Type Of Scleritis Research Articles

Morphological study of the sclerites of the species Renilla muelleri Kölliker, 1872 (Anthozoa, Octocorallia, Pennatulacea)

Some octocorals (Cnidaria, Anthozoa) can produce a sub-millimeter to a millimeter-range skeleton of calcium carbonate, known as sclerites. Sclerites have diverse morphological characters, such as size, and shape features that give them relevance as taxonomic characters at different levels. Renilla Lamarck, 1816, is a genus of the order Pennatulacea (Octocorallia), in which colonies are characterized by two distinct zones: a peduncle, which anchors them to the substrate, and a rachis that supports the polyps. In the case of Renilla muelleri Kölliker, 1872, prior research established the presence of similar sclerites in both the peduncle and the rachis. Nevertheless, the potential morphological variations of these sclerites among colonies and within different colony regions have yet to be assessed to determine the stability of these characteristics at the species level. This study aimed to describe and compare the external microscopic morphology and biometry of the sclerites of Renilla muelleri, enhancing their identification and assessing their consistency within the species. Sclerite composition was examined across the entire colony, and we analyzed length variation among colonies using generalized linear models (GLM) and within colony zones using generalized linear mixed models (GLMM). Additionally, the external microscopic morphology of all sclerites was examined through scanning electron microscopy (SEM). Based on size, two types of sclerites, namely large and small, were identified within the colonies. Both types exhibited significant size differences among colonies. Furthermore, the large sclerites displayed notable variations between zones, with those in the rachis being the largest and holding the highest rank within the colonies. In terms of external microscopic morphology, the sclerites exhibited considerable variability, making it challenging to establish clear groupings based on these characteristics. Based on the obtained results, it can be concluded that both the biometry and external microscopic morphology of sclerites do not exhibit consistency as characteristics in Renilla muelleri highlighting the ambiguity in defining Renilla species.

Funeralaspis n. gen.: a new odontopleurine trilobite from the early Middle Ordovician (Dapingian) of Death Valley, eastern California, USA, and the classification of Ordovician odontopleurines.

Funeralaspis n. gen. (type species F. deathvalleyensis n. sp.) is the oldest known formally named odontopleurine trilobite species, described on the basis of abundant secondarily silicified sclerites of all sclerite types except the rostral plate, from the Dapingian of the Antelope Valley Formation, west flank of the Funeral Range, Death Valley National Park, Inyo County, California. Many Ordovician odontopleurines have been assigned to Diacanthaspis, to the point that it has become something of a taxon of convenience. All of the potential species are listed along with their provenance, preservation, and represented sclerite types. A core group of Diacanthaspis, termed Diacanthaspis (sensu stricto or s.s.) possibly represents a Laurentian clade, consisting of the type species, D. cooperi, and D. lepidus, D. orandensis, D. scitulus, D. secretus, and possibly D. elapsa and D. parvula. This group is characterized by extreme dorsal spinosity, dorsal accessory spines on the base of the genal spine, pygidial spines with lateral fringes of tiny spines, and thoracic and pygidial ring furrows with fringes of tiny spines. Funeralaspis deathvalleyensis has none of the features characteristic of Diacanthaspis and in general scarcely resembles members of this Upper Ordovician group. Remaining species that have been assigned to Diacanthaspis, some of which are very poorly known, should be reclassified as knowledge of Ordovician odontopleurines advances, but for the present are treated as Diacanthaspis (sensu lato or s.l.). A heretofore nearly unknown species described as Ceratocephala maquoketensis from the early Katian of Howard County, Iowa, has not been commented upon in the literature since it was proposed. It is an odontopleurine which in the current state of knowledge should be assigned to the Diacanthaspis (s.l.) group.

Ocruranus-Eohalobia Sclerites from the Cambrian Stage 2 Yanjiahe Formation in South China: Scleritome Reconstruction and Zoological Affinity.

