land nemertines of new zealand

2001. J. Linn. SOC., 52: 293-313. With 1 5 figures

June 1973

Land nemertines of New Zealand JANET MOORE

Zoology Department, Downing Street, Cambridge

Accepted for publication July 1972

A full description and comparison of the two land nemertines already reported from New Zealand, Geonemertes novaezealandiae and G. pantini. is followed by the description of G. allisonae sp. nov., whose relationship to the other two species is defined.

The New Zealand upper littoral nemertine Acteonemertes bafhamae is compared to these species of Geonemertes, and its occurrence recorded as a terrestrial nemertine on the Auckland Islands. The relationships and evolution of land nemertines are discussed.

Introduction . . . . . . . . . Methods . . . . . . . . . . Geonemertes novaezealandiae and G. pantini Geonemertes allisonae sp. nov. . . . . Acteonemertes bathamae . . . . . Darbishire’s species . . , . . , . Discussion . . . . . . . . . Acknowledgements . . . . . . . References . . . . . . . . . .

CONTENTS

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INTRODUCTION

A review of the genus Geonemertes by the late Professor C. F. A. Pantin was published posthumously by the British Museum of Natural History (Pantin, 1969). The land nemertines of New Zealand proved to be particularly interesting, but he was only able to make a preliminary study of them (described by the present author in an appendix to “The Genus Geone- rnertes”). The following account is an extension of that study, based on specimens collected by or sent to Professor Pantin but which he was never able to examine histologically.

METHODS

Most of the specimens were collected by Professor Pantin, Dr E. J . Batham of Portobello Marine Biological Station, New Zealand or Dr P. M. Johns of the University of Canterbury, New Zealand. These specimens were fixed by the methods devised by Pantin (1969) to minimize shrinkage and to preserve in particular details of the circulatory and excretory systems: after narcotization

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294 JANET MOORE

in 7% ethyl alcohol until movement almost stopped, the worms were fixed either in Susa (followed by 96% alcohol with iodine, absolute alcohol and methyl benzoate or liquid paraffin) or in 80% alcohol.

The specimens were subsequently sectioned at 8 Pm and stained in Mallory's trichrome, by Mr D. J . Buck of the Department of Zoology, Cambridge.

GEONEMERTES NOVAEZEALANDIAE AND G . PANTI"

Two species of New Zealand land nemertines have already been described: G. novaezealandiae Dendy (Dendy, 1894, 1895) and G. pantini Southgate (Southgate, 1954). All but three of the present specimens of Geonemertes belong to these two species.

Locati ties

Figure 1 shows that the localities from which specimens have been obtained are widely distributed in New Zealand. The two species occur in similar habitats but have never been found together in the same locality. Since the animals are cryptozoic and difficult to find, negative results are not necessarily significant.

Figure 1 . The distribution of Geonernerres species in New Zealand. 0 , G. novoezeolondioe; 0 ,

G. pontini; ,G. al~isonoe.

LAND NEMERTINES OF NEW ZEALAND 295

Details of localities are as follows:

G. novaezealandiae South Island (a) Toitoi, Fortrose, nr. Invercargill, Southland, N.Z. A deserted farmhouse 3

miles south of Waimahaka on the road to Fortrose. This is a Type locality (Dendy, 1895). Dr Pantin found specimens there in 1954, but in 1961 the place was fcund to be unfenced and ruined by sheep.

(b) Mount Somers, nr. Ashburton, Canterbury, N.Z. In decomposing timber near the edge of Alford Forest at the foot of Mount Somers. Type locality (Dendy, 1895). Dr P. M. Johns and Dr Pantin, August 1961.

(c) Tokanui, nr. Invercargill, Southland. A wood 1% miles S.E. of Tokanui station; a small patch of bush in the slopes of a hill; specimens were in crevices and hollows in rotten trunks of tree ferns (Dr Pantin, Dr H. M. Pantin, Dr E. J . Batham and Mr A. J . Southgate, August 1961).

North Island (d) Stokes Valley, nr. Wellington (Dr B. Holloway, August 1952). (e) Mount Egmont (Dr P. M. Johns, July 1964). (f) Piha Gorge, Auckland (Dr Johns, July 1964). (g) Near Lake Waikaremoana (Dr Johns, 1961). (h) Napier area, near beach at Waipataki (Dr Johns, 1961).

0 ther Islands Ocean Island (off Auckland Island) in coastal Rata forest (Dr Johns, 1962).

Specimens from D’Urville Island at Greville Harbour (grid reference 137 : 855, Dr V. Stout, August 1960) probably belong to this species but certain identification is not possible.

