Post-embryonic larval development and metamorphosis of the hydroidEudendrium racemosum (Cavolini) (Hydrozoa,Cnidaria)

The morphology and histology of the planula larva ofEudendrium racemosum (Cavolini) and its metamorphosis into the primary polyp are described from light microscopic observations. The planula hatches as a differentiated gastrula. During the lecithotrophic larval period, large ectodermal mucous cells, embedded between epitheliomuscular cells, secrete a sticky slime. Two granulated cell types occur in the ectoderm that are interpreted as secretory and sensorynervous cells, but might also be representatives of only one cell type with a multiple function. The entoderm consists of yolk-storing gastrodermal cells, digestive gland cells, interstitial cells, cnidoblasts, and premature cnidocytes. The larva starts metamorphosis by affixing its blunt aboral pole to a substratum. While the planula flattens down, the mucous cells penetrate the mesolamella and migrate through the entoderm into the gastral cavity where they are lysed. Subsequently, interstitial cells, cnidoblasts, and premature cnidocytes migrate in the opposite direction, i.e. from entoderm to ectoderm. Then, the polypoid body organization, comprising head (hydranth), stem and foot, all covered by peridermal secretion, becomes recognisable. An oral constriction divides the hypostomal portion of the gastral cavity from the stomachic portion. Within the hypostomal entoderm, cells containing secretory granules differentiate. Following growth and the multiplication of tentacles, the head periderm disappears. A ring of gland cells differentiates at the hydranth's base. The positioning of cnidae in the tentacle ectoderm, penetration of the mouth opening and the multiplication of digestive gland cells enable the polyp to change from lecithotrophic to planktotrophic nutrition.     

Localized Organic Binding of Radioiodine in Hydra

Radioiodine, given as the iodide, localized in protein-bound form in the ectoderm of Hydra fusca and H. littoralis. The radioiodine was shown by autoradiography to be: (1) diffusely distributed in the ectoderm over the gonads and (2) precisely localized in the apical cytoplasm of cnidoblasts that carry stenotele nematocysts. The meaning of such precise cellular localization of iodoprotein in Hydra remains to be determined.     

Glycosaminoglycans in Hydra magnipapillata (Hydrozoa, Cnidaria): demonstration of chondroitin in the developing nematocyst, the sting organelle, and structural characterization of glycosaminoglycans

The hydrozoan is the simplest organism whose movements are governed by the neuromuscular system, and its de novo morphogenesis can be easily induced by the removal of body parts. These features make the hydrozoan an excellent model for studying the regeneration of tissues in vivo, especially in the nervous system. Although glycosaminoglycans (GAGs) and proteoglycans (PGs) have been implicated in the signaling functions of various growth factors and play critical roles in the development of the central nervous system, the isolation and characterization of GAGs from hydrozoans have never been reported. Here, we characterized GAGs of Hydra magnipapillata. Immunostaining using anti-GAG antibodies showed chondroitin or chondroitin sulfate (CS) in the developing nematocyst, which is a sting organelle specific to cnidarians. The CS-PGs might furnish an environment for assembling nematocyst components, and might themselves be components of nematocysts. Therefore, GAGs were isolated from Hydra and their structural features were examined. A considerable amount of CS, three orders of magnitude less heparan sulfate (HS), but no hyaluronan were found, as in Caenorhabditis elegans. Analysis of the disaccharide composition of HS revealed glucosamine 2-N-sulfation, glucosamine 6-O-sulfation, and uronate 2-O-sulfation. CS contains not only nonsulfated and 4-O-sulfated N-acetylgalactosamine (GalNAc) but also 6-O-sulfated GalNAc. The average molecular size of CS and HS was 110 and 10 kDa, respectively. It has also been established here that CS chains are synthesized on the core protein through the ubiquitous linkage region tetrasaccharide, suggesting that indispensable functions of the linkage region in the synthesis of GAGs have been conserved during evolution.     

