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6значения, а важным е лише параметр маси води, що випа-рена з одиниц площи, яка залежить вщ опромшення озера сонцем, а вщповщно - вщ кута наклону сонця.
Пщвищення кута сонця ведет до того, що в першу
чергу зменшуеться час освiтлення noBepxHi озера. Змшюючи параметри Т1 i Т2 у формулi 8 вiдповiдних лшш-них параметрiв озера можна получити загальш витрати води на випарування.
l=2h 1=1.5h l=h
Рис.2. Вплив розмiрiв системи "озеро-рослиншсть" на кут освтлення дзеркала озера сонцем. l - дiаметр озера, h - висота дерев на його березк
Якщо озеро не мае рослинного покрова (що прий-нято за 100 % об'ема випарування), то у випадку, коли висота дерев на березi дорiвнюе радiусу озера (а=30° на рис.1), то зменшення втрат води складае 20 - 25 %. Для "модельного" озера вщповщно розрахованим витратам це складае 21 т води за добу.
Очевидно, що до мошторингу стану водних обТеклв вимагае цтого ряду сучасни пiдходiв [2], включаючи тi, як часто не враховуються, оскiльки е "стандартними" для да-ноТ мкцевосл. Але насправдi, сучасний змiни природи в багатьох випадках "антропогенш", i в першу чергу це вщносяться до стану лiсiв у степових зонах. Тому, оцшку балансу води треба проводить з врахуванням зелених насаджень, як споконвту оточують (або оточували) лю-бий водний об'ект, включаючи озера та рiчки.
За результатами роботи можна зробити наступш випадки:
1. Вщ висоти рослинного покриву берепв озер залежить енергетична ефектившсть освiтлення Тх по-верхнi;
2. Пiдвищення висоти приберегових раслинних по-кривiв ведет до суттевого зменшення випарювання води з озера. У найкращому (при вщсутносл ветрi) випадку економiя може складати 40 % випаруваноТ води;
3. Вказаш ефекти бiльш суттевi для маленьких озер, чий дiаметр близький до висоти дерев, ям оточуе озеро. Та навпаки, для великих озер економiя води за рахунок пригшчення випарування - змен-шуеться;
Список л^ератури
1. Айдаркина Е.Е. Мониторинг состояния водных ресурсов Ростовской области // Гуман. и соц. науки.-
2012.- № 5.- С. 53-62.
2. Гостищев В.Д., Сахаров Р.Ю., Кузьмичёв А.А. Современный подход к государственному мониторингу поверхностных водных объектов // Науч. ж. Рос. НИИ проблем мелиорации.- 2012.- № 1.- С. 157165.
3. Егоркина Г.И., Зарубина Е.Ю. Экологический мониторинг водоемов с использованием циторенетиче-ских характеристик высших водных растений // Тез. докл. респуб. конф." Региональное природопользование и экол. мониторинг".- Институт водных и экол. проблем СО РАН, Алтайский гос. ун-т.- 1996. С. 239-240.
4. Мокин В.Б. Оптимальная геоинформационная модель региональной системы государственного мониторинга поверхностных вод // Еколопя довктля та безпека жип^яльносл (Укр.).- 2005.- №3.-С.73-78.
5. Пряхин С.И. Мониторинг состояния водных объектов и экологические аспекты водопользования северной части Доно-Медведицкой гряды // Поволжский экол. вестник.- 2004.- № 10.- С. 96-103.
6. Савченко Г.А., Ронкин В.И. Экосистемный подход к охране степей // Мат. международ. науч. конф. «Заповедные степи Украины. Состояние и перспективы их сохранности» (Аскания-Нова, 18-22 сент. 2007 г).- Армянск: ПП Андреев, 2007.- С.85-86.
7. Шевченко А.М., Артюхин А.Е. О необходимости комплексного подхода к мониторингу и использованию водних ресурсов рек // Акад. журн. Западной Сибири.- 2014.- Т.10, №2.- С.30-31.
