BULLETIN OF MARINE SCIENCE, 27(3): 552-571, 1977

A NEW GENUS AND SPECIES OF LINEID HETERONEMERTEAN FROM SOUTH AFRICA, POLYBRACHIORHYNCHUS DAYI (: ANOPLA), POSSESSING A MULTI- BRANCHED PROBOSCIS

Ray Gibson

ABSTRACT A new genus and species of lineid heteronemertean from South Africa, Polybracllio- rhyne/Ius dayi, is described and illustrated. lts most characteristic taxonomic feature, the mode of branching of the proboscis, distinguishes the worm from all other described nemerteans. The proboscis consists of a single main axis from which the primary branches arise in only a single plane either alternately along the lateral margins or dichotomously at the distal tip. Each primary branch then bifurcates regularly up to the quaternary branch let stage. Other anatomical characters can also be used to distinguish the new taxon of worms from existing heteronemertean species which have a branched proboscis and these are discussed in detail. A key for the identification of nemertean species which possess a branched proboscis is provided.

Only three species of nemerteans, all be- and Panorhynchus. They defined Gorgono- longing to the anoplan order Heteronemer- rhynchus as possessing a branched proboscis, tea, have so far been described with a the branches being regularly dichotomous branched proboscis. Gorgonorhynchus re- with numerous (32-64) divisions, whereas pens Dakin and Fordham (1931) has been the structure from Panorhynchus was de- reported from Australia (Dakin and Ford- scribed as forming a panicle-like branching ham, 1931, ] 936; Dakin, 1973; Bennett, system, with the proximal portion of the 1974) and the Marshall Islands (Coe, proboscis trunk containing one muscle cross 1947), and is probably the form from and a complete layer of circular musculature. India referred to by Gravely (1927) (see Further differences between the proboscides Gibson, 1974a: 473-474); Gorgonorhyn- of these genera lie in that "The characteristic chus bermudensis Wheeler (1940a) is dendritic form of the everted proboscis (of known from Bermuda (Wheeler, 1936, Gorgonorhynchus) is achieved by a regular 1940a) and Florida (Gibson, 1974a); and alternation of the planes of division" (Dakin Panorhynchus argentinensis Serna de Este- and Fordham, 1936: 465), whereas in ban and Moretto (1969) has been found Panorhynchus the principal lateral branches only in a lagoon near Buenos Aires, Argen- emerge in a "very open spiral" (Serna de tina (Serna de Esteban and Moretto, 1969). Esteban, pers. comm. 23 February 1976). Few species of nemerteans have been re- The proboscis of the new South African form corded from South African shores (Wheeler, possesses quite a different mode of branch- 1940b; Day, 1974). Among these, Day ing; the primary branches, apart from the (1974: 47) lists a "Gorgonorhynchus sp.," terminal pair which result from a simple although his illustration depicts a proboscis dichotomous division of the distal axial which is not branched dichotomously as in tip, are given off laterally and alternately the two species of this genus. Indeed, the from the single main axis entirely within a nature of the proboscis branching was used single plane. Each primary branch then by Serna de Esteban and Moretto (1969: divides through three successive bifurcations 167) as a major taxonomic character for to give eight quaternary branchlets. This distinguishing between Gorgonorhynchus manner of branching, together with other

552 GIBSON: NEW GENUS OF HETERONEMERTEAN 553

morphological differences, excludes the trichrome or Alcian blue methods for ana- present nemerteans from either of the genera tomical investigations. listed above and they are accordingly placed In addition, the morphology of the present in a new genus, Polybrachiorhynchus specimens has been compared with selected (Greek: poly-many; brachion-an arm; stained slides of Panorhynchus argentinensis rhynchos-a snout), the specific name dayi kindly loaned by Dr. Carmen J. de la Serna being chosen in honour of the finder, Pro- de Esteban, University of Buenos Aires. fessor John H. Day, and to mark his retire- ment from the Department of Zoology, Uni- Polybrachiorhynchus new genus versity of Cape Town, South Africa. Heteronemerteans with a single pair of deep horizontal lateral cephalic slits; with a MATERrALS AND METHODS complex branched proboscis comprising an The description of Polybrachiorhynchus undivided main axis from which primary dayi is based upon five specimens collected branches emerge in a single plane, terminal by Professor Day. Three of the , primaries formed by dichotomy of the distal originally given to the British Museum (Nat- axial tip but remaining primaries arising ural History), London, several years ago, alternately from the lateral axis margins, have been loaned through the courtesy of each primary branch dividing dichotomously Mr. S. Prudhoe but two were sent directly to to give eight quaternary branchlets; pro- the author by Dr. Charles Griffiths of the boscis axis containing three muscle layers Department of Zoology, University of Cape (outer and inner longitudinal, middle circu- Town. The localities from where the nemer- lar) and two muscle crosses; rhynchocoel teans were obtained, together with their musculature not interwoven with body wall University of Cape Town Ecological Survey muscle layers; dermal glandular zone and Catalogue Numbers, are: (1) BRE 73A outer longitudinal musculature of body wall Breede River. 34°S, 200E. One specimen, separated by distinct layer of connective tis- dug from mud in Zostera zone. Collection sue; dorsal fibrous core of cerebral ganglia date unknown. (2) BRE 158B Breede simple, not forked either at front or back; River. Two specimens, near river mouth, nervous system with neurochord cells in the intertidally from Upogebia beds. Collected 9 brain and neurochord fibres in the lateral January 1974. (3) DBN 54B Durban Bay. nerve cords; proboscis nerve supply a neural One specimen, burrowed in a sand bank. sheath without distinct nerves; foregut with Collected 19 July 1950. (4) DBN 211A a delicate layer of circular splanchnic Durban Bay. One specimen, swimming next muscles and with a longitudinal muscle plate to a wharf at night. Collected 4 October between dorsal wall and rhynchocoel; main 1951. intestinal canal enclosed by a layer of longi- The worms were preserved in formalin but tudinal muscle fibres; blood system with a have subsequently been secondarily fixed in cephalic lacunar network and a postcerebral hot (60°C) Bouin's fluid prior to sectioning foregut plexus, transverse blood connectives at 6-7 ""m in 56°C melting point paraffin present in intestinal region, mid-dorsal vessel wax. The smaller of the two worms holding developed into a long rhynchocoelic villus; catalogue number BRE 158B has been com- cephalic glands well developed, reaching pletely sectioned, but the large size of the backwards to anterior margins of brain and remaining animals made it impracticable to opening via frontal organ; without eyes; section them fully and accordingly only rep- with a caudal cirrus. resentative portions of their bodies have been examined histologically. All sections Type-Species.-Polybrachiorhynchus dayi, have been stained by either the Mallory new species. 554 BULLETIN OF MARINE SCIENCE, VOL. 27, NO.3, 1977

