Australian Ascidians of the Sub-family Holozoinae and a Review of the Sub-family
University of Otago, New Zealand
[Read before the Otago Branch, May 13, 1952; received by the Editor, May 23, 1952.]
This paper contains a review of the sub-family Holozoinae, emended definitions of the genera Distaplia and Sycozoa, the definition of a new genus Hypsistozoa [type species, H. fasmeriana (Mich.)], a review of the known Australian species, a note as to their geographical distribution, and descriptions of S. tenuicaulis (Herdman), S. cerebriformis (Q. and Gaim.) and D. australensis, n.sp.
Order Aplousobranchia Lahille
Family Polycitoridae Michaelsen, 1904
Sub-family Holozoinae Berrill, 1950
Thanks to the courtesy of the staffs of the Australian Museum and the Fisheries Division, C.S.I.R.O., Cronulla, I was able on a recent visit to Australia to examine much material, including type specimens, of this sub-family, and it is apparent that some of the previous descriptions of the Australian species are not only inadequate but also erroneous—e.g., the recording of five rows of stigmata in Sycozoa tenuicaulis (Herdman) when there are only four in the type specimen.
Six members of the sub-family are found in Australian waters:—Sycozoa sigillinoides Lesson; Sycozoa tenuicaulis (Herdman); Sycozoa cerebriformis (Quoy and Gaimard); a doubtful species, Sycozoa murrayi (Herdman); Distaplia stylifera (Kowalevsky); Distaplia australensis, n.sp. Of these S. cerebriformis and S. tenuicaulis occupy anomalous positions. Michaelsen (1924) pointed out that S. cerebriformis is an intermediate between Distaplia and Sycozoa, and the present survey shows that unlike most Sycozoa species S. tenuicaulis produces buds in the tadpole stage.
Berrill (1950) recognises three genera in the sub-family—Distaplia Della Valle 1881, Holozoa Lesson 1830 (= Julinia Calman, 1894) and Sycozoa Lesson 1830 (= Colella Herdman, 1886, in part). As the original generic descriptions of Distaplia and Sycozoa were inadequate Michaelsen (1924) emended them. Even his definitions are not satisfactory, most of the characters of Distaplia overlapping those of Sycozoa, the only distinct ones being the form of the stalk and the presence or absence of a reservoir in the duct of the intestinal gland—a feature considered by Van Name (1945) to be dependent on the functional activity of that organ and not reliable as a taxonomic character.
Studying living specimens of S. sigillinoides Lesson from New Zealand waters, I first observed the very regular arrangement of the common cloacal apertures around the periphery of the distal part of the head, a region entirely free of zooids,—one per double meridional row of zooids. Due to their small size the apertures
are difficult to demonstrate in preserved colonies unless shrinkage has been kept to a minimum, and it is understandable that Northern hemisphere zoologists, with preserved material only, overlooked them or mistook the distal end of the head, depressed by shrinkage, for a single central aperture.
A similar arrangement of zooids and common cloacal apertures is seen in both S. tenuicaulis (Text Fig. 1) and S. cerebriformis (Text Fig. 2). S. sigillinoides is the type species of the genus Sycozoa and therefore this feature should be incorporated in the generic description.
The genus Holozoa, a Southern hemisphere form, contains but one species, H. cylindrica Lesson. The colonies were thought to be unisexual until Arnbäck-Christie-Linde (1949,1950) showed that the zooids are hermaphrodite with testes maturing before the ovaries. She also reports two or three well-developed eggs in the ovary, and, unless luteinization of nearly mature eggs occurs as in Ciona intestinalis (Carlisle, 1950), it is possible that several embryos develop in the brood pouch, not one only as recorded from the only colony with embryos studied to date (Hartmeyer, 1911). (Note: The Berlin Museum reports this colony as missing.) Van Name (1945) points out that the genus Holozoa may perhaps be maintained as distinct from Distaplia on account of its so-called “free-swimming” stage and the extraordinary elongate form of the colony. In S. sigillinoides heads often break off in rough weather and, in the stormy Falkland Island region in which H. cylindrica is found, a similar breaking might well be expected and be responsible for the” free-swimming” stage. H. cylindrica does hold the record for length of colony, but this alone would not justify maintaining Holozoa as a separate genus. As Van Name (1945) points out, the combined genera should by priority be known as Holozoa, but Distaplia has been accepted as a nomen conservandum.
