173
P eda o y in e ac ions be ween wo global aqua ic in ade s
beyond hei na i e anges: An expe imen al app oach
And ey N. Reshe niko 1, A ina O. Raldugina1, Dmi iy V. G inchenko2, A em A. Kido 2,
Niki a G. Pla ono 1, And ey B. Pe o skiy1
1 Se e so Ecology and E olu ion Ins i u e, Moscow, Russia
2 Russian S a e Ag a ian Uni e si y–MTAA, Moscow, Russia
Co esponding au ho : And ey N. Reshe niko (an [email p o ec ed])
Copy igh : © And ey N. Reshe niko e al.
This is an open access a icle dis ibu ed unde
e ms o he C ea i e Commons A ibu ion
License (A ibu ion 4.0 In e na ional – CC BY 4.0).
Resea ch A icle
Abs ac
The widesp ead dis ibu ion o in asi e species ine i ably leads o he eme gence o a new ca ego y
o bio ic ela ionships: in e speci ic p eda o y in e ac ions be ween in asi e species. We assessed he
ulne abili y o di e en li e s ages o he clawed og, Xenopus lae is (eggs, ha chlings, adpoles, new-
ly-me amo phosed ogle s, and adul s), o p eda ion by he Eas e n mosqui o ish, Gambusia holb ooki,
and e alua ed whe he adul clawed ogs p ey upon ju enile and adul mosqui o ish. The esul s con-
i m di e ences in he pala abili y o di e en on ogene ic s ages o he clawed og by mosqui o ish, as
well as he low pala abili y o mosqui o ish o adul ogs, wi h he excep ion o ish ju eniles, which
a e ela i ely p o ec ed in he ligh bu highly ulne able unde low-ligh condi ions. The e o e, hese
ish-amphibian in e ac ions a e complex and can be de ined as unequal bidi ec ional p eda ion: he mos-
qui o ish eadily elimina es i s ea ly-s age opponen , bu may become p ey o i s adul indi iduals. The
e ealed exis ence o a ulne able mosqui o ish s age makes i di icul o p edic he uncondi ional sup-
p ession o clawed og popula ions by his ish species when hese wo global aqua ic in ade s become
syn opic in new egions. In any case, mosqui o ish a e likely o domina e in u ban wa e bodies in loca-
ions wi h cons an a i icial ligh ing. We emphasise he impo ance o s udying in e ac ions a all on-
ogene ic s ages, as well as aking in o accoun he li es yle o he o ganisms s udied when analysing he
mechanisms o p eda o y in e ac ions be ween any pai s o in asi e species in new a eas o he plane .
G aphical abs ac
Academic edi o : Filipe Ribei o
Recei ed:
30 Decembe 2024
Accep ed:
17 June 2025
Published:
7 Oc obe 2025
Ci a ion: Reshe niko AN, Raldugina
AO, G inchenko DV, Kido AA, Pla ono
NG, Pe o skiy AB (2025) P eda o y
in e ac ions be ween wo global
aqua ic in ade s beyond hei na i e
anges: An expe imen al app oach.
In: Anas ácio P, Ribei o F, Chainho P
(Eds) In asions in Aqua ic Sys ems.
NeoBio a 102: 173–189. h ps://doi.
o g/10.3897/neobio a.102.145644
NeoBio a 102: 173–189 (2025)
DOI: 10.3897/neobio a.102.145644
Ad ancing esea ch on alien species and biological in asions
A pee - e iewed open-access jou nal
NeoBio a
ecosys ems change on he global scale; assessmen o newly es ablished
p eda o y in e ac ions has o include di e se on ogene ic s ages and ake
in o accoun he li es yle o he s udied o ganisms
Ame ican Eas e n mosqui ofish
in he da k only
Global in ade s encoun e in egions beyond hei na i e dis ibu ions
complex sys em o in ade -in ade in e ac ions
A ican clawed og
174
NeoBio a 102: 173–189 (2025), DOI: 10.3897/neobio a.102.145644
And ey N. Reshe niko e al.: In e ac ions o wo global aqua ic in ade s
Key wo ds: Gambusia holb ooki, Global in asions, in asion ecology, p eda o y in e ac ions,
Xenopus lae is
In oduc ion
The widesp ead dis ibu ion o in asi e species ine i ably leads o he eme gence o a
new ca ego y o bio ic ela ionships: in e speci ic in e ac ions be ween in asi e species.
