Art. XIII.—The Fresh-water Amphipoda of New Zealand.
[Read before the Philosophical Institute of Canterbury, 4th November, 1908.]
The immediate cause of this paper was the discovery in February, 1908, of a fresh-water gammarid at Rona Bay, Wellington Harbour, which, on examination, proved to be the same as Phreatogammarus propinquus, a species described in 1907 from a single specimen collected by Mr. Crosby Smith on Mount Anglem, Stewart Island. This species was of special interest as the first species of Phreatogammarus to be recorded from the surface waters of New Zealand, and owing to its near relationship to P. fragilis, a species inhabiting the underground waters of the Canterbury Plains. During the last few years, too, several facts referring to the other freshwater Amphipoda have been collected, and it seems, desirable to gather them together here. This group of the Crustacea possesses considerable interest from the point of view of geographical distribution, and for this reason a paper on the subject was commenced and partly written out about fifteen years ago, but was then left unfinished owing to want of knowledge of the fresh-water Amphipoda of Australia and elsewhere. Since then many of the gaps have been filled up, and, though our knowledge is still far from complete, some comparison of the fresh-water Amphipoda of New Zealand with those of other countries is now possible.
In this paper, however, I shall give only a list of the various species, with references and notes as to their distribution, reserving more general remarks for a future paper. The three subterranean species have been included because it is around them that the chief interest centres, and because two of them are now known to have near representatives in the surface streams. The terrestrial amphipod Parorchestia sylvicola (Dana) has not been included, because it is truly terrestrial, living far from streams, although it is found only under decaying leaves and in other moist situations, and its method of respiration is doubtless practically the same as that of the freshwater species. It is a species very widely distributed in New Zealand and perhaps elsewhere, and there are various uncertainties and difficulties connected with it that require for their solution more time than can be devoted to the question at present. I have, however, included Parorchestia subtenuis (Dana), as it seems to be usually found in fresh-water streams, though able to live in brackish water, and perhaps also on land. There are other brackish-water species, such as Melita inaequistylis (= M. tenuicornis) (Dana), that I have not included, because, although they may be found in water that at the time is almost or quite fresh, they do not appear to have established themselves in the fresh-water streams.
I have arranged the species according to the classification in Stebbing's “Das Tierreich Amphipoda,” and have given only such references as appeared necessary; others will be found in that elaborate and exhaustive work.
Paraleptamphopus subterraneus (Chilton).
Calliope subterranea, Chilton. in N.Z. Journ. Sci., vol. i, p. 44, and Trans. N.Z. Inst., vol. xiv, p. 177, pl. ix, figs. 1–10 (1882). Calliopius subterraneus, Chilton in Trans. Linn. Soc. London, ser. 2, vol. vi, p. 234, pl. xxiii, figs. 10–18 (1894). Paraleptamphopus subterraneus, Hutton in Index Faunae N.Z., p. 259 (1904). Paraleptamphopus subterraneus, Chilton in P.Z.S. London, 1906, p. 704 (1906). Paraleptamphopus subterraneus, Stebbing'in “Das Tierreich Amphipoda,” p. 294 (1906).
This species was first described in 1882 from the underground waters at Eyreton, in North Canterbury, and was afterwards obtained from similar situations in Lincoln and Ashburton, and at Winchester, in South Canterbury. I have also two specimens from an artesian at St. Albans, Christchurch, depth probably not more than 70 ft.; collected by Mr. J. B. Mayne. In November, 1903, Dr. Cookayne brought me a few specimens, obtained in a surface stream near the River Porter, at Castle Hill, Canterbury; and a month or two later I myself obtained numerous specimens from the same locality. These specimens were quite colourless, showed no trace of eyes, and in these and in all other respects closely resembled the subterranean forms. They were found in a small stream issuing from a spring in the side of one of the river-terraces of the River Porter, and I afterwards also found them in other streams about two miles distant on the other side of the river. Later on the species was taken by Messrs. Lucas and Hodgkin in their investigation of the fresh-water lakes of New Zealand. Among their collections which were submitted to me for examination there was one specimen obtained from Lake Wakatipu (no depth mentioned) in Otago, and one from Lake Taupo, at a depth of 700 ft., in the North Island. These specimens seem to be practically identical with the subterranean forms first described. About
the same time Mr. Laing also found the species in surface streams at Otautau, in Southland, in company with the next species, P. coeruleus. The two species were found together in two different streams in that locality, and though very different in appearance, one being colourless—almost white—and the other dark blue, they appeared to be living together under precisely the same conditions. Mr. Laing thinks that probably the P. subterraneus may have got into the surface streams from springs feeding the streams, much in the same way as appears to have occurred at Castle Hill.
