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Tuatara: Volume 3, Issue 3, November 1950

Collecting and Preserving Zoological Specimens

page 104

Collecting and Preserving Zoological Specimens

Collecting, to a zoologist, is only a means to an end. His real work starts when the collection is fully documented, and is complete enough to enable him to recognise the animals of a region. A student interested in species as such may follow up the taxonomy of a group, leading to a study of its evolution, and the relationships of its members. Or his main interest may lie in the adaptations of the animals to their environment, leading to a study of the biology of one species, and later to that of a group of animals-ecology or animal sociology. From either point of view, the forming of a collection will serve as a tool to discover and a tack further problems. And to the New Zealand zoologist, problems will soon present themselves.

The following notes are designed for the student beginning serious collecting. They outline the steps to be taken from the time of locating and securing the specimen, through the stages of fixing, preservation and recording.

Marine Invertebrata *

Collecting Methods

Organisation of field work is best left to the collector. Most marine work will be done between tide marks and full advantage should be taken of the predictions and times of lowest tides in the Nautical Almanac. On rocky coasts especially, the area should be reached an hour or two before low tide. The upper portions of the reef can then be thoroughly combed, and will not be neglected in favour of the richer substratum. A general recennaisance of the ground may be made before collecting; if the locality is a new one, a simple sketch plan together with a photograph often helps. Rapid sketches and measurements should be made of zonation patterns of sessile plants and animals.

In summer, or on North Island coasts, shorts or swimming trunks are the most serviceable dress for moving about in at low tide mark. Strong, open sandals are the best footwear, allowing the water to run out, but protecting the feet. During winter, rubber knee-boots are useful and comfortable. They should never be worn, however, on mudflat or soft sandy bottoms, where they render the wearer helpless if he gets bogged. A strong-bladed pocket knife should be carried, together page 105 with a hand-lens and collector's note-book, secured to his person, although in strong winds, or spray, or standing waist-deep in water, the student is often unable to use his notebook. Metal or enamel “billies” are ideal for bringing home material, with individual tubes or jars in which to keep animals separate. Most marine animals remain alive much longer in air, or wrapped in moist seaweed, than in seawater which is allowed to become foul. Portions of the substratum, hold-fasts, and algal thalli should be brought home for careful dissection in search of smaller animals, if possible under the binocular microscope. In sand or mud-flat collecting, the chief requirements are a spade and a coarse-meshed sieve, and the zoologist must be prepared to dig deeply and energetically.

Preservatives and Fixatives

Formalin, where its use will not harm the specimen, is a better preservative than alcohol. It penetrates more rapidly and internal organs remain in better condition. Commercial formalin (40%) should be diluted with ten volumes of water to a 4% solution. 2% formalin with seawater is an excellent quick preservative for small specimens.

Alcohol as used in zoology is generally 95% ethyl alcohol (white spirits) which may be diluted with distilled water to strengths of 70% and 80%. At least 70% is required for safe storage of material. Alcohol is a valuable preservative for crustacea, polychaeta and echinoderms with corrodable bristles or hard-parts. A teaspoonful of glycerine in a quart of alcohol helps to preserve natural colours and to keep integuments flexible. Alcohol in jars containing preserved specimens should be changed at intervals—once or twice a year—and evaporation should be guarded against. One of the most important fixatives for the general collector of invertebrates is Bouin's Fluid, which is excellent for general structural and histological work, and for preservation of animals for dissection. Fixation time is at least 12 hours for a specimen of lcc. bulk, correspondingly longer for larger material. There is not much danger of over-fixing. Afterwards specimens should be washed in 70% alcohol, to remove excess picric acid, and stored in 70-80% alcohol. Formula for Bouin's: 75 parts saturated aqueous picric acid; 25 parts 40% formalin; 5 parts glacial acetic acid.

