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Relative Influence of Kinship and Density on MetamorphicTraits of Tomopterna brevicepsAuthor(s): Narahari P. Gramapurohit, Dheeraj K. Veeranagoudar, Bhagyashri A.Shanbhag, and Srinivas K. SaidapurSource: Journal of Herpetology, 38(4):594-599. 2004.Published By: The Society for the Study of Amphibians and ReptilesDOI: http://dx.doi.org/10.1670/53-03NURL: http://www.bioone.org/doi/full/10.1670/53-03N

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Journal of Herpetology, Vol. 38, No. 4, pp. 594–599, 2004Copyright 2004 Society for the Study of Amphibians and Reptiles

Relative Influence of Kinship and Density onMetamorphic Traits of Tomopterna breviceps

NARAHARI P. GRAMAPUROHIT, DHEERAJ K. VEERANAGOUDAR,BHAGYASHRI A. SHANBHAG, AND SRINIVAS K. SAIDAPUR

1

Department of Zoology, Karnatak University, Dharwad - 580 003, India

ABSTRACT.—Tadpoles of Tomopterna breviceps from five different sibships were subjected to pure (siblings)or mixed (kin and nonkin) rearing conditions at varying densities to determine relative influence of kinshipand density on metamorphic traits of larval growth, larval period, and size at metamorphosis. Individualrearing of 50 tadpoles from five different parental lines revealed no significant difference in any metamorphictraits among sibships. At a given density, metamorphic traits were comparable between sibling and mixedgroups indicating an absence of kinship influence. However, progressive increase in the number of tadpoles(density) affected severely the metamorphic traits regardless of the kinship/mixed rearing conditions. Thisresulted in an increase in larval period, decrease in the size of metamorphs in comparison to those reared ata lower density or uncrowded conditions. Our study shows that in T. breviceps density of rearing rather thankinship plays a major role in affecting the metamorphic traits.

Most amphibians have a free-swimming larval stagethat uses the rich resources of temporary aquatichabitats. Size at metamorphosis and duration of larvalperiod are two important metamorphic traits in anuranamphibians. Both biotic and abiotic factors are knownto influence the duration of larval period and size atmetamorphosis; these in turn have strong ecologicalimplications with respect to long-term fitness involvingjuvenile survival, age and size at first reproduction,and/or adult fecundity (Smith, 1987; Semlitsch, et al.,1988; Berven, 1990). Tadpoles of several anurans live inaggregations. Advantages of group living include thepossibility of avoiding, detecting and deterring preda-tors, enhancing foraging efficiency, accruing benefits incompetitive interactions and thermoregulation (Hoff etal., 1999). Tadpoles that form aggregations may gainone or the other benefit by cooperating with theindividuals in the group. In nature, aggregations oftadpoles may consist of kin or individuals of mixedrelatedness depending upon ecological conditions andkin discrimination abilities. In such aggregations, kin-ship is known to have positive influence on themetamorphic traits. For instance, the tadpoles of severalspecies reared with kin grew faster and developed ata uniform rate than those reared with nonkin (Wald-man, 1986, 1991; Jasienski, 1988; Smith, 1990; Girish andSaidapur, 1999, 2003; Saidapur and Girish, 2001).Further, rearing in crowded condition resulted indelayed metamorphosis, large variation in individualgrowth rates, and smaller size at metamorphosis(Alford, 1999; Girish and Saidapur, 1999, 2003; Saidapurand Girish, 2001). These results were more pronouncedwhen tadpoles were reared in mixed groups.

Tomopterna breviceps usually breeds in temporarybodies of water such as small puddles, ponds, ditches,and artificial cement cisterns, from April–Septemberfollowing premonsoon and monsoon showers atDharwad, southern India. Tadpoles of T. breviceps areoften observed in loose aggregations, and they gener-

ally metamorphose within 4–5 weeks. However, thetransient bodies of water in which they are foundsometimes dry-up in 15–20 days resulting in the deathof all tadpoles well before metamorphosis (pers. obs.).Therefore, in the ephemeral water bodies where T.breviceps bred, selection may favor rapid larval growthand metamorphosis regardless of the kinship environ-ment. However, crowding may still influence the larvaldevelopment and metamorphosis. The present studywas undertaken to test these assumptions by rearingthe tadpoles of T. breviceps with kin and nonkin (mixed)under varying densities.

