studies on the fauna of an algerian hot spring

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STUDIES ON THE FAUNA OF AN ALGERIAN
HOT SPRING
BY I. L. MASON
(Received i May 1939)
(With Four Text-figures)
MANY exaggerated statements have been made, and too often uncritically repeated,
concerning the temperatures at which animals and plants have been found in hot
springs. To throw light on this subject, the author undertook two expeditions—in
the summer of 1937 and the winter of 1938-9—to study the hot springs at Hammam
Meskoutine, Algeria.
These springs and some of the animals in them were originally described by
Gervais (1849) an<i later by Blanchard (1903), but neither author gave them more
than a casual examination. Since they are not sulphurous or saline they constitute
a habitat in which the only special feature is the high temperature; furthermore,
since they present a graded series of temperatures from 95 ° C. downwards, their
fauna is living in a permanent temperature gradient. These two features make them
particularly suitable for the study of the upper temperature limits for life.
An attempt was also made to discover whether the hot spring animals differ
physiologically from normal forms and if so wherein this difference lies. This is a
subject about which there is very scanty information in the literature, except in the
case of marine animals for which physiological races, adapted to different environ-
mental temperatures, have been discovered by Mayer (1914), Huntsman & Sparks
(1924), Fox (1936, 1938), and Fox & Wingfield (1937).
PART-1. MAXIMUM TEMPERATURES AT WHICH ANIMALS AND
PLANTS WERE FOUND
The hot springs of Hammam Meskoutine rise at various temperatures between
50 and 900 C. in the beds of travertine (95 % CaCO ) which they have deposited.
3
The most spectacular series of springs rises on a plateau, and the water flows over
a gleaming white precipice as a steaming cascade. The water contains 1-4 parts per
thousand of salts. A typical analysis of the water and its deposit is given in Table I.
At its source the pH of the water is about 7-0, but it rises to 8-5, as the water in
cooling gives off CO and deposits CaCO . The hot water flows into a small stream,
2 3
the Oued Chedakra, which it heats to 60-65° C. As the heated stream flows away
it gradually cools, producing a series of habitats similar except that their temperatures
L L. MASON
vary from 65 to 200 C. This series is repeated several times in the Oued Chedakra
and also in a number of irrigation canals drawn from it, so that the range of any
animal could be confirmed in a series of gradients. Finally, the stream flows into a
small river, the Oued Bou Hamdam, which in summer is heated to 400 C, but in
winter, when in flood, is unaffected.
Table I. Chemical Analyses (from Fiorini, 1935)
Spring water (in g. per litre) Gas evolved
Calcium (Ca) 0227 Carbon dioxide 97'°%
Magnesium (Mg) 0034 Hydrogen sulphide o-5
Alkali metals (as Na) 0228 Nitrogen
Sulphates (SOJ 0'393 Deposit (from Piot, 1893)
Chlorides (Cn 0329 Calcium 5*-9
Carbonates (COj combined) 0-192 Magnesium
2'I
Total drv residue 1 412 Sulphate
Carbonate
4O-2%
o " Hot spring
t—• - Distribution of
Barbus callensis
Scale: 3J in. to the mile
Fig. i. Map of the Oued Chedakra showing the position of the principal springs and the distri-
bution of Barbus callensis. The small figures show the approximate summer temperatures along the
stream.
The sketch map (Fig. 1) shows the position of the chief springs, the course of
the Oued Chedakra and the summer temperatures at various points along it.
Further details of topography and geology will be found in books by Piot (1893)
and Fiorini (1935).
(1) Plants
No life was found above 58° C. (bacteria were not looked for), but at this tem-
perature a carpet of blue-green algae was noticeable. This carpet was continuous
Studies on the Fauna of an Algerian Hot Spring 489
down to 40-380 C. where it thinned out. The principal species found, with their
limits of distribution, were as follows:
°C.
Spirulina labyrinthiformis Gom. 58—43
Oscillatoria angustissima W. & G. S. West 58-43
O. amphibia Gom. 58—41
Symploca thermalis Gom. 4S~4X
Lyngbya aestuarii Gom. 45~39
Denticula thermalis Kiitz. (diatom) 45~33
Oscillatoria chalybea Gom. 4I~39
Oscillatoria species 4°~33
Lyngbya martensiana Gom.
