3.Note on the Species of Hydra found in New Zealand.
Communicated by Dr. Chas. Chilton.
[Read before the Philosophical Institute of Canterbury, 12th July, 1911.]
Very little appears to have been published on the species of Hydra found in New Zealand. The first definite record was made in 1867 by Dr. Coughtrey,* who found a specimen in a stream near Dunedin. In his note he says, “This Hydra, in general form, is like H. viridis, in colour pale brown, and has seven tentacula, which are peculiar in this respect, that they are distinctly annulated and each ring is fringed.” No name was given to this species by Coughtrey. In an earlier paper he says in a footnote, “I have seen two Hydrae in New Zealand, one nearly like H. viridis of Britain, and the
[Footnote] * Coughtrey: “Critical Notes on New Zealand Hydroida.” Ann. Mag. Nat. Hist., ser. 4, vol. 17, p. 22; 1867.
other I have not been able to identify with the British members of Gymnochroa.”*
In 1879 Mr. A. Hamilton,† in a paper on fresh-water Polyzoa, incidentally mentioned the occurrence in a swamp near Napier of “a large reddish-brown Hydra.” The next record is by Farquhar,‡ who, in 1896, published a catalogued list of the New Zealand Hydroida. In his list he mentions only one Hydra—i.e., the one which Coughtrey had described as above. Unfortunately, he calls it H. viridis, evidently misreading Coughtrey's description. Under this name it appears in the “Index Faunae Novae-Zealandiae.”§
In 1910 Dr. W. B. Benham∥ published a note on “A Species of Hydra new to New Zealand,” which was found in the Shag Valley, and which, he said, was characterized by a rich reddish-brown, almost mahogany, colour, and by the great size (up to 15 mm.). He also refers to a small brown species found near Dunedin, probably the same as the one mentioned by Coughtrey.
In addition to the published facts referred to above, Dr. Hilgendorf, Professor Thomas, Professor Kirk, and Dr. Chilton have kindly contributed information as to the occurrence of species of Hydra in New Zealand.
Dr. Hilgendorf has seen a small brown form which occurs in ponds at Woodhaugh, near Dunedin. This is probably the same as the brown species of Coughtrey and Benham.
Professor Kirk writes that there appear to be two kinds in Wellington, one a dark-brown form, and the other a light-brown one. Professor Thomas says that Hydra appears to be widely distributed about Auckland, and notes the occurrence of the following: (1) a brownish or yellowish-brown form; (2) a form of a colour to suggest orange; (3) a nearly colourless form; (4) a green species. He considers (1) to be the form commonly called H. fusca, and (2) and (3) to be colour-varieties of it. The forms noted by Professor Kirk and Dr. Hilgendorf probably belong to this species also.
In 1885 Dr. Chilton in his manuscript note-book recorded the appearance of a Hydra in Christchurch. The animal observed was light brown in colour, and appeared to him to be the same as the form commonly known as H. fusca.
Specimens of a brown Hydra have, for several years past, been obtained in moderate numbers from the River Avon, for use in the biological laboratory at Canterbury College, though until lately no green ones were seen. But in April of this year, while searching for Hydra in water from the River Avon, several green specimens were discovered. These forms agree exactly, in the characters that can be observed, with the descriptions given of H. viridis. The gonads, however, have not been seen.
According to Hickson,¶ three species of Hydra are known in England —viz., H. viridis Linn., H. oligactis Pall. (= H. fusca Linn.), H. vulgaris Pall. Hickson gives a short description of each of these species.
A comparison of the forms found in New Zealand with these and other descriptions shows that the green species observed in Christchurch is certainly H. viridis, and the green form noted by Professor Thomas at Auckland probably must be placed here also. It seems likely that the Shag Valley
[Footnote] * Trans. N.Z. Inst., vol. 8, p. 299; 1876.
[Footnote] † Hamilton: “On Melicerta ringens and Plumatella repens.” Trans. N.Z. Inst., vol. 12, p. 303.
[Footnote] ‡ Farquhar: Trans. N.Z. Inst., vol. 28, p. 468; 1896.
[Footnote] § Index Faunae Novae-Zealandiae,” edited by F. W. Hutton, London; 1904
[Footnote] ∥ Benham: Proc. N.Z. Inst. for 1909, part iv, p. 128; 1910.
[Footnote] ¶ Hickson: “Cambridge Natural History,” vol. 1, Coelenterata, p. 256; 1906.
specimens described by Dr. Benham are representatives of H. vulgaris, though this cannot be decided with certainty till they have been examined more closely. The large reddish-brown form noted by Hamilton will probably also belong to this species. The light-brown species mentioned above as found at Dunedin, Christchurch, &c., appears to belong to the well-known brown Hydra of Europe, commonly referred to as H. fusca. This should, however, be called H. oligactis, this being the name first given to the species by Pallas. It seems to be the most common species in New Zealand, having been seen in Christchurch, Wellington, Auckland, and Dunedin. Coughtrey's species evidently belongs here too.
