This research applied corpus analysis techniques to a corpus of marine biology texts in Peninsular Spanish (PS) and Latin American Spanish (LAS). The results explain why these varieties of Spanish have different designations for the same sea organism. The focus of this research was thus on types of formal onomasiological variation (Geeraerts, Grondelaers, & Bakema, 1994) and its pervasiveness in Spanish scientific discourse. Also addressed was the incidence of metaphor in specialized concept formation and designation. Domain-specific and standard strategies were used for the semi-automatic retrieval of metaphorical terms. The resulting qualitative and quantitative account of terminological diversity reflected the pervasiveness of intralingual denominative variation in scientific language and also identified its causes.