on a new genus of freshwater hoplonemertean from campbell island

Freshwat. Biol. 1972, Volume 2, pages 187-202

On a new genus of freshwater hoplonemerteanfrom Campbell Island

J A N E T M O O R E Department of Zoology^ University of Cambridge, andRAY GIBSON Department of Biology, Liverpool Polytechnic

Manuscript accepted 10 April 1972

SummaryA new freshwater hoplonemertean from Campbell Island, to the south of New Zealand,is described and named Campbellonemertes jolinsi gen. et sp. nov. The morphology ofthis tiemertean relates it with the family Prosorhochmidae and the occurrence of thisform, the second freshwater prosorhochmid genus from the Antipodes, stronglysupports an earlier hypothesis on the evolution of freshwater hoplonemerteans.

IntroductionNemerteans are predominantly marine invertebrates, but a few species have colonizedfreshwater, mixohaline or terrestrial environmetits. Two freshwater genera are atpresent known amongst the monostyliferous hoplonemerteans: Prostoma (Tetra-stemmatidae) with eight species (Gibson & Young, 1971) and the monotypic genusPotamonemertes (Prosorhochmidae) (Moore & Gibson, in press).

The present paper describes specimens of a new freshwater hoplonemertean from apond on Campbell Island, near Auckland Island to the south of New Zealand. Thespecimens possess a combination of characters which excludes them from any othercurrently recognized genus. In their general anatomy they are similar to the prosor-hochmid genera Geonemertes (Pantin, 1961a, 1969), Acteonemertes (Pantin, 1961b)and Potamonemertes (Moore & Gibson, in press), species of which occur in the NewZealand region. The present specimens are compared with these three genera, as wellas with the tetrastemmid genus Prostoma, and possible phylogenetic relationshipsare discussed.

The nemerteans are named Catnpbelhnemertes Joftnsi gen. et sp. nov., the specificname being in honour of the finder, Dr P. M. Johns of the University of Canterbury,Christchurch, New Zealand.

Material and methodsThe three specimens upon which this description is based were collected by Dr P.M. Johns in January 1961 from a pond near Tucker Cove, Perseverance Harbour,Campbell Island. The nemerteans were fixed in Bouin's fluid, preserved in 70%

Correspondence: Dr R. Gibson, Department of Biology, Liverpool Polytechnic, ByromSt., LiverpoolL3 3AF, England.

187

188 Janet Moore and Ray Gibson

alcohol and given to the late Professor C. F. A. Pantin in August 1961. Mr D. J.Buck of the Cambridge University Department of Zoology subsequently sectioned themat 8 /^m, and stained the sectiotis with Mallory's trichrome.

Appearance in life

The nemerteans were grey, with a single longitudinal mid-dorsal white stripe extendingthe full length of the body. When anaesthetized and relaxed straight, they measured'up to about 4 inches long' and appeared extremely attenuated.

AnatomyEpidermis

The body is covered by a ciliated epidermis composed of irregular, ovoid or attenuatedinterstitial cells, and comparatively few gland cells of the usual hoplonemertean types.Gland cells are distributed more or less equally throughout the epidermis, but areslightly more abundant in the anterior regions.

rdl acg

Fig. 1. Campbelionemertes jolmsi gen. et sp. nov. Oblique transverse section through the precerebralregion to show the principal structures present. The proboscis is in a partially everted position,acg, anterior cephalic groove; eg, cephalic gland; cvl, cephalic vascular loop; p, proboscis; rdl,rhynchodaeal lining. Scale=200 ^m.

cbv

HFig. 2. CampbeUonemertes johnsi gen. et sp. nov. As Fig. 1 but just posterior to transverse part ofcephalic vascular loop, acg, anterior cephalic groove; cbv, cephalic blood vessel; 1mb, longitudinalmuscle block; p, proboscis. Scale=2(X) ;*m.

