| Pycnogonum litorale | |
|---|---|
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Scientific classification  | |
| Domain: | Eukaryota |
| Kingdom: | Animalia |
| Phylum: | Arthropoda |
| Subphylum: | Chelicerata |
| Class: | Pycnogonida |
| Order: | Pantopoda |
| Family: | Pycnogonidae |
| Genus: | Pycnogonum |
| Species: | P. litorale |
| Binomial name | |
| Pycnogonum litorale | |
| Synonyms [1] | |
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Pycnogonum litorale is a marine arthropod in the family Pycnogonidae, the sea spiders. It is found in the northern Atlantic Ocean, the North Sea, the English Channel and the western Mediterranean Sea.
Pycnogonum litorale has a head, a small slender prosome (thorax) and a tiny opisthosome (abdomen), the trunk being up to 1 cm (0.4 in) in length. The head bears two pairs of eyes and a long, tapering proboscis, and in males, a pair of slender curved appendages called ovigers, which are used in reproduction. The prosome consists of four segments, each bearing a pair of relatively long, robust walking legs which each have nine segments and terminate with a claw; the prosome is too small to house all the internal organs, so these extend into the limbs. The colour of this sea spider is somewhat variable, being yellowish, pale brown or reddish-brown. Males tend to be darker than females, individuals that have recently fed tend to be darker than those that have not, while those that have recently moulted tend to be pale. [2] They grow up to 25mm
In the northeastern Atlantic Ocean and the North Sea, Pycnogonum litorale occurs from Arctic Norway southwards to the western Mediterranean Sea. It is also present in the northwestern Atlantic, ranging from the Gulf of St. Lawrence southwards to New York State. It is found on the sea bed, usually on rocky substrates, where its prey are to be found. It has been recorded from the low tide mark down to depths of about 400 m (1,300 ft). [2]
Pycnogonum litorale feeds exclusively on Cnidaria, with adults feeding on sea anemones, while juveniles feed on hydroids, such as Clava multicornis . The proboscis is inserted into the prey and some body fluid is sucked out; the sea spider can be considered a parasite rather than a predator, as the food source is not killed; sea anemones that are targeted include Actinia equina , Anemonia viridis , Calliactis parasitica and Metridium dianthus . [2] The green shore crab (Carcinus maenas) feeds on sea spiders, but avoids Pycnogonum litorale because it produces two hormones (20-Hydroxyecdysone) which disrupt the crab's ecdysis (moulting). [2]
The sexes are separate in this sea spider, and reproduction occurs between spring and autumn. The process is initiated by the male clinging to the female above her head, which stimulates her to expel her eggs from orifices at the base of her legs. The male scoops these up with his ovigers, fertilises them and secures them to his underside. Here he broods them for about three weeks until they are ready to hatch. The protonymphon-type larvae have three pairs of legs, and will develop a fourth pair at metamorphosis. [2]
Sea spiders are marine arthropods of the order Pantopoda, belonging to the class Pycnogonida, hence they are also called pycnogonids. They are cosmopolitan, found in oceans around the world. The over 1,300 known species have legs ranging from 1 mm (0.04 in) to over 70 cm (2.3 ft). Most are toward the smaller end of this range in relatively shallow depths; however, they can grow to be quite large in Antarctic and deep waters.
Cancer pagurus, commonly known as the edible crab or brown crab, is a species of crab found in the North Sea, North Atlantic Ocean, and perhaps the Mediterranean Sea. It is a robust crab of a reddish-brown colour, having an oval carapace with a characteristic "pie crust" edge and black tips to the claws. A mature adult may have a carapace width up to 25 centimetres and weigh up to 3 kilograms. C. pagurus is a nocturnal predator, targeting a range of molluscs and crustaceans. It is the subject of the largest crab fishery in Western Europe, centred on the coasts of the British Isles, with more than 60,000 tonnes caught annually.
The Asilidae are the robber fly family, also called assassin flies. They are powerfully built, bristly flies with a short, stout proboscis enclosing the sharp, sucking hypopharynx. The name "robber flies" reflects their expert predatory habits; they feed mainly or exclusively on other insects and, as a rule, they wait in ambush and catch their prey in flight.
The mouthparts of arthropods have evolved into a number of forms, each adapted to a different style or mode of feeding. Most mouthparts represent modified, paired appendages, which in ancestral forms would have appeared more like legs than mouthparts. In general, arthropods have mouthparts for cutting, chewing, piercing, sucking, shredding, siphoning, and filtering. This article outlines the basic elements of four arthropod groups: insects, myriapods, crustaceans and chelicerates. Insects are used as the model, with the novel mouthparts of the other groups introduced in turn. Insects are not, however, the ancestral form of the other arthropods discussed here.
