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Ascidians of New Zealand
Part XI—Ascidians of the Stewart Island Region

[Received by Editor, August 21, 1957.]

Summary

The number of ascidians recorded from the Stewart Island region is raised from 30 to 58, this survey extending the southerly distribution of 21 species. Seven new species are described (Polyclinum novae-zelandiae, Amaroucium maritimum, Pseudodistoma sigillinoides, Leptoclinides novaezelandiae, Trididemnum sluiteri, Botryllus stewartensis and Molgula herdmani) and a detailed description is given of Polycarpa pegasis Michaelsen. As far as is known at present, about 15% of the species are endemic.

A survey is made of the sub-family Euherdmaninae in which a new classification is proposed and the diagnosis of Pseudodistoma Michaelsen, 1924, is emended, as also is that of Theodorella Michaelsen, 1922.

In 1898, Pizon described one ascidian from Stewart Island from the Paris Museum collection. After the Mortensen Expedition (1914–1916) a fuller account of the ascidian fauna of the region was made available, and 30 species were recorded (Michaelsen, 1922, 1924). The present survey is based on the study of (1) shore collections by W. B. Oliver (1910), L. B. Moore (1947), G. Knox (1951), and the author (1945, 1950); (2) dredged material collected by W. B. Benham (1907), M. W. Young (1926) and W. B. Dawbin (1952), and (3) material in the Otago Museum collections. The number of species recorded is 58, and accompanying the list given below is the known local distribution (H.M.B., Half Moon Bay; Pat., Paterson Inlet; P., Port Pegasus; Fov. Str., Foveaux Strait; B., Bluff).

List of Species Locality
Synoicidae
* Polyclinum cerebrale Mich. ?
Polyclinum novaezelandiae, n.sp. Fov.Str.
* Macroclinum stewartense Mich. ?
* Macroclinum arenaceum Mich. ?
* Amaroucium thomsom Brewin H M.B., Pat., Fov.Str., B.
* Amaroucium phortax Mich. var. ptychodes Mich. Pat.
Amaroucium adamsi Brewin H M.B.
* Amaroucium benhami Brewin Pat., H. M.B.
Amaroucium oamaruensis Brewin H M.B.
Amaroucium foliaceum Slutter H.M.B.
* Amaroucium maritimum, n.sp. Fov.Str.
* Pseudodistoma cereum Mich. H.M.B., Pat., P., Fov.Str.
Pseudodistoma sigillinoides, n.sp. H M.B.
Dumus areniferous Brewin H.M.B.
Didemnidae
Leptoclinides novaezelandiae, n.sp. H.M.B., Pat.
* Trididemnum cerebriforme Hartm. H M.B.
Trididemnum sluiteri, n.sp. H. M. B., Pat.
* Didemnum psammatodes Sluit., var. maculatum Nott. H.M.B., Pat.
* Didemnum studeri Hartm. f. typicum H.M.B.
* Didemnum studeri Hartm. f. africanum Mich. P.
* Didemnum chondrilla Mich. Pat.
Didemnum albidum (Verr.) H.M.B., Pat., P.
* Didemnum tuberatum (Nott.) H.M.B.
* Didemnum candidum Sav. H.M.B., Pat., P., Fov.Str. B.
* Didemnum mortenseni Mich. P.

[Footnote] † Not represented in the present collection.

[Footnote] * Present in dredged material.

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Didemnum lithostrotum Brewin H.M.B., Pat
* Diplosoma macdonaldi Herdm. Pat., P., Fov.Str, B.
Clavelinidae
Polycitor (Eudistoma) circumvallatum (Sluit.) H.M B.
* Cystodytes dellachiaiae (Della Valle) H M.B., Pat.
* Hypsistozoa fasmeriana (Mich.) H.M.B., Pat., P., Fov Str
Perophoridae
* Perophora boltenina Mich. ?
Ascididae
* Ascidia lagena Mich. Pat.
Ascidiella aspersa (Müll.) Pat.
Rhodosomatidae
Corella eumyota Traust. H.M.B., Pat., P., B.
Botryllidae
* Botrylloides leachi Sav. H.M.B., Pat., P., B
Botryllus magnicoecus (Hartm.) H.M.B.
Botryllus schlosseri (Pall.) H.M.B., B
* Botryllus stewartensis, n.sp. Pat., Fov.Str.
Styelidae
* Theodorella arenosa Mich. ?, B.
* Theodorella stewarbensis Mich. Fov. Str., P.
* Alloeocarpa minuta Brewin Fov.Str.
* Polycarpa pegasis Mich.
* Asterocarpa cerea (Sluit.) H.M.B., Pat., P., Fov.Str, B.
Cnemidocarpa nisiotis (Sluit.) H M.B.
* Cnemidocarpa bicornuata (Sluit.) H.M.B., Pat., Fov.Str., B.
* Cnemidocarpa stewartensis Mich. H M.B., Pat., P., Fov.Star.
Pyuridae
Pyura suteri (Mich.) H M.B., Pat., B.
* Pyura subuculata (Sluit.) H M.B., P., Fov.Str.
* Pyura trita (Sluit.) ?
Pyura cancellata Brewin H M.B.
* Pyura pulla (Sluit.) H.M.B., Fov.Str.
* Pyura picta Brewin P., Fov.Str.
* Pyura carnea Brewin Fov.Str.
Pyura pachydermatina (Herdm.) H.M B., Pat., P., Fov.Str., B.
Molgulidae
* Paramolgula filholi (Piz.) H.M.B, P., Fov.Str.
* Molgula sluiteri (Mich.) H.M.B., Pat, Fov.Str., B.
* Molgula mortenseni Mich. ?
Molgula herdmani, n.sp. H M.B., Pat.

Description of Species

Full descriptions are given only of genera and species not appearing in the author's papers on the ascidians of New Zealand and the outlying islands. With the following exceptions all specimens of the other species fall within the range of variability given in the initial description in this series of papers. Larger size was recorded for (1) colonies of Amaroucium thomsoni which reached the same size as specimens recorded from Taylor's Mistake (Brewin, 1950), (2) Cnemidocarpa stewartensis, one specimen of which was 4 cm long, 2.5 cm wide and 2.5 cm deep, (3) several specimens of Pyura carnea, the largest being 10 cm long, 5 cm wide, 6 cm deep. A short stout lappet was present in all zooids of Amaroucium oamaruensis, and a short eighth fold was present in the anterior half of the pharynx in 2 specimens of Molgula mortenseni. In one specimen of Asterocarpa cerea 8 stigmata only were.

