Understanding Marine Size Through Data Collection
Craig McClain officially initiated the Marine Organism Body Size (MOBS) project during his sabbatical in 2022. However, his journey collecting body size data for various marine species spans several years prior to this formal launch. With an existing dataset, he was able to consolidate this information into a comprehensive database, ensuring a uniform format and structure.
Craig McClain holding a giant isopod (Bathynomus giganteus), an iconic crustacean from the deep sea
Credit:
Craig McClain
McClain noted a significant challenge in his prior data collection efforts: the taxonomy of marine organisms. He explained that obtaining specific body sizes for all species of octopuses was often problematic due to limited available data, which was contingent on taxonomists publishing their findings, often outdated with the continual discovery of new species.
Fortunately, the establishment of the World Register of Marine Species (WoRMS) in recent years has provided a systematic approach to cataloging marine life. This initiative involves taxonomy experts who validate and assign new species with a unique numerical code, which McClain has linked to his dataset, thereby simplifying the updating process for MOBS as new species are confirmed by WoRMS. Additionally, McClain and his team have accessed body size data from various museum collections to enrich their database.
The scope of the MOBS database centers on measuring body length rather than mass. McClain explained, “Most taxonomic descriptions of new species typically include some linear measurement. For many organisms, that will be the length, perhaps width, and in a fortunate case, height. Weight data is rare unless specifically targeted in research, making it less accessible.”
He further elaborated on the implications of body density variation among different species, stating that, “While mammals tend to have a consistent density, comparing the density of organisms such as a sea slug and a jellyfish reveals substantial differences in carbon content despite equal mass.” He provided another example of contrasting organisms, emphasizing that a one-meter cylindrical worm differs in weight from a one-meter spherical sea urchin. To address these discrepancies, McClain aims to develop an additional database for length-to-weight conversions.