A modified view on octocorals: Heteroxenia fuscescens nematocysts are diverse, featuring both an ancestral and a novel type

Cnidarians are characterized by the presence of stinging cells containing nematocysts, a sophisticated injection system targeted mainly at prey-capture and defense. In the anthozoan subclass Octocorallia nematocytes have been considered to exist only in low numbers, to be small, and all of the ancestral atrichous-isorhiza type. This study, in contrast, revealed numerous nematocytes in the octocoral Heteroxenia fuscescens. The study demonstrates the applicability of cresyl-violet dye for differential staining and stimulating discharge of the nematocysts. In addition to the atrichous isorhiza-type of nematocysts, a novel type of macrobasic-mastigophore nematocysts was found, featuring a shaft, uniquely comprised of three loops and densely packed arrow-like spines. In contrast to the view that octocorals possess a single type of nematocyst, Heteroxenia fuscescens features two distinct types, indicating for the first time the diversification and complexity of nematocysts for Octocorallia.     

Convergent origins and rapid evolution of spliced leader trans-splicing in Metazoa: Insights from the Ctenophora and Hydrozoa

Replacement of mRNA 5′ UTR sequences by short sequences trans-spliced from specialized, noncoding, spliced leader (SL) RNAs is an enigmatic phenomenon, occurring in a set of distantly related animal groups including urochordates, nematodes, flatworms, and hydra, as well as in Euglenozoa and dinoflagellates. Whether SL trans-splicing has a common evolutionary origin and biological function among different organisms remains unclear. We have undertaken a systematic identification of SL exons in cDNA sequence data sets from non-bilaterian metazoan species and their closest unicellular relatives. SL exons were identified in ctenophores and in hydrozoan cnidarians, but not in other cnidarians, placozoans, or sponges, or in animal unicellular relatives. Mapping of SL absence/presence obtained from this and previous studies onto current phylogenetic trees favors an evolutionary scenario involving multiple origins for SLs during eumetazoan evolution rather than loss from a common ancestor. In both ctenophore and hydrozoan species, multiple SL sequences were identified, showing high sequence diversity. Detailed analysis of a large data set generated for the hydrozoan Clytia hemisphaerica revealed trans-splicing of given mRNAs by multiple alternative SLs. No evidence was found for a common identity of trans-spliced mRNAs between different hydrozoans. One feature found specifically to characterize SL-spliced mRNAs in hydrozoans, however, was a marked adenosine enrichment immediately 3′ of the SL acceptor splice site. Our findings of high sequence divergence and apparently indiscriminate use of SLs in hydrozoans, along with recent findings in other taxa, indicate that SL genes have evolved rapidly in parallel in diverse animal groups, with constraint on SL exon sequence evolution being apparently rare.     

Taxonomy and distribution of the hydrozoan and protozoan epibionts on Pagurus bernhardus (Linnaeus, 1758) (Crustacea, Decapoda) from Scotland

Protozoan and hydrozoan epibionts on the hermit crab Pagurus bernhardus and its shell, collected near Cumbrae Island (Scotland) were studied. The epibionts found were the following: (1) protozoans: the suctorian ciliates Ephelota plana, Acineta compressa, Conchacineta constricta, Corynophrya anisostyla; the peritrich ciliates Cothurnia mobiusi and Zoothamnium plumula; the chonotrich ciliate Chilodochona quennerstedti; and (2) hydrozoans: the species Leuckartiara sp. and Clytia sp. The morphological characteristics of the epibionts were analysed, as well as their taxonomic position. The distribution of epibionts on the crab surface and its shell was studied, and the density and biomass of epibionts were calculated on each anatomic unit. There was a differential distribution according to the type of epibiont: hydrozoans dominated in biovolume and were present mainly on the shell, meanwhile protozoans represented the highest fraction of density and they were found exclusively on the crab (principally on eyes, antennulae, antennae, maxillipeds, pereopods and uropods). The anterior area of the cephalothorax was the most colonized. On this area, the maxillipeds and second pereopods showed the highest densities. The location of each epibiont species was described. There was a correlation between the length of the crab and the total number of hydrozoans. There was a significant correlation between the right and the left units of the crab, taking into consideration the mean densities of epibionts on each anatomical unit. The shell was colonized by the same species of hydrozoa that appeared on the crab, although in a much higher density (mean 3024.38 per shell; 6.9 per crab). There was a significant difference between both species of hydrozoan epibionts with respect to the mean densities on the different areas of the shell. The zone of the shell more occupied by Clytia sp. was the apical zone of the shell, while the highest densities of Leuckartiara sp. were registered near the aperture of the shell. The hydrozoan and protozoan epibiont species found on P. bernhardus in this study represent the first mention of their presence on this hermit crab.     