The isolated sclerites of the Ocruranus and Eohalobia group are abundant among the early Cambrian small shelly fossil assemblages, which were recently assigned to the same scleritome as an early member of the polyplacophoran (chiton) stem lineage. However, the scleritome reconstruction and zoological affinities of these sclerites are still controversial due to the lack of exceptionally preserved articulated specimens with in-situ sclerites. Herein, we report new specimens of Ocruranus and Eohalobia sclerites from Member 5 of the Yanjiahe Formation, which provide new insights into the reconstruction of the original scleritome. The Eohalobia sclerites from the Yanjiahe Formation have an extended and upfolded proximal field with dense wrinkles, which seems to be a weakly mineralized structure and acted as a joint with another sclerite, Ocruranus. Comparing the butterfly-shaped proximal field on a unique sclerite of Eohalobia with the sub-apical field on Ocruranus sclerites suggests that the original scleritome of this group may consist of only two types of sclerites: the Ocruranus-type and the Eohalobia-type. The polygonal structure on the internal mold of Eohalobia sclerites is interpreted herein as the muscle attachment zone; their distribution corresponds well with that of the modern chitons, which provides strong evidence to support the close relationship between the Ocruranus-Eohalobia group and the Polyplacophora.

Clinical Profile, Systemic Association, Treatment and Visual Outcome of Patients with Scleritis in an Eye Care Center in Mexico City

ABSTRACT Aims To describe demographic and clinical characteristics as well as etiologies and visual outcomes of patients with scleritis. Methods This is a descriptive, observational and retrospective study. We reviewed the electronic health records of patients with diagnosis of scleritis, who presented at the Institute of Ophthalmology Conde de Valenciana from January 2009 to December 2019. Results The cohort consisted of 162 patients with mean follow-up of 33.7 months. Mean age of scleritis presentation was 53.8 years. The most common type of scleritis was anterior nodular in 67 patients (41.3%). Most cases were idiopathic (52.4%). Visual outcomes were worse in anterior necrotizing scleritis. The most used drugs were oral NSAIDs and corticosteroids. Conclusion The visual outcome in most patients is favorable, however it depends on scleritis type and etiology, with worse prognosis in anterior necrotizing scleritis forms and associated with autoimmune or systemic diseases.

Clinical Profile of Patients with Scleritis in Bangladesh

ABSTRACT Purpose: To analyze clinical profile of the patients with scleritis in a tertiary care eye hospital in Bangladesh. Method: Retrospective analysis of 111 eyes of 79 patients of scleritis between January 2012 and May 2018. Result: The study observed a relative younger mean age and equal gender distribution. Diffuse anterior scleritis (43%) was the most common type of scleritis. Rheumatoid arthritis (10%) was the most common systemic disease followed by granulomatosis with polyangiitis (5%) and tuberculosis (2.5%). Fifty-eight patients (73.4%) required immunosuppressive agents. Conclusion: The current study highlighted a distinct pattern and profile of scleritis patients in Bangladesh.

Chancelloriid sclerites from the Dyeran–Delamaran (‘Lower–Middle’ Cambrian) boundary interval of the Pioche–Caliente region, Nevada,USA