A new hoplonemertean from Campbell Island 189

cm

rm

asp rd

Fig. 3. CampbeUonemertes johnsi gen. et sp. DOV. AS Fig. I but through anterior point of insertion ofproboscis, asp, accessory stylet pouch; cc, ciliated canal of cerebral organ; cm, circular musculature;CO, cerebral organ; d, dermal layer; gst, glands of stylet region of proboscis; rd, rhynchodaeum;rm, rhynchocoel musculature; v, valve of blood vessel. Scale=2(X) ^m.

Cephalic slitsThere are two pairs of horizontal lateral cephalic slits arranged in tandem (Figs 1,2 and 3). Both pairs consist of shallow depressions in the epidermis lined by a modifiedciliated epithelium that is devoid of gland cells, the posterior pair opening at theirrear end into the canals of the cerebral organs (Fig. 3).

The occurrence of two pairs of slits arranged in this way is quite unlike that seenin any of the other prosorhochmids or in Prostoma.

DermisA layer of connective tissue beneath the epidermis comprises a thin 'basement mem-brane' or dermis only 3-6 /̂ m thick. It is occasionally penetrated by muscle fibresoriginating from the outer circular zone of the body wall musculature.

A comparable thin dermal zone is found in Acteonemertes., contrasting markedlylo the very much thicker dermis (up to 20 /zm) that occurs in Potamonemertes andmost species of Geoncmertes.

Body wall musculatureThe principal body wall musculature is strongly developed. The outer circular musclelayer is 6-10 /tm thick, but the inner longitudinal layer may be as thick as 60-70 /j.m,particularly ventrally in the stomach region. The longitudinal fibres, arranged intodiscrete bundles ensheathed by connective tissue, are especially evident in the anteriorregion where they originate from the incomplete dorsoventral muscular septummarking the junction of the rhynchodaeum and rhynchocoel.

In addition to these usual hoplonemertean layers, there are blocks of dorsoventraland radial muscle fibres running irregularly through the parenchyma. In the intestinalregion these muscles form bands running between and closely apposed to the intestinaldiverticula.

The musculature of this long and slender worm is, in general, very much betterdeveloped than in other prosorhochmid genera.


ParenchymaThe parenchymal tissues in Cainpbellonemeries johnsi gen. et sp. nov. are nowhere asextensive as in Acteonetnertes, Geonemertes or Potamonemertes. Except in the cephalicregion, the various body structures are packed closely together with no obviousparenchyma between them. What parenchymatous tissue is present consists of afinely amorphous ground substance containing isolated muscle fibres and irregularly-shaped cellular inclusions.

RhynchodaeumThe rhynchodaeum opens ventrally and subterminally (Fig. I). U is a short, cone-shaped chamber from which the proboscis opens dorsally and the oesophagus ventrally.The rhynchodaeal lining is thin, unciliated and without gland cells, its dorsal halfpossessing a strong muscle layer of circular and oblique fibres derived from the dorso-ventral muscle septum.

RbynchocoelThe rhynchocoel extends the full length of the body and occupies about 50% of thebody's cross-sectional area. It is Uned internally by a thin non-glandular endotheliumoverlying a single layer of oblique and longitudinal muscle fibres that is not thickerthan 10 fim.

ProboscisThe proboscis is not a massive organ, as in Geonemertes and Potamonemertes, but is anarrow tubular structure similar to that of Acteonemertes. It is as long as or longer thanthe animal, and lies loosely coiled in the fluid-filled rhynchocoel. It is inserted anterior-ly in front of the cerebral ganglia, and is divisible into the three regions characteristicof monostyliferous hoplonemerteans.

The enlarged anterior portion is externally bounded by an epithelium composedof two cell types arranged into tall club-shaped or columnar papillae (Fig. 4). Eachpapilla is formed as a column of narrow and elongated acidophiiic cells, filled with afinely granular cytoplasm, that distaliy fan out to support the much shorter but wider

bgc

olm

arp

pn

Fig. 4. Campbeltonemertes johnsi gen. et sp. nov. Longitudinal section through a part of the anteriorproboscis in the everted condition, arp. acidophiiic region of proboscis papitia; bcm, bundle ofcircular muscle fibres; bgc, basophilic gland cells of proboscis papilla; ct, connective tissue; en,endotheliutn; ilm, inner longitudinal muscle layer; olm, outer longitudinal muscle layer; pn, proboscisnerve. Scale=30 fim.


basophilic glands. These are disposed over the entire abfrontal region of the papillae(i.e. that face of the papilla comprising the effective surface when the proboscis isused, analogous to the hooked side of a barb), and contain a somewhat coarser cyto-plasm. Papillae are up to 70 /̂ m tall but are only 30-35 ^m wide.

