LIFE HISTORY TRAITS OF MESOCYCLOPS THERMOCYCLOPOIDES HARADA, 1931 (COPEPODA, CYCLOPOIDA) WITH OBSERVATIONS ON NAUPLIAR MORPHOLOGY BY EDUARDO SUÁREZ-MORALES 1,2 ), GRACE A. WYNGAARD 3 ), MARTHA A. GUTIÉRREZ-AGUIRRE 4 ) and JENNIFER COSTANZO 3 ) 1 ) El Colegio de la Frontera Sur (ECOSUR), Unidad Chetumal, A.P. 424, Chetumal, Quintana Roo 77000, Mexico 3 ) Department of Biology-MSC 7801, James Madison University, Harrisonburg, VA 22807, U.S.A. 4 ) Universidad de Quintana Roo, Campus Cozumel, Cozumel, Quintana Roo, Mexico ABSTRACT The naupliar stages of the Asian copepod, Mesocyclops thermocyclopoides Harada, 1931 are described from laboratory-reared specimens collected near the type locality, in Taiwan. The morphology of the Taiwanese nauplii differs from a previous description of nauplii assigned to Mesocyclops cf. thermocyclopoides from Sri Lanka. The morphology of M. thermocyclopoides also differs in several respects from that of its congeners for which nauplii are known, thus supporting previous statements about the identity of the Sri Lankan specimens as related to M. thermocyclopoides but in reality belonging to a different species. It is speculated that several species, even those with morphologically close forms as adults, have recognizable differences at the earliest developmental stages; our findings in M. thermocyclopoides support the hypothesis that naupliar characters are complementary tools in distinguishing closely related species. The maturation time of M. thermocyclopoides is the shortest known in the genus. This species has the smallest genome size reported for Mesocyclops, a feature presumably related to both their small body size and their short maturation time. These features seem to be most relevant when considering this species for culturing, i.e., as a potential control for vector mosquito larvae. RESUMEN Se describen los estadios naupliares del copépodo asiático Mesocyclops thermocyclopoides Harada, 1931 a partir de especímenes cultivados en laboratorio y recolectados cerca de la localidad tipo de esta especie, en Taiwán. La morfología de los nauplios taiwanenses difiere de una descripción previa asignada a Mesocyclops cf. thermocyclopoides de Sri Lanka. La morfología de M. thermo- cyclopoides también es diferente en varios aspectos respecto a la de los nauplios de los congéneres cuyas larvas nauplio se conocen. Estas diferencias apoyan aserciones previas acerca de la identidad de los especímenes de Sri Lanka como una entidad cercana a M. thermocyclopoides pero asignable 2 ) Corresponding author; e-mail: esuarez@ecosur-qroo.mx © Koninklijke Brill NV, Leiden, 2007 Crustaceana 80 (10): 1205-1222 Also available online: www.brill.nl/cr