Zago, Marlene Sofia Arcifa

English

Cadernos Espinosanos (E-Journal)

Bolm. Zool., Univ. S. Paulo  1:147-160, 1976A preliminary investigation on the eyclomorphosis of Daphnia gessneri Herbst, 1967, in a Brazilian reservoirMARLENE SOFIA ARCIFA ZAGOA B S T R A C TThe  eyclom orphosis of a  natural population of Daphnia  (D . gessneri H erbst, 1967) in Am ericana Reservoir (B razil) is investigated during one year.T he structures considered w ere helmet, head basis, carapace and spine of carapace, m easured in two ins ta rs : new born and last stage  adult. T he relative length of the helm et and of the spine showed variation  in time, w ith sum m er incre­ment, while the head basis show ed a less expressive variation.T hree environm ental factors w ere considered: tem perature, turbulence and nutrition. T here are  no linear correlation betw een the ratios he lm et/carapace, sp ine/carapace  and the tem perature, but the la tte r seem s to have influenced above a limit (25°C). N utrition, estim ated indirectly through  the egg  production, seem s to have affected the proportions, but the cyclical variation  of food is difficult to evidence in the environment. It is possible th a t the relative length of the mentioned structu res w as influenced by the jo in t action of the three factors.The eye size w as also considered, being sm aller in the low helm eted form.I N T R O D U C T I O NThe eyclomorphosis in Cladocera, mainly in species of Daphnia, was investigated in detail in temperate regions. In tropical and subtropical ones, generally speaking, observations withouth mensuration data were made.The investigations, based on laboratory populations, natural popula­tions, or both, have searched the causes and the adaptive value of eyclomorphosis. The environmental factors more intensely investigated as possible causes were: temperature (Ostwald, 1904; Wesenberg-Lund, 1926; Coker and Addlestone, 1938; Brooks, 1946; Jacobs, 1961a; Hazel­wood, 1962, and Egloff, 1968), turbulence (Brooks, 1947; Hrbâcek, 1959, and Jacobs, 1961a), turbulence allied to light (Jacobs, 1962, and Hazel­wood, 1966), and nutrition (Coker and Addlestone, 1938; Brooks, 1946, and Jacobs, 1961a).The adaptative value is still a very discussed theme. The hypotheses are concerned with density and viscosity of the water and the buoyancy of the organisms, defended by Ostwald and Wesenberg-Lund; with stabi­lization and direction of the animal (Woltereck, 1909); with predation (Brooks, 1965; Green, 1967; Jacobs, 1967, and Dodson, 1974). It was even suggested that this variation of form has no adaptive meaning, although Jacobs (1961b) searched to prove the contrary.This paper deals with an attempt to verify the occurrence of cyclo- morphosis in a species in tropical conditions and to test the factors known as important in the process in temperate zones. The lack of knowledge on the subject in tropical regions makes it exceedingly hard to extend the conclusions from researches in temperate regions to our latitudes.In this work an analysis is done of the monthly variation of the relative length of the head (divided in two parts) and of the spine of the carapace of Daphnia gessneri in two instars —  newborn and adult — during one year (with a gap of two months). The factors to which the structure are related a r e : temperature, turbulence and nutrition. The results, however, are preliminary and intend to be a basis for further studies.I would like to express my deepest thanks to Dr. Claudio G. Froehlich, Dr. Antonio Carlos Azevedo and Miss Gisela Y Shimizu.MATERIAL AND METHODSAmericana Reservoir is located in São Paulo State, Brazil, 22°44’20” S Latitude and 49°19’52” W  Longitude.The samples were collected monthly at Station 6 (see Zago, 1976) from June, 1969 to June, 1970. Sampling was made with a net 85 ./¿m- meshed through vertical hauls.In the present work the attempt to utilize the allometric analysis introduced by Brooks (1946) failed, for k is not constant through the instars. In such case, two stages were chosen: newborn and last stage adult.From each sample 36 newborn and 50 egged parthenogenetic females were measured. Each specimen was measured in profile, at the micros­cope with the help of a camera lucida. The eggs were counted and the averages of eggs per adult were computed.In fig. 1, the measured regions are delimited by parallel lines. The head is divided in two parts (according to Jacobs, 1961b): the helmet (E ) ,  delimited by the apex of the head and the anterior limit of eye pigmentation, and the basal part (B ), whose posterior delimitationis the tangent to the head limit. The carapace (C) is posteriorly limited by the line that passes by the end of the opening of the carapace, shown