B. F. Keegan

Field survey of the occurrence and significance of regeneration in Amphiura filiformis (Echinodermata: Ophiuroidea) from Galway Bay, west coast of Ireland

The Boreo-Mediterranean amphiurid Amphiura filiformis (O. F. Müller) occurs in high densities within Galway Bay. This burrowing species consistently shows signs of recent regeneration (of both arms and disc “cap”) at the above locality. Specimens were collected by SCUBA in March, April and May 1980, May 1981, and April 1982. Biomass assays have revealed that individuals with up to 50% (mean ca. 25%) of their entire body weight consisting of regenerated tissue are not uncommon. The occurrence of arm breakage and regrowth was found to be more frequent in the proximal (basal) and mid-arm regions than in the exposed arm tip portions. Roughly 3% of the population were found to be in the process of regenerating the disc “cap” or covering. Preliminary results from gut analyses of potential predators at the sampling station indicate that young flatfish (plaice and dab) actively “crop” the arms of A. filiformis. Records from north western Europe of this species occurring in the diets of fish and invertebrates are considered. In this long-lived species, the continual necessity to regenerate is deemed to be a major drain on bodily resources.

The use of REMOTS® technology in monitoring coastal enrichment resulting from mariculture☆

Abstract REMOTS® technology is a combination of sediment-profile imagery and computer image analysis. With it, one can deduce the dynamics of biological and physical seafloor processes from imaged structures. The equipment is easy to deploy and broad areal coverage can be accomplished in a very short time. The data return is equally rapid, allowing the implementation of management decisions which based on ‘real time’ information rather than the ‘after the fact’ remedial actions imposed by the more traditional surveying/monitoring methods.

Comparative Analysis of Two Populations of the Brittle Star Amphiura filiformis (Echinodermata: Ophiuroidea) with Different Life History Strategies Using RAPD Markers

Abstract: Random amplified polymorphic DNA (RAPD) analysis was applied to individuals of Amphiura filiformis sampled from two geographic locations that have previously been reported to have different life history strategies. Of thirty-one 10-mer RAPD primers screened initially, four were chosen and used in a comparative analysis of A. filiformis individuals collected from Galway Bay (Ireland) and Concarneau Bay (France). The results show much variation within A. filiformis populations. Although there are some rare alleles particular to each population, overall the populations were not genetically differentiated with the methods employed. Analysis of molecular variance (AMOVA) showed that a minimum of 93% of genotypic variance occurred among individuals within populations. The statistical significance of this pattern was supported by permutation tests. FST values were not significantly different from and UPGMA cluster analyses based on three distance metrics did not separate the two populations.

Seasonal patterns in the reproductive activity of the red whelk, Neptunea antiqua (Mollusca: Prosobranchia) in the Irish Sea

The red whelk, Neptunea antiqua (Mollusca: Prosobranchia) is a dioecious prosobranch species with internal fertilization, and lecithotrophic larval development. Sexual dimorphism, sexual ratio, the size and age at sexual maturity, and the annual breeding and hatching periods of this subtidal neogastropod were investigated in the central western Irish Sea. Sexual dimorphism was evident as female whelks were larger in both length and weight. Subtle differences in shell morphology were also detected between the sexes. All samples taken together indicated an equal male to female sexual ratio for the studied population. Size and age at sexual maturity were noted to differ between sexes, occurring at 75-90 mm (shell length), or four to five years in males, and 95-110 mm, or six to nine years in females. Quantitative and qualitative techniques identified an annual spawning period between late spring and early summer. Egg masses containing between 14 and 84 egg capsules were observed attached to the dorsal surface of whelk shells in the succeeding months. An average fecundity of 63.78 juveniles was estimated per egg mass deposited. Juveniles were observed to hatch after 6-7 months in laboratory maintained aquaria, indicating a hatching period from October to January in the Irish Sea.

Long-term trends in benthic habitat quality as determined by Multivariate AMBI and Infaunal Quality Index in relation to natural variability: A case study in Kinsale Harbour, south coast of Ireland

Benthic Ecological Quality Ratios (EQR) are important tools for assessing the ecological status of coastal and transitional water bodies. Here, we use spatial and time-series data from Kinsale Harbour, Ireland to examine the effects of sample processing methodologies on the outputs of two EQRs: Multivariate AMBI (M-AMBI) and Infaunal Quality Index (IQI). Both EQRs were robust to changes in sieve size from 1mm to 0.5mm, and to changes in the taxa identified in spatial calibration. Both EQRs classified habitat quality in Kinsale as generally Good or High with no evidence of significant change over the time series (1981-2006). IQI classified the ecological status as higher than M-AMBI. There was a significant relationship between IQI and M-AMBI in spatial calibration, but no significant relationship between them in time series. Further research into the behaviour of EQRs in relation to natural variability over long time-scales is needed to discriminate anthropogenic impacts reliably.

