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A simple method is described for siting and recording permanent vegetation transects. Based on standard methods, it has the advantages that in forest plants can be relocated quickly and there is no need to set out boundary strings which are time-consuming. When necessary the recording of a transect can be effected by one observer.
Recording vegetation in permanently marked areas at suitable time intervals is the most direct method of measuring rates and trends of succession. As greater emphasis is placed on maintaining vegetation reserves in satisfactory condition, there will be an increasing demand for information on succession. The procedure outlined here has been in use for some years by the writer and has proved suitable for many different types of vegetation. It is modified from standard techniques and may have advantages in ease of use, particularly when only one recorder is available.
The siting of permanent transects usually depends on a subjective judgement influenced by the aims of the study. Two common objectives can be mentioned: 1. To record vegetation changes occuring at a particular site, e.g. a boundary between scrub and tussockland. The vegetation need not be typical of the surrounding area and the transect may include more than one type of vegetation. 2. To record the changes occurring within a particular type of vegetation. In this case the transects should be located in stands representative of the vegetation type and hence a vegetation survey is a necessary pre-requisite.
Within a single type of vegetation much of the variation in rates and trends of succession will be associated with differences in site, particularly slope and position on the slope relative to ridge crests and valley bottoms. Thus some thought should be given to the site conditions of each transect so that future comparisons between similar sites in different vegetations, or contrasting sites in the same vegetation, can be made and the maximum amount of information gained.
Transects are orientated with the long axes parallel with the slope. On some steep slopes it may be easier to record a transect lying at right angles to the slope but in illustrating such a transect, features of growth form related to the slope may be lost.
Belt (rectangular) transects are faster to record and often give more information about the vegetation than do square quadrats of the same area (Clapham 1932). In the method described here, transect lengths of 20, 30 or 40 m are used according to the vegetation height, 30 m or more being most useful in forest. A width of 4 m is most satisfactory in forest and this can be reduced to 1 m or less in grassland. However, when a change from grassland to forest is anticipated, a standardised 4 m wide transect of fixed length will facilitate comparisons at a later date. The time needed for recording increases greatly with widths exceeding 4 m and furthermore the recorder is forced to enter the transect more frequently.
A graduated tape is stretched taut between two permanent marker posts (e.g. aluminium angle standards, waratah steel standards, galvanised iron pipes, tanalised pine posts) protruding 0.8 to 1 m above ground level. Unless in remote areas, the marker posts are best left unpainted so that they do not attract attention. The tape marks the centre-line of the transect and from it, offset distances to plants within each of the 2 m strips either side of the tape can be measured using a small measuring tape or, for greater speed, a 2 m long graduated pole or rod. Each plant recorded is identified and located according to two co-ordinates — distance along the centre-line tape and offset distance from the tape. This information can be plotted directly on a transect chart or transferred to a chart later.
Charting of low-growing vegetation within a 0.5 or 1 m wide transect is simplified by using graduated tapes along both sides of the transect. Vegetation boundaries can then be plotted within successive segments of the transect framed by two graduated rods or laths spanning the transect and of length equal to the transect width. For some plants the point of emergence of the main stem can be indicated; this is essential if the vegetation is to be followed through to the forest stage when charting of plant crowns will no longer be practical.
The positions of trees and tall saplings only are located unless the position of a smaller plant is considered important. Of the tall saplings, only those plants having a diameter at breast height (dbh) > 2 cm are measured, breast height being taken as 1.4 m. The stem measurement made in the field is circumference at breast height (cbh) which can be converted to a dbh measurement subsequently if a circumference-diameter tape is not used. Sometimes it is of value to measure the cbh of trees or saplings immediately outside the transect where these can be re-located in the future.
Where major branching occurs below 1.4 m above ground level, the plant is treated as multiple-stemmed. In such plants identification and measurement of all stems increases the amount of growth data that can be gained and allows the growth of different parts of the same tree to be compared. With multiple-stemmed plants on sloping ground, the stem growing furthest up the slope is measured first and the remaining stems then measured in clockwise order. The stems of combines, e.g. rata + rimu, are measured separately whenever this is possible. Prostrate or leaning trunks are measured at a distance of 1.4 m from a point level with the centre of the trunk at its base. Dead trunks or limbs are not measured but their numbers, positions and sometimes condition are recorded.