PRENATAL DEVELOPMENT OF THE AUDITORY ORGAN IN PINNIPEDS
Solntseva Galina NIkolaevna
Doctor of biological sciences, akad. IAENM, A.N. Severtsov Institut of Problem Ecology and Evolution Russian Academy of
Sciences
ПРЕНАТАЛЬНОЕ РАЗВИТИЕ ОРГАНА СЛУХА У ЛАСТОНОГИХ
Солнцева Галина Николаевна, Доктор биологических наук, академик МНАЭП, Институт проблем экологии и эволюции им. А.Н. Северцова РАН
АННОТАЦИЯ
У представителей ластоногих в раннем эмбриогенезе слуховые и вестибулярные структуры отделяются друг от друга одновременно и обнаруживают сходные черты в строении. В первой половине раннего предплодного периода (ст. 13-15) как слуховые, так и вестибулярные структуры имеют общие черты в строении у большинства млекопитающих. Видовые особенности в структурной организации органов слуха и равновесия формируются во второй половине раннего предплодного периода (ст. 16-20) на сходных стадиях развития и в определенной последовательности. Эти черты строения обусловлены особенностями среды обитания и развиваются из гомологичных зачатков периферического отдела слуховой системы параллельно у филогенетически далеких и близких форм.
Keywords: outer, middle and inner ears; auditory ossicles; cochlea; prenatal development
Ключевые слова: наружное, среднее и внутреннее ухо; слуховые косточки; улитка; пренатальное развитие
ABSTRACT
In the representatives of pinnipeds, in the early embryogenesis, the auditory and vestibular structures are simultaneously separated from each other and reveal similar structural features. In the first half of the early prefetal period (stages 13-15), both the auditory and vestibular parts possess common structural features in most of mammals. Specific features in the structural organization of the hearing and equilibrium organs are formed in the second half of the early prefetal period (stages 16-20) at similar stages of development and in a certain sequence. These structural features are caused by peculiarities of habitat and develop in parallel from the homologous rudiments of the peripheral auditory system in phylogenetically distant and close forms.
INTRODUCTION
The study of marine mammals' auditory organ (cetaceans, pinnipeds), representing an absolutely specific direction of placental animals' evolution, was started more than three centuries ago. However, these works were carried out mainly at an anatomic level and had a fragmentary character [1, p. 131; 3, p. 102]. Besides, the research data on development of the cetaceans' and pinnipeds' auditory organ during an early prefetal period were completely absent, i.e. beginning with formation of an acoustic vesicle, or the stage of bud, up to the end of formation of basic anatomic structures of the auditory organ. On the basis of obtained results developmental patterns of the structures of the outer, middle and inner ears in representatives of mammals belonging to various ecological groups were established. In semi-aquatic marine mammals (pinnipeds), there is a strong connection with two habitats: water and air. It has caused an appearance of the adaptive features in the structural organization of the auditory organ for functioning in different in terms of physical properties habitats.
RESULTS and DISCUSSION
Bearded seal (Pinnipedia, Phocidae - Erignathus barbatus)
The outer ear of the bearded seal is represented by the external auditory meatus only. The auricle is reduced. The pair rudiment of a membranaceous labyrinth is marked at the stage of 2-3 pairs of somites [ 6, p. 315]. Further, at the stage of 6-9 pairs of somites, the auditory placode is formed [2, p. 370] and at the stage of 14-15 pairs of somites the auditory pit is formed, from which an acoustic vesicle develops at the stage of 20 pairs of somites (forelimb bud, stage 13) [5, p. 125]. At the same stage, in all investigated species, the bud of the auditory ossicles in the form of a mesenchymal condensation was found out. In studied species of mammals, a subdivision of the acoustic vesicle into superior and inferior parts is marked at the stages 14-15.
