Protodrilida

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Protodrilida
Systematics
without rank: Bilateria
without rank: Primordial mouths (protostomia)
Over trunk : Lophotrochozoa (Lophotrochozoa)
Trunk : Annelids (Annelida)
Class : Polychaete (Polychaeta)
Order : Protodrilida
Scientific name
Protodrilida
Pettibone , 1982

Protodrilida is very small, the name of an order in sand gap system of living and from bacteria nourishing polychaete (Polychaeta), which are found in oceans worldwide.

features

The Protodrilida usually have a transparent to whitish, sometimes yellow, orange or green body, which is 1.6 to 30 mm long depending on the sub-taxon and has up to 200 segments. The head consists of a small, triangular or round prostomium and a peristomium that forms a complete ring around the mouth. All types of Saccocirrus ( Saccocirridae ) and some types of Protodrilus ( Protodrilidae ) have simple, two-celled, pigmented eyes on the prostomium , but they are absent in all other known species of the taxon. In all Protodrilida there is a pair of nuchal organs at the base of the prostomium . The animals mostly have rows of eyelashes on their belly which are used for locomotion, but their size and shape vary greatly. All species have a pair of very flexible palps on the prostomium (also known as “ tentacles ”) with a sensory function and without the eyelash groove typical of the Canalipalpata . With the Protodrilidae and the Saccocirridae, but not the Protodriloididae, a possibly coelomatic , hydroskeletal inner channel runs through each of the palps , and both unite in the prostomium. All Protodrilida have two, sometimes three lobes with adhesive glands on their pygidium, with which the animals attach themselves to sediment grains. Most Protodrilidae - but not some Saccocirridae - have a ventrally located pharynx , of which it is not known whether it can be everted. In Astomus taenioides ( Parenterodrilus taenioides ) the digestive system is reduced, but there is also a lack of symbiotic bacteria such as those found in comparable cases such as beard worms . A simple, closed blood vessel system with colorless blood is present, but a central heart is missing. The nephridia are protonephridia in the Protodrilidae and metanephridia in the Saccocirridae.

habitat

The Protodrilida live in the sand gap system in comparatively clean, coarse sediments with little detritus in the intertidal zone or below. Most species graze the bacteria that live on the surface of the grains of sand.

The animals move with the help of their belly-side eyelash strips and, with the help of sticky substances from glands, are able to adhere to a grain of sand, especially on the two lobes on the pygidium. Astomus taenioides in the coral sands of Moorea ( French Polynesia ), which has only a rudimentary intestine, feeds on dissolved organic substances that are absorbed via enlarged side lobes.

Development cycle

As far as is known, all Protodrilida are separate sexes. Mating with the penis and vagina has been observed in the Saccocirridae . In the Protodrilidae, mating takes place with spermatophores , so that internal fertilization also occurs here. In most species, the fertilized eggs are released by partially tearing the epidermis, but in some species it is released through fallopian tubes, which are protonephridia with a coelomic funnel. The development usually takes place via a freely swimming trochophora larva, but in Protodriloides with its very large eggs it occurs directly in a cocoon from which finished worms hatch.

Systematics

In 1868 Anton Schneider described the first species that is now included in this group, Polygordius purpureus . Berthold Hatschek placed this species in a new genus Protodrilus in 1881 . In 1891, Berthold Hatschek described the subclass Archiannelides within the Annelida with the genera Protodrilus and Polygordius , each of which he granted the status of a family: Protodrilidae (in the sea, in the sand) and Polygordiidae (in the sea, beach region). He expressly ruled out other families that were put here by other researchers, which he understood under Archiannelides essentially a group in the range of the later taxon Protodriliformia . Marian Hope Pettibone described the order Protodrilida in 1982 with the families Protodrilidae ( Protodrilus and Protodriloides ) and Saccocirridae. In 1988 Günter Purschke and Claude Jouin-Toulmond compared the taxon Protodrilida, in which they included the genera Parenterodrilus , Protodriloides , Protodrilus and Saccocirrus , as a monophyletic group to the sister group of the Spionida , while Kristian Fauchald and Gregory Rouse could not recognize such a relationship in 1997 put the three families Protodrilidae, Protodriloididae and Saccocirridae as familiae incertae sedis in the order Canalipalpata .

The following genera belong to the three families in the order Protodrilida :

literature

  • Anton Schneider (1868): About the construction and development of Polygordius. Archives for Anatomy, Physiology and Scientific Medicine, 1868, pp. 51–60, panels II – III.
  • Berthold Hatschek (1881): Protodrilus leuckartii. A new genus of archiannelids. Works from the zoological institutes of the University of Vienna and the zoological station in Trieste 3 (1), pp. 79–92. ( PDF )
  • Berthold Hatschek: Textbook of Zoology, a morphological overview of the animal kingdom as an introduction to the study of this science. Volume 3. Gustav Fischer, Jena 1891. 1. Subclass of the Annelids. Archiannelides. Pp. 411-415, here p. 415.
  • Marian Hope Pettibone: Annelida. In: Sybil P. Parker (Ed.): Synopsis and Classification of Living Organisms , Vol. 2, pp. 1-43. McGraw-Hill, New York 1982. pp. 40f., Protodrilida.
  • Günter Purschke, Claude Jouin (1988): Anatomy and ultrastructure of the ventral pharyngeal organs of Saccocirrus (Saccocirridae) and Protodriloides (Protodriloidae fam. N.) With remarks on the phylogenetic relationships within Protodrilida (Annelida: Polychaeta). Journal of Zoology, London 215 (3), pp. 405-432.
  • Stanley J. Edmonds: Fauna of Australia, Volume 4A. Polychaetes & Allies. The Southern Synthesis 4. Commonwealth of Australia, 2000. Class Polychaeta. Pp. 317f., Family Protodrilida.
  • Gregory Rouse, Fredrik Pleijel: Polychaetes. Oxford University Press, Oxford 2001. pp. 282-284, 72. Protodrilida Pettibone, 1982 .

Individual evidence

  1. ↑ Protodrilidae Hatschek, 1888 WoRMS , 2018. Accessed November 14, 2018th
  2. ↑ Protodriloididae Purschke & Jouin, 1988. WoRMS , 2018. Retrieved November 14, 2018.
  3. ↑ Saccocirridae Czerniavsky, 1881. WoRMS , 2018. Accessed November 14, 2018th