The Identification, Structure, Care, and Conservation of Sawfish Rostra (Rhinopristiformes: Pristidae)

THE IDENTIFICATION, STRUCTURE, CARE, AND CONSERVATION OF SAWFISH ROSTRA (RHINOPRISTIFORMES: PRISTIDAE)

JESSICA BYLER

Conservation Department, University of Pennsylvania Museum of Archaeology and Anthropology, 3260 South Street, Philadelphia, PA 19104, USA Downloaded from http://meridian.allenpress.com/collection-forum/article-pdf/31/1-2/1/1506027/0831-4985-31_1_1.pdf by guest on 27 September 2021 [email protected]

Abstract.—Sawfish rostra are commonly found in historic natural science collections, yet there isa scarcity of guidance on their preservation. Rostra are cartilaginous with teeth-like scales. The function and structure of sawfish rostra as well as key mechanical and chemical issues need to be considered for their appropriate care in museum collections. Possible routes of decay are discussed, and methods for the care and conservation of rostra in museum collections are suggested. The species of sawfish can be determined by the morphology of the rostral structure. Physical damage, due to the nature of the material and from handling, often causes deterioration of rostra.

Key words.—sawfish rostra, rostrum, collections, conservation, identification Associate Editor.—Alana Gishlick

INTRODUCTION Sawfish are found in subtropical, shallow ocean waters around Australia, Africa, Indone- sia, India, and the Americas (Whitty et al. 2013, Dulvy et al. 2016). Like sharks, skates, and rays, sawfish are elasmobranchs. Active predators, sawfish use their rostra to detect, kill, and manipulate prey (Kirkland and Aguillon-Martinez 2002; Wueringer et al. 2009, 2012). Known for this unique neurocranial appendage, sawfish are culturally known as a novelty and their rostra have been widely collected (Fig. 1). Sawfish are culturally and monetarily significant. For many tribal societies, fromCen- tral America to Africa to Australia, the sawfish is represented in mythology, totemic iden- tity, and symbolism. From fighting to fecundity, the sawfish often represents protection and power (Fowler et al. 2005, Robillard and Seret 2006, Wueringer et al. 2009). Conse- quently, sawfish rostra are often found in ethnographic as well as natural history collections. However, little has been published on their care and conservation in private or museum collections. The international trade of sawfish materials, including rostra, fins, and teeth, has been banned since 2003 (Wueringer et al. 2009, Dulvy et al. 2016). However, these products are still highly valued and bought illegally (Fowler et al. 2005, Wueringer 2009, Dulvy et al. 2016). The demand for sawfish rostra and fins has allowed some fishermen to profit from killing these endangered species illegally. A single sawfish can be sold for a large amount of money as medicine, a curio, or foodstuff (Robillard and Seret 2006, Wueringer et al. 2009, Dulvy et al. 2016). As of 2014 in Brazil, individual rostral teeth were found to be sold for around US$200 (Dulvy et al. 2016), and whole sawfish were sold for several thousand dollars (Wueringer et al. 2009). The rostrum is often the only part of the fish retained as a souvenir. All species of sawfish are endangered and globally protectedFowler ( et al. 2005, Wueringer et al. 2009, Whitty et al. 2013, Dulvy et al. 2016). Easily caught in fishing nets, sawfish populations have severely declined in the last 50 yearsFowler ( et al. 2005, Robil- lard and Seret 2006, Whitty et al. 2013). Since 2007, sawfish have been included in CITES (Convention on International Trade of Endangered Species) Appendix I due to the drastic

Collection Forum 2017; 31(1):1–14 C 2017 Society for the Preservation of Natural History Collections 2 COLLECTION FORUM Vol. 31(1) Downloaded from http://meridian.allenpress.com/collection-forum/article-pdf/31/1-2/1/1506027/0831-4985-31_1_1.pdf by guest on 27 September 2021

Figure 1. Largetooth sawfish (Pristis pristis) rostrum from Bristol Museum and Gallery (no catalogue number). The proximal end is broken and several rostral teeth are missing. (Photo: author). decline caused by both intentional and incidental killings, indicating international agree- ment that sawfish are threatened with extinction (CITES 2013).