All other plants within the transect, including epiphytes, are recorded qualitatively according to species and size classes using the following scheme:
It is often desirable to have a more complete picture of the composition of the uppermost (canopy) layer and understorey of the
For sampling or describing the understorey an arbitrary but useful method of subdividing the space below the canopy is as follows:
In low-growing vegetation such as grassland or herbaceous swards, it is often difficult to distinguish individuals of each species, particularly when the vegetation is being grazed. To attempt charting the position of each individual within a transect may take more time than can be justified by the information gained. It is thus essential to decide what particular vegetation change or changes are to be recorded, even though some changes cannot always be anticipated. For example, the interest in a grassland might be the rate at which it is being invaded by woody plants. The position, heights, and possibly crown outlines, of all woody plants would be plotted whereas the grassland might be characterised by a single point analysis of crown-cover made along the centre-line of the transect. In another case one might chart the distribution of a single species within the
Bl. cap.: Blechnum capense
Cass: Cassinia retorta
Cy deal: Cyathea dealbata
Dac. glom.: Dactylis glomerata
Ger. molle: Geranium molle
Hol. lan.: Holcus lanatus
Lept. scop. and L.s.: Leptospermum scoparium
Met. ex.: Metrosideros excelsa
Pitt crass: Pittosporum crassifolium
Plant. lanc.: Plantago lanceolata
Pt. ag. and Pt.: Pteridium aquilinum
Sc. nod.: Scirpus nodosus
In some types of short vegetation it is possible to plot boundaries or sharp transitions in composition readily and to characterise the vegetation in each part of the mosaic with a simple descriptive name (Fig. 1).
Profile diagrams are not an essential part of permanent transect recording but can be useful particularly where structural changes are expected. In forest the centre-line tape of the transect can be used as a baseline for drawing a profile diagram of the plants as accurately as possible, either estimating heights by eye or using an abney‘ level or 4 m pole to measure heights. Alternatively, in forest where the density of plants does not allow a clear cross-section to be drawn, a profile diagram can be based on a tape stretched from tree to tree in a zig-zag manner. In this case only the tall trees touching the tape are drawn and then these should be indicated by showing the baseline of the profile diagram on the transect chart. With either alternative, the drawing of understorey plants is restricted to those greater than 0.3 m ht and growing within a metre-wide transect centred on the baseline. Only a segment of the crown of each of the taller trees is drawn but what is shown must be sufficient to convey a realistic picture of the vegetation structure. In comparing two forest profile diagrams of the same transect made at different times, it should be remembered that reliability will be greater at the lower levels.
Photographs taken from fixed points around a transect usually convey additional information. In forest only the understorey can be photographed satisfactorily and here it is essential to be able to relocate the photo-point with respect to ground position, height and exact direction of the camera. Slight changes in the position of the lens between photographs can give a false picture of changes in the height of plants. A 2 m graduated pole can be used to overcome this difficulty of obtaining a vertical scale. Ideally the boundaries of part of the transect should be included in the photograph and the field of view can be centred on a permanent marker. Sometimes it is possible to photograph a transect from a nearby vantage point or tree; this is particularly useful when future understorey growth is expected to obscure the field of view on the ground.
It is most important to provide a set of instructions that will allow a future worker to re-locate the transect. There are examples on record where it has not been possible to find potentially valuable
Location: Lady Alice Island, Chickens group.
Date: 28/3/1971.
Recorder:
Vegetation type: Metrosideros excelsa-Vitex lucens forest.
Site type: Ridge crest.
Position: Climb slope westwards from main valley draining into South Cove. On reaching crest of ridge, proceed southwards and then south-south-eastwards along the ridge until shortly before it drops steeply towards Koputotara Point. At this place a trench-like depression about 4 m wide and from 1 to 5 m deep crosses the ridge in a NW-SE direction. A large pohutukawa tree, with three trunks branching 1.5 m above ground, grows on the ridge crest at the southern edge of the trench. The marker post and point of origin of the transect (waratah steel standard) is six paces from the base of this pohutukawa on a magnetic bearing of 225°.
To establish permanent transects in any type of vegetation is time-consuming; in forest this method takes from two to four hours per transect with two persons. If specific questions are asked that
The basic parameters mentioned have been numbers of individuals according to size classes for each species, trunk circumference of trees > 2 cm dbh, and canopy cover. Any additional parameters can be recorded, depending on the aims of the study. In order to reduce the chances of error, a record of the original field measurements
Sometimes it is possible to mark the positions and measure plants in the vicinity of but outside a transect. In this way sample size can be increased so that a particular species population is sampled adequately. Individual plants can be labelled, care being taken to ensure that wiring on the label does not restrict future growth.
