Sandworms

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Sandworms
Branchiomaldane and Arenicola. Catalog of the Chaetopoda in the British Museum (Natural History), 1912

Branchiomaldane and Arenicola . Catalog of the Chaetopoda in the British Museum (Natural History), 1912

Systematics
Empire : Animals (Animalia)
Trunk : Annelids (Annelida)
Class : Polychaete (Polychaeta)
Subclass : Sedentaria
Order : Scolecida
Family : Sandworms
Scientific name
Arenicolidae
Johnston , 1835

The sandworms (Arenicolidae) are a family of often large and conspicuous polychaeta that can be found burrowing in the soft sediment of oceans worldwide.

features

The multi-bristle of the family Arenicolidae have an elongated and soft, often swollen, clearly segmented body with a small blunt head without appendages and a curled epidermis, which in adult animals can be up to 40 cm long. The gills sit on the middle segments of the notopodia and are mostly branched tufts, in the genus Branchiomaldane simple, pointed body appendages. The prostomium of the Arenicolidae is small and round or cone-shaped, the peristomium typically reduced to lips that surround the mouth, in some species, including the genus Branchiomaldane , to a ring around the mouth. While antennae and palps as well as tentacle cirrus are missing, the two nuchal organs are formed as dorsolateral pits on the prostomium. The longitudinal muscles of the skin muscle tube are arranged in four distinct bundles. The first segment is similar to the other segments, but in adults it does not have parapodia that only begin with the second segment. The distal cut, cylindrical or conical Notopodien are short, the neuro stages as torus formed. Dorsal and ventral cirrus organs are absent, as are epidermal papillae, pygidial papillae, aciculae, lateral organs and probably also dorsal cirrus organs. The bristles are capillary-shaped or distally toothed, unprotected hooks of the neuropodia.

The simple, axial, sac-shaped pharynx is covered on the outside with large papillae. The animals have a throat membrane and the intestine is a straight tube. Only the foremost segments have mixonephridia , of which the first pair is only used for excretion, the others at the same time as an exit for the gametes . The blood vessel system of the Arenicolidae is closed. Some species, including the lugworm , have a central heart as adults , but this is not homologous to the heart of other polychaete families. To bind the oxygen , hemoglobin dissolved in the plasma serves as a blood pigment with a very high affinity for oxygen, which also enables survival in an oxygen-poor environment. In contrast, there is no hemoglobin in the Coelom fluid .

Females and males are the same size in the Arenicolidae. The mature gametes are released to the outside via the mixonephridia, where fertilization takes place in the seawater. The development takes place via benthic larvae, which live on yolk reserves until metamorphosis .

The Arenicolidae feed on detritus and microorganisms by taking up substrate particles with their everted pharynx and digesting adherent detritus and microorganisms - including bacteria , ciliates , flagellates and nematodes - in the intestine.

Some sample styles

In the northeastern Atlantic Ocean is Wattwurm ( Arenicola marina ) is very widespread.

Genera

The family Arenicolidae is divided into 8 genera :

literature

  • Stanley J. Edmonds: Fauna of Australia, Volume 4A. Polychaetes & Allies. The Southern Synthesis 4. Commonwealth of Australia, 2000. Class Polychaeta. Pp. 81-87, Family Arenicolidae.

Web links

Commons : Arenicolidae  - Collection of images, videos and audio files

Individual evidence

  1. ^ Arenicolidae Johnston, 1835. WoRMS , 2018. Retrieved June 11, 2018.