Anne Marie Power

Spatial and temporal variation in settlement and recruitment of the intertidal barnacle Semibalanus balanoides (L.) (Crustacea : Cirripedia) over a European scale

Variation in the level of settlement and recruitment in the intertidal barnacle Semibalanus balanoides was studied using a hierarchical sampling programme. The effect of three spatial scales, 10s of metres (sites), 1000s of metres (shores) and 100s of kilometres (locations), was determined. The largest spatial scale represented the distance between four widely separated locations, Sweden, the Isle of Man, SW Ireland and SW England, covering a large part of the range of S. balanoides in Europe. Temporal variation was determined by comparison between two years, 1997 and 1998. The settlement period of S. balanoides varied in length and timing, being earlier and shorter at the most northerly location, Sweden. The duration of settlement showed little difference among shores within locations, but the pattern of settlement did vary. Estimates of total settlement throughout the settlement period and of recruitment at the end of this period both showed substantial variation among locations which was dependent on the year of study. There was little consistency in the ranking of locations between the two years. Recruitment showed significant variation at the lower spatial scales of shore and site. In addition, examination of variance components showed a high degree of variation between replicates within sites in 1997. There was a significant relationship between settlement and recruitment at three of the four locations. Across all locations variation in settlement explained between 29 and 99% of variation in recruitment. However, locations showed distinct differences in the level of post-settlement survival.

Using historical data to detect temporal changes in the abundances of intertidal species on Irish shores

An historical data set, collected in 1958 by Southward and Crisp, was used as a baseline for detecting change in the abundances of species in the rocky intertidal of Ireland. In 2003, the abundances of each of 27 species was assessed using the same methodologies (ACFOR [which stands for the categories: abundant, common, frequent, occasional and rare] abundance scales) at 63 shores examined in the historical study. Comparison of the ACFOR data over a 45-year period, between the historical survey and re-survey,showed statistically signi¢cant changes in the abundances of 12 of the 27 species examined. Two species(one classed as northern and one introduced) increased signi¢cantly in abundance while ten species (¢ve classed as northern, one classed as southern and four broadly distributed) decreased in abundance. The possible reasons for the changes in species abundances were assessed not only in the context of anthropogenic eiects, such as climate change and commercial exploitation, but also of operator error. The error or diierences recorded among operators (i.e. research scientists) when assessing species abundance using ACFOR categories was quanti¢ed on four shores. Signi¢cant change detected in three of the 12 species fell within the margin of operator error. This eiect of operator may have also contributed to the results of no change in the other 15 species between the two census periods. It was not possible to determine the eiect of operator on our results, which can increase the occurrence of a false positive (Type 1) or of a false negative (Type 2) outcome.

Unusual Adhesive Production System in the Barnacle Lepas anatifera: An Ultrastructural and Histochemical Investigation

Adhesives that are naturally produced by marine organisms are potential sources of inspiration in the search for medical adhesives. Investigations of barnacle adhesives are at an early stage but it is becoming obvious that barnacles utilize a unique adhesive system compared to other marine organisms. The current study examined the fine structure and chemistry of the glandular system that produces the adhesive of the barnacle Lepas anatifera. All components for the glue originated from large single‐cell glands (70–180 μm). Staining (including immunostaining) showed that L‐3,4‐dihydroxyphenylalanine and phosphoserine were not present in the glue producing tissues, demonstrating that the molecular adhesion of barnacles differs from all other permanently gluing marine animals studied to date. The glandular tissue and adhesive secretion primarily consisted of slightly acidic proteins but also included some carbohydrate. Adhesive proteins were stored in cytoplasmic granules adjacent to an intracellular drainage canal (ICC); observations implicated both merocrine and apocrine mechanisms in the transport of the secretion from the cell cytoplasm to the ICC. Inside the ICC, the secretion was no longer contained within granules but was a flocculent material which became “clumped” as it traveled through the canal network. Hemocytes were not seen within the adhesive “apparatus” (comprising of the glue producing cells and drainage canals), nor was there any structural mechanism by which additions such as hemocytes could be made to the secretion. The unicellular adhesive gland in barnacles is distinct from multicellular adhesive systems observed in marine animals such as mussels and tubeworms. Because the various components are not physically separated in the apparatus, the barnacle adhesive system appears to utilize completely different and unknown mechanisms for maintaining the liquid state of the glue within the body, as well as unidentified mechanisms for the conversion of extruded glue into hard cement. J. Morphol., 2012.