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Text-fig. 1—A—Amaroucium foliaceum. A1—Right side of zooid. A2—T.S. stomach. A3—Portion of colony. B—Amaroucium maritimum. B1—Right side of zooid. B2—Colonies B3—T.S stomach. C—Pseudodistoma cereum. C1—Right side of zooid. C2—Zooid with embryois in oviduct. C3—Tadpole. C4—Colonies.

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present per mesh, and in one specimen of Cnemidocarpa bicornuata (orange in colour in Stewart Island waters) only 5–7 stigmata were present per mesh (7–10, orange form, Otago waters; 5–9 blue form Lyttelton). All specimens of Alloeocarpa minuta were of the large type recorded in the Chatham Island ascidian fauna (Brewin, 1955).

Order Krikobranchia Seeliger

Genus Polyclinum Savigny, 1816

Polyclinum novaezelandiae, n.sp.

Colony a large ovoid mass up to 8 cm in length, 4.5 cm in height above the substratum, attachment by an area 5 cm in length and approximately 1 cm in width. Test translucent with numerous small test cells, surface region only heavily impregnated with sand grains. Common cloacal apertures scattered over the free surface up to 1.5 mm in diameter, 5 to 7 mm apart. Probably owing to preservation no systematic arrangement of the zooids is apparent.

Zooids up to 12 mm in length, 1.3 mm in width in the pharyngeal region, which has 11 to 12 longitudinal muscle bundles, 18 transverse. Post-abdomen between ⅓ and ½ of the zooid length. Branchial aperture with 6 lobes, atrial with a long, wide lappet.

Pharynx with 32 tentacles of 3 orders of size regularly arranged. Dorsal lamina of 18 languets curving back opposite the fourth stigmata from the mid-dorsal line. On each side 19 rows of 19 to 20 stigmata up to 7 times as long as wide (those of the posterior row only as long as they are wide). Papillae 13 in number–i.e., slightly less than the stigmata Oesophagus short; stomach smooth, ovoid; intestine twisted to form a small closed loop posterior to the stomach; rectum long, extending more than halt way up the thorax, where it ends in a two-lobed aperture.

Post-abdomen pyriform, 5 mm long. Gonads confined to the swollen posterior portion. Attachment region thin, up to 3 mm long. Ovary anterior to testis Testis with 30 or more lobes.

Distribution. Foveaux Strait (no date, Otago Museum collection).

Type Specimen. In the Otago Museum.

Remarks. This species is separated from the closely related P. cerebrale Michaelsen (recorded off New Plymouth) mainly by the number of rows of stigmata and the number of stigmata per row. The number of rows of stigmata also distinguish it from the two Chatham Island species, P. sluiteri Brewin and P. michaelseni Brewin.

Genus Amaroucium Milne-Edwards, 1841

Amaroucium foliaceum Sluiter (Fig. I, A1, A2, A3)

1900. Psammaplidium foliaceum and Ps. ambiguum Sluiter, Tunic Stillen Ocean, p. 11, 12.

1900. Psammaplidium foliaceum and Ps. ambiguum Hartmeyer, Bronn, Kl. Ordn. Tier-R., p. 1471.

1924. Aplidium vel. Amaroucium foliaceum, Michaelsen, Vidensk. Medd. naturh. Foren, bd. 77, p. 400.

Colonies (Fig. 1, A3) small flat irregular, sandy mats up to 7 cm in largest diameter, 1 to 2 mm in height above the substratum. Test, with numerous small test cells, no bladder cells, colourless, heavily impregnated with sand except in the immediate vicinity of the zooids, Zooids yellow, in round or oval systems of 12 to 16 zooids. Common cloacal apertures circular, 1.0 mm in diameter, up to 4 mm apart.

Zooids (Fig. 1, A1) up to 3 mm long, 06 mm wide in pharyngeal region, which has 9 fine longitudinal muscle bands, 7 transverse Pharyngeal and abdominal regions approximately equal in length. Post-abdomen one-half of body length, musculature not concentrated on ventral side. Brachial aperture with six short lobes, atrial with one long tapering lappet.

Pharynx with 16 tentacles of three orders of size Dorsal lamina 7 to 8 long languets extending to the second stigmata from the mid-dorsal line. On each side 8 to 9 rows of 8 stigmata twice as long as wide, parastigmata absent. Oesophagus long, narrow; stomach short with 8 or 9 longitudinal folds (Fig. 1, A2); intestine narrow at first, widening before it bends to run towards the anterior end; anal aperture with two lobes.

Up to 18 testis blocks in posterior five-sixths of post-abdomen. Ovary anterior to testis with up to 10 eggs in various stages of development. Tadpoles at an early stage present in mantle cavity of specimens collected October 24, 1953.

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Distribution. In New Zealand: South Island, French Passage (Sluiter); Stewart Island, Half Moon Bay, coastal rocks; Otago coastline; Little Papanui, coastal rocks, 24/10/53 (in author's collection). Elsewhere: Chatham Islands (Sluiter).

Note. Sluiter's original description of A. foliaceum is by no means a full one. In essentials the specimens described above fully agree with those described by Sluiter, though probably because he was dealing with preserved material he draws attention to the smallness of the post-abdomen and fails to note the common cloacal apertures though he does describe the atrial lappets of the zooids.

Amaroucium maritimum, n.sp. (Fig. 1, B1, B2, B3).

Colonies (Fig. 1, B2) sandy, irregular round masses, club-shaped or cushion-like. Maximum measurements–club-shaped forms, 20 mm in diameter in the head, 10 mm in diameter in the stalk, 40 mm in height above the substratum–cushion-shaped forms, 18 mm in diameter, 10 mm in height above the substratum. Test light yellow, of cartilaginous consistency, heavily impregnated with sand grains, small test cells present in large numbers. Zooids orange in circular system of 7 to 10 zooids. No tendency to mound formation round the common cloacal apertures which are circular, up to 1 mm in diameter, and 4 to 6 mm apart.

