The chambered nautilus (Nautilus pompilius), of the family Nautilidae, is native to the Indo-Pacific region of the ocean. It is present in waters that span from the Andaman Islands and the Philippines in the north, with Fiji and Australia at the southern end of the range (Reyes 2016). N. pompilius lives deep in the ocean above coral reefs and is sometimes found as deep as 750 m (2,460 feet). However, it cannot travel lower than 800 m (2,625 feet), as this could cause the shell to implode. The species also cannot survive temperatures above 25˚C (77˚F) (Jereb and Roper 2005).
Adult N. pompilius exhibits slight size differences between the sexes. Male average diameter is 131.9 mm and females average 118.9 mm (Dunstan, Ward and Marshall 2011). It is difficult to get an accurate weight for the species because there are differing amounts of seawater within its shell at a given time. Studies of N. pompilius in the Philippines reported an average weight of 850 g (30 ounces) for a large specimen (diameter of 165 mm) (Saunders and Landman 2009). The body of N. pompilius is contained within a spiral shaped shell that is a pearly white color with deep crimson stripes. This external shell is unique to the nautilus and has not changed much from its ancestors 500 million years ago. Within the fully matured shell, there are 30 – 38 chambers. The nautilus’ body occupies only the first segment, while the chambers behind are filled with gases and fluid (Cerullo 1997), which allow it to float and travel above the ocean floor (Lemanis, Zachow, Fusseis and Hoffmann 2015). When first hatched, the juvenile nautilus only possesses seven chambers (Saunders and Landman 2009). In this stage, N. pompilius lives near the floor of the sea and is entirely covered in stripes to help them camouflage themselves. Adult N. pompilius’ stripes become concentrated only on the tops of their shells to better camouflage them in their new habitat in the water column.
N. pompilius remains generally unobserved in its natural deep sea habitat, therefore, most of the information about behavior and life history comes from aquariums that breed them (Dunstan, Ward and Marshall 2011). N. pompilius is mainly a solitary animal (Basil et al. 2002) that remains at the bottom of the sea during the day and travels vertically into more shallow depths at night to find prey. A carnivore, the N. pompilius feeds on molted shells, the carcasses of dead animals, as well as fish, crabs and other crustaceans. N. pompilius catches food in its adhesive tentacles and transfers it to its mouth. Here, the strong jaws crack through the shells of prey (Saunders and Landman 2009).
When threatened, the nautilus can retract completely into its shell and hide behind its leather-like hood (Jereb and Roper 2005). To travel, this species controls the concentration of gases and sea water within its chambers to achieve buoyancy (Lemanis, Zachow, Fusseis and Hoffmann 2015). The nautilus also utilizes jet propulsion by forcing water out of the funnel beneath its tentacles, in order to move up and down in the water column. The siphuncle is a separate structure within the chambers that allows fluid to flow in or out, to maintain buoyancy at different water depths (Saunders and Landman 2009). The chambered nautilus has very poor eyesight and finds its food using its tentacles’ ability to detect scent (Crook and Basil 2008). Although it lacks the degree of brain development of octopi, squids and cuttlefish, the nautilus does have the ability to learn simple associations, such as the connection between a pulsing light and feeding time. Through laboratory studies, this animal has been proven to employ both short- and long-term memory (Crook and Basil 2008).
During the mating process, the male nautilus uses his spadix, a structure made up of four combined tentacles, to deliver sperm to the female (Jereb and Roper 2005). The female lays 10 fertilized eggs annually, which measure up to 45 mm (Eldredge and Stanley 2012). Females are seen sticking the eggs to hard surfaces with their tentacles (Jereb and Roper 2005). It takes 10-12 months for the eggs to hatch (Dunstan, Bradshaw and Marshall 2011). When newly emerged, N. pompilius measures approximately 23 mm in diameter (Saunders and Landman 2009). Juveniles in captivity are observed to consume small shrimp soon after hatching (Jereb and Roper 2005). The nautilus has a slow rate of development. The species reaches maturity roughly 15 years after hatching and has a life expectancy of more than 21 years. (Dunstan, Ward and Marshall 2011).
Although N. pompilius is preyed upon by sharks, fish and octopi, human harvesting is the main danger to its population size (U.S. Fish and Wildlife Service 2016). Populations are considered vulnerable to extinction due to loss of natural habitat, low reproduction rate and over-harvesting (De Angelis 2012).The beauty of its shell has caused the chambered nautilus to be a target for profit. Some isolated populations of the nautilus have seen 100% reduction after just two years of over-fishing.Even in locations untouched by harvesting, it is estimated that only fifteen nautiluses are present per square kilometer of habitat (.386 square miles) (U.S. Fish and Wildlife Service and National Oceanic and Atmospheric Administration Fisheries 2016). N. pompilius was previously not a protected species due to a lack of knowledge regarding the international population size (De Angelis 2012). During the 2016 Convention on International Trade in Endangered Species of Wild Fauna and Flora, it was finally agreed that the entire Nautilidae family would become listed as species requiring international controls on harvesting (Convention on International Trade in Endangered Species 2016).
The chambered nautilus (Nautilus pompilius), of the family Nautilidae, is native to the Indo-Pacific region of the ocean (Reyes 2016). N. pompilius lives in the sea above coral reefs and is sometimes found in habitats as deep as 750m (2,460 feet) (Jereb and Roper 2005). Adult male nautiluses reach an average diameter of 131.9 mm (5 3/16 inches), while females reach an average of 118.9 mm (4 11/16 inches) (Dunstan, Ward and Marshall 2011). The body of N. pompilius is contained within a spiral shaped shell that is a pearly white color with deep crimson stripes on the top and solid white underneath. Juveniles are striped over their entire shells. Chambers contained within the center of the shell are filled with gases and seawater which allow the species to be buoyant (Lemanis, Zachow, Fusseis and Hoffmann 2015). The nautilus can also swim and travel via jet propulsion. Generally, these animals travel to shallower depths at night to feed on crustaceans and carrion, which they locate using their odor-sensing tentacles (Saunders and Landman 2009) (Crook and Basil 2008¬). N. pompilius employs both short- and long-term memory and is able to learn simple associations (Crook and Basil 2008¬). The chambered nautilus utilizes internal fertilization and lays approximately ten eggs each year (Eldredge and Stanley 2012). These eggs take 1 year to hatch, while the animal takes 15 years to mature and lives over 21 years (Dunstan, Bradshaw and Marshall 2011) (Dunstan, Ward and Marshall 2011). Because of its low reproductive rate and slow life history, N. pompilius is in danger of extinction due to over-fishing to supply the demand for nautilus shells (De Angelis 2012). After the elimination of several local nautilus populations, it was agreed in 2016 that international controls would be enforced over trade of this species. (De Angelis 2012) (Convention on International Trade in Endangered Species 2016).
Its relatives the ammonoids dominated the oceans for millions of years before going extinct along with the dinosaurs 65 million years ago – but the nautilus came through that disaster and is still with us today...
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