At the stages 14-15, subdivision of the inner ear into superior and inferior parts, i.e. into vestibule-ampullar and cochlear apparatuses is noticed. At the 16th stage, a cartilaginous part of the external auditory meatus starts to develop in the outer ear. It represents a short and direct tube. In the middle ear the tympanum is not expressed. At the 1617th stages, each bud of the auditory ossicles represents an independent formation; their basis is formed by immature precartilaginous tissue. Malleus has a small size. Compared to the malleus, the incus is big. Stapes is differentiated into cruses; bottom lamina is of an oval form. At the 16th stage, the cochlear apparatus looks like a canal. Its basis is formed by a high columnar epithelium, and the top part - by a low cuboidal epithelium, consisting of three rows of cells. The differentiation of the cellular elements of Corti's organ is completely absent. Nuclei of the cells are sharply basophilic, cellular borders are not marked. At this stage, the cochlear canal starts to twist spirally, forming the basal turn of the cochlea. At the 17th stage, the auditory meatus slightly
lengthens and, at the same time, the diameter and the form of its lumen partly change. The auditory meatus is surrounded by buds of four cartilaginous laminas formed by the mesenchymal tissue. In the middle ear, the process of formation of the tympanum, which represents a big and very narrow canal, starts. A basis of the auditory ossicles is formed by a mature precartilaginous tissue, the cells of which have distinct outlines. The auditory ossicles are separated by a perichondrium, consisting of small flat cells - chondroblasts that don't have distinct borders. Tympanic membrane is well-expressed. In the inner ear differentiation of the cochlea is observed in the basal and medial turns. On the axial cuts 3 cross-sections of the cochlear canal are visible. At the given stage, the cochlea is formed by 1.5 turns only. It is surrounded with an aural capsule, whose basis is formed by mature precartilaginous tissue. The formation of the modiolus, which is represented by the connective tissue elements, begins; numerous blood vessels are located between them. Cellular elements of Corti's organ are approximately at one stage of differentiation. Cells of the spiral ganglion are compactly assembled and are sharply basophilic. Nervous fibres are not marked. Exactly at the stage of the
At the 17th stage, the auditory meatus slightly lengthens and, at the same time, the diameter and the form of its lumen partly change. The auditory meatus is surrounded by buds of four cartilaginous laminas formed by the mesenchymal tissue. In the middle ear, the process of formation of the tympanum, which represents a big and very narrow canal, starts. A basis of the auditory ossicles is formed by a mature precartilaginous tissue, the cells of which have distinct outlines. The auditory ossicles are separated by a perichondrium, consisting of small flat cells - chondroblasts that don't have distinct borders. Tympanic membrane is well-expressed. In the inner ear differentiation of the cochlea is observed in the basal and medial turns. On the axial cuts 3
cross-sections of the cochlear canal are visible. At the given stage, the cochlea is formed by 1.5 turns only. It is surrounded with an aural capsule, whose basis is formed by mature precartilaginous tissue. The formation of the modiolus, which is represented by the connective tissue elements, begins; numerous blood vessels are located between them. Cellular elements of Corti's organ are approximately at one stage of differentiation. Cells of the spiral ganglion are compactly assembled and are sharply basophilic. Nervous fibres are not marked. Exactly at the stage of the cellular differentiation, the columnar epithelium of the cochlear canal's basis seems to move apart and two thickenings are formed, the bigger one is an axial thickening, the smaller - the lateral one. Nuclei in the cells of thickenings are located closer to the basis. They are large, with numerous nucleoli. Cellular borders are hardly marked, cytoplasm of the cells is light.
At the 18th stage of development, the auditory meatus is lengthened, and its cavity is filled with epithelial cells. In the middle ear the process of formation of tympanum continues. On the cross-section cuts it has the form of an irregular oval. The auditory ossicles are increased in size and differentiated into the elements constituting them. Incus is big and exceeds the size of malleus almost twice. In the area of incudomalleal joint the auditory ossicles are connected with each other almost at right angles that is also marked in definitive forms. Around chondrocytes the pericellular substance increases, a process of isogenous groups' formation takes place and the basic substance is formed. The chondroblasts of the perichondrium have distinct contours and are located more rarefiedly. In maturing of the auditory ossicles a heterochrony is found. Malleus and incus become more mature, their basis is formed by primary cartilaginous tissue, while the basis of the stapes is formed by mature
precartilaginous tissue. At the 19th stage, the auditory meatus is formed basically and filled incompletely with epithelial cells. In the middle ear, the process of tympanum formation and auditory ossicles cartilaginification continues. In tympanum an interposition of the auditory ossicles is the same as in definitive forms. Subsequent differentiation of the auditory ossicles into forming them elements continues. Malleus has a small head and a thickened handle. Incus is big relative to the malleus. Short and long processes of incus are well-visible. Stapes is differentiated into two thick cruses, forming a small inter-crura aperture. Around the bottom lamina the ring-shaped ligament is formed.
