The largest known population of coelacanths (Latimeria chalumnae) lives along the coasts of the Comoros Islands. Small breeding groups have also been found along the African coast from Kenya to South Africa. (Fricke, et al., 2011; Hissmann, et al., 2006)
During daylight hours, coelacanths gather in caves roughly 100 to 200 m below the water surface where temperatures range from 16˚ to 22˚C. At night, when they hunt, coelacanths travel to depths ranging from 70 to 700 m, depending on prey abundance and ambient temperature. (Fricke, et al., 2011; Hissmann, et al., 2006)
Latimeria chalumnae is sometimes referred to as a living fossil due to their morphology remaining static over hundreds of millions of years. Also, while they have many characteristics in common with other Osteichthyes (such as their bony skeleton and diphycercal tail), some features are usually found in Chondricthyes (their reliance on fat for buoyancy and ovoviviparity) while others appear to be derived specializations (a vestigial lung and intracranial joint).
Coelacanths can grow up to 2 m in length. Their bodies are covered in blue scales, which turn brown after death, with a white speckling that is unique to each individual. Their seven fins have fleshy lobes and they move their two paired sets of fins (pectoral and pelvic) in a diagonally synchronous manner like a four-limbed terrestrial animal.
Unlike all other vertebrates, coelacanths possess an intracranial joint and an associated basicranial muscle. The purpose of this structure is disputed, with some experts arguing that it assists with suction feeding, while others suggest that it increases bite force. Another dissimilarity is their notochord, which in coelacanths is a hollow tube filled with fluid.
Coelacanths have a fatty organ that serves the same purpose as a swim bladder. It was recently discovered that, within this fatty organ, a vestigial lung can be found that is surrounded by small hard plates. It is believed that these plates were involved in lung volume regulation in an ancestral species, but have become rudimentary in extant coelacanths.
Females are larger in size, and have higher thickness ratios and metabolic rates than males. Average mass of adult females is 82.1 kg, and average length is 170 cm, for males average mass is 37.2 kg, length 125 cm. Basal metabolic rate for adult females is about 7400 cubic cm of oxygen per hour, for males 4100. (Balon, 2007; Cupello, et al., 2015; Dutel, et al., 2015; Fricke and Hissmann, 2000; Fricke, et al., 2011; Hissmann, et al., 2006)
Coelacanths are ovoviviparous, with females bearing their offspring internally for 13 months to three years. Embryo development is supported by yolk provisioned by the female. A gestation period of 13 months was originally determined by Hureau and Ozouf (1977). Once it was established that coelacanths are ovoviviparous, Froese and Palomares (2000) argued that the von Bertalanffy growth function can apply to coelacanth embryos, and found their gestation period to be roughly 3 years, with supporting evidence based on scale rings.
Eggs have been measured to be 1 to 9 cm in diameter and weight 100 to 350 g. Near term juveniles can reach 35 cm in length and weigh up to 500 g. Few juvenile specimens have ever been caught following birth, and none have been witnessed in the presence of adults. (Balon, 2007; Froese and Palomares, 2000; Lampert, et al., 2013)
It is likely that fertilization is internal for coelacanths and it has been suggested that males possess a modified cloaca for this purpose due to the absence of a copulatory organ. Genetic studies have found evidence of single-male paternity but direct observations of mating behavior are lacking. (Balon, 2007; Fricke, et al., 2011; Lampert, et al., 2013)
There is little information available for the life history of the species. Gravid females have been found bearing between five and 26 fully developed young at a time. However, the number of eggs at earlier developmental stages can be 60 or more which suggests a decline of brood size during gestation. The long gestation time suggests that females may reproduce at intervals of two or more years. It has been estimated that reproductive maturity in females is achieved after more than 20 years. (Balon, 2007; Lampert, et al., 2013)
There is no known investment by males in raising young. There is a large energy investment by females in the bearing and nourishment of live young during the lengthy gestation period. (Fricke, et al., 2011; Lampert, et al., 2013)
The lifespan of coelacanths is not known for certain. It is certainly at least 22 years, based on repeated observation of the same adult individuals over that time period. Froese and Palomares (2000) determined the expected lifespan of coelacanths to be 48 years using the equation Ap = t0 – ln(1 – p)/K.
Fricke et al. (2011) proposed that coelacanths could live longer than 100 years using an alternate method, and pointed out that there are other deep-water fish species with similar lifespans. (Fricke, et al., 2011; Froese and Palomares, 2000)
Coelacanths have shown a tendency to aggregate in their daytime cave habitats. However, there has been no observation of social interactions of any kind among coelacanths in their aggregations. Any physical contact appears to be accidental and non-aggressive. No pattern has been discerned in cave selection in coelacanths beyond temperature and depth requirements. Individual coelacanths have been observed staying in different caves from night to night, but also will sporadically revisit the same cave over many years.
