Structural–functional Aspects in the Evolution of Operculate Corals (Rugosa)

Among the Rugosa operculae were developed by only a few genera. One is the slipper–shaped Calceola and another is the pyramidal shaped Goniophyllum . On the basis of biological and morphological knowledge of recent corals, the two different bauplans of the soft bodies of Calceola and Goniophyllum have been reconstructed. The soft body (i.e. the polyp) of a rugose coral is thought to have all the basic structures of anthozoan polyps: a barrel–like body shape, a flat oral disc with tentacles, and a mouth from which a pharynx reaches inside the gastric cavity. Furthermore, as in all Anthozoa, Rugosa had internal mesenteries that act as tensile cords; during growth in the diameter further mesenteries were inserted. In contrast to all other Anthozoa, in the Rugosa new single mesenteries were added in four insertion sectors. The bauplans of Calceola and Goniophyllum differ in the pattern of mesentery insertion into these four sectors. Calceola had a serial insertion pattern and Goniophyllum had a symmetrical insertion pattern. They are representatives of the two different bauplans within the Rugosa. The lid corals are examples of convergent evolved genera; Calceola as well as Goniophyllum originated by quite simple modifications of the ancestral type. The peculiar shapes, the operculae and especially the straight hinges between the calyx and the lid(s) result only from mechanical necessity. Under special conditions (such as high sedimentation rates) these modifications of the corallites represent suitable tactics for survival.     

Die Weichkörperkonstruktion vonCalceola sandalina (Rugosa, Anthozoa) — Konstruktionszusammenhänge, Ontogenese, Evolution und Funktionsweisen

The slipper-like corallum ofCalceola sandalina comprises the calyx and the lid. It was generated by an anthozoan-like coral. Anthozoan polyps have a barrel-like shape that is produced and maintained by the activity of internal tethering elements and muscular structures in the body wall. All these structures counteract the hydrodynamics of the gastrovascular cavity. In this reconstruction of the soft parts ofCalceola the functional aspects pointed out byRichter (1929) will be reviewed and revised and partially corrected. Calceola was reconstructed on the basis of the model of rugose polyps. Consequently it consisted of single mesenteries which were added in four sectors in a serial manner. The lid was formed on the counter side and is explained as a bulge of the basal parts of the soft body. The lid was connected coherently by the mesenteries to the whole construction. It could be closed by contraction of the mesenteries and opened by regeneration of the hydraulic volume in the gastric cavity. As a mechanical consequence of moving the lid a straight hinge was developed between the calyx and the lid. The soft body ofCalceola developed by quite simple structural modifications of a rugose coral. The most important modification was the bulging of the basal parts of the soft body on the counter side which formed the lid. This bulge enlarged the surface for adhesion to the substrate and might have been an advantage in survival as well. The soft body generated its own substrate giving it the specific slipper shape. This shape preventedCalceola from sinking into soft or muddy substrate by the principle of a snowshoe which also enabledCalceola to conquer new territories. The lid meant protection where enemies and pollution were concerned. The slipper shape and the lid ofCalceola indicated a complex evolutionary pathway, but they evolved by simple modifications of an ancestor with a round diameter. The slipper shape is just a mechanical consequence of the possession of a flappable lid.     

Principles of early ontogeny in the rugose corals: a critical review

It has been suggested that septal furrows in the Palaeozoic rugose corals are secondary in comparison both to growth lines and to the septal blades inside calices. The leading role of furrows as an indicator of septal increase is thus questioned. Septa are always grouped in quadrants but their increase is generally towards the cardinal septum. The arrangement of the contratingent minor septa seems to be independent of the increase in septal furrows. Hence, the growth of the polyp's skeleton may have started from an aseptal cup.     