G pantini South Island (a) Signal Hill, Dunedin, N.Z. Tjipe locality (Southgate, 1954). Many

specimens subsequently found by Mr Southgate, Dr Batham and Dr Pantin. (b) Leith Valley, nr. Dunedin (Dr Pantin, 1954). (c) Thornhill Farm, Mataura (Dr Pantin, July 1961). (d) Cass, Canterbury in Nothotugus forest (Dr R. Pilgrim, October 1961 ). (e) Minchin Pass, Arthur’s Pass, National Park, subalpine (Dr Johns, 1961). ( f ) Lewis Pass, 5000 f t , subalpine (Dr Johns, 1961). (g) Yaparoa Range, nr. Westport, 4000 f t (Dr Johns, 1961). ( h ) Hapuku, nr. Kaikoura, in coastal Ngaio forest (Dr Johns, 1961).

North Island (a) Erua, nr. Ruapehu, 2500 ft , in very wet rotten beech log (Dr Johns). (b) Mount Kahu, Hauhungaroa Range, nr. L. Taupo, in leaf mould (Dr Johns). (c) Mangawhoio, nr. Waitotara, nr. Wanganui (Dr Johns, January 1958). (d) Coroglen, Coromandel (Dr Johns, July 1964).

0 ther Islands Stewart Island, Easy Cove (Dell and Holloway, January 1955).

Differences between the two species

G. novaezealandiae and G. pantini differ in colour pattern, due to differences in the nature of the brown pigments and in the pattern of the stripes. Pantin’s

296 JANET MOORE

examination of three specimens of each species showed that the two are internally alike (in those characters found to be significant in classifying land nemertines) except that G. pantini possesses an accessory lateral nerve and G. novaezealandiae does not, a surprisingly major difference between species otherwise so similar (Pantin, 1969, appendix).

Sixteen specimens of G. novaezealandiae and 20 specimens of G. pantini have now been examined to assess the constancy of distinctions between the two species and the extent of variation within each. Examination of these specimens confirms the previous findings and establishes other minor differences between the two species.

Number of stripes G. novaezealandiae has four dark brown dorsal bands on a cream

background, the two more lateral stripes being thinner than the two more dorsal ones. G. pantini has two rich brown stripes of a different pigment (Pantin, 1969, Frontispiece). However in 5 of the 20 G. pantini the stripes divide, for part or all of their length, so that the animals appear to have four stripes and may therefore be confused with G. novaezealandiae.

Accessory lateral nerve This structure (Fig. 2) is present in all specimens of G. pantini but absent

from all specimens of G. novaezealandiae. The main lateral nerve in all nemertines is formed by backward extension of the ventral cerebral ganglionic lobe. Where there is an accessory lateral nerve, a tract of fibres arises from the median surface of the dorsal ganglionic lobe, crosses to leave it laterally and becomes incorporated on the dorsal side of the main lateral nerve as a distinct bundle of fibres (Fig. 2).

/ Accessory lateral nerve

A El C D

50 urn

Figure 2. T.S. lateral nerves (at the level of anterior gut diverticula, on the left side). A. G. novaezealandiae: no accessory lateral nerve. B. G. pantini, length 25 mm, with large accessory lateral nerve. C. G. pantini. length 32 mm, with small accessory lateral nerve. D. G. pantini with accessory lateral nerve detached.


In G. novaeaealandiae there is no contribution from the dorsal ganglion to the lateral nerve. In G. pantini the accessory lateral nerve arises from the dorsal ganglion as described, but its course is then variable. In 8 of the 20 specimens it does not immediately become incorporated in the bundle of the lateral nerve, but travels back separately on either side for up to 300 pm before joining the main nerve. Particularly in these specimens, the accessory lateral nerve may again become detached at intervals along its course, for distances up to 400 pm at a time, on one or both sides (Fig. 2D). The relative size of the accessory lateral nerve varies considerably in different specimens and is unrelated to the size of the worm (Fig. 2B, worm 25 mm long: Fig. 2C, worm 32 mm long). Both sections drawn are at the level of the first appearance of the anterior gut diverticula: the accessory lateral nerve becomes smaller as it passes posteriorly and disappears in the most posterior region.

Vascular plugs Both species have two circular rhynchocoelic plugs, one on each of the

anterior branches from the dorsal blood vessel: as in some other land nemertines, this forking of the vessel occurs just behind the ventral cerebral commissure and each branch enters the rhynchocoelic sheath. At this point the blood is separated from the rhynchocoelic fluid only by this tissue plug (Fig. 3 ) .

In G. pantini plugs are smaller (c. 40pm) than in G. novaezealundiae (c. 65 pm in diameter). There is no relationship between worm and plug sizes, in either species.

