Rearing Fairy Shrimp in the Laboratory

Rearing Fairy Shrimp in the LaboratoryAuthor(s): V. W. KaczynskiSource: Limnology and Oceanography, Vol. 16, No. 3 (May, 1971), pp. 586-588Published by: American Society of Limnology and OceanographyStable URL: http://www.jstor.org/stable/2834142 .

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586 NOTES

brane sensor head. With the flow-through chamber empty, the instrument then re- sponds to the salinity at the remote head. The unique characteristics of the membrane sensor ensure that the device re- sponds only to the film of liquid close to the membrane surfaces; the nature of the sediment surrounding the head is im- material, provided that electrical continu- ity is maintained between the membrane surfaces.

T. ROGER S. WILSON

Woods Hole Oceanographic Institution, Woods Hole, Massachusetts 02543.

REFERENCES

GIEsKEs, J. M. 1967. Der Membran-Salzfiihler als geeignetes Gerat zur Registrierung der Schichtung in Meere. Kiel. Meeresforsch. 23: 75-79.

1968. Some investigations into the sensitivity of the membrane salinometer for various ions. Kiel. Meeresforsch. 24: 18-26.

- AND K. GRASSHOFF. 1969. A study of the variability in the hydrochemical factors in the Baltic Sea on the basis of two anchor stations, Sept. 1967 and May 1968. Kiel. Meeresforsch. 25: 105-132.

KosyCE, P. H. 1964. tber ein potentiometrisches Verfahren zur Bestimmung von Chloridkon- zentrationen im Meerwasser. Kiel. Meeres- forsch. 20: 138-142.

MANGELSDORF, P. C., JR. 1967. Salinity mea- surements in estuaries, p. 71--79. In G. H. Lauff [ed.], Estuaries. Publ. Amer. Ass. Ad- van. Sci. 83.

SANDERS, H. L., P. C. MANGELSDORF, AND G. R. HAMPSON. 1965. Salinity and faunal dis- tribution in the Pocasset River, Massachu- setts. Limnol. Oceanogr. 10(Suppl.): R216- 229.

WILSON, T. R. S. 1970. The development of a membrane salinometer for monitoring estuaries. Woods Hole Tech. Rep. 70-45.

REARING FAIRY SHRIMP IN THE LABORATORY1

ABSTRACT

A complex food (dilute duff infusion, yeast, and two species of algae) was found to be highly satisfactory in rearing the anos- tracan Eubranchipus bundyi. Yeast alone could be used to culture this species but monoxenic algal cultures were inadequate diets. The complex diet was easily quantified for routine rearing and experiments and was measured in terms of particulate carbon.

In the analysis of several natural popu- lations of Eubranchipus bundyi, individual growth rates, fecundity, and longevity var- ied in time and from pond to pond. Valid laboratory experiments were needed to establish a data base for comparing and interpreting these parameters in nature. Moore (1957) described two diets satisfactory for culturing the genus Strepto- cephalus. When E. bundyi was- cultured on these diets (at various temperatures, 4-20C) its growth rate, maximum size, fecundity, and survivorship were all less than that observed in nature. A culture technique was then developed that al-

1 Abstracted in part from a Ph.D. thesis pre- sented to the Graduate School of Cornell Univer- sity, Ithaca, N.Y. 14850.

lowed E. bundyi to grow, survive, and reproduce at rates equal to those observed in nature.

MATERIALS AND METHODS

All rearings were done in 2-liter plastic refrigerator dishes at a maximum density of 5 fairy shrimp and fixed temperatures of 4, 8, 12, 15, and 20C. The water used was a dilute duff infusion ( duff is the upper layer of forest litter and soil). One volumetric part duff (taken from the dried or frozen bottom of a temporary pond) was added to 25 parts charcoal-filtered water. After 4 days at 15C under normal laboratory lighting, the supernatant of the infusion was drawn off, filtered through a 0.16-mm mesh plankton net (No. 10), and diluted with an equal part of charcoal-filtered water. The dilution of this seminatu- ral water was designed by trial and error barely to support growth of E. bundyi and acted as a minimum food level. All food levels above this minimum were supplemented with drops of yeast suspension and an equal mixture of Chlorella vulgaris and Ankistrodesmus falcatus taken from cultures in the log phase of growth. A pack-



NOTES 587

TABLE 1. Eubranchipus bundyi growth and egg production at 15C in response to quantities of the complex diet described in the text, together with the amounts of particulate organic carbon

determined for these food levels

Mean max Mean growth eggs/ Ag C/liter (mm) female (mean ? 1 SE)

Dilute duff infusion 8.0 0 227.5 ? 79.0 Supplemented 1 X 9.8 5.6 592.6 ? 22.3

2X 11.4 36.0 783.9 21.1 4X 13.1 108.3 1,628.6 ? 96.0 6X 14.0 199.3 2,123.3 ? 58.7 8X 11.7 55.2 2,629.9 86.2

age (7 g) of commercial active dry yeast was added to 225 ml of distilled water for the standard yeast suspension (100 drops equal 5 ml). This was made up every 4 days and refrigerated. The algal mixture was standardized to 100 + 5 Klett units at 4,200 A.

The first supplemented food level (lx) was the diluted infusion water plus one drop of yeast suspension and 25 ml of the algal mixture, for 5 individuals, for 2 days. Volume was adjusted to 2 liters. Correspondingly larger amounts of supplemented food could be easily added (2x, 4x, and 8x max). The technique of Men- zel and Vaccaro (1964) allowed accurate quantification of these food levels in terms of particulate organic carbon.