To clarify the systematics of the sub-family Holozoinae I propose to rearrange but by no means substantially alter Berrill's definition of it (1950), to emend the genera Sycozoa and Distaplia (incorporating in it the genus Holozoa) and to erect a new genus Hypsistozoa to house a highly peculiar New Zealand member of the sub-family.
Note 1: The genus Colella Herdman, 1886, has been dropped since it incorporated several species of previously diagnosed genera (Polycitor, Sycozoa and probably Distaplia).
Note 2: The genus Cyathocormus Oka (1912, 1913) resembles Sycozoa in divisions of zooid present, number of rows of stigmata, position of heart and gonads, arrangement of zooids in meridional double rows, possession of brood pouches and the position of zooids bearing them. The genus thus lies very near the sub-family Holozoinae, being separated from it by the fact that there are no common cloacal canals, the anal apertures opening directly into the unique central cavity of the head. Added to that, it is impossible to tell from Oka's description of C. mirabilis, the only known species, whether or not the brood pouch is formed by an outgrowth of the anterior end of the oviduct.
Sub-family Holozoinae Berrill, 1950
Compound ascidians. the zooids of which consist of a thorax and abdomen connected by a narrow oesophageal region. There is no post-abdomen.
The heart lies on the side of the intestinal loop. The gonads lie on the opposite side of the intestinal loop, sometimes protruding from that region.*
There are four rows of stigmata and a well-developed atrial languet.
In mature zooids the anterior part of the oviduct grows out from the pharynx to form a brood sac which eventually becomes detached.
The vascular processes extending from the posterior end of the abdomen fuse and hypertrophy to a relatively enormous size.
Budding takes place by constriction and usually a strobilation of a tube formed by the epidermist† and containing an extension of the epicardium.
Features characteristic of the whole sub-family are not repeated in the generic descriptions which are kept as broad as possible, and statements like “parastigmatic vessels present or absent” and “stomach wall with or without ridges” have been omitted.
Genus Distaplia Della Valle, 1881, emend.
Colonies pedunculate or sessile. Zooids in small circular or oval systems or in double rows somewhat meridionally arranged. In capitate forms zooids distributed over the whole head region. Common cloacal apertures, one centrally placed or many scattered.
Colonies hermaphrodite. Zooids hermaphrodite or unisexual. Gonads on right of intestinal loop or in a sac-like projection from that region, but never involving other structures as well.
Oviducal bend forming the brood pouch with arms of different diameters.
Embryos one to many. Buds in liberated tadpoles in early stages of development only.
Note 1: The position of D. magnilarva is peculiar. Berrill (1948), in one colony alone, found young buds of three types, hermaphrodite, with testes only or with ovaries only.
Note 2: A knowledge of the life cycle of species is highly desirable, in that in several species previously recognised as unisexual it has been shown that the zooids are hermaphrodite, with testes maturing before the ovaries and both disappearing during developmental stages of the embryos.
Genus Sycozoa Lesson, 1830, emend.
Colonies pedunculate. Zooids in double rows in regular meridional arrangement and not distributed over the entire head region, the distal end being free. Common cloacal apertures regularly arranged around periphery of clear region of the head, one per double row of zooids.
Zooids and colonies unisexual. Gonads on right of intestinal loop.
[Footnote] * Berrill's phrase “never involving other structures” has been dropped in view of a New Zealand species hitherto known as Distaplia fasmeriana Michaelsen, in which the gonads (not present in the specimens originally described, 1924), project into the right anterior end of the vascular process (Brewin, 1946), whilst position of heart, origin of brood pouch, zooid structure, etc., are absolutely typical of the sub-family.
[Footnote] † Berrill's phrase, “associated with the abdominal end of the vascular process,” applies only to some species of Distaplia, as he has shown in his account of budding in D. bermudensis (1948).
Oviducal bend forming the brood pouch with arms of different diameters.
Embryos one to many. Buds if present in liberated tadpoles in early stages of development only.
Note: Most of the known Sycozoa species form part of the collections of Antarctic research vessels, and in many cases very few specimens are known. The genus as defined above houses the type, S. sigillinoides, S. tenuicaulis and S. cerebriformis. Though absence of parastigmata is characteristic of these species, its inclusion above would restrict the genus.
It is highly probable that many species—e.g., S. umbellata, S. ramulosa, S. georgiana, of which relatively little is known because of the small amount of material available, will be found to be merely local forms of S. sigillinoides.