Zooids (Fig. 1, B1) up to 10 mm in length, 1 mm in width in pharyngeal region, which has 12 fine longitudinal muscle fibres, 11 transverse. Post-abdomen one half body length, musculature not concentrated on ventral side. Branchial aperture with 6 short lobes, atrial prolonged into a siphon with one wide lappet.

Pharynx with 16 tentacles of three orders of size, regularly arranged; dorsal lamina of 11 languets extending to fifth stigmata from the mid-dorsal line; on each side 12 rows of 16 to 18 stigmata, 2 to 4 times as long as wide, parastigmata absent. Oesophagus comparatively long, narrow; stomach round with 6 to 8 very low folds (Fig. 1, B3), intestine narrow at first, widening shortly after the bend, extending half up pharyngeal region; anal aperture smoothedged, bi-lobed.

Up to 50 testis lobes in an irregular double row occupying the greater portion of the postabdomen. Ovary just behind intestinal bend, sometimes partly surrounded by testis lobes. Early embryos in mantle cavity October 24, 1953.

Distribution. Otago coast, Papanui Beach, in clefts in coastal rocks, 24/10/53; Foveaux Strait, no date (Otago Museum collection).

Type Specimen. In the Otago Museum.

Remarks. A. maritimum is not identical with any species so far described from New Zealand, Australia, South Africa, South America or the Antarctic. The prolongation of the atrial aperture into a siphonal tube with a single lappet is characteristic of both this species and A. siphonum Brewin from which it is separated by the rows and number of stigmata. It is separated from A. variabile Herdman by the number of stomach folds and the presence of sand in the test.

Note on the Sub-Family Euherdmaninae

For those species in the sub-family Euherdmaninae in which the zooids are completely embedded in the common test, 5 genera have been erected with the last–Sigillinaria Oka, 1933–sufficiently broadly defined to house all the known species. Van Name in 1945 accepted the genus Sigillinaria and in previous papers (1950, 1951, 1957) the author has also However, Kott (1957) has drawn attention to genera with priority. There are four of these. Placentela Redikorzev (1914) is distinguished by “Placenta stark entwickelt” and the other three genera are determined mainly on the number of rows of stigmata and the presence or absence of folds in the stomach wall. Excerpts from generic descriptions read: Pseudodistoma (Michaelsen, 1924, p. 364) “Kiemensack mit wenigen (3) Kiemenspalten-Zonen.— Magen mit (wenigen) Längswülsten.”; Homoeodistoma (Redikorzev, 1927, p. 375) “Kiemensack mit mehreren kiemensplaten — Magen glattwandig.”; Ritterella (Harant, 1931) from a resume of the diagnosis of the type species) “8 rangees de tremas — 6 ou 7 plis stomachaux”.

Kott (1957) attempted to straighten out the classification, emending the genera Pseudodistoma and Ritterella, but the classification still remains unsatisfactory.

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Though the sub-family Euherdmaninae has affinities with both the sub-family Polycitorinae of the family Clavelinidae and the family Polyclinidae it is accepted by systematists as a sub-family of the latter (Berrill, 1950). It is the author's opinion that if parallelism in classification is to be sought, the bias should be towards that of the Polyclinidae. Therefore, it is proposed that in generic differentiation the presence or absence of longitudinal folds in the stomach wall should be the main criterion and to effect this the generic description of Pseudodistoma has been emended, as shown below, so that regardless of stigmatal rows species with a longitudinally-folded stomach wall can be accommodated in it. Species with a smooth stomach wall fall into the genus Homoeodistoma as originally defined.

Genus Homoedodistoma Redikorzev, 1927

Ascidiozooide in Thorax, abdomen und Postabdomen eingeteilt.

Siphonen beide 6-lappig, beiden auf gleichen Niveau, an der Spitze des Korpers. Atrialzunge fehlt.

Kiemensack mit mehreren Kiemensplaten. Darm bildet eine gedrehte Schlinge; magen glattwandig.

Gonade in Postabdomen; Hoden und “Eierstock” nebeneinander liegend.

Type Specimen. Homoeodistoma michaelseni Redikorzev.

Note. Of the New Zealand species previously placed in the genus Sigillinaria two belong to the genus Homoeodistoma–H. arenosa (Brewin) and H. novaezealandiae (Brewin).

Genus Pseudodistoma Michaelsen, 1924, emend.

Colonial ascidians with the zooids fully embedded in the common test.

Atrial siphon opening directly on the surface of the colony, 6-lobed, without an atrial lappet.

Post-abdomen a direct continuation of the abdomen and housing the heart and gonads.

Pharynx with any number of stigmatal rows.

Gut a simple loop, stomach with any number of longitudinal folds.

Testis lobes arranged more or less in two rows along the vas deferens.

Type Species. Pseudodistoma cereum Michaelsen.

Note. Of the four New Zealand species previously placed in the genus Sigillinaria two belong to the genus Pseudodistoma–P. opaca (Brewin) and P. aurea (Brewin).

All species which were placed in the genus Ritterella can be accommodated now in the genus Pseudodistoma.

Genus Pseudodistoma Michaelsen, 1924

Pseudodistoma cereum (Michaelsen) (Fig. 1, C1, C2, C3, C4).

Syn: 1924. Pseudodistoma cereum, Michaelsen, Vidensk. Medd. naturh. Foren., bd. 77, pp. 364–374.

Colonies (Fig. 1, C4), cream, light yellow or faint pink (darkening to yellow or brownishyellow in formalin), with one or more club-shaped lobes fixed to a basal membrane up to 1 mm thick. The majority of colonies have small lobes up to 7.0 cm long, 2.0 cm in diameter with the zooids opening nearer the distal end. A few larger colonies were found in the dredged material, the largest consisting of one lobe 20 cm long, 5.5 cm in diameter. Zooids yellow or pink, branchial and atrial apertures opening separately on the head of colony. Test cartilaginous, clear or light yellow with white opaque globular patches 10° in diameter, numerous small test cells and in the vicinity of zooids elongated cells which turn bright blue in glycerine.At certain seasons round bud-like masses up to 175μ in diameter lying below the zooids.