in the same figure. The spine (S) is measured from this line to the end.The length of the measured structures —  helmet, basis of head and spine —  was related to the carapace length —  E/C , B /C  and S /C . The average, the standard deviation and the confidence interval (9 5 % ) were calculated for each sample.The temperature values represent averages from superficial and deep water temperatures.The eye, from last instar adults, was measured according to Zaret (1972) at the microscope with a camera lucida. Twenty specimens were obtained from the samples of 2 5 /9 /6 9  and 28 /1 /70 .Fig. 1 —  Outline of adult female of D aphnia gessneri, in profile, showing the measured regions. E —  Helmet; B —  Basal p a r t  of head; C —  Carapace;S — Spine of carapace.Fig. 2 —  Outlines of high and low helmeted forms.R E S U L T Sa. Seasonal variation in the newbornThe ratio helmet/carapace (E /C ) ,  head basis/carapace (B /C ) ,  and spine/carapace (S /C )  reflects the prenatal relative growth.Fig. 3 shows the variations of the ratio averages, being noticeable the fall of E /C  and S /C  in July and September, followed by an increase that culminates in January, 28. In the same figure a similar development of these two curves can be noticed, there being positive and significant correlation between them (fig. 4; r =  +  0 .83 , p <  0 .0 0 1 ) .  B /C  shows a pronounced fall in September like the other two curves. Generally the development of B /C  is more irregular and the curve has a narrower range of variation.Correlation with temperatureThe embryonic development in laboratory conditions at an average temperature of 21°C, has taken about 3 days. So, it is possible to assumethat in the environment, the newborns had developed a few days before sampling. This stage is, then, the nearest to the environmental dataobtained at the moment of sampling.In the relationship of the ratios E /C , B /C  and S /C  with the instan­taneous temperatures (figs. 5A, B, C) the points are scattered. Thecorrelation coefficients (r =  +  0 .19 , r =  +  0 .3 0  and r =  +  0 .30 ,respectively) are not significant (p >  0 . 1).Fig. 3 —  V ariation of tem perature  and of E /C , B /C  and S /C  in the new borns. Solid circles represen t the means.Fig. 4 — Regression of E /C  on S /C  in the newborns.Correlation with nutritionIt is difficult to establish directly the nutritional state of the animals in natural conditions. Assuming that the adults spend a great amount of energy in reproduction, the nutritional state could be estimated through the numbers of eggs produced.The nutritional condition of the female can affect the size of the newborn (Green, 1956). Thus, E /C , B /C  and S /C  were related to the average ntimber of eggs per adult. There is linear correlation between E /C , S /C  and the number of eggs (r =  +  0 .74 , 0.001 <  p <  0 .0 1 )  in both cases (figs. 6A, C). There is no linear correlation between B /C  and the number of eggs, (r =  +  0 .30 , p >  O . i ;  fig. 6B).b. Seasonal variation in the adultThe ratios E /C , B /C  and S /C  point out the postnatal relative growth.Observing fig. 7, a similar trend is noticeable in the development of the curves E /C  and S /C  and the newborn E /C  and S/C. The range of variation of B /C  is narrower than in the newborns, only the fall in September being proeminent.E /C  and S /C  show a similar pattern, there being a positive and significant linear correlation between them (fig. 8; r = + 0 .64,0 .0 2  <  p <  0 .0 5 ) .Correlation with temperatureActually the adults were subject to a greater range of temperature, than that shown by the instantaneous values. However, as intermediate values were not available the instantaneous ones were used, by necessity.Fig. 7 —  V ariation of tem perature, of num ber of eggs per adu lt and of E /C , B /C , S /C  in the adults. Solid circles represent the means.Fig. 8 —  Regression of E /C  on S /C  in the adults.U\Lü18 20 Tz TT 26 28° C t e m p .tJ\cnt emp .CJ 0.610-\ co0.570-“ 1-------1 1-----24 26 2 8 »C t e m p .Figs. 9A, B, C T he relationship between E /C , B /C  and S /C  in the adults, respectively, and the tem perature.There is no correlation between E /C , B /C, S /C  and the tempera­tures: r =  +  0 .2 0  (p >  0 .1 ) ,  r = +  0 .52  (0 .0 5  <  p <  0 .1 )  and r =  +  0 .5 2  (0 .0 5  <  p <  0 .1 ) ,  respectively (figs. 9A, B, C).S/C B/C E/CCorrelation with nutritionThe correlation between E /C , S /C  and the number of eggs issignificant: r =  +  0 .6 2  (0.02 <  p <  0 .0 5 )  and r =  +  0 .67(0.01 <  p <  0 .0 2 ) ,  respectively (figs. 10A, C). There is no linearcorrelation between B /C  and the number of eggs (fig. 10B): r =  — 0 .4 4(p >  0 . 