SAW F I S H SPECIES IDENTIFICATION Rostrum morphology, including width of the rostrum, internal canals, and rostral tooth shape, crown, and grooves, can be used to determine the sawfish speciesTable ( 1, Fig. 2). Biologists and conservationists use rostral morphology and measurements to identify sawfish, such as Whitty et al. (2013) for species found around Australia and Robillard and Seret (2006) in West African collections. The most common sawfish species, the largetooth sawfish, Pristis pristis (Linnaeus, 1758), has approximately 16 to 24 straight teeth on each side of the rostrum (Whitty et al. 2013). The rostral teeth have longitudinal grooves, but no crowns (Fig. 3) (Kirkland and Aguillon-Martinez 2002, Whitty et al. 2013). The largetooth sawfish rostrum tends to be longer than that of the smalltooth sawfish, Pristis pectinata (Latham, 1794), which has 22 to 34 straight rostral teeth on each side, with crowns but no longitudinal grooves (Whitty et al. 2013, Dulvy et al. 2016). Green sawfish, Pristis zijsron (Bleeker, 1851), have a similar number of rostral teeth to smalltooth sawfish, but the proximal teeth have partial longitudinal grooves as in largetooth sawfishWhitty ( et al. 2013). Dwarf sawfish, Pristis clavata (Garman, 1906), have around 18 to 27 teeth per side. The rostra of green sawfish and narrow sawfish, Anoxypristis cuspidata (Latham, 1794), tend to be narrower in relation to their width than those of the largetooth, smalltooth, and dwarf species. Nar- row sawfish have hook-shaped rostral teeth, whereas the other species have straight teeth (Whitty et al. 2013). The rostra of all species except the narrow sawfish have three internal canals running from the head of the sawfish to the proximal tip of the rostrum (Kirkland and Aguillon-Martinez 2002, Cicimurri 2007, Wueringer et al. 2009, Whitty et al. 2013). The narrow sawfish has five internal canals. The internal canals are visible on cut or broken edges of the rostrum.

STRUCTURE,MATERIAL, AND CHEMISTRY The anatomical properties of the sawfish skeleton, including the rostrum, are similar to those of rays, sharks, and skates, including teeth-like modified scalesHamlett ( 1999, 2017 BYLER—IDENTIFICATION, STRUCTURE, CARE, AND 3 CONSERVATION OF SAWFISH ROSTRA g a,d a a a,c a a g c,d 16–33 0.11–0.25 Spade or hooked Visible Absent Narrow 3.50 Indo-West Pacific Downloaded from http://meridian.allenpress.com/collection-forum/article-pdf/31/1-2/1/1506027/0831-4985-31_1_1.pdf by guest on 27 September 2021 g a a a a g a a + 23–37 0.1–0.5 Straight, awl-like Worn down Partial, on the proximal teeth Narrow 7.50 Indo-West Pacific g a a a a a a g Sawfish species 0.29–0.67 Straight, awl-like Absent Wide 3.25 Indo-West Pacific g e e e g 22–34Straight, awl-like VisibleAbsent Wide 3335 5.50 18–27 West and East Atlantic Worn down a,c,f a,c,d . a a g Pristis pristis Pristis pectinata Pristis clavata Pristis zijsron Anoxypristis cuspidata a a,e g c,d,f 0.5–1.0 6.75 East Pacific, Indo-West Pacific . . b . . . Properties Ratio of spacing between proximal and distal teeth. Wueringer et al. 2009 Whitty et al. 2013 Dulvy et al. 2016 Kirkland and Aguillon-Martinez 2002 Robillard and Seret 2006 Cicimurri 2007 a b c d e f g Table 1. Sawfish species and their properties. Common nameTeeth per sideIntertooth spacing ratio Tooth shapeTooth crownsLongitudinal grooves LargetoothRelative rostrum 16–24 widthInternal canals Full, to baseMaximum of length of teeth Straight, awl-like Absent sawfish (m) Wide Geographic distribution Smalltooth 3 West andConservation East Status Atlantic, Critically endangered Dwarf Endangered Green Endangered Endangered Narrow Endangered 4 COLLECTION FORUM Vol. 31(1) Downloaded from http://meridian.allenpress.com/collection-forum/article-pdf/31/1-2/1/1506027/0831-4985-31_1_1.pdf by guest on 27 September 2021

