Small Aquarium Research Articles

The behaviour of some amphiur1d Brittle-Stars

Eight species of burrowing amphiurid brittle-stars have been observed in small aquaria. Burrowing is effected by the tube-feet and the arms; the animals come to lie in a semi-permanent burrow whose walls are reinforced with mucus, in such a way that the disk is several centimetres down but the tips of the arms can explore the surrounding surface. The burrow is ventilated by the undulation of one or more arms. The effectiveness of this activity is increased by the tube-feet in one of three ways: they may be held out sideways between the spines, lightly anchored to the burrow wall; they may adopt a similar posture but pick up particles of the substratum until they are embedded in a continuous ‘fringe’; or the tube-feet may transfer particles of the substratum to the arm-spines and there build a fringe from which they remain free. It is suggested that the different methods of building the respiratory fringes may have taxonomic significance and may be associated with differences in the shape of the arm spines. The animals can obtain food from three sources, namely, the substratum, its surface, and the water above it. In each case the tube-feet are employed to transfer material to the disk. Spawning behaviour was observed once and is described.

Empirical Determination of Air-Water Impedance Differences in Small Tanks

Airborne sonic pressures in an open or sealed housing enclosing an aquarium were measured in the air and in the water under near- and farfield conditions. Effective impedance differences were 9.1 dB with the housing open and 4.5 dB with the housing sealed in the nearfield, and 6.5 dB in the open condition and 7.1 dB in the closed condition in the farfield. Both conditions indicated an effective impedance difference considerably less than the 35.5 dB impedance difference between air and the open ocean. Prevalent use of sonic fields in small aquariums thus requires detailed calibration of sonic fields in tanks where the air-water interface is traversed. Because of the 30 dB loss from disruption of the ossicular chain, the ear, in spite of anatomical likeness, is not similar to a closed speaker (eardrum) system over a water-filled tank (cochlea).

Empirical Determination of Air-Water Impedance Differences in Small Tanks

Airborne sonic pressure in an open or sealed housing enclosing an aquarium was measured in the air and in the water. Effective impedance differences were 9.1 dB with the housing open and 4.5 dB with the housing sealed. Both conditions indicated an effective impedance difference considerably less than the 35.5 dB impedance difference between air and the open ocean. Prevalent use of sonic fields in small aquariums thus require detailed calibration of sonic fields in tanks where the air-water interface is tranversed. The middle ear apparently functions primarily to transduce airborne sonic pressure into displacement in the cochlear fluids, rather than to match sonic pressure impedance.

Eggs and early larvae of Thrissocles species (Engraulidae: Pisces)

Eggs of Thrissocles species are found in surface plankton in the Ernakulam Channel (Cochin Harbour)during February to May 1967. The eggs hatch within 24 h. Empty egg shells have characteristic apertures, through which the embryos have emerged; yolk is resorbed 36 h after hatching.Larvae (36 to 72 h groups) assemble at the lighted region of the aquaria during day-time and scatter to different levels at night. Larvae older than 72 h show no inclination to assemble as before. All larvae died between 96 and 110 h after hatching. Many batches of eggs were reared in the same medium, and all of them behaved as described. The results indicate that the right type of food was available in the aquaria for larvae up to a period of 72 h. The volume of water also appears to have a bearing upon the survival rate and longevity of the larvae since, in small aquaria, more larvae died at an early stage.

Sound Fields within Aquaria

Small aquaria are generally convenient for bioacoustic experiments. Sound introduced into such tanks is often measured with pressure-sensitive hydrophones. Unfortunately, sound in a small tank never propagates in a plane wave, and therefore pressure measurements can be highly misleading. The sound field also fails to resemble the natural acoustic environemnt of the organisms. We have obtained further measurements of the effective wall impedance and, hence, estimates of the wave impedance within such tanks, using the technique described at the Second Symposium on Marine Bio-Acoustics (1966). The fields within the tanks are similar whether the sound source is located in the water or in the air nearby. Particle velocities in the water (and hence displacements) are orders of magnitude greater than has been sometimes assumed from uncritical use of pressure hydrophones. This suggests that animal behavior may be due to lateral-line response rather than to auditory system response. [Hudson Lab. of Columbia Univ. Informal Documentation No. 148. This work was supported by the U. S. Office of Naval Research.]