MATERIALS AND METHODS

Experimental Design.—Five different egg clutches ofT. breviceps were collected from rain-filled pools on 24June 2002, in and around Karnatak University campus(158279N, 758059E). Spawns of T. breviceps are laid asa sheet of eggs floating on the surface of water. Freshlylaid egg clutches spaced at least 15–20 m apart werecollected to avoid multiple paternities. Eggs were keptin plastic containers (30 cm diameter) until hatching(within 24 h of collection). Hatchlings started feeding atGosner (1960) Stage 25, a day after hatching. In allexperiments, Stage 25 tadpoles were used. Spinachleaves cut into small pieces of uniform size and boiledwere provided as food on alternate days. Water waschanged using aged tap water prior to feeding. Theamount of food added to each container was nearlyequal and adequate. It was generally in slight excess ofwhat could be consumed by the tadpoles. On 27 June2002 the following experiments were commenced.

Experiment I.—This experiment was designed todetermine genetic components of variation, if any, ongrowth, size at metamorphosis, and larval periodamong tadpoles of different sibships as reported insome species of frogs (Travis, 1983a,b; Newman, 1988;Smith, 1999). If such variation should exist amongdifferent sibships of T. breviceps, it would be one of theconfounding factors in interpreting the results ofexperiments involving mixed groups. Therefore, thespecific null hypothesis tested in this experiment wasthat there is no significant difference in growth, size at

1 Corresponding Author. E-mail: saidapur@hotmail.com

metamorphosis, and larval period between individualtadpoles from different clutches. Ten tadpoles fromeach of the five clutches were reared individually inplastic containers (17 cm diameter) with 1 liter of water.All the containers were kept on a flat surface underuniform natural photoperiod and temperature. Posi-tions of containers were randomized on alternate daysto minimize any positional effect.

Experiment II.—In this experiment, kinship anddensity were treated in a 2 3 2 factorial design. Eachtreatment was replicated five times. The treatmentswere set as follows: Group 1—Siblings reared in 1 literof water (Sib 1L); Group 2—Siblings reared in 5 liters ofwater (Sib 5L); Group 3—Nonsiblings reared in 1 liter ofwater (Mix 1L); and Group 4—Nonsiblings reared in 5liters of water (Mix 5L).

In each group, 10 tadpoles were reared using plasticcontainers (30 cm diameter) with either 1 liter(crowded) or 5 liters of (uncrowded) water. Replicatesof Groups 1 and 2 consisted of tadpoles from a singleparental line (homogenous). Replicates of Groups 3 and4 consisted of tadpoles (2 each) from all five clutches(heterogeneous).

Experiment III.—This experiment was designed todetermine (in addition to the effects of kinship anddensity) the nature of competition among individuals(reared as kin or nonkin groups) at higher densities.Kinship and density were considered in a 233 factorialdesign leading to six treatment groups, each replicatedfive times (30 containers in total). The experimental setup was as follows: Group 1—Low-density siblinggroup, 10 siblings in 5 liter of water (Sib 10);Group 2—Medium-density sibling group, 25 siblingsin 5 liters of water (Sib 25); Group 3—High-densitysibling group, 50 siblings in 5 liters of water (Sib 50);Group 4—Low-density mixed group, 10 nonsiblings in5 liters of water (Mix 10); Group 5—Medium-densitymixed group, 25 nonsiblings in 5 liters of water (Mix25); and Group 6—High-density mixed group, 50nonsiblings in 5 liters of water (Mix 50).

In this experiment, the quantity of water remainedconstant while number of tadpoles and, thus, densityvaried. Replicates of Groups 1–3 contained tadpoles

from each of the five parental lines. In replicates ofGroups 4–6, all five clutches contributed tadpoles (two,five, and 10, respectively) and, thus, were heteroge-neous. Each container received 3 g of food during thefirst week followed by 6 g in the second and, 12 g fromthird week onward until metamorphic climax. Rationof food was increased progressively to meet the intakeneeds of growing tadpoles. The null hypothesis testedin Experiment II and Experiment III was that kinshipand density have no significant effect on growth andmetamorphic traits of T. breviceps tadpoles when rearedunder different social situations/densities.

