Sperm Penetration and the Formation of a Fertilization Cone in the Common Carp Egg*

Kudo, Shigeharu

doi:10.1111/j.1440-169x.1980.00403.x

Cited by 71 publications

(56 citation statements)

References 24 publications

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“…According to Kudo (1980), the micropyle channel in Cyprinus carpio allows the access to several spermatozoa, suggesting that the agglomeration of supernumerary spermatozoa in the perivitelline space is required as an additional mechanism to prevent polyspermy. Ginsburg (1961) confirmed the agglutination of spermatozoa in the micropyle channel of Salmo trutta and reported that, by removing the perivitelline fluid, polyspermy was achieved in this species since it would prevent the accumulation of supernumerary spermatozoa.…”

Section: Discussionmentioning

confidence: 99%

Structural analysis of fertilization in the fish Brycon orbignyanus

Ganeco

Franceschini-Vicentini

Nakaghi

2009

Zygote

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SummaryIn the present work, we analyzed the structure of oocytes and fertilized eggs of the piracanjuba fish (Brycon orbignyanus) under light and scanning electron microscopy. After inducing spawning, samples were collected at the moment of oocyte extrusion, when oocytes and semen were mixed (time 0), as well as at 10, 20 and 30 s after mixing, every minute up to 10 min, and then at 15 and 20 min. The oocytes are spherical, translucent and greenish with a mean diameter of 1.3 ± 0.11 mm. During the extrusion, cytoplasmic movement was observed in eggs towards the micropyle, characterizing the animal pole. At the moment of fertilization, the cortical cytoplasm showed a higher concentration of cortical alveoli at the animal pole than at the vegetal pole. The cortical alveoli breakdown promoted the elevation of the chorion with a consequent increase in egg diameter (1.95 ± 0.08 mm). The penetration of the spermatozoon promotes the formation of a fertilization cone of spherical external structure, which obstructs the opening of the micropyle. This structure acts as a main mechanism to avoid polyspermy, intercepting the access of supernumerary spermatozoa. Such studies about the reproductive biology of fish are important to species survival and conservation programmes.

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Section: Discussionmentioning

confidence: 99%

Structural analysis of fertilization in the fish Brycon orbignyanus

Ganeco

Franceschini-Vicentini

Nakaghi

2009

Zygote

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“…In the carp and the rose bitterling, a fertilizing spermatozoonattaches first to the membraneof the microvilli at the SES just beneath a micropyle (9,15). Membrane fusion between sperm heads and egg microvilli has begun within 10 sec postinsemination (14).…”

Section: Discussionmentioning

confidence: 99%

“…The morphology of the SES just beneath the micropyle varies among different species of teleosts (2,6,8,9,10,15). In cyprinid fishes, the SES has many microvilli in a circle coinciding with the inside diameter of the micropylar aperture (6,10,15).…”

Section: Discussionmentioning

confidence: 99%

Electron Microscopic Observations on Sperm Penetration in Cytochalasin-treated Eggs of the Rose Bitterling.

Ohta

Yoshida

Kato

1998

Cell Struct. Funct.