1).Eye sizeThe average of the eye diameter in high-helmeted specimens (2 8 /  1/70; N =  20) was 0 .063  mm and of low-helmeted specimens (2 5 /9 /6 9 ;  N =  20) was 0 .055  mm. The difference between the means is significant (t =  3 .1 7 ;  0.001 <  p <  0 .0 1 ) .D I S C U S S I O NZaret (1972) suggests that in tropical regions occur polymorphism with cohabitation of forms and no cyclomorphosis. The present work is not based on the study of spatial distribution of the species but on samples collected in one station in the middle of the reservoir. Nevertheles, the results based on a significant number of specimens seem to show a certain coherence in the variation of the proportions of the structures, pointing out to the existence of a variation in time. In the future there is a plan to carry on the research on the theme, including the spatial distribution, having in view the confirmation of the results obtained here.The pattern of variation of the relative length of the helmet and of the spine are similar in each one of the instars, as well as between the two instars. There are few data concerning the relative length of the spine, but the results presented differ from the related by Brooks and Hsi Ming (in Hazelwood, 1962) that observed an inverse relationship between the ratios spine/carapace and head/carapace.The head always presented an apical lengthening (helmet), and the rounded form was not found. From the two regions of the head, the one that seems more sensitive to the considered factors is the helmet, agreeing with the results obtained by Jacobs (1961b) in experiments with D. galeata mendotae.Concerning the prenatal relative growth, generally speaking, the authors agree that temperature is an important factor. Coker and Addle- stone (1938), Brooks (1946), Jacobs (1961a), and Egloff (1968) detected its influence upon the head development during the embryonic period. Differing from the results presented by these authors, in relation to other species, there is no linear correlation between the relative growth of the helmet and of the spine of D. gessneri and the temperature, in the em­bryonic phase. In the same way, the ratios E /C  and S /C  of the adults are not linearly related with this factor. On the other hand, the increase of E /C  and S /C , in the newborns and adults, when the temperature reached values higher than 25°C, suggests the influence of this factor above the mentioned limit. The existence of a limit of temperature was observed by Brooks (1946) related to D. retrocurva in Bantam Lake;tachyauxesis of the post natal growth of the head occurred at temperatures above 19°C.Other factor to consider in Americana Reservoir is turbulence. In 1969, the dry season was exceptionally intense from April to October. The following summer rains were particularly strong and the intensifi­cation of the drainage of Atibaia River could have increased the turbulence in the reservoir. Independently of this year, an increase of the river drainage during the wet season (October-March) always occurs. Mainly concerning postnatal growth, turbulence seems to be an important factor (Brooks, 1947; Hrbacek, 1959). Jacobs (1961a) detected its influence in experiments at 14°C, on the postnatal as well as on the prenatal growth of D. galeata mendotae, considering, however, difficult to extend this conclusion to the natural environment.The influence of nutrition, supported by Woltereck, is controversial, and Brooks (1946) do not believe it to be related with the pre and postnatal growth of the head. Jacobs (1961a), nevertheless, ascertained that starvation had a depressor effect on the relative growth rate, at 24°C. Concerning D. gessneri nutrition seems to have influenced the development of the helmet and spine in the two stages, during the observed period. However, in opposition to temperature and turbulence, the existence of cyclic variation of available food in the reservoir is not evident, the influence of nutrition, as a isolated factor, upon the cyclomorphosis of D. gessneri being questionable. In September, 1969, occurred a water bloom of the blue green alga Anabaena spiroides, what seems to have affected the relative growth. On that occasion, the substances excreted by the algae affected either directly the development or indirectly through the influence on the organisms suitable as food. It is hard to assert with certainty, but the occurrence of ephippial females in relatively large numbers on that occasion (Zago, 1976), could be a sign of starvation (Hutchin­son, 1967).As Brooks (1946) and Jacobs (1961a) suggest, mainly in relation to the postnatal growth, but which in this work may also apply to the prenatal growth, the cyclomorphosis of gessneri could be the result not from the