Such in e ac ions may be neu al, unidi ec ional o bidi ec ional; he es ablishmen o
some in ade s may acili a e o p e en he in asions o o he o ganisms (Jackson 2015).
The e a e compa a i ely ew s udies o in e ac ions be ween in ade s, bu hei impo -
ance is inc easing as he bio a change (Sheppa d e al. 2018; A ismendi e al. 2020).
Some in asi e o ganisms a e now globally dis ibu ed. One such species is he
Eas e n mosqui o ish (Gambusia holb ooki Gi a d, 1859), which o igina es om
No h Ame ica (F ancis and Ha dwick 2012). This ish and a closely ela ed one
(G. a inis (Bai d & Gi a d, 1853)) we e long conside ed o be a single biological
species un il 1988 (Woo en e al. 1988). I is assumed ha hey ha e e y simila
biology and beha iou . Many con empo a y e iews combine he desc ip ion o
bo h species in o single pape s (Pyke 2005; Wal on e al. 2012). The main eason
o he human-media ed geog aphical sp ead o G. holb ooki, along wi h G. a inis,
is i s use o mosqui o con ol (Pyke 2005). This small-sized omni o ous ish has a
gene alis die which includes a wide ange o animal p ey: om cilia es and mic o-
c us aceans o small-sized aqua ic e eb a es (Pyke 2008). In asi e mosqui o ish
popula ions demons a e an undesi able impac on na i e ecosys ems (Hu lbe
e al. 1972; Hinchli e e al. 2017). Today, popula ions o G. holb ooki exis on
all con inen s excep An a c ica; i s in aded ange includes a leas 92 coun ies
(Reshe niko e al. 2018). This ish in ade anks i h among 551 non-na i e ish
species in e ms o he numbe o i e basins colonised on a global scale; he mos
in aded a eas a e Aus alia, whe e G. holb ooki anks 1s among o he ish in ade s,
and he Palea c ic, whe e i anks 4 h (Be ne y e al. 2022).
Simila o he ish species p esen ed abo e, he clawed og (Xenopus lae is
(Daudin, 1802)) is a global in ade (Measey e al. 2012). This anu an amphibian
belongs o he amily Pipidae and o igina es om Sou he n A ica. A e me a-
mo phosis, he adul clawed ogs emain in he wa e and exhibi an aqua ic li e-
s yle. I s la ae a e il a o s whe eas adul s consume di e se animal p ey including
compa a i ely la ge in e eb a es and e en e eb a es such as amphibians and ish
(Cou an e al. 2017). F om he 1930s o he 1960s, his amphibian was widely
used o es p egnancy (Elkan 1938) and g adually became ex emely popula o
a ious scien i ic labo a o y in es iga ions and as a pe . As a esul , X. lae is is ex-
po ed ou side i s na i e ange in Sou he n A ica (Weldon e al. 2007), b ed in
cap i i y and sold in pe shops wo ldwide (Gu don 1996). This amphibian species
has been in oduced in o many new coun ies ou side i s na i e dis ibu ion (Mea-
sey e al. 2012). In new a eas, his og in e ac s wi h na i e bio a, a ec ing local
species h ough compe i ion, p eda ion, and ansmission o in ec ious diseases
(Ama al and Rebelo 2012). The clawed og has been no ed as an asymp oma ic
agen in he sp ead o he pa hogen o he eme ging amphibian ungal disease
(Ba achochy ium dend oba idis) and ana i us (Fishe and Ga ne 2007; Reede
e al. 2012; Peña iel-Ricau e e al. 2023). To da e, X. lae is has been ound on all
con inen s excep Aus alia and An a c ica (Rödde e al. 2017).
175
NeoBio a 102: 173–189 (2025), DOI: 10.3897/neobio a.102.145644
And ey N. Reshe niko e al.: In e ac ions o wo global aqua ic in ade s
The clima ic niches o his og and he a o emen ioned mosqui o ish, used
o mosqui o con ol, o e lap as shown by species dis ibu ion models; egions
o ac ual sympa y o hese global in ade s ha e al eady been e ealed on all
he con inen s whe e he og has na u alised (Ihlow e al. 2016; Jou dan e al.
