Little skate

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Little skate
Leucoraja erinacea.jpg
Scientific classification OOjs UI icon edit-ltr.svg
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Class: Chondrichthyes
Superorder: Batoidea
Order: Rajiformes
Family: Rajidae
Genus: Leucoraja
Species:
L. erinacea
Binomial name
Leucoraja erinacea
(Mitchill, 1825)
Leucoraja erinacea rangemap.png
Range of the little skate
Synonyms
  • Raja erinaceaMitchill, 1825

The little skate (Leucoraja erinacea) is a species of skate in the family Rajidae, found from Nova Scotia to North Carolina on sand or gravel habitats. [2] They are one of the dominant members of the demersal fish community in the northwestern Atlantic. This species is of minimal commercial importance and is mostly used as bait for lobster traps, though its wings are also marketed for food. [3] It is also important as a model organism for biological and medical research. [4]

Contents

Distribution and habitat

This skate is native to the western Atlantic Ocean, from Nova Scotia, Canada, to Cape Hatteras, North Carolina, USA. They are most abundant in the northern Mid-Atlantic Bight and the Georges Bank. Little skates prefer sandy or gravelly habitats from the shore to a depth of 90 meters (300 ft), though they have been caught as deep as 329 m (1,079 ft). They can tolerate temperatures of 1.2–21 °C (34.2–69.8 °F) and salinities of 27–33.8 ppt (though the optimum is 29–33 ppt). They do not undertake long migrations, but at the inshore parts of the species' range individuals move into shallower water during the summer and deeper water during the fall and winter. At the southern extent of the range, many also move north and south with changing temperatures. [3] [5]

Description

Dorsal view of a little skate Skate91-300.jpg
Dorsal view of a little skate

The little skate has a rounded pectoral fin disk 1.2 times as wide and as long, and a blunt snout with a central tip. The jaws contain 38–66 series of round teeth on plates, adapted for grinding food. [5] The pelvic fins are divided into two parts, with the forward lobe modified into a leg-like structure. [6] The tail is longer than the disk in juveniles and shorter in adults. Two small, closely spaced dorsal fins are located near the tip of the tail. Adults have small dermal denticles and usually no midline thorns, though there are strong spines on the dorsal surfaces of the head, shoulders, and tail. Males tend to have fewer spines than females. [5]

The coloration of the little skate ranges from grayish to uniform or variable shades of brown above, becoming lighter towards the edges of the disk, and white or gray below. Most individuals have small, round, dark spots on the back. The tail has irregular dusky blotches or a dark gray ventral surface. The little skate may be confused with unspotted individuals of the winter skate ( Leucoraja ocellata ), which has a similar shape. This species typically measures 41–51 cm (16–20 in) long, but may reach 54 cm (21 in) long. [5] Little skates grow to a larger maximum size in the northern part of their range. [3]

Biology and ecology

Little skates are more active at night and spend much of the day buried in sediment, usually near specific landscape features such as depressions excavated by other animals. [3] They employ a curious mode of locomotion, dubbed "punting" by the first scientists to document it, to move over the sea floor. The forward lobes of the pelvic fins are modified into leg-like structures called "crura" (singular "crus"), containing three flexible joints and modified skeletal and muscular elements. The little skate pushes off the substrate with both crura and then glides a short distance on its wings while repositioning the crura for the next push. The crura are also used as pivots when the skate needs to turn. Research [7] proposes that the locomotion is akin to that found in land vertebrates and thus puts the evolution of the underlying genes 20 million years earlier. It has been speculated that using the pelvic fins in this manner assists in hunting, by reducing water turbulence that might alert the prey or distort the ray's electroreception. [6]

The tail of the little skate contains an electric organ that intermittently generates a weak electric field (the electric organ discharge or EOD). The EOD lasts 70 ms and has a head-negative monophasic waveform. [2] This electric organ is thought to function in communication, and may help potential mates locate one another. [5]

