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Tuatara: Volume 5, Issue 2, August 1953
A Guide to the Athecate (Gymnoblastic) Hydroids and Medusae of New Zealand
A Guide to the Athecate (Gymnoblastic) Hydroids and Medusae of New Zealand
Most people are familiar with the hair-like growth frequently seen on mussel shells and popularly called ‘old man's beard’. This growth is really a hydroid colony. Such may be either of two distinct types, namely thecate hydroids, those in which the animals live in a cup-like extension of the outer protective coat (e.g. ‘old man's beard’) and athecate hydroids in which the animal is without a protective cup. Hydroids are part of a much larger group of animals, the Phylum Cœlenterata, to which belong also the corals and sea-anemones. Hydroids have been a source of delight to sea-shore naturalists for many centuries, but it was not until about the latter part of the eighteenth century and more especially through the research of John Ellis that they were finally placed in the animal and not the plant kingdom. Here are a few sentences from Ellis's introduction to his book:
‘An Essay towards a Natural History of Corallines and other Marine Productions of the likekind’ (1755).
‘As I was convinced from my own Observations of the Subjects themselves, that several, which had hitherto been considered by Naturalists, as Marine Vegetables, were in Reality of animal Production: So from the Opinions of several Gentlemen then present, my Suspicions were increased, that others likewise, which I had taken for Vegetables might in Reality be of an animal Nature.
‘To determine how far these Suspicions were just, it seemed the most expedient to examine the Subjects, when recent, with Attention.… Here we had an Opportunity of seeing these disputed Beings called branched Corallines, alive in Sea-water, by the Help of a very commodious Microscope, of Mr. Cuff's the Optician in Fleetstreet, which I had altered for that Purpose; and was fully convinced, that these apparent plants were ramified Animals in their proper Skins or Cases, not loco-motive; but fixed to Shells of Oysters, Mussels, etc., and to Fucus's.’
For many years the hydroids were called Zoophytes (zoon — animal, and phyton — plant), a word carried over from those earlier days. A glance at the figures accompanying the key will show how plant-like many of page 60 them are. The hydroids are predominantly marine and frequently found growing on seaweeds and mussels in intertidal pools and also in deeper water. An interesting feature in their life history is the budding off from the hydroid colony of free-swimming jelly fish (medusa). The medusæ grow from any one of several regions of the colony. In addition to being the active swimming stage of the life cycle, the medusa is also the sexually mature form. A typical Athecate medusa is shown in Fig. 18. The larva produced by the union of gametes is a ciliated free-swimming form called a planula (Fig. 6b). In due course the planula sinks to the bottom and attaches itself by one end. At the other end a mouth and tentacles grow and eventually another hydroid colony is formed. (Fig. 6c.) Thus there are two stages in the life cycle of the hydroids, a fixed colony and a free-swimming medusa. This feature of the life cycle led to considerable confusion in early systematic work and still gives the present-day systematist many headaches. It will be realised readily that unless the hydroid is ‘caught in the act’ of producing medusae, different specific names may, and in fact have been, given to the two stages of the life cycle. There are still a number of hydroid colonies of which we have no knowledge of the adult medusa and mature medusae of which we have no knowledge of the hydroid generation.
Variations of the typical life cycle described above are found. There is a tendency towards degeneration of the medusa and its retention on the parent colony. All grades from perfect medusae retained on the parent colony to ovoid sac-like bodies (sporosacs) simply serving for the ripening of the sex cells, are found. The genus Tubularia (Fig. 12) has reproductive buds (gonophores) that retain some medusoid features but remain attached to the parent animal, and further, the planula stage is passed through within the gonophore. The released larval stage is an advance on the planula and is known as an actinula. The actinula becomes fixed to the substratum and gives rise to the new colony. The gonophores of Hydractinia and Cordylophora (Figs. 1 and 6) are examples of sporosacs. These also remain attached to the parent colony.
