Marine Hydrozoan Research Articles

Multi-domain GFP-like proteins from two species of marine hydrozoans

Proteins homologous to Green Fluorescent Protein (GFP) are widely used as genetically encoded fluorescent labels. Many developments of this technology were spurred by discoveries of novel types of GFP-like proteins (FPs) in nature. Here we report two proteins displaying primary structures never before encountered in natural FPs: they consist of multiple GFP-like domains repeated within the same polypeptide chain. A two-domain green FP (abeGFP) and a four-domain orange-fluorescent FP (Ember) were isolated from the siphonophore Abylopsis eschscholtzii and an unidentified juvenile jellyfish (order Anthoathecata), respectively. Only the most evolutionary ancient domain of Ember is able to synthesize an orange-emitting chromophore (emission at 571 nm), while the other three are purely green (emission at 520 nm) and putatively serve to maintain the stability and solubility of the multidomain protein. When expressed individually, two of the green Ember domains form dimers and the third one exists as a monomer. The low propensity for oligomerization of these domains would simplify their adoption as in vivo labels. Our results reveal a previously unrecognized direction in which natural FPs have diversified, suggesting new avenues to look for FPs with novel and potentially useful features.

A heat shock protein and Wnt signaling crosstalk during axial patterning and stem cell proliferation

Both Wnt signaling and heat shock proteins play important roles in development and disease. As such, they have been widely, though separately, studied. Here we show a link between a heat shock protein and Wnt signaling in a member of the basal phylum, Cnidaria. A heat shock at late gastrulation in the clonal marine hydrozoan, Hydractinia, interferes with axis development, specifically inhibiting head development, while aboral structures remain unaffected. The heat treatment upregulated Hsc71, a constitutive Hsp70 related gene, followed by a transient upregulation, and long-term downregulation, of Wnt signaling components. Downregulating Hsc71 by RNAi in heat-shocked animals rescued these defects, resulting in normal head development. Transgenic animals, ectopically expressing Hsc71, had similar developmental abnormalities as heat-shocked animals in terms of both morphology and Wnt3 expression. We also found that Hsc71 is upregulated in response to ectopic Wnt activation, but only in the context of stem cell proliferation and not in head development. Hsc71's normal expression is consistent with a conserved role in mitosis and apoptosis inhibition. Our results demonstrate a hitherto unknown crosstalk between heat shock proteins and Wnt/β-catenin signaling. This link likely has important implications in understanding normal development, congenital defects and cancer biology.

Green-Fluorescent Protein from the Bioluminescent Jellyfish Clytia gregaria Is an Obligate Dimer and Does Not Form a Stable Complex with the Ca2+-Discharged Photoprotein Clytin

Green-fluorescent protein (GFP) is the origin of the green bioluminescence color exhibited by several marine hydrozoans and anthozoans. The mechanism is believed to be Förster resonance energy transfer (FRET) within a luciferase-GFP or photoprotein-GFP complex. As the effect is found in vitro at micromolar concentrations, for FRET to occur this complex must have an affinity in the micromolar range. We present here a fluorescence dynamics investigation of the recombinant bioluminescence proteins from the jellyfish Clytia gregaria, the photoprotein clytin in its Ca(2+)-discharged form that is highly fluorescent (λ(max) = 506 nm) and its GFP (cgreGFP; λ(max) = 500 nm). Ca(2+)-discharged clytin shows a predominant fluorescence lifetime of 5.7 ns, which is assigned to the final emitting state of the bioluminescence reaction product, coelenteramide anion, and a fluorescence anisotropy decay or rotational correlation time of 12 ns (20 °C), consistent with tight binding and rotation with the whole protein. A 34 ns correlation time combined with a translational diffusion constant and molecular brightness from fluorescence fluctuation spectroscopy all confirm that cgreGFP is an obligate dimer down to nanomolar concentrations. Within the dimer, the two chromophores have a coupled excited-state transition yielding fluorescence depolarization via FRET with a transfer correlation time of 0.5 ns. The 34 ns time of cgreGFP showed no change upon addition of a 1000-fold excess of Ca(2+)-discharged clytin, indicating no stable complexation below 0.2 mM. It is proposed that any bioluminescence FRET complex with micromolar affinity must be one formed transiently by the cgreGFP dimer with a short-lived (millisecond) intermediate in the clytin reaction pathway.