AbstractChancelloriids are a poorly understood group of phylogenetically problematic Cambrian metazoans; complete specimens show they were sessile, radially symmetrical, club‐shaped organisms covered with sclerites in the form of rosettes of spines. While isolated sclerites are common components of Cambrian shelly assemblages, they have been relatively little studied. We describe chancelloriid sclerites from a series of nine sections spanning the upper Dyeran to lower Delamaran stages (latest Stage 4 to perhaps basal Wuliuan) from the Pioche–Caliente region of east‐central Nevada,USA. Acid maceration of samples from the Combined Metals, Comet Shale and Susan Duster Limestone members of the Pioche Formation yielded more than 2000 sclerites. Based on careful examination of these sclerites and statistical analyses of co‐occurring sclerite types, we distinguish six species, each with a restricted stratigraphic range.Chancelloria imparMoore sp. nov. is the dominant species in most upper Dyeran samples.Archiasterella cometensisMoore sp. nov. andA. auriculataMoore sp. nov. are rare in the upper Dyeran but abundant in the lowest Delamaran;A. uncinataMoore sp. nov. andC. lilioidesMoore sp. nov. replace these in younger samples.A. auriculatais noteworthy for sharing features with species of bothArchiasterellaandChancelloria. These results provide further support for the taxonomic tractability and biostratigraphical utility of chancelloriid sclerites; large collections from single horizons allow intraspecific variability to be assessed and species to be distinguished. Our results document a taxonomic turnover in chancelloriids at the Dyeran–Delamaran boundary, showing that not only trilobites were affected at this time.

Paterimitra pyramidalis Laurie, 1986, the first tommotiid discovered from the early Cambrian of North China

The eccentrothecimorph tommotiid Paterimitra pyramidalis Laurie, 1986, was previously only known from lower Cambrian rocks of the Northern Territory and South Australia. Herein, we document the first occurrence of P. pyramidalis from the Xinji Formation in the Shuiyu section at Ruicheng County, Shanxi Province, located at the southwestern margin of the North China Platform. This represents the first report of a tommotiid taxon from lower Cambrian strata of the North China Platform. All three sclerite types that characterise the scleritome of P. pyramidalis have been recovered and are described, permitting definitive identification to species level. The discovery of P. pyramidalis from the North China Platform not only greatly extends the palaeogeographic range of this distinctive tommotiid taxon, but also supports planktotrophic development of larvae in Paterimitra as a stem group brachiopod. The discovery of P. pyramidalis supports a Cambrian, Epoch 2, late Age 3 to early Age 4 age for the shelly fossil fauna from the Xinji Formation and indicates a close palaeogeographic position between the North China Platform and Australian East Gondwana during the early Cambrian.

New early Cambrian sclerites ofLapworthella schodakensisfrom NE Greenland: advancements in knowledge of lapworthellid taxonomy, sclerite growth and scleritome organization

AbstractThe Cambrian Stage 4 upper Bastion Formation of Albert Heim Bjerge and CH Ostenfeld Nunatak, NE Greenland, yielded 34 excellently preserved sclerites ofLapworthella schodackensisamong other small shelly fossils. Lapworthellids have been interpreted as members of the camenellans, a basal tommotiid group. Little is known about this group although the morphological and ultrastructural features of their sclerites allow a potential reconstruction of a lophophorate body plan. The exquisite material from Greenland provides significant new data for the revision of the species taxonomy, but also for the comprehension of the scleritome structure of lapworthellids and the mode of formation of their sclerites. Two morphotypes ofL. schodackensissclerites are identified: one with a simple apex, occurring in sinistral and dextral forms; and one bilaterally symmetrical sclerite with two apices. All bear a similar ornamentation constructed of repeated growth sets consisting of a reticulate inter-rib groove with tubercles, a densely denticulate rib and a striated sub-rib area. The new data on the ornamentation and observations of the laminar shell microstructure ofL. schodackensisenable us to improve the reconstruction of growth in lapworthellids. Finally, the morphological features of the two types of sclerites provide new information for the reconstruction of the bilaterally symmetrical multi-component lapworthellid scleritome with evidence of the fusion of adjacent sclerites during early ontogeny.