action of a single factor, but from the joint action of some factors as temperature, turbulence and nutrition. Brooks (in Hazelwood, 1962) verified that in D. longiremis the cyclomorphosis is the result of the influence of temperature and turbulence.The structural variations presented by gessneri are, however, not as pronounced as compared with species from temperate regions.With regard to the eye, the results are contrary to those obtained by Zaret (1972) with other species of Daphnia. In gessneri the high helmeted form has a bigger eye. Nevertheless, the difference is small, the reduction in the low helmeted form being of 12,7 per cent. Anyway, this difference seems to be very small to be distinguished by predators.L I T E R A T U R EBROOKS, J. L. —  1946 —  Cyclom orphosis in D aphnia.  I .  An an a lysis o f D. re tro cu rv a  and D. ga lea ta .  Ecol. Monogr.,  16 (4 ):  409-447.BROOKS, J. L. —  1947 —  Turbulence as an environm ental determ inant o f re la tiv egrow th  in Daphnia. Proc. N at .  Acad. Sei., 33: 141-148.BROOKS, J. L. -—- 1965 —  Predation  and rela tive  helm et size in cyclom orphic Daphnia.  Proc. Nat.  Acad. Sei. U . S . ,  53: 119-126.COKER, R. E. and H. H. ADDLESTONE —  1938 —  In flu en ce of tem perature on cyclo- m orphosis in Daphnia  longispina. J. Elisha M itchell  Sei. Soc., 54: 45-75.DODSON, S. I. —  1974 —  A daptive change in plankton  m orphology in response tosize-se lective  predation: A new  hypothesis of cyclom orphosis. Limnol.  Oceanogr.,19 (5 ): 721-729.EGLOFF, D. A. —  1968 —  The re la tive  grow th  and seasonal variation  of severa l cyclo­m orphic structures of D aphnia  catavoba  Coker in n atu ra l populations. Arch.Hydrobiol. ,  65 (3 ):  325-359.GREEN, J. —  1956 —  Growth, size and reproduction in Daphnia  (C rustacea-C ladocera). Proc. Zool. Soc. Lond.,  126: 173-204.GREEN, J. — 1967 —  The distribution  and variation  of Daphnia  lu m h oltz i  (C rustacea- Cladocera) in relation  to fish  predation in Lake Albert, E ast A frica. Proc. Zool. Soc. Lond., 151: 181-197.HAZELWOOD, D. H. —  1962 —  T em perature and photoperiod e ffec ts  on cyclom orphosis in Daphnia. L imnol. Oceanogr.,  7 (2 ):  230-232.HAZELWOOD, D. H. —  1966 —  Illu m in ation  and turbulence effects  on re la tive  grow th  in Daphnia. Limnol. Oceanogr.,  n  (2 ): 212-216.HRBÁCEK, J. —  1959 —  C irculation of w ater as a m ain factor in flu en cin g  the  develop­m ent of h elm ets in D aphnia  c u cu lla ta  Sars. H ydrobiologia ,  13: 170-186.HUTCHINSON, G. E. —  1967 -— A T reatise  on L im nology  2: In troduct ion  to L ake  Bio­logy and the  L im noplankton .  N ew  York, John W iley & Sons, Inc. 1115 pp.JACOBS, J. —  1961a — Cyclom orphosis in Daphnia  g a le a ta  m e n d o ta e  B irge, a case of environm enta lly  controlled allom etry. Arch. Hydrobio l. ,  58: 7-71.JACOBS, J. —  1961b —  On the regu lation  m echanism  of en v iron m en ta lly  controlled  a llom etry (heterauxesis) in cyclom orphic Daphnia. Physiol. Zool., 34: 202-216.JACOBS, J. —  1962 —  L ight and turbulence as co-determ inants of re la tive  grow th  rates in  cyclom orphic Daphnia. In t. Rev .  ges. Hydrobiol. ,  47: 146-156.JACOBS, J. —  1967 —  U ntersuchungen zur F unktion und E volu tion  der Zyklom orphose bei Daphnia ,  m it besonderer B erücksich tigung der Selek tion  durch Fische. Arch.  Hydrobiol. ,  62 (4 ):  467-541.OSTWALD, W. —  1904 —  E xperim entele U ntersuchungen über den Saisonpolym orphism us bei Daphniden. Arch. E n tw ick .  Mech.,  18: 415-451.W ESENBERG-LUND, C. —  1926 —  C ontribution to the biology and m orphology of the genus Daphnia. K. D anske Vidensk. Selsk.  Skr. , N atur .  M athem .,  11 (2 ):  91-250.WOLTERECK, R. —  1909 —  W eitere experim entele  U ntersuchungen über A rtveränderung, speziel über das W esen q u an tita tiver  A rtunterschiede bei Daphniden. Verh. Zool. Ges., 19: 110-172.ZAGO, M. S. A. —  1976 —  The p lanktonic Cladocera (C rustacea) and aspects o f t h e ' entrophication of A m ericana R eservoir (B razil). Bolm. Zool., 1: 105-145.ZARET, T. M. —  1972 —  Predators, invisib le prey, and aspects of polym orphism  in the  Cladocera (c lass C rustacea). Limnol. Oceanogr. , 17 (2 ): 171-184.A d r e s s : D epartam ento de Zoologia, In stitu to  de B iociências, U niversidade de São Paulo.C aixa P ostal 20.520, São Pairlo, Brasil.

A preliminary investigation on the cyclomorphosis of Daphnia gessneri Herbst, 1967, in a Brazilian reservoir

https://www.revistas.usp.br/bolzoo/article/download/121575/118478/

A preliminary investigation on the cyclomorphosis of Daphnia gessneri Herbst, 1967, in a Brazilian reservoir

Abstract

Similar works

Full text

Available Versions

Cadernos Espinosanos (E-Journal)