Download Tiburones gato y parientes (familia Scyliorhinidae)

Tiburones gato y parientes (familia
Scyliorhinidae)
N omb res comu n es: Pejegatos (Español) / Cat sharks (Inglés)
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General description 1,2
The family Scyliorhinidae is the largest shark family, with at least 15 genera and over 100 species. Their
common name, catsharks, likely derives from their elongated, cat-like eyes, although their scientific
name is based on the Greek words, “Scylla,” meaning “a shark,” and “rhinos,” meaning “nose.” Some
members of Scyliorhinidae are also commonly known as dogfish. Members of this family tend to be
small, usually less than 1 m long, and are harmless to humans. Most catsharks live in seas above the
upper continental slope, a location that makes it difficult to observe these sharks and collect specimens.
Therefore, much information about catsharks remains to be discovered.
Distribution 3,4
Distribution: temperate and tropical seas. Usually elongated, catlike eyes with nictitating eyelids. Lower
eyelid usually with longitudinal fold. Gill openings 5, the fifth over origin of pectoral fin. Two small,
spineless dorsal fins. One of the largest family of sharks, occurring from the intertidal zone to the edges
of the continental and insular shelves and down the slopes to depths greater than 2000 m. Spawns
large eggs in tough egg-cases with tendrils. Some species are ovoviviparous. Feed mainly on
invertebrates and small fishes.
Morphology 1,2
Catsharks (family Scyliorhinidae) are small sharks. Most are less than 80 cm long, but some, i.e.
Scyliorhinus cervigoni, attain a length of at least 1.6 m. The bodies of catsharks are fusiform (cylindrical,
tapering at the ends) to slightly depressed. The snout may be short or elongated, and sometimes forms
a bell shape when seen from above or below. This family has elongated, catlike eyes situated high on
the sides of the head. They possess rudimentary nictitating lower eyelids. These membranes,
essentially a third eyelid, can cover the exposed portion of the eye, since, as in all sharks, the upper and
lower eyelids of catsharks cannot completely cover the eyeball. Catsharks have moderately large
spiracles, or respiratory openings, and five pairs of gill slits. Teeth are small and multicuspid, with 40 to
111 rows of teeth in each jaw. In some cases the rear teeth are comblike. In various species of catshark
from at least seven genera, females and adult males have different tooth shape. This is called sexual
heterodonty, and it occurs most strongly in smaller species of catshark. Adult males in these cases tend
to have much larger teeth than females or immature males, and larger, higher, and differently-shaped
cusps. One researcher suggests that the modifications of the teeth in adult males may contribute to
their ability to grasp a female during courtship. In all catsharks, the base of the first dorsal fin is
opposite or behind the base of the first pelvic fin. There are two dorsal fins, both without spines. Anal
and caudal fins are also present. Catsharks may be a plain color ranging from grayish to dark brown, or
may have color patterns of blotches, spots, or saddles. Like other sharks, catsharks are covered with
placoid scales. All sharks have a valvular intestine, and in catsharks the valve has a conicospiral shape,
with between five and 21 turns.
Oth er Ph ysi cal Featu res: heterothermic ; bilateral symmetry
Sexu al Di morp h i sm: sexes alike; sexes shaped differently
Habitat 1,2
Catsharks most frequently live near the bottom, ranging from shallow intertidal zones to depths of more
than 2000 m. Many occur along continental and insular slopes, and this deepwater habitat makes many
catsharks difficult to observe and collect. Near Australia, catsharks have been observed inhabiting
ledges and caves, seagrass or kelp beds, coastal reefs, and both sandy and rocky bottoms. Some
catsharks (members of Parmaturus and probably Cephalurus) are able to live in benthic habitats
tolerable to few other fishes: enlarged branchial (gill) regions enable them to survive very low oxygen
levels, high temperatures, and high salinity.