Nomenclature
Some technical terms have already been explained above. The living tissue of the colony (cœnosarc) is covered by an outer chitinous protective sheath (perisarc) secreted by the living tissue. A typical hydroid animal (zooid) has an attaching basal region frequently extending over the substratum as a network of tubes (stolons or hydrorhiza), a stalk or stem (hydrocaulus) and a terminal individual (hydranth). In the Athecate hydroids, the perisarc typically covers the stolons and hydrocaulus only, but may extend as a thin covering round the basal region of the hydranth. The hydranth is the feeding individual and has a terminal mouth borne on an elevated structure (hypostome or proboscis), and tentacles. These tentacles may be either long, thin, and finger-like (filiform) or shorter and page 61 thicker with a prominent rounded head (capitate). On the tentacles are stinging cells (nematocysts) which are characteristic of not only the hydroids but the whole of the Phylum Coelenterata. Nematocysts are most abundant on the tentacles of both hydroid and medusa, frequently grouped as knobs and circular or spiral bands. They may, however, be found elsewhere in the outer layer of the cœnsarc. The position and type of tentacle is a ready means of distinguishing the majority of families of Athecate hydroids, and their medusæ.
Technique
As the shape, tentacle form, and other features of the hydranth and gonophore are important in classification it is very desirable that these should be well extended before killing and preserving. Magnesium chloride has been found to be a good narcotising agent. For every litre of sea water add 33 cc. of saturated solution of magnesium chloride in water. Add gradually, but preferably within half an hour. For fresh-water forms slightly stronger solutions should be used. Fix and preserve in 70% ethyl alcohol. If permanent preparations for microscopical examination are required, specimens stain excellently with acetic-acid-alum carmine, and can be cleared and mounted in Canada Balsam. (See Tuatara 5(1): 14.) A technique that gives good results if position and structure of nematocysts is particularly desired is to mount the specimen directly in Polyvinyl alcohol. (For recipe of polyvinyl alcohol see Salmon, J. T., 1949: Trans. Roy. Soc. N.Z. 77(5): 251.)
In the field a hand lens is often sufficient to distinguish the different families of Athecate hydroid, but the microscope will frequently be necessary to diagnose correctly individual species. One is very tempted to use the vivid colours found in the Athecate hydroids as a means of identification, but it should be noted that colour is not a very reliable guide as to species, and that change of form may also occur from the juvenile state to the adult in both medusa and fixed colony. For example, adult colonies may be fasciculated, i.e. the main stem and some of the branches may be formed of many tubes instead of one (Fig. 3a) whereas the young colony may have a simple unfasciculated stem but otherwise possess the main characters of the species.
Systematics
It is sufficient for the purpose of the present key to briefly explain the name changes that have occurred in the group since Bale's paper in the Trans. N.Z. Inst. Vol. 55, 1924. This is the last publication of any size on New Zealand hydroids found in a New Zealand journal. Trebilcock (1928) recognised that Ascidioclava parasitica Kirk was synonymous with Endocrypta huntsmani Fraser. Totton (1930) describes a Eudendrium sp. which he considers may be synonymous with E. novæ-zelandiæ Marktanner-Turneretscher, but states that it is difficult to extract from the original page 62 description any diagnostic specific characters. On these grounds E. novæ-zclandiæ is best considered an unidentifiable species and has accordingly been left out of the present key. The hydroid and medusa described by me in Trans. Roy. Soc. N.Z.1947 Vol.76(3): 414-420 as Cnidonema vallentini Browne is a synonym of Staurocladia hodgsoni (Browne). One further change, that of Tubularia attenuoides Coughtrey to T. larynx Ellis and Solander is put forward for the first time in this key. Unfortunately the type specimen of T. attenuoides is so badly crushed and dessicated as to be useless for purposes of reference. Comparison of specimens (kindly sent me by Miss B. Brewin, Otago University) from Dunedin Harbour, the locality of the original specimens of T. attenuoides, with specimens of Tubularia larynx from Naples, have convinced me that T. attenuoides is a synonym of T. larynx. Also, there is nothing in the original description of T. attenuoides that would preclude its inclusion within the present concept of T. larynx.
Our Cordylophora lacustris Allman recorded by Hamilton (1883) from the Esk River. Hawkes Bav. has been recognised as a distinct subspecies C. lacustris otagoensis Fyfe (1929. Trans. N.Z. Inst. 59(4): 813-823), but the original description of the specimens from Hawkes Bay is rather inadequate.
It will be noted that some of the species described in the present paper are known in New Zealand only from one generation of the life cycle. As we presume that the missing generation will be recorded sooner or later, and in order to give as complete a reference list as possible, both generations are here described.