Other types of repeated observation can be made in permanent transects apart from those relating to live plants. For example, the decay rates of fallen branches from different species in various environments is a topic about which little is known. The unexpected results which permanent transects sometimes produce, amply reward the observer for the time he takes in their recording.
Finally it must be emphasised that recording vegetation in a permanent transect invariably has some modifying effect on the plants, particularly when more than one person is recording. Every care should be taken to minimise this disturbance.
I thank Mr A. E. Ester of Botany Division, D.S.I.R., for encouraging me to publish this paper. Discussion with Mr Esler, Mr R. G. Bagnall of Victoria University and Mr
The Xenophyophores are a group of marine, giant protozoans (Schulze, 1907) recently established as a sub-class of the Rhizopodea (Tendal, 1972). They are known to live on the seabed at depths ranging from 1 m. to 7,000 m. but have been reported commonly only from abyssal depths. In this paper I wish to draw attention to their presence in New Zealand waters in the hope that they be recognised more commonly in the future.
Xenophyophores were first reported from New Zealand by Lewis (1966) who described a new species of Syringammina, a genus then regarded as belonging to the arenaceous foraminifera. Subsequently several specimens that appeared to be allied to Syringammina were sorted from trawl samples by Mr. W. de L. Main of the New Zealand Oceanographic Institute. These were kindly loaned to me for identification. For a full description of these and all other known xenophyophores, together with a review of their biology and taxonomy, the reader is referred to the report by Tendal (1972).
Xenophyophores are by far the largest protozoans known; they range in size from 1 mm. to 25 cm. Nevertheless, they are frequently overlooked. Most of them have an external test which is composed of agglutinated grains termed xenophyae. The xenophyae, which may be mineral grains, sponge spicules, foraminiferal tests or radiolarian tests, are only loosely cemented so that the test is fragile. Depending on the abundance of xenophyae, the test may feel like a friable sandstone, a doughy lump or a wet rag. The form of the test may be spherical, plate-like, irregular or a ball of anastomosing walls or tubes. Xenophyophores may easily be mistaken either for broken and decayed parts of other animals such as sponges, foraminifera, coelenterates, bryozoans and ascidians or for inorganic concrements. Such dubious material is generally handled and investigated with care only where other biological material is scarce. This lack of care may be the reason for by far the largest number of xenophyophores being recorded from abyssal depths. However, the New Zealand material was recognised in biologically rich environments on the upper part of the continental slope despite the fact that it is amongst the most fragile ever found.
Much of the internal structure of the xenophyophores can be investigated with a common dissecting microscope, the specimen being
The xenophyophores are protozoans whose protoplasm is contained largely in branched, transparent, organic tubes. The tubes, which are filled with plasma, are called granellare. The plasma includes nuclei of several different types as well as flat, rounded or spindle-shaped crystals of barium sulphate known as granellae. Part of the plasma protrudes from open ends of the tubes as branching pseudopodia which spread out over the surrounding substrate.
Most of any xenophyophore is dead matter. This includes large, membrane-covered masses of faecal pellets, known as stercomare, which are retained outside the tubes, perhaps as protection and support for the tubes. The stercomare are characteristic of the xenophyophores. Tubes and stercomare are generally enclosed by an exterior wall of xenophyae, which are loosely cemented by a mucopolysaccharid.
Xenophyophores probably feed on bacteria that live on the surrounding substrate. Food is collected by the pseudopodia which also collect xenophyae and may move the animal along. Pseudopodial fans have been seen in photographs of xenophyophores living on the abyssal ocean floor near New Britain (Western Pacific) (Lemche et al.). Because xenophyophores are commonly recorded from areas of high surface production or from close to land, it is thought that they require a relatively large food supply.
A few shallow-water species have biflagellate gametes and therefore must reproduce by gametogamy. Amoeba-like stages occur in the life cycle, but their role is not definitely decided. Some deep-sea species appear to have amoeboid gametes and therefore may also reproduce by gamontogamy. In a number of species, for instance within the genus Syringammina, the juvenile stages have a test morphology that is different from the adult.
Phylum PROTOZOA High-level classification according to Honigberg et al. (1964).
Subphylum SARCOMASTIGOPHORA Honigberg and Balamuth, 1963
Superclass SARCODINA Hertwig and Lesser, 1874
Class RHIZOPODEA von Siebold, 1845
Subclass XENOPHYOPHORA Tendel, 1972
Rhizopodea with plasma in strongly branched tubes, granellae in the plasma, and voluminous masses of faecal pellets (stercomare) retained outside the tubes.