Beneath the epithelium a thick basophilic connective tissue 'basement membrane'20-23 (im deep forms a distinctive layer, its distal surface being extended into eachpapilla as a central core. An unusual feature of this layer is that it encloses the probosciscircular musculature as a series of discrete bundles of fibres some 6-7 /xm wide (Fig. 4).Each muscle bundle is totally enclosed by the connective tissue, and no other circularmusculature occurs in this part of the proboscis. This situation is quite unlike thatfound in other prosorhochmid genera.

Inside the connective tissue layer a zone of longitudinal musculature, 42-47 /xmin overall thickness, is effectively split into inner and outer components by the develop-ment of the proboscis nerve-supply. This split is unequal, the outer longitudinallayer being thicker than the inner, but complete, and muscle fibres do not cross fromone layer to the other. In places where the nervous system is reduced, an increaseddevelopment of the connective membrane investing the system maintains the separationof the two longitudinal muscle layers. There are twelve proboscis nerves, more or lessregularly placed, connected laterally by an extensive nerve plexus. Internally theanterior proboscis region is lined by a thin endothelium overlying a second connective'basement membrane' only 2-3 fjbm thick.

The stylet region of Campbellonemertes johnsi gen. et sp. nov. is clearly demarcatedfrom the remainder of the proboscis (Fig. 5). The posterior end of the anterior chamberjoins the stylet bulb without narrowing, the junction being marked by a raised ring ofinterstitial cells encircling the front end of the bulb. The central region is divisibleinto two parts, the anterior housing the stylet apparatus, the posterior forming amuscular contractile bulb.

The disposition of muscle fibres in the central region shows the precise arrange-ment typical of monostyliferous hoplonemerteans. The chambers of the anterior andposterior proboscis regions are connected by a duct extending through the centralbulb. In the anterior half of the bulb this duct runs beside the central stylet basis as a

sbp

s tb

msb

Fig. 5. Campbellonemertes johnsi gen. et sp. nov. Vertical longitudinal section through the styletbulb region of the proboscis, ap, anterior proboscis; i, intestine; Id, longitudinal duct of stylet bulb;msb, musculature of stylet bulb; o, ovary containing ripe egg; pp, posterior proboscis; re, rhynchocoel;sbp, slylet bulb region of proboscis; stb, stylet basis. Scale=234 /im.


broad canal, filled with an acidophilic cellular material whose derivation is uncertain.This feature is found additionally in Acteonemertes, but is absent from New ZealandGeonemertes and Potamonemertes which instead have the normal narrow duct thatdoes not contain cellular inclusions.

The central stylet and basis are housed in an inverted chamber on the anteriorface of the central bulb. The basis is 100 ^m long and 75-80 fixn wide at its broadestpoint. In shape it is similar to a straight-necked retort flask with the narrow neckorientated anterioriy. The central stylet is a short needle-like structure embedded inthe distal end of the basis. It is less than half the length of its basis and does not exceed45 /xm.

CO

pvp

Fig. 6. Campbellonemertes johnsi gen. ct sp. nov. As Fig. ] but through the oesophageal region, co,cerebral organ; erg, cerebral ganglion; nd, nephridial duct; oe, oesophagus; pvp, position of vascularplug; re, rhynchocoel. Scale=200 fi.m.

vcc

Itnb

cgc

Fig. 7. Campbellonemertes johnsi gen. et sp. nov. As Fig. I but through level of ventral cerebral com-missure, cgc, ceils of cephalic gland; del, dorsal cerebral lobe; 1mb, longitudinal muscle block;nd, nephridial duct; vcc, ventral cerebral commissure; vcl, ventral cerebral lobe. Scale = 200 /̂ m.

