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Sperm Polymorphism
Sperm heteromorphism is the simultaneous production of two or more distinguishable types of sperm by a single male. The sperm types might differ in size, shape and/or chromosome complement. Sperm heteromorphism is also called sperm polymorphism or sperm dimorphism (for species with two sperm types). Typically, only one sperm type is capable of fertilizing eggs. Fertile types have been called "eusperm" or "eupyrene sperm" and infertile types "parasperm" or "apyrene sperm". One interpretation of sperm polymorphism is the "kamikaze sperm" hypothesis (Baker and Bellis, 1988), which has been widely discredited in humans. The kamikaze sperm hypothesis states that the polymorphism of sperm is due to a subdivision of sperm into different functional groups. There are those that defend the egg from fertilization by other male sperm, and those that fertilize the egg. However, there is no evidence that the polymorphism of human sperm is for the purpose of antagonizing rival sperm. Distribution ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sperm
Sperm is the male reproductive cell, or gamete, in anisogamous forms of sexual reproduction (forms in which there is a larger, female reproductive cell and a smaller, male one). Animals produce motile sperm with a tail known as a flagellum, which are known as spermatozoa, while some red algae and fungi produce non-motile sperm cells, known as spermatia. Flowering plants contain non-motile sperm inside pollen, while some more basal plants like ferns and some gymnosperms have motile sperm. Sperm cells form during the process known as spermatogenesis, which in amniotes ( reptiles and mammals) takes place in the seminiferous tubules of the testes. This process involves the production of several successive sperm cell precursors, starting with spermatogonia, which differentiate into spermatocytes. The spermatocytes then undergo meiosis, reducing their chromosome number by half, which produces spermatids. The spermatids then mature and, in animals, construct a tail, or flagellum, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Carabidae
Ground beetles are a large, cosmopolitan family of beetles, the Carabidae, with more than 40,000 species worldwide, around 2,000 of which are found in North America and 2,700 in Europe. As of 2015, it is one of the 10 most species-rich animal families. They belong to the Adephaga. Members of the family are primarily carnivorous, but some members are phytophagous or omnivorous. Description and ecology Although their body shapes and coloring vary somewhat, most are shiny black or metallic and have ridged wing covers (elytra). The elytra are fused in some species, particularly the large Carabinae, rendering the beetles unable to fly. The species ''Mormolyce phyllodes'' is known as violin beetle due to their peculiarly shaped elytra. All carabids except the quite primitive flanged bombardier beetles (Paussinae) have a groove on their fore leg tibiae bearing a comb of hairs used for cleaning their antennae. Defensive secretions Typical for the ancient beetle suborder Adephaga to ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sperm Competition
Sperm competition is the competitive process between spermatozoa of two or more different males to fertilize the same egg during sexual reproduction. Competition can occur when females have multiple potential mating partners. Greater choice and variety of mates increases a female's chance to produce more viable offspring. However, multiple mates for a female means each individual male has decreased chances of producing offspring. Sperm competition is an evolutionary pressure on males, and has led to the development of adaptations to increase males' chance of reproductive success. Sperm competition results in a sexual conflict of interest between males and females. Males have evolved several defensive tactics including: mate-guarding, mating plugs, and releasing toxic seminal substances to reduce female re-mating tendencies to cope with sperm competition. Offensive tactics of sperm competition involve direct interference by one male on the reproductive success of another male, for ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sperm Competition
Sperm competition is the competitive process between spermatozoa of two or more different males to fertilize the same egg during sexual reproduction. Competition can occur when females have multiple potential mating partners. Greater choice and variety of mates increases a female's chance to produce more viable offspring. However, multiple mates for a female means each individual male has decreased chances of producing offspring. Sperm competition is an evolutionary pressure on males, and has led to the development of adaptations to increase males' chance of reproductive success. Sperm competition results in a sexual conflict of interest between males and females. Males have evolved several defensive tactics including: mate-guarding, mating plugs, and releasing toxic seminal substances to reduce female re-mating tendencies to cope with sperm competition. Offensive tactics of sperm competition involve direct interference by one male on the reproductive success of another male, for ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Fusitriton Oregonensis Parasperm
''Fusitriton'' is a genus of large predatory sea snails marine gastropod molluscs in the family Cymatiidae. Species Species within the genus ''Fusitroton'' include: * '' Fusitriton brasiliensis'' Cossignani & Cossignani, 2003 * '' Fusitriton galea'' Kuroda & Habe, 1961 * '' Fusitriton glassi'' Swinnen, 2019 * '' Fusitriton laudandus'' Finlay, 1926 * '' Fusitriton magellanicus'' (Röding, 1798) * '' Fusitriton oregonensis'' (Redfield, 1846) * '' Fusitriton retiolus'' (Hedley, 1914) * '' Fusitriton takedai'' Habe, 1979 ;Species brought into synonymy: * ''Fusitriton algoensis'' Tomlin, 1947: synonym of ''Fusitriton murrayi'' (E. A. Smith, 1891): synonym of '' Fusitriton magellanicus'' (Röding, 1798) (synonym) * ''Fusitriton antarcticus'' Powell, 1958: synonym of '' Antarctoneptunea aurora'' (Hedley, 1916) * ''Fusitriton aurora'' Hedley, 1916: synonym of '' Antarctoneptunea aurora'' (Hedley, 1916) (original combination) * ''Fusitriton futuristi'' Mestayer, 1927: synonym of '' Fusi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Capacitation