Morphologie und Ultrastruktur der KoralleCornularia cornucopiae (Anthozoa,Octocorallia)

Cornularia cornucopiae is a colonial coral whose polyps arise singly from stolons. In contrast with other octocralliaC. cornucopiae lacks calcareous spicules. Therefore, tissue preparation for electron microscopic investigations can be performed. The presence of a calyx such as the theca of hydroids, in which the polyps may be completely retracted, is conspicuous. The calyx consists of three layers. The structure of the basal layer suggests massive collagen. The body wall is connected with the calyx by living desmocytes. The histology of the oral disc and the actinopharynx is identical. The ventral side of the polyps bears the siphonoglyph. Below the pharynx the inner edges of the mesenteries are free and form the mesenterial filaments. The two ventral mesenteries differ from the others; the one is long and exhibits a large and heavily flagellated filament, the other is short and lacks a filament. The muscular system is represented by gastrodermal circular fibres in the body wall and by radial and longitudinal fibres in the septa; a large septal retractor muscle is missing.

---

---

Diese Arbeit ist unserem am 22. März 1984 verstorbenen Kollegen Herrn Dr. B. Werner (Biologische Anstalt Helgoland) gewidmet, auf dessen Initiative diese Untersuchung zurückgeht, der uns zahlreiche Besuche in seinem Labor ermöglichte und uns jederzeit mit Rat und Tat zur Seite stand.     

Tiny sea anemone from the Lower Cambrian of China

Background

Abundant fossils from the Ediacaran and Cambrian showing cnidarian grade grossly suggest that cnidarian diversification occurred earlier than that of other eumetazoans. However, fossils of possible soft-bodied polyps are scanty and modern corals are dated back only to the Middle Triassic, although molecular phylogenetic results support the idea that anthozoans represent the first major branch of the Cnidaria. Because of difficulties in taxonomic assignments owing to imperfect preservation of fossil cnidarian candidates, little is known about forms ancestral to those of living groups.

Methods and Findings

We have analyzed the soft-bodied polypoid microfossils Eolympia pediculata gen. et sp. nov. from the lowest Cambrian Kuanchuanpu Formation in southern China by scanning electron microscopy and computer-aided microtomography after isolating fossils from sedimentary rocks by acetic acid maceration. The fossils, about a half mm in body size, are preserved with 18 mesenteries including directives bilaterally arranged, 18 tentacles and a stalk-like pedicle. The pedicle suggests a sexual life cycle, while asexual reproduction by transverse fission also is inferred by circumferential grooves on the body column.

Conclusions

The features found in the present fossils fall within the morphological spectrum of modern Hexacorallia excluding Ceriantharia, and thus Eolympia pediculata could be a stem member for this group. The fossils also demonstrate that basic features characterizing modern hexacorallians such as bilateral symmetry and the reproductive system have deep roots in the Early Cambrian.     

Biology Of The Famennian Heterocoral Oligophylloides Pachythecus

Studies on the taxonomy and morphology of the Famennian heterocoral Oligophylloides have placed great emphasis on the character of the soft tissue, coloniality and distal development of the skeleton with regard to the construction of the wall. Here, the existence of soft tissue covering the entire skeleton of the colony is proposed. Thirty-eight branching specimens have been found in addition to the predominant single fragments of corallites; these should be regarded as colonial with a well-developed branching form. It is here proposed that the external wall grew not only at the distal end, and that its thickening did not result from the overlapping of tabulae, but was built independently of tabulae by the soft tissue covering the whole skeleton of the colony. The following new characteristics of Oligophylloides are described: a change in the position of septa, so-called 'septal shifting', a rearrangement of the septal apparatus; the occurrence of aulos-like structures; a groove ornamentation on the external wall; and the granular microstructure of the axial part of septa. A detailed study of Late Devonian Oligophylloides corals shows that O. tenuicinctus Róz˙kowska and O. pachythecus pentagonus Róz˙kowska are synonymous with O. pachythecus Róz˙kowska.     

