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Coral barnacles: Cenozoic decline and extinction in the Atlantic/East Pacific versus diversification in the Indo-West Pacific

Proceedings of the 9th Int. Coral Reef Symposium, Bali, Indonesia 01/2002; I.

ABSTRACT

The pyrgomatid coral barnacles, first appearing in the late Oligocene of the western Atlantic, underwent a Miocene diversification unparalleled by any other group of sessile barnacles. Diversification in the Indo- Pacific (eastern Tethys) coincided with retreat of the tropics from higher latitudes, especially in the Atlantic. Fragmentation of the tropics, due to the breakup of the Tethys seaway, and wholesale extinctions of their host corals beginning in the Oligocene of Europe, Mediterranean and eastern Pacific resulted in relictual distributions and regional endemism. This was followed by Neogene extinctions of many host coral genera in the western Atlantic which were not replaced by originations. The exceptional diversity of pyrgomatids now evident in the Indo-Pacific was tied to the survival and radiation of the corals found there. Curiously, our knowledge of pyrgomatid numbers and diversity has shifted from the Indonesian to peripheral centers of distribution.

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    • "Fossil pyrgomatines are known from the late Miocene, Pleistocene, and Holocene of the IWP. All pyrgomatine fossils have been classed into extant species of Pyrgomatini (Asami & Yamaguchi, 1997; Ross & Newman, 2002a). The Megatrematinae Holthuis 1982 is a small subfamily (4 genera, 6 extant species; Table 1) distributed in the WA, IWP, and East Atlantic (EA). "
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    ABSTRACT: Pyrgomatid barnacles are a family of balanomorphs uniquely adapted to symbiosis on corals. The evolution of the coral-dwelling barnacles is explored using a multi-gene phylogeny (COI, 16S, 12S, 18S, and H3) and phenotypic trait-mapping. We found that the hydrocoral associate Wanella should be excluded, while some archaeobalanids in the genus Armatobalanus should be included in the Pyrgomatidae. Three well supported clades were recovered: clade I is the largest group and is exclusively Indo-West Pacific, clade II contains two plesiomorphic Indo-West Pacific genera, while clade III is comprised of East and West Atlantic taxa. Some genera did not form reciprocally monophyletic groups, while the genus Trevathana was found to be paraphyletic and to include members of three other apomorphic genera/tribes. The highly unusual coral-parasitic hoekiines appear to be of recent origin and rapidly evolving from Trevathana sensu lato. Pyrgomatids include six-, four-, and one-plated forms, and exhibit convergent evolutionary tendencies towards skeletal reduction and fusion, loss of cirral armature, and increased host specificity. © 2014 The Linnean Society of London, Biological Journal of the Linnean Society, 2014, ●●, ●●–●●.
    Full-text · Article · Aug 2014 · Biological Journal of the Linnean Society
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    • "The coralinhabiting barnacles of the sub-family Pyrgomatinae are obligatory symbionts of scleractinian corals in the Indo-Pacific. There are more than 70 nominal species of coral-inhabiting barnacles in the family Pyrgomatidae (Ross and Newman, 2003); a number that is now rising due to use of modern research technologies such as resolution morphology techniques (SEM) and molecular analysis (Mokady et al., 1999; Mokady and Brickner, 2001; Simon-Blecher et al., 2007; Achituv et al., 2009; Chan et al., 2009). The study of life-history strategies integrates physiological, morphological, and behavioral traits in order to explain how different mechanisms allocate finite resources to maintenance, growth and reproduction, under both predictable and unpredictable environments. "
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    ABSTRACT: Barnacles are one of the most common and well-studied groups in marine ecology. In the Gulf of Eilat, the barnacle assemblages in the subtidal zone are dominated by epibionts, inhabiting stony corals, hydrozoans and sponges. Pyrgomatidae barnacles are obligatory symbionts of scleractinian corals and hydrozoans. For many organisms there is a relationship between life strategies, as predicted by the r–K selection theory, and degree of habitat specialization. Earlier studies have suggested that coral-inhabiting barnacles exhibit a tendency towards the r-endpoint. In the present research we studied the life strategy of two pyrgomatidae: Trevathana sarae, a host specialist; and Cantelius pallidus, considered a host generalist, both of which occur on the same coral host, Cyphastrea chalcidicum. Our results indicate that the two species of barnacles present two different life strategies. T. sarae fits more into the K-strategy model: a slow development, late maturity (2 years), long life span (6 years), large embryos 440 μ, and a low number of propagules (ca. 40). In contrast, C. pallidus exhibits the r-selected traits: a fast development, early maturity (1 year), short life span (2 years), small embryos 270 μ, and a high number of propagules (ca. 300). These findings support the hypothesis that associates the tendency of a species strategy towards the r-or K-endpoint with the degree of habitat specialization. Furthermore, the results highlight the diversity of life strategies existing in the Pyrgomatidae.
    Full-text · Article · Aug 2010 · Journal of Experimental Marine Biology and Ecology
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    • "The pyrgomatid (Crustacea, Cirripedia, Thoracica) genus Cantellius is the most speciose genus of its family, with 22 nominal species presently known (Ross & Newman 2000). Cantellius shows the most plesiomorphic characteristics within the coral-inhabiting barnacles, four shell wall plates and unmodified balanoid-type opercular valves. "
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    ABSTRACT: Two species of Cantellius from Taiwan were identified from the elephant skin coral, Pachyseris speciosa Dana, 1846, Cantellius sextus was found on the underside of the coral plate and a new species, C. hoegi sp. nov., on the upper surface. The microdistribution indicates the different requirements of the two species. In the present study, both arthropodal and opercular plate characters of these two species were investigated using SEM techniques. Morphologically, C. hoegi is close to C. pallidas. However, the tergal scutal margins of C. pallidas are curved, whilst those of C. hoegi are straight, and its spur is narrower than that of C. pallidas. The apex of the scutum and tergum of C. hoegi forms a honeycomb-like surface, most probably the 'imprint' of the chitinous primordial valves. The separation of C. hoegi from C. pallidas is also supported by molecular analyses of three mitochondrial gene sequences (COI, 16S, and 12S rRNA). Cantellius hoegi differs from C. pallidas and C. sextus by >5% in all three mitochondrial genes (COI, 16S, and 12S rRNA) sequenced. The values of sequence divergence in 12S are comparable to the inter-specific divergence reported for other Cantellius and Savignium species. Interestingly, C. hoegi is not the sister group of C. pallidas, a morphologically similar species, in the present study. Further studies should focus on molecular phylogenetic analysis of Cantellius species.
    Full-text · Article · Feb 2009 · Zootaxa
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