In the cochlear apparatus the process of the cartilaginification of an aural capsule has ended. Chondrocytes are of a roundish form with eccentrically located nucleus. In the intercellular substance differentiation of the collagen fibers takes place. The cells of Corti's organ are located rarefiedly, their nuclei are less basophilic. The process of cellular differentiation starts. The Reissner's and basilar membranes are formed, the last of which is located under the cells of axial and lateral thickenings.
In an embryo at the 20th stage of development, the auditory meatus is considerably lengthened, widened and bent. Throughout its whole length a diameter and a form of its lumen change. The basic process of its formation In an embryo at the 20-21st stages of development, a formation of the tympanic and vestibular scalae starts in the inner ear. The process of formation of the tectorial membrane has ended. The formation of a spiral incisure, spiral limb and a vascular stria continues. The tunnel is completely formed. The basic stage of a cellular differentiation of the receptor elements of Corti's organ has ended. The formation of the supporting cells of Corti's organ continues (Figure 1).
Fig. 1. Histotopography of the auditory organ in dorsoventral section of a prefetus's head of Erignathus barbatu s. Labels of all Figures (1-3): eam-external auditory meatus; ct- tympanum; m- malleus; i- incus; s- stapes; ms- m.stapedius; mtt- m. tensor tympani; och- os cochlearis; ch - cochlea;; vs - venous sinus; cb- cerebrum; at - auditory tube; sc -semicircular canal; sk -sacculus; ut - utriculus;; A - apical turn of the cochlea; M - middle turn; B - basal turn; n.ch -n. cochlearis;
n.v - n. vestibularis; 8n - n. acousticus.
Steller sea lion (Pinnipedia, Otariidae - Eumetopias jubatus)
The structure of the outer ear of a Steller sea lion includes an auricle and an external auditory meatus. In semi-aquatic species, as against terrestrial mammals, the auricle adopts new structural features. In a Steller sea lion, the auricle looks like a thick dermatoid fold, twirled in a cone, the top of which is caudally inverted. The same structure of the auricle is marked in the representative of marine mammals from the Carnivora order - a sea otter (Enhydra lutris).
At the 16th stage of development in a Steller sea lion, as well as in other mammals possessing an auricle, the first branchial cleft, widening gradually, forms a deepening, at the edge of which small protuberances start to develop, which, at the 17th stage of a normal development, merge and form a uniform mesenchymal bud of an auricle. The cartilaginous part of an external auditory meatus starts to form out from lateral walls of the first branchial cleft at the 16th stage of development. The osseous part of the auditory meatus in a Steller sea lion, as in other immature-born species (pinnipeds, cetaceans, ungulates), finishes its formation by the moment of birth.
