Abstract
Lobsters and other crustaceans do not have sterile hemolymph. Despite this, little is known about the microbiome in the hemolymph of the lobster Homarus americanus. The purpose of this study was to characterize the hemolymph microbiome in lobsters. The lobsters were part of a larger study on the effect of temperature on epizootic shell disease, and several died during the course of the study, providing an opportunity to examine differences in the microbiomes between live and recently dead (1-24 h) animals. The hemolymph microbiomes of live lobsters was different from those in dead animals and both were different from the tank microbiome in which the animals had been held. The microbiomes of live lobsters were more diverse and had a different suite of bacteria than those from dead animals. The dominant taxa in live lobsters belonged to Flavobacteriaceae and Rhodobacteraceae, whereas Vibrionaceae and Enterobacteriaceae were predominant in the dead lobsters. Although aquarium microbiomes overlapped with the hemolymph microbiomes, there was less overlap and lower abundance of taxa in comparison with hemolymph from live lobsters. Previous studies reporting bacteria in the digestive tract of lobsters suggested that Vibrionaceae and Enterobacteriaceae had invaded the hemolymph via the gut. Our study suggests that hemolymph bacteria abundant in live lobsters do not originate from the tank milieu and comprise a rich, natural, or native background of bacterial constituents.
Highlights
The American lobster Homarus americanus is a highly valued commercial species and one of the main fishery products in the world
We found a high diversity in the hemolymph microbiomes of live American lobsters
The hemolymph microbiome from live lobsters was different from the tank microbiomes and consisted of several families with known symbiotic relationships in other host taxa
Summary
The American lobster Homarus americanus is a highly valued commercial species and one of the main fishery products in the world. Previous studies used culture techniques to isolate and identify few culturable bacteria in the lobster hemolymph, including significant pathogens (Cornick & Stewart 1966, Bartlett et al 2008), but these methods are highly selective and the results may not be representative of the taxa present in the hemolymph microbiome (Bent & Forney 2008). Quinn et al (2013) examined bacteria in the lobster hemolymph using culture-independent methods (nested-PCR of 16S rRNA and denaturing gradient gel electrophoresis), but reported only a few taxa, and one sample did not have bacteria. In a study using generation sequencing (NGS) of 16S amplicons, the whole hemolymph microbiome of the spiny lobster Panulirus ornatus was found to include a high diversity of potentially symbiotic bacteria (Ooi et al 2019). There have been no NGS studies to date on the microbiome in the hemolymph of H. americanus or other nephropid lobsters
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