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Clasper
In biology, a clasper is a male anatomical structure found in some groups of animals, used in mating. Male cartilaginous fish have claspers formed from the posterior portion of their pelvic fin which serve to channel semen into the female's cloaca during mating. The act of mating in some fish including sharks usually includes one of the claspers raised to allow water into the siphon through a specific orifice. The clasper is then inserted into the cloaca, where it opens like an umbrella to anchor its position. The siphon then begins to contract, expelling water and sperm. The claspers of many shark species have spines or hooks, which may hold them in place during copulation. Many male holocephalans, including living chimaeras, have cephalic claspers (tenacula) on their heads, which are thought to aid in holding the female during mating. In entomology Entomology (from Ancient Greek ἔντομον (''éntomon''), meaning "insect", and -logy from λόγος (''lógos'') ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Holocephali
Holocephali (Sometimes spelled Holocephala; Romanization of Greek, Greek for "complete head" in reference to the fusion of Palatoquadrate, upper jaw with the rest of the skull) is a Subclass (biology), subclass of Chondrichthyes, cartilaginous fish. While the only living holocephalans are three families within a single Order (biology), order which together are commonly known as chimaeras, the group includes many extinct orders and was far more diverse during the Paleozoic and Mesozoic Era (geology), eras. The earliest known fossils of holocephalans date to the Middle Devonian period, and the group likely reached its peak diversity during the following Carboniferous period. Molecular clock studies suggest that the subclass diverged from its closest relatives, Elasmobranchii, elasmobranchs such as sharks and Batomorphi, rays, during the Early Devonian or Silurian period. Extinct holocephalans are typically divided into a number of orders, although the interrelationships of these gro ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Shark
Sharks are a group of elasmobranch cartilaginous fish characterized by a ribless endoskeleton, dermal denticles, five to seven gill slits on each side, and pectoral fins that are not fused to the head. Modern sharks are classified within the Division (taxonomy), division Selachii and are the sister group to the Batoidea, Batomorphi (Batoidea, rays and skate (fish), skates). Some sources extend the term "shark" as an informal category including Extinction, extinct members of Chondrichthyes (cartilaginous fish) with a shark-like morphology, such as hybodonts. Shark-like chondrichthyans such as ''Cladoselache'' and ''Doliodus'' first appeared in the Devonian Period (419–359 million years), though some fossilized chondrichthyan-like scales are as old as the Ordovician, Late Ordovician (458–444 million years ago). The earliest confirmed modern sharks (Selachii) are known from the Early Jurassic around , with the oldest known member being ''Agaleus'', though records of true shar ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Lepidoptera Genitalia
The study of the genitalia of Lepidoptera is important for Lepidoptera taxonomy in addition to development, anatomy and natural history. The genitalia are complex and provide the basis for species discrimination in most families and also in family identification. The genitalia are attached onto the tenth or most distal segment of the abdomen. Lepidoptera have some of the most complex genital structures in the insect groups with a wide variety of complex spines, setae, scales and tufts in males, claspers of different shapes and different modifications of the ductus bursae in females. The arrangement of genitalia is important in the courtship and mating as they prevent cross-specific mating and hybridisation. The uniqueness of genitalia of a species led to the use of the morphological study of genitalia as one of the most important keys in taxonomic identification of taxa below family level. With the advent of DNA analysis, the study of genitalia has now become just one of the tec ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Harpagofututor Volsellorhinus
''Harpagofututor'' is an extinct genus of eel-like cartilaginous fish from the Early Carboniferous ( Mississippian). It is primarily known from complete specimens discovered in the Bear Gulch Limestone of Montana, as well as an isolated tooth from Whitrope, Scotland. Discovery and taxonomy ''Harpagofututor'' was first described in 1982, from several complete specimens discovered in the Bear Gulch Limestone of Montana by Adelphi University palaeontologist Richard Lund.Lund, Richard. "Harpagofututor volsellorhinus New Genus and Species (Chondrichthyes, Chondrenchelyiformes) from the Namurian Bear Gulch Limestone, Chondrenchelys problematica Traquair (Visean), and Their Sexual Dimorphism," ''Journal of Paleontology'', Vol. 56, No. 4, July 1982, pp. 938-958. There is only one named species, ''H. volsellorhinus'', which was described by Lund in 1982. A single specimen of indeterminate species is also known from a single tooth plate discovered in Whitrope, Scotland. The genus is pla ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Chimaera
Chimaeras are Chondrichthyes, cartilaginous fish in the order (biology), order Chimaeriformes (), known informally as ghost sharks, rat fish (not to be confused with rattails), spookfish, or rabbit fish; the last two names are also applied to Barreleye, Opisthoproctidae and Rabbitfish, Siganidae, respectively. At one time a "diverse and abundant" group (based on the fossil record), their closest living relatives are sharks and ray (fish), rays, though their last common ancestor with them lived nearly 400 million years ago. Living species (aside from plough-nose chimaeras) are largely confined to deep water. Anatomy Chimaeras are soft-bodied, shark-like fish with bulky heads and long, tapered tails; measured from the tail, they can grow up to in length. Like other members of the class Chondrichthyes, chimaera skeletons are entirely cartilaginous, or composed of cartilage. Males use forehead denticles to grasp a female by a fin during copulation. The Branchial arch, gill arche ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Fish Anatomy