2021). Fu he mo e, he e is e idence ha bo h he clawed og and he mos-
qui o ish exhibi ed clima ic niche enla ging as hey colonise new a eas (Rödde
e al. 2017; Jou dan e al. 2021).
Th oughou i s as in aded ange, he mosqui o ish ine i ably encoun e s
o he aqua ic in ade s, esul ing in he es ablishmen o new ophic in e -
ac ions. Fo example, he in asi e mosqui o ish co-occu s and in e ac s wi h
he cane oad (Rhinella ma ina (Linnaeus, 1758)) in Aus alia, he Louisiana
c ay ish (P ocamba us cla kii (Gi a d, 1852)) in Eu ope, he og X. lae is in
Sou h Ame ica and o he con inen s (Komak and C ossland 2000; Anas ácio
e al. 2011; Lobos 2020). Expe imen al s udies ha e shown ha he mosqui-
o ish a oids eeding on he eggs and adpoles o he cane oad, bu he b ie
ha chling on ogene ic s age has been conside ed ulne able o ish p eda ion
(Komak and C ossland 2000). The mosqui o ish can consume newly ha ched
Louisiana c ay ish, bu is ea en by la ge adul c ay ish indi iduals (Anas ácio
e al. 2011). Thus, unidi ec ional and bidi ec ional p eda o y in e ac ions be-
ween mosqui o ish and o he in ade s a e possible. Howe e , many aspec s
o he alien-alien in e ac ions emain unknown. Fo example, i has been sug-
ges ed ha mosqui o ish in Chile may nega i ely a ec popula ions o he
in oduced clawed og bu de ailed analyses indica e ha he clawed og pop-
ula ion began o decline p io o he da e o documen ed mosqui o ish popu-
la ion g ow h (Lobos 2020). In addi ion, on ogene ic s ages o he clawed og
ha a e ulne able o mosqui o ish p eda ion and he po en ial consump ion
o he mosqui o ish by his in asi e amphibian emain unknown. Bo h he
mosqui o ish and he clawed og a e classic in ade s wi h ea ly sexual ma u-
i y, high ecundi y, and a b oad die . They a e ole an o a wide ange o en-
i onmen al condi ions, and eadily colonise hea ily modi ied an h opogenic
landscapes (Pyke 2008; F ancis and Ha dwick 2012). Bo h he clawed og
and he mosqui o ish ha e simila habi a equi emen s, p e e ing shallow,
well- ege a ed wa med a eas o aqua ic si es wi h s ill o slowly-mo ing wa e
(Pyke 2008; F ancis and Ha dwick 2012). Howe e , he possibili y o long-
e m coexis ence o popula ions o hese wo in ade s in he same wa e body
is ques ionable, as hey a e ac i e p eda o s wi h signi ican po en ial o impac
on syn opic hyd obion s (La e y and Page 1997; Hame 2022).
The aim o his s udy is o in es iga e he p eda o y in e ac ions be ween
wo globally in asi e species: he Eas e n mosqui o ish (Gambusia holb ooki)
and he A ican clawed og (Xenopus lae is). We hypo hesised ha di e en
on ogene ic s ages o he og a e ulne able o a ying deg ees o p eda ion by
mosqui o ish and ha mosqui o ish hemsel es can be p eyed upon by adul
ogs unde ce ain condi ions. To his end, we conduc ed a se ies o con olled
labo a o y expe imen s o assess he pala abili y, unde s ood as abili y o con-
sume, o X. lae is eggs, ha chlings, adpoles, and me amo phs o mosqui o ish.
In pa allel, we e alua ed he pala abili y o ju enile and adul G. holb ooki o
adul clawed ogs. Gi en ha X. lae is is a p edominan ly noc u nal p eda o ,
we also conduc ed addi ional ials unde low-ligh condi ions o explo e i s
p eda ion e iciency du ing he da k phase o he diel cycle.