Figure 2. Standard measurements from Australian largetooth, dwarf, narrow, and green sawfish rostra. TRL: total rostrum length; SRL: standard rostrum length; SRW: standard rostrum width; TW: tip width; Rp: right proximal- most rostral tooth gap; Rd: right distal-most rostral tooth gap. (Whitty et al. 2013).

Fowler et al. 2005). Sawfish rostra are distinct cranial appendages with lateral protruding rostral teeth and are covered in placoid scales, also called dermal denticles (Shellis and Berkovitz 1980, Miyake et al. 1992, Hamlett 1999, Cicimurri 2007, Wueringer et al. 2012). The underlying cartilage structure has both mineralized and nonmineralized areas. The shape of the placoid scales is similar to those in sharks (Fig. 4). They feel smooth when stroked from distal end to base, but can be slightly rougher if stroked the other way. Nonoverlapping, plate-like crowns are secured with dentine roots embedded into the skin (Hamlett 1999). Unlike sharks, sawfish scales are relatively flat and do not have a central ridge. The rostral teeth are in fact modified placoid scalesHamlett ( 1999, Cicimurri 2007). Rostral teeth are contained in deep lateral sockets, or alveoli, and are not attached with

Figure 3. Largetooth sawfish (Pristis pristis) rostral teeth with no observed crowns and full posterior grooves, from Bristol Museum and Gallery (no catalogue number). (Photo: author). 2017 BYLER—IDENTIFICATION, STRUCTURE, CARE, AND 5 CONSERVATION OF SAWFISH ROSTRA Downloaded from http://meridian.allenpress.com/collection-forum/article-pdf/31/1-2/1/1506027/0831-4985-31_1_1.pdf by guest on 27 September 2021

Figure 4. Placoid scales on a largetooth sawfishPristis ( pristis) rostrum, from Bristol Museum and Gallery (un- catalogued), × 30 magnification. (Photo: author). connective tissue (Shellis and Berkovitz 1980, Kirkland and Aguillon-Martinez 2002, Wueringer et al. 2009)(Figs. 5, 6). This makes them relatively easy to remove. The teeth continue to grow during the sawfish’s lifetime. However, a lost tooth is not replaced, and the socket remains empty and eventually closes. Sawfish use the rostral teeth to attack and manipulate prey, which are consumed using rows of true teeth within its mouth located below the rostrum (Kirkland and Aguillon-Martinez 2002, Wueringer et al. 2012, Whitty et al. 2013 ). The rostral teeth and scales are composed of materials similar to true teeth, although they are weaker and more prone to degradation. Both teeth and scales are composed of

Figure 5. X-radiograph of a largetooth sawfish (Pristis pristis) rostrum from the broken end, inverted image, from Bristol Museum and Gallery (no catalogue number). The three internal canals, rostral teeth sockets, and growth bands on teeth are clearly visible. Thicker, mineralized cartilage appears darker than the unmineralized cartilage. A crack also appears on the lower left. Settings: 65 kV for 3 minutes. (Photo: author). 6 COLLECTION FORUM Vol. 31(1) Downloaded from http://meridian.allenpress.com/collection-forum/article-pdf/31/1-2/1/1506027/0831-4985-31_1_1.pdf by guest on 27 September 2021