Figure 3B shows the vascular plugs of G. pantini with the proboscis retracted, Fig. 3A shows G. pantini with the proboscis extruded and the plugs prominent in the empty rhynchocoel, Fig. 3C shows the larger plugs of G. novaezealundiae (proboscis retracted).

Anterior gut diverticula The anterior gut caecum (see below) ends blindly as two anterior diverticula

(20-300 pm long) which reach forward almost to the brain. Their position constitutes another difference between the two species: they are ventral to the stomach in 12 specimens of G. novuezealundiae (Fig. 4A) but more dorsally situated and lateral to the stomach in 16 specimens of G. puntini (Fig. 4B). This condition however is not invariable as two specimens of G. novaezealandiue and three of G. pantini entirely lack anterior diverticula and the caecum ends abruptly, midventrally (as shown in Fig. 6).

Resemblances between the two species The two species are alike in their remaining characters (see Pantin, 1961a,

The epidermis is ciliated and glandular. Dermis. The underlying connective tissue is a thin basement membrane

rather than the thick dermis found in many species of Geonemertes. The body wall musculature is well developed with many strands of

longitudinal muscle, especially ventrally. In larger specimens of both species this muscle is separated into well defined bundles.

1969, for a more complete account of geonemertine morphology).

298 JANET MOORE

Blood vessel I

C

Figure 3 . T.S. vascular plugs. A. G. pantini with proboscis extruded and plugs standing up in empty rhynchocoel. B. G. pantini with proboscis (not shown) in rhynchocoel. C. G . novaezealandiae, larger plugs, with proboscis in rhynchocoel.

The parenchyma is extensive in most regions. The gut (as in other land nemertines) opens from the rhynchodaeum as a

thin-walled unciliated oesophagus with a few acidophilic gland cells. This widens into a ciliated and glandular stomach (200-1500 I.tm long) with deeply folded strongly basophilic walls. There is great variation in the length of the oesophagus, and consequent position of the stomach. The oesophagus may extend posteriorly to the brain, or the stomach may be pushed right up to the mouth (most commonly the oesophagus widens into the stomach at the level of the ventral cerebral commissure). In beautifully fixed specimens it seems unlikely that these differences are artefacts, and they would be unusual individual variations. Possibly this stomach movement, with contraction of the oesophagus, occurs during feeding.

Posteriorly the stomach narrows into a dorsoventrally flattened pylorus (up to 2000pm long) which opens into the dorsal surface of the intestine. From this point the intestine continues posteriorly (with paired lateral diverticula) to


Cephalic

Rhvnchocoel EDidermis

gland

I A 500 ,urn

Epidermis \

nerve

I 2 5 0 p m

,

Figure 4. T.S. anterior gut diverticula ventral to stomach in A (G. novaezeulundiue) and lateral to stomach in B (G. pantini).

the anus, and a large caecum runs anteriorly, ventral t o the pylorus, ending in the anterior gut diverticula described above.

The 'rhynchocoel separates from the rhynchodaeum at the level of the eyes and extends posteriorly the full length of the body. The sheath muscle is in the form of wickerwork, as in most other Geonemertes species.

The proboscis is large (a characteristic of land nemertines) and typical of the group in structure, as described for example by Dendy (1892) for G. austru- liensis. I t has 12-21 nerves in G. pantini (17 specimens) and 12-17 in

300 JANET MOORE

G. novaezealandiae (9 specimens). There are 2-4 accessory stylet sacs. The numbers of proboscis nerves and stylet sacs are characters which tend to be very variable in land nemertines.

No frontal organ is present. The cephalic gland extends from the anterior tip of the worm to the

beginning of the ventral gut caecum. It is very well developed around and just behind the brain, where it occupies most of the parenchyma (Fig. 4). As in other land nemertines which lack a frontal organ, the cephalic gland has many improvised openings (around the eyes and elsewhere in the anterior end). The “dorsal gland cells” prominent in Australian Geonemertes species are not found in these New Zealand forms.

The cerebral organs open ventrally into a transverse ciliated groove. The opening most commonly occurs just behind the eyes, where the oesophagus separates from the rhynchodaeum, and the cerebral organ extends posteriorly for some 200-300 pm.

However in one of the specimens of G. novaezealandiae and in three of the specimens of G. pantini the cerebral organ is altogether more posterior; the anterior opening is then beside the ventral commissure and the organ extends backwards as much as 400 pm behind the end of the brain. These specimens are characteristic of their species in every other respect, which suggests that the position of the cerebral organs should not by itself be given great systematic importance.

The opening leads into a ciliated cerebral canal which forks so that the anterior branch ends in a thin-walled sac and the posterior, more median branch is surrounded by a mass of nerve ganglion cells and ends blindly in a posterior glandular region (Fig. 15) . The ganglionic and glandular regions are approximately equal in size, There is a large nerve tract from the ganglionic region to the brain, and the posterior gland extends backward in a ventrolateral position as in G. australiensis (figures in Pantin, 1969).