Nematogalectin, a nematocyst protein with GlyXY and galectin domains, demonstrates nematocyte-specific alternative splicing in Hydra.

Taxonomically restricted genes or lineage-specific genes contribute to morphological diversification in metazoans and provide unique functions for particular taxa in adapting to specific environments. To understand how such genes arise and participate in morphological evolution, we have investigated a gene called nematogalectin in Hydra, which has a structural role in the formation of nematocysts, stinging organelles that are unique to the phylum Cnidaria. Nematogalectin is a 28-kDa protein with an N-terminal GlyXY domain (glycine followed by two hydrophobic amino acids), which can form a collagen triple helix, followed by a galactose-binding lectin domain. Alternative splicing of the nematogalectin transcript allows the gene to encode two proteins, nematogalectin A and nematogalectin B. We demonstrate that expression of nematogalectin A and B is mutually exclusive in different nematocyst types: Desmonemes express nematogalectin B, whereas stenoteles and isorhizas express nematogalectin B early in differentiation, followed by nematogalectin A. Like Hydra, the marine hydrozoan Clytia also has two nematogalectin transcripts, which are expressed in different nematocyte types. By comparison, anthozoans have only one nematogalectin gene. Gene phylogeny indicates that tandem duplication of nematogalectin B exons gave rise to nematogalectin A before the divergence of Anthozoa and Medusozoa and that nematogalectin A was subsequently lost in Anthozoa. The emergence of nematogalectin A may have played a role in the morphological diversification of nematocysts in the medusozoan lineage.

Reconciling genealogical and morphological species in a worldwide study of the Family Hydractiniidae (Cnidaria, Hydrozoa)

The Hydractiniidae are a family of globally distributed marine hydrozoans (class Hydrozoa, phylum Cnidaria). Despite being one of the most well‐studied families of the Hydrozoa, their genus and species‐level taxonomy is unsettled and disputed. The taxonomic difficulties of the Hydractiniidae are due to many inadequate species descriptions, a paucity of available morphological characters, many cryptic species, and the often‐extreme plasticity seen when colonies of the same species are found at different stages of growth or different environmental conditions. This confusion over species identity is especially important because some species of the family Hydractiniidae are well‐established model organisms for a wide array of studies ranging from gene expression to developmental biology and colony growth. Here we report the species‐level implications of 226 mitochondrial large ribosomal subunit (16S) rDNA sequences from around the world and 52 nuclear DNA sequences (Elongation Factor 1α) with the intent to reconcile described morphospecies with genealogical lineages.Our data show that Podocoryna carnea and P. exigua are distinct and geographically disjunct species, P. borealis is paraphyletic with respect to Podocoryna sp. from South Africa and P. bella from New Zealand. Podocoryna australis, from New Zealand form a distinct monophyletic group. Podocoryna from New England, New York and Florida all fall into a distinct monophyletic group (P. americana) and fail to support the existence of a distinct, P. selena in the Gulf of Mexico. Hydractinia pruvoti is the only species within the Podocoryna clade without fully formed medusae. We identify a Clava clade closely related to other algae dwelling Hydractiniidae. Our data do not recover Stylactaria inabai from Japan as a distinct species from S. misakiensis, and S. carcinicola as distinct from H. epiconcha. Also, 10 colonies identified as S. carcinicola fall into a distantly related clade that is close to the American S. hooperi. Finally, we identify Janaria mirabilis as the sister group to the H. echinata species complex and clarify the relationships between the H. echinata, H. symbiopollicaris, H. polyclina, H. symbiolongicarpus and H. [GM].

