User:Fama Clamosa/Sandbox3

My baleen whale sandbox.

Taxonomic classification

 * Thalassotherii, /Thalassotherii

Filter feeding
Baleen whales are carnivorous filter-feeders; they consume vast amounts of small organisms by vacuum-cleaning the ocean and not, like toothed whales, by catching preys individually. To achieve this, baleen whales typically seek out a concentration of zooplankton, swim through it, either open-mouthed or gulping, and filter the prey from the water using their baleens. The baleen is a row of a large number of keratin plates attached to the upper jaw. These plates have a composition similar to those in human hair or fingernails. They are triangular in section with the largest, inward-facing side bearing fine hairs which form a filtering mat.

Baleen whales are either continuous or intermittent filter feeders.

In the Southern Hemisphere, there are huge concentrations of krill during summers, the food preferred by baleen whales. In the Northern Hemisphere, the prey available is more variable, and, for example, humpbacks and fin whales can feed exclusively on krill around Antarctica but prey on schooling fish in the Arctic. All baleen whales except the gray whale feed near the water surface, rarely diving deeper than 100 m or for extended periods. The gray whale feed on bottom-living organisms such as amphipods in shallow waters.

All baleen whales are opportunistic hunters but they use three very different modes of filter feeding:
 * 1) balaenid whales, bowhead and right whales, use continuous ram feeding: slow swimming at a steady speed through dense patches of prey with the mouth open,
 * 2) the gray whale use suction feeding: the tongue is depressed in order to suck in prey and water
 * 3) rorquals intermittently use lunge and ram feeding: to catch prey, they engulf a large volume of prey-filled water at high speed.  They then filter the water out as their mouth closes.


 * 1) skiming
 * 2) Sediment-straining
 * 3) lunge or gulping

Continuous filter feeding
Balaenids, the bowhead and right whale, continuously filter water through their mouths and have several anatomical adaptations for this feeding mechanism: a frontal cleft between the two rows of baleen plates (known as the subrostral gap) and a large depression inside the lower lip. These adaptations are unique to these mysticetes, as are the fused cervical vertebrae, the firm tongue, and the semicircular lips that can reach up to the narrow rostrum. Balaenids regularly clean their baleen of accumulated prey. Right whales are slow swimmers with large heads and mouths. Their baleen plates are narrow and very long — up to 4 m in bowheads — and accommodated inside the enlarged lower lip which fits onto the bowed upper jaw. As the right whale swims, water and prey are guided in through the subrostral gap, while the baleen filter out the water.


 * Skim feeders swim at approximately 4 km/h through swarms of microscopic zooplankton, such as copepods, amphipods, and euphausiids, with their open mouth functioning as a huge plankton tow net. This feeding behaviour is frequently observed near the ocean surface, but analyses of stomach content and muddy and scratched rostra indicate that skim feeding occurs at all levels, including the ocean floor.  Right whales have been observed grazing this way for hours without interruption.  Balaenids have a clefts between the baleen racks called the subrostral gap.  The highly arches skull accommodates very long and narrow baleen plates.  The huge, semicircular, and highly mobile lower lips extend far above the mandible and, when the mouth is closed, they cover the baleen racks laterally and enfold the narrow rostrum.  Medial to each of these lips is gutter-like groove called the orolabial sulcus, through which filtered water passes back to the "exhaust port" at the lips trailing edge.  In balaenids, the tongue is firm, muscular, and extremely large.  Averaging 4–6% of total body mass, a tongue can weigh 2000 - 3000 kg and measure several meters in length in a standard 50-ton whale.  The cervical vertebrae are fused.

In foraging balaenids, the water enters the mouth through a large anterior opening, but is expelled through a smaller posterior opening. This generates a hydrodynamic effect that increases filter performance and reduces drag, but also requires slower swimming. During ascent and descent balaenids swim at 1.3 - 1.6 m/s, but at 0.8 m/s during the foraging bottom phase of a dive. With their bulky bodies and large flippers and flukes, the balaenids seem to be optimized for this slow and steady swimming.

Intermittent filter feeding


Intermittently filter feeding mysticetes include the gray whale and rorquals such as the blue whale, fin whale, and humpback. They engulf a mouthful of water from which they filter the small prey using their baleen. Rorquals have several anatomical adaptations for lunge feeding, including a loose mandibular joint, a large throat pouch with ventral folds, and a soft and agile tongue. Rorquals are fast swimmers with smaller heads and have shorter and broader baleen plates. To catch prey, they widely open their large lower jaw — almost 90° — swim into a swarm gulping water and prey. They expand the capacity of their mouth by expanding the ventral grooves by pressing the tongue down.