References
There is no publication solely devoted to N.Z. Athecate hydroids, and the species are found described throughout the general hydroid literature of the country. There is a check list of the N.Z. Hydroid fauna by H. Ferquhar in the Trans. N.Z. Institute 1896 Vol. 28: 459-468. This list is supplemented by later papers, viz: Hilgendorf, F. W., 1897, Trans. N.Z. Inst., 30: 200-218; Hartlaub, C., 1901, Zool. Jahrb., xiv; Bale, W. M., 1924. Trans. N.Z. Inst., 55: 225-268; Trebilcock, R. E., 1928, Proc. Roy. Soc. Victoria 41: 1-31; and Totton, A. Knyvett, 1930, Rpts. Brit, Ant. Exp. (‘Terra Nova’) V(5): 131-252. Two classical English texts — ‘A Monograph of the Gvmnoblastic or Tubularian Hydroids’ (G. J. Allman — Ray. Soc. 1872) and ‘A History of British Hydroid Zoophytes’ (Thomas Hincks — John van Voorst, London, 1868) are still consulted frequently by hydroid workers.
Note: All habit studies on Plates I-IV are natural size except Fig. 14 which is approximately quarter natural size.
Key to the Athecate (Gymnoblastic) Hydroids of New Zealand
| 1 |
(12) Hydranths with a single whorl (circle) of filiform tentacles. |
| 2 |
(3) Perisarc not well developed; hydranths devoid of perisarc; zooids growing singly from a stoloniferous network of tubes covered with thin perisarc and giving rise to spines unless the colony is otherwise protected. Stoloniferous tubes may be covered with a layer of free cœnosarc; colonies with two or more kinds of individual and diœcious; reproductive zooids smaller than feeding zooids or may be aborted. F. Hydractinidæ. Stolon network covered with free cœnosarc; gonophores producing sporosacs. G. Hydractinia. Feeding zooids 3 to 5 mm. high, 9 to 13 tentacles in ‘two series’; dactylozooids (protective zooids) and very small spines present, but both dactylozooids and spines scarce; sporosacs on short stalks borne slightly above the mid-line of the zooid. female with approximately 8 eggs. Hydractinia (?) parvispina Hartlaub. * Fig. 1. Intertidal; reef Portobello Marine Biological Station. |
| 3 |
(2) Perisarc well developed, colonies usually branched. |
| 4 |
(7) Hydranths with trumpet-shaped proboscis; gonophores producing fixed sporosacs; male and female gonophores dissimilar, male gonophores in whorls, female in clusters. F. Eudendridæ, G. Eudendrium (only genus of family). |
| 5 |
(6) Stem not fasciculated, perisarc annulated throughout. Hydranths with about 20 to 25 tentacles; gonophores with short stalks and formed from a circular groove near the base of the hydranth, female globular, male two-chambered oval and forming a whorl round the body of the hydranth; hydranth usually degenerates after the formation of the gonophores. Eudendrium insigne Hincks *. Fig. 2. Drift; on seaweed, many East Coast beaches, Auckland to Gisborne. |
| 6 |
(5) Stem fasciculated; perisarc not annulated throughout. Eudendrium sp. Totton 1930. 11-20 fath. Near North Cape. |
| 7 |
(4) Hydranths with conical proboscis, male and female gonophores similar and producing fixed sporosacs or free medusæ. F. Atractylidæ. |
| 8 |
(11) Colonies much branched. Perisarc well developed on stem and branches; gonophores stalked, producing free medusæ. G. Bougainvillia. |
| 9 |
(10) Ultimate branchlets and unfasciculated branches closely wrinkled throughout; hydranths with 8 to 10 tentacles; gonophores singly or in clusters from the hydranth stalks. Medusa unknown. Bougainvillia inæqualis Fraser *. Fig. 3. Intertidal; Menzies Bay, Lyttelton Harbour, on shells of Amphidesma australe. page 64 |
| 10 |
(9) Ultimate branchlets and unfasciculated branches with few shallow annulations at their origins not wrinkled throughout; perisarc carried over the body of the hydranth as far as the base of the tentacles; hydranth with about 12 tentacles, gonophores on moderately long stems on the upper branches and occur singly or in groups of two or more. Bougainvillia ramosa Van Beneden *. Figs.9, 25. Intertidal; reef, Marine Biological Station, Portobello; drift, large colonies West Coast beaches, Coromandel Peninsula. |
| 11 |