Young and adult little skates are preyed upon by sharks, other skates, teleost fishes (including cod, goosefish, sea ravens, longhorn sculpins, bluefish, and summer flounder), gray seals, androck crabs ( Cancer irroratus ). Their egg-cases are preyed on by the sea urchin Strongylocentrotus droebachiensis and the whelk Buccinum undatum . [3] Known parasites of the little skate include the protozoans Caliperia brevipes , Haemogregarina delagei , and Trypanosoma rajae , the myxosporeans Chloromyxum leydigi and Leptotheca agilis , the nematode Pseudanisakis tricupola , and the copepods Eudactylina corrugata and Lernaeopodina longimana . [5]

Feeding

The diet of the little skate consists mostly of decapod crustaceans and amphipods. Polychaete worms are also an important prey item, while other invertebrates (including isopods, bivalves, squid, sea squirts, and copepods) and small benthic fishes (including sand lances, herring, cunners, and cod) are rarely taken. The importance of crustaceans in the skate's diet increases with size. This species shares its benthic habitat with the similar winter skate; the little skate focuses more on epifauna (organisms living atop the substrate) while the winter skate eats more infauna (burrowing organisms). [3] The little skate has an extremely high number of electrosensory ampullae of Lorenzini around its mouth, giving it a high degree of spatial precision when hunting for prey buried in the substrate. [8]

Reproduction

A dried-up egg case of the little skate, washed up on Long Beach, Long Island, New York, in October 2010 Little Skate eggcase 2010.jpg
A dried-up egg case of the little skate, washed up on Long Beach, Long Island, New York, in October 2010

Little skates are oviparous. Mating occurs frequently throughout the year and pregnant females can be found year-round. However, eggs are most common from October to December and from April to May, and least common from August to September and February to March. An average little skate spawns twice a year, in spring and fall, and produces a total of 10–35 eggs annually. Females deposit their egg capsules in pairs on sandy bottoms, in water no more than 27 m (89 ft) deep. The egg cases are amber-colored when first laid but become greenish-brown and leathery. Each roughly rectangular case contains a single fertilized egg and measures 44–63 mm (1.7–2.5 in) long and 30–45 mm (1.2–1.8 in) wide. There are hollow horns at each corner with sticky tendrils to secure the egg case to the substrate; the anterior horns are half as long as the case and curved inward, while the posterior horns are as long as the case and nearly straight. [3]

Eggs raised in captivity hatch in 5–6 months, while those in the wild may take up to 12 months to hatch, depending on temperature. While inside the case, the embryos have a whip-like extension on the tail believed to be used for circulating water. The newborns measure 93–102 mm (3.7–4.0 in) long and are perfectly formed miniatures of the adults. After hatching, the empty egg capsules often wash ashore and are known as "mermaid's purses". Growth is about 10 cm (3.9 in) per year for the first three years, then slows down to 5 cm (2.0 in) per year between the third and fourth years. At adolescence, males become larger than the females, and this difference persists through adulthood. Males mature at 32–43 cm (13–17 in) long and females at 36–45 cm (14–18 in) long. Very few little skates over 5 years old have been found, suggesting a high mortality rate at that age. [3] [5]

An unusual little skate specimen found off Fishers Island, New York contained a developed testis, vas deferens, and functional clasper on its left side and an adolescent ovary, shell gland, oviduct, and abortive clasper on its right. This example of hermaphroditism (a bilateral gynandromorph) is one of very few known for elasmobranch fishes. [5]

Human interactions

Euell Gibbons promoted the consumption by humans of the little skate in his cookbook Stalking the Blue-eyed Scallop (1964), noting that its wings, properly cut, could be treated like scallops. [9] Round cuts from the little skate's wings are marketed as "scallops", though due to their small size their commercial importance is limited. Little skates are also often used to bait traps, especially for lobsters and eels. [5] Skates are typically caught as bycatch in otter trawls; the little skate is not currently considered to be overfished. [3] Along with the spiny dogfish (Squalus acanthias), the little skate is often used as a model organism in biomedical research. A BAC genomic library for the little skate was completed in January 2005. [4]

Related Research Articles

<span class="mw-page-title-main">Skate (fish)</span> Family of fishes

Skates are cartilaginous fish belonging to the family Rajidae in the superorder Batoidea of rays. More than 150 species have been described, in 17 genera. Softnose skates and pygmy skates were previously treated as subfamilies of Rajidae, but are now considered as distinct families. Alternatively, the name "skate" is used to refer to the entire order of Rajiformes.