These and other species of Oscillatoria have already been recorded in other
North African hot springs (Seurat & Fr^my, 1937), but only at a considerably lower
temperature (380 C). Copeland (1936), in an extensive investigation of the blue-
green algae of the Yellowstone Park, also records these species of Oscillatoria and
Spirulina at approximately the same temperatures as the present author. The
highest temperatures at which Copeland found any life where:
°C.
Bacteria (unidentified) 89
Cyanophyceae {Oscillatoria filiformis) 85-2
It should be noted that these figures refer to siliceous waters. In calcareous
springs, such as the one at Hammam Meskoutine, the maximum temperatures are
about 15-200 C. lower (Setchell, 1903).
(2) Animals
Table II shows the principal animals from truly thermal waters and the maximum
temperature at which each was consistently found. 380 C. was arbitrarily chosen as
the lowest temperature at which the stream could be considered thermal, since some
of the small pools into which the Bou Hamdam dries up in summer are heated by
the sun to a temperature just below this, viz. 360 C. They still differ, however,
from thermal waters of the same temperature in their diurnal and seasonal changes
and in the presence of cool depths to which animals can retire from the heated
surface.
About thi3 temperature (38—350 C.) the character of the stream changes owing
to the disappearance of the algal carpet and the appearance in large numbers of the
species forming the general freshwater fauna of the district, viz. ephemerid and
dragonfly nymphs, caddis worms, gyrinid beetles, water skaters, corixids, rotifers,
fresh-water oligochaetes, gammarids and free-living nematodes. To the human
hand, too, 38—350 C. marked the transition from "hot" to "lukewarm".
Setchell (1903), writing of the Yellowstone Park, counts as truly thermal
waters only those with temperatures above 43-45° C, but does not give his reasons.
He emphasizes the necessity of taking temperatures exactly where animals and
496 I. L. MASON
Table II. Distribution of principal species at Hammam Meskoutine
Max.
temp. Species Description Distribution
°C.
5i'5 Cypris balnearia Mon. Ostracod Abundant 50-40° C.
45 C. balnearia eggs and young — —
45 Species undetermined Small ciliates and flagellates —
45 Coelottoma hupamcum (KUst) Hydrophilid beetle Temporarily; at edges
only
45 Bidetna tignatelhu Keug. (var. Dytiscid beetle (Hydro- Abundant 42-36° C.
thermalisj porinae)
41 Bidestus ngnatelha larvae — —
41 Rana ridibunda perezi (Sloane) Edible frog Temporarily only; abund-
ant below 38° C.
39 R. ridibunda perezi larvae All stages summer and Abundant
winter
39 Potamon (Potamon) edulis Freshwater crab Temporarily in water; in
(Latreille) burrows at 35° C. and
Lbielow
39 Peltodytes rotundatus Axibi Haliplid beetle Rare
39 Laccophtiui kyalinus testaceus Dytiscid beetle Rare
39 CAAu.U.lUeXDxc larvae Abundant
39 CMronomus larvae Abundant
39 Anophelet larvae Abundant
39 Orthetrum (?) nymph Libellulid dragonfly Rare
39 Species undetermined Coenagrionid dragonfly Rare
nymph
39 Micronecta adults and nymphs Minute water bug Abundant
38 Barbui callensis Cuv. and val. Cyprinoid fish Abundant at 37° C. and
below
plants are found, since the bottom of a deep pool or the edges of a sluggish stream
may be at a lower temperature than the rest. This practice was invariably observed
by the present author. In addition, a careful distinction was drawn between the
maximum temperature at which specimens were found occasionally or in small
numbers, and the optimum temperature at which they live habitually. This dis-
tinction applied particularly to the two most interesting animals in the list, Cypris
balnearia and Bidessus signatellus, which are species confined to thermal waters.
The other animals of special interest are Barbus callensis and Potamon edulis, which
are widely distributed in the surrounding cool streams but have resistant races in
the hot springs. The distribution and physiology of these animals will be discussed
in the second part of this paper.
(3) The upper temperature limits for life
Previous extensive study of hot spring animals has been made by Issel (1901,
1906, 1908, 1910) for the Italian springs, and by Brues (1924, 1928, 1932) for
the American springs. The latter gives a very complete survey of the literature.
His results indicate that 410 C. is the upper limit for vertebrates and 450 C. for
most invertebrates, while a few groups (ostracods and hydracarines) are found up
to 50-51° C. These results agree very closely with mine.
