The weird, wonderfully-designed sawfish
It is not hard to tell where the sawfish gets its name—the long snout (‘rostrum’) covered with tooth-like ‘denticles’ is one of its most distinctive features. And it is not only for show; it is a dangerous weapon, both to other fish and to fishermen who can be injured by a sawfish as it tries to resist being caught! In the same family as rays, there are approximately five living species of sawfish, all listed as endangered. They have been subject to overfishing, as their rostrums are both in demand as curios and used in traditional medicine. Their fins are also considered a delicacy. In addition, their habitat has been severely reduced (juveniles spend most of their time in shallow water bays and estuaries) and they are often accidentally caught, as their toothy snouts easily snag in fishing nets.
Sawfish can be found in the Atlantic, Pacific, and Indian oceans. The dwarf sawfish, Pristis clavata, only reaches about 1.5 m (5 feet) in length. The others are much larger, often reaching 7 m (23 feet).
Along with sharks and rays, sawfish belong to a class of animals called the Chondrichthyes (cartilaginous fishes). They are actually grouped with rays in superorder Batoidea and have several characteristics in common with them, including the fact that both the mouth and gills are on the bottom of the animal. The characteristic denticles on the sawfish’s rostrum are not true teeth, but modified scales—the sawfish does have teeth in its mouth.1 The rostrum has electrical and mechanical sensors that detect slight movements, allowing it to stalk prey in murky water.2 When it encounters something that seems tasty, it thrashes its rostrum about, stunning and/or wounding the prey. It can also use the rostrum to probe for shellfish in soft sand and mud, and it can temporarily pin fish to the bottom before sucking them into its mouth. The rostrum is also a defensive weapon against sharks.3
|Knifetooth sawfish||Anoxypristis cuspidata||Bays and estuaries in the Indian Ocean, as far west as Arabia, and in the western Pacific, from Japan to Australia||No denticles at the base of the rostrum|
|Queensland/Dwarf sawfish||Pristis clavata||Northern/tropical Australia||The smallest member of the sawfish family|
|Smalltooth sawfish||Pristis pectinata||Atlantic ocean||Can occasionally reproduce parthenogenically|
|Longcomb sawfish||Pristis zijsron||Indian ocean as far west as Africa, Western Pacific from China to Australia||The largest member of the sawfish family|
|Common/largetooth sawfish||Pristis pristis, P. microdon, and P. perotteti||Indo-Pacific, East Pacific, and Atlantic||There is some contention about the status of these three species, thus many scientists talk about the Pristis pristis species complex|
Like sharks and rays, sawfish skin is covered with dermal denticles—tiny scales that help reduce friction from the water as the sawfish swims. If you rubbed the skin from the snout to the tail, the sawfish would feel very smooth, but if rubbed the other way, would feel rough. Scientists have learned to mimic this amazing design, leading to new applications like super–drag-resistant boat hulls and even swimsuits.4
Like several other species within class Chondrichthyes, sawfish are ovoviviparous:5 mothers give birth to live young, but the babies grow in eggs that hatch inside the mother. The sawfish usually gives birth to about eight young at a time. The teeth do not fully erupt until after birth, and the rostrum is sheathed in tissue until after birth.6 This is a wonderful design mechanism that prevents the mother from being injured.
Another interesting fact about sawfishes is that most of them are euryhaline: they can move back and forth between fresh and salt water and sometimes can be seen far upstream in tropical lakes and rivers. Actually, there are many fish species that can tolerate a wide range of salt levels, even if they prefer one over the other. So many fish could have survived the potentially wide range of salinity in Noah’s Flood with no problem.7
In the fossil record, modern sawfishes appear fairly ‘late’. Evolutionists say they first appear about 60 million years ago in rocks classified as Paleogene.8 There is a slightly different type of sawfish found earlier in Cretaceous rocks,9 which evolutionists would date to 145 million years ago. Creationist geologists would consider all of these rock layers to have been deposited around the time of Noah’s Flood, which was about 4,500 years ago. There may have been two types of sawfish living in the pre-Flood world that were buried at different times during the Flood. Or the modern-looking sawfish fossils are from post-Flood deposits. Or the two are really different versions of one species. This is an area of ongoing creationist research. Whatever the reason, the main difference between modern and ancient sawfishes is size (the old ones were larger), but there are also differences in the size and spacing of the rostral denticles. Also, the denticles in Cretaceous sawfish were attached to the rostrum with connective tissue, while modern sawfish teeth are embedded in sockets. Thus, the Cretaceous sawfish may have been able to regrow these denticles, unlike modern sawfish. While evolutionists believe that Cretaceous and modern sawfish are not closely related (they are said to have evolved independently from the guitarfish10), there is no reason that they could not be part of the same created kind. Note also that, like in so many other cases, the Cretaceous sawfish appears fully-formed with no fossil evidence of its ‘evolution’ from earlier forms. There is also a ‘sawshark’ living today. It looks similar to the sawfish in many ways, but they are clearly distinct. For instance, the sawshark’s gills are on the sides, like a shark.
