Convolutriloba

Convolutriloba
Scientific classification
Kingdom:	Animalia
Superphylum:	Deuterostomia (?)
Phylum:	Acoelomorpha
Class:	Acoela
Family:	Sagittiferidae
Genus:	Convolutriloba
Species
Convolutriloba hastifera Convolutriloba longifissura Convolutriloba macropyga Convolutriloba retrogemma

Convolutriloba is a genus of marine acoelomorph worms.

They are usually a few millimetres in length and around a millimetre thick. The body is shield shaped with a rounded anterior and three caudal lobes, though the number may vary in mature individuals.^[1]

They have symbiotic algae that give them a green or brown colour. They also prey on small crustacean larvae like artemia and copepods.^[2] However they cannot survive for long periods in the dark even if they are fed.^[1] The mouth is located on the ventral surface. When feeding, they raise their front ends and fold the lateral edges of their body downward forming a funnel. Prey are trapped by lowering the body onto them.

They reproduce both sexually and asexually. They have captured scientific interest because of the various ways of agammetic asexual reproduction. During budding or architomy the offspring separate from the body by attaching to the substrate and tearing away. The offspring produced by sexual reproduction lack the symbiotic algae and will die unless they can pick them up within a few weeks.^[1]

Like all members of the family sagittiferidae they possess sagittocysts on their skin. Sagittocysts are needle like bodies 18-50 microns long that contain some secretory product. They can be extruded from the body by an associated muscle.^[3] They are believed to play a role in defence and prey capture. Ultrastructurally, they have a vesicular core surrounded by a mesh of actin filaments.

Due to their rapid growth in well-lit aquariums, they are considered pests.

Systematics

• Convolutriloba hastifera (Winsor, 1990): The only species discovered naturally.^[1] the other three were discovered in aquaria. This species undergoes transverse fission (architomy) near the caudal end. The smaller fragment grows a new head and begins moving around in a few days.
• Convolutriloba longifissura (Bartolomaeus & Balzer, 1997) Asexual reproduction in this species occurs by architomy of the caudal end to give a small butterfly shaped piece. This is followed by the small caudal part splitting longitudinally to give two daughter organisms.^[2]
• Convolutriloba macropyga (Shannon & Achatz, 2007): This species is green in colour and has a pair of indentations on either side of the head. Asexual reproduction occurs by the formation of buds facing away from the head from the caudal ends.^[1]
• Convolutriloba retrogemma (Hendelberg & Akesson, 1988): Asexual reproduction occurs by the formation of buds facing away from the head from the caudal lobes.

References

1. ^ ^{a b c d e} Shannon, Thomas; Johannes G Achatz (2007). "Convolutriloba macropyga sp. nov., an uncommonly fecund acoel (Acoelomorpha) discovered in tropical aquaria". Zootaxa 1525: 1–17. ISSN 1175-5326. http://www.mapress.com/zootaxa/2007f/zt01525p017.pdf. 
2. ^ ^{a b} Åkesson, Bertil; Robert Gschwentner, Jan Hendelberg, Peter Ladurner, Johann Müller, Reinhard Rieger (2001-12-01). "Fission in Convolutriloba longifissura: asexual reproduction in acoelous turbellarians revisited". Acta Zoologica 82 (3): 231–239. doi:10.1046/j.1463-6395.2001.00084.x. ISSN 1463-6395. http://homepage.uibk.ac.at/~c719135/pdf/Akesson-Gschwentner-2001.pdf. Retrieved 2011-07-13. 
3. ^ Gschwentner, Robert; Peter Ladurner, Willi Salvenmoser, Reinhard Rieger, Seth Tyler (1999-10-01). "Fine Structure and Evolutionary Significance of Sagittocysts of Convolutriloba longifissura (Acoela, Platyhelminthes)". Invertebrate Biology 118 (4): 332–345. doi:10.2307/3227005. ISSN 1077-8306. http://www.jstor.org/stable/pdfplus/3227005.pdf. Retrieved 2011-07-13.