Field Record Sheets (Diag. p. 106):

The illustration shows a suitable type of field record. Several hundred of these should be cyclostyled on quarto sheets at the beginning of a collecting season. The paper should take ink, and it may be perforated along the margin for filing. During field work, the collector will use his note-book for “on the spot” observations. On returning home, he should—even at some inconvenience—sort over and roughly classify the specimens, discarding unwanted material at once. Sketches and colour records must now be completed while the animals are still alive. The field sheets should then be filled in, before exact details page 106 Example of a field record sheet. page 107 are forgotten. The amount to be recorded will vary greatly from group to group, according to the amount known, or to the collector's interest in the material. The sheets provide for ample detail, but it is tedious to repeat exhaustive information on each sheet. If too much detail is aimed at, the collector, after a day in the field, will probably not write up his sheets at all. Each bottle or tube of specimens should be identified by a reference number corresponding to the serial sheet number. Specimens are thus numbered simply in order of collecting and writing up. An abbreviation for the name of the class can be usefully added to the sheet below the serial number, e.g. (CTEN — GASTR — CRUST —). The sheets may then be filed in serial order, and, if necessary, as the collection grows, cross-indexed in taxonomic and ecological categories. Details of locality, type of environment, ecological association should be specified, with date and collector's name. Space is left for details of novelty or special interest, but with well-investigated species, this will not necessarily be filled. Reference should be given to any life drawing, colour record, slide or other preparation made from living material. After identification the specific name can be added in the space provided, together with a note referring to taxonomic or general literature. A brief summary of diagnostic features can often be added with advantage.

Storage of the Collection

As the collection grows, the greatest need will be for an orderly storage system, with facilities for quick reference to any container, to filed field notes and any other information. It may be desired to have the collection visible for permanent display, and with mollusc shells or dried material a set of flat cabinet drawers is best for storage. Most invertebrates, however, will be kept in bottles, and sets of tubes or jars can be massed together in a small space by placing them in deep cardboard boxes, conspicuously labelled with serial box numbers, and either the ecological to taxonomic classification of the material contained, e.g., either Low TideWharf PilesDevonport, or Echinodermata (Ophiuroidea and Holothuroidea). At the same time, the field record sheets should be kept in readily accessible files, again either in ecological or taxonomic order.


A tidy-minded collector will probably prefer several uniform sizes of tubes and jars. These pack more economically into limited space and are fairly cheap in quantity. Jars should be wide-mouthed, and of clear glass, thick enough to withstand knocks. Bakelite or other noncorrodable tops are preferable to metal caps. Alternatively, widemouthed bottles may be stoppered with firm, good quality corks.

Preserving jars with rubber washer lids are ideal for larger specimens, while for the bulkiest material, metal drums of two or four page 108 gallons capacity are useful. For normal use, jars of 6in. × 3in. and 4in. × 2in. are most serviceable. Specimen tubes are most useful in the 4in. × lin. size. For larger polychaetes, 6in. × 1in. tubes are available, while the smallest material, such as minute shells and crustacea, can be put into 2in. × ½in. or 2in. × ¾in. phials. Small lengths of glass tubing, cut with a file and sealed by heat, or with cotton plugs are often used for tiny shells, and small rubber-stoppered serum tubes are especially useful for delicate material. Specimens as a rule may be put straight into the container, although soft-bodied nudibranchs and coelenterates should be protected from distortion by placing them on a layer of cotton wool.


The bulk of the information about a specimen should be entered on the record sheet. It is not usually convenient to label material exhaustively in situ. Labels attached to the container should include the habitat, locality and date, and the collector's initial, with perhaps a condensation of any other information to which it is desired to refer without turning up the field sheet. Most important, there should be a reference number to the written field record. Alternatively specimen labels can be placed in the preservative within the container. They should then be written on stiffish, non-absorbent white card, either in pencil (not “indelible” pencil) or in indian ink. Ink labels should be allowed to dry, then steeped for a few minutes in a 3% solution of acetic acid, which effectively sets the ink and prevents “running” when placed in preservative. An example of a completed label is shown. Note that the accurate identification of the specimen is not important at this stage. Often it may not be possible immediately; and the name will have to be entered on the field sheet at a later date. Sometimes identification by a specialist will be needed, while in a few cases the collector may have the thrill of bringing home a yet undescribed species.

  • Low Tidal Sand-Flat (L.W.S.T.)

  • Cheltenham Beach 5.11.49. W.J.B.