A ttew hoplonemertean from Campbell Island 193

There are two accessory stylet pouches, each an oval chamber 105-110 ^m longand 50-54 /xm wide, orientated so that their long axes are in an oblique dorsoventralplane. Each pouch contains up to five accessory stylets, proximally embedded in acuboidal capsule some 13 fim square (Fig. 3). The remainder of the pouch is filled witha coarsely particulate substance.

The posterior end of the central bu!b is shaped hke an inverted funnel, into whichthe posterior proboscis is inserted. The width of the posterior proboscis at this pointis only some 20 fj.m compared with an overall bulb breadth of approximately 250 /xm.Anteriorly the rearmost proboscis region is extended into an 'intramuscular neck',joining the central bulb in such a way that the musculature of the bulb encircles theneck as a collar.

Anatomically the posterior proboscis is much simpler than either of its precedingregions, and closely resembles that of other monostyliferous species.

The proboscis of Campbellonemertes Johnsi gen. et sp. nov., therefore, essentiallyresembles that of Geonemertes species except for the arrangement of the circularmusculature in the anterior region, and the broad cell-containing duct of the centralbulb.

GutThe oesophagus is a short unciliated dorsoventrally-compressed tube leading from therhynchodaeum to the stomach (Fig. 6). It is lined by a simple epithelium and lacksgland cells.

The junction between stomach and oesophagus is not clearly demarcated; belowand behind the ventral cerebral commissure the oesophagus becomes less compressed(Fig. 7) and its epithelium begins to thicken. From the point where cilia first begin toappear there is a short unfolded anterior portion to the stomach but the remainderof this part of the gut consists of a large chamber with deeply convoluted walls formedfrom densely ciliated cells interspersed with gland cells, as is typical of hopionemerteans(Figs 8, 9 and 10).

mbv

Fig. 8. Camphellonemertes johnsi gen. et sp. nov. As Fig. 1 but through posterior part of cerebralganglia and anterior portion of stomach. Ibv, lateral blood vessel; mbv, mid-dorsal blood vessel;nd, nephridial duct; s, stomach; v, valve of blood vessel. Scale= 200 /Am.


The stomach extends posteriorly as a dorsoventralJy compressed pyloric tube(Fig. 11), about 650 fim long, with thinner epithelium and fewer gland cells than themain anterior region. The pylorus opens into the dorsal surface of the intestine (Fig.12), from which point an intestinal caecum extends anteriorly, ventral to the pylorictube, for about 600 urn. At its anterior tip the caecum is formed into a single pair of

tnc

^

Ffe. 9. Camphellonemertes johnsi gen. et sp. nov. As Fig, 1 but posterior to cerebral ganglia, throughstomach, die, diverticulum of intestinal caecum; Inc, lateral nerve cord; mbv, mid-dorsal blood vessel;nd, nephridial duct; p, proboscis; s, stomach.

die

mbv

Fig. 10. Campbellonemertes johnsi gen. et sp. nov. As Fig, 1 but through posterior portion of stomach,die, diverticulum of intestinal caecum; lbv, lateral blood vessel; Itic, lateral nerve cord; mbv, mid-dorsalblood vessel; nd, nephridial duct; s, stomach. Scale = 200 /xm.


long diverticula (each about 400 /xm in length) which reach forwards nearly to thecerebral ganglia (Figs 9 and 10),

The remainder of the intestine, posterior to its junction with the pyloric tube,possesses more or less serially repeated lateral diverticula, a typical hoplonemerteangastrodermal histology, and terminates posteriorly at the anus.

In all of these features the gut resembles that of Acteonemertes, Geonemertes andPotamonemertes., as well as of other hoplonetnerteans. but the muscle blocks and fibresadjoining the intestine and running between the lateral diverticula are an unusualnemertean feature.

