The spinner shark is a species of requiem shark, in the family Carcharhinidae, named for the spinning leaps it makes as a part of its feeding strategy. This species occurs in tropical and warm temperate waters worldwide, except for in the eastern Pacific Ocean, it is found from coastal to offshore habitats to a depth of 100 m. The spinner shark resembles a larger version of the blacktip shark, with a slender body, long snout, black-marked fins; this species can be distinguished from the blacktip shark by the first dorsal fin, which has a different shape and is placed further back, by the black tip on the anal fin. It attains a maximum length of 3 m. Spinner sharks are swift and gregarious predators that feed on a wide variety of small bony fishes and cephalopods; when feeding on schools of forage fish, they speed vertically through the school while spinning on their axis, erupting from the water at the end. Like other members of its family, the spinner shark is viviparous, with females bearing litters of three to 20 young every other year.
The newborns are born in shallow nursery areas near the coast, are fast-growing. This species is not dangerous to humans, but may become belligerent when excited by food. Spinner sharks are valued by commercial fisheries across their range for their meat, liver oil and skin, they are esteemed as strong fighters by recreational fishers. The IUCN has assessed this species as near threatened worldwide and vulnerable off the Southeastern United States; the spinner shark was described as Carcharias brevipinna by Johannes Peter Müller and Friedrich Gustav Jakob Henle in their 1839 Systematische Beschreibung der Plagiostomen, based on the mounted skin of a 79-cm-long specimen collected off Java. This species was subsequently moved to the genera Aprion and Aprionodon before being placed within the genus Carcharhinus; the tooth shape and coloration of this species varies with age and between geographical regions, which caused much taxonomic confusion. Other common names include black-tipped shark, great blacktip shark, inkytail shark, large blacktip shark, long-nose grey shark, longnose grey whaler, smoothfang shark.
Based on similarities in morphology, tooth shape and behavior, the closest relatives of the spinner shark were believed to be the blacktip shark and the graceful shark. However, this interpretation was not supported by Gavin Naylor's 1992 allozyme analysis, which suggested that these similarities are the product of convergent evolution and that the closest relative of the spinner shark is the copper shark. In a 2007 ribosomal DNA study, the spinner shark was found to be the most genetically divergent of all the requiem shark species examined save for the tiger shark, being less related to other Carcharhinus species than the lemon shark; some uncertainty exists in the distribution data for the spinner shark due to confusion with the blacktip shark. In the Western Atlantic Ocean, it occurs from North Carolina to the northern Gulf of Mexico, including the Bahamas and Cuba, from southern Brazil to Argentina. In the Eastern Atlantic, it occurs from off North Africa to Namibia. In the Indian Ocean, it is found from South Africa and Madagascar, to the Red Sea and the Gulf of Aden, to India and nearby islands, to Java and Sumatra.
In the Pacific Ocean, it occurs off Japan, Vietnam and the Philippines. Parasitological evidence suggests that Indian Ocean spinner sharks have passed through the Suez Canal into the Mediterranean Sea, becoming Lessepsian migrants; the spinner shark has been reported from ocean surface to a depth of 100 m, though it prefers water less than 30 m deep, occupies all levels of the water column. This species may be found from coastal waters to well offshore, over continental and insular shelves. Juveniles have been known to avoid brackish conditions; the northwest Atlantic subpopulation is known to be migratory. The average spinner shark weighs 56 kg. Indo-Pacific sharks are larger than those from the northwest Atlantic; this species has a slim, streamlined body with a distinctive, pointed snout. The eyes are circular. Prominent forward-pointing furrows occur at the corners of the mouth; the tooth rows number 15–18 in each half of the upper jaw and 14–17 in each half of the lower jaw, with two and one tiny symphysial teeth, respectively.
The teeth have long, narrow central cusps and are finely serrated in the upper jaw and smooth in the lower jaw. The five pairs of gill slits are long; the first dorsal fin is small and originates behind the free rear tip of the pectoral fins. No ridge exists between the second dorsal fins; the pectoral fins are moderately short and falcate. The body is densely covered with diamond-shaped dermal denticles with seven shallow horizontal ridges; the coloration is gray above, sometimes with a bronze sheen, white below, with a faint white band on the sides. Young individuals have unmarked fins; the spinner shark differs from the blacktip shark in that its first dorsal fin is more triangular in shape and is placed further back on the body. Adults can be dist
In biology, mating is the pairing of either opposite-sex or hermaphroditic organisms for the purposes of sexual reproduction. Some definitions limit the term to pairing between animals, while other definitions extend the term to mating in plants and fungi. Fertilization is the fusion of both sex gamete. Copulation is the union of the sex organs of two sexually reproducing animals for insemination and subsequent internal fertilization. Mating may lead to external fertilization, as seen in amphibians and plants. For the majority of species, mating is between two individuals of opposite sexes. However, for some hermaphroditic species, copulation is not required because the parent organism is capable of self-fertilization; the term mating is applied to related processes in bacteria and viruses. Mating in these cases involves the pairing of individuals, accompanied by the pairing of their homologous chromosomes and exchange of genomic information leading to formation of recombinant progeny. For animals, mating strategies include random mating, disassortative mating, assortative mating, or a mating pool.
