Crustaceans preservation
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The document discusses methods for collecting and preserving various types of crustaceans. It describes different nets, traps, and techniques used to collect crabs, lobsters, prawns, and cladocerans. The key preservation methods include fixation in formalin, storage in 70-75% ethyl alcohol, and adding glycerol or propylene glycol to prevent desiccation. Regulations for crab traps and nets are also outlined.
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Crustaceans preservation
- 2. COLLECTION AND PRESERVATION OF CRUSTACEANS PRESENTED BY VISHNURAJ.R.S
- 3. INTRODUCTION Crustaceans form a large group of arthropods usually treated as a subphylum It include Crabs, Lobsters, Cray fish, Shrimps, Krill, and Barnacles The study of that because more than 10million crustacean produced annually for human consumption. They have many ecological and phylogenetic significance also. The study of crustaceans mainly through specimen analysis. The collection and preservation of specimen through various techniques The collection mainly through hand picking or using nets The specimens are well documented and preserved for future uses.
- 4. COLLECTION METHODS CRAB 1. HAND PICKING This is one of the common technique use to collect crustaceans. Gloves are permitted for this. 2. SPANNER CRAB NET It is a net attached to a rigid rectangular frame not exceeding 1.6 meters in length and 1 meter in width net capable of extending more than 0.1 meter beneath the frame is suspended in a horizontal position. There are many regulations for the use of spanner crab net .
- 5. BOX CRAB TRAP •It is made from strong non collapsible wire. •It’s advantage is ones crab enters searching for bait, it can’t escape. •The down side of this trap is storing and transporting it since it collapse. •PYRAMID CRAB TRAP These are flat when lying on the bottom of sea floor, but when raised to the surface they form the shape of pyramid. This is similar to ring crab trap because ,no wall or prevents to resist the escape of crab from trap.
- 6. Benefit from ring trap is that, it is slightly sturdier and so used in waters with strong currents. RING CRAB TRAP •These are very popular •Primarily used in river mouths and protected bays, but it is also use in open shoreline. •It is a sample piece of equipment that contains two wire rings that form the top and bottom of a collapsible basket. •The lower ring is smaller than the upper ring and connected by a strong netting that forms the side.
- 7. REGULATIONS FOR USING CRAB TRAP AND CRAB NET • Not more than 1 trap or net to be used (or in possession) by any person at any one time. • Maximum dimensions - 1.2 meters (length) x 1 meter (width) x 0.5 meter (depth) or has a diameter not exceeding 1.6 meters at the top or bottom for crab traps. • The float/ buoy must measure not less than 100mm in all dimensions, which show the details about, type of net , name and address of the crabber.
- 8. THE MARYLAND CRAB POT • It is a cubic structure ,generally 2 cubic feet and weight of 15 pounds after baited • It is an enclosed framework of wire with four opening. • These openings are constructed four entering the crab to the trap •The crab doesn’t leave back on the same way they entering. •Crabs swim upward and go through the opening of the inner portion ,crabs become permanently trapped.. •A floating buoy attached to the crab pot to locate the position
- 9. PRESERVATION TECHNIQUES OF CRABS Crabs can be preserved wet in 6-10% formalin neutralized with Hexamine i.e., 100 gm per 1000ml formalin. To avoid limb-shedding the unique phenomena of autotomy alive crabs may be narcotized first with few menthol crystals or by adding few drops of chloroform. Then preserved in spirit or formalinated spirit for a day or two, to make the autotomizing muscles as well their "breaking-planes' rigid After fixing,crabs can be preserved in 6-10% formalin for the laboratory studies. The colour retension in crabs is now experimented with 5% aqueous Solution of sodium arsenite to preserve red and related colours
- 11. COLLECTION OF PRAWNS HAND HAULD NET •Maximum length of 6 meters. •Mesh size between 30mm-36mm measured across the diagonal. •Must not be staked or set, or joined or placed with any other net. •Must be continuously and manually pulled through the water and not used as a stationary net. •Hauling lines of up to a maximum of 2 metres in length may be used.