The ecology of protists epibiontic on marine hydroids

Several hydroid species have an epibiontic lifestyle, living associated with organisms of many different phyla. On the other hand, hydroids can also host dense assemblages of microflora and microfauna, mainly composed of protists and bacteria. Among protists, diatoms are the most abundant and diversified group, followed by foraminifera and sessile ciliata such asVorticellaand suctorians. Regarding the spatial distribution of epibionts, hydroid colonies represent a mosaic of different microhabitats: in some species, each colony portion (base of the stem, branches, pedicels, inner space between the polyp and the theca) hosts different diatom species. Moreover, three foram species have been shown to occupy different positions according to the plasticity of their shell. A host specificity has been also observed: some epibionts are typical of only one or a group of species, such asVorticellaliving on the teeth of theAglaopheniathecae or coralline algae that cover mainlyAglaopheniaandSertularellacolonies. The microassemblage associated toEudendrium racemosumshowed a typical seasonal cycle and a vertical distribution which reflects the selective advantage of the different life forms. Experiments with plastic structures miming hydroid colonies demonstrated that the living hydroid affects the assemblage structure. Probably, the perisarc composition and secondary metabolites play a crucial role in the relationships between hydroids and their microassemblage.

DNA barcoding reveals cryptic diversity in marine hydroids (Cnidaria, Hydrozoa) from coastal and deep‐sea environments

Fifty‐six sequences of the mitochondrial 16S RNA gene were generated for hydroids, belonging to six nominal families — Eudendriidae, Lafoeidae, Haleciidae, Sertulariidae, Plumulariidae and Aglaopheniidae — collected from bathyal environments of the Gulf of Cadiz (22 haplotypes), Greenland (1 haplotype), Azores (1 haplotype), the shallow waters of the UK (17 haplotypes) and Portugal (2 haplotypes). When combined and analysed with 68 additional sequences published in GenBank, corresponding to 63 nominal species of these families (nine species in common between the GenBank sequences and those presented by the authors), cryptic species were detected (e.g. two species of Nemertesia and other of Lafoea), as well as apparent cases of conspecificity (e.g. Nemertesia antennina and N. perrieri and Aglaophenia octodonta, A. pluma and A. tubiformis). Other taxonomic inconsistencies were found in the data including cases where species from different genera clustered together (e.g. Sertularia cupressina, Thuiaria thuja, Abietinaria abietina and Ab. filicula). The mitochondrial 16S rRNA proved to be a useful DNA ‘barcode’ gene for hydroids, not only allowing discrimination of species, but also in some cases of populations, genera and families, and their intra‐ or interphylogenetic associations. Although still under‐represented in public data bases, the 16S rRNA gene is starting to be used frequently in the study of hydroids. These data provide powerful complementary evidence for advancing our understanding of hydrozoan systematics.

Induction of reverse development in two marine Hydrozoans

Cnidarians are unique organisms in the animal kingdom because of their unequalled potential to undergo reverse development (RD). The life cycle of some species can temporarily shift ordinary, downstream development from zygote to adult into the opposite ontogenetic direction by back-transformation of some life stages. The potential for RD in cnidarians offers the possibility to investigate how integrative signalling networks operate to control directionality of ontogeny (reverse vs. normal development). Striking examples are found in some hydrozoans, where RD of medusa bud or liberated medusa stages leads to rejuvenation of the post-larval polyp stage. Artificial stress may determine ontogeny reversal. We describe here the results of experimental assays on artificial induction of RD by different chemical and physical inducers on two marine hydrozoans, Turritopsis dohrnii and Hydractinia carnea, showing a different potential for RD. A cascade of morphogenetic events occurs during RD by molecular mechanisms and cellular patterns recalling larval metamorphosis. For the first time, we show here that exposure to cesium chloride (CsCl), an inducer of larval metamorphosis, may also induce RD, highlighting similarities and differences between these two master ontogenetic processes in cnidarians.