By the beginning of the 19th stage of development, the auricle of a Steller sea lion acquires more distinct contours. The auditory meatus is lengthened. By the end of the 19th stage, the lateral part of the auditory meatus is filled with epithelial cells, which close the lumen of the auditory meatus completely by the 20-21st stages of development. In a Steller sea lion, the resorption of epithelial cells of the auditory meatus occurs by the moment of birth, as it is in other mature-born mammals. The formation of the species-specific features of the outer ear is marked at the 19th stage, as well as in majority of species. The middle ear is an additional organ of a labyrinth and is laid by a protrusion of the first pharyngeal recess, the endoderm of which will be transformed into a common tube-tympanic protrusion. All elements of the middle ear develop from mesenchyme. The bud of the auditory ossicles in a Steller sea lion, as well as in other mammals, appears at the 13th stage of development as a mesenchymal condensation. In this bud at the 16th stage, contours of the auditory ossicles appear. At the 17th stage, all buds of the auditory ossicles are represented by independent formations, their bases are composed by immature precartilaginous tissue. Tympanicum is formed at the 16th stage as a narrow canal located below the buds of the auditory ossicles. At the 19th stage, the tympanum's turning around the sagittal and frontal axes of a body of prefetus occurs. The formation of the structural elements of the auditory ossicles is marked at the 18th stage. The auditory ossicles are increased in size and are plunged in depth of the tympanicum. In majority of mammals cartilaginification of the auditory ossicles starts in the center of each bud of the auditory ossicles and spreads gradually to the periphery. In a Steller sea lion, as well as in other pinnipeds, maturation of the auditory ossicles occurs non-simultaneously. The malleus matures first of all, then a body of the incus, while lenticular arm of the incus, as well as the stapes, are formed by a mature precartilaginous tissue. However, in prefetuses of the majority of species, by the 20th stage, replacement of the mature precartilaginous tissue by an embryonic cartilage is finished completely. Formation of the features, linked to interposition of the auditory ossicles relative to each other, is marked at the end of the 16th and the beginning of the 17th
stages of development. At these stages, the auditory ossicles turn around the sagittal and frontal axes of the animal's body. The tympanic membrane is formed in an area of contact of pharyngeal recess's entoderm and ectoderm of the first branchial cleft. Its bud appears at the 16th stage; at the 17th stage, a Steller sea lion's tympanic membrane, as well as in majority of species, is thick and friable. Significant thinning of the tympanic membrane is marked by the end of the 16th and the beginning of the 17th stage of development. At the same stage, the tympanic membrane acquires a three-layer structure and is located almost horizontally on the lateral wall, forming one of the tympanic bone sides. The venous sinuses' development in a Steller sea lion, as well as in other representatives of pinnipeds, is marked at the 20th stage, i.e. during the replacement of cartilaginous tissue by osseous tissue in integumentary bones of a cranium. The process of ossification of the auditory ossicles starts during the stages 21st-22nd of development.
As in other mammals, the pair rudiment of a membranaceous labyrinth is marked at the stage of 2-3 pairs of somites. At the stage of 6-9 pairs of somites, the bud of the membranaceous labyrinth represents an auditory placode. Further, at the stage of 14-15 pairs of somites, an auditory pit is formed, from which at the stage of 20 pairs of somites (13th stage of development, the stage of a forelimb bud), an auditory vesicle develops, which passes into the endolymphatic duct without clear borders. In a Steller sea lion, as well as in most of mammals, at the 15th stage, subdivision of the acoustic vesicle into superior and inferior parts occurs. At the 16th stage of development, a cochlear canal starts to twist spirally, forming a lower, or basal, turn of the cochlea. At the 17th stage, a medial turn of the cochlea is formed, and anatomic formation of the cochlea is completed with the formation of an apical turn at the 18th stage of development. The cochlea is formed by 2.5 turns. At the same stage, cartilaginification of the aural capsule starts. Structures of the cochlear canal and cellular elements of Corti's organ are approximately at the same stage of development in all cochlea's turns. At the subsequent stages, the size of the cochlea increases.
At the 19th stage, a formation of an axis, or modiolus, of the cochlea, consisting of a connective tissue, as well as an anatomic formation of the cochlear canal's elements and a differentiation of cells of Corti's organ begins (Figure 2.).
The cuboidal epithelium's cells flatten; a loosening of connective tissue adjacent to this epithelium also occurs. At these locations, a formation of tympanic and vestibular scalae starts. The differentiation of the cells of Corti's organ begins from the basal turn of the cochlea and is spread gradually onto the turns located above. As a result, in all turns of the cochlea a different degree of an anatomic and cellular differentiation of the cochlear canal's elements is marked. The cochlear and vestibular branches of the auditory nerve are well-developed.