(8) Colony not branched or but slightly branched. Perisarc well developed on stem; gonophores stalked producing free medusæ. G. Stomotoca. Base of stems with 2 to 5 annulations and at their base of origin are same diameter as the branched stolons but become much thicker; branches when present annulated at the point of origin. Stomotoca rugosa (Mayer) *. Figs. 8, 17. Known only from medusa in New Zealand. |
| 12 |
(1) Hydranths with tentacles otherwise. |
| 13 |
(28) Hydranths with scattered tentacles. |
| 14 |
(23) Hydranths with scattered filiform tentacles. |
| 15 |
(22) Colonies fixed, gonophores giving rise to sporosacs or free medusæ. F. Clavidæ. |
| 16 |
(19) Colonies branched. (Fig. 3B.) |
| 17 |
(18) Brackish water or freshwater forms; gonophores producing fixed sporosacs. G. Cordylophora. Stolons unbranched or but slightly branched; persisarc with about 10 annulations at the origin of each branch and gradually terminating on the neck of the hydranth; tentacles about 23 in number; gonophore with thin transparent covering, central core of tissue in ripe female very much reduced with characteristic cup-shaped body at distal end. Cordylophora lacustris Allman sub. sp. otagoensis Fyfe. Fig. 6. On Ruppia, Tomahawk Lagoon, Otago; Lake Ellesmere, Canterbury. |
| 18 |
(17) Marine, gonophores producing free medusæ; colonies with a few small branches from a much-branched stolon or from a fasciculated stem. G. Turritopsis. Perisarc thick, ending abruptly beneath the hydranth; proboscis elongated, each branch bearing a single hydranth; gonophores borne on short stalks at the base of the hydranth. Turritopsis nutricula McCrady. Figs. 10, 18. Intertidal; Wellington Harbour, and reef, Marine Biological Station, Portobello. |
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Plate I
Fig. 1: Hydractinia (?) parvispina -habit; 1a, oral view; 1b, male sporosac; 1c, zooids of female colony. Fig. 2: Eudendrium insigne -habit; 2a, basal portion of colony; 2b, hydranth. Fig. 3: Bougainvillia inæqualis -habit; 3a, fasciculated stem (B. ramosa); 3b, branch of colony; 3c, hydranth. Coe., cœnosarc; Dact., dactylozooid; Hyc., hydrocaulus; Hyd., hydranth; Mth., mouth; Nem., nematocysts; Spor., sporosac; Stol., stolon; Tent., tentacles.
| 19 |
(16) Colonies not branched, or but slightly branched. (Fig. 15.) |
| 20 |
(21) Hydrorhiza of small fibres or almost degenerated; perisarc enveloping the hydrocaulus also unites one with the others, this being in the nature of a fine encrustation; gonophores produce free medusæ. G. Endocrypta. Hydrocaulus usually erect unbranched, perisarc so thin as to be a mere pellicle; hydranth very mobile, exhibiting frequent changes of shape, tentacles up to 24 no definite arrangement; 1 to 3 medusæ buds develop a short distance below the tentacles. Endocrypta huntsmani (Fraser). Fig. 4. All specimens so far from the branchial cavity of a tunicate; e.g. in Cnemidocarpa otagoensis Brewin and Polycarpa sp. for N.Z. These from off Moeraki 40-50 fath. and intertidal rock pools, Wellington Harbour, respectively. |
| 21 |
(20) Hydrorhiza well developed; perisarc rigid, around the whole hydrocaulus not encrusting; gonophores producing fixed sporosacs in clusters from stolon or stem. G. Tubiclava. Perisarc smooth, or slightly annulated at the base of the stem; hydranths very contractile; gonophores 3 to 4 in number developed on the summit of separate stems. Tubiclava rubra Farquhar. Fig. 5. Intertidal; Christchurch area. |
| 22 |
(15) Pelagic hydroids with stem or hydrocaulus almost entirely suppressed; gonophores produce free medusæ. F. Margelopsidæ. Scattered tentacles all over the body of the hydranth, proximal portion of the hydranth modified to form a float. Sub. F. Pelagohydrinæ; sole genus Pelagohydra. Distal portion of the body a flexible proboscis; gonophores between the tentacles of the float form stolons from which are budded medusæ. Pelagohydra mirabilis Dendy. Figs. 7, 23. Drift; Sumner Beach, Christchurch. |
| 23 |
(14) Hydranths with scattered capitate tentacles; gonophores arising from the body of the hydranth producing sporosacs or free medusæ. F. Corynidæ. |
| 24 |