The subclass Xenophyophoria has two orders. All known New Zealand specimens belong to the order Psamminida which contains xenophyophores of
Test lumpy with numerous anastomosing branches. The texture is friable, The branches have two layers: a thin, hard exterior layer of cemented fine granular matter with some xenophyae and a thick interior layer containing xenophyae loosely associated with granellare and stercomare.
R. novazealandica n. sp., Tendal 1972, p. 29, pl. III, E-G
R. novazealandica is the type species for the genus.
Description: Two specimens and a fragment are known. The body is rounded, somewhat flattened on one side, and measures up to about 60 mm. in diameter. It consists of anastomosing, lamella-like branches measuring 3-7 mm. in width, most of them about 5 mm. The open spaces in the network are circular or oval, and are 2-10 mm. wide. The colour is light grey. The internal xenophyae are foraminiferan tests. The thin surface layer consists of wellcemented calcareous matter with only a few foraminiferan tests.
The reddish-brown granellare are 40-60 mic. in diameter. Granellae seem to be scarce; they are rounded, elongate, and measure 1-3 mic. in length. Nuclei are spherical to ellipsoidal and measure 3-5 mic. in diameter. The stercomare anastomose and are 40-150 mic. in diameter.
Localities: NZOI Sta. E903 a, b: 37° 33′ S., 172° 05′ E.; top of Aotea Seamount; depth—a, 960 m., b, 984 m.; bottom—volcanic rock with thin covering of foraminiferal sand; temperature The temperatures are from Garner and Ridgway (1965).
NZOI Sta. F913, 34° 43.5′ S., 174° 31.5′ E.: continental slope off Bay of Islands; depth 743 m.; bottom—foraminiferal sand with detrital mud; temperature—about 7° C. 1 fragment.
R. labyrinthica n. sp., Tendal 1972, p. 30. pl. III, H; IV, A
Description: Two specimens are known. The body is rounded, somewhat flattened on one side, and measures up to about 23 mm. in diameter. It consists of anastomosing branches that are circular or flattened in cross-section, and measure 1-2 mm. in diameter. The open spaces in the network are circular or oval, and are 1-8 mm. wide. The colour is whitish. The internal xenophyae are foraminiferan tests. The surface is covered by a well-cemented thin layer of fine, granular calcareous and silicious material.
The granellare measure 25-60 mic. in diameter. Granellae are rare; they are rounded and measure up to 5 mic. in diameter. Nuclei are spherical to slightly ellipsoidal and measure 3-5 mic. in diameter. The stercomare measure 25-160 mic. in diameter.
Locality: NZOI Sta. F913, 34° 43.5′ S., 174° 31.5′ E.; continental slope off Bay of Islands; depth—743 m.; bottom—foraminiferal and with detrital mud; temperature—about 7° C. 2 specimens.
Reticulammina lamellata, top view; X 1.5. Upper right: R. labyrinthica, top view; X 2.2. Middle left: R. novazealandica, top view; X 1.5. Middle right: R. novazealandica, side view; X 0.8. Lower left: Syringammina fragilissima fragment, side view; X 3.2. Lower right: S. tasmanensis, side view of sectioned paratype; X 1.8.
Description: One specimen is known. The body is lumpy and somewhat flattened, measuring 32 mm. in diameter and 15 mm. in height. Most of the anastomosing branches are lamellate, 1-2 mm. wide; a few are nearly circular in cross-section and measure about 1 mm. in diameter. Large irregular cavities occur between the branches. The colour is greyish. The internal xenophyae are sand grains. The surface is covered by a thin layer of sand grains and fine granular matter.
The yellow-brown grannellare measure 12-90 mic. in diameter. Granellae are up to 5 mic. in length. The stercomare measure 50-120 mic. in diameter.
Locality: NZOI Sta. F881, 37° 07.8′ S., 177° 14′ E.; continental slope off Bay of Plenty; depth—1253 m.; bottom—foraminiferal sand with sand and glauconite; temperature—about 4° C. 1 specimen.
The test is constructed by numerous tubes of tightly cemented xenophyae. The tubes are arranged in a radiating manner, single tubes being connected with other tubes by side branches. The xenophyae are restricted to the tube walls, and only granellare and stercomare are found in the interior.
