Phylum Onychophora The Velvet Worms

Characteristics of the Phylum Onychopora

Characteristics of the Phylum Onychopora Bilaterally symmetrical with a through gut.

Characteristics of the Phylum Onychopora Bilaterally symmetrical with a through gut. Body with 14-43 pairs of un-jointed fleshy legs.

Characteristics of the Phylum Onychopora Bilaterally symmetrical with a through gut. Body with 14-43 pairs of un-jointed fleshy legs. Well developed hemocoelic body cavity with a open circulatory system.

Characteristics of the Phylum Onychopora Bilaterally symmetrical with a through gut. Body with 14-43 pairs of un-jointed fleshy legs. Well developed hemocoelic body cavity with a open circulatory system. Cuticle covered epidermis, with ecdysone mediated molting (ecdysis).

Characteristics of the Phylum Onychopora Bilaterally symmetrical with a through gut. Body with 14-43 pairs of un-jointed fleshy legs. Well developed hemocoelic body cavity with a open circulatory system. Cuticle covered epidermis, with ecdysone mediated molting (ecdysis). Gaseous-exchange organs simple tubular tracheae issuing in tufts from small spiracles.

Anatomy

Legs with claws

Anatomy

Anatomy Oral Papilla Lips and Jaws

Well Developed Eyes

Circulation and Gas Exchange Circulatory system is an open and very similar to the arthropod hemocoel circulatory system. Gas exchange is by tracheae.

Reproduction Accept for one species all dioecious. Males deposit spermatophor around or on the female. (ovoviviparous and viviparous)

Viviparous species have a “placenta” like structure.

About 110 species all terrestrial

However their fossils have been found in the Middle Cambrian marine faunas.

Hallucigenia sparsa an Onychophoran from the Burgess Shale deposits of Canada

Aysheaia, from the Middle Cambirian

Ancient Earth's Anomalous Overlords

Phylum Tardigrada the Water Bears

Characteristics of the Phylum Tardigrada

Characteristics of the Phylum Tardigrada Bilaterally symmetrical; minute, squat. 0.3-0.5 mm.

Characteristics of the Phylum Tardigrada Bilaterally symmetrical; minute, squat. 0.3-0.5 mm. A through straight gut.

Characteristics of the Phylum Tardigrada Bilaterally symmetrical; minute, squat. 0.3-0.5 mm. A through straight gut. Body monomeric although with four pairs of short un-jointed claw-bearing legs.

Characteristics of the Phylum Tardigrada Bilaterally symmetrical; minute, squat. 0.3-0.5 mm. A through straight gut. Body monomeric although with four pairs of short un-jointed claw-bearing legs. Coelom has been thought to be a pseudocoelom however, more recently they think it is a reduces hemocoel.

Characteristics of the Phylum Tardigrada Bilaterally symmetrical; minute, squat. 0.3-0.5 mm. A through straight gut. Body monomeric although with four pairs of short un-jointed claw-bearing legs. Coelom has been thought to be a pseudocoelom however, more recently they think it is a reduces hemocoel. Ecdysone mediated molting like arthropods.

Anatomy

Well Developed Stylet For Feeding

Reproduction Sexual and parthenogenesis are the reproductive modes exhibited in the Tardigrada.

Reproduction Most lay Ornamental eggs.

Reproduction

Reproduction

Biology Scientists have reported tardigrades in hot springs, on top of the Himalayas, under layers of solid ice, and in ocean sediments. Many species can be found in milder environments such as lakes, ponds, and meadows, while others can be found in stone walls and roofs.

Most tardigrades live in the water/air interface.

Biology Tardigrades are one of the few groups of species that are capable of reversibly suspending their metabolism and going into a state of cryptobiosis. Several species regularly survive in a dehydrated state for nearly 10 years. Depending on the environment, they may enter this state via anhydrobiosis, cryobiosis, or other ways. Their metabolism lowers to less than 0.01% of normal and their water content can drop to 1% of normal. Their ability to remain desiccated for such a long period is largely dependent on the high levels of sugar which protects their membranes.

Tardigrades Produce Tuns

Tardigrade Tun

Some Tardigrades such as Halobiotus crispae also demonstrate cyclomorphosis, or seasonal transformations, molting into a thickly armored but still mobile winter form which may survive complete freezing for six months at a time. This species is a sea-dweller, but its spring form can tolerate fresh water produced as ice begins to melt.

Other tardigrades are even parasitic Other tardigrades are even parasitic. The species Tetrakentron synaptae is fully adapted to the outer body of the sea cucumber Leptosynapta galliennei, draining fluids from its epidermal cells. Females of this species (A) are flattened, tick-like and virtually immobile, their mouth situated beneath their domed bodies and their anus farther up their "back." Males, unusually, have been observed in two forms; slender, more mobile males (B) and nearly immobile "dwarf" males (C) who cluster around females.