  • Commensal in burrows of Trochodota

  • 105 (LAM) (Scintillona zelandica)

Notes on the Treatment of Special Groups

1. Coelenterates are difficult to preserve adequately. The pelagic Scyphozoa, Siphonophora and Ctenophora are often singularly beautiful in form and colour. The collector must be prepared for work in the field, with note-book and colour sketches. Afterwards the best that can be done is preservation in 70% alcohol or 5% formalin—usually a poor best! Smaller hydrozoans such as Obelia and Sertularia are easier to deal with, while the less well protected Hydra can be quickly fixed in Bouin's—warm, not hot. Among the sea-anemones, important taxonomic features are the handsome page 109 colour patterns, arrangement of tentacles, and of mesenteries, and microscopic structure of nematocysts. The first two features should be observed in the expanded living animal; the last two require careful fixation, after narcotisation, during which the epithelia should not be allowed to deteriorate.

2. In the Platyhelminthes (Flatworms) and Nemertea (Proboscis worms) final identification often depends upon microscopic examination of sections. Careful fixing is essential for critical study of internal structures. On collecting alive, a colour record and accurate measurements should always be made, with a scale drawing recording accurately any periodic changes of form. In planarians and nemerteans lens details of eye arrangement are important. The best fixation is by pipetting warm Bouin's Fluid over the animal, from tail forward, so as to cause a minimum of contraction. Storage for several days in Bouin's will not harm the tissues. 70-80% alcohol is useful for temporary storage, also as an alternative fixative. Animals may be dehydrated, cleared and bulk-stained for internal study of whole mounts. For the systematist's purposes, it is a good plan to bring a few specimens up to paraffin fairly rapidly, orient and embed in blocks. Paraffin is, perhaps, the best long-term preserving and storage medium of all.

3. Polychaeta or larger bristle worms present fewer problems. Their colours are often brilliant and characteristic, and should be recorded in life. Formalin—unless rendered neutral in reaction—damages the setae, on which systematic work so much depends. Use, therefore, 70% alcohol, bringing up to 80% with a drop of glycerine to prevent shrinkage and undue fading. Worm tubes — calcareous, parchment or sandy, should be kept. Habit sketches should not be neglected, especially with worms having a specialised relation to the substratum. Feeding, respiratory and cleansing mechanisms can be properly studied only with living material, and the field biologist will get useful “hunches” from watching the behaviour of his specimen before collecting, and observing the action of tentacles, mucous glands, parapodia and ciliary fields while the worm is still alive.

4. In the Echinodermata identifications are based to a major extent on skeletal parts. Formalin should therefore be avoided in favour of 70-80% alcohol, with glycerine to keep soft articular membranes flexible. Much more difficult to handle than the starfish or urchins are the delicate Ophiuroids or brittle stars, which break into fragments at slight provocation. They should be placed in clean seawater in flat dishes, and carefully narcotised as with nudibranchs.

The Holothurians or sea-cucumbers are equally temperamental—eviscerating themselves when irritated. Before preservation the animals should be narcotised by the addition of magnesium sulphate or menthol to the sea water in which they are contained. When completely page 110 insensitive to stimuli such as pricking they should be transferred to 70% alcohol for preservation and storage. Formalin should not be used as it is liable to dissolve the body wall spicules, which are very important diagnostic characters. With all living echinoderms, look for commensal molluscs or crustaceans.

5. Ascidians and Enteropneusta. The tunic of simple ascidians should be slit to allow penetration of formalin when the specimen is detached from the substratum. Colour notes, both of test and contained animal, are of great importance. Shrinkage invariably takes place, so that accurate measurements must be taken in life. Compound ascidians, after the all-important colour note, should be fixed directly, some left in the test, others pressed out on slides. Glacial acetic acid is recommended, with transfer after 5 minutes to 95% alcohol. In the Enteropneusta, the bright, distinctive colours are of systematic importance as also the structure of the epithelial regions. Overall measurements should be made of the successive regions of the extended animal, followed by narcotisation with the gradual addition of alcohol. Before narcotisation any odoriferous properties should be noted—many enteropneusts produce iodoform, while to one species is attributed the odour of “chloride of lime with a faecal admixture!” As with the lower worms, successive portions of the body may with advantage be dehydrated, cleared and embedded.