At the subsequent stages, the size of the cochlea increases and cellular differentiation of Corti's organ continues, which in a Steller sea lion, as well as in other mature-born species, is completed by the moment of birth. As it is in terrestrial species, Reissner's membrane is formed the first out of all structures of the cochlear canal, and a vascular stria is the latest to form
Walrus (Pinnipedia, O7dobenidae - Odobenus rosmarus divergens)
In an embryo at the 17th stage, the auditory meatus slowly plunge into the forming tympanum. The form of the
is lengthened, and the form and diameter of its lumen change auditory ossicles already corresponds to the one they will
in its different parts. The buds of the auditory ossicles, in have during definitive period. The basis of the auditory
which chain their juncture borders are clearly discerned, ossicles is formed by a mesenchymal tissue.
Fig. 2. Histotopography of the peripheral auditory system in dorsoventral sections of Eumetopias jubatus prefetus's head,
stages 18-19. Labels as in Figure 1.
At the 16th stage, in the inner ear around the cochlear canal, the process of formation of an aural capsule starts, the basis of which is formed by a mesenchyme. At the end of this stage, the process of transformation of mesenchyme into the
At the 17th stage, the medial turn, and at the 18th stage, the apical turn are formed. The basic process of the cochlea's formation has ended. Similar to other species, the development of the basal turn outstrips the development of the following turn, which is located above. According to its size, the basal turn differs insignificantly from the apical turn. The elements of Corti's organ are at approximately identical stage of cellular differentiation. The formation of the basilar and Reissner's membranes begins; these membranes, opposite to other details of the cochlea, start to develop the first.
At the 18th stage, in development of the auditory meatus, significant changes are not marked. However, in the lateral part of the auditory meatus, the epithelium's cells, which gradually fill up this part of the auditory meatus, are found and by the 19th stage they fill up its lumen completely.
In the middle ear an increase of the tympanum and the auditory ossicles, which are formed by a mature precartilaginous tissue takes place. However, contrary to the previous stage, the auditory ossicles undergo the process of morphological differentiation into the elements forming them. In the ear muscles, their differentiation continues. They are represented by long and wide muscular bundles.
In the inner ear, the cochlear canal forms 2.5 turns. On the axial cuts of the cochlea, four cross-sections of the cochlear canal are marked. On the section through the basal turn of the cochlea two protuberances, which are formed by
mature precartilaginous tissue starts, the cells of which acquire more distinct forms. The cochlear canal twists spirally, forming the basal turn.
a multi-row epithelium, can be seen. Between the protuberances a small deepening is located, from which the tunnel will be formed further. The aural capsule is formed by a mesenchyme, and transformation process of mesenchyme into mature precartilaginous tissue begins from the vestibular apparatus. At the given stage, the cellular elements of Corti's organ are involved in the process of morphological differentiation. Cells are located more rarefiedly. Cells' nuclei are large, have an oval form and numerous nucleoli. However, the typical patchiness in the arrangement of the outer hair cells is completely absent.
At the 19th stage, a size of the auditory meatus increases. The size of the auditory ossicles and tympanum in comparison with the previous stage is increased insignificantly. The tympanic muscle of the middle ear is long and wide, it lies deeply in the bone canal which separates the cochlear apparatus from the vestibular one. The stapedius muscle is short and wide. The differentiation of the middle ear's muscles continues. The auditory ossicles are differentiated into the elements forming them. The basis of the auditory ossicles is formed by a mature precartilaginous tissue. The interposition of the auditory ossicles in tympanum is the same as in definitive forms. According to its formation, the inner ear practically does not differ from the previous stage. Modiolus is at the initial stage of morphological differentiation. The differentiation of the cochlear canal's elements and the cells of Corti's organ is marked. The tympanic and vestibular scalae are formed (Figure 3).
Fig. 3. Histotopography of the peripheral auditory system in dorsoventral sections of Odobenus rosmarus divergens
prefetus's head, stages 18-19. Labels as in Figure 1.
