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Leptothecata

Leptothecata
Leptothecata, or Thecata is surrounded by a chitinous outer layer as its exoskeleton, including gonophores, their reproductive organ. Leptothecata obtain radial symmetry, in which their gonads can be found in their radial canals. Their morphological characters normally have ranged from benthic to planktonic stages. Characters associated with benthic are the polyps and colony forms, while planktonic is medusae. Leptothecata has a vast and complex variation among all species within the hydrozoan clade. Thecata colonies also have extensive specialization due to their polyps function and variation. Most Leptothecata possess statocysts, which are used for defense and protection. The classes that have lost their statocysts have been changed ancestrally over time rather than a direct loss.

Characteristics
Colony architecture among Leptothecata comprises extensive diversity found in the hydrozoans. Their life cycles have been found to be connected with changes in colony shapes. Zooid polymorphism within the colonies are usually specialized. Polyps that make up the colonies tend to have three specialities and functions. First being the gastrozooid, which has their speciality of nutrition and digesting the food. Second, the gonozooid which is the reproductive polyp. Third, being the dactylozooid which function works in defense for the colony. The dactylozooid recently had become more highly variable with not being present in some thecata colony forms, and only possessing the gastrozooid and gonozooid polyps.

Thecata colonies have detectable shapes and arrangements allowing for distinguishing classification between one another. One major shape is when the colonies are erected off a branched colony. Another major shape of thecata is where the colonies can be erected off an unbranched stem. Stolonal colonies are a final major type where their polyps are connected to the creeping part of the colony. Where most cases of the erected branched shape has be found to be derived over time.

Medusae tend to be pelagic. But there are specific medusae species while at the medusa stage can still remain benthic. Polyps can also be free floating, which are called pelagic polyps. Similarly, their gastroular and nervous system have great complexity, as well as their shape. While medusae due tend to lack any presence of visible sense organs. Leptothecata have significant synapomorphies that are present in most of all their species. In regards to their gastrozooids, Lephtothecata have the theca layer on their polyps. Which has allowed the synapomorphy for Leptothecata to form hydrothecae that is made also made of theca that surrounds the gonozooid.

Reproduction and Development
Leptothecata have distinguishing factors in the presence of morphological dimorphism. The dimorphism in the species classes has led to great complexity within their taxonomic identification. Majority of the thecate hydroids use asexual reproduction in response to budding. They have also been known for their plasticity, allowing them to adapt and grow in their given environment. Thecata's branch has a mutual similarity based on mature gamete localization, where they posses their mature gametes located through their radial canals.

Location
Among Leptothecata’s diversified species, they have great variability within their organization and life cycles. Leptothecata can be found worldwide in all marine environments. The location of where Leptothecata are found ranges from shallow waters to the deep sea, most being marine species. In their polyp and medusa form, due to natural factors they can travel outside their native location. This is usually done by currents or if attached to other vertebrates. Due to the hydroids' broad range of locations, they also have been known to play in many ecosystem factors. They provide shelter and protection and are a known food source for other marine species. Leptothecata has been the main attraction in many great expeditions and studies due to the broad spectrum of thecate hydroids within their order. These developments have led to further discoveries of finding locations where thecate hydroids can be relatively rich in the marine environment. Allowing researchers to study a range of differences based on the colonies, the hydrotheca and even the pairs of thecae themselves.