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A second look at the shipworm: A unique member of seagrass communities

Shipworms are group of unique marine bivalves that burrow into wood and are known to cause costly damage to ships and docks.  Shipworms also play an important ecological role in decomposing organic matter that would otherwise take much longer to break down.

A recent study led by researchers at Northeastern’s Ocean Genome Legacy (OGL) group – including Postdoctoral Researcher Reuben Shipway, Research Technician David Stein, and OGL Director and Professor Dan Distel – reveals novel information regarding a particular boring bivalve that lives in seagrass as opposed to ships and docks.

In the study, recently published a study in the journal PLOS ONE, Shipway and colleagues focus on Z. zenkewitschi, a shipworm unique from its kin because it burrows in seagrass rhizomes rather than terrestrial wood. This shipworm is fairly rare, and was collected from the Sea of Japan as well as off the coast of Russia. As it turns out, however, the differences between Z. zenkewitschi and other Teredinidae (shipworms) hardly stop there.

Seagrass boring shipworms are the only type of Teredinidae that exhibit male dwarfism, in which multiple males actually live within a single larger female’s mantle. Like many other marine species, most shipworms reproduce via broadcast spawning, in which organisms release their gametes into the water and fertilize and develop externally.  In contrast, seagrass shipworms fertilize internally, and females often brood the eggs under the gills for a time before releasing them into the water as larvae.

Notably, this research has allowed for specimens of an extremely rare organism to be made available to the wider scientific community.  The researchers achieved this by extracting and preserving Z. zenkewitschi DNA at OGL, allocating a Neotype specimen at the Harvard Museum of Comparative Zoology, and by providing DNA barcoding sequencing data to the online repository GenBank.

Prior to this study, these mysterious shipworms and their unique life history characteristics were not fully understood. While Z. zenkewitschi is one of the only species discovered of its genus, it is speculated that other seagrass boring shipworms have been identified in Vietnam and Papua New Guinea and in fact Shipway and colleagues have studied specimens found in the Philippines. This work by the OGL improves understanding of these important, but seldom studied, species of shipworm.