Description: The single New Zealand specimen is a nearly spherical fragment about 9 mm. in diameter. The colour is grey, and the test is very fragile. The anastomosing lateral radial tube branches are arranged in relatively conspicuous layers 0.9-2.8 mm. apart. The tube diameter ranges from 0.5-1.6 mm. and tubes with different diameters are intermingled. The xenophyae are sand grains, mineral particles, and fine grained material.
Each tube contains three to six peripheral longitudinally extending head branches of granellare and one centrally placed, thick stercomare mass. The granellare measure 20-140 mic. in diameter. Granellae are oval or rounded, most of them less than 1 mic. in diameter. The stercomare measure 200-540 mic. in diameter.
Locality: NZOI Sta. E417, 45° 12′ S., 171° 49′ E.; continental slope off Otago; depth—860 m.; bottom—detrital sandy mud with shells and foraminifers; temperature—about 5.5° C. 1 fragment.
Description: Six specimens are known. The body is roughly hemispherical and up to 44 mm. in diameter. The colour is light grey, and the test is extremely friable. The radial tubes anastomose irregularly in the centre, and more regularly in the periphery where the lateral tube branches form concentrically arranged consecutive layers mostly 0-0.6 mm. apart. The tubes are mostly 1.1-1.5 mm. in diameter. The xenophyae are predominantly foraminiferan tests and fine-grained calcareous matter.
Each tube contains one central granellare branch and 2-4 peripheral stercomare masses. The granellare measure 115-193 mic. in diameter. Granellae measure up to 5 mic. in length. Nuclei are spherical to almost ellipsoidal and 2-3 mic. in diameter. The stercomare measure 77-460 mic. in diameter.
Localities: NZOI Sta. D227, 39° 50′ S., 169° 43′ E.; on the Challenger Plateau; depth — 711 m.; bottom — globigerina ooze; temperature — about 6.5° C. 4 specimens.
NZOI Sta. D228, 39° 08′ S., 170° 17′ E.; on the Challenger Plateau; depth — 664 m.; bottom — globigerina ooze; temperature — about 8° C. 2 specimens.
All of the New Zealand specimens were trawled from bathyal depths between 600 m. and 1,300 m, where temperatures range from 4° C. to 8° C. They are some of the few xenophyophores that have been dredged from such depths; most being from abyseal depths. They are also some of the few that have been found close to established marine stations.
The three species of Reticulammina were found only around the northern part of North Island. The genus Reticulammina may be endemic to New Zealand, the only other species in the genus, R. cretacea (Haeckel, 1889), being of dubious taxonomic position. Syringammina tasmanensis has been found on the Challenger Plateau to the west of New Zealand and nowhere else. Reticulammina and S. tasmannesis may together constitute an endemic xenophyophoria fauna at bathyl depths around New Zealand. The other New Zealand species, S. fragilissima, was originally described from the North Atlantic but may also occur in the South Atlantic close to Antarctica.
Xenophyophores could occur at any depth around New Zealand and it is hoped that marine scientists will examine the debris in their trawls very carefully to see whether any of it might belong to this group.
I am deeply indebted to Dr. Syringammina tasmanensis.
Lights Have Often Been Used as aids in collecting various marine and freshwater organisms. These exploit the positive phototropism exhibited by certain species, e.g. cumaceans (Hale, 1953), aquatic insect larvae (Hungerford et al., 1955; Washino and Hokama, 1968), assorted freshwater invertebrates (Espinosa and Clark, 1972), marine invertebrates (Sheard, 1941) and fish larvae and juveniles (Winn and Miller, 1954; Parsons and Hodder, 1970). Various systems have been used, from suspended lights and dipnets (Winn and Miller, 1954) to more elaborate submersible and semi-submersible traps (Hungerford et al., 1955; Washino and Hokama, 1968; Espinosa and Clark, 1972).
The light-trap described here was designed for collecting larval and juvenile fish of the families Tripterygiidae (‘blennies’), Clinidae and Gobiesocidae (clingfish). The trap was to be used close inshore from rocks, wharves and boats. Hence it needed to be light yet robust enough to withstand the normal wear and tear of field handling. The light-traps referred to earlier that were designed for collecting aquatic insects etc., were too small to collect large numbers of fish larvae. A trap similar to that used by Davies (1954) and Baker (1972) for collecting pilchard larvae was available. However, this was too cumbersome for my purpose. Furthermore, the total collecting area of the cones was small relative to the area of the trap radiating light, thus decreasing the catching efficiency. I have used a sealed light on the end of a long pole, the light being placed just under the water to attract fish larvae that were then captured by a dipnet. This method, while effective in rocky shore surge channels not suitable for set traps, did not give any quantitative assessment, however rough, of larval number. Furthermore, light traps have an advantage in that they can be left unattended for several hours.
