Kogiidae is a family comprising at least two extant species of Cetacea, the
pygmy (''Kogia breviceps)'' and
dwarf (''K. sima)'' sperm whales. As their common names suggest, they somewhat resemble
sperm whale
The sperm whale or cachalot (''Physeter macrocephalus'') is the largest of the toothed whales and the largest toothed predator. It is the only living member of the genus ''Physeter'' and one of three extant species in the sperm whale famil ...
s, with squared heads and small lower jaws, but are much smaller in size, with much shorter skulls and more notable
dorsal fin
A dorsal fin is a fin located on the back of most marine and freshwater vertebrates within various taxa of the animal kingdom. Many species of animals possessing dorsal fins are not particularly closely related to each other, though through conv ...
s than sperm whales. Kogiids are also characterized by a "false gill slit" behind their eyes.
A number of genera are extinct.
Taxonomy
There is some amount of uncertainty over if Kogiidae belongs in the
sperm whale family
Physeteroidea is a superfamily that includes three extant species of whales: the sperm whale, in the genus ''Physeter'', and the pygmy sperm whale and dwarf sperm whale, in the genus ''Kogia''. In the past, these genera have sometimes been united ...
. Research still suggests a close relationship between Kogiidae and
sperm whale
The sperm whale or cachalot (''Physeter macrocephalus'') is the largest of the toothed whales and the largest toothed predator. It is the only living member of the genus ''Physeter'' and one of three extant species in the sperm whale famil ...
s using
mitochondrial DNA
Mitochondrial DNA (mtDNA or mDNA) is the DNA located in mitochondria, cellular organelles within eukaryotic cells that convert chemical energy from food into a form that cells can use, such as adenosine triphosphate (ATP). Mitochondrial D ...
, which supports Kogiidae as part of the sperm whale family.
This relationship is supported by similarities of the anatomical structures in the read, responsible for sound production, in particular the presence of a
spermaceti organ
The spermaceti organ is an organ present in the heads of toothed whales of the family Physeteroidea, in particular the sperm whale. This organ contains a waxy liquid called spermaceti and is involved in the generation of sound.
Description
In ...
. Other
phylogenetic
In biology, phylogenetics (; from Greek φυλή/ φῦλον [] "tribe, clan, race", and wikt:γενετικός, γενετικός [] "origin, source, birth") is the study of the evolutionary history and relationships among or within groups o ...
research raises further questions over a potential relationship between kogiids and
Ziphiidae
Beaked whales (systematic name Ziphiidae) are a family of cetaceans noted as being one of the least known groups of mammals because of their deep-sea habitat and apparent low abundance. Only three or four of the 24 species are reasonably well-kn ...
.
Other questions exist regarding the high relatedness in mitochondrial DNA between ''
Platanista'' and kogiids. Fossil evidence is limited for this family, which potentially limits an understanding of their relationship to other extant cetaceans.
Researchers have proposed that ''K. sima'' may represent at least two genetically unique species, and further genetic research is needed to determine the real number of extant species of ''Kogiidae''.
![Denebola Praekogia](https://upload.wikimedia.org/wikipedia/commons/7/71/Denebola_Praekogia.jpg)
ORDER
ARTIODACTYLA
The even-toed ungulates (Artiodactyla , ) are ungulates—hoofed animals—which bear weight equally on two (an even number) of their five toes: the third and fourth. The other three toes are either present, absent, vestigial, or pointing poster ...
* Infraorder
Cetacea
Cetacea (; , ) is an infraorder of aquatic mammals that includes whales, dolphins, and porpoises. Key characteristics are their fully aquatic lifestyle, streamlined body shape, often large size and exclusively carnivorous diet. They propel them ...
** Parvorder
Odontoceti
The toothed whales (also called odontocetes, systematic name Odontoceti) are a parvorder of cetaceans that includes dolphins, porpoises, and all other whales possessing teeth, such as the beaked whales and sperm whales. Seventy-three species of ...
toothed whales
*** Superfamily
Physeteroidea
Physeteroidea is a superfamily that includes three extant species of whales: the sperm whale, in the genus ''Physeter'', and the pygmy sperm whale and dwarf sperm whale, in the genus ''Kogia''. In the past, these genera have sometimes been united ...
**** Family Kogiidae
***** Genus ''
Kogia
''Kogia'' is a genus of toothed whales within the superfamily Physeteroidea comprising two extant and two extinct species from the Neogene
*Pygmy sperm whale, ''Kogia breviceps''
*Dwarf sperm whale, ''Kogia sima''
*†'' Kogia pusilla'', Italy, ...
''
******
Pygmy sperm whale
The pygmy sperm whale (''Kogia breviceps'') is one of two extant species in the family Kogiidae in the sperm whale superfamily. They are not often sighted at sea, and most of what is known about them comes from the examination of stranded spec ...
, ''K. breviceps''
******
Dwarf sperm whale
The dwarf sperm whale (''Kogia sima'') is a sperm whale that inhabits temperate and tropical oceans worldwide, in particular continental shelves and slopes. It was first described by biologist Richard Owen in 1866, based on illustrations by n ...
, ''K. sima''
******''
Kogia pusilla
''Kogia pusilla'' is an extinct species of sperm whale from the Middle Pliocene of Italy related to the modern day dwarf sperm whale (''K. sima'') and pygmy sperm whale (''K. breviceps''). It is known from a single skull discovered in 1877, a ...