Figure 6. Diagram of the internal structure of a largetooth sawfish (Pristis pristis) rostrum, from Bristol Museum and Gallery (no catalogue number). (Diagram: author). osteodentine (hydroxyapatite and organic material) and an enameloid sheath (hyperminer- alized enamel, hydroxyapatite, and calcium), with a collagen network and pulp canal that secures the tooth and scales to the substrate (Shellis and Berkovitz 1980, O’Connor 1987, Hamlett 1999, Whitty et al. 2013). The tooth dentine is arranged in tightly packed tubules parallel to the core (Figs. 7, 8)(Shellis and Berkovitz 1980, O’Connor 1987). This allows the tooth to fracture longitudinally but not transversely, which helps maintain the sharp- ness of rostral teeth and explains their irregular shape (Shellis and Berkovitz 1980). This is also why shrinkage from drying can result in longitudinal cracking and splitting (Fig. 9). The flat placoid scales do not have directional dentine tubules, but there is adefinite direction of growth, extending back over the epidermis towards the proximal end. Hydrox- yapatite is chemically stable, but can be demineralized in acidic conditions at or below pH 5 (O’Connor 1987). This external sheath can be quite thin or even absent and the enameloid easily wears down (Cicimurri 2007, Wueringer et al. 2009). Although more chemically sensitive than true teeth, mechanical damage resulting in the loss of scales and teeth is much more likely than chemical degradation during storage in museum collections.

Figure 7. Scanning electron microscope photograph of longitudinal surface of pulp canal (PC), nondirectional collagen network, and parallel dentine. (Photo: Shellis and Berkovitz 1980:343). 2017 BYLER—IDENTIFICATION, STRUCTURE, CARE, AND 7 CONSERVATION OF SAWFISH ROSTRA Downloaded from http://meridian.allenpress.com/collection-forum/article-pdf/31/1-2/1/1506027/0831-4985-31_1_1.pdf by guest on 27 September 2021

Figure 8. Transmission electron microscope photograph of transverse section of cylindrical dentine (C) sur- rounded by a darker collagen network. (Photo: Shellis and Berkovitz 1980:343).

Figure 9. Longitudinal cracking on largetooth sawfishPristis ( pristis) rostral tooth, × 5 magnification, from Bris- tol Museum and Gallery (no catalogue number). (Photo: author). 8 COLLECTION FORUM Vol. 31(1) Downloaded from http://meridian.allenpress.com/collection-forum/article-pdf/31/1-2/1/1506027/0831-4985-31_1_1.pdf by guest on 27 September 2021

Figure 10. Diagram of a rostral cartilage cross section, demonstrating the three layers of mineralized cartilage surrounding the internal canals. (Adapted from Cicimurri 2007)

Internal canals run from the proximal base to the distal end of the rostrum and contain blood vessels, nerves, fluids, and connective tissues during the sawfish’sHoenig life( and Walsh 1982, Cicimurri 2007, Wueringer et al. 2009). Hollow at the base, the distal third of the canals are filled with unmineralized hyaline cartilageWueringer ( et al. 2009). Two layers of calcified cartilage surround each of the lateral canals, and a third outer layer surrounds the entire structure (Hoenig and Walsh 1982, Cicimurri 2007)(Fig. 10). Calcification of the cartilage, which makes up the canal walls, creates a strong and rigid appendage. The rostrum’s mechanical and chemical properties are similar to mammalian bone and teeth, although more flexible and porous (Wintner 2000, Porter et al. 2006, Cicimurri 2007, Kittiphattanabawon et al. 2010). The epidermis and scales make the sawfish skin tougher and more resistant to chemical attacks than mammalian skin (Bailey 1971, Kittiphattan- abawon et al. 2010). Sawfish cartilage is composed of collagen fibrils, an amorphous ground substance, proteins, chondrocytes, and water (O’Connor 1987, Kennaugh 1988, McDon- ald 2006). The cartilage structure contains both mineralized and nonmineralized layers (Hoenig and Walsh 1982, Wintner 2000, Porter et al. 2006, Cicimurri 2007, Claeson 2011). It is the calcified outer layers, which incorporate calcium phosphate hydroxyapatite intothe matrix, that give the sawfish cartilage properties close to that of bone(McDonald 2006, Porter et al. 2006). Although relatively mechanically strong, cartilage is prone to damage through shock (McCredie et al. 2009). Water is absorbed into the porous cartilage matrix during the sawfish’s life, constituting much of its volume (Kennaugh 1988, Kittiphattan- abawon 2010). When dried, this can result in shrinkage and weakening of the remaining matrix. The chemical stability of collagen is dependent on the hydrogen bonds in its helical structure (Bailey 1971, O’Connor 1987, Stuart 2007, Kittiphattanabawon et al. 2010). The collagen fibrils are chains of amino acids with both polar and nonpolar side groups, making them susceptible to degradation due to acids and alkalis, and disruption by water (Table 2) (Bailey 1971, O’Connor 1987, Wess and Orgel 2000, Storch 2003, Stuart 2007, Kittiphat- tanabawon et al. 2010). As a result, collagen is prone to hydrolysis, oxidation, discoloration, staining, and biodeterioration.

