The coral species L. pachysepta can live in most reef environments apart from high energy ones and within a depth range of 3 to 30 meters.  It is however most common on the upper reef slopes and lagoons of coral reefs (Iucnredlist.org, 2017). 

Flood, (1977) identifies coral reefs as having a number of zones, rather than being one homogenous reef.  These reef zones are exposed to varying levels of energy from wave action and currents.  This factor along with varying water depths create microhabitats along a reef cross section, and hence support corals of varying morphology.  The reef crest (see Fig 3) is exposed to the greatest energy of any reef zone as it has the highest elevation (apart from a cay), which then dissipates in both the leeward and windward direction (Castro and Huber, 2008). 

The upper reef slope (or fore reef zone in Fig 3) is nested just below the reef crest in a moderate energy environment, just above the deep fore reef.  The upper reef slopes generally has high coral abundance and diversity since it is protected from high wave energy by the reef crest, while still being shallow enough to access sufficient sunlight for the corals photosynthesising algae symbionts. This zone also has enough wave energy for a continual supply of nutrients (Castro and Huber, 2008).  The lagoon is a similar environment that sits on the other side of the reef crest in a lower energy environment ideal for delicate branching corals(Castro and Huber, 2008).    

Stony corals have many strategies of reproduction and include both asexual and sexual reproduction, and have a generation length of 10 years (Iucnredlist.org, 2017).  Many species have separate sexes where the whole colony is either male or female, and some like the genus Lobophyllia are sequential hermaphrodites(Fadlallah, 1983).  Individual polyps produce both male and female gametes for external fertilization rather than brooding planulae for internal fertilization.  This method is known as broadcast spawning. 

Asexual

L. pachysepta is a colonial organism and is made up of repeated, genetically identical individuals known as polyps.  The species propagates asexually through division (Veron and Pichon, 1980), however little is known about this species asexual reproductive modes. 

Sexual

Sexual reproduction involves gametogenesis- the process in which cells undergo meiosis to form gametes.  The primary oocytes (female germ cell) of scleractinian corals first emerge in the mesoglea of the septa (Fadlallah, 1983).  These continue to develop within the mesogleal linings (lamellae) of the septa mesenteries that grow within the gastrovascular cavity known as the coelenteron (Fadlallah, 1983).  During vitellogenesis when nutrients is deposited in the oocyte, and the oocytes increase in number, the entire mesogleal layer between the septa filaments and the polyp wall can become packed with gonads (Fadlallah, 1983).  Spermatogenesis however begins in the septal endoderm, where it is later included within mesogleal gonadal cysts (Fadlallah, 1983).  The mesogleal lining remains around the cluster until spawining occurs (Fadlallah, 1983).  Mature gametes are released into the coelenteron before being spawned through the mouth for external fertilization (Ruppert, Fox and Barnes, 2009).  The eggs and sperm are released in buoyant bundles which drift towards the water surface, breaking up on the way so that fertilization can be achieved with other colonies (Hayward et al., 2011). 

Broadcast spawning is an annual evening event which involved the synchronised release of eggs and sperm into the water column.  Exogenous stimuli such as the lunar cycle and warming water temperatures can stimulate the event (Fadlallah, 1983), while day length, tide height and salinity can influence the timing of the even (GRUMPA).  The exact way in which these stimuli trigger the annual event however is still not properly understood (Twan et al., 2006).  Lobophyllia species have been identified as mid-tropical breeders, requiring 30^oC waters for their annual spring broadcasting (Fadlallah, 1983).  Spawning lasts between a few days and a week as various species spawn at different intervals to avoid hybrids (GRUMPA).  On the Great Barrier Reef, inshore reefs tend to spawn the night after the first full moon in October, while corals on the outer reef tend to spawn in November or December (GBRMPA).  After the release of eggs and sperm into the water column, the boyant , the gametes drift to the surface where fertilization takes place. 

The class Anthozoa is unique from all other cnidarians since they do not include a medusa stage in their life cycle. Corals have a biphasic life cycle consisting of a juvenile planktonic phase, and a dominant benthic adult phase which is separated by metamorphosis.  Following fertilization, egg cleavage commences at the animal pole which is the early beginning of the oral body end.  Following blastulation, gastrulation takes place to form the two inner and outer germ layers (endoderm and ectoderm), and the blastoceal becomes the inner layer of mesoglea (Ruppert, Fox and Barnes, 2009).

 After further cell differentiation, free swimming ciliated planula larvae are produced.  Over several days, the planula elongates and swims aboral end first with use of its flagella amongst the plankton and ocean currents for a period ranging between a few days to a few months (Hayward et al., 2011).  During this time, the planula performs corkscrew swimming onto the ocean floor in search of an appropriate substrate using sophisticated chemosensory (Hayward et al., 2011).  Early metamorphosis occurs just prior to settlement with the morphogenesis of tentacles, septa and pharynx (Ruppert, Fox and Barnes, 2009). 

