Our ability to reliably use radiocarbon (14C) dates of mollusk shells to estimate calendar ages may depend on the feeding preference and habitat of a particular species and the geology of the region. Gastropods that feed by scraping are prone to incorporation of carbon from the substrate into their shells as evidenced by studies comparing the radiocarbon dates of shells and flesh from different species on different substrates (Dye 1994; Hogg et al. 1998). Limpet shells (Patella sp.) are commonly found in prehistoric midden deposits in the British Isles and elsewhere, however these shells have largely been avoided for radiocarbon dating in regions of limestone outcrops. Results from limpets (Patella vulgata) collected alive on limestone and volcanic substrates on the coasts of Ireland indicate that the shells were formed in equilibrium with the seawater, with no significant 14C offsets. Limpets collected from the east coast of Northern Ireland have elevated 14C due to the output of Sellafield nuclear fuel reprocessing plant. In all locations, the flesh was depleted in 14C compared to the shells. The results will have an important consequence for radiocarbon dating of midden deposits as well as the bone of humans and animals who fed on the limpets.

The red-blooded limpet ‘Shinkailepas’ briandi (Neritimorpha: Phenacolepadidae) is one of the commonest gastropod species at deep-sea hydrothermal vents on the Mid-Atlantic Ridge (MAR). We investigated its population connectivity along MAR as the first such study for gastropods and explored the importance of larval migration for the distribution of vent-endemic animals. Our analyses, based on 1.3-kbp DNA sequences from the mitochondrial COI gene, showed a panmictic population throughout its geographic and bathymetric ranges that span from the northernmost and shallowest Menez Gwen vent field (38°N; 814–831 m depth) to the southernmost and deepest Ashadze field (13°N; 4090 m). Early development of this species is presumed to have a long pelagic duration as a planktotrophic larva; the hatchling with a shell diameter of 170–180 μm attains a constant settlement size of 706 ± 8 μm (mean ± SD). Retention of eye pigmentation in newly settled juveniles, along with the genetic panmixia, suggests that the hatched larva of ‘S.’ briandi migrates vertically to the surface water, presumably to take advantage of richer food supplies and stronger currents for dispersal, as has been shown for confamilial species at hydrothermal vents and cold methane seeps.

Many studies have shown that physical environmental factors cause phenotypic diversity in limpets. However, no studies have documented how substrate conditions (surface shape and topology) affect adhesive force and how they regulate shell morphology in limpets. The intertidal limpet Patelloida pygmaea, having a flat shell, is found exclusively on oyster shells, while P. conulus, with an extremely high shell, is found on Batillaria cumingi. The adhesive force on the B. cumingi was significantly greater in P. conulus than in P. pygmaea, whereas the force on the oyster shell showed no significant difference between these species. On the B. cumingi, a significantly positive correlation was found between adhesive force and volume in P. conulus, and no significant correlation was found in P. pygmaea. In contrast, on the oyster shell, a significant positive correlation was found between adhesive force and volume in both of the two species. These results suggest that the shell of P. conulus becomes higher with increasing own shell size by keeping aperture area relative to body size as small as possible. These morphological differences are most likely due to an adaptation to utilize different habitats and adhere to substrates with different structure and topology.

The reproductive cycles of four limpet species, Patella depressa, Patella ulyssiponensis, Patella vulgata and Patella rustica are described for several locations in northern and central Portugal. Patella depressa and P. ulyssiponensis displayed almost continual gonad activity, with two main spawning periods, September–January and March–June, and minor spawning events dispersed throughout the year. Patella vulgata and P. rustica exhibited highly synchronized reproductive cycles, with well-defined breeding and resting periods. Gonad development in P. vulgata started in September and spawning took place from November–December to March. In P. rustica development started in June and spawning occurred from September–October to December–January. Compared to the 1980s these results suggest that breeding periods are becoming longer in southern species and shorter in northern species.

A cold-shock technique was used to determine radula production rates for the chitons Acanthopleura hirtosa and Plaxiphora albida, and for the limpet Patelloida alticostata, which replaced their radular teeth at rates of 0.40, 0.36 and 0.51 rows d−1, respectively. These rates are far slower than those determined previously for non-iron-mineralizing molluscs, suggesting that the improved working life of the teeth afforded by iron-mineralization acts to significantly reduce replacement rates. In addition, inductively coupled plasma-atomic emission spectroscopy has been used to determine the quantity of iron and other elements comprising the radula of each species. These data, used in conjunction with the radula production rates, reveal that A. hirtosa, Plaxiphora albida and Patelloida alticostata have daily radula mineralization requirements for iron of 3.06, 4.12 and 0.55 μg, respectively. Such information is vital for continuing studies related to the cellular delivery of ions and subsequent biomineralization of the tooth cusps in chitons and limpets.

Morphological and isozyme variations between 13 populations of the species hitherto named Patella granularis were investigated to see whether differences in shell structure between the west coast versus the south and east coasts of southern Africa are supported by other morphological features or by genetic differences. The shells showed a definite decrease in size from west to east, but this is correlated with productivity and is of no diagnostic use in distinguishing between populations. Discriminant functions analysis based on shell morphometrics failed to separate populations from the three coastal regions. Shells from the northern east coast do, however, have shell nodules with a dark pigmentation, distinctly separating them from those further south and west. No differences in radular or soft part morphology were detected between the populations, but the four northernmost populations on the east coast have a significantly shorter Z looping of the gut than the other populations along the coast. Significant microstructural differences in the sperm were also detected between these two groups of populations. Electrophoretic analysis of 16 enzyme loci failed to detect any significant differences between the west and south coast populations, but revealed a genetic identity (Nei) of 0.528 as well as four diagnostic alleles between the four northernmost populations from the east coast compared with those to the south and west. The two genetically distinct forms occurred sympatrically at one of the study sites on the east coast (Coffee Bay). It was concluded the two groupings were sufficiently different to warrant the recognition of a separate species, which is centred in KwaZulu-Natal on the east coast and extends south to Coffee Bay, from where it is replaced by P. granularis. There is, however, no evidence at all that the west coast populations are in any way separable from the remaining populations of P. granularis on the south coast.