Mr. O. A. Sayce* has called attention to the occurrence of three blind fresh-water Crustacea in the surface waters of Victoria, and has given many interesting facts with regard to them and their surface allies. Other examples of the same thing have been recorded from North America also. In the present case we have P. subterraneus living side by side at Otautau with P. coeruleus, to which it is so closely allied that we may consider it as a subterranean modification of that species.
Paraleptamphopus caeruleus (G. M. Thomson).
Pherusa coerulea, G. M. Thomson in N.Z. Journ. Sci., vol. ii, p. 576 (1885). Paraleptamphopus coeruleus, Hutton in Index Faunae N.Z., p. 259 (1904). Paraleptamphopus coeruleus, Stebbing in “Das Tierreich Amphipoda,” p. 295 (1906).
This species was originally described by Mr. Thomson from specimens taken in a small stream at the top of the Old Man Range, in Otago, at a height of about 3,000 ft., and for many years afterwards no further specimens were discovered. In 1904 Mr. Crosby Smith sent me one or two specimens of Amphipoda from the bog-water at the top of Swampy Hill, near Dunedin. These were not in a fit state for an exact determination, but appeared to belong to this species. In the next year Mr. R. M. Laing brought me undoubted specimens from a stream at Otautau, in Otago, where it had, been found in surface streams along with P. subterraneus. Subsequently I found a single specimen among Crustacea sent to me from Ruapuke Island by Mr. T. Horan, and in 1907 I collected numerous specimens in pools and streams near Drummond, in Southland, and afterwards in streams near Invercargill. All of these specimens show the dark-blue colour described by Mr. Thomson, and this colour does not fade even after the specimen has been kept for a long time in spirit.
As already stated, this species may be looked upon as the surface form from which P. subterraneus has arisen.
Paracalliope fluviatilis (G. M. Thomson).
Calliope fluviatilis, G. M. Thomson in Trans. N.Z., Inst., vol. xi, p. 240, pl. x c, figs. 4 a-c (1879). Paracalliope fluviatilis, Hutton in Index Faunae N.Z., p. 259 (1904). Paracalliope fluviatilis, Chilton in P.Z.S. London, 1906, p. 704 (1906). Paracalliope fluviatilis, Stebbing in “Das Tierreich Amphipoda,” p. 297.
This species is extremely abundant in all the fresh-water streams of New Zealand, and also in many of the ponds formed by them. I have seldom failed to find it in such positions in the South Island, and, though I have fewer specimens from the North Island, it doubtless occurs there
[Footnote] * “On Three Blind Victorian Fresh-water Crustacea found in Surface Water,” Ann: Nat. Hist., ser. 7, vol. viii, pp. 558–64.
almost as abundantly—I have it from Rona Bay, Wellington Harbour, and also from Island Bay; and Messrs. Lucas and Hodgkin obtained specimens from Lake Waikare. Besides being found in fresh water, however, this species is also able to live in salt water. I have on different occasions taken it in great abundance in Otago Harbour in the ordinary sea-water, associated with the usual marine forms. I have also taken it at Island Bay, Wellington, in a pool near high-water mark, which would doubtless be filled with sea-water at particularly high tides, though the water was only slightly brackish at the time I collected the specimens.
Mr. Stebbing considers Pherusa australis, Haswell, to be a synonym of this species, and thinks that CEdicerus novi-zealandice, Dana, may perhaps also belong to it. I have, however, specimens that I think undoubtedly are to be referred to the latter species, and they belong to the CEdicerotidce, and are apparently the same as Carolobatea schneideri (Stebbing). I am dealing with them in my report on the Crustacea collected by the recent expedition to the subantarctic islands of New Zealand.
Paracrangonyx compactus (Chilton).
Crangonyx compactus, Chilton in N.Z. Journ. Sci., vol. i, p. 44, and Trans. N.Z. Inst., vol. xiv, p. 177, pl. x, figs. 13-19 (1882). Crangonyx compactus, Chilton in Trans. Linn. Soc. London, ser. 2, vol. vi, p. 220, pl. xx (1894). Paracrangonyx compactus, Stebbing in “Das Tierreich Amphipoda,” p. 369 (1906).