S. murrayi (Herdman) is a dubious species, the zooid structure being insufficiently described. However, the double rows of zooids and their absence in the distal 2–3 mm. of the head show Sycozoan arrangement.
The position of S. gaimardi (Herdman) is doubtful. In zooid and common cloacal aperture arrangement it is definitely removed from Sycozoa as defined above. If, as Michaelsen (1907) and Van Name (1945) claim, the colonies are unisexual, a new genus will have to be erected to house it. (Note: Michaelsen was working over much material of good seasonal range.) If, however, as Herdman (1886) and Berrill (1948) state, the zooids are hermaphrodite, this species should be transferred to the genus Distaplia—a position which would be well in accordance with its colony form.
Genus Hypsistozoa, n. gen
Colonies pedunculate. Zooids distributed over the whole head region. Common cloacal apertures scattered.
Zooids hermaphrodite. Gonads projecting into right anterior end of vascular process.
Oviducal bend forming the brood pouch with arms of equal diameter.
Ova with little yolk. Embryos giving rise to an extra embryonic membrane—an “ectotrophe”. Buds in liberated tadpoles in an advanced stage of development.
Type species: Hypsistozoa fasmeriana (Michaelsen), a complete life history of which is being prepared for publication.
Australian Species of the Sub-Family Holozoinae
Full accounts are given only of S. tenuicaulis, S. cerebriformis and D. australensis, n.sp.
Genus Sycozoa Lesson, as emended.
Sycozoa sigillinoides Lesson, 1830.
For Syn. and Lit. see: Sycozoa sigillinoides, Van Name, 1945, p. 151. Sycozoa sigillinoides, Arnback-Christie-Linde, 1950, p. 29. Sycozoa sigillinoides, Brewin, 1952, p. 190.
A circum-south-polar species.
Distribution in Australia: Hobart, Bass Strait (Mich. 1924), Victoria, Port Western (Q. and Gaim. 1834, Mich. 1924), West Australia (Q. and Gaim. 1834), Albany, Princess Royal Harbour, Oyster Harbour (Hartm. and Mich. 1905), Fremantle, Garden Island (Mich. 1924).
Sycozoa tenuicaulis (Herdman) 1899. (Text Fig. 1A, 1B, 1C, 1D, 1E, 1F.)
Syn: Colella tenuicaulis Herdman, 1899, p. 64, Pl. Dist. 1, Figs. 1–16.
Colonies stalked with a rooting system on lower half and base of peduncle (Text Fig. 1A). Peduncles sometimes united by a slightly branched stolon (Text Fig. 1B) similar in structure to the peduncle and also producing a rooting system. Stolon up to 10 cm. long (Herdman). Peduncle hard, firm, many times longer than the head, up to 22 cm. long (Herdman), circular in transverse section, up to 6 mm. in diameter in widest part (Herdman) narrowing gradually to 1 mm. at base, colour dull yellow or dull pale purple (Herdman). Head (Text Figs. 1A, 1B, 1C) a laterally-flattened cone attached by the pointed end, colour ranging from dark brown with light longitudinal streaks, to yellow, grey, slate, dark purple brown, and dull pale purple.
Zooids confined to the head and absent from the distal extremity of it, in vertical double rows of up to 33, the youngest being nearest the stalk, those of opposing rows arranged alternately. Zooids he almost transversely. Common cloacal apertures (Text Fig. 1C) narrow oval, up to 1 mm. long, situated at the distal ends of the double rows of zooids. Test in head region soft with numerous small test cells and large bladder cells.
Text Fig. 1.—Sycozoa tenuicaulis. A. Colony showing rootlets. × 1. B. Group of colonies showing connecting stolon. × 1/2. C. Head of colony showing arrangement of zooids and common cloacal apertures. × 4. D. Right side of zooid from female colony. × 40. E. Intestinal loop and gonad of zooid from male colony. × 40. F. Tadpole, showing stolon and two buds. × 47.
Zooids up to 3 mm. long; 1 mm. wide in pharyngeal region which has 16 fine longitudinal muscle bands. Rectal-oesophageal region of medium length. Abdominal region almost the same width as pharyngeal. Vascular processes very long and fine. Branchial aperture with six short lobes, atrial surmounted by a wide lappet.