[The section below cannot be correctly rendered as it contains complex formatting. See the image of the page for a more accurate rendering.]

Zooids (Fig. 1, C1) up to 2.4 cm long, 1.2 mm wide in pharyngeal region, which has 15 to 22 longitudinal muscle bands on each side, numerous fine transverse. Post-abdomen occupying up to 5/6ths of body length. No concentration of muscles in any special region of post-abdomen.Branchial and atrial siphons six-Iobed and with strong circular muscles.

Pharynx with 32 tentacles of three orders of size, irregularly arranged (16?, Michaelsen); dorsal lamina of two large languets curving back opposite third stigmata from mid-dorsal line; on each side three rows of 20 to 24 stigmata, six to eight times as long as wide, no parastigmatic vessels. Oesophagus long, narrow; stomach as long as wide, with four longitudinal folds; intestine without constrictions; anal aperture bi-lobed, smooth-edged.

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Zooids hermaphrodite; up to 30 testis lobes in an irregular double row in a central position in the post-abdomen and occupying ⅓ or ½ of its length. Ovary just anterior to testis (Fig. 1, C1). Up to 8 embryos in various stages of development in anterior half of the oviduct in specimens collected November (Michaeisen) and in October, 1953 (Fig. 1, C2), but none in specimens collected in April, 1950. Largest tadpole 2.7 mm in length, 0.6 mm in width in head region (Fig. 1, C3).

Distribution, Stewart Island, 35 fathoms, 29/11/1914 (Michaelsen); Paterson Inlet, intertidal coastal rocks, 10/4/40; Foveaux Strait, 17 fathoms, April, 1926; Otago coast, Little Papanui, intertidal rocks, 24/10/53 (in author's collection).

Remarks. The author wishes to thank Dr. A. Brunn, of the Copenhagen Museum, for the opportunity of studying the type specimen.

Pseudodistoma sigillinoides, n.sp. (Fig. 2, A1, A2, A3, A4).

Colonies (Fig. 2, A4) with a small basal mat of hrm texture up to 1 mm in thickness and with capitate lobes of which the head region is globular up to 1.5 cm in diameter and the stalk region (which tapers towards the base) is from 1 mm to 4.5 mm in diameter and up to 2 cm in length. Test flesh-coloured or yellow with numerous very small irregularly shaped test cells and with an almost horny texture in the peripheral regions of the staik and basal mat (in this respect and in colony form this species resemoies Sycozoa sigillinoides).

Zooids (Fig. 2, A1) up to 13 mm long, 1.5 mm wide in the pharyngeal region which has approximately lb longitudinal muscle bundles on each side, 4 transverse. Post-abdomen ¾ or more of body length. Branchial and atrial siphons with six very small short lobes.

Pharynx with 32 tentacles of at least 3 orders of size; dorsal lamina of 4 wide languets curving back opposite the third stigmata from the mid-dorsal line; on each side 5 rows of 27 to 30 stigmata, 3 to 6 times as long as wide, no parastigmatic vessels. Oesophagus short; stomach with up to 11 somewhat irregular longitudinal foids (Fig. 2, A3); intestine narrow at first, widening just after the bend, anal aperture bilobed, smooth-edged.

Gonads at least 1 mm behind intestinal loop. Ovary anterior to testis, which consists of up to 45 lobes arranged in an irregular double row. As many as 9 embryos held in mantle cavity. Tadpoles (Fig. 2, A3) up to 1.2 mm in length, 0.24 mm in width in the head region present in specimens collected November, 1955.

Distribution. Stewart Island, Half Moon Bay, coastal rocks, November, 1955.

Type Specimen. In the Otago Museum.

Note. This species is clearly differentiated by the form of the colony and the arrangement of the stigmata.

Genus Trididemnum Della Valle, 1881.

Trididemnum sluiteri, n.sp. (Fig. 2, B1, B2).

Colonies white, forming thin encrusting sheets up to 2 mm in height above the substratum. Zooids irregularly arranged around the common cloacal apertiues which are small, circular, up to 0.5 mm in diameter, up to 7 mm apart. Spiculation absent in the surface 0.1 mm, dense throughout the next 0.2 to 0.3 mm, sparse in the deeper layer. Bladder cells not discernible in the surface layer. Test cells numerous, small. Spicules (Fig. 2, B2) 10μ to 50μ in diameter, ends of rays usually acutely-pointed, occasionally blunt.

Zooids (Fig. 2, B1) up to 1.5 mm in length and 0.3 mm wide in the pharyngeal region, which is up to 0.4 mm long. Rectal-oesophageal region equal in length to pharyngeal. Brancnial siphon 0.1 mm long with six short lobes. Atrial aperture without lobes, short, tubular, behind the middle of thorax. “Seitenorgane” present. A thin, tapering muscular process projects backwards from the rectal-oesophageal region.

Pharynx with 8 tentacles of two orders of size; dorsal lamina 2 languets projecting back at the level of the third stigmata from the mid-dorsal line; on each side three rows of stigmata (9–10, 9, 8–9) up to 4 times as long as wide. Oesophagus short; stomach short rounded; a distinct mid-intestinal bulge, anal aperture smooth-edged.

Testis simple. Sperm duct with 8 colls. Ovary near testis, with one or two eggs. No tadpoles present in specimens collected 6/1/51.

Distribution. Stewart Island, Half Moon Bay, coastal rocks, 6/1/51.

Type Specimen, In the Otago Museum.

Remarks. This species is distinguished from T. cerebriforme previously recorded from the locality (Michaelsen, 1924) by the number of stigmata per row and by the absence of bladder cells in the cortical layer. In number of stigmata and coils of the vas deferens this species most closely resembles T. niveum (Giard) from which it is separated by the form of the spicules and the length of the oesophageal region (Carlisle, 1953). The distribution also makes synonymity unlikely.

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Text-fig. 2.—A—Pseudodistoma sigillinoides. A1—Right side of zooid. A2—T.S. stomach. A3—Tadpole. A4—Colony. B—Trididemnum sluiteri B1—Right side of zooid. B2—Spicules. C—Leptoclinides novaezelandiae. C1—Left side of zooid. C2—Colonies. C3—Spicules. C4—Tadpole. D—Polycarpa pegasus. Body dissected from the ventral surface, pharynx removed.