Hab i tat R egi on s: temperate ; tropical ; saltwater or marine
Aq u ati c Bi omes: benthic ; coastal
Oth er Hab i tat Featu res: intertidal or littoral
Trophic strategy 1,2
Small fish and invertebrates make up the diet of most catsharks. Some swellsharks, for example
Cephaloscyllium ventriosum ( see image) hide among squid eggs; they wait for the parent squid to
become accustomed to a shark among its eggs, then devour the squid when it returns.
Pri mary Di et: carnivore (Piscivore , Molluscivore , Scavenger )
Associations 1,2
Catsharks occur around the globe in warm temperate seas, and therefore are a consistent predator on
populations of squid, crustaceans, cephalopods, and small fishes. Catsharks, especially smaller
specimens, provide food for other families of sharks and other large fishes.
Behaviour 1,2
Catsharks, like other elasmobranchs , have a high sensitivity to electric fields created by the movement
of water, of other fishes, and even the movement of the earth. In experiments Scyliorhinus canicula, for
example, demonstrated sensitivity to extremely low voltage gradients. In principle, sharks can use this
sense to navigate according to the earth’s magnetic fields, and to detect prey. The special receptors
used for this mode of perception are called the ampullae of Lorenzini, distributed around the shark’s
head. Catsharks, like all other fishes, sense their environment hydrodynamically through the lateral line,
a series of pores connecting a complex internal canal system with the outside water. They also possess,
like other elasmobranchs , pit organs that lie between the bases of scales and add to information
provided by the lateral line. Members of the family Scyliorhinidae are raptorial predators, and therefore
have keen senses of hearing, taste, and smell that help them sense and find food sources. Experiments
on species of Scyliorhinidae suggest that the pineal gland in the brain may serve as a keen light sensor
that cues the fish’s behavior to periodic changes in light.
Commu n i cati on Ch an n el s: visual ; tactile ; acoustic ; chemical ; electric
Percep ti on Ch an n el s: visual ; tactile ; acoustic ; chemical ; electric ; magnetic
Life cycle 1,2
Catsharks begin life inside spindle-shaped egg cases known to beachcombers as “mermaids’ purses.” In
most cases the embryo develops, inside its egg case, within the mother’s uterus until it is almost ready
to hatch. Then the mother deposits the egg on the sea bottom or other surface. Long, curling tendrils
extend from each of the four corners of an egg case to help secure it to the substrate. Slits in the
tendrils allow water to flow through the egg case. The young catshark continues to develop until it
hatches, looking like a miniature adult. Hatching time ranges from less than a month to more than a
year. There is no larval stage. In about 10% of catsharks, from the genera Galeus, Halaelurus, and
Cephalurus, the embryo completes its entire development inside the mother and is born directly into
the sea. Male carcharhinids, including catsharks, have reached sexual maturity when their clasper
(male organ for internally fertilizing a female) cartilages have become calcified and rigid, rather than
small, soft, and flexible as in immature males. The presence of large ovaries with follicles marks
adulthood in females.
Life expectancy 1,2
No specific information was found regarding lifespan in Scyliorhinidae. Sharks in general, however,
tend to mature slowly and be long-lived.
Reproduction 1,2
Only a few species of elasmobranch (subclass including all sharks and rays) fishes have been observed
during courtship and mating. However, sharks have a system that involves internal fertilization, and
elasmobranch fishes have relatively complex endocrine (hormonal) systems. Based on knowledge of
other vertebrates with similar systems, it is likely that females signal to males through chemical or
behavioral cues to indicate when their hormonal state is appropriate for mating. Some female sharks
have been observed behaving in specific ways prior to mating, followed by passive behavior during
copulation that permits the biting and grasping behavior of the male. It is likely that some catsharks
participate in this pattern. Mating in some sharks lasts for 15 to 20 minutes, but specific information
regarding length of copulation in catsharks was not found. In order to inseminate the female, the male
inserts into her one of his two claspers, organs that are grooved extensions of the rear bases of the
pelvic fins. In most catsharks the clasper groove is covered by soft tissue, forming a tunnel down which
semen travels into the female. In at least one species of catshark, Scyliorhinus canicula , the female is
able to store sperm for delayed insemination.
