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Are there fishes with a double circulatory system?

Are there fishes with a double circulatory system?


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Our courseware materials say there are such fishes, but my Internet searches suggests fishes only have a single circulatory system.


It seems that lungfish display the beginnings of a double circulatory system:


Circulatory system

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Circulatory system, system that transports nutrients, respiratory gases, and metabolic products throughout a living organism, permitting integration among the various tissues. The process of circulation includes the intake of metabolic materials, the conveyance of these materials throughout the organism, and the return of harmful by-products to the environment.

Invertebrate animals have a great variety of liquids, cells, and modes of circulation, though many invertebrates have what is called an open system, in which fluid passes more or less freely throughout the tissues or defined areas of tissue. All vertebrates, however, have a closed system—that is, their circulatory system transmits fluid through an intricate network of vessels. This system contains two fluids, blood and lymph, and functions by means of two interacting modes of circulation, the cardiovascular system and the lymphatic system both the fluid components and the vessels through which they flow reach their greatest elaboration and specialization in the mammalian systems and, particularly, in the human body.

A full treatment of human blood and its various components can be found in the article human blood. A discussion of how the systems of circulation, respiration, and metabolism work together within an animal organism is found in the article respiration.


Are there fishes with a double circulatory system? - Biology

Trends in organ systems - Vertebrate circulatory systems

The metabolic activity of any tissue is limited by its blood supply the more active any organ, the more blood it needs and the more extensive its vascularization.

The changes in metabolic activity associated with endothermy and the change from gill to lung respiration has led to changes in vertebrate circulatory systems.

In general, blood is pumped by heart to arteries -> arterioles -> capillaries.

Capillaries come together to form venioles -> veins -> major venous trunks

Veins between two capillary networks are portal systems.

Closed circulatory system, but fluid constituents of blood leak out of capillaries and return to the heart by the second component of the circulatory system, the lymphatic system.

Considerable adaptability built into vertebrate circulatory systems:

Considerable variation in blood vessels, as seen in shark

Due to developmental origin of blood vessels: many channels form, some enlarge to form major blood vessels, some of which atrophy and die.

A piece of a vein grafted into an artery transforms structurally to become an artery.

Nearly any vessel can be tied off gradually and system can enlarge alternate routes.

Blood can, and does, flow in either direction in several vessels.

Blood can be diverted towards or away from any part of the body, volume of circulating blood can be changed, rate of circulation can be changed 5-fold.

Despite this variability, the structure of the heart and major vessels tells us a lot about the evolutionary history of vertebrates and the evolutionary changes that have greatly modified vertebrate circulatory systems.

Circulatory system is the first organ system to become functional during development.

On each side of embryo, an aorta forms ventrally and swings dorsally.

The paired aortae in ventral position fuse along a short section and form a single vessel, the beginning of the heart.

The posterior part of the fusion forms the sinus venosus, receiving the major venous trunks flowing back to the heart.

Four sequential chambers of the heart exist, from posterior to anterior:

1. thin-walled sinus venosus

3. thick walled single ventricle

The adult heart (fish or amniote) develops from this simple pattern.

The heart takes on its final adult form from a number of possible modifications:

differential growth of certain parts

fusion of adjacent regions

disappearance of partitions

formation of new partitions

In amniotes, the heart overgrows its pericardial space and doubles up on itself to form a loop that swings to the right side of the pericardial cavity.

This twisting results in the shape of the heart and the positioning of the atria and ventricles seen in adult amniotes.

Comparative anatomy of the heart

The large sinus venosus receives blood from the common cardinal veins on the side of the body and the hepatic veins from the liver.

Single chambered atrium balloons out dorsally on each side of the muscular ventricle .

Blood flows into ventricle, which opens into the conus arteriosus where a series of valves prevent back flow of blood.

The regions of the heart form an S-shaped loop, to fit into pericardial cavity.

The heart of the fish contains completely deoxygenated blood and has a single circulatory system.

In lungfish, the heart is partially divided into a right and left atrium.

The sinus venosus opens into the right side of the atrium.

Vessels from the lung return oxygenated blood to the left atrium (pulmonary vein).

The ventricle and conus arteriosus are also partially divided, although there is some mixing of deoxygenated and oxygenated blood.

As blood goes through the conus arteriosus, a branch carries oxygenated blood from the left side of the ventricle to the anterior gills.