Species identification of bivalve‐inhabiting marine hydrozoans of the genus Eugymnanthea

Abstract. Species‐level identification is difficult in the symbiotic bivalve‐inhabiting hydrozoans of the genus Eugymnanthea (Cnidaria, Hydrozoa). Morphological differences are detected only in the adult medusoid stage. Eugymnanthea is known only from the Mediterranean and the western Pacific, and doubt persists over whether the two localities are inhabited by different species. Because the bivalve host, Mytilus galloprovincialis, is thought to have been introduced by humans from the Mediterranean to the western Pacific, there has been speculation that the Mediterranean Eugymnanthea was also introduced along with its host. Here, we evaluate the species status of the two hydrozoan forms with breeding experiments, morphology, and two recently developed tools for discrimination: a mesoglea cell adhesion and spreading test, and 16S rDNA comparison. Reciprocal crosses of the two forms failed to produce normal offspring, providing evidence that they are indeed different species according to the biological species concept, and suggesting that the Pacific form is not an invasion of the Mediterranean form. The tissue‐grafting test failed to distinguish between the two forms, while the morphological and genetic evidence corroborated the breeding results.

Ontogenetic shifts in fusion?rejection thresholds in a colonial marine hydrozoan, Hydractinia symbiolongicarpus

Like many modular organisms, genetically distinct colonies of the hydrozoan Hydractinia symbiolongicarpus naturally fuse to produce chimeras. One of the principal cooperative benefits of fusion arises from the increased size of the resulting chimeric individual, which may enhance survivorship. However, fusion also promotes conflict through competition between cell lineages for representation in reproductive tissues. Previous studies on H. symbiologicarpus show that, consistent with kin selection theory, a highly polymorphic self/non-self recognition system limits fusion to close kin. However, these recognition systems are intrinsically subject to error. Conspecific acceptance threshold theory predicts that as the costs and benefits of making recognition errors change, or the frequencies of encounters between acceptable and unacceptable kin vary, the recognition system should respond. Specifically, as the benefits of acceptance decline or the frequency of encounters with unacceptable individuals increases, the acceptance threshold should become more restrictive. We tested this hypothesis by monitoring changes in the expression of fusion/rejection behaviors of H. symbiolongicarpus during colony establishment, a period of high mortality when the size-dependent benefits of fusion may be changing most rapidly, and the frequency of encounters with close kin declines. Across seven full-sib families, fusion frequencies between pairs of sibling colonies declined from 73% for 3-day-old colonies to 58% by day 12. This decline is consistent with optimal acceptance threshold theory. However, the period of maximum decline also corresponds to an interval during which the recognition effector mechanism becomes fully functional, suggesting that the shift to a more restrictive conspecific acceptance threshold may reflect an intrinsic constraint on recognition system maturation.

Nonlinear oscillations in marine hydroids.

Irregular oscillations in a colony of marine hydroids Podocoryne carnea were investigated. Quantitative characteristics were obtained as a result of long term (10-12 h) monitoring of oscillations at arbitrary sites. The sliding window spectra as well as the pulse-to-pulse dynamics argue the transient chaotic behavior of hydroid colony. The significant change of amplitudes and frequencies in intact colony oscillations after feeding and long sustained oscillations of stolons separated from colony suggest that the irregular activity could be determined by the network of pacemakers residing in stolon wall cells. These are influenced mechanically by the amount of digesting food and/or by chemical action of nutrients inside the stolon lumen. The possible correlation of these oscillations which can evoke Ca(2+) waves in stolon wall cells is discussed.

Taurine in the marine hydrozoan Hydractinia echinata: stabilizer of the larval state?

Taurine (β-aminoethane sulfonic acid) is present in high concentrations in tissue of planula larvae of the marine hydrozoan Hydractinia echinata. It has been proposed to function as a stabilizer of the larval state mainly because of the previous findings that larvae induced to undergo metamorphosis appeared to lose most of their taurine, and taurine added to the medium antagonizes metamorphosis. Release of taurine was assumed to be a necessary prerequisite for the onset of metamorphosis. The primary aim of the present study was to confirm this by determination of taurine release accompanying metamorphosis induction by inducers other than CsCl. However, a decrease of the larval tissue taurine content was not found, irrespective of schedule of treatment and the inducer applied. The cause for this difference from the preceding study could not be clarified. Taurine in the medium, even at low concentration, causes elevated tissue concentrations high enough to cause general adverse effects on cell physiology. In order to ascribe an alternative function to taurine in H. echinata variations of the free amino acid pool under osmotic stress were examined. The tissue concentration of β-alanine strongly correlates with the salinity of the medium. Large amounts of γ-aminobutyric acid (GABA) are present in animals adapted to high salinity. Taurine content appears not to depend on osmolarity of the medium. Nevertheless, taurine may constitute the foundation of the cellular organic osmolyte system of the H. echinata larva.