From a careful investigation of the literature I have drawn up, the following
table of the maximum temperatures at which various animal groups have authenti-
Studies on the Fauna of an Algerian Hot Spring 491
cally been found (Table III). It should be noted, however, that these may represent
merely temporary maxima and the animals listed may not be able to survive pro-
longed exposure to these temperatures. This question is discussed in connexion
with the death-point of Cypris (see below).
Table III. Maximum temperatures at which the principal animal groups have
been recorded in hot springs
Group Species Temp. Author and locality
°C.
PROTOZOA Amoeba (?) hartmanella 54 Hindle (1932), Dax, France
(Rhizopoda) Hyalodiscus sp. 54 Issel (1008), Valdieri, Italy
CRUSTACEA Cypris balnearia Mon. 5i'5 Mason, Hammam Meskoutine
(Ostracoda) Potamocypris perbruttnea Blake 5° Brues (1932), Nevada
ARACHNIDA Thermacarut nevadensis 508 Brues (1932), Nevada
(Hydracarina) Marshall
NEMATODA* Dorylaimus atratus 47 Issel 1906 Abano, Italy
ROTIFERA Pkilodina roseola Ehrb. 46 Issel 1901 Vinadio, Italy
MOLLUSCA Paludestrina aponensis 46 Issel 1906 , Abano, Italy
(Gastropoda) Bythinella thermaUs 46 Issel I9o6 , Abano, Italy
INSECTA Bidessus signatellus Keug., 45 Mason, Hammam Meskoutine
(Coleoptera) several species 45-4O Brues, Issel
CRUSTACEA Potamon edulis Latreille 39 Mason, Hammam Meskoutine
(Malacostraca) Gamntarus limnaeus Smith 38 Brues (1924), Yellowstone Park
VBRTEBRATA :
Amphibia Rana pretiosa B. and G. 4i Brues (1924, 1932), Yellowstone
(adults and tadpoles) Park
R. ridibunda (temporarily) 41 Mason, Hammam Meskoutine
R. ridibunda tadpoles 39 Mason, Hammam Meskoutine
Pisces Notropis lutrensis B. and G. 39'5 Brues (1928), New Mexico
Barbus callensis Cuv. and Val. 38 Mason, Hammam Meskoutine
• Several examples of nematodes found at higher temperatures than 470 C. are given in a paper
by G. Rahm (Forseh. u. Fortsckr. 13, 1937, 381). The maximum is for Aphelencus sp. found inahot
spring at Rotorua, New Zealand. The temperature of the spring varied from 58 to 69-1° C. and was
6i'3°C. when the animals were observed. This is by far the highest temperature at which any animal
has been observed. Rahm emphasizes the great resistance to extremes of temperature of the' anabiotic'
fauna (nematodes, rotifers and tardigrades) when in the 'latent' condition but he does not make it
clear whether the records mentioned above refer to active or dormant individuals.
PART II. THE ADAPTATION OF HOT SPRING ANIMALS
TO THEIR ENVIRONMENT
Several authors (Issel, 1906; Vouk, 1923; Brues, 1932; Copeland, 1936) have
attempted to classify the fauna of hot springs according to their assumed origin,
e.g. marine, tropical,. primeval, fresh water. The assumption underlying this
method of grouping does not rest on experiment, so this classification throws no
light on the more interesting question: How are animals able to withstand the
abnormally high temperatures of hot springs? The author has divided the Meskou-
tine fauna into the following groups according to physiological differences observed
during experiments done on the spot with animals straight from the stream:
(1) Those species common in the surrounding fresh water which are merely
living nearer their thermal death-point.
(2) Those species common in the surrounding fresh water which have more
resistant physiological races living in the hot springs.
(3) Those species confined to hot springs.
492 I. L. MASON
(I) Animals living nearer their thermal death-point
Of the animals on which death-point experiments were performed only frogs
and tadpoles fell into this group, but most of the other animals whose range ends
about 37-39° C. probably belong here too.
The frogs and tadpoles were immersed in water of constant high temperature
until they died; the frogs were allowed to keep their noses out of water so that they
would not suffer from oxygen lack. From a series of such experiments the highest
temperature was determined at which they could live without showing signs of dis-
comfort for an arbitrary period of 1 hr.
Table IV. The death-point of Rana ridibunda
Temp. Time for heat rigor in Max. time frogs were
°C. lab.; frogs from 230 C. observed to remain
immersed in stream
44 Few sec. Few sec.
41 iJ-2 min. 1 min.
40 2—4 min. 2 min.
