Are Sipunculans annelids?
While traditionally considered a phylum, Sipuncula may be a subgroup of Annelida, based on recent molecular work. Sipunculans vary in size but most species are under 10 cm (4 in) in length.
Is Echiura a phylum?
Annelid
Echiura/Phylum
What is the leech searching for on the person’s foot?
What is the leech searching for on the person’s foot? Soft, bloodrich spot to latch onto. How does the leech mask a potentially painful bite to the person’s skin? They inject an anesthetic into the skin so they don’t feel the bite.
Does Sipuncula have Chaetae?
The echiurans have minimally a pair of large hooks, usually located ventrally behind the mouth. The sipunculans lack chaetae, but have epidermal hooks formed directly externally on the body.
Are Polychaetes dioecious?
Polychaetes are dioecious – each one produces only male or female gametes. Fertilisation of eggs occurs typically at swarming time when mature adults of a species arise synchronously to the sea’s surface and release their gametes.
Do leeches breathe?
Leeches breathe through the skin. The digestive system contains a crop, or pouch, in which food can be stored for several months. The leech’s saliva contains substances that anesthetize the wound area, dilate the blood vessels to increase blood flow, and prevent the blood from clotting.
What are the two major clades of Echiura?
Recent analyses have recognized two major clades within Echiura; a so-called Bonellia -group, containing Bonellidae and Ikedaidae, and a Urechis -group, containing Urechidae and Echiuridae.
Are U-shaped burrow fossils echiuran?
However, U-shaped burrow fossils that could be Echiuran have been found dating back to the Cambrian. Spoon worms vary in size from the giant Ikeda taenioides, nearly 2 m (7 ft) long with its proboscis extended, to the minute Lissomyema, measuring just 1 cm (0.4 in).
What are the characteristics of echiurans?
Echiurans are unsegmented worms with two body sections; the trunk and an anterior, preoral, extendable proboscis, which is often much longer than the trunk. They range widely in body length, from under 10 mm to over 2 m, and their skin surfaces may be smooth or warty, sometimes with chitinous bristles.
Where do echiurians live?
In the Atlantic Ocean, the greatest echiuran species diversity occurs in the northern temperate region. ( Biseswar, 2009; Brusca and Brusca, 2003; Shapiro, 2012) The name Echiura was first applied to these worms in 1940 by William Wallace Newby. Inter-relationships of echiuran groups remain a contentious area of study.