When ram feeding, a rorqual uses the pressure from the flowing water to open its mouth, similar to a bag opening when pulled through the air. There are a number of ram feeding adaptations in rorquals, including:
 * Intermittent filter feeders ingest discrete mouthfuls of water. Prey is then filtered as the mouth closes to expel the engulfed water.  In rorquals, this is done by ram feeding.
 * a flaccid, deformable, and bag-like tongue;
 * accordion-like longitudinal throat pleats and elastic throat wall;
 * oral floor with an intermuscular fascial cleft, the cavum ventrale;
 * temporomandibular joint is lockable to prevent the mouth from opening during fast locomotion
 * the mandibular symphysis is unfused and there are
 * rostrum is flat and streamlined.

investigated the mechanisms of the balaenopterid lunge feeding: when the mouth is filled with water, the loose tongue folds into a tube and slits into a longitudinal groove in the oral floor, the cavum ventrale. This initiates the distention of the oral pouch when the distensible pleats expand and the mouth balloons like in a bullfrog or pelican. The mouth is then closed both by active contraction of the jaw adductor muscles and the elastic recoil of the pouch.

Suction filter feeding
The gray whale, in contrast, uses suction feeding: the tongue is rapidly depressed and retracted to expand the oral cavity which creates a negative pressure that forces the muddy water and prey into the mouth. Ram feeding requires forwards lunges, but the gray whale can feed while stationary.

It has been observed that the baleen rack on one side is typically more worn than the other, that the gray whale feeds by sucking its prey into one side of the mouth, and that the tongue produces the flow of water into the mouth.

Locomotion
Balaenids, such as the right whale, are positively buoyant and, consequently, have a descent characterized by active swimming, swim continuously during the foraging phase at depth, and a gliding ascent to the surface. In contrast, rorquals are negatively buoyant and their dives are characterized by a gliding descent, cycles of active lunges and passive gliding filtering during the bottom phase, and a final ascent powered by active swimming.

Migration
Rorquals are the fastest swimming baleen whales. Sei whales can reach 35 kn over short distances; minke whales and fin whales have been reported to reach speeds up to 20 kn; while blue whales can sustain 15 kn over several hours. Average speeds are considerably slower: migrating humpbacks and gray whales average 1.5 - 2.3 kn; bowheads 2.7 kn; and migrating cow-calf pairs of southern right whales 1.5 - 2.3 kn.

Gray whales migrate 5000 nmi from their breeding grounds near Baja California to their feeding grounds off Alaska, and humpbacks from the Southern Hemisphere migrate some 4500 nmi between the Antarctic Peninsula and Costa Rica in a single trip — the longest recorded migration route of any mammal. The migration pattern is not well-known for all baleen whales however. The calving grounds of blue and fin whales is unknown. In the Bering Sea, the timing of bowhead migration is dependent on the ever-changing timing of the advancing and retreating ice. Sei whale migration patterns are diffuse and non-static, while Bryde's whales live in tropical/warm temperate waters and hardly migrate at all.

Sound production
In baleen whales, the larynx is believed to be the only organ responsible for sound production. The complex system of air sacs a fatty tissues present in odontocetes is absent, as are the vocal folds found in terrestrial mammals. Exactly how mysticetes produce sound have remained a mystery until very recently.

Most laryngeal cartilages found in terrestrial mammals are also present in mysticetes except the cuneiform cartilages. A horizontally oriented U-shaped fold, located between the laryngeal inlet and the ventral laryngeal sac, is thought to be homologous to the missing vocal folds. Each side of this U-fold is supported by an extension of the arytenoid cartilage which is thought to be homologous to the vocal process. <!--
 * The mysticete larynx is largely composed of the same cartilages as the larynx of a typical terrestrial mammal, with the notable exception of the cuneiform cartilages. The mysticete’s U-fold appears to be homologous to the vocal folds of terrestrial mammals based upon similarities of orientation, attachment, cartilage movements, presence of an interarytenoid (vocal) ligament, innervation pattern, and relationships with adjacent structures.  The U-fold’s orientation in the laryngeal lumen allows it to serve as a valve to narrow or seal the passageway for airflow between the upper and lower respiratory tracts.  The U-fold is supported along each lateral wall by a ventrocaudally directed extension of the arytenoid cartilage that appears to be homologous to the vocal process.  The caudal tip of each vocal process curves medially so that the left and right sides approximate each other in the midline.  As in terrestrial mammals, the vocal process originates from the arytenoid base, which in turn articulates at a likely synovial joint to the rostral edge of the cricoid cartilage. Unlike terrestrial mammals, however, the mysticete vocal process does not traverse the laryngeal lumen perpendicular to the long axis of the trachea and larynx.
 * A thick interarytenoid ligament is contained within the U-fold and is attached between the cartilaginous terminations of the two vocal processes at the bottom of the curvature of the ‘‘U’’. This ligament appears homologous to the vocal ligament that, in terrestrial mammals, arises from the arytenoid’s vocal process and is contained within the vocal fold.

