Turbo haynesi is a common marine gastropod snail that can be found in tropical and subtropical Australia, reaching north-westwards of Hervey Bay in south Queensland to Geraldton in Western Australia (Beesley, Ross, & Wells, 1998; Ponder, 1978). It belongs to the turban snails and is a browser and grazer, feeding on several types of algae. Reproduction happens between separate sexes and young develop directly in egg-masses laid by the females. Predators include carnivorous gastropods, sea stars, lobsters or even octopi. Snails are known to live in association with other animals, sometimes even as hosts and their anatomy follows a typical marine gastropod body plan. 
 

In Prestons original paper (1914), he describes T. haynesi as a subspecies of Turbo foliaceus but since then T. haynesi has been considered adistinct species. The main physical descriptions were made on features of the shell and the operculum. The shell is described as turban shaped and imperforate, colouration alternates between yellowish-pink and dark-greenmarkings. The whole shell contains 5 to 6 whorls with two tubercular large outer ridges (carinae), several fine spiral ridges (lirae) and fine spiral shallow incised grooves (striae). Both, carinae and lirae numbers are increased on the last whorl towards the convex base of the shell. The aperture is roundly ovate with an acute labrum and can range from 16 to 29mm in diameter. The columella, the central spiral structure of the shell, has iridescent inner margins, outer margins covered in thick white callus and is descending in acurved manner. The multi-spiral operculum contains a sub-central nucleus and aslightly convex columellar side. The surface is weakly granulated and consists of two distinct furrows. The colour is mostly white but can also appear light-brown or greenish. Shell sizes can reach up to 35mm in height and 31mm indiameter (Ponder, 1978; Preston, 1914).

The snails’ soft body external features are represented in an illustration of Turbo fluctuosus (Figure 4). They can be broadly applied to other species in that family. The epipodium, a fold along either side of the gastropods foot, is intermediately pronounced and the attached epipodial tentacles are stubby and short. Alongside broader neck lobes with simple margins, cephalic lappets are present and the snouts oral disc ends in a pronounced pseudoproboscis. Its function is unknown (Beesley et al., 1998).

Habitat

Little is known about the ecology of Australian Turbinidae species. Generally they are believed to strongly influence community structures since they are part of the most abundant and largest herbivorous species on rocky shores and intertidal zones (Beesley et al., 1998). The species Turbo smaragdus for example has been found to migrate with tidal changes in New Zealandia mangrove-seagrassestuaries and thereby influence zones of seagrass, algae and pneumatophores (Alfaro, 2006). Changes in diet have been found to impact growth rate and reproductive fitness in Turbo sarmaticus (Foster, Hodgson, & Balarin, 1999). The density and average sizes of Turbo in Australian studies has been shown to be correlated with the percentage cover of coralline algae and water depth. Turbo are believed to have a strong relationship with Corallina algae in both micro- and macrohabitats. It provides habitat, shelter and food. It has been established however that Turbo diets vary and thus the association with that type of algae as well (Worthington & Fairweather, 1989). It has been proposed that food source availability itself in form of for example algae is more important than presence of a specific food source because the rhiphidoglossan type radula enables access to a wide variety of food resources (Ramesh & Ravichandran, 2008). T. haynesi might therefore be less specialized on Corallina algae and opportunistically feed on any available algae like the closely related species T. bruneus. A lesser association with this algae might also suggest broader habitat availability of T. haynesi.

Predators

Turban snails have been found to be predated upon by predatory gastropods, sea stars (Vermeij & Williams, 2007; Worthington &Fairweather, 1989), lobsters (Van Zyl & RF, 1998) or even octopi (Steer & Semmens, 2003). The operculum is used as defence against predation and serves as a shield with its hardly calcified structure. Instead of fleeing, the snails retract into their shell and opercula prevent predators to break the shell at the outer lib. Operculumthickness was even found to increase towards tropical regions which correlated with passive armour being more common and better developed in the tropics (Vermeij & Williams, 2007).