A NEW BASIDIOMYCETOUS SEPTAL TYPE: THE MULTIPERFORATE SEPTUM IN KRIEGERIA ERIOPHORI

Septa from metabasidia and clamp connections of the heterobasidiomycetous sedge parasite Kriegeria eriophori were studied with light and electron microscopy. Septa from clamp connections subtending probasidia were reconstructed from serial sections. Septa at clamp connections are perforated by multiple, simple pores, while metabasidial septa possess single, central swellings which probably represent pores occluded by wall material. The occurrence of multiperforate septa in the fungi is reviewed. The septal morphology of K. eriophori is compared to that of simple-septate heterobasidiomycetes, and the systematic and functional implications are discussed.     

A contribution to knowledge of the compartments and the fascial and septal formations of the popliteal fossa in the human fetus and the adult.

A contribution to knowledge of the compartments and the fascial and septal formations of the popliteal fossa in the human fetus and the adult. A study was made in human fetuses from the 3rd month onwards, newborn and the adult of the fascial and septal formations and the compartments of the popliteal fossa. Observations of serial sections of the knee of human fetuses, of macroscopic preparations of the knee of newborns and of ultrasound images of the popliteal fossa in adults showed that: the fascial formation covering the popliteal fossa consists of the popliteal fascia and the superficial fascia. The bud of the popliteal fascia is observable in the 3-month fetus as a layer of thin fibrillar connective tissue which is thicker in the tracts between the muscle buds. At birth the popliteal fascia is clearly a separate anatomical entity of continuous laminar structure which is thicker in the tracts between the muscles and thinner where it covers them. The superficial fascia becomes evident in fetuses at a later stage (6th month) in the form of a thin lamina in the frontal plane which at birth is well defined and observable as a thin continuous line deep below the subcutaneous layer. The septal formation consists of four septa: two in the sagittal plane (lateral and medial) and two in the frontal plane (lateral and medial). The bud of these septa appears in 4-month fetuses after the appearance of the popliteal fascia. They branch off from the thicker connective areas between the muscles buds as connective prolongations which later assume a laminar aspect and eventually become compact and form septa. In at-term fetuses and newborns these septal formations are clearly recognizable as antomical entities, which branch off from the deep surface of the thicker tracts of the popliteal fascia and are inserted into the femur. The relationships and connections with the muscular groups are also clearly visible. The organization and demarcation of the compartments, which is already delineated in the 6-month fetus, seems to be completed at birth, considering the presence of the superficial fascia, the popliteal fascia and the septa. It is possible to distinguish a superficial compartment between the popliteal and the superficial fascia an a deep compartment between the frontal septa, the skeletal plane and the popliteal fascia. This deep compartment is clearly subdivided by the two sagittal septa into three sectors (medial, intermediate and lateral). The medial and lateral sectors contain muscles, while the intermediate compartment contains the vasculonervous bundle and the popliteal adipose body.     

Skeletal ontogeny in basal scleractinian micrabaciid corals

The skeletal ontogeny of the Micrabaciidae, one of two modern basal scleractinian lineages, is herein reconstructed based on serial micro‐computed tomography sections and scanning electron micrographs. Similar to other scleractinians, skeletal growth of micrabaciids starts from the simultaneous formation of six primary septa. New septa of consecutive cycles arise between septa of the preceding cycles from unique wedge‐shaped invaginations of the wall. The invagination of wall and formation of septa are accompanied by development of costae alternating in position with septa. During corallite growth, deepening invagination of the wall results in elevation of septa above the level of a horizontal base. The corallite wall is regularly perforated thus invaginated regions consist of pillars inclined downwardly and outwardly from the lower septal margins. Shortly after formation of septa (S2 and higher cycles) their upper margins bend and fuse with the neighboring members of a previous cycle, resulting in a unique septal pattern, formerly misinterpreted as “septal bifurcation.” Septa as in other Scleractinia are hexamerally arranged in cycles. However, starting from the quaternaries, septa within single cycles do not appear simultaneously but are inserted in pairs and successively flank the members of a preceding cycle, invariably starting from those in the outermost parts of the septal system. In each pair, the septum adjacent to older septa arises first (e.g., the quinaries between S2 and S4 before quinaries between S3 and S4). Unique features of micrabaciid skeletal ontogeny are congruent with their basal position in scleractinian phylogeny, which was previously supported by microstructural and molecular data. J. Morphol., 2013. © 2012 Wiley Periodicals, Inc.     