The Study of Biorhythms in Marine Colonial Hydroids

Biorhythmic activity of the colony of marine hydroids Podocoryne carnea was investigated. Quantitative characteristics were obtained as a result of the analysis of long-term (10–12 h) monitored stolon oscillations. Sliding window Fourier spectrum dynamics as well as the analysis of the system particular trajectories argue that the main feature of hydroid biorhythmic activity is transient chaos. Long-sustained cyclic activity of stolon pieces separated from the colony and the change in stolon oscillation amplitude and frequency after feeding suggest that stolon cyclic behaviour is determined by the network which consists of pacemakers residing in stolon wall cells and the amount and/or state of food particles inside the stolon lumen. The biorhythmic activity of colony from the point of chaos theory is discussed.

Effect of cloning rate on fitness-related traits in two marine hydroids.

Hydractinia symbiolongicarpus and Podocoryna carnea are colonial marine hydroids capable of reproducing both sexually and asexually. Asexual reproduction, by colony fragmentation, produces a genetic clone of the parent colony. This study examines the effect of very different cloning rates on colony growth rate, oxygen uptake rate, and colony morphology. Colonies of one clone of each species were maintained for an extended time in two treatments: in a state of constant vegetative growth by repeated cloning, and in a state restricted from vegetative growth (no cloning). For both species, tissue explants taken from the growing colonies grew more slowly than similar explants taken from the restricted colonies. For one species, tissue explants from the growing colonies used oxygen at a higher rate than similar explants from restricted colonies; for the other species, no difference was detected, although the sample size was small. For both species, tissue explants from restricted colonies formed more circular, "sheet-like" shapes, whereas those from their growing counterparts formed more irregular, "runner-like" shapes. After these experiments, in the third winter of treatment, all colonies experienced a severe tissue regression. Within 6 months after this event, the colonies had regrown to their former sizes. A growth assay at this point revealed no difference in growth rate, possibly suggesting an epigenetic basis for these results. Changes in clonal growth rates and morphology correlated with variation in fragmentation rate might affect the ecology of these and other clonal organisms.

Hydroid defenses against predators: the importance of secondary metabolites versus nematocysts.

Marine hydroids are commonly thought to be defended by stinging organelles called nematocysts that penetrate predator tissues and inject proteinaceous venoms, but not all hydroids possess these nematocysts. Although an increasing number of bioactive secondary metabolites have been isolated from marine hydroids, ecological roles of these compounds are poorly known. To test the hypothesis that nematocysts and noxious secondary metabolites represent alternative defenses against predation, we examined hydroids from North Carolina, United States for: (1) the palatability of whole polyps before and after nematocysts had been deactivated; (2) the palatability of their chemical extracts; and (3) their nutritional value in terms of organic content, protein content, and levels of refractory structural material (chitin). All hydroids were avoided by a generalist predator, the pinfish Lagodon rhomboides, compared with palatable control foods. Two of these (Halocordyle disticha and Tubularia crocea) became palatable after being treated with potassium chloride to discharge their nematocysts, suggesting that these species rely on nematocysts for defenses against predators. Chemical extracts from nematocyst-defended species had no effect on fish feeding. The four species that remained unpalatable after nematocysts had been discharged (Corydendrium parasiticum, Eudendrium carneum, Hydractinia symbiolongicarpus, Tridentata marginata) possessed chemical extracts that deterred feeding by pinfish. We have isolated and characterized the structures of the deterrent metabolites in two of these species. We found no differences in nutritional content or levels of chitin between nematocyst-defended and chemically defended species, and no evidence that either of these played a role in the rejection of hydroids as prey. Our results suggest that, among hydroids, chemical defenses may be at least as common as nematocyst-based defenses and that the two may represent largely alternative defensive strategies. The four hydroid species with deterrent extracts represent four families and both sub-orders of hydroids, suggesting that chemical defenses in this group may be widespread and have multiple origins.