Epibiosis

Space is often a limiting factor in colonizing marine habitats. Especially reliance on hard substrata can be difficult because competition is high. Gastropod shells are providing additional hard substrata islands in space-limited habitats. They often become hosts (basibionts) for numerous sessile species of for example algae, polychaetes or cnidarians. These epibionts can either positively or negatively affect the host (Wernberg, Tuya, Thomsen, & Kendrick, 2010) Turban shells are no exception in this regard. In fact, almost all T. haynesi specimens present in the aquaria of the University of Queensland had encrusting algae growing on their shells and in some cases anthozoans and polychaetes were observed too. Often enough even small crustaceans were found in immediate proximity of the shells. To test if there was an interesting association between crustaceans and T. haynesi shells, a little experiment was conducted in which 15 individuals were collected from the aquarium in separate containers. The presence of crustaceans in close proximity was then assessed.

Reproduction

Turbo snails are known to be dioecious with an even sex ratio (Joll, 1980), meaning that reproductive organs are present in separate individuals. Females of the Turbinidae family lay gelatinous egg-masses and usually free-swimming larvae are known to hatch from these (Wilson & Gillett, 1974). However, as shown in figures 10 and 11, T. haynesi young seem to be developing directly since an early shell is forming while they are still in their eggs. Direct developing species have been found to have more locally closed populations since their dispersal capabilities are reduced compared to species that have a free-swimming larval stage (Hoskin, 1997). This might also be one explanation why populations in Western Australia and Queensland are hard to identify as one species. Many species names have been found to be synonyms (Wilson & Gillett, 1974).

Behaviour

Prosobranchia, a gastropod subclass that T. haynesi is a part of, move themselves forward via muscular contractions of their foot. Waves are thereby moving in the opposite direction of movement (Chase, 2002; Miller, 1974). T. haynesi are grazing snails that use their radula to move food particles up their mouths through protraction and retraction (Chase, 2002). Video 1 (Figure 15 Thumbnail) demonstrates a snail that is grazing on the glass of an aquarium. T. bruneus, a closely related species of T. haynesi with similar Radula morphology, seems to be an opportunistic feeder with no specific algal preference (Ramesh & Ravichandran, 2008). Their diet mainly depends on the availability of algae in their environment. They are also unable to remove large quantities of algae due to weak musculature and their radulae mainly serve as brooms that sweep filamentous algae and microalgae off the ground (Ramesh & Ravichandran, 2008). Snails have also been observed to aggregate in the aquaria and every time they were taken out together in a container. They were mostly crawling on top of each other’s shells. Aggregation is believed to reduce predation rates compared to randomly distributed animals, suggesting that individual safety is gained by increased numbers (Ray & Stoner, 1994). 

External and Internal Anatomy

Something unique to the gastropods is the rotation of the visceral mass by 180̊ during development. This process is called torsion. It occurs in all gastropods and opistobranchs can even secondarily be de-torted. Torsion does not involve the coiling of the shell. Both processes however lead to the asymmetry in most gastropods. Reorganisation of various organs is the result. Therefore some snails even defecate into their own necks.

CirculatorySystem

The gastropods’ circulatory system is open and the heart pumps hemolymph through the body to get oxygen to every organ. The hemolymph contains a respiratory pigment called Hemocyanin which carries the oxygen and appears blue.

RespiratorySystem

Marine gastropods like T. haynesi breathe through gills but other gastropods are known to possess pallial lungs or secondary gills. Although most gastropods’ respiratory protein is hemocyanin, some have haemoglobin instead.

Excretory System

Nephridia are the primary excretory organs of gastropods. As a waste product they can either produce uric acid or ammonia depending on the species and in freshwater or terrestrial species they play an important role in osmoregulation. Some species even possess additional organs with excretory purposes like pericardial glands or digestive glands with connection to the stomach.

Nervous System

Even though gastropods can see with their eyespots on the upper tentacles, their primary sense is olfaction which they detect through receptors on their tentacles’ epithelium. Aside from vision and smell they can also detect gravity with statocysts and touch through mechanoreceptors. Gastropods are unable of detecting sound. Visual systems can vary from simple light and dark detecting ocelli to more complex pit eyes and even lens eyes. Gastropods’ nervous systems are divided into central and peripheral, including several types of ganglia. Torsion can often lead to crossovers of certain ganglia.