Diversity and dynamics of bacterial communities in early life stages of the Caribbean coral Porites astreoides

In this study, we examine microbial communities of early developmental stages of the coral Porites astreoides by sequence analysis of cloned 16S rRNA genes, terminal restriction fragment length polymorphism (TRFLP), and fluorescence in situ hybridization (FISH) imaging. Bacteria are associated with the ectoderm layer in newly released planula larvae, in 4-day-old planulae, and on the newly forming mesenteries surrounding developing septa in juvenile polyps after settlement. Roseobacter clade-associated (RCA) bacteria and Marinobacter sp. are consistently detected in specimens of P. astreoides spanning three early developmental stages, two locations in the Caribbean and 3 years of collection. Multi-response permutation procedures analysis on the TRFLP results do not support significant variation in the bacterial communities associated with P. astreoides larvae across collection location, collection year or developmental stage. The results are the first evidence of vertical transmission (from parent to offspring) of bacteria in corals. The results also show that at least two groups of bacterial taxa, the RCA bacteria and Marinobacter, are consistently associated with juvenile P. astreoides against a complex background of microbial associations, indicating that some components of the microbial community are long-term associates of the corals and may impact host health and survival.     

A soft-bodied lophophorate from the Silurian of England

Soft-bodied taxa comprise an important component of the extant lophophorate fauna, but convincing fossils of soft-bodied lophophorates are extremely rare. A small fossil lophophorate, attached to a brachiopod dorsal valve, is described from the Silurian (Wenlock Series) Herefordshire Lagerstätte of England. This unmineralized organism was bilaterally symmetrical and comprised a subconical body attached basally to the host and partially enclosed by a broad ‘hood’; the body bore a small, coiled lophophore. Where the hood attached laterally, there is a series of transverse ridges and furrows. The affinities of this organism probably lie with Brachiopoda; the hood is interpreted as the homologue of a dorsal valve/mantle lobe, and the attachment as the homologue of the ventral valve and/or pedicle. The ridges are arranged in a manner that suggests constructional serial repetition, indicating that they are unlikely to represent mantle canals. Extant brachiopods are not serially structured, but morphological and molecular evidence suggests that their ancestors were. The new organism may belong to the brachiopod stem group, and might also represent a significant element of the Palaeozoic lophophorate fauna.     

Ontogeny of euthecal and metaseptal structures in colonial scleractinian corals

The ontogenetic development of two Recent scleractinian corals, Golaxea fascicularis (Linnaeus) and Acrhelia horrescens (Dana), has been studied in serial thin sections. The origin of the septotheca (a collective term including both eutheca and pseudotheca) is reconsidered. The eutheca is found to be a basic skeletal structure of corals and of primary origin, formed directly from the basal plate, not by the thickening of septa. The eutheca prepares the way for the formation of metasepta. The ontogenetic growth of the metasepta is illustrated. The pseudotheca is formed by fusion of neighbouring septa and is entirely of secondary origin. Its development is occasional. The essential mural structure of oculinid corals with pseudothecal walls is euthecal.     

An electron microscopic study on the type I pneumocyte in the cat: pre-natal morphogenesis

This investigation describes the pre-natal morphogenesis of the type I pneumocyte subsequent to its differentiation from pulmonary epithelium. Cells lining subpleural alveolar septa were photographed from serial sections with the electron microscope, and a three-dimensional representation of each cell was obtained by transferring the contours of the cell membranes from montages to transparent plastic sheets which were then spaced to scale and stacked. The results of this study indicate that: The nascent blood-air barrier of a 50-day reconstructed cell was twice as thick as the average definitive barrier; definitive barrier thickness was observed in some areas in a 63-day reconstructed cell; the amorphous component of elastic tissue which appears peripherally in septal connective tissue during pre-natal morphogenesis may be directly juxtaposed to the basal lamina of the alveolar epithelium; the orientation of the cell junction between a pneumocyte and its neighboring cells, as observed in sections of alveolar septa, changes as the contour of the pneumocyte changes from simple abutment to overlapping patterns.     