6. Crustacea. With large crayfish, anomurans and crabs, as well as barnacles, material may be dried, but fluid preservation is better, using 70-80% alcohol with glycerine, not formalin. Good preservation should keep setae intact and joint membranes flexible. Penetration of alcohol to viscera is poor, and where specimens are wanted for dissection, it may be necessary to use form-alcohol, even with detriment to the exoskeleton. Crustaceans are especially interesting in the modifications of mouthparts and other appendages, which should be observed in action in living material. Notes should be made of the dates at which specimens are in berry, and in the case of parasites, host relationships should be recorded. In the Cirripedia the systematist requires preparation of mouthparts and cirri—animals should always be preserved. The smaller Branchiopoda, Ostracoda, and Copepoda, as well as ISOPODS and Amphipods, should be placed in small tubes with 70% alcohol. They can be collected by tow-netting and by steeping algal thalli and holdfasts in 1% formalin in flat white dishes in whch the dislodged animals (including caprellids and pycnogonids) can be easily located.

7. Most of the Mollusca are very easily preserved, and while perfect cabinet specimens are not necessary for the general zoologist, shells may be carefully scrubbed with a fine nail-brush to remove encrusting growths. Chitons should be firmly bound to wooden splints page 111 or slides to ensure their drying flat. With gastropods, boiling will not usually hurt the shell, and the animal can then be extracted by means of a skewer or a pin. Opercula should always be kept, while in addition, it is very desirable to have radulae, whether isolated by boiling in potash, or left intact in the head or proboscis which may be cut off and preserved separately. Bivalves should be allowed to gape naturally before removing the animal, since there is a risk of damaging the delicate hinge line on forcibly opening shells. The colours of bivalves are especially beautiful in the Pectinidae and the Gariidae, which should be carefully kept away from light. Molluscan animals should be kept where possible: they are at least as important as the shells.

Bouin's fixative is recommended, and it is often advisable to sacrifice one or more shells, lest the animal be damaged by extraction. Small gastropods should be gently cracked and dropped into Bouin's intact. The shell is perfectly dissolved, and the fixed animal remains, with chitinous operculum and radula intact. Bivalves should be wedged open slightly to allow entry of fixative. Colour notes and habit sketches of the extended animal should not be forgotten. In bivalves, note the size and shape of foot and siphons, in gastropods, locomotor, feeding and protective mechanisms, as well as details of spawning and copulation.

The soft-bodied Opisthobranchs are of unrivalled interest in their colours, and in diversity of structure and habits. They are, however, the most troublesome of invertebrates to preserve. Colour sketches and records of external form in life are indispensable. Narcotisation is difficult: a few methods may be suggested, but to a large extent the collector must be guided by his own mistakes. Slow, gradual tincturing of seawater with formalin, alcohol or coccaine is often successful. Alternatively, crystals of menthol, naphthalene or magnesium sulphate may be sprinkled upon the top of the water. For the study of internal structure it is best to pin freshly collected living material in extended condition, flood with Bouin's fluid and incise the dorsal integuments. Internal structure will otherwise probably deteriorate while the half-narcotised animal is still responsive to stimuli.


Most zoologists will have a working familiarity with one or more groups, and in many cases the collector himself will have specialist knowledge of his material. A field zoologist can usefully aspire to an acquaintance with a whole fauna as far as the family or generic level. In practice, however, there will always remain a large number of animals which must be sent to a specialist, usually a professional zoologist, for identification. Sponges, amphipods, polychaetes, and planktonic crustacea are likely to remain specialist's groups. Taxonomists are busy people. This should be remembered in sending specimens, which should be carefully sorted, separated as far as possible into distinct forms, securely packed and sufficiently stamped. Good specimens page 112 only should be sent; mutilated fragments, except with rare species, are troublesome and of little interest. The specialist will often be interested in the collector's field observations; where necessary, send record sheets and colour notes. Taxonomists are human, and will often covet specimens of rarer material sent in. Show your appreciation by supplying duplicates. And remember that a single rare specimen is of much more use to a specialist in the group than to the omnivorous general zoologist. If the taxonomist wants to keep it, let him do so. His future help will be the more available.