A second branch of the conus carries deoxygenated blood to posterior gills and the lungs from the right side of the ventricle.

This is the beginning of the double circulatory system.

The sinus venosus has shifted to the right and empties into right atrium, which is completely separated from left atrium by a thin interatrial septum.

From the right atrium, the blood goes into a single large muscular ventricle.

In the ventricle, muscular folds or trabeculae reduce the mixing of blood between the right and left sides of the ventricle.

Blood from the right side of the ventricle flows into the conus arteriosus, where a spiral valve through the middle of the conus separates the flow of blood into two channels.

The deoxygenated blood from the right side of the ventricle passes on one side of the spiral valve and flows through the pulmonary artery to lungs, skin or gills.

Pulmonary veins return oxygenated blood to the left atrium, to the left side of the ventricle and then on the other side of the spiral valve into the systemic arteries.

Left and right sides of the heart become more separated.

Atria are completely separate, ventricles are almost completely separated, except for a small gap that allows some blood to spill between chambers, resulting in some mixing of blood.

In crocodiles, the gap is closed, the ventricle is completely divided and there is complete separation.

The conus arteriosus is split into the pulmonary trunk and two aortic trunks.

The left aortic trunk emerges from the right ventricle and the right aortic trunk emerges from the left ventricle.

Pulmonary veins return oxygenated blood to the left atrium.

Blood from the pulmonary vein passes to the left ventricle and from there to the right aortic arch.

Heart has completely separated: 2 atria, 2 ventricles, 4 chambers, and adult bird has complete double circulation: low-pressure pulmonary circuit using the right side of the heart and a high-pressure systemic circuit using the left side of the heart.

The sinus venosus is completely incorporated into the wall of the right atrium.

Blood passes from the right atrium to the small right ventricle and from there to the pulmonary trunk.

Pulmonary veins return blood to the left atrium, goes to the thick walled left ventricle, then to the single right aortic arch then on to body.

Also 4 chambered heart, with full double circulation.

Sinus venosus is incorporated into the wall of the right atrium.

Atria and ventricles are completely divided.

Blood is forced from the right ventricle to the pulmonary trunk and lungs.

Pulmonary veins return oxygenated blood to left atrium, passed to left ventricle, then on to left aortic arch for distribution to body.

Birds and mammals have double circulation.

During the fetal development of mammals, the interatrial septum has an opening covered by a valve-like flap. This opening allows the blood from the right atrium to pass into the left atrium and bypass pulmonary circulation. Claps shut at birth.

Evolutionary changes in vertebrate heart are tied to change from single to double circuit heart, with increased separation of oxygenated and deoxygenated blood, allowing more efficient respiration and circulation to fuel high activity and increased oxygen demands associated with endothermy.

Summary of cardiac evolution:

1. Sinus venosus of birds and mammals merges into wall of right atrium.

2. Atrium is partly divided in lungfishes (and salamanders), completely divided in other tetrapods

3. Conus is partly divided by a spiral fold in lungfishes and frogs. It is completely divided into three trunks in reptiles and into two trunks in birds and mammals

The changes to the heart were accompanied by changes to the aortic arches and thus to the rest of the circulatory system.

The dorsal aorta is a continuous vessel in embryo, bent to form a series of aortic arches.

[st bend = 1st aortic arch

When the pharyngeal arches develop, cross links are formed between the dorsal and ventral aortae, one for each pharyngeal arch.

Almost all vertebrate embryos exhibit 6 aortic arches.

Ancestral condition (shown in some vertebrate embryos) may have more.

In gill breathing fishes, the aortic arches are retained and provide afferent branchial arteries to the gill arches.

In adult vertebrates that lack gills, the embryonic and ancestral pattern of 6 aortic arches is highly modified with development.

The most extreme modifications occur in birds and mammals, but the beginnings of these changes can be seen in fish.

These modifications revolve around change from gill to lung respiration and the evolution of the double circulatory system.

Figure 11.13A shows ancestral condition, seen from side of animal, with 6 aortic arches (anterior arches have been lost).

Figure 11.13B - gill respiration

The aortic arches of gill bearing vertebrates are primarily for bringing blood from the heart via the ventral aorta through the gills, where the blood is oxygenated and drained via the efferent branchial arteries into the dorsal aorta for circulation to the body.

Fish embryos have 6 arteries, but the first arch (I) is generally lost or modified.