Fish anatomy is the study of the form or Morphology (biology), morphology of fish. It can be contrasted with fish physiology, which is the study of how the component parts of fish function together in the living fish. In practice, fish anatomy and fish physiology complement each other, the former dealing with the structure of a fish, its organs or component parts and how they are put together, such as might be observed on the dissecting table or under the microscope, and the latter dealing with how those components function together in living fish. The anatomy of fish is often shaped by the physical characteristics of water, the medium in which fish live. Water is much density, denser than air, holds a relatively small amount of dissolved oxygen, and absorbs more light than air does. The body of a fish is divided into a head, trunk and tail, although the divisions between the three are not always externally visible. The skeleton, which forms the support structure inside the fish ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cartilaginous Fish
Chondrichthyes (; ) is a class of jawed fish that contains the cartilaginous fish or chondrichthyans, which all have skeletons primarily composed of cartilage. They can be contrasted with the Osteichthyes or ''bony fish'', which have skeletons primarily composed of bone tissue. Chondrichthyes are aquatic vertebrates with paired fins, paired nares, placoid scales, conus arteriosus in the heart, and a lack of opercula and swim bladders. Within the infraphylum Gnathostomata, cartilaginous fishes are distinct from all other jawed vertebrates. The class is divided into two subclasses: Elasmobranchii (sharks, rays, skates and sawfish) and Holocephali ( chimaeras, sometimes called ghost sharks, which are sometimes separated into their own class). Extant chondrichthyans range in size from the finless sleeper ray to the over whale shark. Anatomy Skeleton The skeleton is cartilaginous. The notochord is gradually replaced by a vertebral column during development, e ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Wobbegong Claspers
Wobbegong is the common name given to the 12 species of carpet sharks in the family Orectolobidae. They are found in shallow temperate and tropical waters of the western Pacific Ocean and eastern Indian Ocean, chiefly around Australia and Indonesia, although one species (the Japanese wobbegong, ''Orectolobus japonicus'') occurs as far north as Japan. The word ''wobbegong'' is believed to come from an Australian Aboriginal language, meaning "shaggy beard", referring to the growths around the mouth of the shark of the western Pacific. Description Wobbegongs are bottom-dwelling sharks, spending much of their time resting on the sea floor. Most species have a maximum length of , but the largest, the spotted wobbegong, ''Orectolobus maculatus'', and banded wobbegong, ''O. halei'', reach about in length. Wobbegongs are well camouflaged with a symmetrical pattern of bold markings which resembles a carpet. Because of this striking pattern, wobbegongs and their close relatives are ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sexual Coercion Among Animals
Sexual coercion among animals is the use of violence, threats, harassment, and other tactics to help them forcefully copulate.Smuts, Barbara B"Male Aggression and Sexual Coercion of Females in Nonhuman Primates and Other Mammals: Evidence and Theoretical Implications" ''Advances in the Study of Behavior'' 22 (1993) Such behavior has been compared to sexual assault, including rape, among humans. In nature, males and females usually differ in reproductive fitness optima.Han, C. S. & Jablonski, P. G"Female genitalia concealment promotes intimate male courtship in a water strider" ''PLoS ONE'' 4, e5793 (2009). Males generally prefer to maximize their number of offspring, and therefore their number of mates; females, on the other hand, tend to care more for their offspring and have fewer mates.Gage, M. J. G., Parker, G. a, Nylin, S. & Wiklund, C"Sexual selection and speciation in mammals, butterflies and spiders" ''Proceedings: Biological Sciences'' 269, 2309–16 (2002). Because of ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Copulation (zoology)
In zoology, copulation is animal sexual behavior in which a male introduces sperm into the female's body, especially directly into her reproductive tract. This is an aspect of mating. Many aquatic animals use external fertilization, whereas internal fertilization may have developed from a need to maintain gametes in a liquid medium in the Late Ordovician epoch. Internal fertilization with many vertebrates (such as all reptiles, some fish, and most birds) occurs via cloacal copulation, known as cloacal kiss (see also hemipenis), while most mammals copulate vaginally, and many basal vertebrates reproduce sexually with external fertilization. In spiders and insects Spiders are often confused with insects, but they are not insects; instead, they are arachnids. Spiders have separate male and female sexes. Before mating and copulation, the male spider spins a small web and ejaculates on to it. He then stores the sperm in reservoirs on his large pedipalps, from which he tran ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Entomology
Entomology (from Ancient Greek ἔντομον (''éntomon''), meaning "insect", and -logy from λόγος (''lógos''), meaning "study") is the branch of zoology that focuses on insects. Those who study entomology are known as entomologists. In the past, the term ''insect'' was less specific, and historically the definition of entomology would also include the study of animals in other arthropod groups, such as arachnids, myriapods, and crustaceans. The field is also referred to as insectology in American English, while in British English insectology implies the study of the relationships between insects and humans. Over 1.3million insect species have been described by entomology. History Entomology is rooted in nearly all human cultures from prehistoric times, primarily in the context of agriculture (especially biological control and beekeeping). The natural Roman philosopher Pliny the Elder (23–79 CE) wrote a book on the kinds of insects, while the scientist Grammarians ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Body Orifice
A body orifice is any opening in the body of an animal. External In a typical mammalian body such as the human body, the external body orifices are: * The nostrils, for breathing and the associated sense of smell * The mouth, for eating, drinking, breathing, and vocalizations such as speech * The ear canals, for the sense of hearing * The nasolacrimal ducts, to carry tears from the lacrimal sac into the nasal cavity * The anus, for defecation * The urinary meatus, for urination in males and females and ejaculation in males * In females, the vagina, for menstruation, copulation and birth * The nipple orifices Other animals may have some other body orifices: *cloaca, in birds, reptiles, amphibians, and a few mammals, such as monotremes. *siphon in mollusks, arthropods, and some other animals Internal Internal orifices include the orifices of the outflow tracts of the heart, between the heart valves. See also *Internal urethral orifice *Mucosa * Mucocutaneous boundary *Meatus ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
