Ascidians from Otago Coastal Waters
[Read by title before Otago Branch, July 13, 1948; received by the Editor, July 22, 1948; issued separately, February, 1950.
The material which forms the basis of the present paper was collected by Captain Black of the trawler Taiaroa off Oamaru, approximately eight miles from the shore and at a depth of forty to fifty fathoms, and by the author from coastal rocks near Pipikaretu, on the ocean side of the Otago Peninsula. Nineteen species of ascidians living under sheltered conditions in the Otago Harbour are described in a previous paper (Brewin, 1946) and in this paper full descriptions are given only of species not previously recorded, the local range of variation alone being given for the others, and likewise generic characters are given only for those genera not previously described. The author's thanks are especially due to Captain Black for the speedy delivery of material which reached the department in a living condition and could be observed in a fully expanded state in the aquaria.
List of Species Described
1. Amaroucium oamaruensis n.sp. 40–50 fths., off Oamaru
2. Didemnum candidum Savigny "
3. Corella eumyota Traustedt "
4. Cnemidocarpa stewartensis Michaelsen "
5.Cnemidocarpa bicornuata (Sluiter) "
6. Pyura picta n.sp. "
7. Pyura cancellata Brewin "
8. Pyura suteri Michaelsen "
9. Molgula sluiteri (Michaelsen)
Description of Species
Explanation of Lettering
- atr., atrial opening
- av., atrial velum
- br., branchial opening
- ecp., endocarp
- g., gonad
- l., “liver”
- n., kidney
- se., sperm duct
- st., stomach
- ♂ ovary
- ♀ testis
Family Synoicidae Hartmeyer, 1908
Genus Amaroucium (Milne-Edwards), 1841
Amaroucium oamaruensis n.sp. (Text-fig. 1)
Small, flat-topped, irregularly shaped colonies of this species were found on skeletal tubes of Tubularia dredged from 40–50 fathoms off Oamaru. The largest colony in the present collection measures 6 mm. in height and 13 mm. in the longest diameter. The test is a light yellow in colour, but the colouring is masked by the numerous small grey particles of sand incorporated in the outer layer. There is no tendency to mound formation around the common cloacal apertures, which are small and inconspicuous, the largest being 1·5 mm. in diameter. The test is composed of a firm, transparent substance and contains many small test cells.
Zooids measure up to 9 mm. in length and 0·5 mm. in width in the pharyngeal region. The post-abdomen is long, occupying two-thirds of the body length in fully expanded zooids. The branchial aperture is surrounded by six distinct triangular lobes, but the atrial aperture has no protecting lappets. The wall of the pharynx is broken by 16–18 (usually 17) rows of 9–11 stigmata, two to three times as long as they are wide. Ten fine muscle bundles run down the wall of the pharynx to the end of the post-abdomen. Branchial tentacles are 16 in number and of three orders of size, regularly arranged, and of these the longest are almost four times the length of the shortest. The dorsal lamina is composed of short curved languets. The oesophagus is short and leads to a short rounded stomach bearing four longitudinal folds. The intestine is wide and passes backwakwards for a distance before turning to run up to open one third of the way up the pharyngeal wall. The testis occupies the posterior half of the postabdomen and is composed of 12–18 very large lobes. The sperm duct is a much coiled structure which runs straight up towards the atrial aperture. Ovaries canot be discerned in any of the specimens to hand.
Distribution: 40–50 fathoms, off Oamaru.
Remarks: From a careful survey of the literature of this genus it is apparent that the species described is not identical with any previously described.
Type in the Otago Museum.
- Family Didemnidae Verrill, 1871
- Genus Didemnum Savigny, 1816
Didemnum candidum Savigny
Synonymy and literature: 1924, Didemnum candidum, Michaelsen, Vidensk. Medd. naturh. Foren., bd. 77, pp. 358, 359.
This species was found on the tests of other ascidians and on the skeletal tubes of Tubularia dredged at 40 or 50 fathoms off Oamaru, but no specimens showed any features not covered by previous descriptions.
Family Rhodosomatidae Hartmeyer, 1908
Genus Corella Alder and Hancock, 1870
Corella eumyota Traustedt
Synonymy and literature: 1945, Corella eumyota, Van Name, Bull. Amer. Mus. Nat. Hist., vol. 84, p. 212.
The few specimens that were found in among the material dredged from 40 to 50 fathoms off Oamaru showed no differences from those described from Otago Harbour (Brewin, 1946, p. 110).