A toxin homology domain in an astacin-like metalloproteinase of the jellyfish Podocoryne carnea with a dual role in digestion and development.

Metalloproteinases of the astacin family such as tolloid play major roles in animal morphogenesis. Cnidarians are thought to be evolutionary simple organisms and, therefore, a metalloproteinase from the marine hydrozoan Podocoryne carnea was analysed to evaluate the role of this conserved gene familiy at the base of animal evolution. Surprisingly, the proteinase domain of Podocornyne PMP1 is more similar to human meprin than to HMP1 from another hydrozoan, the freshwater polyp Hydra vulgaris. However, PMP1 and HMP1 both contain a small C-terminal domain with six cysteines that distinguishes them from other astacin-like molecules. Similar domains have been described only recently from sea anemone toxins specific for potassium channels. This toxin homology (Tox1) domain is clearly distinct from epidermal growth factor (EGF)-like domains or other cysteine-rich modules and terminates with the characteristic pattern CXXXCXXC with three out of six cysteines in the last eight residues of the protein. PMP1 is transiently expressed at various sites of morphogenetic activity during medusa bud development. In the adult medusa, however, expression is concentrated to the manubrium, the feeding organ, where the PMP1 gene is highly induced upon feeding. These disparate expression patterns suggest a dual role of PMP1 comparable to tolloid in development and, like astacin in the crayfish, also for food digestion. The Tox1 domain of PMP1 could serve as a toxin to keep the pray paralysed after ingestion, but as a sequence module such Tox1 domains with six cysteines are neither restricted to cnidarians nor to toxins.

Prdl-a, a gene marker for hydra apical differentiation related to triploblastic paired-like head-specific genes.

Two homeobox genes, prdl-a and prdl-b, which were isolated from a Hydra vulgaris cDNA library, encode paired-like class homeodomains highly related to that of the aristaless-related genes. In adult polyps, prdl-b is a marker for synchronously dividing nematoblasts while prdl-a displays an expression restricted to the the nerve cell lineage of the head region. During budding and apical regeneration, an early and transient prdl-a expression was observed in endodermal cells of the stump at a time when the head organizer is established. When apical regeneration was delayed upon concomittant budding, prdl-a expression was found to be altered in the stump. Furthermore, a specific anti-prdl-a protein immunoserum revealed that prdl-a was overexpressed in adult polyps of the Chlorohydra viridissima multiheaded mutant, with an expression domain extending below the tentacle ring towards the body column. Accordingly, prdl-a DNA-binding activity was enhanced in nuclear extracts from this mutant. These results suggest that prdl-a responds to apical forming signals and might thus be involved in apical specification. When a marine hydrozoan (Podocorynae carnea) was used, the anti-prdl-a antibody showed cross-reactivity with cells located around the oral region, indicating that prdl-a function is shared by other cnidaria. The ancestral role for prdl-a-related genes in the molecular definition of the head (or oral-surrounding region) is discussed.

Induction of metamorphosis of the marine Hydrozoan Hydractinia echinata fleming, 1828

The marine hydrozoan Hydractinia echinata Fleming, 1828 develops through a demersal planula larval stage. Recent work on the induction of metamorphosis of the planula has contributed greatly to understanding of the role of cell communication by signals, signal transmission, and signal transduction during metamorphosis of marine invertebrates. The purpose of this paper is to survey what is known about the natural induction of metamorphosis and to provide information on the biochemical and cellular mechanisms underlying the metamorphic events in H. echinata. A critical look at the effect of inhibitors is given, in conjunction with an hypothesis about the sequence of early events in metamorphosis.