At the 20th stage of an embryo development, the auditory meatus becomes longer, and the form of its lumen differs considerably in the distal and proximal parts. The cartilaginous part of the auditory meatus is filled completely with epithelial cells. The size of tympanum and the auditory ossicles is increased. The basis of the auditory ossicles is formed by a mature precartilaginous tissue with distinct cellular borders. At the given stage, the process of cartilaginification of the auditory ossicles begins, which, initially, covers their periphery and then is spread gradually to the center. Around the chondrocytes of the embryonic hyaline cartilage, the pericellular substance is located. Cells' nuclei are large; they are surrounded by a thin layer of cytoplasm and are located at some distance from each other. The auditory ossicles are surrounded by a perichondrium, consisting of small flat cells -chondroblasts, without distinct borders. Due to the perichondrium, the borders in the junction of the auditory ossicles are marked precisely. Tympanum formation and formation of tympanic membrane, which is thinned, continues. In the wall surrounding tympanum, the first centers of ossification have appeared.
In the inner ear the cochlear canal forms 2.5 turns like in adult forms. On the axial cuts of the cochlea, five cross-sections of the cochlear canal are visible. The process of cartilaginification of the aural capsule has completely finished. There is a differentiation of the collagen fibres in the intercellular substance of the embryonic hyaline cartilage. The morphological differentiation of cells of Corti's organ's continues. The location of cells is more ordered. Nuclei of the cells have a roundish and an oval forms. Below the forming outer hair cells, the cells with large nuclei are located. These are future Deuter's cells. Below them, the cells with pyknotic nuclei and a light cytoplasm are located. Under these epithelial cells the
basilar membrane is located. The future Hensen's and Claudius' cells are represented in the form of the cuboidal epithelium located in 1-2 rows.
In the cochlear canal differentiation of a spiral limb, a vascular stria and a spiral incisure continues. The spiral limb is formed by the cells of an oblong form. The vascular stria is formed by an undifferentiated epithelium, which cells have transparent nuclei of an oval and a roundish form. Nuclei contain one centrally located nucleolus. The outlines of cells are hardly visible. The basilar membrane, on which the cells of Corti's organ are located, is made by a forming connective tissue. The cuboidal epithelium of the Reissner's membrane consists of light and dark cells. In a spiral labium, in the place of the future spiral incisure, a multi-row layer of the high columnar epithelium is located. Nuclei of these cells are of a roundish-oval form and are transparent. Cellular borders are weakly marked. The tunnel is not formed yet. However, the bases of the supporting cells have already diverged. Thus, the internal cells-columns are located vertically, and the external cells-columns form a corresponding angle for the tunnel. The cochlear and vestibular branches of the auditory nerve are well-expressed. The neurons of the spiral ganglion are increased in size, are located at a small distance from each other and have distinct borders. The modiolus is penetrated by the dendrites of the spiral ganglion and has a more compact basis.
At the 21st - 22nd stages of development, the formation of the outer and middle ear has basically ended. The structures of the middle ear continue to increase in size. The number of the ossification's sites in tympanic and periotic bones has considerably increased. The auditory ossicles are formed by an embryonic hyaline cartilage. The head of the malleus is small; its handle is short and thick, what is not typical for terrestrial forms. The widened part of the malleus's
handle is fastened throughout its length to the forming connective-tissue tympanic membrane of a roundish form. In comparison to the malleus, the incus is large and heavy. Its size exceeds those of the malleus almost twice. The stapes is differentiated into two cruses and the footplate of a roundish form, around which a ring-shaped ligament is formed. The compact cruses form a small inter-crura space. The interposition of the auditory ossicles in tympanum is the same as in adult forms. The articular surface of the malleus is connected almost at right angles with the articular surface of the incus. Ear muscles are completely formed and are represented as long muscular bundles.
In the inner ear the aural capsule is formed by the embryonic hyaline cartilage, in which there is an increase of the intercellular substance and the capsules of the cartilaginous cells are clearly prominent. The process of formation of the isogenic groups of chondrocytes continues. The cochlear canal forms 2.5 turns and is located in the depth of periotic bone. The differentiation of the rostral and the paddle-shaped processes of the cells supporting Corti's organ began. The supporting cells have an oblong form with a nucleus located in the basal part of a cell.
