| Abstract: | ABSTRACTIn Mexico, there are currently two known species of Racekiela: R. ryderii and R. montemflumina. Here we describe a new species from high-altitude streams in central and southern Mexico. Racekiela cresciscrystae sp. nov. presents two morphotypes: thick encrusting with raised ridges or lobose outgrowths at the surface and dark green in colour, or lime-green encrustations. The new species as megascleres presents microspined oxeas from 200 to 300 µm long, some centrotylote, or with malformations. Gemmules are spherical with a tri-layered theca, constituted by radially embedded birotules and pseudobirotules. The birotules have longer shaft than the rotule diameter, which is flat, and some slightly umbonate. Pseudobirotules of typical morphology have strongly or somewhat spined shaft. Spines can be straight or hooked. The species also presents other type of pseudobirotules, which are umbonate and with only small warts, instead of spines. DNA sequences from the nuclear ITS1-5.8-ITS2 region were sequenced from the holotype and a paratype of the new species to determine their phylogenetic relationships with other members of the family Spongillidae. Tree topologies (Bayesian Inference and Maximum Likelihood) were consistent in showing Racekiela creciscrystae sp. nov. as a sister clade of R. montemflumina confirming its allocation in a monophyletic genus Racekiela. A comparison with all the Racekiela species described so far is also included. This paper increases the number of species of freshwater sponges in Mexico, and confirmed that Racekiela is a monophyletic genus with morphological characters very well defined.http://www.zoobank.org/urn:lsid:zoobank.org:pub:3769C54F-23C4-409A-AF02-81F3AA084F7Ahttp://www.zoobank.org/urn:lsid:zoobank.org:act:A512359D-E428-4D04-B08A-E189E3F6F962 |