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 * U-Fold: The internal arrangement of the mysticete larynx contains a prominent U-shaped structure that borders the opening between the laryngeal lumen and the ventral laryngeal sac. The left and right extensions of this structure are joined ventrocaudally in the midline, forming a continuous, U-shape, and, therefore, will be referred to as the ‘‘U-fold.’’  The U-fold is oriented in the coronal plane, with the curve of the U directed caudally and the opening between the parallel extensions of the U directed rostrally.  When viewed from its dorsal (laryngeal luminal) surface, the U-fold appears as a raised, thick ridge of tissue that spans between the arytenoid cartilages.  Its thickness varies with different species, being thickest in Eubalaena (northern right whale).  The right and left extensions of the U-fold are each supported by cartilage bars that taper caudally to a point.  The cartilage bars are extensions of the arytenoid and likely homologous to the vocal processes of terrestrial mammals.  The curved portion of the fold (i.e., the bottom of the U) contains a ligament that spans between the caudal tips of the vocal processes.  As the ligament tethers the tips together in the midline, it causes the U-fold to take on a V-shaped appearance when the arytenoids are abducted.  The U-fold surrounds the slit-like ostium of a diverticulum (laryngeal sac) located ventral to the larynx.  When the lateral walls of the U-fold are approximated during adduction of the arytenoids, they resemble two opposed lips that seal the laryngeal sac ostium closed.  The surface of the U-fold in most specimens exhibits numerous closely packed folds separated by narrow and often deep, irregular grooves.  These grooves indicate a folded mucosa that provides flexibility of the tissue and an increased surface area.  To determine whether the U-fold is homologous to the vocal folds of terrestrial mammals, we examined it for the presence of specific traits that define mammalian vocal folds, specifically: (1) orientation, (2) cartilaginous attachments, (3) potential cartilage movements and mechanism of control, (4) presence/absence of ligaments, (5) innervation of associated musculature and mucosa, and (6) relationships to adjacent structures.

The calls and songs of mysticetes are not well understood. Many social functions have been proposed, including foraging, long distance contact, and navigation; mating, sexual advertisement, and parental care; and individual identification, but in practice any specific call is difficult to associate with a specific behaviour. In humpback and fin whales, only males are known to sing, which might suggest a mating display function, but these songs also occur during migration and on feeding grounds, so more than one function is likely.

Sound reception
Like all cetaceans, mysticetes have an ear canal that is probably not functional. The mysticete ear drum, called the "glove finger", is a thick, sack-like membrane derived from the pars flaccida of the tympanic membrane. Up to 15 cm in humpbacks, this auditory "finger" is capped by a waxy mound that increases with age. Ear ossicles are more massive in mysticetes than in odontocetes, and loosely joined, a characteristic of low frequency ears. The mysticete ear also lack the echolocation reception specialisations found in odontocetes ears. In mysticetes, the stapes are mobile the mysticete middle ear is much larger than those of odontocetes


 * In mysticetes, the tympano-periotic sutures are fixed, and extensive anterior and posterior bony flanges wedge the periotic bulla into crevices in the skull. The tight coupling of the flanges to the skull suggest both bony and soft tissue conduction mechanisms are possible in baleen whales.

The vestibular system is greatly reduced in cetaceans, who are unique in having semicircular canals that are significantly smaller than the cochlear canal. This reduction of the semicircular canals is less extreme in mysticetes than in odontocetes. The mysticete cochlear ducts are less overdeveloped than in odontocetes and the spiral ligament, stria vascularis, and support cells more closely resembles those of humans. Auditory fibre and ganglion cell counts are remarkable for all cetaceans: over 160,000 ganglion cells in fin whales. Auditory fibre diameter varies 2–40μ, mean is 5μ in mysticetes. Vestibular nerve fibre counts, on the other hand, is exceptionally low in all cetaceans.

Like in all mammalian ears, the mysticete ear is composed of three distinct parts: the outer, middle, and inner ear. Cetaceans lack a pinna or visible external ear. The inner end of the ear canal is almost filled by a waxy plug. The inner surface of this waxy plug is concave and filled by the elongated and sack-like ear drum, the so called "glove finger". The tympanic annulus, the ring-shaped structure to witch the glove finger is attached is formed by the sigmoid process and the conical process and posterior pedicles of the auditory bulla. A stout tympanic ligament connects the ear drum to the manubrium of the malleus which is connected to the sigmoid process by a the small processus gracilis.

