Lottia

Abstract: The marine mollusk Lottia gigantea, a large grazing limpet of the upper intertidal zone, grazes algal film from a territory which it defends against intrusions by conspecifics and other grazers as well as the gradual encroachment of sessile organisms. The areas of the territories are correlated with the length of the resident Lottia, but for a given size of Lottia the areas vary greatly at different study sites. The thickness of the algal film charcteristic of the territory fluctuates, being greatest in spring. Experimental removal of abundant algal film from some territories in spring was followed by enlargement of these territories relative to controls. Growth rates of Lottia are positively correlated with the thickness of the algal film in their territories. The smaller limpets (1—2 cm in length) of the genus Acmaea are able to crop the algal film more closely than Lottia and will remove almost all the algal film from a territory if the territory—resident is removed. Experiments to determine whether te...

Abstract: SUMMARY We characterized functional and structural properties of cytoplasmic malate dehydrogenases (cMDHs) from six limpets of the genus Lottia that have different vertical and latitudinal distributions. Particular attention was given to the cryptic species pair Lottia digitalis (northern occurring) and L. austrodigitalis (southern occurring) because of recent contraction in the southern range of L. digitalis and a northward range extension of L. austrodigitalis . As an index of adaptation of function, we measured the effects of temperature on the apparent Michaelis–Menten constant ( K m ) of the cofactor NADH ( K m NADH ). K m NADH values of cMDHs from the mid- to high-intertidal, low-latitude species L. scabra and L. gigantea were less sensitive to high temperature than those of cMDHs from the low- and mid-intertidal, high-latitude species L. scutum and L. pelta . cMDH of L. digitalis was more sensitive to high temperatures than the cMDH ortholog of L. austrodigitalis . Thermal stability (rate of loss of activity at 42.5°C) showed a similar pattern of interspecific variation. Comparison of the deduced amino acid sequences showed that interspecific differences ranged from one to as many as 17 residues. Differences in K m NADH and thermal stability between orthologs of L. digitalis and L. austrodigitalis result from a single amino acid substitution. At position 291, the glycine residue in cMDH of L. digitalis is replaced by a serine in cMDH of L. austrodigitalis , a change that favors additional hydrogen bonding and reduced conformational entropy. This difference between closely related congeners demonstrates the role of minor alterations in protein sequence in temperature adaptation and suggests that such variation is important in governing shifts in biogeographic range in response to climate change.

Abstract: Lottia alveus, a gastropod limpet once found only on the blades of the eelgrass Zostera marina from Labrador to New York in the western Atlantic Ocean, is the first marine invertebrate known to have become extinct in an ocean basin in historical time. The last known specimens were collected in 1929, immediately prior to the catastrophic decline of Zostera in the early 1930s in the North Atlantic Ocean. The brackish water refugium of Zostera throughout the decline was apparently outside of this gastropod's physiological range, and the limpet became extinct. Few marine invertebrates have habits as specialized and ranges and tolerances as narrow as did L. alveus. The fact that most marine invertebrates have large effective population sizes may account for their relative invulnerability to extinction.

Abstract: A three-trophic-level interaction among American Black Oystercatchers (Haematopus bachmani), limpets (Lottia spp.), and erect fleshy algae in rocky intertidal communities of central and southern California was documented via manipulative and “natural” experiments. Removal of the territorial limpet (Lottia gigantea) initially caused large increases in the percent cover of erect fleshy algae, followed by a more gradual increase in density of small limpets (Lottia spp.) and a decline in algal cover. Algal cover increased following the removal of small limpets at the sites from which L. gigantea had been removed earlier, thus demonstrating that the large and small limpets had similar inhibitory effects on plant populations. A comparison of sites with and without oystercatchers showed that L. gigantea occupied substrate inclinations in proportion to their availability at sites where oystercatchers were rare, whereas the distribution of L. gigantea was skewed toward vertically inclined substrates where oystercatchers were common. Survival rates of limpets translocated to horizontal and vertical substrates were similar in sites lacking oystercatcher predation, but were much lower on horizontal substrates where oystercatchers were common. Our results are consistent with those from several prior studies in demonstrating that shorelines frequented by humans typically lack oystercatchers. Humans also exploit L. gigantea and reduce populations to low densities of small individuals. These findings may explain why the midlittoral zone of rocky intertidal communities in western North America are so often dominated by high population densities of small limpets.