The trap needed to be submersible to different depths, portable and useable in the sea. Certain basic problems therefore had to be overcome. These were principally the sealing of the light, corrosion, release of water when retrieving the trap, loss of or damage to specimens, and weight of water causing stress on the apparatus. In addition to solving these problems, it was necessary to devise a system whereby the greatest cone aperture area (effective collecting area) was presented to the organisms. Perspex, because of its transparency and durability, was chosen as the main building material.
The trap (Figs. 4 and 5) is essentially a squat perspex ‘box’ with sides that form the outer aperture of four cones. The cones taper to narrow slit-like inner apertures that are in line with a light in the centre of the apparatus. All sides of the trap, therefore, act as effective collecting areas. The top of the ‘box’ is opaque to restrict radiating light to the areas of the cones; organisms are then not likely to approach the light from above the trap but rather from the side in line with the cones. The gauze ‘cod-end’ (bottom of the ‘box’) is four-sided and tapered, ending in a terylene collar designed to hold an Agee jar (Fig. 5). The corners are joined and strengthened by terylene tape. The upper edge of the net is bordered by a 3 cm wide terylene strip, folded from a 6 cm strip. The size of the mesh used for the ‘cod-end’ will depend on the size of the animals to be collected (300 microns for this trap), but mesh size must be large enough to allow reasonably rapid drainage of water from the light-trap. If not the weight of the water retained in the ‘cod-end’ will place undue stress on the whole apparatus. A mesh ‘cod-end’, as distinct from some solid equivalent, has the added advantage of being easily folded. The trap is thereby more readily handled.
The sealed light unit is fastened to the centre of the laminated top (Figs. 4 and 5, A1 and A2) and gives maximum radiation of light through the cones. The light (Fig. 1) consists of a brass holder, the lower portion of which is hollow and threaded to accommodate a small jam jar. This is sealed by pressure against a flat rubber ring. The flex enters the jar through the upper cylindrical stem of the brass holder, and effective sealing is obtained with an ‘O-ring’ forced tightly about the flex by a short bolt. Vaseline is spread liberally over the seals and the rim of the jar. Inside the jar there is a simple brass bulb holder that is screwed firmly to the brass unit, and receives two wires from the flex. Klinger (in Hale, 1953) used a 5,000 watt light, hoping to attract a great variety of marine life. Instead he found this very strong light less effective in attracting organisms than a simple hand-held flashlight. Foxon (1936) and Hale (1943) both found that cumaceans were attracted most effectively by low intensity light. They found that cumaceans tended to shun the brightest areas, preferring to remain on the periphery of the radiated light. A low intensity light (12v 6w) was therefore chosen for this trap.
The cylindrical projection of the brass light holder passes through the laminated top of the trap and is held securely in place by four screws. The light trap is suspended by four bridles, each 54 cm. long with spliced loops at each end. How the bridles are attached
Fig. 1
Fig. 1
This light trap is light and will swing about with the slightest swell. Weights, perhaps those used by divers, may be added to each corner to increase stability. The time the trap is left submerged depends on the locality and type of animal sought. When collecting fish larvae it is advisable to restrict submersion time to no more than half an hour. Any longer and the small delicate larvae are rapidly consumed by isopods etc., and also damaged by general overcrowding. On retrieval the trap should be brought slowly to the surface so that the perspex skirt is just clear of the water. As the ‘cod-end’ is lifted from the water the whole unit is moved from side to side so as to keep the organisms swimming and thus prevent them becoming entangled in the mesh sides. This factor is more important with ‘many-legged’ crustaceans that become readily enmeshed. With the bottle clear of the water the unit may then be brought rapidly up to the wharf.
The light trap has also been successfully used to collect amphipods (Dr. A. A. Fincham, V.U.W.) and epitokous polychaetes (Mr.
I would like to thank Dr.
The New Zealand Zoologist J. von Haast, (1876a), in his description of the species of Beaked Whale Mesoplodon grayi, noted as one of the characteristics of the new species the presence of rather large vestigial maxillary teeth. The occurrence of these teeth in Beaked Whales had already been noted (for a detailed review, see Boschma, 1951), but they are so small that they are generally over looked. In Mesoplodon grayi, however, the maxillary teeth were so conspicuous (lengths up to 12 mm) that von Haast (1876b) concluded that the maxillary teeth (17 to 22 teeth in each row) were functional and not vestigial and therefore proposed a new genus Oulodon to contain his species grayi. However Moore (1968), in his recent taxonomic review of the Beaked Whales, did not recognise Oulodon as a genus, not even as a subgenus.
