The body plan of Telmatactis sp. bears much resemblance to stereotypical Actiniarians and so, unlike other Cnidarians, does not possess a medusa stage in their life cycle. Its polypous design consists of a tubular column which attaches to hard substrates via a pedal disc while the oral surface possesses a number of tentacular appendages which surround a central mouth (Ruppert et al., 2004). It possesses two siphonoglyphs which are ciliated grooves located at the corners of the mouth and lead into the actinopharynx. Despite being tubular, the pharynx is laterally compressed, resulting in the mouth opening appearing as a slit (Shick, 1991). 

Telmatactis sp. is characterised by its unique clavate or club-tipped tentacles which are arranged in a hexamerous fashion (den Hartog, 1995) around the white speckled oral surface. The tentacles closer to the mouth are significantly longer than those distally, but all exhibit a white frosting pattern at the base which transitions to deep purple at the tips (Figure 1). The column is opaque and slightly orange-brown in colour. 

The pharynx opens out into the coelenteron which is divided into a number of infoldings of the body wall called septa (mesenteries) and functions as a blind gut (Ruppert et al., 2004). These structures insert at the pedal and oral discs, some also have insertions on the actinopharynx (complete septa) while some do not (incomplete septa). Tentacles arise from outgrowths of the body wall between septal attachments on the oral surface (Figure 2). 

Complete septa in Telmatactis possess strong kidney-shaped retractor muscles, gonads and unilobed septal filaments (den Hartog, 1995). These filaments contain a number of cnidoglandular cells (cnidocytes and enzymatic gland cells) which aid in digestion, as well as flagellated sections (Ruppert et al., 2004). Telmatactis, unlike most anemones, also possess acontia (den Hartog, 1995) which are long cnidocyte-dense threads that attach at the septum below the filaments and coil in the coelenteron (Shick, 1991) (Figure 3). 

A feature characteristic of the subclass Hexacorallia is their tendency to possess a form of biradial symmetry in which structures are arranged in groups of six or twelve (Ruppert et al., 2004). This plane of symmetry bisects the mouth, siphonoglyphs and pharynx to create a mirrored radial arrangement of mesenteries (Shick, 1991) (Figure 4). This symmetry is demonstrated by Telmatactis in its pair of siphonoglyphs which lie along the directive axis, and the most central tentacles which are most obviously in radial arrangement.  

Telmatactis has previously been described as an exclusively littoral genus (Doumenc et al., 1989), however a number of studies have also found some species at least as deep as 15 metres (Acuña et al., 2012) or even 35 metres (Fautin et al., 2007). Regardless, Telmatactis is commonly found attached to hard substrates underneath rocks, boulders or coral (Figure 5) (Fautin et al., 2007; Acuña et al., 2012) in moderate light exposure (den Hartog 1995). This has also been observed in Telmatactis sp. which, in a laboratory aquaria setting, moves to the underside of rocks but extends the column so that the tentacles are exposed. 

Many anemones in addition to opportunistic feeding also harbour photosynthetic dinoflagellates usually in the tentacles known as zooxanthellae. This symbiotic relationship can sometimes contribute to the diversity of colour in anemone species (Ruppert et al., 2004). However, there is some confusion as to whether these relationships exist within the Telmatactis genus. den Hartog (1995) found no evidence of zooxanthellae in his studies of various species in the Mediterranean, yet Doumenc et al. (1989) described Telmatactis carlgreni as zooxanthellate which would be a unique occurrence within the genus. 

No evidence of zooxanthellae was found in a tentacle section of Telmatactis sp., however only the tip was able to be removed in this case. These microorganisms have been known to reside commonly in tentacles and the oral disc, but can also be found in the column and septa (Ruppert et al., 2004). Thus it cannot be ruled out that the individual described here possesses symbiotic zooxanthellae. 

Actiniarians are capable of both sexual and asexual reproduction, however there is little to no information on the reproductive nature of the Telmatactis genus. 

In terms of sexual reproduction, anemone species are either gonochoric or hermaphroditic (Ruppert et al., 2004). Gonads are located between the septal filaments and retractor muscles of some mesenteries, and in the case of Telmatactis only the primary mesenteries are fertile (den Hartog, 1995). Mature gametes are released into the coelenteron and typically spawned though the mouth and fertilised externally (Ruppert et al., 2004). 

Asexual reproduction occurs through either longitudinal fission or fragmentation in which the fragments or halves develop into fully functional, but genetically identical. These may form close colonial aggregations or disperse away from the original anemone (Shick, 1991).

There are a number of costs and benefits to both kinds of reproduction. Asexual proliferation increases fitness by increasing biomass of both individuals and gonads while decreasing the risk of extinction by dividing the chance of mortality across numerous individuals (Shick, 1991). Sexual reproduction on the other hand breaks down genotypes that have developed successfully in native conditions but will result in greater fitness if the new progeny successfully disperses and reproduces in a different habitat (Shick, 1991).