As is the case for many marine organisms, the Flood resulted in a loss of diversity in the sawfish kind. While representatives of every kind of land animal went aboard Noah’s Ark, this was not the case for marine creatures like the sawfish. John Woodmorappe says it is probable that “present-day marine life is but an impoverished remnant of that which had originally been created and had existed before the Flood.”11 In fact, it is possible that many types of sawfish existed before the Flood and only one main type survives today.
Recently, researchers were surprised to find that sawfish occasionally reproduce via parthenogenesis, i.e., without any male contributing genetic material. This was surprising, because ‘virgin births’ have been documented in very few vertebrates. But DNA fingerprinting of a sawfish population in Florida revealed that about 3% of the population came from parthenogenesis.12 This is an amazing survival strategy for females to use when mates are scarce, but we do not yet know if these parthenogenic offspring are fertile. How does it happen? Toward the end of the process of egg formation in animals (called ‘oogenesis’), the cell divides unevenly. This leads to a larger ‘egg’ and a smaller ‘polar body’, which generally dissolves. It appears that an unfertilized egg in sawfish can combine with a polar body, but since no male was involved the process can only lead to the birth of female fish. Also, fish produced via parthenogenesis have less genetic diversity than the mother.13 Thus, if this is designed to enhance the survival of the species, it is only a short term fix.14
All living species of sawfish are protected internationally by the Convention on International Trade of Endangered Species (CITES), which makes it illegal to sell sawfish parts internationally. National laws vary, but it is illegal to harvest sawfish in Australia, Brazil, the United States, and some other countries.15
Conservation groups are trying to help the sawfish avoid extinction. Such efforts have been successful with other species such as the bald eagle and the gray wolf, but the fact that sawfishes live underwater, and often in muddy water where they are hidden from view, makes conservation much more difficult. As biblical creationists, we believe that God made mankind the steward of creation (Gen 1:28). This includes sawfish, and so we should be concerned that these wonderful animals are threatened with extinction, though we need to reject the idolatry of nature that many environmental groups teach. We can hope that the sawfish is around to testify to the ingenuity of its Creator for many years to come.
References and notes
- Seitz, J., Sawfish biology; flmnh.ufl.edu. Return to text.
- Wueringer, B. et al., The function of the sawfish’s saw, Current Biology 22(5):R150–R151, 6 March 2012. Return to text.
- Fisheries fact sheet: sawfish, Government of Western Australia Department of Fisheries, April 2011; fish.wa.gov.au. Return to text.
- Bhushan, B., Biomimetics inspired surfaces for drag reduction and oleophobicity/philicity, Beilstein Journal of Nanotechnology 2:66–84, 2011. Return to text.
- Cf. Seitz, Ref. 1. Return to text.
- Sawfish; elasmoworld.org. Return to text.
- Also, due to a difference in density, freshwater can float on saltwater, often for long periods of time without mixing. See also creation.com/fish-plants-survive-flood. Return to text.
- The former name for the Paleogene was “Tertiary”. Return to text.
- Seitz, J., Amazing sawfish of the past, ANAMAR News; 12 July 2013; anamarinc.com. Return to text.
- Sawfish fossils span the famous “K-T boundary” (after which dinosaur fossils, for example, have not been found). This is one reason evolutionists say they must have evolved twice. Return to text.
- Woodmorappe, J., Noah’s Flood: A Feasibility Study, p 142, Institute for Creation Research, El Cajon, CA, 1996. Return to text.
- Devlin, H., Sawfish escape extinction through ‘virgin births’, scientists discover, The Guardian 2 June 2015; theguardian.com. Return to text.
- Due to chromosomal recombination during early meiosis, large portions of the egg and polar body will carry identical parts of the same chromosomes. Return to text.
- Zielinski, S., ‘Virgin births’ won’t save endangered sawfish, ScienceNews, 5 June 2015; sciencenews.org. Return to text.
- Sawfish conservation; sawfishconservationsociety.org. Return to text.