This is a subterranean species found in the underground waters of Canterbury' Plains, and has been fully described in my paper in the Trans. Linn. Soc. London referred to above. In that paper I stated that the subterranean crustaceans, though common in the shallow wells on the Plains, had not hitherto been found in the artesian wells of Christchurch. Since then, however, Mr. J. B. Mayne has brought me one or two specimens of this species from an artesian at St. Albans, Christchurch. This artesian is sunk only to the first water-bearing stratum, and probably is not more than 70 ft. deep.
It was from the same artesian that the specimens of Paraleptamphopus subterraneus already referred to were obtained, so that the two species are associated in the underground waters at St. Albans, as they are in other parts of the Canterbury Plains.
Phreatogammarus fragilis (Chilton).
Gammarus fragilis, Chilton in N.Z. Journ. Sci., vol. i, p. 44 (1882), and Trans. N.Z. Inst., vol. xiv, p. 179, pl. ix, figs. 11-18. Gammarus fragilis, Chilton in Trans. Linn. Soc. London, ser. 2, vol. vi, p. 227, pl. xxi, figs. 1-25 (1894). Phreatogammarus fragilis, Stebbing in “Das Tierreich Amphipoda,” p. 454 (1906).
This species is found in the underground waters of Canterbury Plains, and has been already fully described in my paper in the Trans. Linn. Soc. London quoted above. Its special characteristic is the possession of very long antennae, peraeopods, &c., and in this respect it resembles several other subterranean species from other parts of the world.
It is closely related to the next species, p. propinquus, but differs in the gnathopods, having the 2 pairs similar in size and shape and with the propod oval and the palm very oblique, while the carpus in each is very short and triangular.
Phreatogammarus propinquus, Chilton.
Phreatogammarus propinquus, Chilton in Ann. Nat. Hist., ser. 7, vol. xix, pp. 388–90, pl. xi (1907).
This species was described in 1907 from a single imperfect specimen collected by Mr. Crosby Smith in a small pool near the top of Mount Anglem, in Stewart Island, at a height of about 2,800 ft. above sea-level. In February, 1908, I obtained a few specimens from a small stream at Rona Bay, in Wellington Harbour. The place at which they were obtained is only a short distance above high-water mark, but the water was quite fresh, and the species was found in association with Parorchestia tenuis (Dana) and other fresh-water animals. I also have had for many years a mounted specimen sent me from Greymouth by Mr. R. Helms, which I had not previously been able to recognise with certainty, but which I can now tell from comparison with Rona Bay specimens is undoubtedly a female specimen of this species.
The species is of special interest owing to its relationship to the subterranean species Phreatogammarus fragilis (Chilton) from the underground waters of the Canterbury Plains. In describing P. propinquus I pointed out that the generic characters given by Mr. Stebbing required slight modification in order to admit the species. In the specimen then described it was impossible to say whether eyes were present or not, owing to its imperfect condition; in the Rona Bay and Greymouth specimens, however, the eyes are present and well marked, so that the character “without eyes” included in Mr. Stebbing's generic diagnosis will also have to be struck out, and the genus Phreatogammarus is thus shown to be still nearer to Gammarus.
The Rona Bay specimens appear to be closely similar to the Mount Anglem specimens originally described, except as regards the 2nd gnathopods. In a female specimen, bearing eggs, from Rona Bay, the 2nd gnathopod is somewhat more similar in general appearance to the 1st, having the carpus moderately long (about two-thirds as long as the propod) and subtriangular in shape. The posterior margin of the carpus bears 3 or 4 short transverse rows of long setae, and there are 2 tufts of setae on the anterior margin, one tuft being at the distal end of the joint; and there is a row of about 7 or 8 setae on the side of the carpus along its distal border. The propod is suboblong in shape; its anterior margin bears 5 short transverse rows of long setae, the last one, at the joint of the finger, being the longest, and containing the most setae; the palm is slightly oblique, and is bordered by a double row of stout setae, which diminish in size towards the base of the finger, those at the place where the point of the finger impinges being the largest, and fairly well defining the palm; the posterior border bears a number of long setae, and other tufts of setae are situated on the sides of the joint, some of the longest being arranged close to and parallel to the palm; the finger has the inner margin minutely serrate, the serrations being closely approximated. The whole gnathopod is somewhat larger than the 1st gnathopod, in which the carpus is considerably longer, being longer than the propod, and bears a more well-marked row of setae along its distal border; the propod is somewhat narrow at the base, and has the palm more transverse, but in other
respects the 1st gnathopod is closely similar to the 2nd gnathopod. Some or all of the setae in the transverse rows on the posterior margin of the carpus in both gnathopods are finely serrate.