(25) Hydranth body much shorter than stem; gonophores producing fixed sporosacs, among or just proximal to the tentacles; colony branched or unbranched. G. Coryne. Colony branched, stems and branches annulated throughout, perisarc thick, hydranths in basal region surrounded by a loose membranous sheath, tentacles about 20; gonophores globular with short stalk. Coryne vaginata Hincks*. Fig. 13. Drift; on seaweed, Makara Beach, Wellington. |
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Plate II
Fig. 4: Endocrypta huntsmani — habit; 4a, portion of colony with medusæ. Fig. 5: Tubiclava rubra — habit; 5a, portion of colony (polyps contracted). Fig. 6: Cordylophora lacustris otagoensis — habit; 6a, hydranth; 6b, planula; 6c, single zooid of new colony. Figs. 7 and 7a: Pelagohydra mirabilis — zooid; Fig. 8: Stomotoca rugosa — habit; 8a, portion of colony with medusæ buds. Fig. 9: Bougainvillia ramosa — habit; 9a, small branch of colony. Fig. 10: Turritopsis nutricula — habit; 10a, portion of colony. Med. Bud., medusa bud.
| 25 |
(24) Hydranth body usually longer than stem; gonophores producing free medusæ; colony unbranched or irregularly branched; medusæ at liberation with 4 well-developed tentacles. G. Syncoryne. |
| 26 |
(27) Colony slender, simple or sparingly branched; stem smooth, except for a few annulations at the base and a few corrugations immediately above the branch origins; tentacles 20 to 30; gonophores oval not stalked, and in a cluster on the lower part of the hydranth. Medusa, unknown. Syncoryne tenella (Farquhar). Fig. 15. Intertidal: Wellington Harbour; Christchurch area. |
| 27 |
(26) Colony much branched but with branches almost entirely on one side of the stem; stem annulation irregular, often represented by wrinkling only and seldom present on the tops of the branchlets; hydranth with 20 to 30 tentacles; gonophores on short stems. Syncoryne eximia (Allman). Intertidal; rock pools, Oamaru. |
| 28 |
(13) Hydranths with two or more whorls of tentacles. |
| 29 |
(32) Hydranths with proximal and distal whorls of filiform tentacles. |
| 30 |
(31) Colony branched irregularly or unbranched, with a chitinous perisarc and growing from a stolon that usually forms an irregular network; hydranths with distal tentacles in a single whorl; gonophores producing medusoid buds or free medusæ. F. Tubularidæ. Gonophores producing medusoid buds that develop into actinulæ and attached by stalks to the body of the hydranth just above the proximal tentacles. G. Tubularia. Colonies with stems usually branched and tangled at the base, annulated, but the number and nature of annulations variable; proximal and distal tentacles approximately the same number, about 20; gonophores borne on very short stalks, themselves stalked, the whole forming a dense compact cluster; no radial canals, tentacle processes small, conical. Tubularia larynx Ellis and Solander. Fig. 12. Intertidal; Wellington Harbour. Otago Harbour. |
| 31 |
(30) Colony an unbranched stem with a distinct chitinous perisarc, and rooted by a true hydrorhiza; hydranths large, distal tentacles in two whorls; gonophore producing free medusæ only. F. Hybocodonidæ. Stem with distinct annulate expansion just below the hydranth, distal tentacle whorls closely approximated; gonophores attached to hydranths without stalks and
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Plate III |
| 32 |
(29) Hydranths with whorls of two different types of tentacles. |
| 33 |
(34) Hydranths with scattered distal capitate tentacles usually in a series of whorls, and with a whorl of proximal filiform tentacles; gonophores producing free medusæ. F. Pennaridæ. Colony large, much branched, often with distinct pinnate or twice pinnate arrangement; hydranths with large proboscis, well supplied with whorls of capitate tentacles; gonophores on hydranth body just above proximal tentacles; medusæ often mature when liberated. G. Pennaria. Stem with regular alternating ascending pinnæ. stem slightly ringed above the origin of the pinnæ; pinnæ with a few spiral turns at the base, smooth throughout the rest of their length; hydranths with 7 to 12 distal filiform tentacles, and 9 to 14 capitate (4 usually about the proboscis). Pennaria australis Bale (P. Rosea Von Lendenfeld). Figs. 14, 21. Intertidal; Auckland Harbour. |
