Species names are binominal; the first word is the genus name and is always capitalized, the second word is the specific epithet and is never capitalized the combination of both words is the species name. Thus, a species name should always be written out in full and italicized (e.g., Tigriopus californicus) the first time indicated in a section. After that it can be shortened to T. californicus.
Never write the just the species epithet californicus . . . or it could be confused with Myotis californicus (a California bat) or Microtus californicus (a California vole)!
Species names should not be used as adjectives (eggs of T. californicus not T. californicus eggs) or with possessive (reproduction of T. californicus not T. californicus reproduction).