<span class="mw-page-title-main">Fish locomotion</span> Ways that fish move around

Fish locomotion is the various types of animal locomotion used by fish, principally by swimming. This is achieved in different groups of fish by a variety of mechanisms of propulsion, most often by wave-like lateral flexions of the fish's body and tail in the water, and in various specialised fish by motions of the fins. The major forms of locomotion in fish are:

<span class="mw-page-title-main">Egg case (Chondrichthyes)</span> Natural collagen casing found encompassing some aquatic lifeforms fertilized eggs

An egg case or egg capsule, often colloquially called a mermaid's purse, is the casing that surrounds the eggs of oviparous sharks, skates and chimaeras. Egg cases typically contain one embryo, except for big skate and mottled skate egg cases, which contain up to 7 embryos. Oviparity is completely absent in the superorder Squalomorphii.

<i>Bathypterois grallator</i> Species of fish

The tripod fish or tripod spiderfish, Bathypterois grallator, is a deep-sea benthic fish in the family Ipnopidae found at lower latitudes. It is now relatively well known from photographs and submersible observations, and seems to prefer to perch on the ooze using much elongated fin rays in the tail and two pelvic fins to stand, facing upstream with the pectoral fins turned forward so the outthrust projecting fin rays resemble multiple antennae, and are indeed used as tactile organs. B. grallator is hermaphroditic. At least 18 species are placed in the genus Bathypterois, several of which have similar appearance and behavior to B. grallator. B. grallator is the largest member of its genus, commonly exceeding a standard length of 30 cm (12 in) and reaching up to 43.4 cm (17.1 in).

<span class="mw-page-title-main">Rajiformes</span> Order of fishes in the superorder Batoidea

Rajiformes is one of the four orders in the superorder Batoidea, flattened cartilaginous fishes related to sharks. Rajiforms are distinguished by the presence of greatly enlarged pectoral fins, which reach as far forward as the sides of the head, with a generally flattened body. The undulatory pectoral fin motion diagnostic to this taxon is known as rajiform locomotion. The eyes and spiracles are located on the upper surface of the head and the gill slits are on the underside of the body. Most species give birth to live young, although some lay eggs enclosed in a horny capsule.

<span class="mw-page-title-main">Horn shark</span> Species of shark

The horn shark is a species of bullhead shark, in the family Heterodontidae. It is endemic to the coastal waters off the western coast of North America, from California to the Gulf of California. Young sharks are segregated spatially from the adults, with the former preferring deeper sandy flats and the latter preferring shallower rocky reefs or algal beds. A small species typically measuring 1 m (3.3 ft) in length, the horn shark can be recognized by a short, blunt head with ridges over its eyes, two high dorsal fins with large spines, and a brown or gray coloration with many small dark spots.

<span class="mw-page-title-main">Dark shyshark</span> Species of shark

The dark shyshark or pretty happy is a species of catshark, belonging to the family Scyliorhinidae, endemic to the temperate waters off southern Namibia and western South Africa. It is benthic in nature and inhabits shallow, inshore waters and favors rocky reefs and kelp forests. Growing to 60 cm (24 in) long, this small, stocky shark has a wide, flattened head with a rounded snout and a large flap of skin extending from before the nostrils to the mouth. Its dorsal coloration is extremely variable and may feature black-edged orange to blackish saddles and/or white spots on a light brown to nearly black background.