At night, they drift hunt individually. From the few observations made so far of their feeding, it appears that coelacanths do not pursue prey, but will simply snap up any prey of suitable size which passes within 20 cm of the front of their mouths. During the course of their nightly hunting, coelacanths may range over several kilometers.
Because of their specialized fin anatomy, coelacanths possess remarkable agility in the water. They can swim in any direction, and have been witnessed swimming inverted, or in a vertical, face-down posture. (Fricke and Hissmann, 2000; Fricke, et al., 2011; Hissmann, et al., 2006)
The definitive home range of coelacanths is not known. Individuals tagged with a tracking device have traveled between 2 and 8 km in a day. (Fricke and Hissmann, 2000)
Coelacanths have a rostral organ in their snouts that is believed to have an electroperceptive function.
They also possess color vision that is strongly adapted to a deep water environment. Most visible light at that depth has a wavelength around 480 nm, and the visual pigments of coelacanths are most sensitive to wavelengths of 478 nm and 485 nm, which is a blue shift of roughly 20 nm relative to corresponding orthologous pigments. (Bernis and Hetherington, 1982; Yokoyama, et al., 1999)
Coelacanths are opportunistic in their feeding. Some of their known prey species are fish that include: Coranthus polyacanthus, Beryx splendens, Lucigadus ori, and Brotula multibarbata.
Their intracranial joint and associated basicranial muscle likely play an important but unresolved role in feeding. (Balon, 2007; Fricke and Hissmann, 2000)
Humans are the only known predator of coelacanths. They are considered unfit for eating, and are usually caught by accident by fishermen angling for oilfish (Ruvettus pretiosus).
The scale color patterns of coelacanths resemble the walls of the caves in the Comoros where they spend their daytime hours and may play a role in crypsis. (Fricke and Hissmann, 1990; Hissmann, et al., 1998; Plante, et al., 1998)
Aside from their role as large predators, nothing is known about the ecosystem role of coelacanths. (Fricke, et al., 2011; Hissmann, et al., 2006)
There are no known positive effects of coelacanths on humans.
There are no known negative effects of coelacanths on humans.
The L. chalumnae population is in decline. Their total number is believed to be in the hundreds, and it takes years for a female to reach sexual maturity.
The greatest source of coelacanth mortality appears to be as bycatch from gill nets or near-shore, deep water fishing.
Fricke (1997) discusses black-market trade of coelacanths. He dismisses as rumor the widely reported use of coelacanth oil in eastern medicine for longevity. However, despite their protected status, Fricke notes that there does exist some low-value, illegal local trade in dead coelacanths, and that the amount private organizations would be willing to pay for a live coelacanth could exceed seven figures.
Because the habitat tolerance range of L. chalumnae is still poorly defined, major organizations involved in its conservation are emphasizing the importance of a greater understanding of their environmental requirements. (Fricke, 1997; Plante, et al., 1998; Ribbink and Roberts, 2006)
Nicholas White (author), Indiana University - Purdue University Fort Wayne, Mark Jordan (editor), Indiana University-Purdue University Fort Wayne.
having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.
an animal that mainly eats meat
the nearshore aquatic habitats near a coast, or shoreline.
having markings, coloration, shapes, or other features that cause an animal to be camouflaged in its natural environment; being difficult to see or otherwise detect.
animals which must use heat acquired from the environment and behavioral adaptations to regulate body temperature
uses electric signals to communicate
union of egg and spermatozoan
having a body temperature that fluctuates with that of the immediate environment; having no mechanism or a poorly developed mechanism for regulating internal body temperature.
fertilization takes place within the female's body
offspring are produced in more than one group (litters, clutches, etc.) and across multiple seasons (or other periods hospitable to reproduction). Iteroparous animals must, by definition, survive over multiple seasons (or periodic condition changes).
eats mollusks, members of Phylum Mollusca
Having one mate at a time.
having the capacity to move from one place to another.
specialized for swimming
the area in which the animal is naturally found, the region in which it is endemic.
active during the night
generally wanders from place to place, usually within a well-defined range.
reproduction in which eggs develop within the maternal body without additional nourishment from the parent and hatch within the parent or immediately after laying.
An aquatic biome consisting of the open ocean, far from land, does not include sea bottom (benthic zone).
an animal that mainly eats fish
mainly lives in oceans, seas, or other bodies of salt water.
reproduction that includes combining the genetic contribution of two individuals, a male and a female
the region of the earth that surrounds the equator, from 23.5 degrees north to 23.5 degrees south.
movements of a hard surface that are produced by animals as signals to others
uses sight to communicate
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