In later descriptions of stranded Scamperdown Beaked Whales, the rather large maxillary teeth had been recorded (for reviews, see Boschma, 1950 and 1951) and more recently Baker (1972), like von Haast (loc. cit.), cited the size of the maxillary teeth as being one of the characteristics of the species. It is, however, less known that in Mesoplodon grayi (as in a number of other Beaked Whales) vestigial teeth can also be found in the lower jaw.
It seems that they are not present in every specimen but when present are much smaller than the maxillary teeth. (See Fig. 1, specimen 2, at right.)
Recently I had the opportunity to dissect three Scamperdown Beaked Whales. On February 6, 1974, a male specimen, 356.8 cm long, was found in the Port of Napier as was also on the same day at the same locality a female, 373.4 cm long. The next day, in the Port of Napier there occurred a third specimen Mesoplodon grayi, again a male, 398.8 cm long. It is tempting to speculate on the cause or causes of these three strandings at the same date but such is outside the scope of this short paper.
During the dissection of the three specimens I paid special attention to these vestigial teeth and I can confirm the previous descriptions of such teeth in Mesoplodon grayi. I prepared the rows of teeth by keeping intact the strips of gum in which they were imbedded (see Fig. 1). Each row of maxillary teeth was situated just posterior to the singly, well-developed tooth in each ramus of the lower jaw. The vestigial mandibular teeth were found just behind the normal tooth and opposite the maxillary ones. As can be seen in the figure, the teeth are rather large and it is possible that the animals make use of them when feeding. In this respect. Mesoplodon grayi partially resembles Tasmacetus shepherdi Oliver, 1937, Oliver's Beaked Whale, which has, in addition to two large teeth at the end of the lower jaw, two rows of 19 well developed but smaller teeth in the upper jaw and two rows of 26 smaller teeth behind the large ones in the lower jaw. One can speculate whether there is a relationship between the presence of these smaller teeth in Mesoplodon grayi and Tasmacetus shepherdi with the kind of prey they take.
Mesoplodon grayi: 1, maxillary rows of a 373.4 cm long female; 2, maxillary rows and one mandibular row of a 356.8 cm long male; 3, one maxillary row of a 398.8 cm long male.
After cleaning the skulls of the three Scamperdown Beaked Whales I extracted the normal, well-developed mandibular teeth. As is well known, these teeth are situated just anterior to the distal end of the mandibular symphysis. Whilst comparing the teeth with each other, I was struck by the discrepancy between the sizes of the teeth and the total lengths of the animals. In the 373.4 cm long female the lengths by heights of the teeth are 34.0 and 34.9 mm and 34.0 by 34.0 mm. In the small male of 356.8 cm length, the dimensions are 48.9 by 42.7 mm and 46.4 by 42.7 mm. In the larger male of 398.8 cm length, the dimensions are 35.7 by 36.2 mm and 34.4 by 35.3 mm. As in all Beaked Whales there was a distinct sexual dimorphism in the size of the teeth, it was not surprising that the teeth of the female were rather small. That the smaller male had larger teeth than the larger male I cannot explain, the more so as I could not find any significant differences in the state of osseous fusion of the bones between the two male skulls. It might perhaps be useful to check the teeth dimensions in other skulls of Mesoplodon grayi.
Mesoplodon grayi. From left to right: from a 373.4 cm long female; from a 356.8 cm long male; from a 398.8 cm long male. For the dimensions of the teeth in the metric system, see text.
In the dorsal fin of one of the Scamperdown Whales I found, near the posterior rim, a circular hole, looking like a healed wound made by a rifle bullet. As it seemed very unlikely to me that somebody had really taken a shot at the animal, I wondered what had caused the hole — a parasite perhaps? According to Mr. G. P. van Andel (in verbis) this type of hole is often found in the flippers, flukes and dorsal fins of Baleen Whales and Sperm Whales in the Antarctic.
Descriptions of the three main postures of the tunnel web spider P. antipodiana are given. A behavioural/ecological interpretation of each posture is attempted. Emphasis is placed on the importance of the strike posture; and an experiment suggests that the angle the spider assumes to strike at prey is related to the prey height.