To determine whether different sibships exhibitgenetic differences in their ability to grow (larvalgrowth and size at metamorphosis) and metamorphose(larval period), individuals from all the treatments(except the third experiment) were weighed on the 10thday following hatching and subsequently, at six-dayintervals until all the individuals metamorphosed.Tadpoles were removed from water, blotted dry asquickly as possible using blotting paper, and thenweighed. On reaching Stage 43–44, tadpoles from alltreatment groups were maintained separately in glassaquaria placed slanted, with water at one end until tailwas resorbed (Stage 46).

There was no mortality in any treatment group. Ina replicate of Group 4 of Experiment II, one tadpoleremained very small throughout, and it was discardedat the end of the experiment. At metamorphosis bodymass, snout–vent length (SVL) and larval period foreach treatment group were recorded.Statistical Analysis.—Data on body mass, SVL, and

larval period were log-transformed to meet assump-tions of normality. Data on variations in the body mass,SVL, and larval period of individuals of differentparental lines reared in isolation were compared bymultivariate analysis of variance (MANOVA) afterconfirming homogeneity of variances. Data on bodymass of individuals recorded at intervals in isolated

FIG. 1. Body mass (mean 6 SE) of Tomopternabreviceps tadpoles of different parental lines (P1–P5)reared in isolation throughout the larval period and atmetamorphosis (M).

FIG. 2. Changes in body mass during larval de-velopment of Tomopterna breviceps in sibling and mixedgroups reared at different densities. Note a significantdifference in the body mass at the end of the forthweek in low densities (Sib 5L and Mix 5L) compared tothat in high-density (Sib 1L and Mix 1L) groups.

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rearing groups from each parental line were analyzedby repeated measures of ANOVA. Difference in bodymass, SVL, and larval periods in different treatments inExperiment II were analyzed using MANOVA afterconfirming the homogeneity of variances, whereasinteraction of kinship and density was analyzed byunivariate analysis to determine effects of each factorseparately. A two-way ANOVA was performed on eachresponse variable (body mass, SVL, and larval period)within each main effect to determine effects of kinshipand density. Body mass recorded at different intervalsin various treatment groups was compared using one-way ANOVA. As individuals in a given container werenot independent, group means were used for analysisin ANOVA and MANOVA.

In Experiment III, since variances among replicateswere heterogenous, log-transformed data were used

instead of group means. Because size (mass) ofindividuals within and between groups also varied inthis experiment, the ratio (in mass) of the largest andthe smallest individual to the mean mass of all theindividuals in a replicate was calculated and log-transformed. To determine any deviation from log-normal distribution, Lilliefor’s test of normality wasemployed on log-transformed ratios. The largest andthe smallest ratios were used as response variables inour ANOVA/MANOVA designs. The ratio considerssize distribution of froglets in each replicate and allowsevaluation of the tendency of few individuals to growlarger or metamorphose at smaller size over theremaining larvae (Van Buskirk and Smith, 1991; Wallsand Blaustein, 1994; Saidapur and Girish, 2001). Effectof density alone on the metamorphic traits in siblingand mixed groups was analyzed by one-way ANOVAfollowed by Scheffe’s multiple comparison test. Allstatistical tests were performed using SPSS software(vers. 6.0).

RESULTS AND DISCUSSION

When tadpoles of T. breviceps were reared in isolation,there was no significant variation in growth ofindividuals over time among the five parental linestested (Experiment I; repeated measures of ANOVA,F 5 0.872, P . 0.05; Fig. 1). Mean body mass (max.0.43060.03 g and min. 0.40060.01 g), SVL (max. 14.960.03 mm and min. 14.6 6 0.03 mm) and duration oflarval period (max 33.5 6 0.4 days and min 31.16 0.38days) among metamorphs of five parental lines rearedin isolation were comparable (MANOVA; Wilks’slambda 5 00.736, F 5 1.165, P 5 0.316).

Rearing a fixed number of tadpoles as kin or mixedgroups in either 1 liter (high density) or 5 liters (lowdensity) of water caused no significant variation in the

FIG. 3. Effects of kinship and density on meta-morphic traits of Tomopterna breviceps. Figures inparentheses indicate the number of replicates. Com-parisons are made between sib groups or mixedgroups and also between sib and mixed groups ata given density. Dissimilar alphabets over the barsindicate significant differences between the groups.