Metamorphosis is a critical stage in the corals life altering the morphology of free swimming larvae into a sessile polyp.  Once a suitable substrate is detected, metamorphosis continues as the larva settles aboral end down.  New tissue is grown and the newly formed polyp body begins calcification and at this stage also obtains symbiotic zooxanthellae (Hayward et al., 2011). The single polyp asexually propagates into a colony before the cycle begins again.   

Corals such as L. pachyseptahave a range of feeding modes which differ within its lifecycle.  Coral larvae are lecithotrophic meaning that they feed from a nutrient rich yolk sac, and do not have to actively search for food.  The adult polyp form however is a predator with three main feeding mechanisms including nutrients from its symbiotic zooxanthellae, use of cnidae packed tentacles and mucus nets.

Mussid species are all zooxanthellates such that they house unicellular dinoflagellate zooxanthalle in their gastrodermal cells.  Zooxanthalle algae photosynthesise during theday supplying the coral with photosynthates and up to 50 percent of theirenergy requirements (Ruppert, Fox and Barnes, 2009).  During the night, Lobophyllia species predate by extending their tentacles packed with cnidocytes to immobilise and feed on a variety of marine organisms ranging from zooplankton to small fish (Ruppert, Fox and Barnes, 2009). 

Mussids also utilise a third mode of feeding which involves mucus nets (Sorokin, 1993).  These corals secrete large quantities of mucus from the mouth in strip forms. Cilia located from the oral disc out to the side of septa beat to form mucus ‘nets’ at their ends.  When the nets are successful in catching prey, the polyp is triggered and opens it mouth, swallowing the mucus stipes along with its catch (Sorokin,1993). 

Lobophyllia species have also been observed to use their mucus nets for sedimentary filter feeding also (Sorokin,1993). Negatively charged micells of colloids, bacteria cells and detritus particles within the sediments are attracted to the corals muscus which is positively charged by the presence of amino acid groups (Sorokin,1993).  This method of feeding is used continuously, and not dependant on day or night likes the previous two feeding methods discussed.

The coral polyp sits within a corallite (see Fig 4) possessing a tubular body shape.  The oral end consists of an elongated mouth slit which sits within the oral disk, fringed by a whorl often tacles at its outskirts.  The mouth is connected to the central gastrovascular cavity known as the coelenteron by the pharynx.  Ciliated grooves run verticallydown the pharynx at each end of the mouth called siphonoglyphs.  These create currents of water in the pharynx aiding with respiration and maintenance of internal pressure (Willey et al., 1971). The coelenteron is radially partitioned by septa- vertical blades that extend out from the corallite cup.  The septa are a result of gastrodermis out folding such that the individual septa are made of three layers- mesoglear lined either side by gastrodermis (Ruppert, Fox and Barnes, 2009).  The septa extend up to insert themselves onthe oral disk; a distinctive characteristic in L. pachysepta (see physical description for more detail).  Tentacles are an extension of the body wall that grow out between a pair of septal insertions on the oral disc (Ruppert, Fox and Barnes, 2009).  They consist of the three body wall layers of epidermis, mesoglear and gastrodermis that line a hollow centre. 

Following the capture of prey (see Feeding section under Life History and Behaviour), it is moved down into the gastrovasular cavity known as the coelenteron where extracellular digestion takes place.  This is a blind gut with one opening to the exterior via the mouth.  It is partitioned up by septa, increasing the surface area of the gastrodermis to assist in digestion.  In all cnidarians including L. pachysepta, the coelenteron is the main internal transport system in which fluid is transported by the ciliated gastrodermis, muscular contraction, or both (Ruppert, Fox and Barnes, 2009).

Digestion can be initiated with the release of cnidae and injection of proteolytic enzymes during the initial prey capture; however most digestion occurs in the coelenteron (Ruppert, Fox and Barnes, 2009).  Once there, extracellular digestion takes place as gastrodermal gland cells release enzymes, (primarily proteases) reducing prey to a soup like pulp over a period of a few hours.  This enables the breakdown of lipids, carbohydrates and allows for the digestion of proteins.   The nutrients is then absorbed by the gastrodermal cells as the pulp is circulated, and larger chunks are engulfed for intracellular digestion (Ruppert, Fox and Barnes,2009).  This absorption phase of the extracellular digestion takes 8 to 12 hours, followed by intracellular digestion over a few days.  Any indigestible material is ejected via the mouth in a coating of mucus (Ruppert, Fox and Barnes,2009).   