Ultrastructure of nematocyst discharge in catch tentacles of the sea anemone Haliplanella luciae (Cnidaria: Anthozoa)

The mature nematocyst lies just beneath the cnidodyte plasma membrane. A microtubule array surrounds the nematocyst capsule just beneath the capsule tip. We propose that the array helps to hold the capsule at the cnidocyte cell surface until discharge. The undischarged capsule tip is sealed by three apical flaps, joined together along complex radial seams. The seams are filled with subunits that appear to bind the flaps together. Upon discharge, the flaps separate along the radial seams to permit thread eversion. The everted thread is lined on both sides by subunits that are stained by antimonate, indicating that they bind calcium. We suggest that, together, the subunits hold the uneverted thread in its folded and coiled configuration. Thread eversion would follow subunit uncoupling. The capsule and thread interiors of partially discharged nematocysts are stained by antimonate. In contrast, the capsule and thread interiors of fully discharged nematocysts are not stained by antimonate. Thus, nematocyst calcium might be injected into the target tissue where it is presumed to act in conjunction with nematocyst venom to promote cell death.     

Die Cnidogenese der Octocorallia (Anthozoa,Cnidaria): I. Sekretionund Differenzierung von Kapsel und Schlauch

The ultrastructural differentiation of capsule and its relation to tube development is described in several Octocorallia species(Alcyonaria: Alcyonium digitatum, Parerythropodium coralloides, Cornularia cornucopiae, Paralcyonium elegans; Pennatularia: Pteroeides spinosum, Veretillum cynomorium; Gorgonaria: Pseudopterogorgia aerosa), all of which have only one type nematocyst. In the Octocorallia, capsule and tube are secreted successively by the Golgi apparatus associated with a primary centriolar complex. During the secretion of the external tube, the outer capsular wall (sclera) is structurally differentiated; inside the capsule the material of the inner capsular wall is separated from the later capsular content (matrix). The primary wall differentiation enables the capsules to grow after capsular secretion has been completed. Following tube secretion, the external tube is completely transferred into the capsule, without the tube wall being transformed into capsular wall, as previously suggested (Westfall, 1966; Ivester, 1977). During early invagination of the tube wall, the coarse, granulated matrix of the external tube is transferred into the internal tube. From this material the spines are developed, which are observed before the tube is completely transferred into the capsule. By a secondary wall differentiation the previously structureless inner capsular wall changes to a complex structure, extending again the capsule, thus mixing the capsular content and enabling the tube to shift to a position, which corresponds with that of mature capsules. These observations demonstrate for the first time the differentiation of the capsule and its close relationship to the differentiation of the tube in nematocysts of Octocorallia.     

New family of sea anemones (Actiniaria,Acontiaria) from deep polar seas

We describe and illustrate two new species from polar deep seas that belong to a new genus and family. Antipodactidae fam. nov. is characterized by acontia with macrobasic p-amastigophores; this type of nematocyst has never been reported from acontia. Antipodactis gen. nov. is characterized by a column with a distinct scapus and scapulus, cuticle-bearing tenaculi on the scapus, more mesenteries proximally than distally, mesenteries regularly arranged, restricted and reniform retractor musculature, and macrobasic p-amastigophores in the acontia. Antipodactis scotiae sp. nov. and A. awii sp. nov. differ in number of mesenteries, retractor and parietobasilar muscles, cnidae, and geographic distribution. We discuss the familial and generic characters of Antipodactis gen. nov. and its relationship to other families of acontiarian sea anemones: it most closely resembles members of Kadosactidae in terms of anatomy and some aspects of cnidom, and has a cnidom identical to that of Diadumenidae in terms of the types of nematocysts. Because the morphology of nematocysts is critical to the diagnosis of this family, we review and comment on the nomenclature of mastigophores. The macrobasic p-amastigophores of Antipodactidae fam. nov. conform to England’s (Hydrobiologia 216/217:691–697, 1991) definition rather than that of Mariscal (Coelenterate Biology. Academic Press, New York, pp 129–178, 1974).     