The habitus of Scutopus robustus Salvini-Plawen, 1970 (Caudofoveata, Limifossoridae), a rare mollusc from the NW Iberian Peninsula

Caudofoveata are vermiform, aplacophoran molluscs with reduced foot and a mantle covered with calcareous sclerites. Most Caudofoveata live at great depths mainly burrowing in muddy bottoms. They are usually damaged during their collection, thus the iconography available is incomplete, except for the patterns of the sclerites. A sample of Scutopus robustus was collected during the oceanographic expedition MASPROGAL 2013, carried out by the EBMG-USC, on the bottoms of polymetallic nodules and corals of the NW Iberian Peninsula at a depth of 600–700 m (43°48,000’N, 8°51,760’W). S. robustus is a rare species recorded for the first time in this geographic area, which confirms the suspicions of Salvini-Plawen and Garcia-Alvarez (2014) about its presence off the Iberian Peninsula; so far, it has only been found off Norway, Iceland, northern England, southwest Ireland and the western Mediterranean Sea (Salvini-Plawen 1970; Ivanov and Scheltema 2001, Salvini-Plawen and Garcia-Alvarez 2014). Specimen: 5 mm long × 0.25–0.5 mm wide. White in 70% ethanol. Postoral buccal shield slightly flanking the mouth. Three body regions (Fig. 1a): anterium, trunk and tassel, covered in sclerites lying longitudinally on the mantle. Anterium (Fig. 1b), with flat, smooth, lanceolate sclerites (40–70 μm long × 15–30 μm wide) and truncated base (Fig. 1e, f). Trunk narrowing in its medial region (Fig. 1c), with two types of sclerites: first type lanceolate (80–130 × 25–45 μm) with smooth waist, truncated base with slight notch and reinforced apical end of the blade (Fig. 1g–j) on the first part of the trunk; second type (100–150 × 20–50 μm) like the first but with a round base (Fig. 1k, l) at the end of the trunk. Tassel bell-shaped (Fig. 1d) with two types of sclerites: first type lanceolate (150–200 × 30–40 μm) with slight waist and round base longer than the blade (Fig. 1m); second type acicular (180–220 × 10–15 μm) and smooth (Fig. 1n). The iconography of S. robustus is scarce, and only two low-quality photographs of the habitus and some drawings of the sclerites are known (Salvini-Plawen 1970, 1972, 1975). The detailed photographs of the habitus and sclerites under and optical microscope and SEM presented in this paper are the first for this species. The studied specimen differs from those already described (Salvini-Plawen 1970, 1972, 1975), as the small, triangular sclerites described from the anterior part were not observed, probably due to the strong contraction of the anterior part, and the acicular sclerites of the tassel are longer than those of previous descriptions. The fact that the trunk Communicated by P. Martinez Arbizu

Interleukin-22 serum levels are elevated in active scleritis.

To evaluate serum cytokine profile from patients with active scleritis in a two-centre prospective case-control study. The serum of 20 active scleritis patients not treated with any local, periocular, or systemic immunomodulatory therapy (IMT) was analysed with multiplex assay to determine the levels of 11 cytokines interleukin (IL)-1β, IL-6, IL-2, IFN-γ, IL-10, IL-12p40, IL-13, IL-17A, IL-5, TNF-α, and TNF-β, and with ELISA to determine the levels of TGF-β1, IL-22, and IL-23. Twenty-five age-matched healthy volunteers were used as controls. In a subgroup of 13 patients with active disease, a second serum sample was obtained when the disease was inactive and levels of IL-22 were determined. Serum IL-22 levels from patients with active scleritis were correlated with type of scleritis (non-necrotizing and necrotizing), degree of inflammation (0-4+:≤2+ and >2+), and associated systemic disease. Serum levels of IL-22 were elevated in active scleritis patients compared to controls (6.41±1.52pg/ml versus 1.93±0.39pg/ml, p=0.012) and significantly decreased after scleritis remission with the use of IMT (p=0.005). There was no statistical association with scleritis type, degree of inflammation, or associated systemic disease. The serum levels of other cytokines were not significantly different from controls. In our study cohort, IL-22 serum levels were significantly elevated in active scleritis patients compared to controls and decreased significantly after remission. Our results suggest that IL-22, a T helper (Th) 17- and Th22- derived cytokine, may play a critical role in the physiopathology of scleritis.