Specific features in the structural organization of the hearing and equilibrium organs are formed in the second half of the early prefetal period (stages 16-20) at similar stages of development and in a certain sequence. These structural features are caused by peculiarities of habitat and develop in parallel from the homologous rudiments of the peripheral auditory system in phylogenetically distant and close forms [4, c. 110].
One of the aspects of comparative embryological study of the peripheral auditory system's formation in cetaceans and pinnipeds is the determining of their phylogeny.
The monophyletic hypothesis of the pinnipeds' origin is advanced on the basis of ecological-climatological research, biochemical research, the comparative analysis of karyotypes and the comparative embryological study of the formination of the external adaptive traites in phocids and otariids in the prenatal period.
The hypothesis of the polyphyletic origin was advanced after the discovery of serious morphological differences among Otariidae, Phocidae and Odobenidae and in view of the peculiarities of the geography of their natural habitats.
Our comparative morphological research and also the comparative study of the peripheral auditory system's development have revealed the basic distinctions of its structure between the representatives of two suborders of cetaceans,
as well as inside the order of pinnipeds between Otariidae on the one hand, and Phocidae, Odobenidae on the other hand. Our results might seem to testify to a greater extent in favour of the diphyletic hypothesis, as opposed to the monophyletic origin of the mammals.
However, the study of the peripheral auditory system's development has shown that in Mysticeti and Odon-toceti at similar stages of development in the early prefetal period the tympanic membranes reveal similarity in their structure, whereas in the fetal period they acquire species-specific traits.
Among pinnipeds the greatest similarity with the terrestrial forms in the structure of the peripheral auditory system is revealed in Otariidae, while Phocidae and Odobenidae represent evolutionary more advanced groups of mammals, whose auditory organ is to a greater extent adapted for functioning in an aquatic habitat.
During the investigation of the development of the peripheral auditory system the similarity between Otariidae and some representatives of Phocidae (Pusa hispida) was revealed that becomes apparent in the formation of auricle, which in Pusa hispida does not develop in the fetal period and in adult forms is absent.
On the basis of the data obtained, it is possible to assume that the most ancient group among pinnipeds is Otariidae, from which Odobenidae and Phocidae have descended further. This can also serve as evidence for the hypothesis of monophyletic origin of pinnipeds, which has been confirmed by immunological data and comparative karyotype analysis.
Literature Cited
1. Fleischer G. Studien am Skelett des Gehororgans der Saugetiere, einschliesslich des Menschen// Sau-getierk. Mitt -1973.- 21( H. 2 - 3) - p. 131 - 239.
2. Kappers A. Kopfplacoden bei Wirbeltieren// Ergebn. Anat. und Entwicklungsgeshichte - 1941. - № 33.-p.370.
3. Ramprashad F. Aquatic adaptations in the ear of the harp seal. Pagophilus groenlandicus (Erxleben, 1777)//. Rapp. et proc.-verb. reun. Cons, intern, ex-plor. mer. - 1975.- № 169- p. 102 -111.
4. Solntseva G.N. The Auditory Organ of marine Mammals. M.: Nauka, 2006. 203 p.
5. Titova L.K.. Development of receptor structures in the inner ear of vertebrates. L.: Nauka, 1968. 217 p.
6. Wilson J.T. 1914. Observations upon young human embryos// J. Anat. Physiol. - 1914. - № 48 - p. 315.
РЕТРОСПЕКТИВНЫЙ АНАЛИЗ ИССЛЕДОВАНИЙ ОСОБЕННОСТЕЙ ГНЕЗДОВОЙ
БИОЛОГИИ ЛАСТОЧЕК
Сугробова Наталия Юрьевна
кандидат биол. наук, доцент, Пермский государственный национальный исследовательский университет,
Соликамский государственный педагогический институт (филиал), г.Соликамск
RETROSPECTIVE ANALYSIS OF THE RESEACHERS OF THE SPECIAL FOR A NEST BIOLOGY OF THE SWALLOWS Sugrobova Nataliya, Candidate of Biology, Perm State National Research University, Solikamsk State Teacher Training Institute (branch), Solikamsk