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Genus Leptoclinides Bjerkman, 1905

Leptoclinides novaezelandiae, n.sp. (Fig. 2, C1, C2, C3, C4).

Colonies in the form of globular masses or incrusting sheets, irregular in outline, up to 4 mm in thickness (Fig. 2, C2), Branchial apertures small, 0.5 mm to 1 mm apart. Spicules colourless, stellate, 20μ to 45μ in diameter (Fig. 2, C3). Test with numerous small test cells round and irregular and with the spicules evenly disposed in the top 1 mm, somewhat more scattered elsewhere. “Seitenorgane” packed with spicules.

Zooids (Fig. 2, C1) up to 1.5 mm in length, 0.7 mm in width in the pharyngeal region. Rectal-oesophageal region short with abdomen almost at right angles to the pharynx. Branchial and atrial siphons both comparatively long—0.3 mm to 0.4 mm.

Pharynx with 16 tentacles of three orders of size, dorsal lamina of 3 languets curving back opposite the third stigmata from the mid-dorsal line; on each side 4 rows of 10 stigmata per row, up to 6 times as long as wide Oesophagus narrow; stomach short, round; intestine wide, narrowing before the anal opening; anal aperture smooth-edged, bi-lobed.

Testis (Fig. 2, C1) of 3 or occasionally 4 lobes. Vas deferens with 5 spiral coils. Ovary in the intestinal loop. Tadpoles, up to 1.6 mm in length and 0.5 mm in width in the head region, present in specimens collected 10/4/49.

Distribution. Stewart Island, Half Moon Bay, on seaweeds and the test of other ascidians, 10/4/49.

Type Specimen. In the Otago Museum.

Remarks. This species is distinguished from Leptoclinides marmoreus Brewin by the arrangement of zooids and common cloacal apertures and by the number of testis lobes and coils in the vas deferens.

Order Ptychobranchia Seeliger

Genus Botryllus Gaertner, 1774

Botryllus stewartensis, n.sp. (Fig. 3, A1, A2a, A2b, A3, A4, A5).

Colonies lobate up to 3.5 cm in height above the substratum, 1.5 cm in maximum diameter, surfaces of the lobes not highly domed Zooids occupying only the distal 3 mm, systems circular, 8 to 10 zooids per system. Common cloacal apertures small, round, up to 0.5 mm in diameter. Test with numerous small test cells and the outer surface either sparsely impregnated with sand grains (Fig. 3, A2b) or heavily impregnated with sand grains and/or small shell fragments (Fig. 3, A2a).

Zooids up to 2.5 mm long, 1.2 mm wide in pharyngeal region. Branchial aperture smooth-edged, atrial aperture tubular, dorsally-situated, upper lip produced as a wide lappet (Fig. 3. A1). Pharynx with 8 tentacles of 2 orders of size regularly arranged; on each side 3 internal longitudinal vessels and 10 rows of 14 stigmata, 2 to 3 times as long as wide, parastigmatic vessels absent. Arrangement of stigmata E 4/3/2/5 D.L. Oesophagus short curved; stomach with 10 to 11 folds and a backwardly-curved caecum (Fig. 3, A3); intestine curving back to terminate in a smooth-edged anus.

Testis, one on each side of the body; palmate with backwardly-directed finger-like lobes (Fig. 3, A1), number of lobes increasing during growth of zooids, in small buds (Fig. 3, A4) 2 to 3 lobes only, in large zooids up to 14 lobes. Ovary anterior to the testis. Up to 7 eggs present on each side. Tadpoles (Fig. 3, A5) up to 0.9 mm in length, 0.2 mm in width in the head region, present in the mantle cavity of specimens collected January 12, 1952.

Distribution. Stewart Island, Paterson Inlet, on shell ground, 18 fathoms, 12/1/52; Foveaux Strait (Otago Museum collection, no date).

Type Specimen. In the Otago Museum.

Remarks. In general shape of the colony and in testis form this species is unlike any previously recorded in the Southern Hemisphere.

Note on the Genus Theodorella

In 1922 Michaelsen erected the genus Theodorella and described three species, T. arenosa, T. stewartensis and T. torus. The generic description reads “—Kiemensack ohne Falten, mit einer ziemlich geringer, unbestimmten Zahl (etwa 7 or 8 jederseit) innerer Langsgefässe.” This statement holds for T. arenosa and T. torus but not for T. stewartensis which, though in other respects a true member of the genus, has 14 longitudinal vessels. Therefore, the generic definition given below is a slightly emended one.

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Text-fig. 3.—A—Botryllus stewartensis. A1—Right side of zooid. A2a, 2b—Colonies. A3—Portion of gut showing stomach folds and caecum. A4—Young bud with bi- and tri-lobed testes. A5—Tadpole. B—Theodorella species. B1—Colony of T. arenosa. B2T. arenosa. Body dissected from the ventral surface, pharynx removed. B3T. stewartensis. Portion of gut showing stomach folds and caecum. B4—Gonads of T. arenosa (4b) and T. stewartensis (4a) showing relative lengths of gonoducts. B5—Tadpoles of T. arenosa (5a) and T. stewartensis (5b). C—Paramolgula filholi. C1—Body dissected from the ventral surface, pharynx removed. C2—Portion of pharyngeal wall. D—Molgula herdmani. Body dissected from the ventral surface, pharynx removed.

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Genus Theodorella Michaelsen 1922 emend.

Colonial ascidians. Individuals closely associated, joined by a basal membrane or stolonic connections.

Pharynx without folds, but with internal longitudinal vessels.

Polycarps—on left all unisexual male—on right partly hermaphrodite, partly unisexual male. Male polycarps with a single testis lobe.

Theodorella arenosa Michaelsen (Fig. 3, B1, B2, B3, B4a, B5a) 1922, Theodorella arenosa, Michaelsen, Vidensk. Medd. naturh. Foren, bd. 73, pp. 469–473, Fig. 31.