The New Zealand species now known of Hydra, then, are H. viridis, H. vulgaris, and H. oligactis.
Hydra viridis Linn.
Hydra viridis Linn., Sys. Nat., 12th ed., p. 1320, 1767; Johnston, British Zoophytes, p. 121, 1847; Hincks, British Hydroid Zoophytes, p. 312, 1868; Hickson, Camb. Nat. Hist., vol. 1, p. 256, 1906; Brauer, Zool. Anz., vol. 33, p. 790, 1909.
Dr. Brauer says that the correct name for this species should be H. viridissima Pall. (1766), but the name H. viridis is so well known and commonly accepted that it would be inconvenient to alter it; and, moreover, it was used by Linnaeus for this form in the 10th edition of the Systema Naturae, though not definitely as a specific name. In this edition Linnaeus gave all the forms of Hydra under the one name, H. polypus, and it was not until the 12th edition that he divided them up into separate species.
Hickson describes this species thus: “Colour grass-green. Average number of tentacles, eight. Tentacles shorter than the body. Embryonic chitinous membrane spherical and almost smooth.”
The specimens from the River Avon agree closely with the descriptions given by Hickson, Johnston, and Hincks. The species is now known in New Zealand from Christchurch and Auckland.
? Hydra vulgaris Pallas.
? Hydra vulgaris Pallas, Elench. Zooph., p. 30, 1766; Hickson, Camb. Nat. Hist., vol. 1, p. 256, 1906. Hydra (“reddish-brown species”), Hamilton, Trans. N.Z. Inst., vol. 12, p. 303, 1879; Benham, Proc. N.Z. Inst., 1909, p. 128, 1910.
Hickson's description is as follows: “Colour orange-brown. Tentacles rather longer than the body, average number six. Embryonic chitinous membrane spherical and covered with numerous branched spines.” Brauer adds that the proximal end of the body is not narrowed into a stalk, that four kinds of thread-cells are present, and that the animal is hermaphrodite.
Habitat.—Shag Valley, Dunedin; Petane Valley, Napier.
I have not seen specimens of this species.
Hydra oligactis Pallas.
Hydra oligactis Pallas, Elench. Zooph., p. 29, 1766; Johnston, British Zoophytes, p. 124, 1847; Hincks, British Hydroid Zoophytes, p. 315, 1868; Hickson, Camb. Nat. Hist., vol. 1, p. 256, 1906; W. M. Sale, Cat. Austral. Hyd. Zooph., p. 187, 1884; Brauer, Zool. Anz., vol. 33, p. 792, 1909; H. fusca Linnaeus, Sys. Nat., 12th ed., p. 1320. 1767; H. viridis Farquhar, Trans. N.Z. Inst., vol. 18, p. 468, 1896; Hutton, Index Faunae N.Z., p. 321, 1904.
“Colour brown. Tentacles capable of great extension, sometimes, when fully expanded, several times the length of the body. Average number, six. Embryonic chitinous membrane plano-convex, its convex side only covered with spines.”—(Hickson.)
Habitat.—Christchurch, Wellington, Auckland, and Dunedin.
In the paper by Dr. Brauer referred to above H. oligactis is divided into two species—viz., H. oligactis Pall. and H. polypus Linn. The defining characters given by him are,—
“H. oligactis Pall. Stalked, tentacles very long. Body 2–3 cm. long. Three kinds of thread-cells, sexes separate, testes on all parts of the body except the stalk. Eggs usually adhering in groups, spherical, and covered with very short spines. Colour grey, brown, or red.”
“H. polypus Linn. Stalked, body not more than 2 cm. long, usually 1–1-5 cm. Four kinds of thread-cells. Hermaphrodite, testes only in distal third of body, eggs attached singly with under-surface smooth, upper convex and covered with short spines. Colour grey or brown.”
The brown forms I have examined seem to belong to H. oligactis. Only three kinds of thread-cells can be made out, the three kinds apparently corresponding to those described by Brauer as occurring in H. oligactis. It has not been possible, however. to examine the gonads in these forms, and until this is done their identity must remain to a certain extent doubtful.
Of the specimens found near Melbourne, Mr. W. M. Sale observes that “the attenuation of the lower part of the body is by no means so conspicuous as shown in Mr. Hinck's figures of the English species.” This, too, is the case with most of the specimens of H. oligactis seen in Christchurch.
It is to be noted that all the specimens of Hydra in New Zealand seem to have been found near habitations. I have not heard of any having been found in spots where the possibility of introduction by man could be excluded. The consideration of this, and the fact that the New Zealand species are apparently the same as those found in Europe, seem to lead to the conclusion that Hydra is not indigenous to New Zealand, but has at some time or other been accidentally introduced.