Mechanisms of Adhesion in Adult Barnacles

Barnacles belong to the phylum Crustacea (following the taxonomy of Newman, 1987), which makes them segmented animals with jointed limbs, an exoskeleton that periodically moults, and a complex lifecycle involving metamorphosis between larval and adult forms. The group of crustaceans to which barnacles belong, the Cirripedia, has a unique larval form — the cyprid. This life history stage is adapted to locate a spot on which to permanently settle, develop, grow, and survive for the rest of its life. Barnacles have a worldwide distribution and various lifestyles, from parasitic species on the gills of decapod crustaceans to free-living groups. The free-living groups are adapted to permanently attach via cement onto other living organisms, rocks or man-made materials, and barnacle “fouling” on marine installations and cargo ships is increasingly of economic concern (Adamson and Brown, 2002). Within the free-living barnacles, a further division is recognized between acorn (Order Sessilia) and stalked (Order Pedunculata) forms. Certain stalked species are termed “pleustonic” due to a lifestyle at the air/water interface (see Bainbridge and Roskell, 1966) and these are the species which will be emphasized in this chapter (Fig.9.1A-C). Open image in new window Fig.9.1 (A) Lepas anatifera showing capitulum (cap) and peduncle (p), scale bar 1 cm; (B) pleustonic species L. Anatifera attached to glass and Dosima fascicularis with glue fl oat; (C) D. Fascicularis with fl oat (f), scale bar 1 cm; (D) transverse section of peduncle in L. Anatifera stained using AZAN (Kiernan, 1999) showing position of the cuticle lining of the peduncle (c), circular and longitudinal muscle layers (mu), ovarioles (o), hemocoelic space (h) and glue gland cells (g), scale bar 500 µm; (E) schematic of glue apparatus in L. Anatifera including the position of the ovarioles/glue glands (o/g) in the peduncle and principal canal (pc); (F) schematic of detailed glue glands in L. Anatifera including mature cement gland (mcg), young cement gland (ycg), lumen (lu) of the principal canal, vacuole (vac), collector canal (cc), secondary canal (sc), intracellular canal (ic), large nucleus with numerous nucleoli (n). Schematic in B is reproduced with permission from Ankel (1962) and drawings in E and F are reprinted with permission of Lacombe and Liguori (1969)

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.

The chemistry of stalked barnacle adhesive (Lepas anatifera)

The results of the first chemical analysis of the adhesive of Lepas anatifera, a stalked barnacle, are presented. A variety of elements were identified in scanning electron microscopy with energy dispersive spectrometry (SEM-EDS) of the adhesive, including Na, Mg, Ca, Cl, S, Al, Si, K and Fe; however, protein–metal interactions were not detected in Raman spectra of the adhesive. Elemental signatures from SEM-EDS of L. anatifera adhesive glands were less varied. Phosphorous was mostly absent in adhesive samples; supporting previous studies showing that phosphoserines do not play a significant role in adult barnacle adhesion. Disulfide bridges arising from Cys dimers were also investigated; Raman analysis showed weak evidence for S–S bonds in L. anatifera. In addition, there was no calcium carbonate signal in the attenuated total reflectance Fourier transform infrared spectra of L. anatifera adhesive, unlike several previous studies in other barnacle species. Significant differences were observed between the Raman spectra of L. anatifera and Balanus crenatus; these and a range of Raman peaks in the L. anatifera adhesive are discussed. Polysaccharide was detected in L. anatifera adhesive but the significance of this awaits further experiments. The results demonstrate some of the diversity within barnacle species in the chemistry of their adhesives.

Morphology of the Cement Apparatus and the Cement of the Buoy Barnacle Dosima fascicularis (Crustacea, Cirripedia, Thoracica, Lepadidae)

Barnacles produce a proteinaceous adhesive called cement to attach permanently to rocks or to other hard substrata. The stalked barnacle Dosima fascicularis is of special interest as it produces a large amount of foam-like cement that can be used as a float. The morphology of the cement apparatus and of the polymerized cement of this species is almost unknown. The current study aims at filling these gaps in our knowledge using light and electron microscopy as well as x-ray microtomography. The shape of the cement gland cells changes from round to ovoid during barnacle development. The cytoplasm of the gland cells, unlike that of some other barnacles, does not have distinct secretory and storage regions. The cement canals, which transport the cement from the gland cells to the base of the stalk, end at different positions in juvenile and mature animals. With increasing size of the cement float, the exit of the cement canals shift from the centrally positioned attachment disk of the vestigial antennules to more lateral positions on the stalk. The bubbles enclosed in the foam-like float are most likely filled with CO2 that diffuses from the hemolymph into the cement canal system and from there into the cement.

Prolonged settlement and prediction of recruitment in two sympatric intertidal Chthamalus species from south-west Ireland

Attached cypris larvae and less than one month old metamorphs of Chthamalus stellatus and C. montagui (Crustacea: Cirripedia) were sampled from random quadrats on two shores in County Cork, Ireland, from July 1996 to June 1997. Cyprids of C. stellatus were much more abundant than those of C. montagui , but the relative abundance of metamorphs of the two species did not differ significantly. Cyprid abundance predicted metamorph recruitment intensity during peak settlement in C. stellatus but not in C. montagui .

The sizes at settlement in natural populations of the cyprids of Chthamalus montagui and C. stellatus

The lengths of chthamalid cyprids collected during August 1996 on six rocky shores in County Cork, Ireland are reported. The lengths showed a bimodal distribution. The smaller length mode corresponded well with the length range of laboratory-reared cyprids of Chthamalus montagui (Crustacea: Cirripedia), whilst the larger length mode was greater than the length range reported for laboratory-reared C. stellatus . Size may be a useful means to identify Chthamalus cyprids in field investigations.

Long-term, high frequency in situ measurements of intertidal mussel bed temperatures using biomimetic sensors

At a proximal level, the physiological impacts of global climate change on ectothermic organisms are manifest as changes in body temperatures. Especially for plants and animals exposed to direct solar radiation, body temperatures can be substantially different from air temperatures. We deployed biomimetic sensors that approximate the thermal characteristics of intertidal mussels at 71 sites worldwide, from 1998-present. Loggers recorded temperatures at 10–30 min intervals nearly continuously at multiple intertidal elevations. Comparisons against direct measurements of mussel tissue temperature indicated errors of ~2.0–2.5 °C, during daily fluctuations that often exceeded 15°–20 °C. Geographic patterns in thermal stress based on biomimetic logger measurements were generally far more complex than anticipated based only on ‘habitat-level’ measurements of air or sea surface temperature. This unique data set provides an opportunity to link physiological measurements with spatially- and temporally-explicit field observations of body temperature.