Likewise to reproduction, there is little information available on the developmental processes of Telmatactis specifically. However the primitive condition of oviparous planktotrophic development is most common among actiniarians and allows widespread dispersal (Shick, 1991). The planula larvae swims with its aboral end forward and settles by reading sensory cues via well-developed cilia (Ruppert et al., 2004). Little is known about the exact nature of these cues, and in some cases larval settlement is unable to be observed or visibly induced (Shick, 1991). Metamorphosis of tentacles and septa occur prematurely upon its aboral end and develops into a mature polyp (Ruppert et al. 2004). 

Being an opportunistic predator and generally sessile, anemones have little in terms of energetic costs and as a result they are able to maximise their ability to grow and reproduce (Shick, 1991). As the individual grows the number of mesenteries multiply to support the increase in body mass, and as a result, additional tentacles also form. Small intertidal species are more at risk to desiccation, predation and competition and as such may have selected for rapid growth rates through size-dependent mortality (Shick, 1991).

Despite being obligate predators, their sessile nature means they rely on prey movement and currents for capture of various invertebrates (Ruppert et al., 2004; Thorington et al., 2010). Anemone feeding behaviour has developed primarily around the use of chemosensory cues, however tactile stimuli are also important (Shick, 1991). The anemone expands the oral disc and opens the mouth to protrude the actinopharynx in response to water soluble and organic compounds released by prey (Shick, 1991) (Figure 6). Feeding tentacles possess a number of specialised cells called cnidocytes which excrete stinging capsules (cnidae). Anemones possess two kinds; adhesive spirocysts and venomous nematocysts that penetrate and subdue prey (Fautin, 2009). However it has been found that nematocysts and tentacle mucus rather than spirocysts may actually be the primary mechanisms by which prey adhere to the tentacles so long as the prey is penetrable by discharged mastigophore tubules (Thorington & Hessinger, 1990). These cnidocytes are surrounded by sensory supporting cells (cnidocyte/supporting cell complex, CSCC) which house a number of chemo- and mechanoreceptors which mediate cnidae release. Three types have been described whereby differential signals are required for discharge (Table 1) (Thorington & Hessinger, 1990).

Table 1: Stimuli required for discharge of three classes of CSCCs in sea anemones (Adapted from Thorington & Hessinger, 1990)
	Stimulus Required for Discharge
CSCC Type	Physical Stimulus	Chemical Stimulus	Vibrating Stimulus*
Type A	X	X	X
Type B	X	X
Type C	X
*Targets must be vibrating at specific frequencies, as opposed to static targets

Once prey have made contact with feeding tentacles, extension and twitching of the tentacles occurs coupled with ciliary movement and muscle contractions to begin feeding and ingestion of prey (Shick, 1991). Figure 7 demonstrates this process where the tentacles lie outstretched prior to prey contact, after which tentacles contract and move towards the mouth to initiate ingestion of prey. Video 1 shows Telmatactis sp. performing these actions by feeding on a gastropod. 

Once prey is swallowed by the mouth, it is combined with mucous and moved slowly through the pharynx and into the coelenteron through ciliary action and peristaltic contractions (Ruppert et al., 2004). Digestion then occurs extracellularly through discharge of nematocysts to paralyse and inject venom or enzymes into prey, as well as protease and lipase release from enzymatic gland cells located on the cnidoglandular band (Ruppert et al., 2004). Macromolecules and food particles are absorbed and phagocytised by gastrodermal cells while indigestible components are circulated out through the pharynx via ciliary currents (Shick, 1991; Ruppert et al., 2004). See Figure 3 in Internal Morphology for more detail.
Video 1: Visualisation of Telmatactis sp. subduing (4 times speed) and ingesting (6 times speed) a species of gastropod.

Anemones which attach to hard substrates (like Telmatactis), glide across surfaces through muscular contractions of their pedal disc (Ruppert et al., 2004) and possibly with the aid of the hydrostatic skeleton. Telmatactis sp. has been observed to expand one side of its pedal disc to move across the substrate as demonstrated in Video 2.

Video 2: Visualisation of Telmatactis sp. using pedal disc at 6 times speed to glide across the substrate.

Members of Actiniaria such as Telmatactis are highly muscular, and maintain their size and shape through a hydrostatic skeleton. By keeping the mouth closed, anemones can contract muscles and transmit this force to the body wall in order to move and change shape (Shick, 1991). Conversely, opening the mouth releases the compressed fluid and allows the anemone to deflate and draw in its tentacles and protect the oral disc, as in the retraction-deflation response to potential threats (Ruppert et al., 2004). This sequence is demontrated in Video 3 by Telmatactis sp.