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Key words: fish egg/cytochalasin B/spermentry site/fertilization/sperm penetration ABSTRACT. The effects of cytochalasin B (CB), which acts on micro filaments, on sperm penetration into eggs of a teleost fish were investigated ultrastructurally.Eggs from the rose bitterling, Rhodeus ocellatus ocellatus, were pre-treated in physiological saline containing CB and inseminated in water also containing CB. Microvilli at the sperm entry site (SES) under the micropyle disappeared or shortened in length following CB treatment. However, a spermatozoon attached to and fused with the SES of CB-treated eggs. The spermatozoon present in a swollen mass (SM) remained at the egg surface even after membranefusion and did not enter the cortex. It was unclear whether or not sperm movement from the cortex to the inner cytoplasm is CB-sensitive. The SMformed and plugged the micropyle. CB did not inhibit cortical alveolus breakdown. Based on the present experiments with fish eggs, it is concluded that CBinhibits sperm movementfrom the egg surface to the cortex, but not sperm attachment (binding), membrane fusion and SMformation during the process of sperm penetration.The spermatozoon of a teleost fish is devoid of acrosomal structures. On the other hand, the egg is enveloped by an egg membrane (chorion) which has a micropyle at the animal pole. The egg plasma membrane just beneath the micropyle, through which a spermatozoon penetrates, is exposed directly to the exterior. A fertilizing spermatozoon is therefore able to attach to the egg plasma membranewithout making a hole in the chorion. In eggs of the rose bitterling, attachment and subsequent fusion of a fertilizing spermatozoon with the egg plasma membraneresults in formation of a swollen mass (SM) containing the naked spermatozoon. The SMthereafter remains, plugging the micropyle, and serves to block the penetration of spermatozoa after the first (14, 15). Cytochalasin B (CB) acts on micro filament function by inhibiting actin polymerization. We previously investigated the effects of CB on SM formation (16) and found that SMformation was not inhibited by CBtreatment. These preliminary observations of CBtreated eggs showed that sperm penetration seemed to occur, but that penetration of the sperm flagellum was slow in contrast to that seen in non-treated eggs. However, superficial observations by scanning electron microscopy (SEM) cannot clarify the details of penetration. In manyanimals, sperm penetration into CBtreated eggs has been inhibited (3, 5, ll, 12, 17, 21).However, it is unclear which steps in the process of sperm penetration are CB-sensitive. The present report was conducted to investigate the CB-sensitive steps in the process of the sperm penetration of fish eggs, using scanning and transmission (TEM) electron microscopy, as well as fluorescence microscopy. MATERIALS AND METHODSAdult rose bitterlings (Rhodeus ocellatus ocellatus) were kept in aerated aquaria together with freshwater bivalves, Anodonta woodiana at 18-23°C (water temperature). During breeding seasons sp...

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“…These studies suggest that sperm entry into the micropyle is not random, at least in these fish. The morphology of sperm entry in fish eggs was reported first by Yamamoto (1952) in the flounder, followed by many others in various fishes using both light and electron microscopes (Brummett and Dumont., 1979;Kudo, 1980;Iwamatsu and Ohta, 1981;Yamamoto, 1981, 1987;Amanze and Iyengar, 1990;Iwamatsu et al, 1991;Yanagimachi et al, 1992;Iwamatsu et al, 1993).…”

Section: Introductionmentioning

confidence: 99%

The use of poly-L-lysine to facilitate examination of sperm entry into pelagic, non-adhesive fish eggs

Andoh

Matsubara²,

Harumi³

et al. 2008

Int. J. Dev. Biol.

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The fish egg is surrounded by a thick envelope called the chorion. The fertilizing spermatozoon enters the egg through a canal-like structure in the chorion, the micropyle. Examination of micropyle at fertilization is difficult if eggs are large and have no distinct landmarks surrounding the micropyle, or if they are positively buoyant in water. Eggs of many commercially important fishes (e.g., flounder, sea bream and eel) are buoyant in water or only slightly adhere to solid objects (e.g., sands, rock and water plants), which makes observation of spermatozoa at fertilization difficult. Here, we report that such eggs can be firmly attached to plastic and glass dishes that have been previously coated with poly-L-lysine. These adhering eggs can be fertilized and develop normally on the dishes. Observations of micropyles of three fish species, before and after sperm entry are presented.

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Sperm Penetration and the Formation of a Fertilization Cone in the Common Carp Egg*

Cited by 71 publications

References 24 publications

Structural analysis of fertilization in the fish Brycon orbignyanus

Structural analysis of fertilization in the fish Brycon orbignyanus

Electron Microscopic Observations on Sperm Penetration in Cytochalasin-treated Eggs of the Rose Bitterling.

The use of poly-L-lysine to facilitate examination of sperm entry into pelagic, non-adhesive fish eggs

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