Digestive System

Gastropods can have a variety of different digestive systems with major differences associated with their diet and the adapted radula morphology. T. haynesi is a grazing herbivore and has little teeth that wear off and can regrow, able to rasp algae off of substrates. Some burrowing predatory marine gastropods possess a siphon. It extends out from the mantle’s edge and is used to "taste" the water for prey detection.

The information of the section above has all been obtained from Valdez, W. (2012). Gastropods and their study.New Delhi: Research World.

Radula

The gastropod radula is the feeding organ of snails, a morphologically important feature and valuable for identification. Therefore, Scanning Electron Microscopy has been used to obtain an image of the radula for comparison and classification. The radula was dissected out of a previously fixed specimen’s head. The radula was then cut into smaller sections, cleaned from organic material, flattened with a brush, dried and mounted onto a stub.

Turbinids’ feeding biology has rarely been studied in the past. Gastropods generally have a variety of feeding mechanisms (Chase, 2002) and observations of a species’ radulae can yield information about feeding habits and food preferences (Ramesh & Ravichandran, 2008). Turban snails are browsers and grazers with varying preferences to different kinds of algae. The Radula of T. bruneus has recently been studied to find out algal preferences in regards to potential aqua cultural use. Since radulae are unique to every species, the morphology is a valuable characteristic for identification. However, it has been pointed out that T. haynesi and T. bruneus are hard to distinguish from each other (Wilson, 1993). Radulae of both species seem to have a similar morphology and therefore information about the previously studied radula of T. burneus can be applied to T. haynesi. T. bruneus’ radula consists of a large central tooth, five lateral teeth and many marginal teeth. It was found to be from the rhiphidoglossan type (Ramesh & Ravichandran, 2008). The same features are present in the radula of T.haynesi as shown in figures 17 and 18.

Members of the Turbininae subfamily are distributed worldwide in tropical or subtropical regions, intertidal to bathyal depths and usually restricted to hard substrates with calcium carbonate affinity (Hickman & McLean, 1990; Wilson & Gillett,1974). In Australia turbinines occur around the entire coastline but T. haynesi is believed to be distributed along the northern coast spanning from southern Queensland north-westwards to Geraldton in WesternAustralia (Beesley et al., 1998; Ponder, 1978) including close islands like Montebello Islands (Preston, 1914). 

Kingdom: Animalia
Phylum: Mollusca
Class: Gastropoda
Subclass: Vetigastropoda
Order: Trochida
Superfamily: Trochoidea
Family: Turbinidae
Subfamily: Turbininae
Genus: Turbo
Species: Turbo haynesi

The Family Turbinidae is closely related to and the sister group of the Tegulidae and deeply nested inside the Trochidea superfamily. Previously, molecular phylogenies have disagreed on the monophyly of the Trochoidea and it has been suggested that this superfamily is actually paraphyletic (Uribe, Williams, Templado, Abalde, & Zardoya,2017).

Many primitive pleurotomariacean features are still present in the gastropod family Turbinidae. Differentiation and specialization of the rachidian tooth, reduced number of teeth in the central complex and specialization and complexity of tooth bases, shafts and cusps are distinct features regarding the radula. The long-growing edge of the operculum and the family members’ ability to add calcium carbonate to the operculum is a major hallmark. Fossil records date from the Permian and members have been tied to carbonate substrates ever since (Hickman & McLean, 1990). Unique features of the subfamily Turbininae include reduction of the rachidian and lateral teeth, radular asymmetry, inner marginal cusp enlargement, a specially derived pseudoproboscis and bicarinate juvenile shells (Hickman & McLean, 1990).

T. haynesi as a species has not been mentioned as being endangered or extensively threatened and no studies on this species’ conservation have been done so far. However, general issues like global warming could even be discussed for this snail since tropical species are vulnerable to ongoing change in temperature. Ectotherms that cannot flee from drastic environmental changes are especially confronted with mass mortalities (Chapperon & Seuront, 2011). A conservational approach discussing the protection of intertidal breeding grounds could also be applied to T. haynesi. The deposition of gastropod egg masses of several species has been studied and the creation of intertidal protected areas has been suggested. Direct developing species as suggested for T. haynesi deserve special attention since their dispersal is reduced and vulnerability increased compared to other species (Benkendorff & Davis, 2004).