In some birds, it includes behaviors such as feeding offspring. The human practice of mating and artificially inseminating domesticated animals is part of animal husbandry. In some terrestrial arthropods, including insects representing basal phylogenetic clades, the male deposits spermatozoa on the substrate, sometimes stored within a special structure. Courtship involves inducing the female to take up the sperm package into her genital opening without actual copulation. In groups such as dragonflies and many spiders, males extrude sperm into secondary copulatory structures removed from their genital opening, which are used to inseminate the female. In advanced groups of insects, the male uses its aedeagus, a structure formed from the terminal segments of the abdomen, to deposit sperm directly into the female's reproductive tract. Other animals reproduce sexually including many basal vertebrates. Vertebrates reproduce with internal fertilization through cloacal copulation, while mammals copulate vaginally.
Like in animals, mating in other Eukaryotes, such as plants and fungi, denotes sexual conjugation. However, in vascular plants this is achieved without physical contact between mating individuals, in some cases, e.g. in fungi no distinguishable male or female organs exist. Yeasts are eukaryotic microorganisms classified in the kingdom Fungi, with 1,500 species described. In general, under high stress conditions like nutrient starvation, haploid cells will die. Protists are a large group of diverse eukaryotic microorganisms unicellular animals and plants, that do not form tissues. Eukaryotes emerged in evolution more than 1.5 billion years ago. The earliest eukaryotes were protists. Mating and sexual reproduction are widespread among extant eukaryotes including protists such as Paramecium and Chlamydomonas. In many eukaryotic species, mating is promoted by sex pheromones including the protist Blepharisma japonicum. Based on a phylogenetic analysis and Roger proposed that facultative sex was present in the common ancestor of all eukaryotes.
However, to many biologists it seemed unlikely until that mating and sex could be a primordial and fundamental characteristic of eukaryotes. A principal reason for this view was that mating and sex appeared to be lacking in certain pathogenic protists whose ancestors branched off early from the eukaryotic family tree. However, several of these protists are now known to be capable of, or to have had, the capability for meiosis and hence mating. To cite one example, the common intestinal parasite Giardia intestinalis was once considered to be a descendant of a protist lineage that predated the emergence of meiosis and sex. However, G. intestinalis was found to have a core set of genes that function in meiosis and that are present among sexual eukaryotes. These results suggested that G. intestinalis is capable of meiosis and thus mating and sexual reproduction. Furthermore, direct evidence for meiotic recombination, indicative of mating and sexual reproduction, was found in G. intestinalis. Other protists for which evidence of mating and sexual reproduction has been described are parasitic protozoa of the genus Leishmania, Trichomonas vaginalis, acanthamoeba.
Protists reproduce asexually under favorable environmental conditions, but tend to reproduce sexually under stressful conditions, such as starvation or heat shock. Animal husbandry Breeding in the wild Breeding season Evolution of sex Lordosis behavior Mate choice copying Mating system Reproduction Sex determination system Sexual conflict Sexual intercourse Introduction to Animal Reproduction Advantages of Sexual Reproduction
Chimaeras are cartilaginous fish in the order Chimaeriformes, known informally as ghost sharks, rat fish, spookfish or rabbit fish. At one time a "diverse and abundant" group, their closest living relatives are sharks, though their last common ancestor with sharks lived nearly 400 million years ago. Today, they are confined to deep water. Chimaeras live in temperate ocean floors down to 2,600 m deep, with few occurring at depths shallower than 200 m. Exceptions include the members of the genus Callorhinchus, the rabbit fish and the spotted ratfish, which locally or periodically can be found at shallow depths; these are among the few species from the Chimaera order kept in public aquaria. They have soft bodies, with a bulky head and a single gill-opening, they grow up to 150 cm in length. In many species, the snout is modified into an elongated sensory organ. Like other members of the class Chondrichthyes, chimaera skeletons are constructed of cartilage, their skin is smooth and covered by placoid scales, their color can range from black to brownish gray.