Eyes. Four eyes are present in all specimens. The anterior eyes are larger and more lateral, the posterior eyes smaller and more dorsal. The eye multiplication occurring in Australian Geonemertes does not occur in these New Zealand species.

The nervous system is characteristic of hoplonemertines and is similar in both species, except for the occurrence of the accessory lateral nerve in G. pantini, described above.

The vascular system is as described for Australian Geonemertes (Pantin, 1969). There are paired longitudinal lateral vessels and a single mid-dorsal vessel. Throughout the body there is a subdermal capillary network, with characteristic valves at frequent intervals. This network forms cross connections between the three main vessels, and anteriorly repIaces a cephalic vascular loop: the two lateral vessels and the plug-bearing branches of the dorsal blood vessel (described above) originate anteriorly from the capillary network.

The excretory system is also as described for Australian Geonemertes. There are many flame cells scattered throughout the body in the subdermal layer. They are uninucleate and paired, without transverse bars. The excretory ducts branch throughout the parenchyma, opening at several thousand excretory pores. The final region of the excretory ducts is a highly specialized glandular duct, thick-walled with radial striations in the cytoplasm (figures in Pantin, 1969).


Gonads. Here it is uncertain whether the two species are similar. Of the 20 specimens of G. pantini examined, the two smallest (4 mm and 6 mm long) had no gonads. The nine which were between 10 and 20 mm long were immature females (either the gonoducts had not opened to the exterior or the oocytes had not yet developed among the yolk. I am grateful to Dr V. V. Hickman for checking this point for me). The nine specimens which ranged from 25 to 75 mm long were fully mature females. None was hermaphrodite. No male, therefore, has ever been found. This applies also to G. chalicophora (Moore & Moore, 1972). Since the 11 smaller specimens have no trace of male gonads, the present evidence suggests that G. pantini is not a protandrous hermaphrodite like G. dendyi: but probably has separate sexes like G. australiensis (Hickman, 1963).

In G. novaezealandiae one male has been found: a large specimen, 50 mm long. Of the remaining 15 specimens, one small one lacked gonads and 14 (lengths 17 to 57 mm) were female, 12 of which were fully mature. This species therefore appears to have separate sexes.

In both species, the ovaries are placed laterally or ventrolaterally between the intestinal diverticula, as is characteristic of hoplonemertines. They do not occur anterior to the pyloric region but are very numerous in the rest of the body.

The comparison of the two species is summarized in Table 1.

GEONEMERTES ALLISONAE SP. NOV.

Lo Cali t y A small land nemertine was found in open bush near Menzies Bay, Banks

Peninsula, by Mrs F. R. Allison of the University of Canterbury, Christchurch. Banks Peninsula (see Fig. 1) is separated from the mainland by a basin of alluvial clay and may formerly have been isolated from the rest of South Island. It contains a number of endemic invertebrate species (Johns, 1964, 1966).

Methods

The following account is based on three specimens obtained from Menzies Bay by Mrs Allison and Dr Pantin in 1961. They were fixed and stored in 80% alcohol. In 1968 they were sectioned by Mr D. J . Buck of the Cambridge Zoology Department and stained in Mallory’s trichrome.

Difference f r o m G . novaezealandiae

An accessory lateral nerve is present (Fig. 9 ) . This nerve arises in the usual way, is relatively large in all three specimens and detaches from the lateral nerve for part of its length in one specimen. This character distinguishes the specimens from G. novaezealandiae and allies them to G. pantini.

Differences f r o m both G . novaezealandiae and G . pantini

Colour pattern. There are no pigment stripes. The dorsal surface is mottled brown, with a clear stripe over the proboscis (Fig. 5 ) . The nature of the

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302 JANET MOORE

pigment is not known, but it does not persist in ethyl alcohol. Specimens of G. pantini retain their pigment in alcohol and even the smallest have two distinct brown stripes.

Number of eyes. Only two eyes are present (Fig. 5 ) . They are relatively large and laterally placed, like the anterior pair of eyes in the other species (even the smallest individuals of which have four eyes).

Figure 5 . G. ullisome, dorsal view of anterior end.

Size at maturity. The three specimens are all 10 mm long, 0.5-1 mm wide, yet all three are mature females (Fig. 10). The other two species are immature at this size: the smallest mature females of G. pantini were 25 mm long.

Cephalic vascular loop. The blood vessels at the anterior end do not form a network but a simple cephalic loop: the two anterior branches of the dorsal blood vessel enter the rhynchocoel and give off the vascular plugs as in the other species, but then pass anteriorly and dorsally to meet in a cephalic loop above the rhynchocoel, just posterior to the oesophageal/rhynchodaeal separation (Fig. 7).

