Pandalus

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Pandalus
Arctic shrimp Pandalus borealis

Arctic shrimp Pandalus borealis

Systematics
Order : Decapods (decapoda)
Subordination : Pleocyemata
Partial order : Caridea
Superfamily : Pandaloidea
Family : Deep sea shrimp (Pandalidae)
Genre : Pandalus
Scientific name
Pandalus
Leach , 1814

Pandalus is a genus of shrimp fromthe deep-sea shrimp family (Pandalidae). It comprises 20 species that are distributed in the northern hemisphere in the continental shelf to partially in the deep sea. A characteristic feature of these up to 15 cm long shrimp is their protandric hermaphroditism . Some species, including the arctic shrimp ( Pandalus borealis ), are of economic interest as food and are fished.

features

Adultus

Shrimps of the genus Pandalus have a relatively long rostrum that equals or exceeds the length of the Scaphocerite . It is proven with teeth on the back and abdomen. In some species the row of teeth on the back can continue from the rostrum to about the middle of the carapace . The carapace has a distinct thorn behind each eye and two indistinct small thorns in front on the belly. The six somites of the abdomen do not have a median ridge. As with all caridea , the pleura of the second somite overlaps those of the first and third. The pleura of the first through third somits are rounded, while those of the fourth through sixth have a pointed tooth pointing backwards. The telson is longer than the sixth thus and has a tuft of hair on the back at its base. Two rows of thorns run from front to back on the telson.

The eye is wider than the eye stalk. The middle segment of the stem of the antennae has small teeth on its front edge. The stylocerite is rather short and usually rounded. The length of the antennae is no longer than twice the length of the carapace. The inner flagellum of the antennae is longer than the outer one. The scaphocerite of the antennae is relatively long and narrow. The antennae are usually longer than the total body length.

The palpus of the mandible is tripartite, relatively wide and has a prominent process at its basal joint. The first maxilliped also has a three-jointed palpus, the endopodit is two-lobed. The dactyl of the second maxilliped is wider than it is long. The third maxilliped lacks the exopodite . The first striding leg has a tiny chela , is relatively slim overall and has a row of teeth and short hairs. The second pair of striding legs is also chelated and clearly unequal, usually the left leg is longer and slimmer than the right. The three other pairs of striding legs are usually stockier. The exopodite of the uropods has tips on its lateral edge.

larva

The larvae hatch as zoea and develop over several stages to a juvenile, which morphologically resembles the adult. As a zoea, they already have complex eyes, a carapace, the telson and striding legs and no or only rudimentary pleopods. With the help of the exopodites of the striding legs, the larva swims. There is always no exopodite on the fourth and fifth stride bones in all larval stages. After usually four zoeal larvae stages, the larva becomes a megalopa when its pleopods become functional. The number of molts and the number of larval stages varies between species. For example, Pandalus borealis passes through eight to eleven larval stages, while only two of Pandalus latirostris have been described.

distribution and habitat

Species of pandalus are common in the North Atlantic and North Pacific . In the Pacific, the distribution extends from Baja California at around 30 ° N to the Bering Sea near Alaska (65 ° N), over the Chukchi Sea at around 70 ° N, the Kuril Islands and the Okhotsk and Japanese Seas to the north-eastern coast of Taiwan in the East China Sea at about 25 ° N. In the western Atlantic, the distribution ranges from the Gulf of Maine at around 44 ° N to Baffin Bay at 65–70 ° N. Over the east coast of Greenland, the distribution in the European Arctic Sea and the Barents Sea extends to around 82 ° N. The southern limit of the distribution area is probably in the Bay of Biscaya at about 45 ° N.

The vertical distribution varies within the genus. Some species can only be found in the shallow continental shelf, between 0 and 50 meters deep. Others can penetrate to depths of up to 1,380 meters, but can usually be found at depths between 200 and 400 meters. The colonized substrate also differs accordingly. In general, Pandalus species tend to live on sandy bottom. Pandalus is considered stenohalin and stenothermic and prefers low temperatures and high salt values. However, species of pandalus are also found in estuaries .

Reproduction

Pandalus species are protandric hermaphrodites, which means that they first reproduce as males and then change sex. This usually occurs one year of age after an individual mates with females in their first breeding season. Less common is the phenomenon that juveniles develop directly as females, or that males reproduce over several seasons. Males, transitional phases and females can be distinguished by the characteristics of the pleopods. In the second pair of females, the endopodit has an internal appendix that carries a small hooked process. In males there is also an appendix masculina between appendix interna and endopodit. The endopod of the first pleopod is more round-leaf-shaped in males, while that of females is more lanceolate. During the phase of sex change, the internal appendix of the first pair of pleopods degenerates and is no longer present in females.