Frontal organThere is no frontal (supra-oral) sense organ. In this respect it resembles Acteonemertesand the New Zealand Geonemertes, but differs from Potamonemertes.

Cephalic glandThe cephalic gland is well developed and occupies most of the body in the precerebralregion (Figs 1 and 2), being composed of large, irregularly-shaped cells filled with acoarsely homogeneous basophilic cytoplasm. Dorsally the gland extends back to the levelof the cerebral organs, but ventrally and laterally it reaches further, behind the cerebralganglia (some 440 /xm in total length) (Figs 6, 7 and 8), It possesses numerous im-provised openings penetrating the dorsal and dorsolateral epidermis (Fig. 13), as isusual in species lacking a frontal organ (Pantin, 1969). Equally extensive cephalicglands occur in Acteonemertes and all Geonemertes, but not in Potamonemertes norProstoma.

Cerebral organsThe cerebral organs are placed anteriorly and laterally between the oesophageal :rhynchocoel separation and the ventral cerebral commissure. They open laterally into

mbv

Inc

Fig. I I . Campbellonemertes johnsi gen. et sp. nov. As Fig. 1 but through region of pyloric tube,ic, intestinal caecum; lbv, lateral blood vessel; Inc, lateral nerve cord; mbv, mid-dorsal blood vessel;nd, nephridial duct; pt, pyloric tube. Scale=200 ^m.


the posterior of two pairs of short cephalic slits (Fig. 3). The apertures are lateral inPotamonemertes also, and variably lateral or ventrolateral in Prostoma, but in Acteone-mertes and Geonemertes (excepting G. agricola) the cerebral organs open ventrally intoa transverse furrow.

The cerebral canal extends inwards and slightly dorsally, then turns through 90°to run posteriorly. The canal is not forked, and there is no anterior sac. The nervous

Fig. 12. Campbellonemertes johnsi gen. et sp. nov. As Fig. I but through junction between pylorictube and intestine, jpi, junction of pylorus and intestine; Ibv, lateral blood vessel: lnc, lateral nervecord; nd, nephridial duct; t, testis. Scale = 200 iim.

cbv

Imb

H

Fig. 13. Campbellonemertes johnsi gen. et sp. nov. Transverse section of a portion of the cephalic glandto show improvised openings penetrating the epidernnis. cbv, cephalic blood vessel; cm, circularmusculature; d, dermal layer; dcg, discharging cell of cephalic gland; Imb, longitudinal muscle block.Scale=51 ^̂ m.


and glandular parts of the organ are slung like a saddle about the posteriorly orientatedpart of the canal (Fig. 14).

There are two distinct glandular regions, which lie dorsal and ventral to the rela-tively small ganglionic region situated on the outer side of the cerebral canal. Theglandular regions are unusually well developed and extend the full length of the organ(about 200 /lim). Posteriorly the ventral glandular portion separates into two distinctlobes, which continue posteriorly lateral or ventrolateral to the rhynchocoel.

The cerebral organ is therefore very different in appearance from that of Acteone-mertes, Geonemertes and Potamonemertes wbere the ganglionic region is relativelylarger and the glandular portion forms a small posterior adjunct. The organs ofProstoma too are quite different.

The cerebral organ nerve arises between the ganglionic and glandular portions andruns back to the ventrolateral surface of the dorsal ganglionic lobe.

EyesEyes are absent from Campbellonemertes Johnsi gen. et sp. nov., this unusual featurebeing shared with Potamonemertes but not with the other Prosorhochmidae norProstoma.

Nervous systemThe nervous system shows the typical general plan of the hoplonemerteans in con-sisting of paired biiobed cerebral ganglia, joined laterally by dorsal and ventralcerebral commissures, and a single pair of longitudinal main nerve cords running thelength of the body in the parenchyma immediately internal to the body wall muscula-ture. The dorsal cerebral lobes are slightly smaller than the ventral pair, and there are

ep

cgc

dgr

cbv

Fig. 14, Campbellonemertes johnsi gen. et sp. nov. Transverse section through the cerebral organ to showthe relationships of the component parts, cbv, cephalic blood vessel; cc, ciliated canal of cerebralorgan; cgc, cells of cephalic gland; cm, circular musculature; con, cerebral organ nerve; erg, cerebralganglion; d, dermal layer; dgr, dorsal glandular region ofcerebral organ;ep, epidermis; nr, ganglionic(neural) region of cerebral organ; rm, rhynchocoel musculature; v, valve of blood vessel; vgr, ventralglandular region ofcerebral organ. ScaIe=70 ixm.