Anterior caecal diverticula are lacking in all three specimens: the caecum (300-450 pm long) ends blindly behind the brain (Fig. 9 ) . This condition is however shared by a few specimens of the other two species, as reported above.

(In one of the present specimens the stomach has been pushed anteriorly into the oesophageal region (Fig. 7). This may suggest the feeding method of the animal, or may be an artefact, just as in the other two species.)

LAND NEMERTINES OF NEW ZEALAND 3 0 3

Resemblances to the other two species

In all other characters the present three specimens resemble both G. pantifti and G. nouaezealandiae, with only minor differences (number of proboscis nerves and size of vascular plugs).

The general anatomy and relative size of components is shown in the three transverse sections, Figs 7, 8 and 9 , taken from one specimen. Figure 6 is a diagrammatic guide to Figs 7 to 9.

Dorsal cerebral commissure

Proboscis 1 Rhynchocoel

Oesop

Figure 6. G. atlisome, diagram to show position of T.S. in Figs 7 , 8 and 9 .

Port of cephalic

w l t h cephalic gland

C ere brol ! Ganglionic region Orgon

Figure 7. T.S. G. ollisome at level of foreguthhynchocoel separation, showing cerebral organs (right of diagram at a more anterior level than left of diagram).

304 JANET MOORE

Figure 8. T.S. C. allisorure just posterior to the ventral cerebral commissure, showing vascular plugs.

I I 250pm

Figure 9 . T.S. G. ullimnue at the anterior end of the caecum, showing accessory lateral nerve.

The proboscis has 10, 10 and 12 nerves in the three specimens (12-21 recorded for G. pantini and 12-17 for G. novaezealandiae). There are two or three stylet sacs. In the structure of its three main regions and in the main stylet apparatus the proboscis does not differ from other species of Geonemertes.


The cephalic gland is extensive (especially just behind the brain) as described for the other species, with many outlets and no frontal organ. I t occupies most of the parenchyma space shown in Figs 7, 8 and even as posteriorly as Fig. 9 .

The cerebral organ extends from eye level to about the level of the ventral brain commissure. I t is 2 0 0 p m long, i.e. no smaller than that of the larger species. I t has the same components (Fig. 7): the ventrally opening ciliated cerebral canal branches to enter the dorsal anterior sac and the more posterior ganglionic mass, this second branch ending blindly in the posterior gland which is ventro-lateral to the brain (description as for G. novaezealandiae and G. pantini, Fig. 15).

The vascular system includes two rhynchocoelic plugs (Fig. 8) which are 20-25 pm in diameter i.e. even smaller than in G. pantini (41 pm). Apart from the cephalic vascular loop there is a subdermal network of capillary blood vessels, similar to that of the other two species but valves are less prominent (Fig. 10).

ibrone

Figure 10. L.S. G. allisome, posterior region, to show subdermal capillary network and ovary.

The excretory system (Fig. 11) has the specializations described in the other

Gonads. As for G. pantini, only females have been found. Table 1 includes a comparison of G. allisonae with the other two species of

two species.

Geonemertes in New Zealand.

Types The three specimens are named as a syntypic series. With the rest of Dr

Pantin’s collection of land nemertines, they are to be deposited at the British Museum of Natural History in the Pantin Collection.

306 JANET MOORE

Calcareous- particle

Blood - vessel

Figure 11. L.S. C. allisonoe to show excretory ducts and flame cells

ACTEONEMER TES BA THAMAE

Occurrence Acteonemertes bathamae is an upper littoral nemertine first found on the

Portobello Peninsula (Pantin, 1961b). It resembles the New Zealand species of Geonemertes in many characters but is clearly differentiated from them (see below) and is fundamentally marine.

Material collected from the subantarctic Auckland Island, New Zealand reveals a wider range of habitat for this species. Supra-littoral nemertines were collected from the main Auckland island (Tucker Point and Ranui Cove, 6 f t above high water) by Dr P. M. Johns in 1963. These, like Portobello A. ba thamae, were cream-coloured with two dark brown dorsal stripes starting behind the head. Histological examination of six of these specimens showed them to be identical to A. bathamae in every respect. Three nemertines collected from Auckland Island and Ocean island by Mr W . H. Dawbin in 1943 were however entirely terrestrial, being found under small logs at the edge of the scrub remnant at an altitude of about 100 feet. While this is still in reach of


sea spray on these islands, the habitat was sheltered and associated fauna included spiders and millipedes. These specimens were uniformly Iight grey in colour, but histological examination showed them to be identical to A. bathamae in every other respect.