Family Styelidae Sluiter, 1895
Genus Cnemidocarpa Huntsman, 1913
Cnemidocarpa stewartensis Michaelsen (Text-fig. 2)
Synonymy: 1922, Cnemidocarpa stewartensis, Michaelsen, Vidensk. Medd. naturh. Foren., bd. 73, p. 435.
Specimens were collected from 40 to 50 fathoms off Oamaru and were found singly or in groups of two or three on the shells of lamellibranchs (especially those of Pinna) and gasteropods, on the tests of ascidians and on the skeletal tubes of Tubularia. The smaller specimens (Text-fig. 2, B1) are hemispherical in shape, bright orangy-red in colour, and possess a finel wrinkled test, whereas the larger specimens (Text-fig. 2, B2) are nearly spherical in shape, browny-red in colour, and possess a test that is finely wrinkled and covered by numerous short hair-like growths. Michaelsen's specimens are described as yellowish or browny-grey in colour, but as he was dealing with preserved specimens, the colour differences are quite understandable. The siphonal region is centrally situated and the siphons are separated by between one-half and one-third of the body length. Attachment is by the ventral surface. The test is free from incrusting plants and animals. The internal linings of the siphons are reddish-purple with eight internal
longitudinal bands, four of a darker shade of the same colour and four of a light cream colour. Measurements based on the study of twenty-five specimens are: length, 1·0 to 3·0 cm.; breadth, 1·3 to 2·3 cm.; depth, 0·8 to 2·9 cm.; distance between the apertures, 0·8 to 1·2 cm.; branchial siphon, 0·3 to 0·8 cm. long, 0·3 to 0·6 cm. wide; atrial siphon, 0·3 to 0·7 cm. long, 0·2 to 0·5 cm. wide; thickness of test, 0·5 to 1·0 mm.
The mantle wall is cream in colour and the musculature is not very well developed, muscle bundles reaching only one-half or two-thirds of the way down the body. On each side of the pharynx there are four longitudinal folds, of which that nearest the endostyle is usually the smallest. Longitudinal vessels number from 94 to 163 on the right side and from 93 to 160 on the left side and the general arrangement is as follows:—
|Length of specimen||Arrangement of vessels on the right||Total|
|2.0 cm.||E.6 (16) 9 (30) 8 (26) 8 (20) 5D.L.||128|
|2.2 cm.||E.8 (22) 8 (32) 6 (32) 5 (26) 4D.L.||143|
|3.0 cm.||E.7 (23) 11 (32) 10 (33) 7 (32) 6D.L.||161|
Transverse vessels are irregularly arranged, there being up to 7 small vessels between two large, and parastigmatic vessels are usually present. There are 5 to 7 stigmata per mesh between the folds and up to 10 per mesh near the endostyle and the dorsal lamina. The branchial tentacles are short, filiform structures, 32 to 50 in number and of three or four orders of size not regularly arranged. The dorsal tubercle is small and the opening is in the majority of cases horseshoe shaped with inrolled horns, though numerous variations on this plan occur. The neural gland is a small, round structure lying to the right of the very short nerve cord. The dorsal lamina is a smooth untoothed membrane. The gut loop occupies the entire width of the left side of the body and extends halfway up it. The oesophagus is short and narrow and leads to a wide elongated stomach, the wall of which bears from 24 to 28 internal longitudinal folds and a typhlosole. There is no pyloric caecum. The intestinal loop takes a sharp turn just after it starts on its recurving course and in extreme cases the gut in this region makes a complete turn of a spiral. The intestinal region then runs close to and occasionally under the stomach and finally narrows in the anal portion. The anal aperture has 12 to 14 distinct lobes. The wall of the atrial siphon is provided with numerous fine filiform tentacles which are scattered along the entire length. Endocarps, approximately 60 on each side, are small and scattered over all free portions of the inner surface of the mantle.
The gonads are long, much-coiled structures, usually three in number on the right side and two in number on the left side. Specimens were found with two and four gonads on the right side and one and three gonads on the left side, and in six specimens forking occurred in one or more gonads. Testis lobes lie between the ovary and the body wall and ducts from the testis pass from both sides of the gonad to form the vas deferens. The gonoducts open near and towards the atrial aperture. Tadpoles were not present in any of the specimens which were collected in the months of April, May and June, 1948.
Distribution: In New Zealand—25 fths. Port Pegasus and 5–15
fths. Paterson Inlet, Stewart Island (Michaelsen); 40–50 fths. off Oamaru.