39 9—16 min. 6 min.
38 >4O min. >6 min.
c
a
e A
00
80-
60-
S
-
40 c
R
n
40-0 40-5 4IO 41-5 42-0 42-5
Temperature in ° C.
Fig. 2. The death-point of tadpoles of Rana ridibunda from habitats of different temperatures.
A. Five animals from 230 C. (summer). B. Ten animals from 32 to 34° C. (winter). C. Thirteen
animals from 390 C. (summer).
Frogs taken from cool water at 23° C. lived uninjured in the laboratory at
38° C, but heat rigor set in after a few minutes at 390 C. This is in accordance with
the observed behaviour in the field of the hot stream frogs. They spend most of
their time sitting on the bank, only diving in when disturbed and remaining
immersed for a period which varies inversely with the temperature of the water.
Table IV shows this correlation.
The death-points of the tadpoles are shown in Fig. 2. The numbers are too few
Studies on the Fauna of an Algerian Hot Spring 493
to enable definite conclusions to be drawn except that the larvae are more resistant
than the adults. There is no well-marked indication of physiological races differing
in their death-points. In any case, frogs and tadpoles, being only temporary in-
habitants of water, are not so interesting in this connexion as fish, which live there
permanently.
(2) Adaptive Physiological races
Barbels (Barbus callensis) were abundant in a large pool at a uniform summer
temperature of 37° C.; they made occasional excursions into water at 380 C. but
rigorously avoided higher temperatures. They were also present in large numbers
in all streams at temperatures below 37° C. This distribution is shown in Fig. 1.
The minimum temperature at which they were found was 8° C, in winter.
It was found that the death temperature of the fish varied according to the
temperature at which they lived. For these experiments a gradually rising tem-
perature was used rather than sudden immersion in hot water in order that the
conditions might more nearly approach those naturally experienced by the fish.
The temperature was raised rapidly to 300 C. and thereafter very slowly (between
1 and 2° C. per hour), so that at any one temperature the fish had time to regain its
balance lost, presumably, by the expansion of the gas in its swim bladder.
Fish were taken from three different habitats:
(1) A portion of the Oued Chedakra (see Fig. 1), including a hot pool and the
stream flowing out of it along which the temperature range was nearly the same
summer and winter (July 30-360 C.; January 28-340 C). Experiments in July and
January gave similar results.
(2) A part of the Bou Hamdam several miles below the entry of the Chedakra
which was unaffected by hot spring water; January temperature 8-io° C. The
July temperature was not taken at this exact spot, but by comparison with other
parts of the river it was probably 15-20° C. Death-points were taken in January
only.
(3) The Bou Hamdam near the entry of the Chedakra (see Fig. 1). Here the
July temperature was 26-30° C, in December it was 19-200 C, while in January,
when the winter rains had begun and the river was in flood, the temperature was
8-90 C. Death-points were taken both in December and January, but the same
range of variation was shown in each batch.
The results obtained are shown in Fig. 3. In each case a wide range of sizes
was used, but no distinct correlation between size and death-point was observed.
It is clear that temperature is the factor limiting the upper range of the fish,
which, in the hottest places, are living dangerously near to their thermal death-
point.
It is also clear that the fish from the hot water are more resistant to high tem-
peratures (death-points 37-40° C.) than those from the cold water (death-points
31-33° C). Since the range of death-points for the "cold" fish—which are the
normal form—is so small, the "hot" fish cannot represent merely the result of
selection by temperature from a mixed population. But the wide range of variation
494 I. L. MASON
in the "medium" group may represent a direct acclimatizing effect due to the
high, or to the high and variable, temperature, and from this group the most
resistant individuals may have been selected to colonize the hottest waters.
Similar but less conclusive results were obtained with crabs (see Fig. 4). Those
from a temperature of 32-36° C. had a death-point in both summer and winter of
No. of Temp, of htbiut, °C.
fUh July Dec. Jan.
"Cold" filh 9 c.20 8-10 8-10
"Medium" fish 41 26-30 19-20 8- 9
40 "Hot" fi»h 26 30-36 28-34 28-34
'Medium" fish
nnn
n n . . .
31 32 33 34 35 36 37 38 39 40
40
"Cold" "Hot"
fish fish
30
20
10
n _n
0
31 32 33 34 35 36 37 38 39 40
Temperature in ° C.
Fig. 3. The death-point of Barbus callensis from habitats of different temperatures.
All experiment done in winter.