TABLE 1. Results of MANOVA for overall effects ofkinship, density and their interaction and two-wayANOVA for each response variable within a maineffect. Response variables are mean mass (g), SVL(mm) of metamorphs, and mean duration of larvalperiod (days) per replicate.

Source Wilk’s F df P

A. MANOVA for overall effectsKinship 0.651 2.500 3, 16 0.102Density 0.231 15.493 3, 16 0.001*Kinship 3 Density 0.806 1.121 3, 16 0.374Source MS F df P

B. Two-way ANOVA for mean massKinship 0.00 0.61 1 0.448Density 0.03 46.32 1 0.0001*Kinship 3 Density 0.00 0.64 1 0.437

C. Two-way ANOVA for mean lengthKinship 0.00 1.48 1 0.241Density 0.00 6.30 1 0.023*Kinship 3 Density 0.00 2.54 1 0.130

D. Two-way ANOVA for mean larval periodKinship 0.00 0.03 1 0.866Density 0.00 8.25 1 0.011*Kinship 3 Density 0.00 1.05 1 0.320

* indicates significance at 0.05 level.

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growth of the tadpoles (body mass) with respect to pureor mixed groups (Fig. 2). The pattern of growth oftadpoles, however, varied depending upon the densityof rearing, especially during the last week of theirprometamorphic life. During the first three weeks,density had little effect on growth of tadpoles, but at theend of the fourth week, body mass of individuals athigher density remained significantly lower comparedto those reared at lower density regardless of whetherthey belonged to kin or mixed groups (Fig. 2). Bodymass, SVL, and larval period of metamorphs of kin andmixed groups were also comparable (Table 1; Fig. 3). Atlower density (reared in 5 liters), size at metamorphosis(body mass and SVL) was larger regardless of thegroup (sibling or mixed) composition (Fig. 3A, B). Thelarval period was inversely correlated with rearing

density. A combined interactive effect of kinship anddensity on the metamorphic traits was insignificant.

In Experiment III, where varying number of tadpoles(N 5 10, N 5 25, or N 5 50) were reared, either assibling or mixed groups in fixed quantity of water (5liters), metamorphic traits were comparable betweenpure and mixed groups for a given density (Fig. 4A–C).A progressive increase in density of rearing led toa significant decline in mean body mass and SVL andan increase in larval period in sibling as well as mixedgroups (Table 2). Further, the size at metamorphosiswas inversely related to density of rearing. In mixedgroups, at all density levels (low, intermediate, andhigh), although size variation between the largest andthe smallest individuals was greater, it was insignificantin comparison to the kin group (Table 3). A possibleinteractive effect of kinship and density on mean bodymass, SVL, or larval period was insignificant (Table 2).

The present findings for T. breviceps tadpoles reared inisolation reveal no genetic effect on larval growth andmetamorphic traits and conform with findings for Bufomelanosticus (Saidapur and Girish, 2001). Nevertheless,genetic effects, if any, may be expressed in tadpoleswhen exposed to different social situations such as

FIG. 4. Effects of kinship and density on body mass(A), SVL (B), and larval period of Tomopterna brevicepsat metamorphosis (mean 6 SE). Figures in parenthesesindicate the number of replicates. Dissimilar alphabetsover the bars indicate significant difference betweenthe groups. Asterisks over the bars indicate nosignificant difference between these groups.

TABLE 2. Results of MANOVA for overall effects ofkinship, density and their interaction, and two-wayANOVA for each response variable within a maineffect. Response variables are mean mass (g), SVL(mm) of metamorphs mean duration of larval period(days) per replicate, and mean mass of largest andsmallest individuals.

Source Wilk’s F df P

A. MANOVA for overall effectsKinship 0.998 0.791 1, 844 0.499Density 0.330 206.83 2, 844 0.0001*Kinship 3 density 0.994 0.800 2, 844 0.569Source MS F df P

B. Two-way ANOVA for mean mass

Kinship 0.00 0.02 1 0.879Density 1.44 244.08 2 0.0001*Kinship 3 density 0.01 1.080 2 0.341

C. Two-way ANOVA for mean length

Kinship 0.00 0.05 1 0.823Density 0.15 204.87 2 0.0001*Kinship 3 density 0.00 0.15 2 0.865

D. Two-way ANOVA for mean larval period

Kinship 0.00 1.59 1 0.208Density 0.58 255.12 2 0.0001*Kinship 3 density 0.00 0.31 2 0.733

E. Two-way ANOVA for largest individuals

Kinship 0.00 1.76 1 0.197Density 0.01 5.04 2 0.015*Kinship 3 density 0.00 1.82 2 0.184

F. Two-way ANOVA for smallest individuals

Kinship 0.00 0.01 1 0.921Density 0.00 3.56 2 0.044*Kinship 3 density 0.00 2.10 2 0.144

* indicates significance at 0.05 level.

