The biology and life cycle of the Rhizocephala (Cirripedia)

Høeg, Jens T.

doi:10.1017/s0025315400038996

Cited by 202 publications

(204 citation statements)

References 90 publications

(150 reference statements)

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“…Myxozoa | Cnidaria | Polypodium | parasite | genome evolution O bligate parasitism can lead to dramatic reduction of body plans and associated morphological structures (1,2). One of the most spectacular examples is the microscopic Myxozoa, which spend most of their parasitic life cycle as just a few cells in size (3).…”

mentioning

confidence: 99%

Genomic insights into the evolutionary origin of Myxozoa within Cnidaria

Chang

Neuhof

Rubinstein

et al. 2015

Proc. Natl. Acad. Sci. U.S.A.

219

304

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The Myxozoa comprise over 2,000 species of microscopic obligate parasites that use both invertebrate and vertebrate hosts as part of their life cycle. Although the evolutionary origin of myxozoans has been elusive, a close relationship with cnidarians, a group that includes corals, sea anemones, jellyfish, and hydroids, is supported by some phylogenetic studies and the observation that the distinctive myxozoan structure, the polar capsule, is remarkably similar to the stinging structures (nematocysts) in cnidarians. To gain insight into the extreme evolutionary transition from a free-living cnidarian to a microscopic endoparasite, we analyzed genomic and transcriptomic assemblies from two distantly related myxozoan species, Kudoa iwatai and Myxobolus cerebralis, and compared these to the transcriptome and genome of the less reduced cnidarian parasite, Polypodium hydriforme. A phylogenomic analysis, using for the first time to our knowledge, a taxonomic sampling that represents the breadth of myxozoan diversity, including four newly generated myxozoan assemblies, confirms that myxozoans are cnidarians and are a sister taxon to P. hydriforme. Estimations of genome size reveal that myxozoans have one of the smallest reported animal genomes. Gene enrichment analyses show depletion of expressed genes in categories related to development, cell differentiation, and cell-cell communication. In addition, a search for candidate genes indicates that myxozoans lack key elements of signaling pathways and transcriptional factors important for multicellular development. Our results suggest that the degeneration of the myxozoan body plan from a free-living cnidarian to a microscopic parasitic cnidarian was accompanied by extreme reduction in genome size and gene content.Myxozoa | Cnidaria | Polypodium | parasite | genome evolution

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mentioning

confidence: 99%

Genomic insights into the evolutionary origin of Myxozoa within Cnidaria

Chang

Neuhof

Rubinstein

et al. 2015

Proc. Natl. Acad. Sci. U.S.A.

219

304

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“…Female cyprids of the parasite settle on R. harrisii megalopae (Walker et al, 1992), causing sterilization of both adult males and females (Ritchie and Hoeg, 1981;Hoeg, 1995). However, infection by the parasite does not cause mortality in adult crabs when they are acclimated to salinities from 0 to 30 ppt.…”

Section: Larval Releasementioning

confidence: 99%

Larval Biology of the CrabRhithropanopeus harrisii(Gould): A Synthesis

Forward

2009

The Biological Bulletin

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Abstract. This synthesis reviews the physiological ecology and behavior of larvae of the benthic crab Rhithropanopeus harrisii, which occurs in low-salinity areas of estuaries. Larvae are released rhythmically around the time of high tide in tidal estuaries and in the 2-h interval after sunset in nontidal estuaries. As in most subtidal crustaceans, the timing of larval release is controlled by the developing embryos, which release peptide pheromones that stimulate larval release behavior by the female to synchronize the time of egg hatching. Larvae pass through four zoeal stages and a postlarval or megalopal stage that are planktonic before metamorphosis. They are retained near the adult population by means of an endogenous tidal rhythm in vertical migration. Larvae have several safeguards against predation: they undergo nocturnal diel vertical migration (DVM) and have a shadow response to avoid encountering predators, and they bear long spines as a deterrent. Photoresponses during DVM and the shadow response are enhanced by exposure to chemical cues from the mucus of predator fishes and ctenophores. The primary visual pigment has a spectral sensitivity maximum at about 500 nm, which is typical for zooplankton and matches the ambient spectrum at twilight. Larvae can detect vertical gradients in temperature, salinity, and hydrostatic pressure, which are used for depth regulation and avoidance of adverse environmental conditions. Characteristics that are related to the larval habitat and are common to other crab larval species are considered.

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“…The aperture is acquired at the second externa molt, whereafter male cyprids are attracted to the externa, probably by a pheromone emanating from the receptacles (Høeg, 1995). This short-distance cheFigs.…”

Section: Kentrogonidamentioning

confidence: 99%

“…They range from the minimal effects of Chthamalophilidae to the extensive "host control" exhibited by the Sacculinidae, whereby host molting/growth as well as reproduction are all severely compromised. The effects on the host can include cessation of molting, parasitic sterilization, feminization, and "egg-mimicry" behavior (see Høeg, 1995).…”

Section: Akentrogonidamentioning

confidence: 99%

“…Høeg) and others have instigated a renaissance in rhizocephalan research, which continues apace. This renaissance stemmed not only from pure interest in the group but the desire to apply modern techniques that have yielded startling new discoveries within the already intricate life-cycles, in the ultrastructural morphology of the larvae, systematics, and evolution, as well as the physiological effects on their crustacean hosts (see Høeg, 1992bHøeg, , 1995Lü tzen, 1995, 1996).…”

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confidence: 99%

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