The 2nd arch (II) is present in elasmobranchia, but is lost in many other fish.

Figure 11.13D - gills and lungs present

Lungfish depend on lungs for breathing and have lost the capillary networks associated with gills of arches III and IV. The corresponding arches III and IV are uninterrupted vessels.

When arches I and II are lost, the anterior extensions of the dorsal aorta from arch III continues to the head as the internal carotid arteries .

V & VI still have gill capillary networks.

Pulmonary arteries arise as vessels from arch VI, go to lungs of lungfish or swim bladder in coelocanth.

Pulmonary veins return blood to heart via the left atrium.

Not a highly efficient system, but has some ability to shunt blood to regions of the body where increased demand for oxygen is necessary

Changes from elasmobranch -> lungfish, with evolution of pulmonary circulation, are one of the most important steps in the evolution of circulatory systems of vertebrates

Changes become more pronounced

Arches I and II disappear during development.

Arch V disappears in anurans, but is present in some urodeles (salamanders), leaving intact arches III, IV, VI

Dorsal link between III and IV gets thin in urodeles (salamanders) and almost disappears in anurans.

Arch III is now the internal carotid artery .

Right and left arches of arch IV are now right and left sides of systemic aorta.

Arch VI is intact and goes to lung.

Aortic arches I, II, V disappear.

Dorsal connection between III and IV may be lost (not shown in diagram)

Arch III forms part of the internal carotid arteries and forward extensions of ventral aortae form external carotid arteries .

3 vessels emerge from the ventricle:

1. a pulmonary trunk that branches to the pulmonary arteries, formed from arch VI from right ventricle

2 & 3: a right and left systemic aortic arch derived from arch IV

generally right systemic arch (IV) comes from left side of ventricle and

left systemic arch (IV) comes from right side of ventricle

Arch IV forms systemic aorta on right side and first part of subclavian artery on left side

Left root of dorsal aorta disappears, while the one on the right remains and becomes the aortic arch.

Arch III -> internal and external carotid arteries

Aortic arches of mammals have same developmental history and fate as those of birds, with one big exception.

Outstanding difference between bird and mammal is that the aortic arch in the bird is derived from the right side of aortic arch IV and that of the mammals is derived from the left side of aortic arch IV.

Systemic aorta in mammals emerges from left ventricle and goes sharply to the left.

The right aortic arch forms the first part of the right subclavian artery.

From the right subclavian artery emerges the right common carotid, going to the head and neck.

The common trunk of the right subclavian and the right common carotid is called the brachiocephalic artery.

Summary of evolutionary changes in vertebrate circulation:

Separation of right and left atrium

increasing separation of right and left ventricles

Deoxygenated blood on right side of the heart, oxygenated blood on left side of the heart

In ancestral condition, separation is not complete, but structures like trabeculae help to maintain separation.

Aortic arches: changes associated with heart changes

Modification of arches III, VI (pulmonary circulation)

Retention of both sides of arch IV to form aortic arch in reptiles

Birds lose left side, mammals lose right side of arch IV.

Evolution of circulatory system

Trend for separation of oxygenated and deoxygenated blood

These changes resulted from the changes from gill to lung respiration, change from aquatic to terrestrial life.

Changes led to the development (in lungfish) of a double circulatory system from a single circulatory system.

These changes provided a more efficient circulatory and respiratory system to fuel the high activity levels and active metabolism associate with endothermy.


Problem: The circulatory systems of bony fishes, rays, and sharks are most similar to ________.a. those of birds, with a four-chambered heartb. the portal systems of mammals, where two capillary beds occur sequentially, without passage of blood through a pumping chamberc. those of sponges, where gas exchange in all cells occurs directly with the external environmentd. those of humans, where there are four pumping chambers to drive blood flow

The circulatory systems of bony fishes, rays, and sharks are most similar to ________.

a. those of birds, with a four-chambered heart

b. the portal systems of mammals, where two capillary beds occur sequentially, without passage of blood through a pumping chamber

c. those of sponges, where gas exchange in all cells occurs directly with the external environment

d. those of humans, where there are four pumping chambers to drive blood flow

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Our tutors have indicated that to solve this problem you will need to apply the Circulatory and Respiratory Anatomy concept. You can view video lessons to learn Circulatory and Respiratory Anatomy. Or if you need more Circulatory and Respiratory Anatomy practice, you can also practice Circulatory and Respiratory Anatomy practice problems.