Polybrltchiorhynchus dltyi new species Type-Specimens.-Type material deposited with the British Museum (Natural History), London, consists of series of stained sec- tions and uncut body fragments. The Registration Numbers, with relevant Uni- versity of Cape Town Catalogue Numbers listed in brackets, are: Holotype, fully sec- tioned specimen, 1976.3.18.2 (BRE 158B); Paratypes, 1976.3.17.1 (DBN 211A), 1976.3.17.2 (DBN 54B), 1976.3.18.1 (BRE 73A) and unsectioned under 1976.3.18.2 (BRE 158B). Type-Locality.-Breede River, South Af- rica, 34°24'S, 20050'E, near river mouth, intertidally from Upogebia beds. External Appearance.-Living worms are coloured "straw yellow or tinged with pink" (letter from Professor Day dated 10 Jan- uary 1974) or yellowish-white (Day, 1974). Colour notes accompanying two of the speci- mens record that DBN 54B was reddish brown overall with pale edges, whilst DBN 211A possessed a pale yellow-brown head but had a darker body with transparent pink Figure 1. PolybrachiorhYllchus dayi. External margins. Preserved animals are a uniform features, drawn from preserved specimen. (A) En- dull flesh colour overall. tire worm. cc, caudal cirrus; If, flattened lateral 'fins' of intestinal region. (B) Anterior end viewed Polybrachiorhynchus dayi attains a size from ventral surface. mt, mouth; pp, proboscis considerably larger than has been reported pore. (C) Anterior end from lateral aspect. cs, for either Gorgonorhynchus or Panorhyn- cephalic slit. The scale bar refers to A only. chus species; live individuals, after anaesthe- tization, reach a maximum of some 25 in. in Distinct "fins" extend along the lateral mar- length (ca. 60 cm) (letter from Dr. Grif- gins for most of the body length, much as in fiths, 29 January 1974), compared with other nemerteans (e.g., species of Cerebratu- about 20 cm for Gorgonorhynchus repens Ius) which are capable of actively swimming (Dakin and Fordham, 1936), 12 cm for in an eel-like manner (Verrill, 1892; Coe, Gorgonorhynchus bermudensis (Wheeler, 1943). Posteriorly the body gradually tapers L940a) and 18 cm for Panorhynchus argen- to terminate in a small stumpy caudal cirrus tinensis (Serna de Esteban and Moretto, 3 mm or less in length. The wedge-shaped 1969). The body is commensurately bulky; head is distinguishable from the remainder of the maximum width of the largest preserved the body by the single pair of deep horizon- specimen was 11 mm, the dorsoventral thick- tal lateral cephalic slits and the mid-ventral ness 5-5.5 mm. longitudinal rhynchodaeal groove into which In preserved animals the body shape the proboscis pore opens subterminally varies from more or less rounded or oval in (Figs. IB and C). The extreme cephalic cross section anteriorly to dorsoventrally tip is notched and, as in both Gorgonorhyn- flattened in the posterior regions (Fig. lA). chus and Panorhynchus species, there are no GIBSON: NEW GENUS OF HETERONEMERTEAN 555

ed------scm------gd cd olm ]1001' pns

mdn

rc mbv dvm Inc Ibv

500 ~

Figure 2. PolyhraclriorlrYllcllUs dayi. Schematic transverse section through the anterior intestinal re- gion to show the arrangement of the various body structures, with a portion of the outer body wall en- larged to show the relationships of its different layers. cd, connective tissue layer of dermis; em, circular muscle layer; dvm, dorsoventral muscle bundles; ed, epidermis; gd, gland cell of dermis; i1m, inner ]on- gitudinaL muscle layer; in, intestine; Ibv, lateral blood vessel; Inc, lateral nerve cord; mbv, mid-dorsal blood vessel; mdn, mid-dorsal nerve; olm, outer longitudinal muscle layer; pns, peripheral neural sheath; rc, rhynchocoel; scm, subepidermal circular muscle layer. eyes. The ventral slit-like mouth is posi- examination of their sectioned material tioned immediately behind the head. shows that the arrangement is the same as in the present specimens. Both subepidermal Body Wall.-The epidermis possesses a nor- muscle layers extend the full body length in mal heteronemertean construction and shows Polybrachiorhynchus but are reduced in no unusual features. Its thickness varies in thickness precerebrally and towards the different parts of the body but reaches a caudal cirrus. maximum of about 45-50 /Lm. Beneath the The dermis is clearly divisible into outer thin epidermal basement membrane are two glandular and inner connective tissue regions layers of subepidermal or subepithelial (Fig. 2) which together in a large animal muscles (Figs. 2 and 3). The outermost may be 300 /Lmor more deep. The thicker zone forms a distinct layer of circular fibres glandular component consists of long-necked 15-18 /Lm thick, but the inner longitudinal acidophilic gland cells interspersed with the muscles are intimately mingled with the gland cells of the dermis (Fig. 2) and not slender longitudinal fibres of the inner sub- developed into a discrete muscular sheet as epidermal musculature. This is very similar in both species of Gorgonorhynchus (Dakin to the condition described for Panorhynchus and Fordham, 1936; Gibson, 1974a). Serna (Serna de Esteban and Moretto, 1969: de Esteban and Moretto (1969: 169) merely 169-a non-fibrous dermis with glands and noted that Panorhynchus argentinensis pos- longitudinal muscles interspersed), con- sessed subepithelial muscle layers consisting firmed by an examination of their sections, of longitudinal and circular fibres, but an but differs from Gorgonorhynchus species in 556 BULLETIN OF MARINE SCIENCE, VOL. 27, NO.3, 1977

rv Ism

ex

Figure 3. Polybrachiorhynchus dayi. Schematic transverse section through the foregut region to show the main anatomical features. cd, connective tissue layer of dermis; ex, excretory tubule; fg, foregut; Ibv, lateral blood vessel; Inc, lateral nerve cord; Ism, longitudinal splanchnic muscle plate; pns, peripheral neural sheath; rc, rhynchocoel; rv, rhynchocoelic villus.

which the dermal glands are embedded in confined to the dorsal and lateral body mar- connective tissue and the longitudinal muscle gins and do not reach in front of the brain. fibres are absent (Dakin and Fordham, The outer longitudinal musculature, con- 1936). In Polybrachiorhynchus the dermal versely, continues precerebrally to form the glandular zone is separated from the princi- bulk of the cephalic muscles. pal body wall musculature by a distinctive Dorsoventral muscle bundles are best de- fibrous connective tissue layer (Figs. 2 and veloped in swimming and bathypelagic 3) and this too is like Panorhynchus, where nemerteans which possess broad flattened there is a fibrous layer containing numerous bodies (Gibson, 1972) . In Polybrachio- circular muscle fibres (Serna de Esteban rhynchus dayi, which swims actively, strong and Moretto, 1969: 169); whether the dorsoventral muscle fibres extend between fibrous lamellae seen in the present nemer- the dorsal and ventral portions of the circu- teans are indeed muscle fibres or merely lar muscle layer (Figs. 2-4), passing around connective tissue strands could not be deter- the lateral gut margins and amongst the mined. The outer dermal zone of Poly- fibres of the inner longitudinal zone. They brachiorhynchus dayi is more or less regularly are particularly apparent in the intestinal re- penetrated by radial muscle fibres. gions but are also found alongside the pos- The main body wall muscle layers are terior portions of the foregut. In Panorhyn- well developed and show a normal hetero- chus argentinensis dorsoventral muscles are nemertean disposition (Figs. 2 and 3). scarce and confined to the intestinal zones There is no oblique muscle zone. Im- (Serna de Esteban, pers. comrn. 23 Feb- mediately outside the circular layer the ruary 1976). peripheral neural sheath forms a zone up to 20-25 ,urn thick; above the rhynchocoel it Parenchyma.-In Polybrachiorhynchus an is enlarged into a distinct mid-dorsal nerve extensive parenchymal development is which extends the full body length (Figs. 2 found, particularly on either side of the and 3). In front of the mouth the two inner- rhynchocoel and around the intestine (Figs. most muscle layers are reduced in thickness, 2 and 3) where it may reach a thickness of GIBSON: NEW GENUS OF HETERONEMERTEAN 557

