowskii for the first time and compare them to homologous structures in other species. The proboscis skeleton is a unique structure found only in enteropneust hemichordates. It is made of cartilaginous-like material...
Conference Paper
Full-text available
The gill slits are the mysterious structures special only for two phyla of Deuterostomia. It is difficult to image from the evolutionary viewpoint the origin of numerous paired openings leading from the gut to the exterior. We studied the branchial apparatus and the gill skeleton in acorn worm Saccoglossus mereschkowskii by methods of the 3D-recons...
Article
Full-text available
The representatives of Asterozoa (Asteroidea, Echinoidea, and Ophiuroidea) have a similar structural plan of the axial complex with minor differences within each class; this structural scheme substantially differs from that in Crinozoa and Holothurozoa. The axial complex consists of the coelomic organs and the haemocoel (blood) structures, which ar...
Data
The gill slits are the mysterious structures special only for two phyla of Deuterostomia. It is difficult to image from the evolutionary viewpoint the origin of numerous paired openings leading from the gut to the exterior. We studied the branchial apparatus and the gill skeleton in acorn worm Saccoglossus mereschkowskii by methods of the 3D-recons...
Article
Full-text available
The axial complex is one of the most characteristic features of echinoderms. Descriptions of it in classic papers are contradictory. The present paper provides data on the microscopic anatomy of the axial complex in the starfish Asterias rubens restudied using histological techniques. The axial complex is located in the wall of the interradius CD;...
Article
Full-text available
В начале 80-х годов XIX в. профессор Санкт-Петербургского университета Н.П.Вагнер, работая на основанной им Соловецкой биологической станции, исследовал фауну Белого моря и обнаружил небольших червеобразных животных ярко-оранжевого цвета, источающих слабый аптечный запах. Вагнер описал этих животных как новый вид — баляноглосс Мережковского (Balano...
Article
Full-text available
This is the first paper of the series devoted to the microscopic anatomy and fine structure of the skeleton-heart-kidney complex in the acorn worm Saccoglossus mereschkowskii Wagner 1885. The skeleton of S. mereschkowskii consists of the unpaired anterior plate (lamina imparis) and two posterior horns (corni). The anterior plate bears a pair of lat...
Article
Full-text available
It is the fourth report from a series about the microscopic anatomy and fine structure of the skeleton-heartkidney complex in the acorn worm, Saccoglossus mereschkowskii Wagner 1885. The blood network of the glomerulus is divided into two tiers: the inner tier of the vessels directed to the pericardial coelom, and the outer one formed by the vessel...
Article
Full-text available
This paper is the third report on the microscopic anatomy and fine structure of the skeleton-heart-kidney complex in the acorn worm, Saccoglossus mereschkowskii 'Wagner 1885. The dorsal vessel extends within dorsal mesentery between perihaemal coeloms. The wall of a dorsal vessel is made of basement membrane with amebocytes joining internally. Ther...
Article
Full-text available
Второе сообщение из серии, посвященной микроскопической анатомии и ультраструктуре скелетно-рено-перикардиального комплекса органов у кишечнодышащего Saccoglossus mereschkowskii. Буккальный дивертикул S. mereschkowskii состоит из трех частей. Первая часть – основание (basis), состоящее из дорсальной стенки – paries dorsalis с дорсальным желобом – c...
Article
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Первое сообщение из серии публикаций, посвященных микроскопической анатомии и ультраструктуре скелетно-рено-перикардиального комплекса кишечнодышащего Saccoglossus mereschkowskii Wagner 1885. Скелетный элемент S. mereschkowskii состоит из парных рожек (corni) и непарной пластинки (lamina imparis), в составе которой описаны новые морфологические дет...
Article
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Третье сообщение из серии, посвященной микроскопической анатомии и ультраструктуре скелетно-рено-перикардиального комплекса Saccoglossus mereschkowskii. Дорсальный сосуд проходит в толще дорсального мезентерия между перигемальными целомами. Стенка дорсального сосуда образована базальной пластинкой, к которой изнутри прилегают амебоциты. Отмечены де...
Article
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Четвертое сообщение из серии, посвященной скелетно-рено-перикардиальному комплексу Saccoglossus mereschkowskii. Кровеносная сеть гломерулюса разделяется на два яруса: внутренний, образованный сосудами, вдающимися в перикардиальный целом, и наружный, образованный сосудами, вдающимися в полость хоботкового целома. В состав гломерулюса входят эпителиа...
Conference Paper
Full-text available
The unpaired skeleton and the buccal diverticulum are the main supporting structures of collar and proboscis in the Enteropneusta. The skeleton of all enteropneusts includes unpaired anterior plate and paired posterior horns. The buccal diverticulum represents the forward-directed hollow growth of the buccal tube. It consists in most cases of three...
Article
Full-text available
Enteropneusta is one of two classes constituting the phylum Hemichordata, whose representatives are bottom burrowers of marine sediments. Hemichordates have some features that allow them to be considered a group closely related to ancestors of Chordata [1‐3, 5]. One of such features is the development of skeletal formations from connective tissue....
Article
Full-text available
Hemichordates (the phylum Hemichordata) are a small taxon of marine invertebrates considered to be phylogenetically close to the ancestors of chordates. Enteropneusta is a class of Hemichordata whose representatives are burrowing animals living in sea bottom sediments. The microscopic anatomy of Enteropneusta has been described in several classic w...

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