<span class="mw-page-title-main">Barndoor skate</span> Species of cartilaginous fish

The barndoor skate is a species of marine cartilaginous fish in the skate family Rajidae of the order Rajiformes. It is native to the northwestern Atlantic Ocean, and is found from the Grand Banks of Newfoundland and the southern side of the Gulf of St. Lawrence south to North Carolina. The fish is one of the largest skates found in the North Atlantic Ocean, reaching lengths up to 1.5 m (5 ft). It is carnivorous, feeding on invertebrates and other fish found near the sea floor.

<span class="mw-page-title-main">Deepsea skate</span> Species of cartilaginous fish

The deepsea skate is a species of softnose skate, in the family Arhynchobatidae, found in deep water from 362 to 2,906 m, usually on the continental slope. They are distributed from off northern Baja California around Coronado Island and Cortes Bank, north to the Bering Sea, and west to Japan. There have also been sightings north of Darwin Island within the Galapagos Marine Reserve in 2015. This was the first record of the Deepsea Skate being found in the tropical eastern Pacific Ocean. It is fairly common below 1,000 m, and is taken as bycatch in deepwater trawls and traps. The species name abyssicola comes from the Greek abyssos meaning "bottomless", and cola meaning "living at depths".

<i>Leucoraja</i> Genus of cartilaginous fishes

Leucoraja is a genus of hardnose skates in the family Rajidae, commonly known as the rough skates. They occur mostly on continental shelves and slopes in the north-western and eastern Atlantic Ocean, the Mediterranean Sea, the south-western Indian Ocean, and Australia.

<span class="mw-page-title-main">Big skate</span> Species of cartilaginous fish

The big skate is the largest species of skate in the waters off North America. They are found along the Pacific Coast from Alaska to Baja California, typically from the intertidal zone to a depth of 120 m (390 ft), and feed on benthic invertebrates and small fishes. They are unusual among skates in that their egg cases may contain up to seven eggs each. This species is one of the most commercially important skates off California and is sold for food.

<span class="mw-page-title-main">Bottlenose skate</span> Species of cartilaginous fish

The bottlenose skate, spearnose skate, or white skate is a species of skate in the family Rajidae. It is a benthic fish native to the coastal eastern Atlantic Ocean. Due to overfishing, it has been depleted or extirpated in many parts of its former range in the northeastern Atlantic and the Mediterranean Sea, and is now endangered.

<span class="mw-page-title-main">Shagreen ray</span> Species of cartilaginous fish

The shagreen ray, also known as shagreen skate or fuller's ray, is a species of skate in the family Rajidae. This ray is found in the eastern Atlantic Ocean, from Murmansk, Russia through Norway, southern Iceland, the Faroe Islands, the Celtic Sea, the northern North Sea and Skagerrak, to western Morocco and the Madeira archipelago, but not in the shallow waters off England and Wales. It is also recorded sporadically in the Mediterranean Sea.

<span class="mw-page-title-main">Mottled skate</span> Species of cartilaginous fish

The mottled skate is a species of skate in the family Rajidae. An inhabitant of shallow coastal waters, it is found in the northwestern Pacific Ocean off Korea, Japan, and China. This species grows to 1.12 m (3.7 ft) long and has a diamond-shaped pectoral fin disc with a long snout. It is characterized by a covering of prickles above and below its snout, but not elsewhere on its body, and a dark ring in the middle of each "wing".

<span class="mw-page-title-main">Clearnose skate</span> Species of cartilaginous fish

The clearnose skate is a species of cartilaginous fish in the family Rajidae. R. eglanteria is also known by other common names such as the brier skate and summer skate. Clearnose skates are easily identified by the translucent patches on either side of their snouts and their mottled dorsal surface. They are found along the Atlantic and Gulf coasts of the United States in shallow waters of the continental shelf.