39-5-40° C; those taken in summer from 20 to 25° C. died at 38-39° C. The crab
is like the frog in not spending all its time in the hot water; it lives in burrows in
the bank at a slightly lower temperature than the stream itself, only making oc-
casional excursions into the latter, presumably for feeding. It can always avoid too
high a temperature by crawling out of the water; experiment showed that it could
live out of water for at least 17 days.
Studies on the Fauna of an Algerian Hot Spring 495
38-0 36-5 39-0 39*5 40«0
Temperature in ''C.
Fig. 4. The death-point of Potamon cdulis from habitats of different temperatures. " Cool" crabs,
four animals from ao to as" C. (summer). "Hot" crabs, six animals from 3a to 36° C. (summer and
winter experiments gave similar results).
(3) Specialized hot spring animals
Bidessus signatellus. These beetles were found actively moving on the felt of
algae between 45 and 33° C. They were only found once below this temperature
in a stream which had suddenly cooled to 28 ° C. Larvae were found only where the
adults were most abundant, viz. 41-380 C. Death-points were difficult to deter-
mine, since the beetles tended to avoid a lethal temperature by crawling out of the
water. Also it was not easy to decide when an animal was dead because death was
preceded by a period of reversible heat rigor. Death always occurred at 45° C,
however, after times ranging from 20 to 75 min., so that temperature is clearly the
upper limiting factor in the field.
The nature of the lower limit is not clear. The limiting factor is not temperature,
since the beetles were unaffected even by a temperature as low as ii° C. although
below this chill coma was produced. Recovery occurred on reheating to 17*5-
23° C. according to the length of coma. Complete recovery still occurred after
more than 5 hr. below 7° C.
Cypris balnearia. This species was incompletely described by Moniez (1893).
It is being redescribed by Klie under the name of Heterocypris.
The distribution of Cypris at various temperatures in the field, and the times
for death for sudden immersion at various temperatures in the laboratory, are
shown in Tables V and VI. A comparison of these two tables shows that whereas
Cypris dies in the laboratory at 490 C. it is actually found in the field above this
temperature, viz. up to 51-5° C. A possible explanation of this anomaly is as
follows. It was shown in the laboratory (see Table VI) that temperatures between
49 and 52° C. were lethal only after some hours. Since some hundreds of individuals
tested all had the same thermal death-point, it is unlikely that the few found in the
field above 480 C. are members of a specially resistant race. It appears much
more probable that they are individuals which have made temporary excursions
496 I. L. MASON
Table V. The distribution of Cypris balnearia
Temp.
Occurrence
°C
52 Never found
5I-5-5O A few, always within reach of water cooler than 480 C.
50 -45 Abundant and in active movement feeding on algal carpet
45 -4° In solid sluggish aggregations forming brown masses at the edge of streams
4° -38- Few, inactive
Only found where water had suddenly cooled
8
Table VI. The death-point of Cypris balnearia
Temp. Time for
°C. death
53 10 min.
52 48 min.
5i-5 2hr.
49 4hr.
47 > 12 hr.
from the cooler regions near the banks, where the majority are packed in dense
masses, towards the warmer centre of the stream.
Resistance to heat seems to be correlated with resistance to oxygen lack, since
it took 3 days to kill animals in boiled water at 20-300 C. in which no oxygen could
be detected by the Winkler method.
The nature of the lower limit again does not appear to be a matter of temperature.
Cypris lived in the laboratory for at least 17 days in water at room temperature
(20-300 C), although its activity was much reduced. Chill coma occurred at
17-5° C, and on reheating recovery took place, even after the animals had been
kept for 4 hr. at a temperature below 7° C.
Possibly the abrupt disappearance of Cypris at 38-5° C. in the field is connected
with the thinning out of the algae on which it feeds, or with the appearance at this
temperature of animals which may feed upon it, e.g. fish, frogs and tadpoles, crabs
and dragonfly nymphs.
DISCUSSION
The first experimental work with a bearing on the physiology of hot spring
animals was done by Plateau (1872) on fresh-water arthropods. Although he con-
fined his actual death-point experiments to normal cool-water forms, he collected
specimens of the same species from a number of French hot springs and found that
the temperatures of these springs were in no case higher than the death-points of
his cool-water forms. Even in the absence of data on the death-points of the hot
spring specimens it seems likely that this is not a case of physiological adaptation
but merely of normal fresh-water forms living at temperatures nearer their death-
points.