Here is clear evidence of an upper littoral nemertine colonizing the land, on remote islands, without structural change.

Differences from N. Z. Geonemertes

Specimens of A. bathamae from these three habitats (Portobello upper littoral zone, Auckland Island supra-littoral zone and Auckland Island terrestrial region) share the following characters which distinguish them from New Zealand species of Geonemertes.

Nerve from dorsal ganglionic lobe. As in G. novaezealandiae, there is no accessory lateral nerve. Unlike any Geonemertes species which lacks this nerve, A. bathamae has a small contribution from the dorsal ganglion which passes outside the brain laterally and enters the dorsal surface of the lateral nerve (Fig. 12).

Lateral connecting

lobe

I O O p m

Figure 12. T.S. right cerebral ganglion of Acteonemerfes batbamae to show lateral fibre from dorsal to ventral lobe, just anterior to the origin of the lateral nerve from the ventral lobe.

The ventral cerebral commissure has two anterior projections which pass dorsally either side of the proboscis sheath (Fig. 13A). These are additional to the normal dorsal commissure connecting the two dorsal ganglionic lobes (Fig. 13B) and again constitute a distinctive feature not found in any species of Geonem er tes.

The cerebral organ is smaller and simpler. I t may be as long as in the Geonernertes species (200-400 pm) but the ganglionic region is very narrow and there is no anterior sac: the cerebral canal does not fork (see Fig. 14, contrast Fig. 1 5 ) . The cerebral canal is very variable in length: it may be up to 100 pm long, or it may be so short that the ganglionic region begins among the ventral

308 JANET MOORE

Proboscis sheath

Anterodorsol propction

I Ventral lobe

Figure 13. T.S. cerebral ganglia of A . bathamae. A. Anterior edge of ventral commissure showing anterodorsal projections (peculiar to this species). B. More posterior T.S. showing dorsal and ventral commissure (typical of nemertines).

epidermal cells (a condition not known from any other species). The anterior end of A. barhamae has particularly extensive parenchyma with many small blood vessels, and in transverse section the cerebral organ is unusually small in relation to the other body structures.

The position of the cerebral organ is (as in many geonemertines) variable. In the type specimen of A. barhamae it lies entirely in front of the brain, hence its original description (Pantin, 1961b) as “anterior”. In the paratype and in seven other specimens (from all three habitats) the cerebral organ lies between the posterior eyes and the ventral commissure. In two specimens it is very posterior, with the anterior opening at brain level and the organ itself extending behind the brain.

The excretory ducts lack the striking differentiation of a final glandular region which occurs in Australian and New Zealand species of Geonemerres and also in the related freshwater genus Potamonemertes (Moore & Gibson, 1973).

The stylet region of the proboscis has a very wide duct connecting the chambers of the anterior and posterior proboscis beside the main stylet basis.


Glondulor region

/

14 I Ventrol opening

IOOpm

Figures 14 and 15. 14. L.S. right cerebral organ of A. barhamae, anterior end to the right of the picture. 15. Oblique section of left cerebral organ of G. novaezealandiae, with ventral surface to the left of the picture.

Unlike the narrow duct (probably a poison duct) in this position in other hoplonemertines, it appears to be filled with acidophilic cellular material.

Resemblances to N. 2. Geonemertes

Specimens of A. bathamae resemble G. novaezealandiae and G. pantini in the other characters investigated.

Size. Fully mature specimens are 30-80 mm long. The largest specimens of G. novaezealandiae and G. pantini are 57 and 75 mm long, respectively.

Main body structures. The epidermis, dermis, body wall musculature, parenchyma, rhynchocoel, proboscis and gut all accord with the descriptions given above or in earlier accounts of Geonemertes.

Cephalic glands are strongly developed, extending from the anterior tip to behind the brain, with improvised openings in the absence of a frontal organ.

The cerebral organs open ventrally into a transverse groove, as is characteristic of Geonemertes (in marine and freshwater nemertines, and in G. agricola, the cerebral organs open laterally).

Eyes. There are four eyes, or the posterior pair may double to make six. Anterior gut diverticula are long (100-350 pm) and either ventro-lateral or

lateral in position. The vascular system includes two rhynchocoelic plugs of the same size and

kind as in G. novaezealandiae (c. 65 pm in diameter, in nine specimens where the plugs could be measured). There is a subdermal capillary network, much branched particularly in the anterior end, with prominent valves.

3 1 0 JANET MOORE

The excretory system consists of a very large number of paired simple flame cells situated in the subdermal layer, and the ducts are much branched throughout the length of the body with many excretory pores.

Gonads are as described for G. novazealandiae. The sexes appear to be separate: a few males have been found but no hermaphrodites, and there is no obvious correlation between sex and size.