13


mbv

Imb

Cffl

Fig. 15. Campbelionemertes johnsi gen. et sp. nov. Transverse section showing the nephridial ductsof characteristic appearance, cm, circular musculature; erg, cerebral ganglion: lbv, lateral bloodvessel; 1mb, longitudinal muscle block; mbv, mid-dorsal blood vessel; nd, nephridial duct; rm, rhyn-chocoel musculature; v, valve of blood vessel. Scale= 67 ^m.

no neurochord cells. An accessory lateral nerve is absent, and there is no dorsalcontribution to the lateral nerve as occurs in Acteonemertes. The posterior projectionson the ventral cerebral commissure of Potamonemertes are also absent.

Blood vascular systemThe blood vascular system consists of two longitudinal lateral vessels joined only by acephalic loop anteriorly (Fig. I) and an anal loop posteriorly. Immediately behindthe brain one of the lateral vessels branches to give rise to a single mid-dorsal bloodvessel (Fig. 8) which runs posteriorly between the rhynchocoel and the gut. There are notransverse connectives between the longitudinal vessels, a feature shared with Pota-monemerles and Prostoma but unlike most hoplonemerteans.

Anteriorly the vessels are large and thin-walled (Fig. 2)—lacuna-like widths (c,42 ^m) are not uncommon. Valves are frequent (Figs 3, 8 and 15), unlike Potamone-mertes, particularly in the broader anterior vessels. Posteriorly the blood vesselsnarrow and then possess thicker, contractile walls (Figs 11 and 12).

The large cephalic loop passes through the cephalic gland just above the rhyncho-daeal pore and then runs posteriorly. In front of the cerebral ganglia the two vesselscurve inwards and somewhat ventrally to pass through the cerebral ring in the ventro-lateral walls of the rhynchocoel. At this point they give off two small vascular plugs(Fig. 16). Similar structures are found in Acteonemertes, New Zealand Geonemertesand Potamonemertes. Prostoma, however, has only a single vascular plug borne on themain dorsal blood vessel.


Excretory systemThe excretory system extends throughout the body length except for the precerebralregion. Excretory ducts are mainly dorsolateral in position (Figs 7, 8 and 10), butcan be found in any position surrounded by sparse amounts of parenchyma (Figs 9,11 and 12). The ducts are large (Fig. 15), with thick vacuolated walls which stain a verypale pink and present an appearance quite unlike the specialized ducts of the Australianand New Zealand Geonemertes, whose walls have a granular cytoplasm with radialstriations. Flame cells are particularly difficult to find and do not appear to be verynumerous. They are simple, without transverse support bars. There are fewer excretoryopenings than in terrestrial prosorhochmids but many more than in Prostoma, whichhas three to fourteen pairs. Pores may open at any position on the body with theexception of the mid-dorsal line.

The excretory system appears to be less specialized than that of Acteonemertes,Geonemertes or Potamonemertes, although more complex than marine forms in beingdeveloped as a very coiled thick-walled duct opening by numerous nephridiopores andnot restricted just to the foregut region.

A parallel modification of excretory ducts occurs in the Japanese brackish-waterhoplonemerteans Sacconemertopsis and Sacconemertella (Iwata, 1970). These formshave a wide excretory duct extending the full body length, but it is less coiled than inCampbellonemertes johnsi gtn. et sp. nov. and possesses only a single pair of efferentducts.