Capacitation is the penultimate step in the maturation of mammalian spermatozoa and is required to render them competent to fertilize an oocyte. This step is a biochemical event; the sperm move normally and look mature prior to capacitation. ''In vivo'', capacitation occurs after ejaculation, when the spermatozoa leave the vagina and enter the superior female reproductive tract. The uterus aids in the steps of capacitation by secreting sterol-binding albumin, lipoproteins, and proteolytic and glycosidasic enzymes such as heparin. For purposes of ''in vitro'' fertilization, capacitation occurs by incubating spermatozoa that have either undergone ejaculation or have been extracted from the epididymis and incubated in a defined medium for several hours. There are different techniques to perform the capacitation step: simple washing, migration (swim-up), density gradients, and filter. The objective is to isolate as many motile spermatozoa as possible and to eliminate non-motile or d ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sculpin
A sculpin is a type of fish that belongs to the superfamily Cottoidea in the order Scorpaeniformes.Kane, E. A. and T. E. Higham. (2012)Life in the flow lane: differences in pectoral fin morphology suggest transitions in station-holding demand across species of marine sculpin.''Zoology'' (Jena) 115(4), 223-32. As of 2006, this superfamily contains 7 families, 94 genera, and 387 species. Sculpins occur in many types of habitat, including ocean and freshwater zones. They live in rivers, submarine canyons, kelp forests, and shallow littoral habitat types, such as tidepools. Sculpins are benthic fish, dwelling on the bottoms of water bodies. Their pectoral fins are smooth on the upper edge and webbed with sharp rays along the lower edge, a modification that makes them specialized for gripping the substrate. This adaptation helps the fish anchor in fast-flowing water. The sculpin normally grows to about four inches long. Families and subfamilies Families include: * Jordaniidae Sta ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Lysosomes
A lysosome () is a membrane-bound organelle found in many animal cells. They are spherical vesicles that contain hydrolytic enzymes that can break down many kinds of biomolecules. A lysosome has a specific composition, of both its membrane proteins, and its lumenal proteins. The lumen's pH (~4.5–5.0) is optimal for the enzymes involved in hydrolysis, analogous to the activity of the stomach. Besides degradation of polymers, the lysosome is involved in various cell processes, including secretion, plasma membrane repair, apoptosis, cell signaling, and energy metabolism. Lysosomes act as the waste disposal system of the cell by digesting used materials in the cytoplasm, from both inside and outside the cell. Material from outside the cell is taken up through endocytosis, while material from the inside of the cell is digested through autophagy. The sizes of the organelles vary greatly—the larger ones can be more than 10 times the size of the smaller ones. They were discovered ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Gastropods
The gastropods (), commonly known as snails and slugs, belong to a large taxonomic class of invertebrates within the phylum Mollusca called Gastropoda (). This class comprises snails and slugs from saltwater, from freshwater, and from land. There are many thousands of species of sea snails and slugs, as well as freshwater snails, freshwater limpets, and land snails and slugs. The class Gastropoda contains a vast total of named species, second only to the insects in overall number. The fossil history of this class goes back to the Late Cambrian. , 721 families of gastropods are known, of which 245 are extinct and appear only in the fossil record, while 476 are currently extant with or without a fossil record. Gastropoda (previously known as univalves and sometimes spelled "Gasteropoda") are a major part of the phylum Mollusca, and are the most highly diversified class in the phylum, with 65,000 to 80,000 living snail and slug species. The anatomy, behavior, feeding, and reproduc ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Prosobranch
Prosobranchia was a large taxonomic subclass of sea snails, land snails and freshwater snails. This taxon of gastropods dates back to the 1920s. It has however been proven to be polyphyletic (consisting of more than one lineage of descent). Generally speaking in biology taxonomy is required to reflect phylogeny, in other words the classification of a group must reflect its evolutionary descent, as far as that is known, so the taxon Prosobranchia is no longer considered suitable to be used. One can still encounter this subclass used as if it is still valid in many texts and websites. Although Prosobranchia is no longer generally accepted as a taxon by people who study living Mollusca, still the term prosobranch is legitimately used as an anatomically descriptive adjective or noun, and the taxon Prosobranchia is still sometimes used by paleontologists. ''Prosobranch'' means ''gills in front'' (of the heart). In contrast ''opisthobranch'' means ''gills behind'' (and to the right of ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Male
Male (symbol: ♂) is the sex of an organism that produces the gamete (sex cell) known as sperm, which fuses with the larger female gamete, or ovum, in the process of fertilization. A male organism cannot reproduce sexually without access to at least one ovum from a female, but some organisms can reproduce both sexually and asexually. Most male mammals, including male humans, have a Y chromosome, which codes for the production of larger amounts of testosterone to develop male reproductive organs. Not all species share a common sex-determination system. In most animals, including humans, sex is determined genetically; however, species such as ''Cymothoa exigua'' change sex depending on the number of females present in the vicinity. In humans, the word ''male'' can also be used to refer to gender in the social sense of gender role or gender identity. Overview The existence of separate sexes has evolved independently at different times and in different lineages, an example ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