Table 1 summarizes the comparison between the four land nemertine species occurring in the New Zealand region.

Table 1. Differences between the four land nemertine species occurring in the New Zealand region

Acteonemertes

ba rhamae

Habitat upper littoral

No. of stripes No. of eyes Size (mm) of mature 0 Whether d known Accessory lateral nerve Dorsal ganglion fibres

in main lateral nerve Diameter (pm) of

vascular plugs Anterior vascular network

replacing cephalic loop “Australian” excretory ducts Anterior gut diverticula ventrolateral

(VL) lateral (L) or absent (0) Cerebral organ large, with anterior

sac and forked cerebral canal Ventral commissure projections Stylet region with wide duct No. of proboscis nerves

(UL) or terrestrial (T) UL,T

2 4-6 30-80

0 +

+

65

++

0 VL,L

0

+ +

15-18

novaezealandiae

Geonemertes

pantini allisonae

T

4 4

17-57

0 0

65

+

t

+

0 0

12-17

T T

2(4) 0 4 2

25-75 10 0 0

0 0

41 25

+ +

+ 0

+ + L(0) 0

+ +

0 0 0 0

12-21 10.12

DARBISHIRE’S SPECIES

Land nemertines have once before been recorded from the Auckland Islands. Darbishire (1909) examined two fixed specimens, since lost. One, from the main Auckland Island, he named G. spirospermia. It had four eyes, dark dorsal stripes, spiral spermatozoa and no accessory lateral nerve (Darbishire’s “ganglionic strand” in this specimen and in the G. novaezealandiae which he examined referred to the normal dorsal nerve cell bodies in the lateral nerve). Apart from the spiral sperm, the specimen could be either A. bathamae or G. novaezealandiae. The other specimen, from Enderby Island, was examined externally only: it was pale cream with no eyes visible and he called it G. caeca. This again might be either the fully terrestrial unstriped form of A. bathamae, or G. novaezealandiue since specimens of this species lose their stripes in most common preservatives. Pantin (1969) states that “Nothing is known of G. caeca which would enable a new organism certainly to be identified as belonging to this species.”

LAND NEMERTINES O F NEW ZEALAND 3 1 1

In 1963, in addition to the A. bathavlzae described above, Dr Johns found G. novaezealandiae under logs in the Rata forest near the coast of Ocean Island, off Auckland Island. Since both these species occur here, the identity of Darbishire’s specimens must remain entirely uncertain.

DISCUSSION

The ‘genus ” Geonemertes Within the genus Geonemertes, groups of related species can be distin-

guished. The Australian group (G. australiensis, G. hillii and G dendyi) have in common certain specializations of the circulatory and excretory systems and the multiplication of eyes. The Pelaensis group (G. pelaensis, G. arboricola and G. rodericana) have different distinctive specializations of the circulatory and excretory systems and other characters. G. ugricola from Bermuda and G. nightingaleensis from Nightingale Island are closer to the ancestral marine condition in both structure and habitat, but they are not very alike: each combines an assortment of the specialized features of the Australian and Pelaensis groups. G. chalicophora, previously known only from European greenhouses, has recently been found in Madeira and the Azores (Moore & Moore, 1972). This species also is relatively unspecialized, but it is exclusively terrestrial and its assortment of characters does not ally it closely to G. agricola and G. nightingaleensis to make an “Atlantic” group. There are therefore two groups each containing three closely related species, and three separate species: no scheme of relationship can be constructed which does not require separate parallel evolution of one or more significant characters (for fuller discussion see Pantin, 1961a, 1969).

The conclusion remains that the present genus Geonemertes is probably an artificial assemblage of separate species or groups, each of which has evolved separately from marine or littoral ancestors. In this process there have been parallel but distinctive adaptations, in particular of the circulatory and excretory systems.

N e w Zealand Geonemertes

The land nemertines of New Zealand provide no evidence to contradict this view. The present paper establishes that G. novaezealandiae, G. pan tini and G . allisonae sp. nov. have sufficient characters in common to establish them as a New Zealand group within the “genus”. They most closely resemble the Australian group, having the same specializations of the circulatory system (two vascular plugs and a subdermal capillary network) and of the excretory system (in particular the thick glandular final region of the ducts). They differ from the Australian group in that the eyes are not multiplied, in the forking of the cerebral canal, in the absence of “dorsal gland cells” and in other minor features.