GonadsThe specimens are hermaphroditic (one apparently protandrous, two simultaneous)with separate ovaries and testes throughout the body posterior to the intestinal caecum.The testes are confined to the ventral or ventrolateral positions, but the ovaries showthe usual nemertean arrangement in being distributed laterally between the intestinaldiverticula (Fig. 17). Ripe eggs are large, subspherical, with maximum diameters of

vp

cbv

Cffl

Fig. 16. Campbellonemertes johnsi gen. et sp. nov. Transverse section through a vascular plug. cbv.cephalic blood vessel; erg, cerebral ganglion; en, rhynchocoel endothelium; rm, rhynchocoel muscula-ture; vp, vascular plug. Scale=20 ^m.


np

mbv

Fig. 17. Campheltonemertes Johnsigsn. el sp. nov. As Fig. 1 but through intestinal region. Ibv, lateralblood vessel; Inc, lateral nerve cord; mbv, mid-dorsal blood vessel; nd. nephridial duel; np, nephridio-pere; o, ovary containing ripe egg; t, testis containing mature spermatozoa. Scale=200 ^m.

200 ^m or more. A single egg only is matured by each ovary, but not all the ovaries areripe at the same time.

Type specimensThe type specimens, forming a syntypic series, form a part of the Pantin Collectiondeposited with the British Museum (Natural History), London.

DiscussionFor taxonomic comparisons it is the total assemblage of characters that must beconsidered, rather than a few specific points.

Tables 1 and 2 give a full comparison between the present specimens of Campbel-hnemertes johnsi gen. et sp. nov. and Acteonemertes, New Zealand Geonemertes andPotamonemertes. the three other prosorhochmid genera occurring in the New Zealandregion. Comparison is also made with Prostoma (Tetrastemmatidae) as the only otherfreshwater hoplonemertean genus. Geonemertes from other geographical areas arenot included in the Tables since the genus as a whole is probably a convergent assemblyof separately evolved terrestrial nemerteans (Pantin, 1961a, 1969), and it is likely thatonly the New Zealand forms (G. novaezealandiae, G. pantini and another currentlyundescribed species) are directly relevant.

A more complete discussion of the systematic relationships of these hoplonemer-teans (excluding Campbellonemertes johnsi gen. et sp. nov.) is given in Moore &Gibson (in press). We suggest that hoplonemerteans have colonized freshwater viatwo distinct routes; the tetrastemmid line via estuaries and brackish water to Prostoma,and, in the New Zealand area, the prosorhochmid line via supralittoral and terrestrialforms to Potamonemertes. The occurrence in the Antipodes of a second freshwaterprosorhochmid genus, Campbellonemertes gen. nov., is therefore very interesting.Campbellonemertes johnsi gen. et sp. nov. may be more closely allied with the genus

Table 1. The principal anatomical features of Cam/j/w/Zone/Her/ej/oA/is/gen. et sp. nov. compared withthose of Acteonemertes, New Zealand Geonemertes, and Potamonemertes. For additional referencethe characters oi Prostoma are also listed

Character

Habitat

Colour

Main body layers:M=; musculature;P = parenchyma;degree of development

Gut: pylorus and caecum aswell as anterior diverticula

Rhynchocoel: as long as body

Proboscis: large in sizecompared with body

Proboscis nerves

Stylet region 'normal'

Cephalic glands extensive,extend to brain

Frontal organ present

Eyes

Cerebral organ opensventrally (V) or laterally (L)

Cerebral organ:'Anterior sac' and forkedcerebral canalGland region

Accessory lateral nerve

Ventral cerebral commissure:anterior projections (A),posterior knobs (P)

Blood vascular system:Lacunar or notValvesCross links via a capillarynetworkPlugs

Excretory ducts:Specialized end regionNumerous pores

Sex organs:Definite hermaphroditismTestes anterior

Acreone-mertes

Upper littoralor terrestrial

White orwith 2 brown

stripes

M -1-P -1-

+

+0

15-18

0

+

04-6

V

0

+0

A +P 0

0++

2

0+

00

NewZealand

Geonemertes

Terrestrial

2 or 4brownstripes

M +P +

+

++

12-21

+

04V

+

++ orO

AOP 0

0-1-

+

2

++

00

Tetrastemma-Prosorhochmidae

Campbello-nemertes

johnsigen. et

sp. nov.