RISKS FROM HANDLING Specimen handling causes more damage to museum objects than any other hazard. Spe- cial and high-value objects are typically safeguarded (Price and Fitzgerald 1996, Carter and Walker 1999). A decision must be made whether the benefits of having the specimen as part of the research collection outweighs the benefits of allowing visitors or students to handle the rostrum with the concurrent risks of damaging the object. 2017 BYLER—IDENTIFICATION, STRUCTURE, CARE, AND 9 CONSERVATION OF SAWFISH ROSTRA

Table 2. Significant causes of chemical degradation of a sawfish rostrum.

Type of damage Affected area Resulting damage

Watera,b,c,d Cartilage, scales, teeth Absence: Shrinkage, cracking, loss of strength, cross-linking of amino acids, oxidation Presence: Swelling, deformation, disruption of cross-linking of amino acids, oxidation Acidsc,e,f Cartilage, teeth Breakdown of collagen, loss of cohesion, collapse of structure

Alkalisa,c,e Cartilage, teeth Breakdown of proteins, collapse of structure Downloaded from http://meridian.allenpress.com/collection-forum/article-pdf/31/1-2/1/1506027/0831-4985-31_1_1.pdf by guest on 27 September 2021 Heat (> 32◦C)c,f Cartilage Breakdown of proteins, deformation, embrittlement Lightf Cartilage Breakdown of collagen, loss of strength, oxidation, embrittlement

a Bailey 1971. b Kennaugh 1988. c Kittiphattanabawon et al. 2010. d Wess and Orgel 2000. e O’Connor 1987. f McDonald 2006.

If visitors are allowed to touch the rostrum it is likely that some damage will occur, sub- sequently requiring cleaning and repairs (Moore 2004, Pye 2008). Staff can direct how the specimen is to be handled to prevent some damage (Pye 2008). However, because sawfish are increasingly rare, it might be more desirable to protect the rostrum in the research collection than to allow tactile access as an educational object. If there is a risk that the rostrum might be contaminated by pesticides, handling should only be undertaken with appropriate personal protective equipment (Museums and Galleries Commission 1992, Hendry 1999, Pye 2008, Conservation and Collections Care 2013, Hawks et al. 2014). The following risk matrix shows some of the hazards that can occur during the use of a rostrum (Table 3). Most of the hazards are low to moderate, such as dust, molds, viruses, and bacteria. These are generally acceptable for an object in a handling collection.

Table 3. Risk matrix for allowing visitors to touch or handle the rostrum. The risk level has been calculated as severity × intensity. The lighter shades are lower risk, and darker shades indicate a higher risk level. 10 COLLECTION FORUM Vol. 31(1)

Table 4. Environmental risks to the rostrum and suggested conditions.