Anemones possess a number of muscle fields; longitudinal, radial, circular and oblique, which all aid in various forms of movement and locomotion (Figure 8). Columnar circular muscles contract to allow extension, while peristaltic contractions flush out the coelenteron and expel waste and gametes (Shick, 1991). Radial transverse muscles of the mesenteries regulate the opening of the mouth while radial basilar muscles are used in locomotion by effecting release of the pedal disc (Shick, 1991). In terms of the retraction-deflation sequence, a combination of all of these muscular fields are involved. The strong longitudinal retractor muscles are responsible for the symmetrical withdrawal of the oral disc and tentacles towards the pedal disc (Ruppert et al., 2004). This, combined with the release of fluid from the coelenteron, allows the deflated tentacles and oral surface to fit within the column and sphincter muscles around the upper column close like a drawstring over the invaginated oral surface (Shick, 1991). Beating of siphonoglyph cilia aid in the reinflation of the polyp and hydrostatic pressure then returns the pharynx back to its laterally compressed and sealed state (Ruppert et al., 2004). 
Video 3: Visualisation of retraction-deflation sequence of Telmatactis sp. at 2 times speed.

Due to their thin, epithelial body plan, actiniarians have no specialised structures designed specifically for either respiration or excretion and rely instead on diffusion across the body and tentacles (Ruppert et al., 2004). As their internal cavity is usually also filled with water, no cell is far from the “external” environment (Shick, 1991). This process is facilitated by ciliary currents across the gastro- and epidermis (Ruppert et al., 2004) (Figure 9).

Members of Cnidaria receive their namesake from the unique structures they possess called cnidae. These capsules are secreted from cells and are used in prey capture and defence by everting a tubule which may be armed with spines, venom or adhesive threads (Fautin 2009; Ruppert et al., 2004). There are three commonly recognised groups of cnidae; nematocysts, spirocysts and ptychocysts, and the specific types (cnidom) within these groups are useful in describing and distinguishing species (Fautin, 2009). 

Sea anemones are typically understood to possess nematocysts and spirocysts, spirocysts being a defining feature of the Hexacorallia (Ruppert et al., 2004) (Table 2). 60% of anemone genera possess the same three types; spirocysts, basitrichous isorhiza nematocysts (basitrichs) and microbasic p-mastigophore nematocysts (Shick, 1991), and Telmatactis sp. is no different. 

Spirocysts exhibit characteristic spiral coiling inside the thin-walled capsule, and discharge by everting the capsule in response to stimuli (Moore, 1993). Threads extend from the released tubule like bristles and solubilise upon release to form an adhesive mesh (Moore, 1993; Ruppert et al., 2004). Nematocysts are thick-walled, and universal across all Cnidarians. They usually possess spines or barbs which are released after release of the hinged lid (operculum) (Ruppert et al., 2004). 

Despite this consistencies across their cnidoms, the size, shape and distribution of these cnidae within the individual are important taxonomic descriptors for a number of species. Although it is important to note that huge diversity still remains with both established and theoretical links to anemone size, life stage, geography, phylogeny and ecology (Fautin, 2009). 

Table 2: Distribution of spirocysts and nematocysts in various structures of Telmatactis panamensis, X indicates presence (Adapted from Fautin et al., 2007)
Location	Spirocysts	Basitrichs	Microbasic p-mastigophores
Tentacles	X	X	X
Actinopharynx		X	X
Mesenterial Filaments		X	X
Acontia		X	X
Column (Scapulus)		X	X

Tentacles

The tentacles of anemones tend to be packed with cnidae as they are frequently involved in prey capture and also provide defence from attacks. Prey are penetrated and/or adhered to the tentacle to facilitate transmission of toxins and transfer of prey to the mouth (Thorington & Hessinger, 1998). As such, tentacles tend to possess both spirocysts and nematocysts (Fautin, 2009). 

The tip of a more centrally orientated tentacle was removed from Telmatactis sp. and observed under a light microscope (Figure 10). Evidence of undischarged spirocysts (faint with helical structure inside) and basitrichs (darker, slender, slightly curved) were found in high densities. A few microbasic p-mastigophores were also found, however these may have originated from acontial threads (see Acontia) which were recently extruded from the sampled tentacle. Spirocysts are present only in the tentacles (Fautin et al., 2007) and generally in higher abundance than nematocysts which suggests that they must be the primary effectors in prey adhesion to the tentacles (Shick, 1991). However this may not always be the case as shown by Thorington & Hessinger (1990) where nematocysts appear to be the principal contributor to adhesive force to probes coated in anything less than 20% gelatin. This is theorised to be attributed to the inability of spirocysts to adhere to “softer” objects, and as such the relative contributions of the two cnidae even out as gelatin coating increases. However above 40% gelatin, spirocysts become the primary adhesive contributor due to the inability of nematocyst tubules to penetrate the hard target (Thorington & Hessinger, 1990).