Pharynx with 16 tentacles of three orders regularly arranged (12 Herdman), dorsal lamina of three short languets, 4 rows of 15 stigmata 8 times as long as wide (5 rows of 12 stigmata (Herdman)—error), and no parastigmatic vessels. Oesophagus of medium length, stomach wide, curved, tapering towards the posterior end, and with slight roughnesses on the internal lining. Intestine long, narrow. Intestinal gland without a reservoir. (Text Fig. 1D).
Colonies of one sex. Gonads on right side of intestine (Text Figs. 1D, 1E). Testis a rosette of 6 to 8 pear-shaped lobes. Ovary with 1 to 5 eggs. Diameter of liberated egg up to 0.33 mm. Brood pouch straight, elongate, thin-walled sac with 4 to 5 embryos, and with an oviducal bend, the arms of which are of unequal diameter. Largest tadpole seen (not free-swimming) 3 mm. long, 0·7 mm. wide in head region, with 2 immature buds, one of which is in process of division (Text Fig. 1F).
An endemic species. All recorded specimens have been found in deep water.
Distribution in Australia: Port Jackson, Port Stephen, and a few attached to carapace of Macippe spinosa Stimpson (Herdman), Port Jackson (Aust. Mus. Coll.).
Remarks: In a transverse section of a fully-grown colony the succession of zooids can be traced easily. In one specimen young buds occupied the proximal 2 mm. of the head, mature individuals without brood pouches the next 4 mm., mature individuals with one embryo in the brood pouch the next 2–3 mm., mature individuals with two to three embryos in the brood pouch the next 5 mm., whilst dedifferentiating zooids with four embryos in the brood pouch were found more distally and the true distal end was devoid of zooids.
Sycozoa cerebriformis (Q. and Gaim.). (Text Figs. 2A, 2B, 2C, 2D, 2E, 2F.)
Syn: Aplidie cerebriforme Quoy and Gaimard, 1834, p. 625, Pl. 92, Figs. 16, 17. Colella plicata Herdman, 1899, p. 62, Pl. Dist. II, Figs. 1–15. Colella incerta Caullery, 1908, p. 10, Text Fig. 2B. Sycozoa arborescens Hartmeyer, 1912, p. 316. Sycozoa cerebriformis f. intermedia Hartmeyer, 1919, p. 124. Sycozoa arborescens Michaelsen, 1923, p. 22. Distaplia cerebriforme Michaelsen, 1924, p. 325.
Colonies (Text Fig. 2A) stalked, small ones fan-like, large ones rosette-like and up to 11 cm. in longest diameter. Peduncle firm, short, wide, vertically-flattened, up to 7·4 cm. high, 2·2 cm. thick (average size 3·7 cm. high, 1·0 cm. thick), width varying with form, which may be simple or branched, with branches joined by thin membranous layers of test or less frequently free; colour pale yellowish grey (Herdman, 1899), brownish red (Michaelsen, 1924). Head folded, band-like, wider than the peduncle which carries it, showing all degrees of concrescence between neighbouring portions in forms with branched peduncles, up to 1·1 cm. high, 0·7 cm. thick, 43 cm. wide following all folds (average size, 1·0 cm. high, 0·5 cm. thick, 26 cm. wide following all folds); colour pale yellow, almost white (Herdman, 1899), variable, reddish brown in one (Michaelsen, 1924). Zooids confined to head and absent from the distal extremity of it, in vertical double rows of 9 to 11 (about 6, Herdman) the youngest being nearest the peduncle, those of opposing rows arranged alternately. Common cloacal
apertures (Text Fig. 2F) narrow, crescent-shaped, up to 1 mm. long, situated at the distal ends of the double rows of zooids. Test gelatinous, with numerous small test cells and in the head region a few white pigment cells and numerous bladder cells, the latter being confined to the peripheral region.
Zooids up to 3 mm. long, 1 mm. wide in pharyngeal region, which has 10 to 12 fine longitudinal muscle bundles, 3 transverse. The rectal-oesophageal region bent at right angles, pharyngeal region of zooid lying transversely in test, abdominal somewhat vertically (Text Fig. 2B). Abdominal region slightly narrower than pharyngeal. Vascular process long, thin, arising from left side of abdominal region and passing down into peduncle. Branchial aperture with six short lobes, atrial surmounted by a short, wide lappet.
[The section below cannot be correctly rendered as it contains complex formatting. See the image of the page for a more accurate rendering.]