Risk type Risk Preferred condition

Relative Distortions and shrinkage Constant, without fluctuations humiditya,b,c,d,e Embrittlement and stiffness Maintain equilibrium moisture content with the ambient environment Cracking and splitting > 40% RH and < 55% RH preferred Chemical degradation

Bacteria, fungi, or mold growth Downloaded from http://meridian.allenpress.com/collection-forum/article-pdf/31/1-2/1/1506027/0831-4985-31_1_1.pdf by guest on 27 September 2021 Temperaturea,c,e Distortions and shrinkage Constant, without fluctuations Embrittlement and stiffness 15–25◦C preferred Cracking Chemical degradation Handlinga,b,f Physical damage Check for physical damage Visual impact Clean fortnightly if to be handled Bacterial growth Monitor visitors handling the object Staff direct handling only If not to be handled by visitors, train staff how to properly carry the rostrum Lighta,b,e,f Fading, bleaching, and discoloration Up to 200 lux Change in texture Minimize or eliminate UV light Chemical degradation Dusta,b,c Visual impact Keep in display case when exhibited Hold moisture on surface Place in a box or cover with Tyvek or plastic sheeting when in storage Physical damage Clean with a stiff brush Pestsb,f,g Weakening or breakdown of structure Monitor for pests and pest damage Organic material eaten Segregate from other collections Visual impact Keep in sealed but not airtight display case Transportb,c,d,e Physical damage Pack in a strong, rigid box with Plastazote cut outs and acid-free tissue Trained staff should handle and mount the rostrum

a Carter and Walker 1999. b Conservation and Collections Care 2013. c Hendry 1999. d Horie 1988. e Museums and Galleries Commission 1992. f Cross 1988. g Hawks et al. 2014.

Grime, dust, bacteria, molds, and pests can all be reduced with regular cleaning. Deliber- ate or severe damage, such as vandalism, theft, dropping from a significant height, and loss or breakage of material, can be minimized with supervision. Physical damage, including abrasion and loss of scales or teeth, can be mitigated by coating the rostrum. A dilute acrylic resin or poly(vinyl acetate), such as 10% Paraloid B-72, can secure the surface. However, this could negatively affect the appearance of the rostrum, and the ethics of such an alter- ation must be considered. If the specimen’s research value outweighs the educational value, the potential for loss of the specimen would preclude handling and coating.

SURFACE CLEANING To clean a dusty rostrum, a stiff brush should be used, such as hog’s hair, possibly with the aid of a vacuum (Storch 2003, Elliott et al. 2007, Daudin-Schotte et al. 2010). The 2017 BYLER—IDENTIFICATION, STRUCTURE, CARE, AND 11 CONSERVATION OF SAWFISH ROSTRA rostrum should be brushed from the distal end to the proximal end in order to avoid catch- ing or lifting the placoid scales. Other dry-surface cleaning materials, such as Groomstick or cosmetic sponges, can be used if the rostrum is in good condition. Laser cleaning is relatively novel but could produce successful results. Solvents and poultices might be considered if the grime is embedded. Because the structure is sensitive to water, aqueous cleaning methods cannot be recommended unless the rostrum is stable and the wetting is minimal. Care should be taken not to damage the surface if the enamel has worn off the scales or teeth, or if scales are missing. Downloaded from http://meridian.allenpress.com/collection-forum/article-pdf/31/1-2/1/1506027/0831-4985-31_1_1.pdf by guest on 27 September 2021