For defense, most chimaeras have a venomous spine in front of the dorsal fin. Chimaeras resemble sharks in some ways: they employ claspers for internal fertilization of females and they lay eggs with leathery cases, they use electroreception to find their prey. However, unlike sharks, male chimaeras have retractable sexual appendages on the forehead and in front of the pelvic fins; the females lay eggs in leathery egg cases. They differ from sharks in that their upper jaws are fused with their skulls and they have separate anal and urogenital openings, they lack sharks' many sharp and replaceable teeth, having instead just three pairs of large permanent grinding tooth plates. They have gill covers or opercula like bony fishes. In some classifications, the chimaeras are included in the class Chondrichthyes of cartilaginous fishes. Chimaeras have some characteristics of bony fishes. A renewed effort to explore deep water and to undertake taxonomic analysis of specimens in museum collections led to a boom during the first decade of the 21st century in the number of new species identified.
They are 50 extant species in six genera and four families are described. James, Long & Didier, 2009 Hydrolagus mirabilis Collett, 1904 Hydrolagus mitsukurii Jordan & Snyder, 1904 Hydrolagus novaezealandiae Fowler, 1911 Hydrolagus ogilbyi Waite, 1898 Hydrolagus pallidus Hardy & Stehmann, 1990 Hydrolagus purpurescens Gilbert, 1905 Hydrolagus trolli Didier & Séret, 2002 Hydrolagus waitei Fowler, 1907 Family Rhinochimaeridae Garman, 1901 Genus Harriotta Goode & Bean, 1895 Harriotta haeckeli Karrer, 1972 Harriotta raleighana Goode & Bean, 1895 Genus Neoharriotta Bigelow & Schroeder, 1950 Neoharriotta carri Bullis & J. S. Carpenter, 1966 Neoharriotta pinnata Schnakenbeck, 1931 Neoharriotta pumila Didier & Stehmann, 1996 Genus Rhinochimaera Garman, 1901 Rhinochimaera africana Compagno, Stehmann & Ebert
Pelvic fins are paired fins located on the ventral surface of fish. The paired pelvic fins are homologous to the hindlimbs of tetrapods. In actinopterygians, the pelvic fin consists of two endochondrally-derived bony girdles attached to bony radials. Dermal fin rays are positioned distally from the radials. There are three pairs of muscles each on the dorsal and ventral side of the pelvic fin girdle that abduct and adduct the fin from the body. Pelvic fin structures can be specialized in actinopterygians. Gobiids and lumpsuckers modify their pelvic fins into a sucker disk that allow them to adhere to the substrate or climb structures, such as waterfalls. In priapiumfish, males have modified their pelvic structures into a spiny copulatory device that grasps the female during mating. In actinopterygian steady state swimming, the pelvic fins are controlled and used to provide powered corrective forces. Careful timing of the pelvic fin movement during whole-body movements allows the pelvic fins to generate forces that dampen the forces from the entire body, therefore stabilizing the fish.
For maneuvers, electromyogram data shows that pelvic fin muscles are activated after the start of the maneuver, indicating that the fins are used more for stabilization instead of generating the maneuver. In rays and skates, pelvic fins can be used for "punting," where they asynchronously or synchronously push off the substrate to propel the animal forwards. Unlike limb development in tetrapods, where the forelimb and hindlimb buds emerge at the same timepoint, the pelvic fin bud emerges much than the pectoral fin. While the pectoral fin bud is apparent at 36 hours post fertilization in zebrafish, the pelvic fin bud is only clear at around 21 days post fertilization when the animal is 8 mm in length. In zebrafish, the pelvic fin bud starts as a mesenchymal condensation that forms an apical ectodermal thickening. A fin fold forms from this thickening, invaded by migratory mesenchyme, separating the fin bud into the proximal mesenchyme and the distal mesenchyme
Chondrichthyes is a class that contains the cartilaginous fishes: they are jawed vertebrates with paired fins, paired nares, scales, a heart with its chambers in series, skeletons made of cartilage rather than bone. The class is divided into two subclasses: Holocephali. Within the infraphylum Gnathostomata, cartilaginous fishes are distinct from all other jawed vertebrates; the skeleton is cartilaginous. The notochord is replaced by a vertebral column during development, except in Holocephali, where the notochord stays intact. In some deepwater sharks, the column is reduced; as they do not have bone marrow, red blood cells are produced in the epigonal organ. They are produced in the Leydig's organ, only found in certain cartilaginous fishes; the subclass Holocephali, a specialized group, lacks both the Leydig's and epigonal organs. Apart from electric rays, which have a thick and flabby body, with soft, loose skin, chondrichthyans have tough skin covered with dermal teeth called placoid scales, making it feel like sandpaper.