Text Fig. 2.—Sycozoa cerebriformis. A. Small colony. × 3/4 B. L.S. head of colony showing young, mature and dedifferentiating zooids and brood pouches with and without embryos. × 6. C. Right side of zooid from female colony. × 20 D. Left side of zooid from male colony. × 20. E.T.S. brood pouch showing oviducal loop. × 160 F. Portion of head of colony showing arrangement of zooids and common cloacal apertures. × 1 1/2.
Pharynx with 8 tentacles of 2 orders of size regularly arranged (10, Herdman), dorsal lamina of 3 short languets curving backward opposite third stigmata from the mid-dorsal line, 4 rows of 12–13 stigmata (3, occasionally 4 rows of 10, Herdman—error) 6 to 8 times as long as wide, no parastigmatic vessels. Oesophagus long, narrow. Stomach smooth-walled inside and out, smaller to-
wards posterior end. Intestine long, narrow. Intestinal gland with a small, round bladder.
Colonies of one sex. Gonads on right of intestine (Text Figs. 2C, 2D). Testis a rosette of 4 to 6 pear-shaped lobes (2 to 10, Michaelsen, 1924). Ovary with 2 to 3 eggs at different stages of development. Liberated egg heavily-yolked, up to 0.37 mm. in diameter. Brood pouch with oviducal loop of which the arms are of unequal diameter (Text Fig. 2E). One embryo only in the brood pouch. Largest tadpole seen (not free-swimming) 1·1 mm. long, 0·3 mm. wide in head region, stigmata formed, but no buds visible.
Recorded from South Africa and Australia.
Distribution in Australia: Port Jackson (Herdman), Gunnemata Bay (Aust. Mus. Coll), Port Western (Quoy and Gaimard, Michaelsen), West Australia, North West Australia (Hartmeyer), South Australia, South East Australia (Caullery).
Elsewhere: South Africa (Hartmeyer, Michaelsen).
Remarks: The presence of more than one egg in the ovary, but only one embryo in the brood pouch is peculiar in a genus where the pouch usually contains several embryos at different stages of development. The obvious conclusion is that after one egg is liberated, the eggs in the ovary which are still immature are suppressed—a conclusion supported by the absence of gonads in zooids with brood pouches containing developing embryos (Text Fig. 2B).
Dedifferentiation of the parent zooid begins during early development of the embryo, with the result that the brood pouches become isolated.
In a transverse section of the colony the succession of zooids is clearly seen, young buds being found near the stalk, maturing zooids farther up the head region, zooids with brood pouches farther up still, and dedifferentiating zooids and isolated brood pouches close to the distal end itself, a region free from zooids (Text Fig. 2B).
Sycozoa murrayi (Herdman), 1886.
Syn: Colella murrayi, Herdman, 1886, p. 119.
Whilst the zooid structure is insufficiently described to place this species with certainty in the genus Sycozoa and only specimens with male reproductive organs are available, the form of the colony and the arrangement and distribution of the zooids point to its Sycozoan affinities.
Distribution in Australia. Off S. E. Coast, v. rubida Bass Strait (Herdman).
Genus Distaplia Della Valle, as emended
Distaplia stylifera (Kowalevsky), 1874.
For Syn. see: Distaplia stylifera, Van Name, 1945, p. 147.
I have been able to examine two colonies collected on December 12, 1951, from Triggs Island, near Perth. For these I am indebted to Mrs. L. Marsh, University of West Australia. Both colonies show regular distribution of the zooids in round or oval systems of 6 to 12, each system with its own common cloacal aperture. In one colony brood pouches occur at or above the level of the gonad sacs. These contain early tailed embryos, and each is connected to the parent zooid by a narrow neck, not as long as would be thought from Hartmeyer's description (1919) and by no means as long as that seen in D. australensis (Text Fig. 3B).
Distribution in Australia: West Australia (Cape Jaubert, Hartmeyer, 1919; Sharks Bay, Michaelsen, 1930; near Perth).
Distribution elsewhere: Red Sea, East Coast of America as far south as Jamaica, South Africa.
To quote Van Name (1945) p. 149—“D. stylifera (Kowalevsky), 1874, type locality the Red Sea, ranges eastward to Saleyer Island and West Australia (Cape Jaubert and Sharks Bay). I can hardly refuse to accept the identity of the two forms in view of Michaelsen's (1930) statement that his West Australian material, excepting in the unimportant matter of colour, agrees with the West Indian form in even the smallest details and even the colour is similar in some specimens.”
Distaplia australensis, n.sp. (Text Figs. 3A, 3B, 3C, 3D.)