Figures 4-5. Polybrachiorhynchus dayi. (4) Transverse section through a part of the body wall mus- culature in the anterior intestinal region to show the well developed dorsoventral muscle bundles. Mal- lory. Scale = 150 ",m. (5) Transverse section through the rhynchocoel to show the large rhynchocoelie villus (rv) projecting into the lumen. Mallory. Scale = 150 ",m.

150-200 J.tm. This considerably exceeds the a common pore (Dakin and Fordham, 1936; amount reported from Gorgonorhynchus Gibson, 1974a). The nature or occurrence species (Dakin and Fordham, 1936; Gibson, of a frontal organ and cephalic glands in 1974a) but is surpassed by that seen in sec- Panorhynchus argentinensis is not mentioned tions of Panorhynchus argentinensis. by Serna de Esteban and Moretto (1969) and cannot be discerned in the sections ex- Cephalic Glands and Frontal Organ.-The amined. cephalic glands of Polybrachiorhynchus con- sist of three loosely aggregated tracts of Rhynchodaeum.-As in the species of Pano- .glandular lobules reaching back between the rhynchus and Gorgonorhynchus, the probos- cephalic muscle fibres to near the anterior cis pore opens ventrally and subterminally borders of the brain. The dorsal lobules (Fig. IB). It leads into an elongate tubular form a wide band occupying much of the chamber lined by a columnar epithelium head above the rhynchodaeum and cephalic 30 J.tmor more deep which does not contain blood supply, whereas the ventral glands gland cells. The rhynchodaeal walls are form a unified zone in front of the proboscis often deeply folded and, in transverse sec- pore but then separate into two bundles run- tion, give the chamber a corrugated appear- ning along the ventrolateral margins of the ance. The epithelium is enclosed by only a rhynchodaeum. At the extreme anterior tip single layer of circular muscle fibres 10-12 of the head the cephalic glands discharge via J.tmthick, which in turn is embedded in a the frontal organs, which consist of three massive zone of longitudinal muscles in small pits lined by a simple ciliated epithe- which the cephalic blood vessels run. The lium which lacks gland cells. The pits are rhynchodaeum, blood supply and muscula- close to but quite distinct from each other; ture together form a central "core" in the this arrangement differs from the trifoliate head separated from the remaining cephalic structure occurring in Gorgonorhynchus spe- structures by only weakly developed horizon- cies where three radiating canals open into tal and radial muscle strands which do not 558 BULLETIN OF MARINE SCIENCE, VOL 27, NO.3, 1977 form a clear layer. In contrast the longi- divides dichotomously through three suc- tudinal fibres and cephalic blood vessels in cessive bifurcations to yield eight quaternary Gorgonorhynchus are sandwiched between branchlets; i.e., in a probiscis with twelve two distinct circular muscle layers (Dakin primary branches (the most seen) the maxi- and Fordham, 1936; Gibson, 1974a), whilst mum theoretical number of terminal branch- in Panorhynchus the circular zone adjacent lets is ninety-six, although full eversion or to the rhynchodaeal epithelium is only very retraction beyond the tertiary branching thin and the entire cephalic "core" is sur- stage was not apparent and, as in the organ rounded by strongly developed horizontal illustrated, rather fewer than this number and radial muscle bundles. may actually be distinguishable. This branching pattern contrasts markedly with Rhynchocoel.-The rhynchocoel extends for that found in Gorgonorhynchus, where the the full body length. Its cross-sectional proboscis divides through six successive and shape varies considerably and in general it regular dichotomous divisions, consecutive becomes wider and more flattened in the planes of division being at right angles to posterior body regions (Fig. 7E-L). each other, to yield a maximum of 64 ter- The rhynchocoel musculature, as in Gor- minal branchlets (Dakin and Fordham, gonorhynchus and Panorhynchus, consists of 1936). Some degree of irregularity may be inner longitudinal and outer circular layers present; in Gorgonorhynchus bermudensis (Figs. 2, 3 and 5) which are not interwoven the full complement of branches is only rarely with the body wall muscles. Pre-orally the found and regular dichotomy occurs only up stronger circular zone may ventrally attain a to the 16th branch stage, subsequent divi- thickness of 100 p'm or more. The rhyn- sions tending to be somewhat irregular chocoel is internally lined by a delicate (Wheeler, 1940a: 436). The pattern shown cuboidal epithelium 10-12 p'm or less thick, by Panorhynchus is much closer to that of except in the anterior regions where the mid- the present nemerteans. Serna de Esteban dorsal blood vessel penetrates the ventral and Moretto (1969: 167) state that in rhynchocoel wall to form an elongate rhyn- Panorhynchus argentinensis the proboscis chocoelic villus. The villus, which appears consists of a thick, conical, principal trunk as a long prominent ridge (Figs. 3, 5 and from which the more slender secondary 7F-J) , is separated from the rhynchocoel branches emerge alternately to terminate in lumen by layers of circular and longitudinal a single dichotomous division. The second- muscle fibres overlain with a columnar epi- ary branches (equivalent to the primaries thelium 35-40 p'mthick. of the present species), however, emerge in Proboscis.-The proboscis of Polybrachio- a "very open spiral" and not in a single rhynchus (Fig. 6) is a complex organ ex- plane, the number of branches is small and hibiting a branching system quite unlike they never themselves bifurcate more than that in either Gorgonorhynchus or Pano- once (Serna de Esteban, pers. comm. 23 rhynchus. It consists of a single long main February 1976). The branching pattern of axis from which the primary branches (Fig. Polybrachiorhynchus is thus considerably 6B: 1-12) arise laterally and alternately, more complex than that in the genus Pano- except for the terminal pair which result rhynchus. from a simple bifurcation of the distal axial The various types of proboscis in the three tip. Infrequently two consecutive lateral genera can also be distinguished at the histo- primaries may emerge from the same side of logical level. The proximal region (i.e., the the main stem (Fig. 6B: 2 and 3), but in unbranched portion) possesses eight recog- most instances the lateral branches are reg- nisable layers in Polybrachiorhynchus. ularly alternate. All of the primary branches These are an outer, glandular epithelium arise in the same plane. Each branch then 100 p'rn or more thick depending upon the GIBSON: NEW GENUS OF HETERONEMERTEAN 559