Misumena vatia is a species of crab spider with a holarctic distribution. In North America, it is called the goldenrod crab spider or flower (crab) spider, as it is commonly found hunting in goldenrod sprays and milkweed plants. They are called crab spiders because of their unique ability to walk sideways as well as forwards and backwards. Both males and females of this species progress through several molts before reaching their adult sizes, though females must molt more to reach their larger size. Females can grow up to 10 mm (0.39 in) while males are quite small, reaching 5 mm (0.20 in) at most. Misumena vatia are usually yellow or white or a pattern of these two colors. They may also present with pale green or pink instead of yellow, again, in a pattern with white. They have the ability to change between these colors based on their surroundings through the molting process. They have a complex visual system, with eight eyes, that they rely on for prey capture and for their color-changing abilities. Sometimes, if Misumena vatia consumes colored prey, the spider itself will take on that color.
Maja squinado is a species of migratory crab found in the north-east Atlantic and the Mediterranean Sea. The appearance of the European spider crab is similar to the much larger Japanese spider crab.
Notomithrax ursus, known as the hairy seaweed crab, is a spider crab of the family Majidae.
Latreilliidae is a small family of crabs. They are relatively small, long-legged crabs found on soft bottoms at depths of up 700 metres (2,300 ft) in mostly tropical and subtemperate waters around the world. Their carapace is very small and doesn’t cover the bases of their legs, which protrude from the cephalothorax in a spider-like manner. The family and its type genus are named after Pierre André Latreille. The oldest known fossils from the Latreillidae have been dated to the middle of the Cretaceous period. It comprises seven extant species.
Sea anemones are a group of predatory marine invertebrates of the order Actiniaria. Because of their colourful appearance, they are named after the Anemone, a terrestrial flowering plant. Sea anemones are classified in the phylum Cnidaria, class Anthozoa, subclass Hexacorallia. As cnidarians, sea anemones are related to corals, jellyfish, tube-dwelling anemones, and Hydra. Unlike jellyfish, sea anemones do not have a medusa stage in their life cycle.
Lybia edmondsoni is a species of small crab in the family Xanthidae and is endemic to the Hawaiian Islands. Like other members of the genus Lybia, it is commonly known as the pom-pom crab or boxer crab because of its habit of carrying a sea anemone around in each of its claws, these resembling pom-poms or boxing gloves. Its Hawaiian name is kūmimi pua, meaning "inedible flower crab". In ancient times, this animal was used by men claiming to be sorcerers.
Inachus phalangium, Leach's spider crab, is a species of crabs from the north-eastern Atlantic Ocean and Mediterranean Sea. It is up to 20.5 mm (0.81 in) wide, and is very similar to other species in the genus Inachus.
Ophiocomina nigra, commonly known as the black brittle star or black serpent star, is a species of marine invertebrate in the order Ophiurida. It occurs in the north-eastern Atlantic Ocean, the North Sea and the Mediterranean Sea.
Pycnogonidae is a family of sea spiders.
Pycnogonum is a genus of sea spiders in the family Pycnogonidae. It is the type genus of the family.
Pycnogonum stearnsi, commonly known as Stearns' sea spider, is a marine arthropod in the family Pycnogonidae. It is found on the western seaboard of North America.
The thinstripe hermit crab, Clibanarius vittatus, is a species of hermit crab in the family Diogenidae. It is found in the Caribbean Sea, the Gulf of Mexico and the western Atlantic Ocean.
Nymphon gracile is a species of sea spider first described by William Elford Leach in 1863. The species highly resembles other members of the genus Nymphon, and species identification from morphological traits alone is, therefore, a complex task.
Cerebratulus marginatus is a proboscis worm in the family Lineidae. This ribbon worm has an Arctic distribution, and in the North Atlantic Ocean ranges as far south as Cape Cod and the Mediterranean Sea while in the Pacific Ocean it extends southwards to California.
Palaeoisopus is a monotypic genus of fossil pycnogonid, known only by one species, Palaeoisopus problematicus, discovered from the Lower Devonian Hunsrück Slate of Germany. It have several characters unusual for a pycnogonid, such as swimming legs with alternating size, medially-arranged eyes, and most significantly, a long, segmented abdomen, which were highly reduced in modern counterparts.
