. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. 456 M. R. FISHER AND S. C. HAND 3000 K 2000 o o 1000 0. KeV Figure 7. Energy dispersive X-ray analysis of air-dried, freeze-fractured Lucina gills. Period of analysis is 100 seconds. Sulfur (K„ = KeV, K^ = KeV) is clearly the dominant inorganic element, while Fe ( = KeV, K^ = KeV) is not detectable. The Al peak is an artifact due to the aluminum stub used for mounting the specimen. abundance of sulfide is evident from our analyses of core samples taken from the habitat (Table I), and w
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. 456 M. R. FISHER AND S. C. HAND 3000 K 2000 o o 1000 0. KeV Figure 7. Energy dispersive X-ray analysis of air-dried, freeze-fractured Lucina gills. Period of analysis is 100 seconds. Sulfur (K„ = KeV, K^ = KeV) is clearly the dominant inorganic element, while Fe ( = KeV, K^ = KeV) is not detectable. The Al peak is an artifact due to the aluminum stub used for mounting the specimen. abundance of sulfide is evident from our analyses of core samples taken from the habitat (Table I), and we have observed that the bivalve typically resides in close association with the 02-releasing root systems of the seagrasses in these sediments. The size of oxygen-containing zones around the roots, in what is otherwise anoxic sediment, is dependent on the magnitude of O2 flux from the roots and the porosity of the sediment, both of which can be quite variable (Armstrong, 1970). While these oxidized rhizospheres may serve to detoxify potential phytotoxins {, HS") as they come into contact with these zones (Armstrong, 1970), it seems reasonable that such rhizospheres could also serve as an O2 source for L. Jloridana; we have not observed inhalant siphon tubes constructed by the bivalve of sufficient length to allow access to the oxygen in the overlying waters. Thus, while the actual oxygen concentration to which Lucina might be exposed has not been measured, it is clear that the animal's location in the sediment could place it at an oxygen/sulfide interface. As is the case with other lucinids, L. Jloridana appears to have a functional gut. However, Allen (1958) described the digestive system of lucinids as being simplified, with reduction of palps, loss of sorting area, and reduction in the number of restrictions between the stomach and digestive diverticula. Allen suggested that these reductions/ alterations of the gut were to facilitate the acceptance of larger food
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