'' †
***** Genus ''
Aprixokogia'' †
****** ''
Aprixokogia kelloggi''
***** Genus ''
Kogiopsis''†
****** ''
Kogiopsis floridana''
***** Genus ''
Koristocetus''†
***** Genus ''
Nanokogia''†
****** ''
Nanokogia isthmia''
***** Genus ''
Pliokogia'' †
****** ''
Pliokogia apenninica''
***** Genus ''
Praekogia
''Praekogia'' is an extinct genus of cetacean
Cetacea (; , ) is an infraorder of aquatic mammals that includes whales, dolphins, and porpoises. Key characteristics are their fully aquatic lifestyle, streamlined body shape, often large size a ...
''†
****** ''
Praekogia cedrosensis''
***** Genus ''
Scaphokogia''†
****** ''
Scaphokogia cochlearis''
***** Genus ''
Thalassocetus''†
****** ''
Thalassocetus antwerpiensis''
Biology
Kogiid skulls are characterized by a very short
rostrum
Rostrum may refer to:
* Any kind of a platform for a speaker:
**dais
**pulpit
* Rostrum (anatomy), a beak, or anatomical structure resembling a beak, as in the mouthparts of many sucking insects
* Rostrum (ship), a form of bow on naval ships
* Ros ...
, the smallest among extant cetaceans, as well as high levels of asymmetry, which is expected among
odontocetes
The toothed whales (also called odontocetes, systematic name Odontoceti) are a parvorder of cetaceans that includes dolphins, porpoises, and all other whales possessing teeth, such as the beaked whales and sperm whales. Seventy-three species of t ...
.
Kogiid skulls have the most blunt
mandible
In anatomy, the mandible, lower jaw or jawbone is the largest, strongest and lowest bone in the human facial skeleton. It forms the lower jaw and holds the lower tooth, teeth in place. The mandible sits beneath the maxilla. It is the only movabl ...
among extant cetaceans as well. Extant kogiidae also show relatively high
encephalization quotient
Encephalization quotient (EQ), encephalization level (EL), or just encephalization is a relative brain size measure that is defined as the ratio between observed to predicted brain mass for an animal of a given size, based on nonlinear regressi ...
, the ratio between observed brain size and expected brain size. The pygmy sperm whale has an EQ of 1.78, while the dwarf sperm whale's EQ is 1.63.
Kogiidae do possess
spermaceti
Spermaceti is a waxy substance found in the head cavities of the sperm whale (and, in smaller quantities, in the oils of other whales). Spermaceti is created in the spermaceti organ inside the whale's head. This organ may contain as much as of ...
in their head like sperm whales. However, kogiid spermaceti is unique as the whales are able to control its temperature.
Kogiidae are also
homodont
In anatomy, a heterodont (from Greek, meaning 'different teeth') is an animal which possesses more than a single tooth morphology.
In vertebrates, heterodont pertains to animals where teeth are differentiated into different forms. For example ...
s, showing teeth all of the same size and shape.
Kogiidae possess a unique system of organs to produce sound, including a
bagpipe
Bagpipes are a woodwind instrument using enclosed reeds fed from a constant reservoir of air in the form of a bag. The Great Highland bagpipes are well known, but people have played bagpipes for centuries throughout large parts of Europe, Nor ...
-like structure to produce sound and an amplifying horn.
Kogiidae have a modified colon which works as an "
ink sac
An ink sac is an anatomical feature that is found in many cephalopod mollusks used to produce the defensive cephalopod ink. With the exception of nocturnal and very deep water cephalopods, all Coleoidea (squid, octopus and cuttlefish) which dwell ...
", storing liquid red feces.
They are able to release over three gallons of this fecal "ink" to confuse or discourage predators.
Ecology
Range
Kogiidae are believed to be
cosmopolitan species
In biogeography, cosmopolitan distribution is the term for the range of a taxon that extends across all or most of the world in appropriate habitats. Such a taxon, usually a species, is said to exhibit cosmopolitanism or cosmopolitism. The extre ...
, inhabiting all oceans except polar waters, remaining between the 50° latitude lines.
Two fossilized species of ''Kogia sp.'' were shown to exhibit
sympatry
In biology, two related species or populations are considered sympatric when they exist in the same geographic area and thus frequently encounter one another. An initially interbreeding population that splits into two or more distinct species sh ...
, similar to the two modern members of ''Kogia'', which researchers suggested shows that this behavior has been part of ''Kogiidae'' for at least 3 million years.
Behavior and feeding
Extant kogiids travel in small groups and rarely surface, potentially to avoid predators like
orca
The orca or killer whale (''Orcinus orca'') is a toothed whale belonging to the oceanic dolphin family, of which it is the largest member. It is the only Extant taxon, extant species in the genus ''Orcinus'' and is recognizable by its black ...
s.
Kogiidae are deep diving whales, believed to dive up to depths of 500 m.
Kogiids feed using a technique known as suction feeding, and their diet primarily consists of squid.
Pygmy sperm whales are able to eat larger prey than dwarf sperm whales, although their diet as a whole is relatively similar.
They have also been observed using
echolocation to find their prey, and their hearing places them in the "Very High Frequency" group of cetaceans that can hear well above 100 kHz.
Human threats
Most observations of Kogia have come from individuals tangled in fishing line or stranded individuals.
There is a commercial fishery for ''K. breviceps'' in parts of southeast Asia and the
Lesser Antilles
The Lesser Antilles ( es, link=no, Antillas Menores; french: link=no, Petites Antilles; pap, Antias Menor; nl, Kleine Antillen) are a group of islands in the Caribbean Sea. Most of them are part of a long, partially volcanic island arc betwe ...
.
Both species of extant kogiidae have also been observed stranded with plastics blocking their intestines.
References
{{Taxonbar, from=Q1965630
Animals that use echolocation
Taxa named by Theodore Gill
Mammal families