The occurrence of intercellular bridges in groups of cells exhibiting synchronous differentiation

A previous electron microscopic study of the cat testis revealed that spermatids derived from the same spermatogonium are joined together by intercellular bridges. The present paper records the observation of similar connections between spermatocytes and between spermatids in Hydra, fruit-fly, opossum, pigeon, rat, hamster, guinea pig, rabbit, monkey, and man. In view of these findings, it is considered likely that a syncytial relationship within groups of developing male germ cells is of general occurrence and is probably responsible for their synchronous differentiation. When clusters of spermatids, freshly isolated from the germinal epithelium are observed by phase contrast microscopy, the constrictions between the cellular units of the syncytium disappear and the whole group coalesces into a spherical multinucleate mass. The significance of this observation in relation to the occurrence of abnormal spermatozoa in semen and the prevalence of multinucleate giant cells in pathological testes is discussed. In the ectoderm of Hydra, the clusters of cnidoblasts that arise from proliferation of interstitial cells are also connected by intercellular bridges. The development of nematocysts within these groups of conjoined cells is precisely synchronized. Both in the testis of vertebrates and the ectoderm of Hydra, a syncytium results from incomplete cytokinesis in the proliferation of relatively undifferentiated cells. The intercellular bridges between daughter cells are formed when the cleavage furrow encounters the spindle remnant and is arrested by it. The subsequent dissolution of the spindle filaments establishes free communication between the cells. The discovery of intercellular bridges in the two unrelated tissues discussed here suggests that a similar syncytial relationship may be found elsewhere in nature where groups of cells of common origin differentiate synchronously.     

The ontogeny of interstitial cells in Pennaria tiarella

The interstitial cells of Pennaria tiarella differentiate exclusively from the central endoderm of the planula. Shortly after their appearance, most of the interstitial cells become cnidoblasts. Subsequently, as the larva transforms into a polyp, both cnidoblasts and interstitial cells migrate from the endoderm, through endoblast and mesoglea, into the ectoderm. It is suggested that some interstitial cells remain in the endoderm and differentiate into the gland and mucous cells of the polyp gastroderm.     

Hydrozoan and protozoan epibionts on two decapod species, Liocarcinus depurator (Linnaeus, 1758) and Pilumnus hirtellus (Linnaeus, 1761), from Scotland

Crabs of the species Liocarcinus depurator and Pilumnus hirtellus, collected on the west coast of Scotland, showed hydrozoan and protozoan epibionts. The epibionts of Liocarcinus depurator were the protozoan Ephelota plana and the hydrozoans Clytia gracilis and Leuckartiara sp. The epibionts of Pilumnus hirtellus were the protozoans E. plana and Zoothamnium sp. For Liocarcinus depurator the number of Ephelota per crab fluctuated between 0 and 47 and the greatest number of suctorians were located on the chelipeds, carapace and anterior pereiopods. The hydrozoans, for Liocarcinus depurator, showed densities of 0-20 (Clytia gracilis on the second pereiopod) and 0-507 individuals per crab (Leuckartiara sp., principally on chelipeds, carapace and the fourth right pereiopod). For Pilumnus hirtellus, Ephelota plana showed densities between 3 and 56 individuals per crab, the greatest number of suctorians being located on the same areas as on Liocarcinus depurator. There was a density of 10-69 individuals per crab of Zoothamnium sp. on Pilumnus hirtellus (located on the carapace). Ephelota plana has not been observed previously as an epibiont on crustacea, nor had Zoothamnium sp. as an epibiont on Pilumnus hirtellus. Both hydrozoans, Leukartiara and Clytia, have not been previously described as epibionts on Liocarcinus depurator. Data about the morphological characteristics and distribution of these epibionts are included.     

Histology and ultrastructure of the coenenchyme of the octocoral Swiftia exserta,a model organism for innate immunity/graft rejection