In most species, all dermal denticles are oriented in one direction, making the skin feel smooth if rubbed in one direction and rough if rubbed in the other. The pectoral and pelvic girdles, which do not contain any dermal elements, did not connect. In forms, each pair of fins became ventrally connected in the middle when scapulocoracoid and pubioischiadic bars evolved. In rays, the pectoral fins have connected to the head and are flexible. One of the primary characteristics present in most sharks is the heterocercal tail, which aids in locomotion. Chondrichthyans have toothlike scales called placoid scales. Denticles provide protection, in most cases, streamlining. Mucous glands exist in some species, as well, it is assumed that their oral teeth evolved from dermal denticles that migrated into the mouth, but it could be the other way around, as the teleost bony fish Denticeps clupeoides has most of its head covered by dermal teeth. This is most a secondary evolved characteristic, which means there is not a connection between the teeth and the original dermal scales.
The old placoderms had sharp bony plates in their mouth. Thus, it is unknown whether the oral teeth evolved first, it has been suggested that the original bony plates of all vertebrates are now gone and that the present scales are just modified teeth if both the teeth and body armor had a common origin a long time ago. However, there is no evidence of this. All chondrichthyans breathe through five depending on the species. In general, pelagic species must keep swimming to keep oxygenated water moving through their gills, whilst demersal species can pump water in through their spiracles and out through their gills. However, this is only a general rule and many species differ. A spiracle is a small hole found behind each eye; these can be tiny and circular, such as found on the nurse shark, to extended and slit-like, such as found on the wobbegongs. Many larger, pelagic species, such as the mackerel sharks and the thresher sharks, no longer possess them. Chondrichthyes nervous system is composed of a small brain, 8-10 pairs of cranial nerves, a spinal chord with spinal nerves.
They have several sensory organs. Ampullae of Lorenzini are a network of small jelly filled pores called electroreceptors which help the fish sense electric fields in water; this aids in finding prey and sensing temperature. The Lateral line system has modified epithelial cells located externally which sense motion and pressure in the water around them. Most subspecies have large well-developed eyes, they have powerful nostrils and olfactory organs. Their inner ears consist of 3 large semicircular canals which aid in orientation, their sound detecting apparatus has limited range and is more powerful at lower frequencies. Some subspecies have electric organs which can be used for predation, they have simple brains with the forebrain not enlarged. The structure and formation of myelin in their nervous systems are nearly identical to that of tetrapods, which has led evolutionary biologists to believe that Chondrichthyes were a cornerstone group in the evolutionary timeline of myelin development. Like all other jawed vertebrates, members of Chondrichthyes have an adaptive immune system.
Fertilization is internal. Development is live birth but can be through eggs; some rare species are viviparous. There is no parental care after birth. Capture-induced premature birth and abortion occurs in sharks/rays when fished. Capture-induced parturition is mistaken for natural birth by recreational fishers and is considered in commercial fisheries management despite being shown to occur in at least 12% of live bearing sharks and rays; the class Chondrichthyes has two subclasses: the subclass Elasmobranchii
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 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. Wobbegongs are bottom-dwelling sharks, so they spend much of their time resting on the sea floor. Most species have a maximum length of 1.25 m or less, but the largest, the spotted wobbegong, Orectolobus maculatus, banded wobbegong, O. halei, reach about 3 m in length. Wobbegongs are well camouflaged with a symmetrical pattern of bold markings which resembles a carpet; because of this striking pattern and their close relatives are referred to as carpet sharks. The camouflage is improved by the presence of small weed-like whisker lobes surrounding the wobbegong's jaw, which help to camouflage it and act as sensory barbs.
Wobbegongs make use of their relative invisibility to hide among rocks and catch smaller fish which swim too close, typical of ambush predators. Wobbegongs are not considered dangerous to humans, but have attacked swimmers, snorkellers and SCUBA divers who inadvertently come close to them; the Australian Shark Attack File contains more than 50 records of unprovoked attacks by wobbegongs, the International Shark Attack File 28 records. Wobbegongs have bitten surfers. Wobbegongs are flexible and can bite a hand holding onto their tail, they have many small but sharp teeth and their bite can be severe through a wetsuit. There are many more instances of unprovoked attacks on wobbegongs: in Australia, the flesh of wobbegongs and other shark species is called flake and it is the "fish" component of fish and chips. Wobbegong skin is used to make leather. Although most wobbegong species are unsuitable for home aquaria due to their large adult size, this has not stopped some of the larger species from being sold in the aquarium trade.