Intra- and interspecific encounters are described and it is indicated that the behaviour of this spider may help protect it from attack by small animals such as mice.
The study of postures has been a recurring theme in the field of animal behaviour. Darwin wrote on the topic (1872), followed in the early years of this century by biologists like Heinroth and Craig. Most of the early studies were descriptive and many were concerned with the study of courtship in birds. Later writers began to use the study of postures as a basis for erecting models of behaviour, and the fixity of postures associated with instinctive behaviour was used in attempts to understand the functional organisation of the central nervous system in birds and fish. The so-called ‘hydraulic models’ of Lorenz and Tinbergen were the outcomes of these studies in the 1930′s and 1940's.
The study of postures is still popular with students of animal behaviour, but is more likely to be carried out as part of a wider study of animal communication than as a basis for interpreting the function of the nervous system. For example a recent paper by Wilson (1972) includes areas such as communication by chemical means and by sound as well as the role of postures in communication between animals.
In the field of spider behaviour, the most well known studies have probably been those of Crane (1949). These were concerned with the courtship behaviour of Salticid spiders, a group having good enough vision to communicate by posturing. Most spiders, however, have poor vision, so their postures are less elaborate and are most likely to be linked with the tactile rather than the visual senses. The present study is concerned mainly with an investigation of the rather spectacular aggressive or threat display of the large (body length often to 30 mm) New Zealand Mygalomorph spider, Porrhothele antipodiana, commonly called a tunnel web spider. This spider, like other Mygalomorphs, does not have a well developed visual sense;
Certain aspects of the natural history of P. antipodiana have been published already (Laing, 1973). This spider takes a wide range of prey types; it moves about the environment rather than staying in the one burrow as seems to be the case with the trapdoor spiders; it is strongly photo-negative; and it probably has some natural enemies — for example, the two Pompilid wasps Salius monachus and S. fugax. (For a wide-ranging discussion of the New Zealand Mygalomorphs, see Forster and Forster, 1973.)
The legs are drawn up to cast the cephalothorax into shadow and the area occupied by the spider is at a minimum. This posture is seen when the tunnel in which the spider lives is cut open and the spider is exposed to the light. It is also seen when a spider that has been taken from its web is allowed to run away; in which case it will usually crouch in this posture in the first shaded area it comes to.
When in this posture, the spider may be stroked and prodded without eliciting much response. The same posture is shown by a wide range of spiders — the orb-web spider (Aranea), the large grass spider (Miturga), the Katipo (Latrodectus), and the trapdoor spider (Cantuaria), so it is probably a common posture dictated by spider morphology.
The legs are spread out, the spinnerets are lowered and the fangs may be drawn slightly out of their grooves. This is the posture seen when the spider is at the entrance of its tunnel at night, waiting for prey to cross its sheet web. In this posture, the spider is ready for rapid activity in any direction. When running toward the prey, the spider often overshoots the prey animal, coming to rest with its palps touching the prey. Because its body is raised slightly on the legs, the spider's ventral surface is some millimetres above the prey, and in this position the fangs need only be raised forward to be in position to strike. It is rarely necessary for the cephalothorax of the spider to be raised by more than 5-10 degrees from the horizontal for the spider to strike.
It seems to be a common assumption that because of the paraxial chelicerae (having fangs moving in a vertical path, not horizontally as in the true spiders) of the Mygalomorph spiders, raising of the body to a substantial angle from the horizontal is needed to bring the fangs into a striking position. The preceding description, which is based on several hundred observations — both day and night, and in the natural habitat of the spider — indicates that the posture of rearing up of the whole body is not used for routine prey capture by this spider at least. Table 1 shows a summary of the observations made on prey killing postures.
P. antipodiana.
P. antipodiana.
The anatomy of the fang may explain how P. antipodiana can strike at prey without rising up to a substantial angle: the length of the fang is about 5 mm in a spider of body length 25 mm and it can be swung through 130 (Fig. 3). This brings the fang into a position where its tip strikes vertically downwards in the initial stages of its movement. Prey such as slaters and the smaller beetles have a body height of 2-5 mm usually, and as P. antipodiana may be standing with the lower edge of the cephalothorax more than 5 mm above the web surface, an upward raising of the cephalothorax of 2-3 mm is all that is needed for the fang to clear the prey on the upward swing. In addition, each parturon is moved sideways from the midline of the body to an angle of 30 degrees (Fig. 4), and this further increases the probability that the fangs, by travelling outwards rather than directly over the prey, will clear the prey on their upward swing.
P. antipodiana.