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OCR Biology New A-level H420 Paper 1,2,3 (2019) Predictions + Exam Discussion Thread

Yeah you weren&rsquot meant to. It said compare circulatory systems for a reason! You did the right thing )

Not open closed because fish dont have open circulatory systems I talked about :

- both closed
- single vs double
- countercurrent vs capillaries just flowing past

(Original post by Meduser)
Yeah you weren&rsquot meant to. It said compare circulatory systems for a reason! You did the right thing )

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Teaching resources

Where to start?

I think it is helpful to begin with the components and function of blood – the stuff that you are transporting. Get a jug – fill it with water (plasma). Now add in some white blood cells (polystyrene), red blood cells (Cheerios stained with red dye) and platelets (plasters). Take this blood to the ‘stomach’ – add in some salts (NaCl) and glucose (sugar). You could also add in amino acids (glitter) and lipids (oil) too. Add in some urea (yellow balls) from Liver. Blow into the mixture some oxygen. Give it a good stir. Now how do we get these substances to the cells in our foot? What waste substances will now be added (carbon dioxide).

Components of blood

GCSE and Key Stage 3 worksheet looking at the different components of blood. The worksheet starts by assessing prior knowledge with students having to list what substances are present in blood. We then look at a sample of blood after centrifugation and students list what substances and cells are present in each fraction. Finally we think about how blood from different people may vary. (PDF)

Adaptations of veins, arteries and capillaries

GCSE worksheet on adaptations of veins, capillaries and arteries. Students use different tubes to help them understand how veins, capillaries and arteries are adapted for their function. This activity is designed so that students have a overall understanding of blood flow first and how this links to respiration. (PDF)

Heart structure

GCSE worksheet on labelling heart structure. Students label four diagrams of the heart and evaluate the models from the perspectives of different individuals. This activity offers a more challenging way to introduce what can be quite a low-level task of labelling a heart. This resource was made in collaboration with Thomas Kitwood. (PDF)


Alopias pelagicus

Alopias pelagicus. Photo © Doug Perrine

These sharks are easily recognized for their long upper caudal fin lobes (the top half of their tail fin), which they use to stun smaller fish and squid, making them easier to catch. They are not considered a danger to humans. Historically, they were prized for their large livers, from which squalene oil was extracted to be used in cosmetics, health food, and high-grade machine oil.

Order – Lamniformes Family – Alopiidae Genus – Alopias Species – pelagicus

Common Names

Common names for threshers (Alopias spp.) include such terms as fox shark, fox-shark, foxtail, thresher, thrasher, sickletail, swingletail, and swiveltail. The only other common English name for the pelagic thresher is smalltooth thresher. Other language common names for this species include: cá nhám duôi dài (Vietnamese), hwan-do-sang-o (Korean), kleintand-sambokhaai (Afrikaans), kooseh-e-derazdom (Farsi), nitari (Japanese), pating (Maranao/Samal/Tao Sug), pesce volpe pelagico (Italian), pelagický zralok mlatec (Czech), peagische voshaai (Dutch), quian hai cháng wei sha (Mandarin Chinese), renard pélagique & requin-renard (French), stillehavsraevehaj (Danish), stillahavsrävhaj (Swedish), tubarao-raposo-do-indico (Portuguese), ulappakettuhai (Finnish), and zorro de mar & zorro pelágico (Spanish).

Importance to Humans

Alopias pelagicus. Photo © Doug Perrine

Pelagic thresher meat is consumed in many countries, and its fins are used in the Asian shark fin trade. The hide is sometimes made into leather, and liver oil utilized for vitamin extraction. The pelagic thresher contains ten percent of its total body weight as liver weight. The oil from the liver, known as squalene oil, is sometimes used in the manufacture of cosmetics, health foods, and high-grade machine oil. This species is rarely targeted except in the central Pacific and northwestern Indian oceans, but is often caught as a bycatch on floating longline gear set for other sharks, tunas, or swordfish. It is also (rarely) caught in gill nets. Pelagic thresher landings in northeastern Taiwan used to constitute 12% by weight of the total annual shark landings.

