Analysis of the epibiotic bacteria of lobster ( Homarus) eggs and their influence on the loss of eggs from the pleopods

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Epibiotic bacteria on eggs from 66 female lobsters ( Homarus) were examined to determine if these flora were causally related to loss of eggs from the pleopods. Eggs from five categories of berried female were examined. These included (1) wild born/wild spawned H. americanus, N=11, (2) wild born/lab spawned H. gammarus, N=16, (3) wild born/lab spawned H. americanus, N=18, (4) lab born/lab spawned H. americanus, N=10, and (5) laboratory bred hybrids of H. gammarus × H. americanus crosses, N=11. Four morphological types of bacteria were observed. These are: (1) filamentous bacteria, primarily Leucothrix-like, (2) disc-shaped bacteria resembling Microcyclus, (3) colonial rods, and (4) other rods which attached to surfaces by one end only. Wild born/wild spawned H. americanus eggs had all four types of epibionts. Egg coats had a higher number of total bacteria than stalks, including numberous colonial rods, but fewer filaments and other rods. Samples from laboratory spawned H. americanus contained all four types of bacteria with no distinction noted between egg coat and stalks. H. gammarus eggs had fewer surface bacteria than all other samples; these eggs were consistently occupied by a large number of discs, but were without filaments. Hybrid egg samples resembled H. americanus in both the number (high) and diversity (all four) of epibiotic bacteria on egg coat and stalks. Observations showed that: (1) wild spawned eggs can develop a high bacterial load yet still develop normally and be retained, (2) laboratory spawned eggs may drop off for reasons independent of epibiotic growth, or may be retained even when epibiotic growth is severe, or may drop off as epibiotic bacteria establish themselves on coat/stalk surfaces, (3) H. gammarus eggs have relatively clean egg/stalk surfaces and were retained well, (4) hybrid females have eggs resembling those from lab spawned H. americanus females both in epibiotic composition and proclivity toward drop off.