Azooxanthellate? Most Hawaiian black corals contain Symbiodinium

The ecological success of shallow-water reef-building corals (Hexacorallia: Scleractinia) is framed by their intimate endosymbiosis with photosynthetic dinoflagellates in the genus Symbiodinium (zooxanthellae). In contrast, the closely related black corals (Hexacorallia: Anthipatharia) are described as azooxanthellate (lacking Symbiodinium), a trait thought to reflect their preference for low-light environments that do not support photosynthesis. We examined 14 antipatharian species collected between 10 and 396 m from Hawai'i and Johnston Atoll for the presence of Symbiodinium using molecular typing and histology. Symbiodinium internal transcribed spacer-2 (ITS-2) region sequences were retrieved from 43 per cent of the antipatharian samples and 71 per cent of the examined species, and across the entire depth range. The ITS-2 sequences were identical or very similar to those commonly found in shallow-water scleractinian corals throughout the Pacific. Histological analyses revealed low densities of Symbiodinium cells inside antipatharian gastrodermal tissues (0-92 cells mm(-3)), suggesting that the Symbiodinium are endosymbiotic. These findings confirm that the capacity to engage in endosymbiosis with Symbiodinium is evolutionarily conserved across the cnidarian subclass Hexacorallia, and that antipatharians associate with Symbiodinium types found in shallow-water scleractinians. This study represents the deepest record for Symbiodinium to date, and suggests that some members of this dinoflagellate genus have extremely diverse habitat preferences and broad environmental ranges.     

Planulation,larval biology,and early growth of the deep‐sea soft corals Gersemia fruticosa and Duva florida (Octocorallia: Alcyonacea)

Abstract. Although the reproductive biology and early life‐history stages of deep‐sea corals are poorly understood, such data are crucial for their conservation and management. Here, we describe the timing of larval release, planula behavior, metamorphosis, settlement, and early juvenile growth of two species of deep‐sea soft corals from the northwest Atlantic. Live colonies of Gersemia fruticosa maintained under flow‐through laboratory conditions released 79 planulae (1.5–2.5 mm long) between April and early June 2007. Peak planulation in G. fruticosa coincided with peaks in the chlorophyll concentration and deposition rates of planktic matter. Metamorphosis and settlement occurred 3–70 d post‐release. The eight primary mesenteries typically appeared within 24 h, and primary polyps grew to a height of ～6–10 mm and a stalk diameter of ～1 mm within 2–3 months. Planulae of Duva florida (1.5–2.5 mm long) were extracted surgically from several colonies and were successfully reared in culture. Primary polyps reached a height of ～3–4 mm within 2–3 months. No budding of primary polyps was observed in either species over 11–13 months of monitoring, suggesting a very slow growth rate.     

Variation in skeletal microstructure of the coral Galaxea fascicularis: effects of an aquarium environment and preparatory techniques

To compare the crystalline microstructure of exsert septa, polyps of the scleractinian coral Galaxea fascicularis were sampled from shallow reef flat colonies, from colonies living at a depth of 9 m, and from colonies kept in a closed-circuit aquarium. Septal crystal structure and orientation was markedly different between corals in the field and in aquaria. In samples collected from deep water, acicular crystals were composed of conglomerates of finer crystals, and skeletal filling was considerably reduced when compared with samples collected from shallow water. Comparisons were also made between septa prepared in sodium hypochlorite (commercial bleach), sodium hydroxide (NaOH), hydrogen peroxide (H(2)O(2)), and distilled water (dH(2)O). Commercial bleach was the most effective solvent for tissue dissolution in investigations of skeletal structure. Samples prepared in NaOH commonly displayed crystalline artefacts, while the use of dH(2)O and H(2)O(2) was labor intensive and often resulted in unclean preparations. Fusiform crystals were seen only on G. fascicularis septa prepared in bleach and on Acropora formosa axial corallites prepared in either bleach or dH(2)O. We suggest that the mechanical agitation and additional washing necessary for samples prepared in dH(2)O, NaOH, or H(2)O(2) resulted in the loss of fusiform crystals from these preparations.     