All three species of Thresher shark are considered game fish by the International Game Fish Association (IGFA) and are targeted using rod and reel wherever they occur. The largest records having been caught in New Zealand waters, while light-tackle thresher records have been set off California. Threshers, including the pelagic thresher, are eagerly sought after by anglers in Australia, Britain, California, New England (USA), and New Zealand. Famous big-game angler and record holder Zane Grey, writing about the threshers of New Zealand, called these sharks “exceedingly stubborn. Comparing him with the mako, he is pound for pound, a harder fish to whip”.

Danger to Humans

Although this species looks formidable, it is practically harmless and generally avoids divers and swimmers.

Conservation

This species is currently being exploited by directed fisheries (southern California and elsewhere), and is caught accidentally in various floating longline fisheries for tunas and swordfish. Fishing pressure may include being caught in its nursery areas. Fishing pressure combined with its very limited reproductive potential and other life history traits make the pelagic thresher extremely vulnerable. The pelagic thresher probably cannot support intensive exploitation. This species is currently not protected anywhere in the world.

The IUCN is a global union of states, governmental agencies, and non-governmental organizations in a partnership that assesses the conservation status of species.

Geographical Distribution

World distribution map for the pelagic thresher

The pelagic thresher occurs in warm and temperate offshore waters of the Pacific and Indian oceans, including the Mediterranean Sea. This species is abundant off the northeastern coast of Taiwan. In North American waters, this species is found off California and Mexico. Distribution data is imprecise due to confusion with the common thresher, and the pelagic thresher may occur over a wider area than is presently known.

Habitat

The pelagic thresher inhabits surface waters of the open ocean, from the surface to at least 150 m (492 ft) deep. It also sometimes occurs in cool inshore waters. It is not known if this species ascends the water column at night, as does the bigeye thresher, Alopias superciliosus. The habitat of this species is poorly known.

Biology

Alopias pelagicus. Image courtesy FAO Sharks of the World

All threshers are primarily oceanic sharks with extremely long upper caudal fin lobes. The pelagic thresher closely resembles, and is often confused with, the common thresher but can be distinguished from this species by the presence of dark patches of skin above the pectoral fin bases and by the absence of labial furrows. Common threshers lack lateral cusplets (denticles) on their teeth. The pelagic thresher can be easily distinguished from the bigeye thresher by its smaller eyes and by the absence of deep horizontal grooves along the anterior dorsal surface.

Alopias pelagicus. Photo © Doug Perrine

The pelagic thresher is able to elevate its body temperature above that of the water around it by using a special circulatory system. The circulatory system, known as the retia mirabilia, conserves body warmth by routing arterial blood which has been cooled as it passed through gill capillaries, through a network of small arterioles. These small arterioles lay very close to veins containing warm blood draining from organs and tissues. The heat diffuses from venous into the arterial blood and is re-circulated back into tissues and organs. This system allows the pelagic thresher to live in cool water, and allows its muscles to function more efficiently for faster swimming. This advanced heat conserving circulatory system is also used by other lamniforme sharks such as the porbeagle (Lamna nasus), the makos (Isurus spp.), and the white shark (Carcharodon carcharias).

Coloration
The pelagic thresher is lighter in color than the other thresher species. Dorsal surface coloration is blue-gray when alive or very fresh, fading to a pale gray shortly after death. The sides of the body are a light blue-gray (light gray shortly after death), with a white ventral surface. The gill and flank region may have a metallic silvery hue.

Lower and upper teeth from the pelagic thresher. Image courtesy FAO Sharks of the World

Dentition
The teeth of the pelagic thresher are smooth-edged and very small, having oblique cusps with lateral cusplets on their outside margins. The lateral cusplets are most pronounced in teeth along the upper jaw, and may be difficult to see without magnification. Each tooth root is curved inward. Tooth rows along the upper jaw number 21 to 22 per side, usually without a central (symphysial) tooth row. Lower jaw tooth rows number 21 per side, usually without a central tooth row. There are between 5 and 11 rows of posterior teeth.

Early stage embryos have dentition that is different from that of free-swimming pelagic threshers. Early stage embryos have teeth that are adapted to open ovulated eggs (see Reproduction). Late stage embryos are devoid of teeth, and then grow them shortly before birth.

Dermal Denticles
Pelagic threshers, like all other sharks, are covered in rough, placoid scales known as dermal denticles. Like all thresher species, the pelagic thresher has very small, smooth dermal denticles that have flat crowns and with cusps that contain parallel ridges. Dermal denticles located alongside the body have cusps that point posteriorly.