Clinical features and visual outcomes of scleritis patients presented to tertiary care eye centers in Saudi Arabia.

To describe the clinical features, systemic associations, treatment and visual outcomes in Saudi patients with scleritis. A retrospective chart review was performed for patients with scleritis presenting to two tertiary care eye hospitals in Riyadh, Saudi Arabia, from 2001 to 2011. Data were collected on the clinical features of scleritis, subtypes of scleritis, associated systemic disease, history of previous ocular surgery and medical therapy, including the use of immunosuppressants. Treatment outcomes were evaluated based on best-corrected visual acuity (BCVA) and response to treatment. Of the 52 patients included in the study, non-necrotizing anterior scleritis was the most common type of scleritis in 22 patients (42.3%), followed by posterior scleritis in 14 patients (26.9%). The majority of cases, 31 patients (59.6%), were idiopathic in nature. Systemic associations were present in 12 patients (23.1%). Infectious scleritis was confirmed in 6 patients (11.5%): 3 with bacterial scleritis after pterygium excision, 2 patients with scleritis related to tuberculosis and 1 patient with scleritis resulting from herpes simplex infection. For the various subtypes of scleritis, BCVA values after treatment and time to remission significantly differed (P<0.05, all cases). Systemic immunosuppressive therapies in addition to steroids were administered to 46.2% of all patients. The T-sign was present on B-scan ultrasonography in 9 (64.3%) of the 14 posterior scleritis patients. Non-necrotizing anterior scleritis was the most common subtype of scleritis. Final visual outcome and time to remission differed among the various scleritis subtypes.

Comparative biometry and isotopy of three dominant pennatulacean corals in the Northwest Atlantic

AbstractSpatial and temporal shifts in biometric features were examined in three common deep‐water pennatulacean corals (sea pens) from the Northwest Atlantic: Anthoptilum grandiflorum, Halipteris finmarchica and Pennatula aculeata. These three species show different morphological characters and adaptations to their environment. Analyses of colony length, ratio of peduncle to colony length, weight/length ratio, polyp size and density as well as sclerite shape, location and abundance indicate that their phenotype is modulated by environmental factors (e.g. food availability, currents and sediment type) and antipredator strategies. Moreover, the three species had different carbon and nitrogen stable isotope signatures that could be explain primarily by their different polyp diameters and colony shapes, suggesting that they rely on slightly different food sources (varying proportions of phytodetritus and zooplankton). Finally, sclerites were found only in H. finmarchica and P. aculeata and are not known to occur in A. grandiflorum, except for minute oval bodies inside the peduncle. The Mg/Ca ratio of sclerites differed between the two species and, for P. aculeata, among types of sclerites, evoking different biomineralization pathways related to their functional roles (structural support or defence). Overall, this study provides new information on the ecology of poorly known species, which are ubiquitous and suspected to play an important ecological role in deep‐water ecosystems.

Evolution and taxonomic significance of the copulatory apparatus in Ensifera (Orthoptera). Part 2: Male genitalia in Grylloidea

In the superfamily Grylloidea, the main trends in the evolution of the copulatory apparatus were probably connected with the transformation of simple membranous (hagloid) genitalia, characteristic of ancient groups of Ensifera, into a complicated organ with highly specialized sclerites for fixation of the female during copulation. This evolutionary process was probably accompanied by partial reduction and disappearance of paraproctal hooks or other external abdominal processes which may have been used by these ancient groups for female fixation. Sclerites in the male genitalia of Grylloidea appeared independently not less than four times: in Gryllotalpidae, Myrmecophilidae, Gryllidae and Mogoplistidae. This hypothesis, proposed by Gorochov in 1984, was one of the reasons for division of the recent Grylloidea into four families. Each of the first three families acquired sclerites in the male genitalia once, whereas Mogoplistidae possibly acquired them more than once: male genitalia of the tribe Mogoplistini are of the hagloid type, membranous; in most genera of Arachnocephalini (Mogoplistinae), in Pseudomogoplistes (Mogoplistinae) and in Malgasiinae, male genitalia have three types of sclerites which could have also appeared independently. Moreover, many sclerites of the male genitalia in Grylloidea are formed independently and have significant convergent similarity; this is why the nomenclature of male genital structures based partly on their function and position but not exclusively on their homology is simpler and much more suitable for descriptions and morphological investigations. This nomenclature is considered here.