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association exclusively with siblings or with nonkin.However, the results of Experiment III do not supportthis view. Instead, the findings support our nullhypothesis that there is no significant difference ingrowth and metamorphic traits among tadpoles ofdifferent parental lines. In contrast, studies on Pseudacristriseriata (Travis, 1980), Hyla gratiosa (Travis, 1983),Scaphiopus couchii (Newman, 1988), and Rana catesbeiana(Smith, 1999) have revealed variation in the growth andmetamorphosis among tadpoles of different parents.Therefore, genetic effects on larval growth and meta-morphosis may be species specific and depend onecological conditions.

Previous studies have shown that influence ofkinship on metamorphic traits varies across species.For instance, Rana arvalis tadpoles grew more quicklyand metamorphosed in higher number when rearedwith nonkin or in water conditioned with nonkin incomparison to those reared as kin, indicating an intensecompetition among genetically similar individuals(Shvarts and Pyastolova, 1970). However, tadpoles ofB. melanostictus, R. temporalis, and P. triseriata grew welland metamorphosed at larger size when reared inassociation with siblings (Girish and Saidapur, 1999,2003; Saidapur and Girish, 2001; Smith, 1990). Also, inB. melanostictus and R. temporalis, size of the individualsin sibling groups was less variable than those of mixedgroups, indicating a positive influence of kinship onlarval growth and metamorphic traits. In contrast, thepresent study on T. breviceps reveals that a kinshipenvironment has no influence on larval growth anddevelopment, the metamorphic traits (body mass andSVL), and larval period. Furthermore, the size distri-bution of individuals in both sibling and mixed groupsreared under uncrowded conditions was uniformindicating an absence of competition among differentsibships as observed in B. americanus (Waldman, 1991).

The findings of both Experiment II (where number oftadpoles was constant but water quantity varied) andExperiment III (where water quantity was constant butthe number of tadpoles varied) support the generalview that crowding has a negative influence on growthrate of tadpoles, resulting in a smaller size at meta-morphosis and an increase in larval period (Alford,1999; Girish and Saidapur, 1999, 2003; Saidapur andGirish, 2001). Although crowding had no significanteffect on premetamorphic growth and development inT. breviceps, it affected the prometamorphic growthresulting in a smaller body size. Thus, the effect ofdensity rather than kinship on larval growth wasspecifically manifested during the final stages of meta-morphosis.

Apparently, effects of kinship on growth and de-velopment of anuran tadpoles vary in different speciespossibly depending upon the kin discriminationabilities and also ecological conditions. For instance,tadpoles of R. temporalis (unlike T. breviceps) are foundmostly in large bodies of water and as such do not facethe levels of desiccation and crowding. Therefore,tadpoles of R. temporalis take much longer (3–4 months)to metamorphose, whereas T. breviceps metamorphosewithin a month or so. The tadpoles of both B.melanostictus and T. breviceps often face similar ecolog-ical conditions but differ in their kin discriminationability. Hence, variation in the effect of kinship anddensity on metamorphic traits in the two species is notsurprising. In B. melanostictus, kinship environmentpromotes synchronous development, faster growthresulting in a large size at metamorphosis, whereas inT. breviceps, kinship effects on larval traits, if any, areoverridden by density or crowding when faced withdesiccation, possibly caused by intense competitionamong the members of the aggregation.

Acknowledgments.—The work was supported bya grant SP/SO/C-29/2000 from Department of Scienceand Technology (DST), New Delhi awarded to SKSand partly by UGC SAP-II New Delhi. DKV is a juniorresearch fellow in the DST grant. NPG is grateful toCouncil of Scientific Industrial Research, New Delhi fora senior research fellowship.

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Accepted: 18 August 2004.

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