Cnidarians have a wide range of movement due to their muscular system.  The polyp body form in corals can impressively extend, contract and bend their bodies due to having both longitudinal and circular muscle fibres.  The longitudinal muscles are typically associated with the epidermis, while the circular muscles are associated with gastrodermis and are made of epitheliomuscular cells.  These cells are of or relating to the epithelial cell in coelenterates that contains contractile fibres thus allowing it behave like a true muscle cell.  Anthozoans and scyphozoans are unique from all other cnidarians in that that some of their epitheliomuscular cells from the epithelia have migrated to the mesoglea, and evolved into true muscle cells known as myocytes.  Corals also have radial muscle fibres extending from the polyps inner axis out towards the exterior (Ruppert, Fox and Barnes, 2009).     

Corals have a decentralised nervous system consisting of sensory neurons that feel the environment, motorneurons that activate muscles and other cells, and interneurons that join the two together.  Cnidarians have a two layered net systems with one layer in the base of the epidermis, and the other at the base of the gastrodermis.  These two layers are joined by interneurons that run through the mesoglea (Ruppert, Fox and Barnes, 2009).  Unlike other medusae cnidarians, corals do not have advanced nerve rings or ganglia.     

Cnidarians do not have a circulatory system since they only have two true tissue layers (epidermis and gastrodermis) that are in contact with the surrounding water.  These surfaces are ciliated, thus creating a current and making the exchange more efficient.  Therefore all gas exchange simply occurs over the body wall of the individual.  Excretion happens much the same way, such that ammonia (the excretory product of cnidarians), passes through the body wall by diffusion, and is dumped into the surrounding water where it is quickly dissolved and removed by water motion (Ruppert, Fox and Barnes, 2009).   

A key defining feature of all cnidarians is that they have stinging cells known as cnidocytes.  A cnidocyte cell is an explosive combined sensory-effector cell which houses a cnida organelle.  The cnida is a fluid filled sack containing a coiled hollow tubule which is discharged from the cell when signalled.  Cnidocytes are common throughout the epidermis of cnidarians, and in higher density in tentacles and sometimes in localised regions of gastrodermis to assist with immobilising prey for digestion (Ruppert, Fox and Barnes, 2009). 

There are three categories of cnidae including nematocysts, spirocysts and ptychocysts which are housed in three different types of cnidocytes including nematocytes, spirocytes and ptychocytes.  Nematocysts occur in all cnidarians, but within anthozoans, the discharge site of the cnidocyte cells is covered by thre eapical flaps (Ruppert, Fox and Barnes, 2009).  Spirocysts lack any barbs, and instead have sticky threads (see figure 5). 

A cnidome refers the specific assortment of cnidae specific to a species.   The cnidome of L. pachysepta has not yet been described to date, however the cnidome of a close relative Lobophyllia  hemprichii  was described by Cordie (2015) as having a low density and diversity(Cordie, 2015). Cordie (2015) also noted that in central sections of the polyps, spirocytes are few and far between, and nematocytes are uncommon.  The edge sections of the L. hemprichii were similar, although as light decrease in cnidocytes was found (Cordie, 2015).   

From a single L. pachysepta specimen, I clipped off a single tentacle and had it H&E stained and cross-sectioned through various points along the tentacle (see Fig 7).  Slide 1 appears to be the tentacle tip containing only one homogenous layer of epidermis with cnidocytes.  Some epidermis nuclei can also be observed asa vague ring of dark purple dots.  Very few mucocytes (mucus glands) around the outskirts appear as transparent light purple vacancies as the mucus does not colour with H&E.  There is no obvious mesoglea or gastrodermis layer in this slide. 

The second slide is taken from the central region of the tentacle (see Fig 7),and all three layers are present- a thick epidermis (packed with cnidocytes and very few mucocytes), a very thin mesoglea and a central gastrodermis housing zooxanthellae.  The gastrodermal cavity also starts to make an appearance in this section and is called the lumen.  A vague ring of dark purple dots can also be seen here showing epidermis nuclei. 

The third slide (see Fig 7) is located closest to polyp body (point furthest from the tentacle tip).  The wide epidermis is packed full of cnidocytes and mucocytes.  A clear, more compact ring of epidermis nuclei can be seen in this slide.  The mesoglea appears very thin, zooxanthellae are slightly sparser, and the lumen almost consumes the gastrodermis.  No slides show evidence of myocyte cells in or around the mesoglea(see section on Muscles and Nervous System above). 

Figure 6 is a high magnification (40x) of a central section of tentacle with an uneven boarder.  It shows clear tissue layers including gastrodermis housing zooxanthellae, a thick epidermis with mucocytes and cnidocytes and a thin mesoglea layer. At this maginification, the majority of cnidocytes appear to be thin walled spirocysts as the coiled tubules can be made out (see section on Cnidome).   Mucocytes are large and common in the epidermis layer, and the epidermis nuclei are clearly scattered throughout epidermis layer.