Mesospora
Mesospora is a genus of macroalgae that was described by Anna Weber-van Bosse in 1911. Although considered a taxonomic synonym of "Hapalospongidion", the World Register of Marine Species cites six currently accepted species of the genus. Description. "Mesospora" is characterized as a crustose brown macroalga with a saxicolous habitat, gelatinous crustose thallus, adherent to the substrate without rhizoids, several cells thick basal layer, unbranched erect free filaments, intercalary plurilocular reproductive structures uniseriate or biseriate and unilocular reproductive structures stalked and borne laterally at base of erect vegetative filaments. "Mesospora" is said to be morphologically similar to "Diplura". Their  difference lies in the number of chloroplasts per cell. The "Mesospora" has a single chloroplast per cell, a one-celled sterile tip of the erect filament and unilocular sporangia, while the "Diplura" has several chloroplasts per cell and lacks unilocular sporangia. Species. Species according to WoRMS as of April 17, 2022.