Mycophenolate mofetil therapy in scleritis: Analysis of seven cases in tertiary eye hospital in India

To evaluate the effectiveness of immunomodulatory mycophenolate mofetil in the treatment of scleritis. A retrospective non comparative review of seven cases of scleritis managed with mycophenolate mofetil at a tertiary eye hospital. The following information was extracted from the patients folders; socio-demographics, causes, type of scleritis, duration of scleritis, previous treatment on before commencement of mycophenolate mofetil (MMF), any systemic association, visual acuity (VA) at presentation and at the last hospital visit, laterality of the scleritis and the side effects experienced during the use of mycophenolate mofetil.Two patients with anterior nodular and four patients with diffuse anterior scleritis were identified. The mean follow up was 6 months. Six patients had the same pre-treatment VA and one patient had improved VA. No patient reported any side effect. All the inflammations were controlled in all the patients and no case of relapsed during the usage of MMF was reported. And no patient needed any additional immmunosupressive agents.Mycophenolate mofetil appears to be an effective drug in the management of anterior scleritis. The absence of side effects following its use is remarkable. It holds promise to reducing the blinding complication of scleritis. A further study with large sample size may be required to confirm our findings.DOI: http://dx.doi.org/10.3126/jcmc.v5i1.12572

Revision of Plumulites ruskini Lamont, and new data from the Silurian of the Pentland Hills, Scotland

Disarticulated sclerites of plumulitid machaeridians were collected from the Wether Law Linn Formation (Telychian) in the Pentland Hills, Scotland. The specimens are described and compared to specimens collected earlier from the same horizon and locality. Other specimens from the same horizon, assigned in previous works to Turrilepas haswelli then to Plumulites sp., are figured here for the first time. The micro-ornament on plumulitid machaeridians is also documented for the first time. Seven sclerite types are identified and tentatively associated into scleritomes. The collection from the Pentland Hills is compared with other Ordovician and Silurian taxa from various Scottish localities, and this comparative study indicates that the present collection may constitute a new taxon. Nevertheless, complete individuals have to be collected to warrant a confident taxonomic identification.

Morphology of Falcidens vasconiensis (Mollusca, Caudofoveata, Chaetodermatidae), including a 3D reconstruction of the internal anatomy

The morphology and internal anatomy of the caudofoveate Falcidens vasconiensis Salvini-Plawen, 1996, are described and a 3D reconstruction of its anatomy is made with the program AVIZO 6.3.1. The detailed body shape, additional sclerite types, digestive system, and nervous system of F. vasconiensis are described for the first time. The nine specimens studied here were collected off the NW Iberian Peninsula between 150 and 600 m depth during the expeditions DIVA-Artabria I 2002 and 2003, Vertidos 2004, and A Selva 2008.

Five-year outcome in immune-mediated scleritis.