Zoological collecting does not entail “sitting on” rare material to the envy of less fortunate competitors. Unused specimens are of little value lying on shelves. If you know of a man interested in—for example—barnacles, nudibranchs or crabs, let him have your material to work it up, even if he is not at once able to give quid pro quo.

Works of Reference—Taxonomic Authorities

Systematic coverage of New Zealand marine and freshwater invertebrates is very uneven. The following list of references is not exhaustive, but introduces the principal authorities and indicates the gaps still to be filled.

Chilton, C.The Subantarctic Islands of New Zealand. A twovolume work giving a fairly complete over-all coverage of the fauna and flora of the Subantarctic Islands.

Powell, A. W. B.Native Animals of New Zealand. The only complete coverage of the New Zealand fauna. Aims necessarily at the elementary level. The illustrations are excellent for spot identifications.

Powell, A. W. B.Shellfish of New Zealand. Valuable for checklist and reference to literature.

Suter, H.Manual of the New Zealand Mollusca. Needs much revision but still indispensable for molluscan work. Should be supplemented by nomenclatural corrections of Iredale, (T.N.Z.I. 1915) and Finlay (T.N.Z.I. 1927) as well as numerous published papers listed by Powell.

  • Foraminifera
    • Mr. N. Hornibrook, Geological Survey, The Terrace Wgton.

  • Coelenterata
    • Anemones:
      • Miss Gwyneth Parry, Canterbury University College, Christchurch (at present at Glasgow Univ.).

      • Papers by F. G. A. Stuckey, T.N.Z.I. 1908, vol. 41.

    • Corals, Ctenophores, Hydrozoans:
      • Miss P. M. Ralph, Victoria University College, Wellington.

    • Alcyonarians:
      • Miss Beryl Brewin, Otago University, Dunedin.

    page 113
  • Porifera
    • Miss S. Jonathan, Canterbury University College.

  • Platyhelminthes
    • Turbellaria:
      • Prof. E. Percival, Canterbury University College. (esp. Rhabdocoelida.)

    • Land Planarians:
      • Miss M. L. Fyfe, Otago University.

    • Freshwater Planarians:
      • Miss F. R. Nurse, Canterbury University College.

  • Brachiopoda
    • Prof. E. Percival, Canterbury University College.

  • Rotifera
    • Mr. C. R. Russell, 108 Knowles Street, Christchurch.

  • Polyzoa (Fossil)
    • Dr. G. H. Uttley, Canterbury Museum, Christchurch.

    • Dr. Brown, Geol. Dept., Otago University.

  • Annelida
    • Oligochaeta:
      • Mr. K. E. Lee, Soil Bureau, Wellington.

      • Papers by Sir William Benham in T.R.N.Z., Proc. Linn. Soc. (Lond.), and other journals.

    • Polychaeta:
      • Mr. George Knox, Canterbury University College.

      • Papers by Sir William Benham.

    • Hirudinea:
  • Crustacea
    • Brachyura:
    • Barnacles:
    • Planktonic Crustacea:
      • Mr. A. S. Fuller, Auckland University College.

      • Mr. B. M. Bary, Victoria University College.

    • Ostracoda:
      • Mr. N. Hornibrook, Geological Survey, Wellington.

    • Amphipoda, Isopod:
      • Mr. A. W. E. Hurley, Victoria University College.

  • Mollusca
    • Mr. A. W. B. Powell, Auckland Museum.

    • Mr. R. K. Dell, Dominion Museum (esp. Cephalopoda).

    • Dr. Marwick, Geol. Survey, Wellington.

    • Mr. C. A. Fleming, Geological Survey, Wellington.

      page 114
    • Opisthobranchs:
      • Miss Ralph, Victoria University College.

    • Gastropoda, Pelecypoda:
      • Mr. J. E. Morton, Auckland University College (Structure and Ecology).

  • Echinodermata
    • Asteroidea, Echinoidea, Ophiuroidea, Crinoidea:
      • Dr. H. B. Fell, Victoria University College.

    • Holothuroide:
  • Ascidians
    • Miss Beryl M. Brewin, Otago University, Dunedin.

* Later articles will cover methods of collecting and preserving the Insects and Arachnids, the terrestrial Arthropods (Millipedes and Centipedes), Vertebrate animals, and the various groups of endoparasites.—Editor.