The octocoral Swiftia exserta has been utilized extensively in our laboratory to study innate immune reactions in Cnidaria such as wound healing, auto- and allo-graft reactions, and for some classical “foreign body” phagocytosis experiments. All of these reactions occur in the coenenchyme of the animal, the colonial tissue surrounding the axial skeleton in which the polyps are embedded, and do not rely on nematocysts or directly involve the polyps. In order to better understand some of the cellular reactions occurring in the coenenchyme, the present study employed several cytochemical methods (periodic acid–Schiff reaction, Mallory's aniline blue collagen stain, and Gomori's trichrome stain) and correlated the observed structures with electron microscopy (both scanning and transmission). Eight types of cells were apparent in the coenenchyme of S. exserta, exclusive of gastrodermal tissue: (i) epithelial ectoderm cells, (ii) oblong granular cells, (iii) granular amoebocytes, (iv) morula-like cells, (v) mesogleal cells, (vi) sclerocytes, (vii) axial epithelial cells, and (viii) cnidocytes with mostly atrichous isorhiza nematocysts. Several novel organizational features are now apparent from transmission electron micrographs: the ectoderm consists of a single layer of flat epithelial cells, the cell types of the mesoglea extend from beneath the thin ectoderm throughout the mesogleal cell cords, the organization of the solenia gastroderm consists of a single layer of cells, and two nematocyst types have been found. A new interpretation of the cellular architecture of S. exserta, and more broadly, octocoral biology is now possible.     

The Occurrence of Intercellular Bridges in Groups of Cells Exhibiting Synchronous Differentiation

A previous electron microscopic study of the cat testis revealed that spermatids derived from the same spermatogonium are joined together by intercellular bridges. The present paper records the observation of similar connections between spermatocytes and between spermatids in Hydra, fruit-fly, opossum, pigeon, rat, hamster, guinea pig, rabbit, monkey, and man. In view of these findings, it is considered likely that a syncytial relationship within groups of developing male germ cells is of general occurrence and is probably responsible for their synchronous differentiation. When clusters of spermatids, freshly isolated from the germinal epithelium are observed by phase contrast microscopy, the constrictions between the cellular units of the syncytium disappear and the whole group coalesces into a spherical multinucleate mass. The significance of this observation in relation to the occurrence of abnormal spermatozoa in semen and the prevalence of multinucleate giant cells in pathological testes is discussed. In the ectoderm of Hydra, the clusters of cnidoblasts that arise from proliferation of interstitial cells are also connected by intercellular bridges. The development of nematocysts within these groups of conjoined cells is precisely synchronized. Both in the testis of vertebrates and the ectoderm of Hydra, a syncytium results from incomplete cytokinesis in the proliferation of relatively undifferentiated cells. The intercellular bridges between daughter cells are formed when the cleavage furrow encounters the spindle remnant and is arrested by it. The subsequent dissolution of the spindle filaments establishes free communication between the cells. The discovery of intercellular bridges in the two unrelated tissues discussed here suggests that a similar syncytial relationship may be found elsewhere in nature where groups of cells of common origin differentiate synchronously.     

A novel reef coral symbiosis

Reef building corals form close associations with unicellular microalgae, fungi, bacteria and archaea, some of which are symbiotic and which together form the coral holobiont. Associations with multicellular eukaryotes such as polychaete worms, bivalves and sponges are not generally considered to be symbiotic as the host responds to their presence by forming physical barriers with an active growth edge in the exoskeleton isolating the invader and, at a subcellular level, activating innate immune responses such as melanin deposition. This study describes a novel symbiosis between a newly described hydrozoan (Zanclea margaritae sp. nov.) and the reef building coral Acropora muricata (=A. formosa), with the hydrozoan hydrorhiza ramifying throughout the coral tissues with no evidence of isolation or activation of the immune systems of the host. The hydrorhiza lacks a perisarc, which is typical of symbiotic species of this and related genera, including species that associate with other cnidarians such as octocorals. The symbiosis was observed at all sites investigated from two distant locations on the Great Barrier Reef, Australia, and appears to be host species specific, being found only in A. muricata and in none of 30 other species investigated at these sites. Not all colonies of A. muricata host the hydrozoans and both the prevalence within the coral population (mean = 66%) and density of emergent hydrozoan hydranths on the surface of the coral (mean = 4.3 cm⁻², but up to 52 cm⁻²) vary between sites. The form of the symbiosis in terms of the mutualism–parasitism continuum is not known, although the hydrozoan possesses large stenotele nematocysts, which may be important for defence from predators and protozoan pathogens. This finding expands the known A. muricata holobiont and the association must be taken into account in future when determining the corals’ abilities to defend against predators and withstand stress.     