Figure 6. Polybrachiorhynchus dayi. The proboscis. (A) Photograph of discarded proboscis, repre- sented in diagrammatic form in B. The organ, after being discarded, had almost fully inverted itself so that the outer epithelium lies on the inside of the structure, as shown in C and D. 1-12, primary branches; rna, main axis; qb, quaternary branchlet; sb, secondary branch let; tb, tertiary branchlet. (C) Transverse schematic section of main axis at level indicated by solid arrow. The positions of the two muscles crosses are indicated by pecked arrows. em, circular muscle layer; ct, outer connective tissue layer; en, endothelial lining; ep, epithelium; ilm, inner longitudinal muscle layer; ns, neural sheath; olm, outer longitudinal muscle layer. (D) Transverse schematic section through a quaternary (terminal) branchlet at level indicated by solid arrow. Note the absence of muscle crosses and loss of outer longi- tudinal muscle layer. 560 BULLETIN OF MARINE SCIENCE, VOL. 27, NO.3, 1977 degree of local folding and contraction, a final branches; this is very similar to the thick and distinct fibrous connective tissue situation in the present species. zone which extends between the epithelial The proboscis of Polybrachiorhynchus folds and may be 30 p'm or more across, an dayi possesses neither a retractor muscle nor outer longitudinal muscle layer, a neural valves; in this respect it resembles the pro- sheath not developed into distinct nerves, a boscis of Panorhynchus argentinensis but in circular muscle zone, an inner longitudinal the species of Oorgonorhynchus frilled folds muscle coat, a narrow inner connective tis- of the endothelial lining are developed into sue stratum only 7-8 p'm thick, and a axillary valves which appear to control the flattened inner lining endothelium. The cir- eversion and retraction of the the organ cular muscle fibres give rise to two muscle (Dakin and Fordham, 1936: 465). crosses (Fig. 6C), one more strongly devel- oped than the other. In contrast the circular Blood System.-The blood system of Poly- musculature and muscle crosses are missing brachiorhynchus is shown schematically in from this part of the proboscis in Gorgono- Fig. 7. It is considerably more complex than rhynchus species, the circular fibres appear- that of Oorgonorhynchus (compare Gibson, ing just proximal to the first bifurcation 1974a: Fig. 5) but Serna de Esteban (pers. (Dakin and Fordham, 1936), and in Pano- comm. 23 February 1976), having been rhynchus argentinensis only a single muscle sent a photograph of Fig. 7, commented cross is present and the outer connective tis- that "we think there are no remarkable sue zone appears to be nowhere nearly as features in the blood system of Panorhyn- well developed (Serna de Esteban and chus; the pattern is similar to your photo." Moretto, 1969). An examination of sections of Panorhyn- In Polybrachiorhynchus dayi there is a chus argentinensis shows that in a general gradual reduction in the development of the sense this is correct, but that differences in various tissue layers as the different levels of detail exist which distinguish the blood sys- branching are passed. By the tertiary tem of the Argentinian species of Panorhyn- branchlet stage the outer longitudinal muscle chus from that of Polybrachiorhynchus. layer is reduced to isolated bundles of fibres Since the blood system of Panorhynchus ar- embedded in the outer connective tissues, gentinensis has not hitherto been described, and in the quaternary branch lets this layer major differences from that of Polybrachio- rhynchus dayi are noted in italics between is missing altogether (Fig. 6D). There are parentheses in the succeeding paragraphs. also no muscle crosses in the terminal In the present nemerteans the cephalic branches and only a single cross can be blood supply consists of a series of inter- discerned in the tertiary branchlets. In Oor- connected lacunar vessels loosely surround- gonorhynchus the circular muscle layer is ing the rhynchodaeum, running between the entire only as far as the fourth axils, but longitudinal muscle fibres. In front of the two muscle crosses become gradually estab- proboscis pore the cephalic supply joins at lished "distally in all sixteen branches of a single transverse connective (Fig. 7A) , the fifth order" (Dakin and Fordham, 1936: but posteriorly is soon subdivided by con- 468) and continue to the tips of the terminal nective tissue and muscle fibres to form an branches. Serna de Esteban and Moretto anastomosing complex (Fig. 7B-D). The (1969: 169) state for Panorhynchus argen- lateral lacunae on each side of the head tinensis that the proboscis and branches of tend to be larger than the other cephalic the panicle decrease in diameter towards the vessels (Fig. 7C and D) and can be regarded distal end due to a reduction in all the layers, as the principal precerebral blood channels. especially of the outer longitudinal muscula- Near the brain the cephalic branches fuse ture which terminates by vanishing from the into a single pair of slender but dorsoven- GIBSON: NEW GENUS OF HETERONEMERTEAN 561