CARE OF SAW F I S H ROSTRA Rostra should be handled with clean hands or nitrile gloves, not cotton gloves because the cotton fibres can snag on the placoid scales. The rostrum should be lifted by thecarti- laginous central section only. Lifting or holding the rostrum by the rostral teeth can easily pull them out of their sockets. Loose scales and damaged rostral teeth can be secured with an acrylic resin or poly(vinyl acetate) or butyral, such as Paraloid B-72 or Butvar. Broken or frayed rostral teeth can be repaired or consolidated as well. In storage, rostra should be laid flat and fully supported in a box and fixed in placewith Plastazote and acid-free tissue to avoid movement (Horie 1988, Museums and Galleries Commission 1992, Hendry 1999, McDonald 2006, Conservation and Collections Care 2013). They should not be wrapped in material such as bubble wrap or fibrous material such as batting becaue this readily catches on the rostral teeth and can pull them out. Excessive abrasion can also damage or detach the placoid scales. The rostrum should be checked each time it is removed from the box for signs of degradation. Because sawfish rostra are humidity sensitive, the environment in the storage room ordis- play case should be monitored and controlled. Like many organics, sawfish rostra should be kept between 40 and 55% relative humidity if possible, though consistency is more important. Fish cartilage tends to be fragile and prone to degradation in unstable environments (Cross 1988, Museums and Galleries Commission 1992, Carter and Walker 1999, Hendry 1999, Storch 2003, McDonald 2006). Moderate humidity, moderate to low temperatures, and low light levels are essential to prevent chemical degradation (Table 4). At high humidity or temperature, the collagen structure is more flexible and prone to distortions and biological attack (Museums and Galleries Commission 1992, Carter and Walker 1999). At low humidity or temperature, the structure can become brittle and shrink, and can crack and split. Fluctuations of relative humidity and temperature are particularly physically damaging, and the stability of the environment is more important than the exact levels (Museums and Galleries Commission 1992, Carter and Walker 1999, McDonald 2006). Dust, pests, transport, and handling can all cause physical damage to the rostrum (Cross 1988, Museums and Galleries Commission 1992, Carter and Walker 1999, Hendry 1999, Storch 2003, Conservation and Collections Care 2013, Hawks et al. 2014). Pollutants are less of a concern for natural history specimens, but is still an aspect to be considered (Cross 1988, Conservation and Collections Care 2013). These hazards can be lessened with mon- itoring, environmental controls, proper packaging, and display cases. Sealed metal display cases and properly padded storage containers that support the entire length of the rostrum are recommended. When mounting a rostrum for display, the support should be sturdy and discreet. A ver- tical orientation would have the most visual impact, though a horizontal orientation allows the visitor to better conceptualise the species. The stiff, mineralized cartilage of the canals can be used to support the rostrum and evenly distribute the stress (Horie 1988, Lowry 12 COLLECTION FORUM Vol. 31(1)

2012). The canals are filled with cartilage from between a third and half way from the distal end (Wueringer et al. 2009). An X-radiograph can show the exact endpoint. Weight should never be placed on the rostral teeth. Stainless steel, Perspex, or carbon fibre rods can be used to attach the rostrum to a base. Wires hooked through the canals or piercing the distal end can be used to attach the rostrum to a wall or backboard. Many museum and collector’s rostra are mounted vertically with rods or wires entering the lateral canals (Robillard and Seret 2006). Downloaded from http://meridian.allenpress.com/collection-forum/article-pdf/31/1-2/1/1506027/0831-4985-31_1_1.pdf by guest on 27 September 2021 CONCLUSIONS The care of sawfish rostra in museum collections has not been widely documented or studied. Conservation recommendations of sawfish rostra should address the special needs for the cartilaginous structure, the placoid scales, and the unique rostral teeth. An understanding of the chemistry and structure of the various parts of a rostrum is necessary be- fore an appropriate care strategy can be developed. Due to inherent weaknesses within rostra, they are particularly susceptible to physical damage in private and museum collections during both storage and conservation treatments. Loss of scales and rostral teeth are significant risks. Understanding the weaknesses of rostrum structure allows us toavoidor monitor damage better. The stronger cartilage around the central canals can be used to handle and support the rostrum, and storage or support materials that might negatively affect the scales and rostral teeth should be avoided. The identification of sawfish rostra and their use in museum collections is informed by conservationists and biologists. Many ethnographic and natural history collections contain rostra, but many sawfish are now critically endangered. Some protected sawfish species are still being killed and their populations are shrinking. This could increase the requests for use of sawfish rostra in collections for scientific study. An understanding of how to care for rostra in museum collections enables the continued preservation of these fascinating objects for display and scientific study.

ACKNOWLEDGMENTS

I would like to thank the Bristol Museum and Gallery for the use of their sawfish rostrum. I also thank Jane Henderson of Cardiff University for her support and encouragement, as well as Christian Baars of the National Museum of Wales for helpful comments on the manuscript.

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