Alopias pelagicus. Photo © Doug Perrine

Size, Age & Growth
The pelagic thresher is the smallest member of the thresher family (Alopiidae). Average size is about 300 cm (10 ft) and 69.5 kg (153.3 lb). This species has been recorded to reach 500 cm (16.4 ft), but this figure is questionable and may have resulted from confusion with other threshers. Most pelagic threshers are less than 330 cm (10.8 ft) and 88.4 kg (194.9 lb). Females measure 282-292 cm (9.2-9.6 ft) at maturity, and are 8.0-9.2 years of age. Males measure 267-276 cm (8.8-9.1 ft) at maturity, and are 7.0-8.0 years of age. The pelagic thresher is known to live up to 16 years in the wild. Extrapolating growth rates for exceptionally large sharks show that large females may be over 28 years old, while large males may be significantly younger (17.5 years). Juvenile pelagic threshers grow faster than do adults. Specifically, this amounts to 9 cm/yr for ages 0-1, 8 cm/yr for ages 2-3, and 6 cm/yr for ages 5-6 versus 4 cm/yr for ages 7-10, 3 cm/yr for ages 10-12, and 2 cm/yr for ages 13 and greater.

Food Habits
Like all the threshers, the pelagic thresher feeds almost exclusively on fishes, especially herrings (Family Clupeidae), flyingfishes (Family Exocoetidae), and mackerals (Family Scombridae). It also feeds on pelagic squids. Feeding is accomplished by using the long strap-like upper caudal fin lobe to stun prey with sharp blows. Threshers are often caught on longlines with their caudal fins snagged on the hook after striking the bait with the upper caudal fin tip. Pelagic threshers, like the other thresher species, sometimes swim in circles around a school of prey, narrowing the radius and tightening the school with their long upper caudal fin lobe. By condensing the school of fishes or squids, the pelagic thresher feeds more easily on its prey.

Reproduction
Development is through aplacental viviparity. This species reaches maturity at a smaller size than other threshers. The smallest mature female recorded measured 264 cm (6.7 ft) in length. Embryos are nourished from the yolk sac in early development but later in development they feed on ovulated eggs (termed ‘oophagy’), with only one young born per uterus. Early stage embryos use their teeth to open ovulated eggs, while later stage embryos swallow the eggs whole. The yolk from the ovulated eggs are stored in the stomach for later processing. This process is known from most species out of the 16 species of lamnoid sharks. There has not been any evidence of intrauterine cannibalism (termed ‘adelphophagy’), such as is found in the sand tiger shark, Carcharias taurus. Brood size is normally two (rarely only one), and young measure between 158 and 190 cm (5.2-6.2 ft) at birth. The sex ratio of young is 1:1. Gravid females in various stages of pregnancy were recorded throughout the year from off northeastern Taiwan. The lengths of the reproductive cycle and the gestation period are presently unknown.

Alopias pelagicus. Photo © Doug Perrine

Predators
Predators of the pelagic thresher probably include large predatory fishes (including other sharks) and toothed whales (Cetacea: Odontoceti) inhabiting the same geography and habitat.

Parasites
At least three species of tapeworms are known to inhabit the spiral valve of the pelagic thresher. Litobothrium amplifica, Litobothrium daileyi, and Litobothrium nickoli are internal parasites of the pelagic thresher the last being a newly described species. These tapeworms were found in pelagic threshers caught in the Gulf of California and the Pacific coast of Mexico.

Taxonomy

The pelagic thresher was first described by the Japanese ichthyologist Hiroshi Nakamura based on three large specimens that measured between 2.9 and 3.3 m (9.4-10.8 ft) in total length. None of these specimens were kept as examples of this species (termed ‘type specimens’), although one of the three sharks and an additional fetal shark (1.0 m, 3.3 ft) was illustrated in Nakamura’s paper entitled On the two species of the thresher shark from Formosan waters, published in August, 1935. Oddly, the fetus that was illustrated may actually be a different species of thresher, the common thresher (Alopias vulpinus), based on the morphology shown in the illustration.

The valid scientific name of the pelagic thresher is Alopias pelagicus Nakamura, 1935. The only other two names for this shark appearing in past scientific literature are Alopias vulpinus Bonnaterre 1788, and Alopias superciliosus Lowe 1841 both are misidentifications of Alopias pelagicus. The generic name Alopias is derived from the Greek word alopexmeaning “fox”. The specific name pelagicus is derived from the Greek word pelagios meaning “of the sea”.