.. ~A tc~ B~ ••• ---C5 I :C I - rdg

•• rd -G_ '~.. ov E]Fl cg rc vc

,

co Inc on f" mt " , J "~,1, , cm rv fg

in id

Figure 7. PolyhrachiorhYllclllls dayi. Diagrammatic reconstruction of the blood system, with schematic transverse sections showing the relationships between blood vessels (solid black) and the various other structures at different levels in the body (A-L). The plan of the blood system is drawn to emphasise the vascular arrangement and the different regions are not to scale. The transverse sections are to scale with each other-see scale bar at bottom centre. cg, cerebral ganglion; cm, circular muscle layer; co, ce- rebral organ; cs, cephalic slit; fg, foregut; id, intestinal diverticulum; in, intestine; iv, inner cephalic ves- sel; II, post-cerebral lateral lacuna; Inc, lateral nerve cord; mbv, mid-dorsal blood vessel; mt, mouth; on, oesophageal or buccal nerve; ov, outer cephalic vessel; rc, rhynchocoel; I'd, rhynchodaeum; rdg, rhyncho- daeal groove; rv, rhynchocoelic villus; tc, cephalic transverse connective; tv, transverse vessel; vc, ventral cerebral commissure. The points of entry to and exit from the rhynchocoel wall by the rhynchocoelic villus are indicated by white chevrons on the mid-dorsal blood vessel. trally attenuated lateral ducts which, over the ventral commissure a small vessel which the anterior part of the ventral cerebral com- emerges from the trough of the V (Fig. 7£) missure, meet below the rhynchocoel to form marks the beginning of the mid-dorsal vessel. a large V-shaped vessel. Near the middle of It immediately enters the rhynchocoel wall, 562 BULLETIN OF MARINE SCIENCE, VOL. 27, NO.3, 1977 passes through the circular muscle layer and fundamentally a hydraulic process" and Gib- runs for a very short distance in the longi- son (1974a: 483) conjectured that "The tudinal coat before forming the rhyncho- size and nature of the villus (in Gorgono- coelic villus (Fig. 7F-J) (runs for some rhynchus bermudensis) suggests that (it) distance between the circular fibres before may ... play an important part in the ejec- giving rise to the villus). Towards the rear tion and retraction mechanisms of the pro- of the ventral commissure the V-shaped ves- boscis by acting as a hydrostatic plunger in sel separates ventrally and a pair of com- conjunction with the proboscis muscles and pressed lateral vessels run for a short dis- valves." Polybrachiorhynchus dayi, like tance close to the inner margins of the brain Panorhynchus argentinensis, does not pos- lobes (Fig. 7F) but removed from them by sess proboscis valves, but the extreme length distinct layers of longitudinal and circular of the rhynchocoelic villus (more than 4 muscle fibres (by a slender connective tissue mm in a specimen 25 mm long) may indicate layer only). Behind the commissure these that it could be involved in a comparable vessels lead into a pair of comparatively mechanism. A similar villus is found in small (enormous) postcerebral lacunae Panorhynchus argentinensis but no measure- which bathe (totally enclose) the rear por- ments are available on its length. tions of the cerebral organs (Fig. 7G), the Alimentary Canal.-The long slit-like mouth lacunae themselves being in ventral commu- opens ventrally a short distance behind the nication via a transverse connective reaching brain (Figs. 1B and 7H). It leads into a below the rhynchocoel. The lateral lacunae villous buccal chamber lined by a densely extend back to just in front of the mouth ciliated epithelium 30 p'm or more thick. (behind the mouth) but then become subdi- The epithelium of both the buccal chamber vided to form a complex of mainly small and the remaining parts of the foregut are interconnected vessels which comprise the histologically identical and richly furnished foregut plexus (Fig. 7H-J). The two vessels with gland cells of the usual heteronemer- flanking the rhynchocoel are larger than tean types (Jennings and Gibson, 1969; those closely apposed to the foregut margins Gibson, 1974b and 1974c). Large num- (Figs. 3, 7I and J) and can be easily dis- bers of mucus-producing subepithelial glands tinguished in transverse sections, but remain can also be found distributed in the paren- in communication with the rest of the plexus. Near the posterior end of the foregut there is chyma immediately below the foregut and buccal lining, discharging through the gut a reduction in plexal development and in the intestinal region the blood supply consists wall into the lumen. Similar gland cells have been reported from other heteronemerteans, merely of a pair of ventrolateral vessels and including both lineid (Jennings, 1960, 1962; a single mid-dorsal vessel, joined laterally Jennings and Gibson, 1969) and baseodis- above the gut by transverse connectives cid (Gibson, 1974b) species but could not (Fig. 7K and L). with certainty be distinguished in sections of Most vessels in the body are of the lacuna Panorhynchus. Around the oral margins the type, thin-walled and without their own mus- gland cells are much more strongly stained culature, but the mid-dorsal and principal longitudinal vessels (mid-dorsal vessel only) with the Alcian blue method for mucopoly- are ensheathed by distinct layers of inner saccharides than the remaining subepithelial circular and outer longitudinal muscle fibres. glands and form a distinct ring of cells en- These fibres are even apparent in the rhyn- circling the mouth. They do not, however, chocoelic villus and here may be concerned directly correspond with the salivary or ac- with the dilation and contraction of the cessary buccal glands found in some hetero- structure. Dakin and Fordham (1936: 469) nemerteans (Cerebratulus, Micrura) (Coe, stated that "Retraction of the proboscis is 1901) since they do not reach into the outer GIBSON: NEW GENUS OF HETERONEMERTEAN 563 longitudinal muscle layer of the body wall. usually possess its own musculature, al- Somewhat similar structures occur in Gor- though in some species it is enclosed by a gonorhynchus species (Dakin and Fordham, thin layer of circular fibres for part or most 1936; Gibson, 1974a) and seem to be of its length (Gibson, 1972). In Polybrachi- present in Panorhynchus argentinensis. orhynchus the median intestinal tube is en- In many heteronemerteans the presence closed by a distinct layer of longitudinal or absence of a splanchnic muscle layer fibres 15-30 /Lm thick (Fig. 10) which, around the foregut is regarded as taxonom- around the diverticula, is reinforced by cir- ically important (Friedrich, 1960). Poly- cular muscles derived from the dorsoventral brachiorhynchus dayi has a delicate layer of muscle blocks. The species of Gorgonorhyn- circular fibres around the foregut, whereas chus and Panorhynchus do not possess such in Gorgonorhynchus species definitive mus- a muscular arrangement around their intes- cles are lacking (Dakin and Fordham, 1936: tines. 472) and in Panorhynchus argentinensis the Excretory System.-The excretory system splanchnic musculature is apparently formed commences just behind the mouth and ex- of spiral fibres (Serna de Esteban, pers. tends for about three-quarters of the foregut comm. 23 February 1976). A horizontal dorsal muscle plate is also present in PoLy- length. It consists of a large number of thick-walled (15 /Lm or more) nephridial brachiorhynchus, running between the rhyn- chocoel and dorsal foregut wall; this could tubules which spread profusely alongside the not be found in sections of Panorhynchus ventrolateral margins of the gut and are in intimate contact with the branches of the argentinensis. foregut vascular plexus (Fig. 3). The intestinal epithelium or gastrodermis, The main longitudinal collecting ducts 60 /Lm or more in height, is composed of are located in the anterior half of the system slender ciliated columnar cells and acidophi- and run just dorsolaterally at the outer mar- lic glands possessing a typical heteronemer- gins of the gut. A single main tubule is tean appearance. There are, however, two found on either side of the body, each open- unusual features about the intestine, namely ing via a solitary slender efferent duct dis- the distribution of its lateral diverticula and charging on the dorsolateral surface of the gland cells, and the presence of a muscle body. The nephridiopores are positioned sheath for its full length. The anterior few asymmetrically but open approximately one- millimetres of the intestine are totally with- quarter of the way along the excretory sys- out lateral pouches and, in transverse sec- tem. tions, appear simply as a dorsoventrally In contrast, the excretory tubules of Pano- compressed tube (Figs. 2 and 7K). Diver- rhynchus argentinensis commence some dis- ticula then begin to develop and are present tance post-orally, are nowhere near as nu- for the remaining intestinal length. They ap- merous and very much more obvious than pear at first as shallow unbranched pouches in the worms from South Africa. In Gor- (Fig. 8) but, more posteriorly, become in- gonorhynchus species the excretory ducts creasingly deeper and subdivided (Fig. 9). are not only in close communication with the Commensurate with the increasing diverticu- lar development the main intestinal duct is vascular supply but actually penetrate the posteriorly reduced. Acidophilic gland cells walls of the lateral blood vessels (Dakin and are present in all parts of the gastrodermis, Fordham, 1936: 474; Gibson, 1974a: 485 but show a differential distribution in being and Fig. 10). The number of nephridiopores both larger and far more abundant in the in Gorgonorhynchus is variable, from one to diverticula epithelium than in the main in- four occurring asymmetrically on each dor- testinal wall (Figs. 8 and 9). solateral margin of the body, but the number The intestine of most nemerteans does not in Panorhynchus is not known. 564 BULLETIN OF MARINE SCIENCE, VOL. 27, NO.3, 1977

Figures 8-11. PolybraclliorhYllchus dayi. (8) Transverse section through mid-intestinal region to show a shallow undivided intestinal diverticulum. id, intestinal diverticulum; in, main intestinal canal. Mal- lory. Scale = 150 i'm. (9) Transverse section through posterior intestinal region showing how the me- dian intestinal region (in) is narrowed and the lateral diverticula (id) enlarged. Mallory. Scale = 150 i'm. Note in Figs. 8 and 9 the differential distribution of the gastrodermal gland cells. (10) Transverse section through a part of the intestinal wall and a lateral blood vessel to show the muscular layers asso- ciated with these structures. in, intestine; lbv, lateral blood vessel; pa, parenchyma. Mallory. Scale = 75 i'm. (11) Transverse section through the posterior region of the ventral cerebral ganglia (vg) to show one of the large neurochord cells (nd) situated in the ganglionic layer. Mallory. Scale = 50 i'm.