<i>Raja stellulata</i> Species of cartilaginous fish

Raja stellulata, commonly known as the Pacific starry skate, rock skate, prickly skate, or starry skate, is a species of cartilaginous fish in the family Rajidae. It is found on rocky bottoms at 18–982 m depths in the Northeast and Eastern Central Pacific, from Coronado Bank in northern Baja California in Mexico to Barkley Sound in British Columbia, Canada. Females reach a maximum total length of 76.1 cm and a maximum age of 15 years, while males can be up to 71.7 cm long and live up to 14 years; the total length at birth is 15.5–22.5 cm. This skate prefers cold water with a temperature of 4.1–11.6°C.

Batoids are a superorder of cartilaginous fish consisting of skates, rays and other fish all characterized by dorsoventrally flattened bodies and large pectoral fins fused to the head. This distinctive morphology has resulted in several unique forms of locomotion. Most Batoids exhibit median paired fin swimming, utilizing their enlarged pectoral fins. Batoids that exhibit median paired fin swimming fall somewhere along a spectrum of swimming modes from mobuliform to rajiform based on the number of waves present on their fin at once. Of the four orders of Batoidae this holds truest for the Myliobatiformes (rays) and the Rajiformes (skates). The two other orders: Rhinopristiformes and Torpediniformes exhibit a greater degree of body caudal fin swimming.

<i>Raja radula</i> Ray in the genus Raja

The rough ray is a Mediterranean ray species of the Rajidae family described by Delaroche in 1809.

<span class="mw-page-title-main">Sandy ray</span> Species of cartilaginous fish

The sandy ray or sandy skate is a species of ray in the family Rajidae.

<span class="mw-page-title-main">Blonde ray</span> Species of cartilaginous fish

The blonde ray or blonde skate is a species of ray fish in the family Rajidae.

References

  1. ↑ Kulka, D.W.; Anderson, B.; Herman, K.; Derrick, D.; Pacoureau, N.; Dulvy, N.K. (2020). "Leucoraja erinacea". IUCN Red List of Threatened Species . 2020: e.T161418A124481430. doi: 10.2305/IUCN.UK.2020-3.RLTS.T161418A124481430.en . Retrieved 20 November 2021.
  2. 1 2 Froese, Rainer; Pauly, Daniel (eds.) (2009). "Leucoraja erinacea" in FishBase . March 2009 version.
  3. 1 2 3 4 5 6 7 8 9 Packer, D.B., Zetlin, C.A. and Vitaliano, J.J. (2003). Essential Fish Habitat Source Document: Little Skate, Leucoraja erinacea, Life History and Habitat Characteristics. NOAA Tech Memo NMFS NE 175. Retrieved on March 14, 2009.
  4. 1 2 Barnes, D. (2008). The Skate (Leucoraja erinacea) Genome Project Archived 2011-07-20 at the Wayback Machine . MDI Biological Laboratory. Retrieved on August 19, 2010.
  5. 1 2 3 4 5 6 7 8 9 Kittle, K. Biological Profiles: Little Skate. Florida Museum of Natural History Ichthyology Department. Retrieved on March 14, 2009.
  6. 1 2 Koester, D.M. & Spirito, C.P. (2003). "Punting: An Unusual Mode of Locomotion in the Little Skate, Leucoraja erinacea (Chondrichthyes: Rajidae)". Copeia . 2003 (3): 553–561. doi:10.1643/CG-02-153R1. S2CID   51943405.
  7. ↑ Guglielmi, Giorgia (2018-02-08). "Primitive fish's sea-floor shuffle illuminates the origins of walking". Nature. doi:10.1038/d41586-018-01700-3 . Retrieved 2018-02-10.
  8. ↑ Musick, J.A. & McMillan, B. (2003). The Shark Chronicles: A Scientist Tracks the Consummate Predator. Macmillan. ISBN   978-0-8050-7359-1.
  9. ↑ Davidson, A. (2003). North Atlantic Seafood: A Comprehensive Guide with Recipes (third ed.). Ten Speed Press. ISBN   978-1-58008-450-5.
Carly Cassella: Ancient Vertebrates May Have Had Tools For Walking Long Before They Left The Ocean. On: sciencealert, 19 March 2021. Gif and Video included.
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