Immune-mediated scleritis is a rare condition, and the information on the clinical course and complications is scarce. The aim of this study was to identify prognostic factors, complications, and therapeutic effects in patients with immune-mediated scleritis. Patients with diagnosis of scleritis and a follow-up time of 5 years were identified. Systemic disease, laboratory investigations, type of scleritis, disease activity, therapy, and complications were recorded. The study design was a retrospective, non-comparative, interventional case series. Systemic disease was identified in 15 (37%) patients at presentation and in 18 (45%) after 5 years. Rheumatoid arthritis (15%), granulomatosis with polyangiitis (7.5%), and polychondritis (7.5%) were the most predominant disorders. Persistent scleritis (>5 years) was associated with systemic disease (66 vs. 6%; p < 0.05) and positive auto-antibodies (48 vs. 23%; p = 0.18). Control of ocular inflammation was achieved in 38 of 40 (95%). Prednisone (14 patients) and/or methotrexate (8) were the predominant drugs to control persistent disease. Complications included interstitial keratitis (2), inflammatory astigmatism (2), corneal melt (3), macular edema (6), and severe systemic disease (5). The presence of systemic disease and positive auto-antibodies are associated with persistent scleritis. Immunosuppressive agents allow control of scleritis, but may contribute to severe systemic complications.

Sclérites et épisclérites : prise en charge diagnostique et thérapeutique

Episcleritis and scleritis are distinct entities with regard to visual prognosis, risk of associated systemic disease, and treatment. The pertinence of the clinical classification of episcleritis and scleritis established in 1976 still persists, with significant differences in terms of visual prognosis, associated general conditions, and therapeutic choices according to each scleritis subtype. Episcleritis requires rarely to be referred to a tertiary care centre, and if so it has to be monitored similarly to scleritis. In this paper, an analysis of 1358 scleritis cases from the main distinct large series published since 1976 shows a mean proportion of 8% of infectious aetiologies (mainly herpes viruses), and 28% of systemic diseases with two main subgroups: inflammatory rheumatisms 12.8%, and systemic vasculitis 7.8%. Overall, the risk for visual loss following scleritis is around 16%. However, the risks of associated systemic disease and visual loss are both highly variable according to the type of scleritis, and culminate at 80% and 50% in the necrotizing subtype respectively. As compared with older series, the proportion of necrotizing scleritis is lower in recent series which is likely due to the advances obtained over the past 20 years in immunomodulatory therapy, as well as its wide use in the treatment of the main systemic conditions associated with scleritis. The treatment of scleritis should be managed by physicians who are experts in the use of immunosuppressive drugs that may be required in one out of two affected patients.

Two new paralcyoniid octocorals from Japan (Anthozoa: Alcyonacea).

Two new species of paralcyoniid octocorals are described from Japan. One of them, Ceeceenus retractus n. sp., is the fifth species of the genus, and the other, Nanalcyon sagamiense n. gen. n. sp., is proposed as a new genus. Nanalcyon is similar to the Mediterranean and Atlantic genera Maasella Poche, 1914 and Paralcyonium Milne Edwards and Haime, 1850, but the new genus clearly differs from these in having independent colonies not joined by stolons. The ultrastructure of the sclerites is compared among the new genus, Ceeceenus and Paralcyonium by means of SEM. All three genera display the same three main types of sclerites, flat platelets, rods and spindles, the ultrastructure of all consisting of non-branching fibrous crystals. In addition to these, two genera, Ceeceenus and Paralcyonium, have flat oval platelets with the ultrastructure showing branching dendritic crystals, lacking in Nanalcyon.

Ordered Misorientations and Preferential Directions of Growth in Mesocrystalline Red Coral Sclerites

The sclerites of the red coral are ideal structures to handle the question of crystallographic registers in biominerals. Microscopy and diffraction techniques are used to reveal the concealed relationships between the elaborate morphology and the crystallographic organization of the sclerites. Sclerites are 50–80 μm large structures, built from concentric layers of sub-micrometer grains of Mg calcite. Two main types of sclerites are identified: single- and multidomain sclerites. “Single-domain” sclerites are elongated centrosymmetric dumbbells with tubercles in opposite trihedral arrangement. The crystalline grains are similarly oriented with the c axis along the dumbbell length. Each tubercle extends along a direction, the denser Ca2+CO32– chain of the most stable {104} plane of calcite. Each tubercle develops lobes again along the directions indicating a dendritic like growth process in three-dimensional (3D) space. Crystallite misorientations of about ±15° are correlated to the biogenic c...