Longevity in a Polychaete and a Coelenterate

IN December 1949 I collected a small group of the serpulid Mercierella enigmatica Fauvel, which lives in brackish-water as well as in the sea, growing on reeds in Lake Mariout, Alexandria, Egypt. I brought the dozen or so of the tube-worms back to London and kept them alive for a number of years in a small aquarium containing sea-water diluted half-and-half with distilled water. Together with the tube-worms were a filamentous green alga, Rhizoclonium sp., a brown alga, Ectocarpus sp., and a small rissoid gasteropod mollusc which went through many generations. Nothing was added to the aquarium except distilled water occasionally. The Mercierella must have fed on flagellate protozoa and perhaps sometimes on algal zoospores. The last individual worm died in May 1962, that is, 12 years and 5 months after capture. During captivity the most noticeable change was that the colour of the crowns altered from the original light greenish-brown to a dark brown. The age of the animals at the time of the capture was, of course, unknown, but their length of life in captivity seems to be the greatest known for an annelid.

Temperature-Control for a Group of Small Aquariums

Temperature-Control for a Group of Small Aquariums

Experimental Studies of the Reproductive Behaviour of Xenopus Laevis

Males of Xenopus laevis, maintained in constant experimental conditions, when placed with females injected with gonadotrophin and ovulating (hot females) in small aquaria, clasp them (assault) and remain clasping for hours, until after fertilization. Placed with females not so treated (cold females) or with males, they also assault, but only remain clasping for a few minutes, then unclasping and after an interval repeating the process. Thus a sequence of Clasping Spells is obtained. This paper deals with the position of the clasp on the body of the passive partner (the animal clasped). The assault on any passive partner may be on a great variety of different parts of the body, the part concerned being called the assault position. During a spell, rapid unclasping may occur, followed by immediate reclasping on another part of the body, called the adjusted position. Several such adjustments may occur in one spell. The commonest sequence of positions on a hot female is: Thigh (assault) - Waist (adjusted). On other passive partners a great variety of sequences may occur. Assault positions on hot females are on the thigh or waist in 85% of observed assaults. On cold females and males, the percentage is significantly lower, and is correlated with a variable in the central nervous system of the active partner called Clasping Tendency, associated with clasping behaviour. This correlation is taken as evidence of a relation between two functionally distinct types of control mechanism, previously distinguished as Determination and Ajustment. The percentage is not significantly different between assaults on cold females and those on males. To account for the observed facts, a hypothesis of three orientation mechanisms is presented, with a discussion on the role of guiding stimuli. It is shown that the behaviour so generated would be adaptive, and bears an adaptive relation to the system of mating behaviour previously inferred for Xenopus laevis and other Anuran species.

魚類の聴覚特性に関する研究-I

The author considered the auditory characteristic in a lateral line of fish and calculated it on the physiological data about Carassius auratus (Body length; about 20cm.: Absolute refractory periods; 3 milli-sec. in A-neuron and 11 milli-sec. in B-neuron: Transmitting verocities of stimulation; 28.9m/sec. in A-neuron and 6.5m/sec. in B-neuron). The results got are as follow: a) When there is a sound-source in the elongate direction of body-axis, the upper limit of audible frequency may be about 7500 c/sec. and the most sensitive frequency is about 160 c/sec. In this case, the influence of the distance between the sound-source and the fishbody on the range of audible frequency is negligible. b) When there is the sound-source in the vertical direction against body-axis, the influence of the distance between the source and the body on the range of audible frequency is serious. For an example, although the most sensitive frequency is about 710 c/sec, at one meter distance, the most sensitive one is about 1300 c/sec. at a long (1000m.) distance. c) There is not the lower limit of audible frequency. It seem that the audible frequency may be lower as the sound-pressure becomes higher almost independently of the distance between the source and the body. Then, in experiments about the auditory characteristic of fish, we must be careful for the definitions of a sound-source position against fish-body and of the intensity of sound-pressure. Especially, as the sound in a small aquarium causes its reflections, interferences and -transmissions through walls, the devices to suppress them must be adopted so as to gain clear effects or correct results., The author is studying about aquaria with walls isolated from the influences of sound.

The effect of water flow and oxygen concentration on six species of caddis fly (Trichoptera) larvae