Early descriptions
Konungs skuggsjá (The King's Mirror) is a Norwegian didactic text from around 1250. It describes, among other things, the natural marvels of Norway, including some 18 species of North Atlantic cetaceans of which 13 can be identified from the names and descriptions in the text. The English translation below by Lars Walløe is based on a 1917 translation by Laurence Marcellus Larson.
 * Minke whale: There is anther sort of whale, called fiskreki, which is perhaps the most useful of all to men; for it drives the herring and all other kinds of fish in toward the land from the ocean outside, as if appointed and sent by the Lord for this purpose. This is its duty and office as long as the fishermen keep the peace on the fishing grounds.  Its nature is also peculiar in this, that it seemingly knows how to spare both ships and men.  But when the fishermen fall to quarreling and fighting, so that blood is spilt, this whale seems able to perceive it, for it moves in between the land and the fish and chases the shaols back to the ocean, just as it earlier hade driven them in towards the men.  These whales are not more than thirty ells in length, or forty at the very largest.  They would provide good food, if men were allowed to hunt them, but no one is permitted to catch or harm them, since they are of such great and constant service to men.  [The idea that whales drive fish toward the shore was commonly accepted among fishermen in Norway as late as one hundred years ago.  This belief was the basis for strong opposition to whaling from fishermen in nothern Norway in the 1890s.  A Scandinavian word for minke whale has been sildeskipper, which can be translated as herring captain.  The prohibition of the hunting of minke whales cannot have been complied with, at least not for long, since it is known that minke whales have been caught in bays and inlets since medieval times.]
 * Fin and blue whales: Then there is a kind of whale called reydr, and this fish is the best of all for food. It is of a peacful disposition and does not bother ships, though it may swim close to them.  This fish is of great size and length; it is reported that the largest thus far caught have measured thirteen times ten ells, that is, one hundred and thrity ells by ten-count.  Because of its quiet and peacful behaviour it often falls prey to whale fishermen.  It is better for eating and smells better than any other of the other fishes that we have talked about, althought it is said to be very fat; it has no teeth.  It has been asserted, too, that if one can get some of the sperm of this whale and be perfectly sure that it came from this whale and no other, it will be found a most effective remedy for eye trouble, leprosy, ague, headache and for every other ill that afflicts mankind.  Sperm from other whales also makes good medicine, though not as good as this sort.  [Reydr means tubes or grooves, and refere to the characteristic structures foun on the ventral surfacce of the lower jaw and neck of these animals.  A later Norse version of the name of these whales is rørkval, which was borrowed in French and later in English as rorqual.]
 * Right whale: Still another kind is called slettibaka: this has no fins on the back and is about as large as the sort that we mentioned last [the sperm whale]. Searfaring men fear it very much, for it is by nature disposed to sport with ships.
 * Comment: Slettibaka means 'smooth back'.


 * Greenland whale (bowhead): Then there is that kind which is called nordhvalir. This fish grows to a length of eighty or even ninety ells and is as large around as it is long; for a rpooe that isstretched the length of one will just reach around whee it is bulkiest.  Its head is so large tht it comprises fully a third of the entire bulk.  This fish is veery clean in its choice of food; for people say that it subsists wholly on mist and rain and whatever falls into the sea from the air above.  When one is caught and its entralis are examinewd, nothing is found in its abdomen like that which is found in other fishes that take food, for the stomach is emtpy and clean.  It cannot readily open and close its mouth, for the whalebone which grows in it will stand across in the mouth when it is opened wide; and consequently whales of this type often perish because of their inability to close their mouth.  This whale rarely gives trouble to ships.  It has no teeth and is fat and good to eat.
 * Comment: The Greenland whale was called nordhval in Norway until about hundred years ago. The meaning of the word is 'the whale that lives north [of Norway]'.


 * Humpback whale: Some whales are dangerous for men to meet, while others are gentle and peaceable. One of the dangerous is called skeljung; this fish is large and very dangerous to ships.  It has the habit of striking at the vessel with its fins and of lying and floating just in front of the prow where sailes travel.  Although the ship may turn aside, the whale will continue to keep in front, so there is no choice but to sail upon it; but if a ship does sail upon it, the whale will throw the vessel and destroy all on board.  The largest of these fishes grow to a length of seventy or eighty eöös; they are good to eat.
 * Comment: The meaning of the word skeljung, is '[an animal] that carries or is covered by shells'.