| 34 |
(33) Hydranths with one or more whorls of distal capitate tentacles and a proximal whorl of stiff falsely filiform tentacles, probably tactile in function; gonophores produce free medusæ. F. Staurididæ. Stems giving rise to a single hydranth with conical proboscis, single whorl of capitate and false tentacles; medusæ formed between capitate and false tentacles; G. Staurocladia. Capitate tentacles 3 in number, and 6 stiff false tentacles; 1 or 2 medusæ buds formed on body of hydranth at one time; medusæ liberated with 6 bifurcated tentacles and 6 (indistinct) radial canals; upper branch of tentacles carries single nematocyst cluster. Staurocladia hodgsoni (Browne). Fig. 16. Intertidal; Island Bay, Wellington. |
The Medusæ of the Athecate Hydroids
The first thing that will be noticed in the key which follows, is that the determination of the family is rather different from that of the hydroids. This is because the hydroids and medusæ are usually treated as separate entities, and there is no common or single key to the hydroids and medusæ of either the Athecate or Thecate groups. Just to add to the difficulties, very similar medusæ are budded off from quite different hydroids, and vice versa. Because of these difficulties the medusa generation may bear a different name from its hydroid, e.g. the medusa of the hydroid genus Syncoryne is referred to in the literature under the generic name of Sarsia.
A typical medusa from an Athecate hydroid (Fig. 18) resembles in form a deep bowl, and this is termed the bell or umbrella. The outer surface of the bell is called the exumbrella or aboral surface, and the inner concave side the sub-umbrella or adoral surface. The mouth of the medusa page 71 is carried on a protuberance (manubrium) pendant from the sub-umbrella surface. The manubrium leads into a stomach or gaster in the central region of the bell. From the gaster run radial canals. These join with a canal that encircles the margin of the bell (circular canal). Tentacles of various form are found on the bell margin. Sense organs in the form of eye spots (ocelli) may be present on the tentacle bases or the bell margin. A circular shelf of tissue (velum) projects inwards from the bell margin. The velum assists in swimming movements as it contains a highly developed muscle band. The gonads are borne on the manubrium. The terms used above are also applicable to medusæ budded from Thecate hydroids, but the latter differ in having a much shallower bell, sense organs that are balancing in function (statocysts) and gonads borne on the radial canals.
Technique
Inevitably a certain amount of distortion of delicate tissues takes place, even with very careful manipulation, during killing and fixing, so where possible full notes should be taken of shape, colour, etc., before preservation is attempted. Again, as with the hydroid, it is desirable to narcotise the medusa so that it can be killed and fixed in an expanded condition. Place the medusa in a beaker of fresh sea-water and leave to expand. Narcotise with 50% alcohol or magnesium chloride in sea-water. Add a few cc. at a time with a pipette. Keep the water in motion with a glass rod. (Sometimes the gentle bubbling of coal gas through the water acts as a good narcotic.) When narcotised, add a 5% solution of formalin in sea-water, still keeping the water in motion. For storage, increase the strength of the formalin to about 10%. Most medusæ are satisfactorily narcotised, fixed and preserved by this method. A degree of patience is needed, however, as some medusæ take several hours to narcotise. Under certain field conditions narcotisation may be impracticable and a fairly good kill and fix can be obtained by simply adding the 5% formalin solution to the water containing the medusa. Medusæ also stain well with acetic-acid-alum carmine if permanent whole mounts of small forms are desired.
It has not been possible in all cases to draw the figures from specimens. Figures have been re-drawn as follows: Figs. 8, Rees and Russell; 17 and 19, Kaberry (unpublished thesis); 21, Von Lendenfeld; 22, 24 and 25, Mayer; 23, Dendy.