Remarks: In the essential factors, especially those of gut and gonad arrangement, the specimens described above are in close agreement with Michaelsen's description. In the count of longitudinal vessels and in the number of vessels between the folds there is a certain amount of discrepancy [E.4 (17) 5 (22) 5 (20) 2 (22) 2D.L., Michaelsen] and also in the outer covering, Michaelsen having described some of his specimens as covered by small pin-headed papillae. The latter were not seen in any specimens in the present collection, but, as Michaelsen had only a few specimens at his disposal, it is quite likely that they belong in one of the extremes of the range of variability of the species and a survey of many more specimens is necessary before the full range of variability will be known.
Cnemidocarpa bicornuata (Sluiter)
Synonymy and literature: 1922, Cnemidocarpa bicornuata, Michaelsen, Vidensk. Medd. naturh. Foren., bd. 73, p. 440.
The numerous specimens of C. bicornuata dredged at 40 to 50 fathoms off Oamaru differ from those described from the Otago Harbour (Brewin, 1946) in that (1) the body colouring is much lighter, dredged specimens being pale buff with four magenta bands on the whole of the inner and half of the outer lining of the siphons, (2) the average body size is much greater, some dredged specimens being one and a half times as large as the largest from Otago Harbour, and (3) the gut loop is shorter (one-third to one-half of the body length) than that of those from the harbour (one-half of the body length) and than those from the Hauraki Gulf (one-half to two-thirds of the body length (Brewin, 1948). In all other respects the present specimens fall within the range of variability given for the specimens from Otago Harbour.
Distribution: In New Zealand—French Pass (Sluiter), Firth of Thames (Quoy and Gaimard); ? Queen Charlotte Sound (3 to 10 fths.), Stewart Island (5 to 14 fths.) (Michaelsen); Otago Harbour, Hauraki Gulf (Brewin); 40 to 50 fths., off Oamaru. Elsewhere—? Chatham Islands (Sluiter).
Family Pyuridae Hartmeyer, 1908
Genus Pyura Molina, 1782
Pyura picta n.sp. (Text-fig. 3)
This is the most commonly found ascidian among the material dredged from 40 to 50 fathoms off Oamaru. It occurs singly or more often in clumps and is attached to the shells of various molluscs, tests of other ascidians and to the skeletal tubes of Tubularia. The body is pear-shaped (Text-fig. 3 B), the branchial aperture being terminal and the atrial sub-terminal, removed from it by approximately one-third of the depth of the animal. Attachment is ventral and may involve portions of the sides as well. The test is a dirty pale yellow in colour and the surface bears an irregular network of ridges which confers a honeycomb-like appearance on the test. The test is very thin but tough and leathery. The internal linings of the siphons are white in colour, edged by a narrow band of pale pink pigment
and broken by four narrow longitudinal bands of the same pigment. In a few specimens the test forms a holdfast for small Spirula tubes, polyzoa, hydroids, sponges and compound ascidians, but in no case is the body obscured by them. Measurements based on the study of twenty-five specimens are: length, 1·8 to 2·7 cm., breadth, 1·5 to 2·0 cm.; depth, 2·8 to 4·5 cm.; distance between the apertures, 1·0 to 2·0 cm.; branchial siphon, 4·0 to 6·0 mm. long, 2·0 to 3·5 mm. wide; atrial siphon, 2·5 to 4·0 mm. long, 1·8 to 3·2 mm. wide; thickness of test, 0·4 to 0·8 mm.
Text-fig. 3—Pyura picta. (A) Dissection showing body opened from the ventral surface, pharynx removed. X 2.5. (B) Individual specimen. X 0.7. (C) Spinules. X 340.