Sharks, skates, and rays : the biology of elasmobranch fishes

"Successor to the classic work in shark studies, The Elasmobranch Fishes by John Franklin Daniel (first published 1922, revised 1928 and 1934), Sharks, Skates, and Rays provides a comprehensive and up-to-date overview of elasmobranch morphology. Coverage has been expanded from anatomy to include modern information on physiology and biochemistry. The new volume also provides equal treatment for skates and rays. The authors present general introductory material for the relative novice but also review the latest technical citations, making the book a valuable primary reference resource. More than 200 illustrations supplement the text."--Jacket

Includes bibliographical references and index

Systematics and body form / Leonard J.V. Compagno -- Integumentary system and teeth / Norman E. Kemp -- Endoskeleton / Leonard J.V. Compagno -- Muscular system: gross anatomy and functional morphology of muscles / Karel F. Liem, Adam P. Summers -- Muscular system: microscopical anatomy, physiology and biochemistry of Elasmobranch muscle fibers / Quentin Bone -- Digestive system / Susanne Holmgren, Stefan Nilsson -- Respiratory system / Patrick J. Butler -- Circulatory system: anatomy of the peripheral circulatory system / Ramʹon Muñoz-Chʹapuli -- Circulatory system: distrinctive attributes of the circulation of Elasmobranch fish / Geoffrey H. Satchell -- Heart / Bruno Tota -- Nervous system / Michael H. Hofmann -- Special senses / Horst Bleckmann, Michael H. Hofmann -- Rectal gland and volume homeostasis / Kenneth R. Olson -- Urinary system / Eric R. Lacy, Enrico Reale -- Female reproductive system / William C. Hamlett, Thomas J. Koob -- Male reproductive system / William C. Hamlett -- Checklist of living Elasmobranchs / Leonard J.V. Compagno

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Single and Double Circulation Systems

The circulatory system is a broad term that encompasses the cardiovascular and lymphatic systems. The lymphatic system will be discussed later in this tutorial. The cardiovascular system consists of the heart (cardio) and the vessels required for transport of blood (vascular). The vascular system consists of arteries, veins and capillaries. Vertebrates (animals with backbones like fish, birds, reptiles, etc.), including most mammals, have closed cardiovascular systems. The two main circulation pathways in invertebrates are the single and double circulation pathways.

Single Circulatory Pathways

Single circulatory pathways as shown in the diagram below consist of a double chambered heart with an atrium and ventricle (the heart structure will be described in detail later in this tutorial). Fish possess single circulation pathways. The heart pumps deoxygenated blood to the gills where it gets oxygenated. Oxygenated blood is then supplied to the entire fish body, with deoxygenated blood returned to the heart.

Single circulation system as found in a typical fish species. The red represents oxygen-rich or oxygenated blood, the blue represents oxygen-deficient or deoxygenated blood.

Double Circulatory Systems

Double circulation pathways are found in birds and mammals. Animals with this type of circulatory system have a four-chambered heart.

The right atrium receives deoxygenated from the body and the right ventricle sends it to the lungs to be oxygenated. The left atrium receives oxygenated blood from the lungs and the left ventricle sends it to the rest of the body. Most mammals, including humans, have this type of circulatory system. These circulatory systems are called ‘double’ circulatory systems because they are made up of two circuits, referred to as the pulmonary and systemic circulatory systems.

Summary of Double Circulation. Credit: Byju’s

Humans, birds, and mammals have a four-chambered heart. Fish have a two-chambered heart, one atrium and one ventricle. Amphibians have a three-chambered heart with two atria and one ventricle. The advantage of a four chambered heart is that there is no mixture of the oxygenated and deoxygenated blood.


Interacting with Other Systems

The circulatory system touches every organ and system in your body. The system is connected to all of your body's cells so that it can transport oxygen efficiently. When you breathe, the circulatory system carries oxygen to your cells and carries dissolved carbon dioxide back to the lungs.

Every cell that needs oxygen needs access to the fluids in your circulatory system. The circulatory system and its fluids are super important to your digestive system that has absorbed nutrients from your food. Guess what? Hormones created by your endocrine system are sent through the body by the circulatory system.