Nervous System.-Serna de Esteban and has been reported separately for Panorhyn- Moretto (1969: 167) use the number and chus argentinensis by Serna de Esteban distribution of neurochord cells in the brain (1974), and Dakin and Fordham (1936) as one means of distinguishing between the describe the nervous system of Gorgono- genera Gorgonorhynchus and Panorhynchus rhynchus repens at some length. and Friedrich (1960), in his key to the The nervous system of Polybrachiorhyn- , relies upon such features as chus dayi consists of two pairs of cerebral the forked or unforked nature of the dorsal ganglionic lobes connected laterally by slen- cerebral fibre core and the presence or ab- der dorsal and thick ventral commissures. sence of neurochords to separate several of The lateral nerve cords, with a single fibrous the forms. The morphology of the brain core, run from the ventral lobes posteriorly GIBSON: NEW GENUS OF HETERONEMERTEAN 565

in the normal heteronemertean position large oral or buccal nerves passing on (Figs. 2 and 3). The fibrous core of the either side of the mouth. The buccal nerves dorsal lobes is not forked either at front or originate from the posteroventral regions of rear, the posterior region on each side the ventral cerebral commissure and, as in merely running into a stout nerve which Gorgonorhynchus (Dakin and Fordham, connects with the appropriate cerebral or- 1936; Gibson, 1974a) and Panorhynchus gan. This is the same as in Panorhynchus (personal observation) species are joined argentinensis (Serna de Esteban and pre-orally by a short transverse connective. Moretto, 1969: 169) but contrasts with In the South African worms the nerves post- Gorgonorhynclllls species where the dorsal orally remain separate, do not branch and Jobes are posteriorly forked into upper and extend for only a short distance below the lower branches, the lower portion joining foregut, whereas in Panorhynchus argen- with the cerebral organs (Dakin and Ford- tinensis each nerve divides into two, four ham, 1936: 475). nerves then running for some distance along Neurochord cells are present in the the ventrolateral margins of the foregut and ganglionic layer of the brain. They are large giving off numerous smaller peripheral (up to 60 J1.mor more in diameter) and branches. possess a characteristic clear cytoplasm (Fig. Sense Organs.-Polybrachiorhynchus, like 11). Up to seven pairs are located in the Panorhynchus and Gorgonorhynchus, does anterodorsal and mediolateral parts of the not possess eyes. dorsal lobes, two or three pairs are posi- Apart from the frontal organs, described tioned in the posterior inner regions of the earlier, the only specialized sense organs ventral. In Gorgonorhynchus species only which could be found are the well developed a single pair of neurochord cells is present, cerebral organs, attached to the posterior located in the ventral lobes (Dakin and surface of the dorsal cerebral lobes. They Fordham, 1936; Wheeler, 1940a; Gibson, are large ovoid bodies, posteriorly sur- 1974a), but in Panorhynchus argentinensis rounded by the post-cerebral blood supply more than one pair of giant (neurochord) (Fig. 7G), and represent the advanced type cells can be distinguished, occurring in both of development typically associated with the dorsal and ventral lobes (Serna de Iineid heteronemerteans (Gibson, 1972 : Esteban and Moretto, 1969: 170). The dis- 65). The ciliated cerebral canal opens from tribution of neurochord cells in the brain of the deep posterior pouch-like part of the the Panorhynchus species is thus similar to cephalic slits. It forms at first a very short that of the present nemerteans, but in the duct leading inwards opposite where the former they are only about half the size dorsal and ventral ganglionic lobes separate, (27.2-34 J1.m: Serna de Esteban, 1974). then turns posteriorly to run alongside the Neurochords are present in the lateral ventrolateral margins of the dorsal fibre core, nerve cords of Polybrachiorhynchus as well finally terminating near the hind end of the as in Gorgonorhynchus and Panorhynchus. cerebral organ in a mass of neural and glan- In transverse sections they appear as irregu- dular tissue. A second right-angled bend, larly-shaped clear areas in the fibrous tis- such as occurs in Gorgonorhynchus ber- sues. mudensis (Gibson, 1974a: 488), is absent Several other distinct nerves are found in from Polybrachiorhynchus dayi but could be the present worms, including large numbers found in Panorhynchus argentinensis. of cephalic nerves running anteriorly be- tween the muscle fibres both above and Reproductive Organs.-No evidence of below the rhynchodaeum, a distinct mid- gonad development could be distinguished in dorsal nerve (Figs. 2 and 3), and a pair of any of the sections examined. 566 BULLETIN OF MARINE SCIENCE, VOL. 27, NO.3, 1977

Distribution and Behaviour in Life.-Profes- and at least one other has been described sor Day, in a letter dated 10 January since, by Santos, 1974). Several authors 1974, wrote that "We have recorded it (the (BUrger, 1897-1907; B6hmig, 1929; Fried- nemertean) in estuaries and sheltered bays rich, 1936; Cae, 1943) have attempted to all along the south eastern coasts from the arrange the Heteronemertea into families on Breede River estuary (approx. 34°30'S/ various morphological grounds, but the most 21°30'E) to Morrumbene estuary in Mo- recent works (Friedrich, 1960; Iwata, 1967) zambique (approx. 23°40'S/35°10'E). It divide the order into five groups according burrows in soft muddy sand at low tide but to the nature of their cephalic slits. By far does not extend into less than 25% salinity. the largest of these, for convenience known It commonly occurs among the burrows of as the family (Gibson, 1972: Ap- the mud prawn Upogebia africana (Ortm.) pendix; Wilfert and Gibson, 1974: 106, and possibly feeds on them although it is 108), includes all those heteronemerteans not limited to Upogebia beds and probably which possess lateral horizontal cephalic slits also feeds on burrowing polychaetes ... and and numbers some 30 separate genera. Poly- I have seen them swimming like eels in brachiorhynchus, Gorgonorhynchus, and Durban Bay at night. Panorhynchus all have horizontal slits on Normally it is dug up when fishermen their heads and thus belong with the are digging for Upogebia as bait and fisher- Lineidae. men say that the worm itself, which they The principal morphological features of call 'tape worm', is an excellent bait . . . Polybrachiorhynchus dayi, compared with when irritated it shoots out its branching those of Gorgonorhynchus and Panorhyn- proboscis for a distance of two inches; it also chus, are summarized in Table 1. From this fragments very readily. It is never really it can be seen that, of the characters listed, common and if you get one or two in a only five are shared by all three genera and morning you are lucky." the present nemerteans possess many more features in common with Panorhynchus than SYSTEMATIC DISCUSSION with Gorgonorhynchus. Two structures in The systematic interrelationships of ne- particular which are frequently used in dis- merteans are often not well understood, tinguishing between lineid genera are the particularly at the familial and generic levels, simple or bifurcated nature of the fibrous and all too frequently taxa have been estab- portion in the dorsal cerebral lobes, and lished on the basis of characters shown sub- whether or not a distinct connective tissue sequently to possess little or no taxonomic stratum separates the dermal glandular zone significance. Systematic comparisons should from the outer body wall longitudinal mus- thus be made through an assessment of as culature (Friedrich, 1960; Correa, 1963; wide a range of morphological features as Iwata, 1967). The present nemerteans can possible, and not just on a few specific be distinguished from species of Gorgono- points. rhynchus by these characters alone, but their Polybrachiorhynchus dayi and the species separation is even further justified by dif- of Gorgonorhynchus and Panorhynchus are ferences which exist between other struc- the only nemerteans so far reported with a tures. In particular, the mode of branching branched proboscis. Their general body or- of the proboscis and number of pairs of ganization, particularly in the arrangement neurochord cells in the cerebral ganglia, of the body wall muscle layers and position which alone were regarded by Serna de of the nervous system, clearly place them in Esteban and Moretto (1969) as sufficient to the order Heteronemertea, a group which discriminate between Panorhynchus and contains a large number of genera (43 are Gorgonorhynchus, are in Polybrachiorhyn- listed by Wilfert and Gibson, 1974: 106, chus quite distinct from those of Gorgono- GIBSON: NEW GENUS OF HETERONEMERTEAN 567