Colonies capitate (Text Fig. 3A). Head rounded, up to 15 mm. in diameter, 10 mm. in length. Stalk thick, fleshy, up to 7 mm. in diameter, 20 mm. in length, occasionally joined to that of a neighbouring colony by a fleshy basal membrane. Zooids confined to head, arranged in somewhat meridionally-disposed double rows but composing only one system. One common cloacal aperture per colony situated at the summit of the head, circular with fluted edges and up to 3 mm. in diameter.
Zooids (Text Fig. 3C) up to 3·5 mm. long (not counting the long vascular process) up to 1·3 mm. wide in pharyngeal region, which has about 38 fine longitudinal muscle bundles, 3 transverse. Rectal-oesophageal region short. Abdominal region approximately as wide as pharyngeal. Branchial aperture with six short lobes, atrial with languet. A long vascular process arising from left side of abdominal region.
Pharynx with 16 tentacles of 3 orders of size, not necessarily regular in arrangement. Dorsal lamina with 3 lappets. On either side 4 rows of 22 to 24 stigmata, 5 times as long as wide. Parastigmatic vessels absent. Oesophagus short. Stomach wall ridged (Text Fig. 3C). Intestinal gland with reservoir. Anal aperture smooth-edged.
Zooids hermaphrodite. Gonads in a sac projecting backwards from right side of abdominal region (Text Fig. 3C). Testis usually 5 to 6 lobed, ovary with 2 to 4 eggs showing different stages of maturity. Liberated egg up to 0·48 mm. in diameter. Brood pouches (Text Fig. 3B), with one (very rarely two) embryo seen in two colonies collected in August. Brood pouch with a very long neck and an oviducal bend with arms of different diameters (Text Fig. 3D). In the specimens available early embryological stages only present.
Distribution in Australia: Dredged South Tasmania, approx. 24 fathoms.
Type specimen in the Australian Museum. Registered number, U. 3842.
Remarks: In D. australensis and D. stylifera the presence in general of one embryo in the brood pouch, though several ova are produced in the ovary, parallels the condition found in S. cerebriformis. In all three species it would appear that the liberation of one ripe egg probably causes suppression of the others in the ovary, and it is possible that luteinization occurs as recorded for Ciona intestinalis (Carlisle, 1951).
In this species as in others of the sub-family a succession of zooids can be demonstrated clearly in the head region. Young buds are present near the junction of head and stalk. These abut mature zooids with ripening gonads, and the
distal two-thirds of the head is occupied by zooids with brood pouches, the larger embryos being found attached to zooids nearest the summit (Text Fig. 3B).
Text Fig. 3.—Distaplia australensis. A. Two adjacent colonies. × 1. B. L.S. head of colony, showing young and mature zooids and brood pouches with embryos. × 5. C. Left side of zooid. × 21. D. T.S. brood pouch showing oviducal loop. × 48.
Note: This species resembles D. stylifera in that the gonads are held in a sac backwardly projecting from the abdominal region, but differs from it in—
(1) The arrangement of the zooids and the presence of but one central common cloacal aperture as compared with the several systems of zooids and several common cloacal apertures in D. stylifera. (2) The presence of 22 to 24 stigmata per row when the number recorded for D. stylifera is 9 (Hartmeyer), 9-10 (Sluiter), 13-15, occasionally 18 (Van Name), (3) the extremely long necks of the brood pouches and their central position and (4) the geographical distribution. Van Name (1945) is inclined to question the presence in West Australia of a species apparently radiating from the Mediterranean Region, and it is even less likely that a warm water form would be dredged off Southern Tasmania.
Explanation of Lettering
al.—ascending limb of oviduct.
ccl.—common cloacal aperture.
dl.—descending limb of oviduct.
ibp.—isolated brood pouch.
Geographical Distribution of Australian Species
The distribution map (Text Fig. 4) is based on our present knowledge of the distribution of Australian species of the sub-family Holozoinae. Indications are that D. australensis and S. murrayi are confined to the colder regions of the South-East, S. tenuicaulis to the Eastern seaboard, D. stylifera to the Western seaboard, whilst S. sigillinoides and S. cerebriformis extend round the Southern, South-Eastern and South-Western coasts with S. cerebriformis extending into high latitudes on the West.
Only S. sigillinoides occurs in New Zealand waters.
▴ S. sigillinoides
• S. tenuicaulis
□ S. cerebriformis
◍ D. stylifera
≡ S. murrayi
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