Summary. The six species of caddis larvae selected for study were collected from the River Blyth, Northumberland, a small river with alternate shallow swift‐flowing and deeper slow‐flowing stretches. The species selected were Rhyacophila dorsalis, Wormaldia subnigra and Hydropsyche instabilis from swift water, Anabolia nervosa and Polycentropus flavomaculatus from slow‐flowing water and Stenophylax stellatus, a species which is generally distributed. Of these species, Anabolia nervosa and Stenophylax stellatus are case‐bearing larvae and Hydropsyche instabilis, Wormaldia subnigra and Polycentropus flavomaculatus spin nets or snares for food collection. Rhythmic undulatory current‐producing movements of the abdomen are made by all the larvae except Rhyacophila dorsalis and Wormaldia subnigra. Accurate identification entailed rearing the larvae to the adult state. Rhyacophila dorsalis, Wormaldia subnigra and Hydropsyche instabilis, species from swift waters which do not live long in still‐water aquaria, were successfully reared in small aquaria in which the water was continuously stirred by means of rotary stirrers. The larvae may be arranged in the following ascending order of ability to resist the flow of water when exposed to the full force of the current in an experimental channel:— Polycentropus flavomaculatus. Anabolia nervosa. Stenophylax stellatus. Wormaldia subnigra. Rhyacophila dorsalis, Hydropsyche instabilis. The behaviour of the net‐ and snare‐spinning larvae in aquaria showed that Hydropsyche instabilis and Wormaldia subnigra larvae only spin typical nets in flowing water and that the former will spin nets in slower‐flowing water than will the latter. Polycentropus flavomaculatus larvae will spin snares in still water. Oxygen determinations on samples of water from swift‐ and slow‐flowing areas of the River Blyth showed only small differences. Further, under certain circumstances water from swift‐flowing reaches may have a lower dissolved oxygen concentration than water from slow‐flowing reaches. The minimum oxygen concentration, i.e. that at which larvae become immobilized, was determined experimentally for each species in still water. This concentration was relatively high for the swift‐water species Rhyacophila dorsalis, Wormaldia subnigra and Hydropsyche instabilis, but in stirred water it was similar to that obtained for the other species in still water. In Hydropsyche instabilis, Polycentropus flavomaculatus, Stenophylax stellatus and Anabolia nervosa larvae decreasing oxygen concentration tended to increase the number of undulatory abdominal movements. In Hydropsyche instabilis and Polycentropus flavomaculatus larvae the number of movements was reduced by an increase in the rate of stirring of the water. In conclusion, the importance of water flow in determining the distribution of these larvae is stressed. Larvae unable to withstand the force of the current are unable to inhabit swift waters (Polycentropus flavomaculatus, Anabolia nervosa). Some larvae are dependent upon current for feeding (Hydropsyche instabilis, Wormaldia subnigra), and larvae readily immobilized at a relatively high oxygen concentration in still waters (Rhyacophila dorsalis, Wormaldia subnigra, Hydropsyche instabilis) can tolerate low oxygen concentrations in flowing water.

Aphanomyces as a Fish Parasite

During November, 1942, a serious outbreak of a fungal disease on fish developed in some of the aquaria in the Vivarium of the University of Illinois. The macroscopic appearance of the fungus on the infected fish suggested a water mold, possibly a delicate species of Saprolegnia, as the causal organism. Microscopical examination and cultural studies of the parasite revealed it to be a sterile Aphanomyces. Certain species of Saprolegnia, Achlya, and Dictyiuchus are known to parasitize fish and in some instances to cause serious trouble. Aphanomyces species, however, are more widely known as plant parasites or as parasites of such Invertebrates as the European Crayfish and of some smaller fresh water Crustacea. Because of the severity of the epidemic here and its unusual occurrence as a parasite on fish,1 we deem it of some interest to publish this brief account. The first infection was noted in a small one gallon aquarium November 4th, 1942, and was observed in other aquaria within a few days. The fish in two small aquaria, those in a 28 gallon rectangular aquarium and those in a large concrete burial vault used as an aquarium, were almost entirely eliminated by this organism within a period of about two weeks. The source of inoculum is not known but it is probable that it was introduced along with some food materials grown in containers of fresh water kept outside of the Vivarium. Adults as well as young were attacked in a characteristic manner and the virulence of the organism on both age groups was equally

Further Notes on the Overwintering of the Eggs of Anopheles walkeri Theobald with a Description of the Eggs

The overwintering eggs were obtained September 5-23 from four wild specimens collected at Ithaca, New York. The mosquitoes were confined individually, for oviposition, in small jars in the laboratory. The eggs of each batch were removed from the jar within 24 hours and placed out-of-doors on the roof of a low north wing, and thus were protected from direct sunlight while exposed to out-of-door temperature. They were left there until spring. Both small enameled cups and Syracuse watch glasses were used as containers, each one being covered with a glass cover to retard evaporation. They were all placed under a small glass aquarium as protection against wind, snow and rain. The eggs were placed on water in the containers and confined within waxed paper rings which floated on the surface. The temperature data given are air temperatures which have been secured from the records of the U. S. Weather Bureau Station at Ithaca, which is about 100 yards distant.

