Ruth M. O’Riordan

Verification of cyprid size as a tool in the identification of two European species of Chthamalus barnacles using mtDNA-RFLP analysis

Adult barnacles of Chthamalus stellatus and Chthamalus montagui were collected in August 1998, from Garrettstown Co. Cork and Kilkee Co. Clare, in southwest and west Ireland, respectively. Attached cypris larvae were collected during the settlement season of C. stellatus and C. montagui, on 2 shores in Co. Cork and 1 shore on Clare Island, Co. Mayo in west Ireland. Cyprid collections were made during either August or September, in 1992, 1994 and 1998 and all cyprids were measured along their carapace length. Size-frequency histograms were produced for each sampling occasion. Total DNA was extracted and the COI-COII mitochondrial genes were PCR amplified, both from selected adults and cyprids of each species collected in 1998. Composite haplotypes, produced by digesting PCR products with the restriction endonucleases TaqI and RsaI, showed clear identification between the 2 species as adults and larvae. Of the 68 cyprids examined, those measuring 525 μm and under were found to have RFLP profiles corresponding with C. montagui adults, while those of 550 μm and larger were found to match C. stellatus adults. The findings verify previous length-frequency analysis. Carapace length is an important character in the identification of C. stellatus and C. montagui cyprids. The PCR primers developed during this study will also amplify DNA from 4 other species of . acorn barnacle.

Intrapopulational distribution of Meiogymnophallus minutus (Digenea, Gymnophallidae) infections in its first and second intermediate host.

Host size and age are generally assumed to play a pivotal role in digenean trematode infection patterns, accounting for much of the variation found within intermediate host populations. However, knowledge is based on a limited number of studied host–parasite systems. We investigated the shell length class distribution of Meiogymnophallus minutus infections within populations of the first intermediate host Scrobicularia plana and second intermediate host Cerastoderma edule. Infections occurred very early in the life of the two intermediate hosts. Both prevalence and intensity of infections increased with host shell length and displayed extremely high values amongst large individuals. Whilst metacercarial infection patterns in juvenile C. edule could be best explained by differences in host shell length, in adult cockles, the effect of host age on infection levels prevailed. The microsporidian hyperparasite Unikaryon legeri, occurring in the metacercarial stage of M. minutus, was particularly abundant in aged cockles, strongly influencing infection patterns of the gymnophallid. Our results are consistent with the intrapopulational distribution reported from other digenean trematode parasites. The relative influence of both host size and age and the underlying mechanisms as well as the impact of hyperparasitism on M. minutus infection patterns are discussed.

Climate change impacts on potential recruitment in an ecosystem engineer

Climate variability and the rapid warming of seas undoubtedly have huge ramifications for biological processes such as reproduction. As such, gametogenesis and spawning were investigated at two sites over 200 km apart on the south coast of Ireland in an ecosystem engineer, the common cockle, Cerastoderma edule. Both sites are classed as Special Areas of Conservation (SACs), but are of different water quality. Cerastoderma edule plays a significant biological role by recycling nutrients and affecting sediment structure, with impacts upon assemblage biomass and functional diversity. It plays a key role in food webs, being a common foodstuff for a number of marine birds including the oystercatcher. Both before and during the study (early 2010–mid 2011), Ireland experienced its two coldest winters for 50 years. As the research demonstrated only slight variation in the spawning period between sites, despite site differences in water and environmental quality, temperature and variable climatic conditions were the dominant factor controlling gametogenesis. The most significant finding was that the spawning period in the cockle extended over a greater number of months compared with previous studies and that gametogenesis commenced over winter rather than in spring. Extremely cold winters may impact on the cockle by accelerating and extending the onset and development of gametogenesis. Whether this impact is positive or negative would depend on the associated events occurring on which the cockle depends, that is, presence of primary producers and spring blooms, which would facilitate conversion of this extended gametogenesis into successful recruitment.