The mantle wall is a light cream in colour and the musculature is very well developed. Siphonal spinules measure on the average 0·011 mm. in length and 0·006 mm. in width. On either side of the pharynx there are seven complete longitudinal folds and in most cases an additional incomplete one near the endostyle. Longitudinal vessels number from 122 to 167 on the right side and from 124 to 171 on the left side and the general arrangement is as follows:
|Length of specimen||Arrangement of vessels on the right||Total|
|1.7 cm.||E.–(3) 1 (9) 3 (10) 3 (16) 3 (18) 3 (19) 3 (15) 2 (14)–D.L.||122|
|1.8 cm.||E.–(3) 2 (16) 3 (17) 4 (23) 3 (23) 3 (24) 2 (18) 2D.L.||143|
|2.5 cm.||E.1 (4) 2 (12) 3 (17) 1 (16) 2 (21) 3 (23) 3 (22) 3 (19) 3D.L.||155|
|2.0 cm.||E.–(7) 2 (12) 2 (20) 2 (22) 2 (24) 2 (25) 2 (24) 2 (17) 2D.L.||167|
There are from five to seven small transverse vessels between two larger ones, and seven to ten stigmata in the meshes between the folds. The stigmata are four to six times as long as they are broad. Branchial tentacles are branched, 28 to 44 in number and are of three orders of size, not regularly arranged. Primary and secondary branches are present. In the majority of the specimens the opening of the dorsal tubercle is in the shape of a horseshoe with inrolled ends, but many variations on this shape occur. The neural gland is a narrow elongate structure lying close to the nerve cord. The dorsal lamina is composed of from 40 to 67 short curved languets and there is no correlation
between the number of languets and the length of the body. The gut loop is wide and occupies slightly more than the posterior half of the left side of the body. Very little difference in width is shown between the various parts of the gut. The anal aperture is finely lobed. The “liver” is composed of five finely divided lobes, that nearest the intestine being the largest. The atrial velum is narrow (average width 0·5 mm.) and has a faintly scalloped edge.
There is one long gonad on each side except in one specimen which has a very small extra gonad on the right side of the body. The gonoducts open near the atrial aperture. The gonad on the right is divided into 24 to 36 and that on the left into 20 to 35 hermaphrodite lobes, the ovarian portions of which are purple in colour and the testicular portions of which are cream in colour. The lobes on both sides are arranged in an irregular double row. Tadpoles are not present in any of the specimens which were collected in April, May and June, 1948.
Distribution: 40 to 50 fths. off Oamaru.
Remarks: This species is not identical with any previously recorded from the New Zealand area and as far as can be ascertained from a careful survey of the literature is not identical with any species previously described.
Type Specimen: Otago Museum.
Pyura cancellata Brewin
Synonymy and literature: 1946, Pyura cancellata, Brewin, Trans. Roy. Soc. N.Z., vol. 76, p. 121.
1948, Pyura cancellata, Brewin, Trans. Roy. Soc. N.Z., vol. 77, p. 134.
A few specimens were present in the material dredged from 40 to 50 fathoms off Oamaru, but no specimens showed any features not covered by the description given for specimens from Otago Harbour.
Pyura suteri Michaelsen
Synonymy and literature: 1908, Pyura (Halocynthia) subuculata var. suteri, Michaelsen, Naturh. Mus. Hamburg, p. 259.
1946, Pyura subuculata, Brewin, Trans. Roy. Soc. N.Z., vol. 76, p. 119.
Specimens of this species found on the wave-beaten coastal rocks at Pipikaretu, on the ocean side of the Otago Peninsula, showed no features not previously described for specimens from Otago Harbour.
Family Molgulidae Lacaze-Duthiers, 1877
Tentacles almost always branched; branchial sac generally with well-developed folds, bearing internal longitudinal vessels; stigmata especially those on the folds usually curved and arranged in spirals, straight stigmata being exceptional in the family; kidney present on the right side of the body; gonads hermaphrodite, one on each side of the body.
Genus Molgula Forbes and Hanley, 1848
Branchial sac with folds each bearing several or many internal longitudinal vessels. Stigmata more or less curved or spiral, especially on the summits of the folds. Gonads hermaphrodite, one on each side of the body, the left gonad anterior to the primary intestinal loop.
Molgula sluiteri (Michaelsen) (Text-figs. 4 and 5)
Synonymy and literature: 1900, Molgula martensi (err. not M. martensi Traustedt), Sluiter, Tunic. aus dem Stillen Ocean, p. 32.
1922. Ctenicella sluiteri, Michaelsen, Vidensk Medd. naturh. Foren., bd. 73, p. 373.
A few single specimens, but mainly clumps (Text-fig. 5 B) of this species were found in pools on the wave-swept coastal rocks at Pipikaretu, on the ocean side of the Otago Peninsula. Some of the clumps measure 4 in. in diameter and the individuals forming the clump are usually forced into a quadrilateral or hexagonal shape by the pressure of the neighbouring individuals (Text-fig. 5 B). The entire surface of the test of each individual is impregnated with fine sand grains (Text-fig. 4 B) and often the entire clusters are partly covered by sand. The dorsal surface of each ascidian is flattened and bears the two apertures, the branchial being more or less central in position and the atrial, which is slightly longer, being near the periphery. The branchial siphon has six short rounded lobes, and the atrial four, and in addition the branchial has six fine pointed tentacles on the inner edge of the rim. The basic colouring of the test is a light yellow and the internal lining of the siphons is tinged with purple pigment. The test is very thin, but tough and leathery. Attachment is ventral and involves most of the sides as well. Measurements based on the study of 25 specimens are: length, 0·6 to 1·4 cm.; breadth, 0·7 to 1·0 cm.; depth, 0·8 to 2·2 cm.; distance apart of the apertures, 0·45 to 0·6 cm.; branchial aperture, 1·5 to 3·0 mm. long, 0·7 to 1·0 mm. wide; atrial aperture, 2·0 to 4·0 mm. long, 0·7 to 1·0 mm. wide; thickness of the test, 0·4 to 0·8 mm.