Altruist Cheater Dynamics inDictyostelium:Aggregated Distribution Gives Stable Oscillations

Previous articleNext article No AccessAltruist Cheater Dynamics in Dictyostelium: Aggregated Distribution Gives Stable OscillationsAnagha K. Matapurkar and Milind G. WatveAnagha K. MatapurkarLife Research Foundation, 10 Pranav, 1000/6‐c, Navi Peth, Pune 411 030, India Search for more articles by this author and Milind G. WatveLife Research Foundation, 10 Pranav, 1000/6‐c, Navi Peth, Pune 411 030, India Search for more articles by this author Life Research Foundation, 10 Pranav, 1000/6‐c, Navi Peth, Pune 411 030, IndiaPDFPDF PLUS Add to favoritesDownload CitationTrack CitationsPermissionsReprints Share onFacebookTwitterLinkedInRedditEmail SectionsMoreDetailsFiguresReferencesCited by The American Naturalist Volume 150, Number 6December 1997 Published for The American Society of Naturalists Article DOIhttps://doi.org/10.1086/286094 Views: 44Total views on this site Citations: 16Citations are reported from Crossref HistoryReceived December 19, 1996 June 9, 1997Accepted June 9, 1997 © 1997 by The University of Chicago.PDF download Crossref reports the following articles citing this article:Leonardo Miele, Silvia De Monte, Corina E. Tarnita Aggregative cycles evolve as a solution to conflicts in social investment, PLOS Computational Biology 17, no.11 (Jan 2021): e1008617.https://doi.org/10.1371/journal.pcbi.1008617Samay Pande, Pau Pérez Escriva, Yuen-Tsu Nicco Yu, Uwe Sauer, Gregory J. Velicer Cooperation and Cheating among Germinating Spores, Current Biology 30, no.2323 (Dec 2020): 4745–4752.e4.https://doi.org/10.1016/j.cub.2020.08.091Anya E. Vostinar, Heather J. Goldsby, Charles Ofria Suicidal selection: Programmed cell death can evolve in unicellular organisms due solely to kin selection, Ecology and Evolution 9, no.1616 (Jul 2019): 9129–9136.https://doi.org/10.1002/ece3.5460H. R. Votaw, E. A. Ostrowski Stalk size and altruism investment within and among populations of the social amoeba, Journal of Evolutionary Biology 30, no.1111 (Sep 2017): 2017–2030.https://doi.org/10.1111/jeb.13172Milind Watve Why Population Density Matters, (Jul 2012): 185–202.https://doi.org/10.1007/978-1-4614-4409-1_9Joan E. Strassmann, David C. Queller How social evolution theory impacts our understanding of development in the social amoeba Dictyostelium, Development, Growth & Differentiation 53, no.44 (May 2011): 597–607.https://doi.org/10.1111/j.1440-169X.2011.01272.xMilind G Watve, Anuja Damle, Bratati Ganguly, Anagha Kale, Neelesh Dahanukar Blackmailing: the keystone in the human mating system, BMC Evolutionary Biology 11, no.11 (Jan 2011): 345.https://doi.org/10.1186/1471-2148-11-345Neil J. Buttery, Daniel E. Rozen, Jason B. Wolf, Christopher R.L. Thompson Quantification of Social Behavior in D. discoideum Reveals Complex Fixed and Facultative Strategies, Current Biology 19, no.1616 (Aug 2009): 1373–1377.https://doi.org/10.1016/j.cub.2009.06.058Tejashree Modak, Shalmali Pradhan, Milind Watve Sociobiology of biodegradation and the role of predatory protozoa in biodegrading communities, Journal of Biosciences 32, no.44 (Jul 2007): 775–780.https://doi.org/10.1007/s12038-007-0078-0Owen M. Gilbert, Kevin R. Foster, Natasha J. Mehdiabadi, Joan E. Strassmann, David C. Queller High relatedness maintains multicellular cooperation in a social amoeba by controlling cheater mutants, Proceedings of the National Academy of Sciences 104, no.2121 (May 2007): 8913–8917.https://doi.org/10.1073/pnas.0702723104Å Brännström, U Dieckmann Evolutionary dynamics of altruism and cheating among social amoebas, Proceedings of the Royal Society B: Biological Sciences 272, no.15721572 (Jul 2005): 1609–1616.https://doi.org/10.1098/rspb.2005.3116Alex C. C. Wilson, Richard K. Grosberg Ontogenetic shifts in fusion?rejection thresholds in a colonial marine hydrozoan, Hydractinia symbiolongicarpus, Behavioral Ecology and Sociobiology 57, no.11 (Aug 2004): 40–49.https://doi.org/10.1007/s00265-004-0831-4Francesca Fiegna, Gregory J. Velicer Competitive fates of bacterial social parasites: persistence and self–induced extinction of Myxococcus xanthus cheaters, Proceedings of the Royal Society of London. Series B: Biological Sciences 270, no.15231523 (Jul 2003): 1527–1534.https://doi.org/10.1098/rspb.2003.2387 Richard Ellis Hudson , Juliann Eve Aukema , Claude Rispe , and Denis Roze Altruism, Cheating, and Anticheater Adaptations in Cellular Slime Molds. R. E. Hudson et al., The American Naturalist 160, no.11 (Jul 2015): 31–43.https://doi.org/10.1086/340613Gregory J. Velicer, Lee Kroos, Richard E. Lenski Developmental cheating in the social bacterium Myxococcus xanthus, Nature 404, no.67786778 (Apr 2000): 598–601.https://doi.org/10.1038/35007066Michael W. Hart, Richard K. Grosberg KIN INTERACTIONS IN A COLONIAL HYDROZOAN ( HYDRACTINIA SYMBIOLONGICARPUS ): POPULATION STRUCTURE ON A MOBILE LANDSCAPE, Evolution 53, no.33 (May 2017): 793–805.https://doi.org/10.1111/j.1558-5646.1999.tb05373.x