A basic reference for medusæ is ‘The Medusæ of the World’ (three volumes) by Alfred G. Mayer, Carnegie Institute, Washington, 1910.
Key to the Medusæ of the Athecate Hydroids
| 1 |
(4) Marginal tentacles branching dichotomously or complexly, upper branches bearing nematocyst batteries and the lower branch or branches no nematocyst batteries but a suctorial disc at the distal end. Gonads ring-like, or segregated on the inter-radial and adradial sides of the manubrium. F. Cladonemidæ. |
| 2 |
(3) Medusæ adapted for crawling or walking; no oral tentacles; gonads page 72 well developed in inter-radial pockets round the stomach; radial canals usually 6; tentacles numerous, and give rise to a single sucker-bearing and single nematocyst-bearing branch; tentacles increasing in number with age and not corresponding to the number of radial canals, upper branch with several clusters of nematocysts in addition to the terminal cluster; thick nematocyst ring under bell margin. G. Staurocladia. Bell shallow saucer shape, wider than it is high, diameter 1.6 to 3.0 mm.; 6 radial canals in juveniles and in medusæ possessing gonad pouches, oldest medusæ with up to 8 radial canals some of which may be branched; tentacles up to 32 in number, with nematocyst clusters on lateral sides of upper branch of tentacle and about 8 in number; 6 gonad pouches. Staurocladia hodgsoni (Browne). Intertidal rock pools among seaweed (Ceramium), Island Bay, Wellington. |
| 3 |
(2) Medusæ adapted for crawling or walking; 4 to 6 oral tentacles terminating in nematocyst knobs; mature gonad forms protrusions round the manubrium; 4 or 5 or more bifurcated radial canals, or 8 to 10 or more simple canals or with some bifurcated and some simple: tentacles give rise to sucker-bearing or nematocyst-bearing branches or both: approximately the same number of tentacles as radial canals; no nematocyst ring under bell margin. G. Cladonema. Bell rounded in form, diameter 2-3 mm.; manubrium long and mobile with 6 short oral tentacles each with prominent nematocyst head: radial canals usually 9, some of which may be branched; tentacles usually 9; 5 to 6 stinging branches of approximately equal length and 3 to 5 sucker-bearing branches; gonad, 6 rounded protuberances on manubrium approximately mid-way between mouth and gaster. Cladonema novæ-zelandiæ n. sp.* Fig. 20. Rock pools, Island Bay, Wellington. Differs from C. californica Hyman to which it is most nearly related in having up to 4 more stinging branches and 2 more sucker-bearing branches. Hydroids of both species unknown. |
| 4 |
(1) Marginal tentacles not branched. |
| 5 |
(14) No oral tentacles or oral lips. |
| 6 |
(7) Marginal tentacles in four clusters radial in position; gonad ring-like, encircles stomach; 4 unbranched radial canals. F. Margelopsidæ. Five
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Plate IV |
| 7 |
(6) Tentacles separate, not in clusters; gonad ring-like encircling the manubrium; 4 to 6 simple unbranched radial canals; ocelli, when present, on the outer sides of the tentacle bulbs. F. Codonidæ. |
| 8 |
(13) Tentacles well developed. |
| 9 |
(12) Four tentacles of equal length in the radial position. |
| 10 |
(11) Four long, simple, equally developed tentacles; manubrium tubular; ocelli present on each tentacle bulb. G. Sarsia. Bell oval, with thick walls; 4 tentacles with large basal bulbs and eye spots; gonads encircle manubrium from gaster to mouth. Sarsia eximia Boehm. Fig. 24. Oamaru Harbour. |
| 11 |
(10) Four equally developed tentacles, about half the diameter of the bell at the time of liberation and each with a distinct cap; no ocelli. G. Endocrypta. Bell, nearly globular in shape, with extensive velum; manubrium may reach to the opening of bell or beyond, and is greater in diameter at base than at extremity; umbrella extensively pitted; gonads not observed. Endocrypta huntsmani (Fraser). Fig. 4. None so far observed free from branchial cavity of tunicate in which parent colony lives. |
| 12 |