Text-fig. 4—Molgula sluiteri. (A) Dissection showing body opened from the ventral surface, pharynx removed. X 5.0. (B) Individual specimen. X 1.0.
The mantle wall is light yellow in colour with flecks of purple pigment in the more dorsal regions and the musculature is not well developed. The circular muscles extend only slightly below the siphonal regions and the longitudinal (18 to 24 fine, well-separated bundles) do not reach more than halfway down the body. On either side of
the pharynx there are seven longitudinal folds, of which those third, fourth and fifth from the dorsal lamina are usually the largest. The longitudinal vessels are arranged in a very regular pattern, viz.:
|Arrangement of vessels on the right||Total|
|E. (3) 0 (4) 0 (4) 0 (4) 0 (4) 0 (4) 0 (3)–D.L.||26|
|E. (2) 0 (3) 0 (3) 0 (3) 0 (3) 0 (3) 0 (2) D.L.||19|
Eighty per cent. of the specimens examined showed the arrangement given in the top line. There are from five to seven small transverse vessels between two large ones. In the meshes between the folds there are numerous short curved stigmata and occasionally spiral formations, though these are more usually present only on the top of the folds. Branchial tentacles are branched, 28 to 36 in number (average number 32), and are of two orders of size fairly regularly arranged. Short primary and very short secondary branches are present. In most specimens the opening of the dorsal tubercle is a recumbent S-shaped structure. The neural gland is a small round cushion lying to the right of the extremely short nerve cord. The dorsal lamina is a wide membrane, which in many specimens is continued back along the left side of the oesophageal opening. In some specimens this posterior region is toothed in the manner described by Michaelsen (1922, p. 377). The gut loop (Fext-fig. 4 A) is composed of a short narrow oesophagus, a long narrow stomach bearing a much-divided green hepatic organ which is more massive on the inner side of the stomach than on the outer side, and a long narrow intestine which runs up to a point about halfway up the body wall before bending back to run very close to the wall of the stomach and then up to the atrial aperture. The anal opening has a smooth, straight edge. The kidney is sausage-shaped and lies on the right side of the body. In the majority of specimens small concretions were enclosed in the kidney. The atrial velum is a straight-edged structure, 1 mm. in width.
One hermaphrodite gonad is present on each side, that on the right lying anterior to the kidney and that on the left lying anterior to the gut loop. The ovaries are long thin structures and the testes are connected only to the wider posterior ends of them. Gonoducts open near the endostyle. Tadpoles are present in the mantle cavity of nearly all the specimens which were collected at Pipikaretu in March, 1947, and also in specimens collected from Stewart Island in May, 1946.
Tadpoles (Text-fig. 5 A) are tailed and the largest measures 1 mm. in length and 0–15 mm. in width in the head region.
Distribution: In New Zealand—Foveaux Strait (Michaelsen), Otago coastline. Elsewhere—Chatham Island (Sluiter).
Remarks: The specimens described by Michaelsen come within the range of variability given for the specimens in the present survey.
Copepods of the family Notodelphidae were found in the branchial sac of Molgula sluiteri.
In this paper an account is given of seven species dredged at 40 to 50 fathoms off Oamaru and of two species found on coastal rocks on the ocean side of the Otago Peninsula. Two new species are described, Amaroucium oamaruensis and Pyura picta.
These include all those given in “Ascidians in the Vicinity of the Portobello Marine Biological Station, Otago Harbour,” Brewin, Trans. Roy. Soc. N.Z., vol. 76, pp. 130, 131, as well as the following:
Brewin, B. I., 1948. Ascidians of the Hauraki Gulf. Pt. 1. Trans. Roy. Soc. N.Z., vol. 77, pp. 115–138.
Van Name, W. G., 1945. The North and South American Ascidians. Bull. Amer. Mus. Nat. Hist., vol. 84, pp. 1–476.