Factors affecting distribution and abundance of jellyfish medusae in a temperate estuary: a multi-decadal study

Three hydrozoan species, reputedly from the Black Sea (Maeotias marginata, Blackfordia virginica, Moerisia lyonsi), are now found throughout the San Francisco Estuary, California, but long-term and seasonal patterns of distribution and abundance have been poorly documented. We evaluated trends from 35 years of monthly otter trawl data and from a 2-year macrozooplankton survey in Suisun Marsh, a brackish region with extensive tidal sloughs and channels that is part of the San Francisco Estuary. Medusae of all three hydrozoans occurred primarily during the dry season (summer–fall). Abundance of M. marginata medusae significantly increased since the 1980s. Moerisia lyonsi was the most abundant hydrozoan in the macrozooplankton medusa survey followed by M. marginata and B. virginica. Salinity and temperature were strongly positively associated with medusa abundance. Maeotias marginata occurred in the lowest salinity range (2.3–9.1 ppt), while M. lyonsi (2.8–9.9 ppt) and B. virginica (5.6–10.3 ppt) occupied slightly higher salinities. Overall, abundance and distribution of medusae of these three hydrozoans in Suisun Marsh depended on seasonal stability of environmental conditions that favored blooms. While harmful effects have yet to be demonstrated, they could become more of a problem as both sea level and water temperatures rise, especially given the combined range of environmental conditions at which the three species occur.     

Fossile Hydrozoen — Kenntnisstand und Probleme

A critical review on fossil Hydrozoa reveals the following questions and problems:

1. Microstructure, skeleton formation and morphology: According toKazmierczak’s morphogenetical model the formation of the ectodermal basal skeleton depends on a progressive folding of the coenosarc. Can this model be used for all polypoid hydrozoans? Another very important question deals with the possibility of distinctions between systematically important “primary” microstructures and taxonomically worthless “secondary” microstructures which are produced by diagenetical alteration effects.
2. Determination and classification: There is no general agreement on the morphological elements which can be used for the definition of Paleozoic and Mesozoic stromatoporoid genera and species, special problems refer to the taxonomical value of the astrorhizae and of quantitative criteria. About 2000 “species“ from the Paleozoic and about 500 “species“ from the Mesozoic have been described within the Stromatoporoidea but there exists no generally recognized classification system for this group.
3. Paleobiogeography: The oldest polypoid hydrozoans are known from Llanvirnian to Llandeiloverian reef- and shelf-carbonate-deposits; some species described from the Middle Cambrian of Western Sibiria may belong to Archaeocyatha. Tab. 3 shows the temporal distribution of hydrozoan groups. Stricking gaps of knowledge exist for Carboniferous and Permian, Lower Triassic, Liassic, Middle Jurassic and for Tertiary hydrozoan faunas.
4. Palecology: Main factors governing the distribution of polypoid hydrozoans seem to be consistence of substrate, different types of water movement, and eventually differences in salinity. These ecofactors may be recognized by the interpretation of growth forms and growth patterns together with investigations of hydrozoan associations and communities. According to the problems mentioned above no sound evolutionary scheme of all hydrozoan groups is possible just now. Questions dealing with the systematical position of Paleozoic and Mesozoic Chaetetida and with the relationships between Hydrozoa and Sclerospongia have to be studied first (see page 406).

     

Effects of satiation and starvation on nematocyst discharge, prey killing, and ingestion in two species of sea anemone

Studies spanning 60 years with several cnidarian species show that satiation inhibits prey capture and ingestion and that starvation increases prey capture and ingestion. Most have attributed the effects of satiation to inhibition of nematocyst discharge. We hypothesized that satiation inhibits prey capture and ingestion in sea anemones (Haliplanella luciae and Aiptasia pallida) primarily by inhibiting the intrinsic adherence (i.e., holding power) of discharging nematocysts. Using a quantitative feeding assay for H. luciae, we found that satiation completely uncoupled prey killing from prey ingestion, while nematocyst-mediated prey killing was only partially inhibited. Using A. pallida to measure nematocyst discharge and nematocyst-mediated adhesive force, we showed that satiation completely inhibited the intrinsic adherence of discharging nematocysts from Type B and Type C cnidocyte/supporting cell complexes (CSCCs), while only partially inhibiting nematocyst discharge from Type Bs. These inhibitory effects of satiation were gradually restored by starvation, reaching a maximum at 72 h after feeding. Thus, the effects of satiation and starvation on prey killing and ingestion in two species of acontiate sea anemones are primarily due to changes in the intrinsic adherence of nematocysts from both Type B and Type C CSCCs.