Experimentelle Untersuchungen zur Anpassung von Fungiiden (Scleractinia,Fungiidae). an unterschiedliche Sedimentations-und Bodenverhältnisse.

Experiments on Adaptations to Sedimentation and Substrate in Fungiid Corals (Scleractinia, Fungiidae) Experimental evaluation of the sediment rejecting behaviour in fungiid corals shows: a). sediments easily slide off from cupolate coralla; b). some flat corals inflate the polyp to get rid off sediments; c). in most species sediments are entangled in mucus and removed by ciliary action. However mucus production is limited by the number of functioning mucous cells. During continuous stress by weighting sediments the tissue overlying the septal ridges gets cut and worn off. Damage instantly occurs in species with sharp septa, but relatively late in those with broad septa. Even minute tissue remains are capable of regenerating trophozoids attached to the old skeleton. Species which endure only low sedimentation rates, are mainly confined to hard bottoms (e.g. reef slope).     

An early Cambrian polyp reveals a potential anemone-like ancestor for medusozoan cnidarians

Cnidarians form a disparate phylum of animals and their diploblastic body plan represents a key step in animal evolution. Cnidarians are split into two main classes; anthozoans (sea anemones, corals) are benthic polyps, while medusozoans (hydroids, jellyfishes) generally have alternating life cycle stages of polyps and medusae. A sessile polyp is present in both groups and is widely regarded as the ancestral form of their last common ancestor. However, the nature and anatomy of the ancestral polyp, particularly of medusozoans, is controversial, owing to the divergent body plans of the extant lineages and the scarcity of medusozoan soft tissues in the fossil record. Here, we redescribe Conicula striata Luo & Hu from the early Cambrian Chengjiang biota, south China, which has previously been interpreted as a polyp, lophophorate or deuterostome. Through re-examination of the holotype and 51 exceptionally preserved specimens, we show that C. striata possessed features of both anthozoans and medusozoan polyps. A conical, annulated organic skeleton (periderm) fully encasing a polyp is found in fossil and living medusozoans, while a tubular pharynx extending from the mouth into a gut partitioned by c. 28 mesenteries, resembling the actinopharynx of anthozoans. Our phylogenetic analyses recover C. striata as a stem-group medusozoan, implying that the wealth of medusozoan diversity derived, ultimately, from an anemone-like ancestor.     

A simple test: evaluating explanations for the relative simplicity of the Edwardsiidae (Cnidaria: Anthozoa)

Many members of the cnidarian subclass Zoantharia (sea anemones, corals, and their allies) pass through a larval stage with eight complete mesenteries and without posterior musculature. This larva is usually transient, developing into an adult with 12 or more mesenteries. The adults of one family of sea anemones, the Edwardsiidae, bear the larval number and arrangement of mesenteries and lack the pedal disc seen in other sea anemones. The morphology of the Edwardsiidae has been interpreted in a number of ways: (1) the Edwardsiidae are the most basal extant zoantharian, having diverged before the evolution of additional mesenteries and basal musculature; (2) they are relatively advanced sea anemones that have secondarily simplified because they burrow in sand or mud rather than attaching to a hard substrate; or (3) edwardsiids are derived anemones that have retained a juvenile morphology through paedomorphosis. Phylogenetic analyses of small subunit ribosomal gene sequences reveal that the Edwardsiidae are derived zoantharians, nested within sea anemones. None of the proposed explanations fully explain the edwardsiid's body plan; edwardsiid anatomy is a mosaic of retained primitive and derived features. The results of the present study provide insight into zoantharian phylogeny and illustrate how phylogenetic tests can be used to study the evolution of cnidarian body plans.