Acknowledgments

I would like to thank John Healy from the QueenslandMuseum for his extensive efforts and assistance in identifying the species.

References

Alfaro,A. C. (2006). Tidal migration influences the zonation of grazing snails (Turbosmaragdus) in a mangrove-seagrass estuary, northern New Zealand. Estuaries and coasts, 29(5), 731-736.

Beesley, P. L., Ross, G. J., & Wells, A. (1998). Mollusca: the southern synthesis: CSIRO.

Benkendorff, K., & Davis, A. (2004). Gastropod eggmass deposition on a temperate, wave‐exposed coastline in New South Wales,Australia: implications for intertidal conservation. Aquatic Conservation: Marine and Freshwater Ecosystems, 14(3),263-280.

Chapperon, C., & Seuront, L. (2011). Behavioralthermoregulation in a tropical gastropod: links to climate change scenarios. Global Change Biology, 17(4), 1740-1749.

Chase, R. B. (2002). Behavior & its neural control in gastropod molluscs: OxfordUniversity Press on Demand.

Foster, G., Hodgson, A., & Balarin, M. (1999).Effect of diet on growth rate and reproductive fitness of Turbo sarmaticus(Mollusca: Vetigastropoda: Turbinidae). Marinebiology, 134(2), 307-315.

Hickman, C. S., & McLean, J. H. (1990). Systematic revision and supragenericclassification of trochacean gastropods: California, USA.

Hoskin, M. (1997). Effects of contrasting modes oflarval development on the genetic structures of populations of three species ofprosobranch gastropods. Marine biology,127(4), 647-656.

Joll, L. (1980). Reproductive biology of two speciesof Turbinidae (Mollusca: Gastropoda). Marineand Freshwater Research, 31(3), 319-336.

Miller, S. L. (1974). The classification, taxonomicdistribution, and evolution of locomotor types among prosobranch gastropods. Journal of Molluscan Studies, 41(3),233-261.

Ponder, W. (1978). THE UNFIGURED MOLLUSCA OF J.THIELE, 1930. Records of the WesternAustralian Museum, 6(4), 423.

Preston, H. (1914). Description of new species of landand marine shells from the Montebello Islands, Western Australia. Journal of Molluscan Studies, 11(1),13-18.

Ramesh, R., & Ravichandran, S. (2008). Feedingbiology with reference to algal preferance and scanning electron microscopystudies on the radula of Turbo brunneus. Trendsin applied Sciences Research, 3(2), 189-195.

Ray, M., & Stoner, A. W. (1994). Experimentalanalysis of growth and survivorship in a marine gastropod aggregation:balancing growth with safety in numbers. MarineEcology Progress Series, 47-59.

Steer, M. A., & Semmens, J. M. (2003). Pulling ordrilling, does size or species matter? An experimental study of prey handlingin Octopus dierythraeus (Norman, 1992). Journalof Experimental Marine Biology and Ecology, 290(2), 165-178.

Uribe, J. E., Williams, S. T., Templado, J., Abalde,S., & Zardoya, R. (2017). Denser mitogenomic sampling improves resolutionof the phylogeny of the superfamily Trochoidea (Gastropoda: Vetigastropoda). Journal of Molluscan Studies, 83(1),111-118.

Vermeij, G. J., & Williams, S. T. (2007).Predation and the geography of opercular thickness in turbinid gastropods. Journal of Molluscan Studies, 73(1),67-73.

Wernberg, T., Tuya, F., Thomsen, M. S., &Kendrick, G. A. (2010). Turban snails as habitat for foliose algae: contrastinggeographical patterns in species richness. Marineand Freshwater Research, 61(11), 1237-1242.

Wilson, B. (1993). Australian marine shells.Prosobranch gastropods. Part 1 (Prosobranch gastropods). 408 pp: OdysseyPublishing, Kallaroo, Western Australia.

Wilson, B., & Gillett, K. (1974). Australianshells illustrating and describing 600 species of marine gastropods found inAustralian waters-Rev.

Worthington, D., & Fairweather, P. (1989). Shelterand food: interactions between Turbo undulatum (Archaeogastropoda: Turbinidae)and coralline algae on rocky seashores in New South Wales. Journal of Experimental Marine Biology and Ecology, 129(1), 61-79.