EVOLUTIONARY GENETICS OF ALLORECOGNITION IN THE COLONIAL HYDROID HYDRACTINIA SYMBIOLONGICARPUS.

Many sedentary, clonal marine invertebrates compete intensively with conspecifics for habitable space. Allorecognition systems mediate the nature and outcome of these intraspecific competitive interactions, such that the initiation of agonistic behavior and the potential for intergenotypic fusion depend strongly on the relatedness of the contestants. The dependence of these behaviors on relatedness, along with the extraordinary precision with which self can be discriminated from nonself, suggest that allorecognition systems are highly polymorphic genetically. However, allotypic specificity of this sort could be produced by any number of genetic scenarios, ranging from relatively few loci with abundant allelic variation to numerous loci with relatively few alleles per locus. At this point, virtually nothing is known of the formal genetics of allorecognition in marine invertebrates; consequently, the evolutionary dynamics of such systems remain poorly understood. In this paper, we characterize the formal genetics of allorecognition in the marine hydrozoan Hydractinia symbiolongicarpus. Hydractinia symbiolongicarpus colonizes gastropod shells occupied by hermit crabs. When two or more individuals grow into contact, one of three outcomes ensues: fusion (compatibility), transitory fusion (a temporary state of compatibility), and rejection (incompatibility, often accompanied by the production of agonistic structures termed hyperplastic stolons). Observed patterns of compatibility between unrelated, half-sib pairs, and full-sib pairs show that unrelated and half-sib pairs under laboratory culture have a very low probability of being fusible, whereas full sibs have a roughly 30% rate of fusion in experimental pairings. The genetic simulations indicate that roughly five loci, with 5-7 alleles per locus, confer specificity in this species. In ecological terms, the reproductive ecology of H. symbiolongicarpus should promote the cosettlement of kin, some of which should be full sibs, and some half sibs. Thus, there is potential for kin selection to play a major role in the evolution of the H. symbiolongicarpus allorecognition system. In genetic terms, this system conforms to theoretical predictions for a recognition system selected to distinguish among classes of kin, in addition to self from nonself.