Littoral Distributions and Evidence For Differential Post-Settlement Selection of the Morphs of <i>Actinia Equina</i>

Quicke, Donald L. J.; Donoghue, Ann M.; Keeling, T. F.; Brace, R. C.

doi:10.1017/s0025315400060768

Cited by 28 publications

(34 citation statements)

References 25 publications

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“…The horizontal, starch gel electrophoretic techniques employed to separate and stain for these enzymes, and our interpretations of banding patterns resolved, have been described previously Quicke et al 1985). Two allelic variants were found at both Hk-i and Mdh.…”

Section: Isozyme Variationmentioning

confidence: 91%

“…DISCUSSION Three morphs have been previously distinguished amongst anemones obtained from Burniston displaying red to brown column coloration. The U and L morphs are both homozygous, and the M morph heterozygous, for a co-adapted gene complex (multi-locus genotype) which includes (i) loci involved in PDC determination and (ii) several polymorphic enzyme loci (Hk-i, Mdh and To-i) Quicke et al 1985). Anemones of the U and M morph display PDC ranging from DRd to P, a feature which could be explained by a gene-dosage effect.…”

Section: Number Of Acrorhagimentioning

confidence: 99%

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Biochemical-Genetic and Acrorhagial Characteristics of Pedal Disc Colour Phenotypes of Actinia Equina

1985

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An examination has been made of pedal colour phenotypes exhibited by the three morphs of the anemone, Actinia equina L., which are distinguishable on the basis of allelic identity at two enzyme loci. The U (upper mid shore) and M (lower mid shore) morphs have pedal discs ranging in colour from red to pink, whereas the L (low shore) morph displays a grey to green pedal disc. Significant differences in the proportions of U and M morphs were found between samples of anemones having red and pink pedal discs, obtained from Burniston, N. Yorkshire, but these were not sufficiently clear cut to permit visual separation of the two morphs. Neither the pink nor red, pedal disc colour categories were comprised solely of anemones of one morph.A comparison of acrorhagial features (size, type, colour and number) between samples of anemones displaying various pedal disc colours, has shown that they are clearly divisible into three groups with respect to pedal coloration: (1) dark red; (2) light red and pink;(3) gr e y and green (with or without contrasting radial lines). In the absence of isozyme data relating to anemones possessing different acrorhagial features, it is not possible at present to state whether or not these characteristics will prove to be of assistance in visually distinguishing between the U and M morphs.It is cautioned that the differences discerned in characteristics could be related to, and modified by, the incidence of aggressive encounters within each of the pedal disc colour groups. I N T R O D U C T I O NPrevious work has shown that three ecologically disinct morphs can be identified amongst beadlet anemones, Actinia equina L., ranging in column coloration from red to brown (Quicke, Donoghue & Brace, 1983;Quicke & Brace, 1984;Quicke et al. 1985). Each is adapted to a different inter-tidal range, and is characterized by a multi-locus gene complex, which includes loci encoding a number of metabolically important enzymes, pedal disc coloration and probably strength of pedal attachment. They have been named the upper (U), mid (M) and lower (L) shore morphs, and are relatively most abundant on the upper mid, lower mid and low shores respectively. Members of the U morph are typically homozygous slow and fast at a hexokinase locus and a malate dehydrogenase locus respectively, whereas those of the L morph are typically homozygous for the other allele at each of these loci; M morph individuals are heterozygous at both.We have found that pedal disc coloration may be used to distinguish the majority of L morph individuals from members of the other two. L individuals

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Section: Isozyme Variationmentioning

confidence: 91%

Section: Number Of Acrorhagimentioning

confidence: 99%

Biochemical-Genetic and Acrorhagial Characteristics of Pedal Disc Colour Phenotypes of Actinia Equina

1985

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“…Corresponding frequencies for those recolonists which were juveniles when first detected, were of similar magnitude: 0 8 4 and 0 8 2 . These alleles are characteristic of the homozygous gene complex of the U morph, which at Worm's Head extends well down the shore on vertical rock faces, upon which, larger anemones in particular have a selective advantage over L morph individuals by adhering relatively more firmly (see p. 24; Quicke et al 1985).…”

Section: W S////y>>^_mentioning

confidence: 99%

“…The shore concerned was at Burniston (North Yorkshire), a locality with which we are similarly, already familiar Quicke, Donoghue & Brace, 1983;Quicke et al 1985).…”