Colonies (Fig. 3, B1) forming compact masses on the tests of simple ascidians and on the stalks of Pyura pachydermatina Herdm. Individuals sac-like, up to 5 mm long, 4 mm wide. 4 mm deep (8 mm: 5 mm: 4.5 mm, Michaelsen), attached by the ventral surface to a paper-thin basal membrane. Test very thin, outer surface evenly encrusted with fine sand grains, inner surface milky white. Siphons bright red, separated by approximately 1.2 mm (⅓ of the body length, Michaelsen). Mantle with strong musculature.

Pharynx with 24 tentacles of 2 or more orders of size (ca. 18, Michaelsen); dorsal tubercle very small; dorsal lamina a smooth straight-edged membrane; on each side 7 internal longitudinal vessels, about 9 primary transverse vessels, parastigmata present; stigmatal arrangement of the type D. L. 9–13/4/5/5/6/5/6/11–14E; oesophagus short, narrow; stomach globular, with 14–17 folds and a curved caecum; intestinal loop with no marked differentiations; anal aperture 2-lobed, smooth-edged (Fig. 3, B2).

Six or more sac-like endocarps irregularly scattered on either side.

Atrial velum small; atrial tentacles finger-like, up to 1 mm long.

Gonads in two rows one on each side of the endostyle, the row on the left composed of 10–16 male polycarps and either not extending past the gut loop or being broken by it; that on the right composed of 13–18 polycarps mainly hermaphrodite but a few (up to 3) male sometimes included. Female and male portions with separate openings (Fig. 3, B4a). Male gonoduct up to 0.5 mm long (0.2 mm, Michaelsen). Tadpoles up to 2.4 mm long and 0.5 mm wide in the head region present in specimens collected April, 1949 (Fig. 3, B5a).

Distribution. Stewart Island, on test of other ascidians, 20 fathoms. 16/11/14 (Michaelsen); Bluff, on test and stalks of other ascidians on wharf piles, 10/4/49.

Theodorella stewartensis Michaelsen (Fig. 3, B3, B4b, B5b).

1922. Theodorella stewartensis. Michaelsen, Vidensk. Medd. naturh. Foren, bd. 73, pp. 475–479, Figs. 32, 33.

[The section below cannot be correctly rendered as it contains complex formatting. See the image of the page for a more accurate rendering.]

Colonies similar to those of T. arenosa (Fig. 3, B1) forming compact masses on the tests of simple ascidians and on shells of mollusca. Individuals sac-like, up to 6 mm long, 4 mm high, 3 mm wide, attached by the ventral surface to a paper-thin basal membrane. Test thin, tough, outer surface evenly encrusted with fine sand grains and fine shell fragments. Siphons separated by approximately 1.3 mm (1/10th or ¼ of the body length, Michaelsen). Mantle with strong, leathery musculature.

[The section below cannot be correctly rendered as it contains complex formatting. See the image of the page for a more accurate rendering.]

Pharynx with 32 tentacles (26, Michaelsen) of at least 3 orders of size; dorsal tubercle very small; dorsal lamina a plain wide smooth-edged membrane; on each side 14 longitudinal vessels; about 9 wide primary transverse vessels, parastigmata present; stigmatal arrangement of the type, D. L. 6–8/3–4/5–4 —/6–8/9–12E; oesophagus longer than that of T. arenosa; stomach longer than wide (Fig. 3, B3), about ½ the length of the gut loop and with 14 folds and a much curved caecum; intestinal loop with no marked differentiation; anal aperture bi-lobed, smooth-edged.

Endocarps fairly numerous, small irregular sac-like masses scattered over both sides of the mantle.

Atrial velum small, atrial tentacles finger-like, up to 1 mm long.

Gonads in two rows, one on each side of the endostyle; that on the left only slightly shorter than that on the right, composed of 9–13 polycarps, male only; that on the right extending the full length of the zooid, composed of 16–18 polycarps, mainly hermaphrodite but a few male polycarps sometimes included. Hermaphrodite polycarps with male and female gonoducts, male up to 1.5 mm long (2 to 3 times length of testis, Michaelsen), (Fig. 3, B4b). Tadpoles up to 1.7 mm long, 0.5 mm in width in the head region (Fig. 3, B5b), and with a greater number of ampullae than those of T. arenosa.

Distribution. Stewart Island, Port Pegasus, on test of simple ascidians, 25 fathoms, 19/1/15 (Michaelsen); Foveaux Strait, on simple ascidians and molluscan shells (Otago Museum collection, no date).

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Genus Polycarpa Heller, 1877

Simple styelids with small ovate hermaphrodite gonads, often very numerous, irregularly scattered over the inner surface of the mantle wall on both sides of the body, those on the left being for the most part anterior to the digestive canal.

Polycarpa pegasis, Michaelsen. (Fig. 2, D).

Syn. 1922. Polycarpa pegasis Michaelsen, Vidensk Medd. naturh. Foren, bd. 73, pp. 450–453, Fig. 25.

? 1954. Polycarpa pegasis Kott, B.A.N.Z. Ant. Res. Exp., Vol. 1, Pt. 4, p. 146.

Simple ascidians, somewhat globose (their proximity causing lateral compression) attached by the posterior (and lateral) side to seaweeds and shell fragments. Test cartilagenous, clear, yellow, outer region heavily impregnated with fine gray sand grains. Test somewhat warty around the siphons, which were much retracted in all specimens.

Measurements: Length, 12 to 21 mm; breadth, 6 to 7 mm; depth, 11 to 13 mm; distance apart of apertures 8 to 9 mm; thickness of test, 0.5 to 1.0 mm.

Mantle with 50 to 60 simple filiform branchial tentacles, of several orders of size irregularly arranged; opening of dorsal tubercle basically—an elongate broken oval with out-rolled ends (but many variations noted); neutral gland a small round cushion on the right of the nerve cord; dorsal lamina smooth, straight-edged; on each side 4 flattened longitudinal folds; transverse vessels mostly arranged on the simple 13231 plan, where 3 is almost of parastigmatic rank; stigmata up to 6 per mesh, three to four times as long as wide; longitudinal vessels up to 70 on the right, 71 on the left, general arrangement as shown.