Mating usually takes place in autumn to early winter, the larvae hatch in spring to early summer. Shortly after a female has molted, males attempt to get on her back. If they are not thrown off, the male pushes his abdomen under that of the female and places the spermatophores between the last two pairs of striding legs. Mating usually only takes a few minutes, and sometimes several males can mate a female. Then the female stands in a hunched position on the first three pairs of striding legs and, with the fourth and fifth pairs, guides the eggs from the oviductus past the spermatophores, fertilizes them and attaches them to the pleopods. This process takes up to 2.5 hours. Depending on the geographical latitude, this seasonal reproduction can vary. Females spawn in more northerly habitats usually only every two years.

Depending on the water temperature, the incubation lasts between 5 and 10 months. Larvae hatch at night. Females support the spread by swimming and moving their abdomen continuously while the larvae hatch. As a rule, all larvae hatched during one night, but in some species it can last for several days. Pandalus larvae are probably planktonic ; larvae of two species were already part of the benthos shortly after hatching .

Prey and predators

Shrimps of this genus are opportunistic omnivores and scavengers in benthos during the day . A wide variety of prey animals have been found in the stomachs of Pandalus , including many bristles , mollusks , echinoderms and other benthic crustaceans , such as Cumacea or amphipods . Pandalus shrimp swim at night and are then predators of macroplankton in the pelagic , such as copepods , hover shrimp and arrow worms .

Pandalus species are prey to some fish species. In the Atlantic, their predators are primarily cod and other cod such as Gadus merlangus or the French cod ( Trisopterus luscus ). In addition, Pandalus TYPES prey of Lycodes seminudus , Vahls Wolf fish ( Lycodes vahli ), Merluccius bilinearis , Myxine glutinosa or halibut ( Reinhardtius hippoglossoides ) and Raja radiata . In addition to fish, birds and mammals are also predators of these shrimps. a. Brünnich's Guillemot ( Uria lomvia ), seal ( Phoca vitulina ), Ringed Seal ( Phoca hispida ), bearded seal ( Erignathus barbatus ), harp seal ( Phoca groenlandica ) and Beluga ( Delphinapterus leucas ).

In the Pacific, the predators include Gadus macrocephalus , Atheresthes stomias , Hippoglossoides elassodon , Hypoglossus stenoloepis , Pacific dab ( Limanda aspera ) and Pacific pollack ( Theragra chalcogramma ).

Taxonomy

William Elford Leach described Pandalus in the Edinburgh Encyclopædia edited by David Brewster in 1814 . Type species is Pandalus montagui . Not uncommon for the taxa described by Leach, there is no reference to the meaning of the generic name.

Pandalus is possibly a paraphyletic taxon that includes a subclade with species in the genus Pandalopsis . The two genera are the only ones within the superfamily of the Pandaloidea with protandric hermaphroditism and they share many morphological details. The first two pairs of walking legs serve to differentiate between the two species. In Pandalus , the abdominal, two-dimensional expansion of the ischium of the first stride leg is only slightly pronounced and has a few teeth on the abdomen. Furthermore, the prodopus of the first stride leg is slim and conical. The second pair of striding legs is clearly unequal. In Pandalopsis, on the other hand, the abdominal, two-dimensional expansion of the ischium of the first strider leg is very broad, with hairs and without teeth. The prodopus of the first stride leg is indented on the side and the second pair of stride legs is more uniform to slightly unequal.

As distinguishing characteristics of the types of Pandalus especially the relative length of the rostrum, the number of teeth or sting on the rostrum position serve the rearmost spine on the carapace, the number of spikes on the lateral edge of the telson, the relative length of Dactylus of third and fourth stride, as well as its probation and the relative length of the merus of the third stride. In addition, the coloring and patterning can be used, which appear characteristic in living animals.

The genus Pandalus includes the following 20 species:

Individual evidence

  1. ↑ a b c d e Tomoyuki Komai: A revision of the genus Pandalus (Crustacea: Decapoda: Caridea: Pandalidae) . In: Journal of Natural History . tape 33 , no. 9 , 1999, ISSN  0022-2933 , pp. 1265-1372 , doi : 10.1080 / 002229399299914 .
  2. ↑ a b c d e f g h i j k Bo I. Bergström: The biology of Pandalus . In: Advances in Marine Biology . tape 38 , 2000, ISSN  0065-2881 , p. 55-245 , doi : 10.1016 / S0065-2881 (00) 38003-8 .
  3. ^ Charles Fransen, Sammy de Grave, Michael Türkay: Pandalus Leach, 1814. In: World Register of Marine Species. Retrieved November 3, 2017 .

Web links

Commons : Pandalus  - collection of images, videos and audio files