- 12. SCOOP NET • It is a seasonal gear, particularly used on high salinity and high turbidity conditions • Made up with conical nylon monofilament bag • Maximum diameter of hoop or ring 0.6 meters. • Minimum mesh size 20mm measured across the diagonal. • It is used for fishing in areas with seagrass meadows ,particularly in the outer channel areas. • Scoop net with small handle is normally used to collect crabs from hand line and
- 13. STAKE NET •It is cotton net variable in size 12mto 30 m long with mesh size of 1or 2 cm. •Commonly used at time of tide , •SINGLE HOOK HANDLINE •It is commonly used in outer channel sectors of lakes •It is a single nylon filament with a hook attached on the end.
- 14. CRUSTACEANS PRESERVATION Different methods are used for preservation of crustaceans.The preservation include different steps FIXATION A fixative actually "fixes" a specimen by stabilizing (cross-linking) the proteins within its tissues such that long afterwards, the tissues will still retain a semblance of their appearance in life. The most common fixative for crustaceans historically has been formalin. "), this is a 37%-40% aqueous solution of the gas formaldehyde. To overcome the brittleness of specimen add softening agents like propylene phenoxytol , glycerol. The DNA denaturation property of formalin ,we use 95% ethyl alcohol.
- 15. PRESERVATIVES A preservative, in contrast to a fixative, is a solution in which the specimen can be stored and maintained without further degradation. far the most common preservative in regard to storage of crustaceans is ethyl alcohol, usually in a concentration of 70 to 75%. As with the fixatives, occasionally propylene glycol or glycerol are added in small amounts to maintain flexibility of the appendages and to slow down the desiccation of the specimen,
- 16. RELAXATION OF SPECIMEN Crustaceans, like some other arthropods, can throw off (autotomize) a limb when alarmed, and this behavior is often seen when the animal is exposed to a fixative or preservative. "Relaxing" the specimen by adding some kind of narcotizing agent (e.g. clove oil, magnesium chlorate, chloral hydrate, Epsom salts, CO2 gas, menthol, or other chemicals, ) to the water in which it is being held prior to fixation is helpful for avoiding autotomy. . Limb autotomy also can be avoided by chilling the live specimen (immersing it in ice water for a few hours) and then transferring it to the desired fixative or preservative.
- 17. COLLECTION OF CLADOCERANS Cladocerans are small crustacean ,zooplanktons like daphnia, larval nauplius etc..are coming under this It is easy to collect cladocerans in small habitats where a boat is not necessary. A small dip net on a long handle (at least 2 m long, telescopic), or a throwing net with a line about 10 m long, both of them of 0.1 mm mesh size and with a mouth diameter of 15 to 20 cm, It is important to collect enough material, always a large population has to be examined in order to get reliable results.
- 18. There are two routine ways to preserve zooplankton for further identification and treatment. Either 40 % formaldehyde solution is added to the total volume of the sample to get a final dilution of about 4 % formaldehyde, or the zooplankton is filtered out and transferred to 70 % ethyl alcohol (ethanol).
- 19. It is preferable to transfer material preserved in formalin to 70% alcohol since long storage in the former preservative makes the specimens brittle. . The addition of 10% by volume of glycerol or propylene glycol to each ethanol sample is a good precaution against drying. Permanent mounts At first specimens picked out from the sample should be transferred to a small volume of 70 % alcohol to which several drops of lignin pink and chlorazol black E have been added. After staining cladoceran specimens should be transferred either to a mixture of ethanol and glycerol (3:1), and then possibly dissected and mounted in any water miscible medium, or whole specimens, Canada balsam, as a traditional medium, or synthetic resins are recommended.
- 20. The crabs, lobsters, cladocerans, shrimps.etc are coming under the group of crustaceans. They are collected by using many techniques Crabs collected by hand picking, using crab net ,crab traps etc. Lobsters are collected by lobster trap. Prawns are collected through hand hauled net, scoop net, stake net and also by hook hand line. The collected specimens are fixed by using formalin, and preserved in 70-75% ethyl alcohol. Some crabs and lobsters are preserved by dry preservation.