Length of Specimen Arrangement of Vessels on the right Total
21 mm E 3(10) 6(14) 3(13) 5(16)—D 70
12 mm E 1(12)8(12)5(12)1(14)—D 65

Intestinal loop a wide open sling (Fig. 2, D). Oesophagus short; stomach short, ovoid, with a marked typhlosole, 17 to 18 folds and no caecum; no distinction in the intestinal region; anal aperture bi-lobed.

Endocarps not present.

Atrial velum narrow, with a circlet of fine filiform tentacles up to 0.3 mm long, 36μ wide in the short swollen basal region.

Gonads forming a narrow band on each side of the endostyle, extending the full length of the body, ovoid in shape. Testis nearest the mantle wall and composed of 1 to 3 (usually 3) paired lobes. Gonoducts very short and opening in any direction. Gonads in 2 to 4 rows up to 45 on the right, 38 on the left. No tadpoles in specimens collected in November, 1907, or January, 1915.

Distribution. Stewart Island. Port Pegasus, 25 fathoms, (19/1/1915) (Michaelsen); Port Pegasus, 15–20 fathoms, (17/11/1907). Elsewhere:? Tasmania (off north-eastern coast, 676–128 metres).

Genus Paramolgula Traustedt, 1885

Branchial sac without folds but with one wide internal longitudinal vessel in the place of each fold. Stigmata more or less bent, some forming irregularly distributed infundibula.

A hermaphrodite gonad on each side, that on the left above the gut loop.

Paramolgula filholi (Pizon) (Fig. 3, C1, C2).

Syn. see: 1922. Paramolgula filholi, Michaelsen, Vidensk. Medd. naturh. Foren, bd. 73, p. 378.

Body globular, attached by posterior end or part of one side. Test smooth, fine sand grains sometimes incorporated in the somewhat rougher regions around the siphons (test only rarely unencumbered, encrusted with sand or shell fragments, Michaelsen). Branchial siphon 6-lobed, atrial 4-lobed. Measurements based on 5 specimens are: length, 2.3 to 3.3 cm (5 cm Pizon); breadth, 1.5 to 2.0 cm; depth, 1.3 to 1.7 cm; distance between apertures, 1.0 to 1.3 cm; thickness of test, 0.5 to 1.0 mm.

Mantle musculature fairly strong on dorsal region—i.e., around the siphons, elsewhere longitudinal musculature represented by strong but well-separated longitudinal bundles, transverse musculature represented by numerous fine strands.

Pharynx with 16 to 20 tentacles of at least 3 orders of size and showing 2 and very occasionally 3 orders of branching; opening of the dorsal tubercle a downwardly pointing horseshoe with inrolled ends; neural gland a small rounded structure just posterior to the dorsal tubercle; dorsal lamina a plain smooth-edged membrane; on each side 7 longitudinal vessels, 5 to 6 primary transverse vessels, parastigmata present; stigmata nearly straight or forming infundibula (Fig. 3, C2). Oesophagus very short, stomach short, surrounded by the.

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branched “liver”. Intestinal loop on the posterior half of the left side, very narrow forming a tightly closed loop the free end of which turns backwards (Fig. 3, C1). Anal aperture somewhat hooded, with 4 to 5 lobes.

Kidney bean-shaped, far back on the right, 3–4 times as long as wide, ventral end not markedly different from dorsal (smaller, Michaelsen; more sharply pointed, Hartmeyer).

Atrial velum smooth-edged 1.0–1.5 mm wide.

Gonads hermaphrodite, that on the left the smaller. Ovary lying next to body wall, only that portion nearest the atrial aperture being exposed. Testis composed of .numerous lobes situated so close together that the testis appears as a compact mass which surrounds the ovary ventrally and laterally. Testis and ovary both with a single gonoduct, openings juxtaposed (Fig. 3, C1).

Distribution. Stewart Island (Pizon); French Passage (Sluiter); Queen Charlotte Sound, 3–10 fathoms, 19/1/1915 (Michaelsen); Stewart Island, Port Pegasus, 25 fathoms, 20/11/1914 (Michaelsen); Half Moon Bay, coastal rocks, 19/11/1914 (Michaelsen); Foveaux Strait (Otago Museum collection, no date).

Note. Van Name (1945) has placed all the somewhat variable South American forms in the one species Paramolgula gregaria (Leson), 1830. This species can be separated from P. gregaria by the presence of only one male gonoduct per gonad, and by the form of the anal opening.

Genus Molgula Forbes and Hanley, 1848

Molgula herdmani, n.sp. (Fig. 3, D).

Body globular, attached by posterior end and occasionally part of one side. Test somewhat warty around the siphons outer layer impregnated with fine sand grains, inner layer opalescent.

Measurements based on the study of 11 specimens are: length, 1.8 to 3.5 cm, breadth 1.0 to 1.8 cm, depth 1.4 to 3.0 cm, distance between apertures 0.9 to 1.7 cm; thickness of test, 0.5 mm (rarely 1.0 mm).

Musculature strong on the anterior ⅓ of the mantle only, elsewhere bundles widely separated.

Pharynx with 16 to 18 tentacles of 3 orders of size, exhibiting 3 orders of branching; opening of dorsal tubercle small C-shaped; neural gland a rounded cushion directly under the nerve cord; dorsal lamina a plain membrane; on each side 6 folds, with longitudinal vessels arranged thus:

Length of Specimen Arrangement of Vessels on the right Total
3.5 cm E–(10)2 (10)2 (11) 2 (11)2 (14) 1 (9)1 D.L. 75
2.5 cm E 1 (5)1 (8)1 (11)1 (11)1 (9)1 (6)1 D.L. 57
2.0 cm E 1 (4)1 (8)2 (10)1 (11)1 (13)1 (10)1 D.L. 64

Stigmata mainly straight Curved stigmata near the summit of the folds and near the endostyle. Intestinal loop ⅞ of body length. Oesophagus very short; stomach very short, surrounded by “liver” except on left side; intestine smooth, narrow loop open only at reflected end; anal aperture smooth-edged.

Kidney, bean-shaped, far back on right.

Atrial velum, narrow, edge with small, shallow scalloping or nearly smooth.