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And ey N. Reshe niko e al.: In e ac ions o wo global aqua ic in ade s
Ma e ials and me hods
Animals and hei main enance
The Eas e n mosqui o ish, Gambusia holb ooki, we e collec ed on 13 Ap il 2022
wi h a deep-ne om a pond (43.4263N; 39.9731E) on he Black Sea coas o he
Caucasus in K asnoda K ai a sou h o he Russian Fede a ion. The collec ion o
G. holb ooki is no egula ed in Russia as his ish is ecognised as in asi e (Reshe -
niko e al. 2018). The sizes o he ish we e: a o al leng h (TL) o 33.7 ± 0.8
(25.0–41.0) mm and a body mass (m) o 0.33 ± 0.03 (0.11–0.63) g; N = 20 (mean
alues and hei s anda d e o s a e gi en h oughou he a icle). The ish we e
anspo ed o he labo a o y. P io o he expe imen , he ish we e kep in 45 L
aqua ia wi h densi y 1 ish indi idual pe li e . We used aged ap wa e wi h he
ollowing alues o hyd ochemical cha ac e is ics: oxida ion- educ ion po en ial
(ORP) 126.1 ± 1.4 mV; pH 7.14 ± 0.01; concen a ion o dissol ed oxygen (DO)
8.59 ± 0.04 mg/L (Aqua TROLL® 600, he USA); ammonium concen a ion o
< 1.0 NH3/NH4 mg/l (NILPA®, Russia). Wa e was changed pa ially e e y o he
day. Fo p elimina y acclima ion a e anspo a ion o he labo a o y, ish we e
kep in 45 L aqua ia a leas 10 days be o e he s a o expe imen al wo k.
We also used a i icially b ed clawed og X. lae is. P io o he expe imen , eggs
and ha chlings we e kep in aqua ia wi h aged ap wa e (hyd ochemical pa am-
e e s as p esen ed abo e) a wa e empe a u e o 4–5 °C. This low empe a u e
was used o delay he de elopmen o eggs and ha chlings in o de o ha e a ail-
able ma e ials o he expe imen by he igh da e. A e a pe iod o keeping a
low empe a u e, eggs and ha chlings emained ali e and undamaged, which was
con i med by us: some indi iduals did no pa icipa e in he expe imen s and la e
unde wen no mal de elopmen and eached sexual ma u i y. The me amo phs
we e kep in 45 L aqua ia illed o 35 L (10 indi iduals pe aqua ium) and ed wi h
Chi onomidae la ae ad libi um e e y o he day. Adul clawed ogs we e kep un-
de he same condi ions bu 14 indi iduals pe 45 L aqua ium wi h equen wa-
e changes. La ae, me amo phs, and adul s we e kep a a wa e empe a u e o
19–21 °C. Sizes (leng h and mass) o di e en on ogene ic s ages a e p esen ed in
he Table 1. All he measu emen s o leng h we e made wi h an accu acy o 1 mm.
The mass was measu ed wi h 2 mg accu acy wi h balances KERN® CM 50-C2N
(KERN & Sohn GmbH, Ge many), excep ing adul ogs, which we e measu ed
wi h balances VK-300.1 (Massa-K®, RF) wi h 100 mg accu acy. Amphibian sizes
we e de e mined o 15 indi iduals o each o he s ages s udied.
Expe imen al design
Each andomly chosen ish indi idual was placed in a sepa a e aqua ium
(N = 28), 39.5 × 28.7 × 24.5 cm, con aining 10 L o aged ap wa e (app . 9 cm
wa e column). Aqua ia wi h emales and males we e al e na ed: 2 aqua ia wi h
emales, 2 aqua ia wi h males, e c. The expe imen al ish we e isually isola ed
om each o he using whi e hea y (235 g/m2) pape di ide s be ween aqua ia.
The a i icial pho ope iod was 06:00–23:00. Illumina ion sou ces (LED lamps,
cold ligh 6500 K) we e placed 45 cm abo e he wa e and p oduced 623 ± 34 lx
on he wa e su ace. Unde hese condi ions, he ish began o ac i ely con-
sume he ood (la ae o Dip e a, Chi onomidae) wi hin he i s day a e being
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NeoBio a 102: 173–189 (2025), DOI: 10.3897/neobio a.102.145644
And ey N. Reshe niko e al.: In e ac ions o wo global aqua ic in ade s
Table 1. Size cha ac e is ics o di e en on ogene ic s udies o he clawed og Xenopus lae is, used
in he expe imen s: Mean Leng h ± S anda d E o (L, 1 mm), Leng h Range (minimum-maximum,
mm), Mean Weigh (W, 2 mg, 10 mg), Weigh Range (mm), and numbe o measu ed indi iduals (n).