Temporal variation in prevalence and cercarial development of Echinostephilla patellae (Digenea, Philophthalmidae) in the intertidal gastropod Patella vulgata

The trematode Echinostephilla patellae is an abundant but scarcely investigated parasite found in coastal ecosystems of the British Isles. Redial and cercarial stages of the digenean occur in the digestive gland and gonads of common limpets Patella vulgata. Here, we present data on the temporal distribution of E. patellae infections in P. vulgata from an intertidal site on the Irish south coast as well as on the intramolluscan development of the cercariae over a period of one year. Prevalence of infection showed temporal variation with a distinct peak in September, possibly related to an increase in the abundance of bird final hosts coinciding with comparatively high temperatures at the study locality during the summer months. Maturation of cercarial stages was strongly correlated with water temperature. Whilst fully developed cercariae were present in the rediae from May to November, large numbers of infective stages occurred in the limpets’ mantle blood vessels — where they accumulate prior to release — between June and September, suggesting this period of time to be the main transmission window for E. patellae cercariae.

Reproductive biology of the shore crab Carcinus maenas (Decapoda, Portunidae): a macroscopic and histological view

A histological study of the reproductive cycle of male and female shore crabs, Carcinus maenas (Linnaeus), was performed monthly on the South West coast of Ireland (from December 2006 to July 2008). The calculated sex ratio deviated from equality, 1:0.53, revealing a strong male bias. A system was devised, based on screening of tissue sections, to describe and stage gametogenic development. Histological examinations revealed that ovarian development occurred biannually, with a primary winter cycle in which the larger crabs reproduced and a secondary summer cycle, when smaller crabs reproduced. An association was observed where more of the larger specimens were caught in the summer months and the smaller specimens in the winter months, which inversely correlated with the segregated breeding cycles. There was strong evidence that mature male crabs could potentially copulate year round since all mature specimens, collected throughout the year, contained viable spermatozoa. Developmental stages of oogenesis and spermatogenesis were described to develop a practical gonadal index for this portunid crab, providing information on the biology of this species, which will be of benefit for fisheries management.

Habitat selection, philopatry and spatial segregation in rural Irish hedgehogs ( Erinaceus europaeus )

Abstract As a non-territorial species with no known dispersal period, there are no obvious factors that regulate hedgehog numbers in an area. This study aimed to examine these factors and involved the radio-tracking of rural hedgehogs over a 3-year period. Males had a significantly larger mean annual home range (56 ha) than females (16.5 ha), which was at its maximum during the breeding season. Outside of the breeding season, the home range was relatively small (4–5 ha) in both sexes. The home ranges of males completely overlapped both each other and all of the females. In contrast, females occupied more exclusive areas with little overlap between one another. On a nightly basis, both sexes occupied spatially independent areas with little overlap. Compositional analysis of the data showed that habitats were not used in proportion to their availability but were selected, and this changed seasonally, with the highest preference being for garden and arable land. Hedgehogs tagged for consecutive years exhibited site philopatry and followed the same pattern of habitat selection annually. It is suggested that the spatial separation observed amongst individual hedgehogs could restrict numbers in an area and that female numbers reach a carrying capacity before that of males.

Intra- and interhabitat differences in hedgehog distribution and potential prey availability

Abstract With little previous research on the European hedgehog (Erinaceus europaeus Linnaeus) in Ireland, 22 hedgehogs (16 females and six males) were tagged at a rural Irish site between June 2008 and November 2009. Transect, surveying surface invertebrates were carried out in the centre and hedgerow in arable and pasture lands distributed throughout the site. In both years, hedgehogs selected arable land and this coincided with a rise in invertebrate density. This and the fact that within the arable field hedgehogs concentrated their activity where there was a greater density of potential prey suggest that hedgehogs learn the spatial location of prospective food. Contrary to other research, in most of the hedgehogs’ home range, individuals consistently foraged in the centre of both pasture and arable lands. Potential prey was lower in fields where the hedgerow had no bramble understory, and this suggests that hedgerow with good ground cover acts as an important reserve for invertebrates. Badgers (Meles meles Linnaeus) were seen on 12 occasions within the hedgehogs’ home range and they did not appear to have a negative effect on the hedgehogs’ use of the site. It was concluded that the main factor affecting the hedgehogs’ distribution within each habitat was the availability and accessibility of potential prey.