Gonad on left parallel with gut loop and lying between it and the siphonal apertures, gonad on right above kidney but extending around and below the anterior end of the kidney. Ovary medially placed among testis lobes Gonoducts opening towards the atrial aperture, opening of sperm duct rather more variable in position than opening of oviduct (Fig. 3, D). No tadpoles present in specimens collected 10/4/49 and 6/1/51.

Distribution. Stewart Island, Half Moon Bay, coastal rocks, 10/4/49, 6/1/51.

Type Specimen. In the Otago Museum.

Remarks. In the shape and position of the gonads and in the presence of longitudinal vessels between the folds, this species differs from all previously described from New Zealand waters.

Discussion

As far as is known at present the distribution in New Zealand of the 58 species recorded from Stewart Island waters is as follows:—

Twenty-seven species occur along the coast of all three islands—North, South and Stewart Islands.

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Fifteen species have been found on the coast of only the two most southerly islands—South and Stewart Islands.

Sixteen species (including six new species) are recorded only from the most southerly island—Stewart Island.

Of the 16 species recorded in New Zealand from the Stewart Island region only, as far as is known at present, the distribution is as follows:—

Ten species are endemic—Polyclinum novaezelandiae, Macroclinum stewartense, Pseudodistoma sigillinoides, Leptoclinides novaezelandiae, Trididemnum sluiteri, Ascidia lagena, Botryllus stewartensis, Theodorella stewartensis and Molgula herdmani.

Two (perhaps 3) species are circum-south-polar—Didemnum studeri f. typica, Didemnum studeri var. africanum and perhaps Trididemnum cerebriforme which is known at present only from South Africa and Stewart Island.

Two species are present also in the Chatham Islands fauna—Didemnum mortenseni and Didemnum lithostrotum. These presumably, along with three other species recorded from the southern end of the South Island of New Zealand and/or Stewart Island, have reached the Chatham Islands in the sweep of cool sub-antarctic water which flows up past the south-east coast of New Zealand (Deacon, 1937).

Two species have doubtful affinities with Australia—Perophora boltenina (which Michaelsen (1922) very diffidently linked with Perophora hutchinsoni from New South Wales, noting that the original description of P. hutchinsoni was by no means full and that at least in several respects the divergent form from Stewart Island should be considered as a separate variety), Polycarpa pegasis, which Kott (1954) records from material dredged off the north-eastern coast of Tasmania. This species was previously known from material dredged off the south-eastern coast of Stewart Island, and has not been identified in any of the extensive collections of ascidians from other parts of New Zealand investigated by the author. By the direction of flow of the ocean currents between Stewart Island and Tasmania (Dannevig, 1907; Deacon, 1937; Svedrup, Johnson and Fleming, 1942; C. Fleming, 1944), it would appear that there is little likelihood of exchange of material between these two islands, and though it is possible that the species may be circum-south-polar so far there has not been any indication of the occurrence of Polycarpa pegasis in other sub-antarctic regions.

The present paper extends the known southerly range in New Zealand of the following 21 species:—

Amaroucium thomsoni, Amaroucium adamsi, Amaroucium benhami, Amaroucium thomsoni, Amaroucium foliaceum, Dumus areniferus, Didemnum psammatodes var. maculatum, Didemnum albidum, Didemnum lithostrotum, Diplosoma macdonaldi, Polycitor (Eudistoma) circumvallatum, Cystodytes dellachiaiae, Ascidiella aspersa, Botryllus magnicoecus, Botryllus schlosseri, Alloeocarpa minuta, Cnemidocarpa nisiotis, Pyura suteri, Pyura cancellata, Pyura picta, Pyura carnea.

Explanation of Lettering
c caecum d sperm duct
e endocarp ♀ hermaphrodite polycarp
ilv internal longitudinal vessel ♂ testis
k kidney ♀ ovary
o oviduct

References

These include those given in the previous papers of the series, together with:

Brewin, B. I., 1956. “Ascidians from the Chatham Islands and the Chatham Rise,” Trans. Roy. Soc. N.Z., Vol. 84, pp. 121–137.

—— 1957. “Ascidians of New Zealand, Part X—Ascidians from North Auckland,” Trans. Roy. Soc. N.Z., Vol. 84, pp. 577–580.

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Carlisle, D. B., 1953. “Notes on the British Species of Trididemnum, with a Report of the Occurrence of T. niveum (Giard) in the Plymouth Area,” J. Mar. Biol. Ass. U. K., Vol. XXXI, pp. 439–445.

Deacon, G. E. R., 1937. “The Hydrology of the Southern Ocean,” Disc Repts., Vol. XV, pp. 1–124.

Dannevig, H. C., 1907. “On Some Peculiarities in our Coastal Winds and their Influence upon the Abundance of Fish in Inshore Waters,” Proc. Roy. Soc. NSW, Vol XLI, pp. 27–45.

Fleming, C. A., 1952. “A Foveaux Strait Oyster Bed,” N. Z. J. Sci. Tech., Sec. B, Vol. 34. pp. 73–85.

—— 1944. “Evidence of Pliocene Climatic Change,” Trans. Roy. Soc. N. Z., Vol. 74. pp. 216–

Harant, H., 1931. “Contribution à l'histone naturelle des ascidies et de le parasites,” Ann. Inst. Océanogr. Monaco, Vol. M. pp. 231–389.

Kott, P., and Thompson, H., 1954. “Tunicata. B.A.N.Z. Antarc. R. Exp. 1929–1931” Repts. Ser. B, Vol. 1, pp, 1–184.

Kott, P., 1957. “Ascidians of Australia II,” Aust. J. Mar. Fresw. R., Vol. 8 pp. 64–109.

Pizon, A. 1898. “Révision des Tuniciers du Muséum (Famille des Molgulidées)”. in: Bull. Mus. Paris. IV, pp. 272–274.

Redikorzev, V., 1914. “Neue Ascidien,” Zool. Anz., Vol. 43, pp. 204–213.

—— 1927. “Zehn neue Ascidien aus dem Fernen Osten,” Zool. Jahrb. Syst., Vol. 53. pp. 373–404.

Sverdrup, H. U., Johnston, M. W., Fleming, R. H., 1942. The Oceans, New York: Prentice Hall Inc.

Dr. Beryl I. Brewin.


University of Otago.
New Zealand.