Q." + 0 + + + 0 1'+ .§ CJ)

+ 0 0 + 0 ....+ + 1\ 2 ttl 1':'" ,,><.....- •...• ttl :(

'"::l o oa '0 ,d o o ....+ + 0 + +:.0 o + ~•... ttl "3 OIl ~"

"5 Oll "1::l I:: ;::l o •... •.... ttl o "1::l .§ 0. :.0'" o" ~ o ~ "1::l" .S •... •...."::l '" ell ";::l ';3 ·E'" o

'"::l •••• ~ •...•0"0 (;j •...'"::l ttl 0 •... E 0 E•... "[J ;.,..cl ll) ,dO 01:: "1::l (;j 1::;" "S. '" "1::l ll)..cl ll) " ::l ....•... .D ;., ttl ttl ;::l ~ U ~ CJ) 568 BULLETIN OF MARINE SCIENCE, VOL. 27, NO.3, 1977

'"::l o ...•... + ++ + ++ + E ::l Z

] ;;.... + 00 o + ++ c- .

... bO .S '"

o +0 o + 00 .... ."§ Q) ,Bo- •... .-•... 0- !-<

E ...::l cO "0 o ..c:: >. <..I •••• >." Q)0 ..c:: •..• ••• <..I "0 ><... ::l .S o"•... cO

... u ""' '"::l "0... E ;:l '"... •... .S t:i 0:1 c:: '"::l ~ o E •...u U ';;j 'C '-' •... ..•.. ..•.. c:: o o ... •... •... ;;...... o .D .D '"•... E E o ::l ::l o Z Z GIBSON: NEW GENUS OF HETERONEMERTEAN 569

rhynchus. Indeed, only two structures Panorhynchus argentinensis the fibres are present in Polybrachiorhynchus dayi and spirally disposed. It is in the intestinal re- Gorgonorhynchus species are not found in gion, however, that the greatest discrepan- Panorhynchus; these are the caudal cirrus cies in gut morphology are found. Pano- and the horizontal muscle plate between the rhynchus argentinensis has no muscle layers foregut and rhynchocoel walls. How valu- specifically associated with its intestine, but able the caudal appendage is as a generic in Polybrachiorhynchus dayi a distinct and character cannot at present be assessed. A well developed coat of longitudinal fibres cirrus is certainly present in several lineid ensheathes the intestine for its full length. genera and absent from others, but for many The presence of an intestinal splanchnic (Antarctolineus, Huilkia, Pontolineus, and muscle layer has hitherto been reported for Pseudolineus) (Friedrich, 1960; Miiller and only a few nemertean species and consists of Scripcariu, 1964; Serna de Esteban and an extremely thin layer of circular fibres Moretto, (968) no information regarding (Gibson, 1972); both the occurrence and the structure is available. A horizontal mus- nature of the muscles in the present speci- cle plate over the foregut, formed of longi- mens are thus quite unusual. Another tudinal fibres, is found in many lineid uncommon feature of the intestine in Poly- heteronemerteans and has been employed as brachiorhynchus is the differential distribu- a generic character (Friedrich, 1960). Its tion of lateral diverticula and gastrodermal occurrence in the present worms from South gland cells. The absence of diverticula from Africa is thus not at all unusual but is sig- the anterior intestinal region is by itself not nificant when compared with Panorhynchus necessarily remarkable, but the way in which argentinensis, in which no plate can be dis- the glands are both very much larger and cerned. more numerous in the diverticular pouches The most striking feature of Polybrachio- than in the main canal is very different from rhynchus is the complex branched proboscis. the normal heteronemertean condition and Superficially the organ resembles that of contrasts strikingly with the situation in Panorhynchus argentinensis in consisting of Panorhynchus. a long undivided axial region from which the It is concluded that the most significant primary branches emerge alternately, but on generic features of the present nemerteans closer examination several important differ- from South Africa are the morphology of ences can be seen which enable the two the proboscis and organization of the gut and forms to be clearly distinguished (Table 1). its associated musculature. There are, how- The proboscides of the two species are thus ever, several other differences which can in several ways quite distinct from each be used in distinguishing between Poly- other and, among the Lineidae, proboscis brachiorhynchus dayi and Panorhynchus morphology is often regarded as being taxo- argentinensis and these are listed in Table 1. nomically important at the generic level (Friedrich, 1960; Wilfert and Gibson, 1974). KEY TO NEMERTEAN SPECIES WHICH POSSESS A BRANCHED PROBOSCIS Major anatomical differences between Panorhynchus and Polybrachiorhynchus are lao Proboscis branched dichotomously, with also found in the alimentary canal and its short unbranched proximal region 2 lb. Proboscis branched alternately, with long associated structures. As well as the muscle undivided axial trunk 3 plate over the foregut, discussed above, the 2a. Body wall musculature in vicinity of brain three layered; anterior blood system with- orientation of the splanchnic fibres, when out ventral subcommissural vessel; probos- present, is of generic importance (Friedrich, cis irregularly branched after sixteen- branch stage ~__ 1960). In the present nemerteans the mus- GorgollorhYllchus berrnudensis Wheeler 1940 cles consist of circular fibres, whereas in 2b. Body wall musculature in vicinity of brain 570 BULLETIN OF MARINE SCIENCE, VOL. 27, NO.3, 1977