A Mechanism for the Continuous Circulation and Aeration of Water in Small Aquaria

A Mechanism for the Continuous Circulation and Aeration of Water in Small Aquaria

A Mechanism for the Continuous Circulation and Aeration of Water in Small Aquaria

A Mechanism for the Continuous Circulation and Aeration of Water in Small Aquaria

Living Ostracods in the Rectum of a Frog

QUITE recently I received a communication from Mr. J. Omer-Cooper in the course of which he said: “When examining the contents of a frog's rectum yesterday in the course of our lab. work I noticed several living Ostracods. The frog had been kept for some time in a small aquarium which contains a good many ostracods. I have pickled up some of the contents of the rectum and also some of the ostracods from the aquarium…. The frog was chloroformed, well washed under the tap and dissected in normal salt solution. There is no chance that accidental contamination of the preparation can have taken place.”

Observations on the Early Larval Activities of Nymphula Maculalis Clemens* (Lepidoptera).

In a previous paper dealing with the biology of certain aquatic Lepidoptera, the writer pointed out (1916, pp. 173-174) that while it was possible to force a few first instar larvae of Nymphula maculalis Clemens to feed upon the tissue of the floating, green leaf of the yellow water-lily in small aquaria, the normal field habits of the younger instars were not determined and that in rearing such larvae in aquaria difficulty was experienced in securing the second larval instar and in preventing a very high mortality among those which hatched from egg-masses. It was also pointed out in the same connection that certain circumstantial evidence suggested that possibly the larvae, on hatching, “settle to the bottom and after one or two ecdyses, approach the surface of the water on the petioles of the water-lily.” Field observations and breeding work in aquaria subsequent to that on which the above mentioned paper was based repeatedly confirmed the following points from which the inference concerning some form of bottom life for early instars was derived: (1) Recently hatched larvae tend to drop to the bottom of aquaria and wander restlessly about, manifesting no interest in fresh tissue from floating leaves of the normal food plant (2) The first and second instars are not found, in the field, on the floating leaves of the yellow water-lily, although such leaves are the bearers of the egg-masses; (3) Only well advanced larvae occur on the floating leaves, but somewhat younger larvae are to be found on the submerged, green leaves which have not yet reached the surface; and (4) Pupae are absent on submerged leaves. It therefore became reasonably certain that a study of the bottom of the lily beds was necessary in order to understand the early larval development of this species. Forbes (1910, p. 225) had also reported that in his work on Nymphula gyralis Hulst the larvae, just hatched from the eggs, “all died without eating, though provided with leaves of Nymphaea and Limnanthemum (laid on the latter), but they gathered on the Nymphaea leaf in numbers. Possibly in the first stage they may feed on the submerged stems.” Apparently circumstances attending the early larval history of Nymphula gyralis resemble somewhat those of NymPhula maculalis , and it may be that results described herein will yield some clue as to their nature.

Isolation Cultures with Small Aquaria

Isolation Cultures with Small Aquaria

Multiplication by Fission in Holothurians

THERE is to be found in various text-books the statement that certain pedate holothurians are capable of spontaneous transverse division, each part so formed producing a new individual (Lang, 1894, p. 1095; Morgan, 1901, p. 144). This opinion seems to be based, so far as I can learn, upon the observations of Dalyell (1851, p. 74; PI. XIVT), although Morgan says that more recent observers have confirmed this discovery. Chadwick (1891), also, found small individuals of Cucumtaria plawci to undergo self-division, and in one instance the posterior portion so formed also divided. These are records of division in holothurians which were being kept in small aquaria, and there has been no evidence, so far as I am aware, going to show that self-division of adult pedate holothurians is a method of propagation among these animals in their normal surroundings. Hence the possibility of non-sexual reproduction in this way is usually stated with reserve (cf. Lang, 1894). In other classes of echinoderms (aside from echinoids) the expedient of reproduction by fission is of course not unusual; but in ophiuroids and in such starfishes as Linckia (Clark, 1913) and Coscinasterias (Crozier, 1914),2 we are dealing with the division or fragmentation of a

Aged Tadpoles

THE experience of your correspondent Mr. John Don (February 17, p. 458) is no new one. More than twenty years ago we had in a small aquarium in the Charterhouse Museum a tadpole two years of age. To the best of my recollection this veteran never acquired any legs, either hind or front, but the head and body were extraordinarily large. At the present moment I have in my laboratory seven living tadpoles reared from spawn deposited last spring. Of these, three only have developed hind legs. These appendages appeared rather suddenly in December, a few days after I had supplied, for the first time, some fragments of hard-boiled egg.

A New Method for Growing Hydroids in Small Aquaria by means of a Continuous Current Tube

The simple piece of apparatus, to which I give the name “Currenttube” was made last year in the Marine Laboratory at Plymouth. I designed it especially for growing Hydroids, and for them it has proved to be a success; but it should also be useful for other fixed organisms, such as sponges, polyzoa, and ascidians.The previous methods which I had used for growing Hydroids in bell-jars or small aquaria never gave complete satisfaction. Occasionally a success was recorded, but there were too many failures, which frequently involved a great waste of labour.