The transitional habitat

If nemertines have colonized the land several times during evolution, special interest attaches to forms such as Acteonemertes bathamae which are

312 JANET MOORE

transitional between littoral and terrestrial habitats. One such transitional form is G. agricola in Bermuda, which occurs intertidally (Crozier, 1917) as well as terrestrially. This species has many characters in common with the littoral nemertine Prosorhochmus claparedii, yet has flame cells with transverse bars remarkably parallel to those of the Pelaensis group (Pantin, 1969, Fig. 18). G. nightingaleensis on the southern Atlantic Nightingale Island is another relatively unspecialized form which is supralittoral as well as terrestrial (Brinkmann, 1947). Like G. agricola it can survive in seawater, while most species of Geonemertes can survive in freshwater but are quickly killed by seawater. G. nightingaleensis has some structural resemblances t o A. bathamae. In particular the cerebral organ is very similar in the two species (Fig. 14 and Pantin, 1969, Fig. 3 ) and unlike that of other Geonemertes. The excretory ducts of both species show a similar lack of specialization. G. nightingaleensis however differs from A. bathamae in colour pattern, in distribution of flame cells, in lacking the distinctive specializations of the cerebral ganglia and in having the marine type of “metameric” blood commissures rather than a specialized capillary network. The resemblance is probably only that of two species both transitional in habitat between the upper littoral region and the land. A. bathamae primarily resembles the New Zealand species of Geone- mertes (Table 1).

The habitat of A. bathamae is confined to the supralittoral region on the New Zealand mainland. On the remote Auckland Islands however it occurs both supralittorally and at an altitude of 100 feet on the land (while this may well be reached by sea spray, the associated fauna were fully terrestrial species). The distribution of A. bathamae may illustrate the course of evolution of land nemertines.

ACKNOWLEDGEMENTS

I am very grateful to the late Mrs A. M. Pantin, to Dr J. E. Smith and Dr J. P. Harding for the opportunity to work on the late Professor C. F. A. Pantin’s material. I should also like to thank Professor T. Weis-Fogh for facilities in the Cambridge Zoology Department, Dr D. A. Parry for much help the Science Research Council and the Darwin Fund of the Royal Society for financial support, Mr D. Buck for preparation of slides, Dr W. B. Amos for drawing the figures as he did also for “The genus Geonemertes”, and Dr Ray Gibson for much helpful discussion and for reading the manuscript.

This work was made possible by the kindness of those who found the specimens and gave them to Dr Pantin: in particular it is a pleasure to thank Dr E. J . Batham of Portobello Marine Station, Dr P. M. Johns of the University of Canterbury, Christchurch, and Mrs F. R. Allison of the same University. Many of the specimens were found in 1961 by Dr C. F. A. Pantin with Dr Henry Pantin, Dr Batham and Mr A. J. Southgate.

The Zoological Museum of the University of Oslo kindly lent me a type specimen of G. nigh tingaleensis for comparison.

LAND NEMERTINES OF NEW ZEALAND 3 1 3

REFERENCES

BRINKMANN, A.. Jr., 1947. A new Land Nemertean from the Tristan da Cunha Group, and a survey of the genus Geonemertes. Results Norw. scient. Exped. Tristan da Cunha 1937-8, 15: 1-24. Oslo: Jacob Dybwad.

CROZIER, W. J., 1917. Note on the habitat of Geonemertes agricola. Am. Nut.. 51: 758-760. DARBISHIRE, A. D., 1909. A description of two new species of land Nemerteans from the Auckland

Islands. Sub-antarctic islands of New Zealand, I , Article 28: 672-679. Wellington, N.Z.: John Mackay. DENDY, A., 1892. On an Australian Land Nemertine (Geonemertes australiensis n.sp.). Proc. R . SOC.

Vict., 4: 85-122. DENDY, A., 1894. Notes o n a New Zealand land nemertine. Trans. Proc. N.Z. Inst., 27: 191-194. DENDY, A., 1895. Note o n the discovery of living specimens of Geonemertes novuezealandiae. Trans.

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Dendy, with some account of its distribution, habits, variations and development. Pap. Proc. R . SOC. Tasm., 97: 63-75.

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JOHNS, P. M., 1966. The Cockroaches of New Zealand. Rec. Canterbury (N.Z.) Mus., 8: 93-1 36. MOORE, J . & GIBSON, R., 1973. A new genus of freshwater Hoplonemerteans from New Zealand. ZOO[.

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PANTIN, C. F. A., 1961a. Geonemertes: A Study in lsland Life. Proc. Linn. SOC. Lond., 172: 137-1 52. PANTIN, C. F. A,, 1961b. Acteonernertes bathamae, Gen. et Sp. Nov. An upper littoral nemertine from

PANTIN, C. F. A., 1969. The Genus Geonemertes. Bufl. Br. Mus. nor. Hist . (Zool.), 18: 263-310. SOUTHGATE, A. J . , 1954. Geonemertes pantini, a new land nemertine from the Dunedin district. Trans.

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