The differences in the 2nd gnathopod between the Rona Bay specimens and the Mount Anglem one are perhaps sexual. The Rona Bay specimen described is a female, bearing eggs in the brood-pouches, while the Mount Anglem specimen, with the larger and more oval propod in the 2nd gnathopod, is probably a male; but, as the few Rona Bay specimens that I have, appear to be all females, this point cannot at present be definitely settled.
Chiltonia mihiwaka (Chilton).
Hyalella mihiwaka, Chilton in Ann. Nat. Hist., ser. 7, vol. i, p. 423, pl. xviii (1899). Chiltonia mihiwaka, Stebbing in “Das Tierreich Amphipoda,” p. 555 (1906).
This species was described from specimens found in mountain-streams near Dunedin. During the recent subantarctic expedition specimens were collected both at the Auckland Islands and at Campbell Island. Mr. O. A. Sayce has described 2 species from the fresh waters of Victoria—one, C. australis, has the 3rd uropod less reduced, and consequently approaches more nearly to the genus Hyalella; the other species, C. subtenuis, is more typical of the genus as regards the 3rd uropod, and is apparently closely related to C. mihiwaka, but differs in having shorter antennae and a more slender body.
The genus Hyalella, to which Chiltonia is closely related, is well represented in the fresh waters of America, particularly in South America. Many species have been described from Lake Titicaca by Faxon,* and more recently by Monsieur Edouard Chevreux.† The various species, although all closely related, show a great variety in the form of the body, the projection of the different segments into spinal processes, and so on.
Parorchestia tenuis (Dana).
Orchestia tenuis, Dana in P. Amer. Ac., vol. ii, p. 202 (1852). Orchestia tenuis, Dana in U.S. Expl. Exp., vol. xiii, ii, p. 872, pl. lix, fig. 1 (1853 and 1855). Parorchestia tenuis, Stebbing in “Das Tierreich Amphipoda,” p. 557 (1906).
This species has been frequently mentioned by previous authors, but, as with many species of the Orchestidce, it is very difficult to identify with certainty, and considerable confusion has arisen with regard to it. It has been recently redescribed by Mr. Stebbing, and I refer to the species (as defined by him.) specimens obtained in a fresh-water stream at Rona Bay, Wellington Harbour, and others obtained in similar situations at Akaroa and elsewhere. I also found it on the seashore at Campbell Island, at the mouth of a small stream, and it seems probable that it is a species which can live either in brackish or in fresh water, and perhaps, like many other Orchestidce, it may be also more or less terrestrial in habit.
[Footnote] * Bull. Mus. Comp. Zool. Harvard College, vol. iii, No. 16 (Cambridge, Mass., 1876).
[Footnote] † “Les Amphipodes des Lacs des Hants Plateaux de l' Amerique du Sud” (extract from Mission scientifique, G. de Créqui Montfort et E. Sénechal de la Grange).
Paracorophium excavatum (G. M. Thomson).
Corophium excavatum, G. M. Thomson in Trans. N.Z. Inst., vol. xvi, p. 236, pl. xii, figs. 1-8 (1884). Paracorophium excavatum, Hutton in Index Faunae N.Z., p. 261 (1904). Paracorophium excavatum, Chilton in P.Z.S. London, 1906, p. 704 (1906). Paracorophium excavatum, Stebbing in “Das Tierreich Amphipoda,” p. 664 (1906).
This species was originally described by Mr. Thomson from the Brighton Creek (salt water), near Dunedin. Subsequently I took it from the same creek at a time when the water was almost fresh, and specimens lived in some of the some water for several months. I have also specimens taken from brackish water at Napier. Messrs. Lucas and Hodgkin afterwards took it near Lake Rotoiti (5 fathoms), and in Lake Waikare, where, of course, the water is perfectly fresh. It therefore appears to be one of several species of our New Zealand Amphipoda that are able to live either in salt or in fresh water.
So far as I am aware, it is the only known fresh-water species of the family Corophiidæ.