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confidence: 99%

Dynamics of Colonization by the Beadlet Anemone,Actinia Equina

Brace

Quicke

1986

J. Mar. Biol. Ass.

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Recolonization of a relatively flat, vertical, low shore rock face in an exposed location (The Worm's Head, West Glamorgan) in South Wales, was monitored, at approximately two-monthly intervals, over a two-year period (1981-3), following the experimental removal of part of an aggregation of Actinia equina L. Recolonization was primarily brought about by apparently random, juvenile settlement; encroachment by either the immigration of adjacent residents or the local settlement of their brooded young was not marked.Allele frequencies among juvenile recolonists and the original occupants at two enzyme loci (Hk-i, Mdh), were similar, but differed considerably from those in adjacent populations inhabiting different niches. These findings suggest the existence of strong, post-settlement selection. Examination of the positions of both the original occupants and recolonists revealed that slightly elevated portions of the rock were, and largely remained, uncolonized. This is interpreted as indicating that juveniles settling on these areas are particularly susceptible to dislodgement. Pooled survivorship data for cohorts of recolonizing juveniles yielded a mean longevity of 3-19 years; adult survivorship at this site, though, was far in excess of this. Investigation of the movements of the former revealed a number of negative correlations with size.Recruitment and loss peaked in autumn and winter respectively; loss was principally due to juvenile mortality. Similar peaks were apparent in data drawn from part of the still resident aggregation. Brooding at The Worm's Head was maximal in late summer, with ensuing reductions corresponding well with peaks in settlement. Concurrent monitoring of an aggregation at Burniston, on the north-east coast of Britain, revealed comparable seasonal trends, though there was an indication that maxima in both recruitment and loss occurred earlier. Throughout most of the year, however, a greater proportion of adults were brooding, a difference probably largely attributable to the less severe buffeting experienced on this semi-exposed shore.It is argued that the internal brooding of apparently apomictically produced young endows A. equina with two important attributes, which are collectively necessary for colonization of, and survival in, the patchy, temporally unstable and rigorous, mid shore environment: (1) the more or less continuous production of small, but viable modules which can effect dispersal to suitable neighbouring patches in addition to sites immediately adjacent to parents, and (2) the ability of successful genotypes to undergo local multiplication under favourable environmental circumstances. Further, it is tentatively postulated that there has been suppression of sexual reproduction in this species, in which brooding is clearly of great survival value, in response to the need to avoid unfavourable allogeneic interactions. The life history features elucidated so far are discussed from a bet-hedging viewpoint.

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“…A. equina is most abundant on the lower shore, particularly on exposed coasts, but is also found on the middle and upper shore, especially in rock pools, as well as in damp crevices. Upper and lower distributional limits of mean low water springs (MLWS) and mean high water neaps (MHWN) were given by Quicke et al (1985), indicating that the species is an intertidal specialist (though it is subtidal in the microtidal Mediterranean; Chintiroglou & Koukouras 1992). Much of its biology was reviewed by Shick (1991).…”

Section: Introductionmentioning

confidence: 99%

Common sea anemones Actinia equina are predominantly sessile intertidal scavengers

Davenport¹,

Moloney²,

Kelly³

2011

Mar. Ecol. Prog. Ser.

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Coelenteron contents of anemones Actinia equina collected from 2 shore heights (upper and lower) on 3 shores (exposed, semi-exposed and sheltered) in south-west Ireland were investigated in summer 2009. Diets of exposed and semi-exposed shore anemones were dominated by small mussels Mytilus edulis, mostly (> 90%) with broken/cracked shells. The diet of anemones on the sheltered shore was dominated by insects, particularly on the upper shore. On all shores, larger food items (isopods, mussels, insects) were broken or fragmented; only small gammarid amphipods, crab megalopae, midges and mosquitos were found whole. Laboratory behavioural experiments showed that A. equina were unselective at small prey size, but were limited by their own size, which restricted the maximum size of prey that could be ingested. Whole mussels were ingested, but egested alive after mean elapsed times of 0.75 to 1.95 h (depending upon anemone size). In contrast, mussels with cut adductor muscles, and incapable of shell valve closure, were fully digested, empty shells not being egested until 8.70 to 8.95 h after ingestion. Whole, live mealworms Tenebrio molitor were eaten by anemones, but were egested after a mean 1.30 h with no signs of digestion or fragmentation. Mealworms with mechanically perforated exoskeletons were held in the coelenterons of A. equina for a mean of 5.90 h and all soft tissues were digested. It was concluded that A. equina predominantly scavenges on macrofaunal carrion, as well as preying upon smaller food items.

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Littoral Distributions and Evidence For Differential Post-Settlement Selection of the Morphs of Actinia Equina

Cited by 28 publications

References 25 publications

Biochemical-Genetic and Acrorhagial Characteristics of Pedal Disc Colour Phenotypes of Actinia Equina

Biochemical-Genetic and Acrorhagial Characteristics of Pedal Disc Colour Phenotypes of Actinia Equina

Dynamics of Colonization by the Beadlet Anemone,Actinia Equina

Common sea anemones Actinia equina are predominantly sessile intertidal scavengers

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