The fairy shrimp were moved to clean vessels and fresh medium every 2 days by using a large, flexible mouth aspirator (ca. 1-cm I.D.). As long as the shrimp were aspirated (with water) head first no in- juries occurred. Aeration of the vessels was not necessary but did prevent settling of food, especially the yeast cells.

Individuals for the laboratory rearings were obtained directly from the duff infu- sions. In central New York State, large co- horts of nauplii could be hatched anytime from the second week of December until the spring thaw and natural hatching. Broch (1965) described a technique to break diapause of the egg stage of E. bundyi before December.

Unialgal cultures of Chlamydomonas reinhardti, A. falcatus, C. vulgaris, and

Scenedesmus sp. were used by themselves as test foods, as was the standard yeast suspension.

RESULTS AND DISCUSSION

The temperature of the rearing was im- portant. Generally speaking, E. bundyi survived and grew best at the cooler temperatures. For brevity I report only the following comparisons from the 15C rearings. No unialgal food was able to support E. bundyi longer than 10 days after hatching. The yeast suspension in various quantities allowed E. bundyi to live, grow, and even repro,duce; however, the individuals were generally small (mean max length from tip of head to base of cercopods was 10.2 mm, n 24) and fecundity was low (mean total eggs per female was 7.8). Table 1 gives the com- parative responses when the diluted or supplemented duff infusion was used, with the amounts of particulate organic carbon for these food levels. The amount of particulate organic carbon in three central New York vernal ponds ranged from 400- 1,700 /xg C/liter. Most values were between 500-1,000 ptg C/liter and generally highest early in spring and tapered off toward summer.

The poor growth and reproduction at the 8x food level can probably be attrib- uted to an adverse effect from the large amount of yeast it contained; similar phe- nomena occurred in test rearings with only large amounts of yeast. The growth and fecundity values in Table 1 are less than some observed in nature. Maximum length (excluding cercopods) observed in nature was 18-19 mm. The maximum rate of egg production was at 8C in laboratory experiments at the 4x food level. Mean maximum growth at 4C was 19.2 mm (n = 4), and at 8C was 18.5 mm (n= 12). These results will be more fully discussed elsewhere.

V. W. KACZYNSKI

Department of Oceanography, University of Washington, Seattle 98195.



588 NOTES

REFERENCES

BROCH, E. S. 1965. Mechanism of adaptation of the fairy shrimp Chirocephalus bundyi Forbes to the temporary pond. Cornell Univ. Agr. Exp. Sta. Mem. 392. 48 p.

MENZEL, D. W., AND R. F. VACCARO. 1964.

The measurement of dissolved organic and particulate carbon in seawater. Limnol. Oceanogr. 9: 138-142.

MOORE, W. G. 1957. Studies on the laboratory culture of Anostraca. Trans. Amer. Microsc. Soc. 76: 159-173.

NEARSHORE TRACKING OF SEABED DRIFTERS'

ABSThACT

Miniaturized sonic transmitters attached to seabed drifters have been used successfully to trace bottom current flow in an estuary and on the continental shelf.

Bottom currents in the shallow water of the estuarine zone or continental shelf are frequently difficult to measure because of vigorous wave action and because commercial or recreational boat operators may interfere with moored equipment. How- ever, information concerning residual drift along the bottom in such areas has been gained by plotting tracks of seabed drifters released at known locations and later recovered by beachcombers or in fisher- men's nets (Woodhead and Lee 1960; Bumpus 1965). A means of obtaining more specific information with seabed drifters was suggested to me and my col- leagues by the success biologists have had tracking fish to which miniaturized sonic transmitters were attached (Leggett, unpublished; Carey, unpublished). A seabed drifter with a similar transmitter mounted on it appeared to be a potentially effective device to acquire information on bottom water circulation over periods ranging from a few days to a few weeks.

DESCRIPTION AND RESULTS

To evaluate such a device we used a receiver, hydrophone, and sonic transmitters manufactured by Smith-Root Elec- tronics (Seattle, Wash.); some of the specifications cited below were provided by the manufacturer. Figure 1 shows one

1 This research was supported by the U.S. Geo- logical Survey, Woods Hole Oceanographic Insti- tution Contract 12109. Contribution No. 2625 of the Woods Hole Oceanographic Institution.

of the transmitters attached to a seabed drifter. The transmitter is 8.9 cm long, has a maximum diameter of 1.9 cm, and weighs 29.5 g in water. The output fre- quency is 74 kHz and output power is 52 dB (reference level 1 pbar at 0.96 m) in freshwater at 29C. The pulse repetition rate is preset by the manufacturer at the value between 0.5 and 8/sec desired by the user. After a transmitter is activated it operates continuously until the battery is exhausted or the circuitry disconnected. The effective battery life estimated by the manufacturer is 60 days. Several of the transmitters that we placed on moorings where the bottom water temperature was between 6 and 7C, however, were not operating after 30 days. At the ship the signal is detected with a portable hydrophone (80 conical beam pattern) and amplified as an audio tone with a small tuneable (60-180 kHz) sonic receiver that can be operated continuously for about 10 hr before its internal battery must be recharged.

In quiet water we have detected transmitter signals from drifters on the bottom at water depths of 20-80 m from a maximum distance of about 2 km. When waves were large, however, noise due to water turbulence, especially around the ship's hull, occasionally masked the signal and reduced the detection range to a few hun- dred meters. We estimated that we were able to position the ship within about 20 m of a drifter's location in good weather where water was less than 40 m deep, but our accuracy was less in bad weather or deeper water. Observations commonly were made with the ship moving very slowly or stopped to minimize turbulence around the hydrophone and the ship's hull.



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Rearing Fairy Shrimp in the Laboratory