Camp. Biochem. Physiol. 1976, Vol. 53B, pp. 1 to 2. Peroamon Press. Printed in Great Britain

FREE AMINO ACIDS IN AURELIA AURITA SCYPHISTOMAE FROM CORPUS

CHRISTI, TEXAS

J. MALCOLM SHICK*

Department of Biology, Texas A & M University, College Station, TX, U.S.A.

(Received 14 November 1974)

Abstract--1. The occurrence of fl-alanine in the free amino acid pools of Aurelia aurita scyphistomae from Corpus Christi, Texas, supports previous evidence that this population is related to that of the York River, Virginia, and that both are divergent from the Woods Hole, Massachusetts, population of the species.

INTRODUCTION

EVIDENCE for divergence among geographically separ- ated populations of the scyphozoan Aurelia aurita, has recently been marshalled by Morales-Alamo & Haven (1974). The principal biochemical evidenc~ for such divergence is provided by Webb et aL (1972), who detail the free amino acid (FAA) composition of Aurelia polyps from Woods Hole, Massachusetts, and from the York River, Virginia. The present work examines the FAA pools of members of a third popu- lation, that of Corpus Christi, Texas. Data on starva- tion-induced changes in the pool composition and concentration are also presented.

MATERIALS AND METHODS The experimental animals were from a culture of Aurelia

aurita polyps originated at Corpus Christi, Texas, by Span- genberg (1964). They were maintained in iodine-free artifi- cial seawater (30%o) at room temp (21-24°C), and were fed Artemia salina nauplii twice weekly.

Two groups of polyps were removed from the stock cul- ture and acclimated to 20°C for 2 weeks; one group was fed twice weekly, while the other was starved for the entire period. At the end of this time, fed (2 days since last feed- ing) and starved (14 days since last feeding) polyps were decontaminated by removing adhering debris with a pipet, and were rinsed four times in Millipore filtered (0.45 #m pore size) seawater. Subsamples of both groups were removed for weighing as described by Shick (1975).

Groups of 100 fed and starved scyphistomae were then homogenized in 0.5 ml of absolute ethanol in an ice bath. The homogenate was centrifuged at 20,000 0 for 20 min, the pellet dried and weighed, an aliquot of the supernatant removed for determination of total ninhydrin positive sub- stances (NPS) according to the method of Clark (1964), and the remaining supernatant evaporated to dryness in vacua. The residue was redissolved in lYo HC1 and sub- jected to ion exchange chromatography on a Beckman 120A amino acid analyser using a 0.2 N citrate buffer at pH 3.25 and 4-28 on a 55-cm column of PA-28 resin at 55°C. Basic amino acids were not determined.

RESULTS AND DISCUSSION

Absolute amounts of acidic and neutral free amino acids in Texas Aurelia aurita polyps are given in Table 1. As in the data of Webb et al. (1972) for

* Present address: Department of Zoology, University of Maine, Orono, ME 04473, U.S.A.

Virginia polyps at the same salinity, glycine predo- minates and taurine and fl-alanine are present in sub- stantial amounts. Values for total NPS are also given in Table 1, although these data may include ammonia.

While the concentrations of most free amino acids decline during 2 weeks of food deprivation, there is little change in the internal FAA or total NPS con- centration (Table 1). This is achieved largely by in- creases in glycine, taurine and fl-alanine, perhaps a compensatory mechanism to maintain internal levels of osmotically active organic substances during the utilization of other amino acids in the pool. The role of the FAA pool in cellular volume regulation in

TABLE 1

Absolute amounts (n moles/mg dry weight) of free amino

acids (FAA) in fed (2 day) and starved (14 day} Corpus

Christi, Texas Aurelia aurita polyps at 300/00 and 20°C.

Tr = trace amounts, Values also given for total ninhydrin

positive substances (NPS).

Amino acid Fed Starvsd

Taurine 29 49

Aspartic acid 4 6

Threonine i0 8

Serine 23 36

Glutamic acid 5 6

Proline 22 Tr

Glycine 89 154

Alanine 17 14

Valine 25 12

Methionine Tr Tr

Isoleucine 15 6

Leucine 21 4

Tyrosine 13 Tr

Phenylalanine I0 Tr

~ -alanine 23 48

Total FAA* 306 343

Total NPS 353 364

*Excluding undetermined basic amino acids

2 J. MALCOLM SHICK

another euryhaline cnidarian, the sea anemone Diadu- mene leucolena, has been demonstrated by Pierce & Minasian (1974). The significance of exogenous gly- cine to the nutri t ion of starved polyps is discussed elsewhere (Shick, 1975).

Webb et al. (1972) and Morales-Alamo & Haven (1974) have correlated the presence of fl-alanine in the pools of Virginia scyphistomae and its absence from those of Massachusetts polyps with observed differences in morphology (round mouth vs cruciform mouth) and in the cnidome (presence vs absence of atrichous polyspira nematocysts) between the two populations. An additional difference concerns the method of asexual reproduction: Virginia polyps reproduce by budding directly from the body of the parent polyp, while Massachusetts scyphistomae reproduce primarily by stolonization (Calder, per- sonal communication). Further, Virginia polyps do not form podocysts, while Massachusetts polyps do (Morales-Alamo & Haven, 1974).

Interestingly, Texas Aurelia scyphistomae have atri- chous polyspiras (Spangenberg, 1964) and round mouths (Morales-Alamo & Haven, 1974), reproduce by direct budding, do not form podocysts, and con- tain large amounts of /J-alanine. They would thus appear to be more closely related to the Virginia population than to that of Massachusetts, and the northern Gulf of Mexico fauna has in fact been char- acterized as Carolinian in affinity (Ekman, 1953; Phil- lips, 1971).

Acknowledgement~J. M. Prescott, Texas A&M Univer- sity, provided time on the amino acid analyzer. I am espe- cially grateful to D. R. Calder, Marine Resources Research

Institute, Charleston, South Carolina, for his continuall 3 helpful comments and his review of this manuscript.

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