Freshwater

Grey, 1whitestripe

M -1- +P -

+

+0

12

0+

0

0

L

0

+ -I-

0

AOP 0

++0

2

0+

+0

Poiamo-nemertes

Freshwater

White

M +P +

+

++

11-12

+0

+0

L

0

+

0

AOP -1-

+00

2

+

++

tidae

Prostoma

Freshwater

No stripe.variablereddish-

brown

M -P -

0

0

0

9-11

+0

-1-1

4-82

L'

0

+0

AOP 0

0+ ?

0

1

00

-1-0

Except P. rubriim.Except P. puteale.


Table 2. The intrafamilial resemblances between Campbellonemertes johnsi gen. et sp. nov. and otherantipodean prosorhochmids, showing how a greater number of characters is shared with Acteone-mertes ihan with the other two genera. \ = Acteonemertes; C= Campbellonemertes; G = Geonemertes;P = Potamonemertes

C A G P

New Zealand locality + + . ( . . +Rhynchocoel full length of body + + + .(.Anatomy of the gut 4- + + +Two vascular plugs present + + + 4.Cephalic gland extensive .f + + 0Frontal organ absent + + + 0Valves present in blood vessels + 4. + 0Dermis a thin 'basement membrane' + + + 0Large rhynchocoel but comparatively small size proboscis + -f 0 0Stylet region of proboscis with broad duct containing acidophiiic cells -I- + 0 0Freshwater habitat + 0 0 - 1 -Absence of eyes 4 - 0 0 4-Cerebral organs open laterally 4 - 0 0 +Blood vessels large and lacunar anteriorly, with no capillary network

and no transverse connectives 4 - 0 0 - 1 -Hermaphroditic 4 - 0 0 4-Well developed body wall musculature 4 - 0 0 0Two pairs of longitudinal cephalic furrows 4 - 0 0 0Cerebral organ structure - 1 - 0 0 0Anatomy of excretory ducts 4 - 0 0 0Proboscis circular musculature in connective tissue 4 - 0 0 0Testes ventral 4 - 0 0 0

Acteonemertes than with either Potamonemertes or Geonemertes (see Tables I and 2).In any event, it provides strong supporting evidence for this evolutionary route tofreshwater among prosorhochmids.

AcknowledgmentsWe should like to thank Dr P. M. Johns for providing the specimens, Mrs A. M.Pantin, Dr J. E. Smith and Dr J. P. Harding for access to the late Professor C. F. A.Pantin's material. Professor T. Weis Fogh for facilities in the Cambridge ZoologyDepartment (J. M.), Professor A. J. Cain for facilities in the Department of Zoology,Liverpool University {R. G.) and Mr D. J. Buck for preparing the slides. J. M. isindebted to the Scientific Research Council for financial assistance.

ReferencesGTBSON R. & YotjNc. J.O. (1971) Prostoma jenningsi sp. nov., a new British freshwater hoplonemertean.

Freshwat. Biol. 1. 121-127.IwATA F. (1970) On the brackish water nemerteans from Japan, provided with special circulatory

and nephridial organs useful for osmoregulation. Zool Anz. 184, 133-154.MOORE J. & GIBSON R. (in press) A new genus of freshwater hoplonemertean from New Zealand.

Zoal. J. Linn. Soc. 52.PANTIN C.F.A. (1961a) Geonemertes. a study in island life. Froc. Linn. Soc. Lond. Ill, 137-152.PANTIN C.F.A. (1961b) Acteonemertes bathamae. gen. et sp. nov. An upper littoral nemertine from

Portobello, New Zealand. Proc. Linn. Soc. Lond. 172, 153-156.PANTIN C.F.A. (1969) The genus Geonemertes. Bull. Br. Mus. nat. Hist. {Zool) 18, 263-310.

on a new genus of freshwater hoplonemertean from campbell island

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