not three layered; anterior blood system ---, and M. G. C. Fordham. 1931. A new with subcommissural vessel; proboscis and peculiar marine nemertean from the regularly and dichotomously branched throughout Gorgono- Australian coast. Nature, Lond. 128: 796. 1936. The anatomy and systematic po- rllynchus repens Dakin and Fordham 1931 3a. Primary proboscis branches emerge in open sition of Gorgonorhynchus repens, gen. n., spiral from axis and divide only once; no sp. n.: a new genus of nemertines character- horizontal muscle plate between foregut and ised by a multi-branched proboscis. Proc. rhynchocoel; intestine without splanchnic Zool. Soc. Lond.: 461-483. musculature; no caudal cirrus _ Day, 1. H. 1974. A guide to marine life on ______Panorlzynclzus argen- South African shores. A. A. Balkema, Cape tinensis Serna de Esteban and Moretto 1969 Town and Rotterdam. 300 pp. 3b. Primary proboscis branches emerge in Friedrich, H. 1936. Nemertini. Tierwelt der single plane from axis and divide through three successive bifurcations; a horizontal Nord- und Ostsee IVd: 1-68. muscle plate present between foregut and 1960. Bemerkungen tiber die Gattung rhynchocoel; intestine with longitudinal Micrura Ehrenberg 1831 und zur Klassifika- splanchnic muscle layer; caudal cirrus tion der Heteronemertinen nebst vorHiufigem present Poly- BestimmungsschliisseI. VerOff. Inst. Meeres- brachiorhynchus dayi new genus and species forsch. Bremerh. 7: 48-62. Gibson, R. 1972. Nemerteans. Hutchinson, ACKNOWLEDGMENTS London. 224 pp. 1974a. Occurrence of the heteronemer- I wish to express my thanks to Professor John tean Gorgonorhynchus berrnudensis Wheeler, Day for providing much valuable information on 1940, in Floridan waters. Bull. Mar. Sci. 24: the distribution, behaviour and living appearance 473-492. of the nemerteans, to Dr. Charles Griffiths for specimens and observations on the living worms, 1974b. Histochemical observations on the localization of some enzymes associated to Mr. S. Prudhoe for permission to section Mu- with digestion in four species of Brazilian seum material, to Dr. Carmen 1. de la Serna de nemerteans. BioI. Bull. Mar. BioI. Lab., Esteban for kindly loaning slides of Panorhynchus and providing unpublished information on the Woods Hole 147: 352-368. Argentinian species, to Miss Lilian Saad for 1974c. Two species of Baseodiscus assistance with translations from Spanish, to Mr. (Heteronemertea) from Jidda in the Red Sea. Alan Barker for technical help and to Mr. Keith ZooI. Anz. 192: 255-270. Wilkinson for photographic assistance. This work Gravely, F. H. 1927. Nemertinea. Bull. Madras was supported by Science Research Council Grant Govt. Mus. New Ser., Nat. Hist. 1: 53-54. No. B/RG-87945. Iwata, F. 1967. Uchidana parasita nov. gen. et nov. sp., a new parasitic nemertean from LITERATURE CITED Japan with peculiar morphOlogical characters. Zool. Anz. 178: 122-136. Bennett, I. 1974. The fringe of the sea. Rigby Jennings, J. B. 1960. Observations on the nu- Ltd., Sydney, 261 pp. trition of the rhynchocoelan rubeI' (0. Bohmig, L. 1929. Nemertini = SchnurwUrmer. F. MUller). BioI. Bull. Mar. BioI. Lab., Pages 1-110 in W. KUkenthal and T. Krum- Woods Hole 119: 189-196. bach, eds. Handbuch der Zoologie. 2, Pt 3. 1962. A histochemical study of diges- BUrger, O. 1897-1907. Nemertini (SchnurwUr- tion and digestive enzymes in the rhyncho- mer). In H. G. Bronn, ed. Klassen und coelan Lineus rubeI' (0. F. MUller). BioI. Ordnungen des Tier-Reichs. 4 SuppI. 542 pp. Bull. Mar. BioI. Lab., Woods Hole 122: Coe, W. R. 1901. Papers from the Harriman 63-72. Alaska expedition. XX. The nemerteans. ---, and R. Gibson. 1969. Observations on Proc. Wash. Acad. Sci. 3: 1-110. the nutrition of seven species of rhynchocoelan 1943. Biology of the nemerteans of the worms. BioI. Bull. Mar. BioI. Lab., Woods Atlantic coast of North America. Trans. Hole 136: 405-433. Conn. Acad. Arts Sci. 35: 129-328. MUller, G. J., and D. Scripcariu. 1964. Ponto- 1947. Nemerteans of the Hawaiian and Marshall Islands. Occ. Pap. Bernice P. Bishop lineus arenarius nov. gen. nov. sp. (Heterone- Mus. 19: 101-106. mertini, Lineidae) und Diagnose der Gattung Correa, D. D. 1963. Nemerteans from Cura9ao. Antarctolineus nov. gen. Rev. Roum. BioI., Stud. Fauna Cura9ao 17: 41-56. ZooI. 9: 313-319. Dakin, W. J. 1973. Australian seashores. Angus Santos, E. R. D. 1974. Nemertinos (Heterone- and Robertson, Sydney, 5th ed. 372 pp. mertini e Hoplonemertini) do Brasil (Estado GIBSON: NEW GENUS OF HETERONEMERTEAN 571

de Siio Paulo). M.Sc. Dissert., Univ. S. Wheeler, J. F. G. 1936. Rccord of Gorgono- Paulo. 66 pp. rhY/lchus at Bermuda. Nature, Lond. 137: 33. Serna de Esteban, C. J. de lao 1974. Algllnas 1940a. Notes on Bermudan nemer- observaciones sobre el ganglio cerebroide de teans: Gorgonorhynchus bermudensis, sp. n. Pallorhynchus argel1til1ensis de la Serna y Ann. Mag. Nat. Hist., Ser. 11, 6: 433-438. Moretto, 1969 (Heteronemertea). Physis 33: 1940b. Some nemerteans from South 335-340. Africa and a note on Lineus corrugatus ---, and H. J. A. Moretto. 1968. Heterone- M'Intosh. J. Linn. Soc. Lond., Zool. 41: 20- mertea en la bahia de Ushuaia. I. Parbor- 49. lasia lueguina sp. nov. y Huilkia ushuaiensis Wilfert, M., and R. Gibson. 1974. A new genus gen. et sp. nov. Physis 28: 171-181. of hermaphroditic freshwater heteronemertean 1969. Un neuvo heteronemertino can (Nemertinea). Z. Morph. Tiere 79: 87-112. proboscis ramificado Panorhynchus argen- tine/lsis gen. et sp. nov. Ciencia e Invest. 25: 166-171. DATE ACCEPTED: June 23, 1976. Verrill, A. E. 1892. The marine nemerteans of New England and adjacent waters. Trans. AnDRESS: Department of Biology, Liverpool Poly- Conn. Acad. Arts Sci. 8, Pt 2: 382-456. technic, Byrom Street, Liverpool L3 3AF, England.