(9) Tentacles not of equal length; bell asymmetrical; 1 to 3 long tentacles at foot of the long radial canal and 3 small or rudimentary, 1 each at base of other radial canals. G. Hybocodon. Four radial canals and 5 superficial orange-coloured meridional bands; 1 to 3 long tentacles that may bud other medusæ from the base, and these in turn may bear other medusæ; 3 rudimentary tentacles mere basal bulbs. Hybocodon prolifer (Nutting). Fig. 22. Known only from hydroid. |
| 13 |
(8) Tentacles rudimentary; 4 permanently rudimentary tentacles which are reduced to mere basal bulbs. G. Pennaria. Bell, slender, oval; 4 large rudimentary tentacle bulbs with a minute external ocellus upon each; manubrium with sperm or ova fills the entire cavity of the sub-umbrella; ova discharged after medusæ set free. Pennaria australis Bale. Fig. 22. Known only from hydroid. |
| 14 |
(5) Mouth with oral lips or oral tentacles or both. |
| 15 |
(18) Oral lips present, but no oral tentacles; 4 unbranched radial canals; tentacles hollow; ocelli on outside of tentacle bulbs when present. F. Pandeidæ. |
| 16 |
(17) Two well-developed and many rudimentary tentacles; external surfaces of the adradial gonads thrown into folds. G. Stomotoca. Bell, deep hemisphere, with relatively straight sides, solid apical projection, 2 long marginal tentacles, and 14 small rudimentary tentacles; manubrium four-sided; 4 recurved oral lips; stomach wall folded and ridged; gonads on wall of page 75 stomach. Stomotoca rugosa (Mayer). Fig. 17. Cook Strait. Hydroid not known for N.Z. |
| 17 |
(16) Four or more tentacles; 4 inter-radial, horseshoe-shaped gonads on the stomach wall, composed of more or less fused ridges or network-like swellings; completely separated in the 4 principal radii. G. Neoturris. Bell with large solid apical projection of variable shape; 16 well-developed tentacles with quite large basal bulbs flattened in a radial direction; abaxial ocellus on each bulb; also when fully grown, 48 very short rudimentary tentacles arising at a lower level on the bell margin than the long tentacles; 4 radial canals with funnel-like openings into the stomach; no stalk on the manubrium; 4 prominent crenulated oral lips; 4 gonads with outer surface thrown into complex folds. Neoturris vesicaria A. Agassiz.* Fig. 19. Hydroid unknown. Cook Strait. |
| 18 |
(15) Oral lips present and oral tentacles or nematocyst knobs on the lips; 4 unbranched radial canals; tentacles solid; ocelli when present on the inner side of the tentacle. F. Margelinæ. |
| 19 |
(20) Eight or more filiform marginal tentacles; walls of radial canals above stomach formed of vacuolated cells forming a stalk-like base for the stomach; oral lips with row of nematocyst-bearing knobs; ocelli present at tentacle bases. G. Turritopsis. Bell, slightly pear-shaped; 40 to 70 simple marginal tentacles; 4 masses of vacuolated cells at base of manubrium; gonads developed on the side of stomach. Turritopsis nutricula McCrady. Fig. 18. Wellington Harbour and Cook Strait. |
| 20 |
(19) Marginal tentacles filiform, grouped in 4 radial clusters; walls of radial canals not vacuolated; oral tentacles present and dichotomously branched at some distance above the mouth rim and with terminal clusters of nematocysts; ocelli present at tentacle bases. G. Bougainvillia. Bell, high, dome-shape; 4 marginal bulbs with 16 to 20 tentacles; manubrium 4-sided, urn-shaped; oral tentacles branched dichotomously 6 to 7 times; gonads 8. Bougainvillia ramosa Van Beneden. Fig. 25. Known only from hydroid. |
Acknowledgments
My thanks are due especially to the managers of the Musgrave Fund. Cambridge University, England, for their generous grant for expenses incurred in collecting material; also The Dominion Museum, Wellington; The Canterbury Museum, Christchurch; Professor L. R. Richardson, Victoria University College; Dr. E. J. Batham, Marine Biological Station, Portobello; Mr. George Knox, Canterbury University College, Christchurch; Mr. C. Kaberry, Marine Department, Wellington; and others of my colleagues and students who have from time to time sent me interesting hydroids and medusæ; also to Dr. W. J. Rees, British Museum (Natural History), for advice on the status of the genus Stomotoca.
* Fisrt record of species for New Zealand.