The preference for yew (Taxus baccata) by a red (Sciurus vulgaris) only squirrel population

Abstract Context. As invasive grey squirrels continue to spread, red only areas are becoming rarer. It has been reported that red squirrels can outcompete greys only in pure coniferous woodland. In areas of sympatry with grey squirrels, there are concerns about red squirrels’ dependence on certain coniferous tree species in light of recent tree diseases. Aims. This study aimed to investigate tree selection by red squirrels in an area vulnerable to the spread of the grey squirrel, but currently free of this species. Methods. During 2013–14, squirrels were trapped and monitored on a 315-ha managed island, with a woodland characterised by a mixture of deciduous and coniferous species. Radio-tracking revealed that squirrels clustered their activity along a network of yew trees, a preference they showed throughout the year. Trap success was also higher in traps placed on yew trees. Yew and beech were selected most commonly, but squirrels were also observed foraging on other items, such as sycamore flowers and lichen. Squirrels spent 35% of their time foraging, utilising the greatest number of tree species in June (n = 13). In spring, squirrels foraged to a greater extent on the ground than in the trees, and exploited a lower number of tree species. Conclusions. There has been little previous data on the use of yew trees by red squirrels, but they have previously been listed as a species that is preferred by red squirrels rather than greys. This study has further emphasised the importance of this tree species to red squirrels. Implications. The continued spread of the grey squirrel may lead to red squirrels becoming restricted to areas of intense management such as parks and, accordingly, optimum tree planting is required from the onset for the long-term maintenance of red squirrels. With recent concern about the disease vulnerability of other coniferous species, this study emphasises the relative importance of yew and other tree species in the distribution of red squirrels.

A preliminary investigation into the endoparasite load of the European hedgehog (Erinaceus europaeus) in Ireland

Abstract The European hedgehog is strictly protected in the Republic of Ireland but has been little studied. Carcasses, such as road kill casualties, can provide valuable information on population demographics, parasite load and general body condition. This study aimed to examine the species of endoparasites present in hedgehogs, their prevalence and intensities and whether differences occurred depending on the age and sex of the hedgehog. Carcasses were collected and examined from around Ireland, over a 3-year period. In 21 of the 23 hedgehogs examined, endoparasites were identified. The nematode species, Crenosoma triatum and Capillaria erinacei were both positively identified. C. striatium was confined to the lungs, whereas C. erinacei was the most prevalent (87%) endoparasite and occurred in the stomach and intestines. There was a significantly higher load of Crenosoma striatum observed in male hedgehogs compared to females, but no significant difference was observed in the intensity of C. erinacei between the sexes. In all tissues, a greater mean endoparasite load was observed in male hedgehogs. Sex differences in exposure or immunity to parasitism could be related to the males’ larger home range and the effects of oestrogen levels on immunity.

A health status survey of clams, Mya arenaria and Ensis siliqua, in the Irish Sea

The soft shell clam, Mya arenaria, and the razor clam, Ensis siliqua, are widely distributed in Irish waters. Though the reproductive biology and other aspects of the physiology of these species has been previously investigated, little or no data are currently available on their health status. As this knowledge is essential for correct management of a species, M. arenaria and E. siliqua were examined to assess their current health status using histological and molecular methods, over a period of sixteen months. No pathogens or disease were observed in M. arenaria, and low incidences of Prokaryote inclusions, trematode parasites, Nematopsis spp. and eosinophilic bodies were recorded in razor clams for the first time in Northern European waters.