At least 90% of known catsharks are oviparous, meaning they lay eggs. Many of these catsharks produce
eggs all year, with seasonal increases in the number of females laying eggs. Most catsharks have a
system called single oviparity, in which an egg develops inside each oviduct and is deposited outside
the female, remaining attached to the substrate until it hatches. Hatching time may be less than a
month or nearly a year. At least one species of Galeus and four species of Halaelurus have multiple
oviparity. In this case several eggs develop in each oviduct, and hatching time tends to be shorter (23 to
36 days in Halaelurus lineatus). Catshark egg cases, made from a keratin-like collagen, tend to be
rectangular in shape, with rounded sides and narrow ends. Tendrils from each corner help anchor the
egg to the substrate. A special gland in the female, unique to elasmobranchs and known as the
oviducal, nidamental, or shell gland, produces the egg case.
Although egg cases provide a tough protective shield, developing embryos inside them are still
vulnerable to predation. Some sharks have evolved a system called ovoviviparity or aplacental viviparity
to protect their young until a later stage of development. It is estimated that oviparity evolved into
viviparity at least 18 times within Chondrichthyes (class that includes sharks). Ovoviviparous sharks give
birth to live young, and a few members of Scyliorhinidae (from the genera Galeus, Halaelurus, and
Cephalurus) fall into this category. In this system, the egg is retained inside the uterus, and the young
catshark develops there until it is born directly into the sea and can swim away like a miniature adult.
Only one young at a time develops within the uterus. Some ovoviviparous sharks secrete a uterine fluid
that supplements the nutrition the developing young receives from the egg. No information was found
to verify whether or not ovoviviparous catsharks share this characteristic.
K ey R ep rod u cti ve Featu res: iteroparous ; seasonal breeding ; year-round breeding ;
gonochoric/gonochoristic/dioecious (sexes separate); sexual ; fertilization (Internal ); ovoviviparous ;
oviparous
No parental care has been observed in catsharks. Female catsharks contribute extensively to the
survival of offspring by protecting them internally during development and even producing secretions
that provide nutrition.
Paren tal In vestmen t: pre-fertilization (Provisioning, Protecting: Female); pre-hatching/birth
(Provisioning: Female, Protecting: Female)
Statistics of barcoding coverage 5
Barcode of Life Data Systems (BOLD) Stats
Specimen Records:1290
Specimens with Sequences:1033
Specimens with Barcodes:768
Species:104
Species With Barcodes:95
Public Records:331
Public Species:52
Public BINs:51
Conservation status 1,2
Sharks in general are vulnerable to overfishing. They grow and mature slowly, and the size of the adult
population closely determines the number of young produced, due to their “slow” reproductive strategy
of investing a great deal of energy in relatively few young over a lifetime. As of 2001, one species of
catshark was listed as vulnerable (facing a high risk of extinction in the wild), and eight species of
catshark were listed as near threatened (approaching vulnerable status). Twenty species were listed as
data deficient, meaning that not enough information has been collected to assess whether or not the
species is threatened. These species may be threatened, however, especially if their geographic range
is limited and few specimens have been found for data collection.
Uses 1,2
Catsharks are harmless to humans. One species, Cephaloscyllium laticeps , apparently can be a
nuisance to lobster fishermen in parts of Australia when it enters lobster traps.
References
1. Weinheimer, M. 2004. "Scyliorhinidae" (On-line), Animal Diversity Web. Accessed April 27, 2013 at
http://animaldiversity.ummz.umich.edu/site/accounts/information/Scyliorhinidae.html
2. © The Regents of the University of Michigan and its licensors, some rights reserved
3. MASDEA (1997).
4. © WoRMS for SMEBD, some rights reserved
5. © Barcode of Life Data Systems, some rights reserved