Feeding and related morphological structures in the dendrochirote Aslia lefevrei (Holothuroidea: Echinodermata)

The dendrochirote holothuroid Aslia lefevrei (Barrois, 1882), forms dense aggregations [>70 individuals (m-2)-1] within two epibenthic associations on the west coast of Ireland. The holothuroid is a reophilic suspension feeder, utilizing 8 large and 2 small dendritic tentacles in the feeding process. Each tentacle tip terminates in fleshy nodes with 2 to 10 retractile papillate regions containing from 10 to 40 papillar bodies, among which are interspersed small numbers of cilia. Histological observations indicate the presence of secretory bodies both in the papillar regions of the tentacle and interspersed among the epithelial cells of the pharynx. Entrapment of seston on the adhesive papillae appears to be the principal mode of tood capture in A. lefevrei. Besides a suggested chemosensory capacity, the holothuroid seems to be mechanoresponsive to a loading factor on the tentacle tips. The sequence in the usage of the large tentacles of A. lefevrei shows some indication of repetition by individuals, but lacks any basic pattern between individuals. Whilst the same tentacle will not be inserted into the mouth twice in succession, adjacent tentacles often follow each other. Neighbouring and contiguous individuals allow their tentacles to intermesh without, apparently, interfering with the feeding process. Seasonal torpor in the feeding behaviour of A. lefevrei is tentatively interpreted as reflecting temperature-depressed metabolism and refuge-seeking from turbulent conditions.

The significance of imposex levels and TBT contamination in the red whelk, Neptunea antiqua (L.) from the offshore Irish Sea

The extent to which open seas and oceanic waters have been contaminated by TBT is unclear since most sampling programmes have concentrated on inshore areas, particularly near harbours. Accordingly, the red whelk, Neptunea antiqua L. (Mollusca: Prosobranchia), a sublittoral and dioecious prosobranch species, was selected to investigate the potential effects of TBT-induced imposex in the central western Irish Sea. The presence of imposex was noted in > 90% of all female whelks that were examined on a monthly basis over a 12-month period. However, the proliferation of the vas deferens was not considered severe enough to affect the reproductive capabilities of the population. Low concentrations of butyltins were detected in the soft tissues of all whelks examined, ranging from 0.009 to 0.112 microg g(-1) Sn dry wt There was no significant correlation between the documented imposex stages and total butyltin contamination, indicating that the species is not a reliable bioindicator species of the effects of this contaminant.

Population dynamics of Amphiura chiajei (Echinodermata: Ophiuroidea) in Killary Harbour, on the west coast of Ireland

The infaunal ophiuroid Amphiura chiajei Forbes is a dominant member of the A. chiajei community in Killary Harbour, a fjord-like inlet on the west coast of Ireland. High density populations (∼700 individuals/ m2) occur in sediments with a silt/clay content of 80 to 90% and organic carbon levels of ∼5 to 7%. A study of the population dynamics of this species was carried out from November 1985 to October 1988. At the outset, the population consisted of approximately equal numbers of adults and juveniles. By October 1988, the percentage of adults had increased to ∼95%, with little or no change in the mean annual dersities. However, there was some degree of variability between the mean monthly densities. Such variability may have been due to very low bottom temperatures, resulting in mortality among the older members of the population. Observations suggest that in Killary Harbour the species may attain an age of ≥10 yr, with an early annual growth rate of ∼0.5 mm (oral width). Annual recruitment was variable and low, due presumably to intraspecific competition with the adults; recruitment success may be very closely linked to adult mortality. The Killary Harbour findings are considered in the light of what is currently known of similar amphiurid populations in different geographical locations.

The gametogenic cycle of Scrobicularia plana (Mollusca: Bivalvia) in Mweeloon Bay (Galway, west coast of Ireland)

The gametogenic cycle of Scrobicularia plana was studied in Mweeloon Bay (Galway, west coast of Ireland) over the periods of February to September 1996 and January to September 1997. Quantitative (reproductive indices and oocytes size) and qualitative (gonad developmental stages) analysis identified a broad annual breeding cycle, with one protracted spawning event occurring from May until September. Early gonad development had begun by January/February. Spawning animals were first recorded at the end of May and continued to mature throughout the summer. The decrease in temperature in September coincided with the end of the spawning season and gonad regression. Although the species is predominantly dioecious, one case of hermaphrodism was recorded. A female to male sex ratio of 1.1:1 was registered. Sexual maturity occurred at a shell length greater than 20 mm; the smallest individual undergoing sexual development had a shell length of 22.4 mm. The timing of the reproductive cycle in S. plana at Mweeloon Bay is in broad agreement with previous findings on the species carried out in northern latitudes.

In situ behavioural studies on echinoderm aggregations

KurzfassungAn der Westküste Irlands wurden extrem dichte Aggregationen einiger Echinodermen-Arten beobachtet. Die für die Populationsdichten einiger dieser Stachelhäuter ermittelten Werte gehören zu den höchsten, die bisher bekannt geworden sind. Die Untersuchungen konzentrieren sich auf die Lebensweise der HolothuriePseudocucumis mixtaÖstergren unter besonderer Berücksichtigung der Habitatpräferenz, der Art des Einbohrens in den Untergrund, der Nahrungsweise, der Defäkation und des Sinneslebens. In-situ-Studien zeigten, daß ein offensichtlich vom Tag-Nacht-Wechsel gesteuerter Freßrhythmus vorliegt.Summary1. On the west coast of Ireland, a number of echinoderm species have been found to exhibit extreme aggregation. Population densities for some of these animals are amongst the highest on record.2. Detailed studies have been carried out on aggregations of the holothurianPseudocucumis mixtaÖstergren. These provided information on habitat preference, mode of burrowing, method of feeding and the animals sensitivity.3. In situ observation established the existence of a diurnal feeding rhythm which may be primarily controlled by light.4. The manner of defecation and the nature of the faeces would appear to rule out self-fouling by the aggregation.