Small wobbegong species, such as the tasselled wobbegong and Ward's wobbegong, are "ideal" sharks for home aquarists to keep because they are an appropriate size and are lethargic, enabling them to be accommodated within the limited space of home aquaria, although they will consume tankmates quite large ones. Some aquarists, by contrast, see the lack of activity to be a drawback to keeping wobbegongs and prefer more active sharks. Wobbegongs are nocturnal and, due to their slow metabolism, do not have to be fed as as other sharks. Most do well on two feedings weekly. Underfed wobbegongs can be recognised by visibly atrophied dorsal musculature; the 12 living species of wobbegong, in three genera, are: Genus Eucrossorhinus Regan, 1908 Eucrossorhinus dasypogon Genus Orectolobus Bonaparte, 1834 Orectolobus floridus Last & Chidlow, 2008 Orectolobus halei Whitley, 1940. Orectolobus hutchinsi Last, Chidlow & Compagno, 2006. Orectolobus japonicus Regan, 1906 Orectolobus leptolineatus Last, Pogonoski & W. T. White, 2010 Orectolobus maculatus Orectolobus ornatus Orectolobus parvimaculatus Last & Chidlow, 2008 Orectolobus reticulatus Last, Pogonoski & W. T. White, 2008 Orectolobus wardi Whitley, 1939 Genus Sutorectus Whitley, 1939 Sutorectus tentaculatus Fossil genera include: Eometlaouia Noubhani & Cappetta, 2002 List of sharks Froese and Daniel Pauly, eds..
"Orectolobidae" in FishBase. April 2017 version. "Spotted Wobbegong, Orectolobus maculatus". Australian Museum
In animal anatomy, a cloaca kloh-AY-kə is the posterior orifice that serves as the only opening for the digestive and urinary tracts of many vertebrate animals, opening at the vent. All amphibians, reptiles, a few mammals have this orifice, from which they excrete both urine and feces. Excretory openings with analogous purpose in some invertebrates are sometimes referred to as cloacae. Mating by cloaca is known as cloacal copulation referred to as cloacal kiss; the cloacal region is often associated with a secretory organ, the cloacal gland, implicated in the scent-marking behavior of some reptiles, marsupials and monotremes. The word is from the Latin verb cluo, "to cleanse", thus the noun cloaca, "sewer, drain". Birds reproduce using their cloaca. Birds that mate using this method touch their cloacae together, in some species for only a few seconds, sufficient time for sperm to be transferred from the male to the female. For some birds, such as ostriches, kiwi and some species of swans and ducks, the males do not use the cloaca for reproduction, but have a phallus.
In those, the penis helps ensure. One study has looked into birds. Among fish, a true cloaca is present only in lobe-finned fishes. In lampreys and in some ray-finned fishes, part of the cloaca remains in the adult to receive the urinary and reproductive ducts, although the anus always opens separately. In chimaeras and most teleosts, all three openings are separated. With a few exceptions noted below, mammals have no cloaca. In those that have one, the cloaca is subdivided into separate regions for the anus and urethra; the monotremes possess a true cloaca. In marsupials, the genital tract is separate from the anus, but a trace of the original cloaca does remain externally; this is one of the features of marsupials that suggest their basal nature, as the amniotes from which mammals evolved possessed a cloaca, the earliest animals to diverge into the mammalian class would most have had this feature, too. Unlike other marsupials, marsupial moles have a true cloaca, a fact, used to argue against a marsupial identity for these mammals.
Most adult placental mammals have no remaining trace of the cloaca. In the embryo, the embryonic cloaca divides into a posterior region that becomes part of the anus, an anterior region that has different fates depending on the sex of the individual: in females, it develops into the vestibule that receives the urethra and vagina, while in males it forms the entirety of the penile urethra. However, the tenrecs and golden moles, small placental mammals native to Africa, as well as some shrews retain a cloaca as adults. Being placental animals, humans only have an embryonic cloaca, split up into separate tracts during the development of the urinary and reproductive organs. However, a few human congenital disorders result in persons being born with a cloaca, including persistent cloaca and sirenomelia. In reptiles, the cloaca consists of the urodeum and coprodeum; some species have modified cloacae for increased gas exchange. This is; some turtles those specialized in diving, are reliant on cloacal respiration during dives.
They accomplish this by having a pair of accessory air bladders connected to the cloaca which can absorb oxygen from the water. Various fish, as well as polychaete worms and crabs, are specialized to take advantage of the constant flow of water through the cloacal respiratory tree of sea cucumbers while gaining the protection of living within the sea cucumber itself. At night, many of these species emerge from the anus of the sea cucumber in search of food. Cloaca