S age Mean L, mm Range L, mm Mean W, Mg Range W, mg n
Egg 2.0 2–2 4 4–4 15
Emb yo 1.5 1.5–1.5 4 4–4 15
Ha chling 7.0 7–7 4 4–4 15
Ea ly adpole 7.9 ± 0.2 7–9 8 8–8 15
Me amo ph 15.8 ± 0.4 13–19 417 ± 32 220–760 15
Adul 36.7 ± 0.5 33–43 5000 ± 200 3500–8100 15
placed in he aqua ium. Ne e heless, he ish we e le o acclima ise o i e
days. Hyd ochemical pa ame e s on he second day o acclima ion (be o e pa -
ial wa e change) we e: ORP 113.6 ± 1.3 mV; pH 7.28 ± 0.04; DO 8.50 ± 0.04
mg/L (Aqua TROLL® 600, USA); < 1.0 NH3/NH4 mg/l (NILPA®, Russia). All
expe imen s we e ca ied ou in a he mos a ically con olled labo a o y oom
om Decembe 2022 o No embe 2023 a a wa e empe a u e o 19–21 °C.
This empe a u e is wi hin he empe a u e ange o ole ance and eeding ac i i-
y o bo h species s udied: mosqui o ish and clawed og (Cas e lin and Reynolds
1980; El-Bo ay 2014; Wilson e al. 2000; ou obse a ions). To s anda dise he
le el o ood mo i a ion, ish we e no ed o 24 h p io o he expe imen .
When a po en ial ood was added o he aqua ium, he ood was isually isola ed
om he ish by an opaque plas ic sc een (9.5 × 25.5 cm) o p e en he ish om
esponding o he expe imen e ’s hand mo emen s. The sc een was hen emo ed
om he aqua ium wi h a e ical upwa d mo ion.
i. Pala abili y o clawed og o mosqui o ish. In he i s expe imen , 28 mos-
qui o ish (14 emales and 14 males; one indi idual pe aqua ium) we e o e ed
eggs o he clawed og. All ish indi iduals we e assigned andomly o wo es
subg oups. Du ing he i s ound o he expe imen , one hal o he expe imen-
al ish ( i s subg oup: odd-numbe ed aqua ia) we e o e ed one amphibian egg
(2 mm; 4 mg). Remaining ish (second subg oup: e en-numbe ed aqua ia) we e
o e ed he con ol ood, wo indi iduals o Chi onomidae la ae (each wo m
was 10.5 ± 0.3 (8–14) mm, da a p esen ed om measu emen s o 20 speci-
mens). The mass o a pai o insec la ae indi iduals was 6.0 ± 0.0 (6.0–6.0)
mg. A e 2 h, he unea en ood o i s emains we e emo ed and he expe imen
was con inued a e ano he 1 h. In he second ound o he expe imen , ish o
he i s subg oup we e o e ed con ol ood whe eas ish o he second subg oup
we e o e ed amphibian egg. The nex day, ish in each g oup we e again o e ed
amphibians and con ol ood wice ( i s and second ound), bu in e e se o de .
Such design o he expe imen was applied in o de o exclude he po en ial e -
ec o he sequence o o e ing he main and con ol p ey species. Fo s a is ical
analysis we summed he da a ob ained o e wo days o an expe imen , ans-
o ming he esul s o each ce ain ype o p ey o a bina y sys em: consumed
/ no consumed. Du ing each ound, no adjacen aqua ia had he same ea -
men o minimise any bias ha migh ha e a isen om aqua ium posi ion. No
addi ional ood was o e ed o he ish a he end o he es in his expe imen .
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And ey N. Reshe niko e al.: In e ac ions o wo global aqua ic in ade s
In he same way o he same well-acclima ed g oup o ish indi iduals, we
o e ed emb yos, ha chlings, adpoles (s age 25 acco ding o Gosne 1960; s age
45 ollowing Nieuwkoop and Fabe 1994), and newly-me amo phosed ogle s
o he clawed og, each in a sepa a e expe imen wi h compa ison wi h con ol
ood. The sizes o he used og s ages a e p esen ed in Table 1. The sequence o
expe imen s did no co espond o he o de , om egg o ogle s, lis ed abo e.
In an expe imen wi h a pa icula p ey species/s age/condi ion, each indi idual
ish pa icipa ed once. Tes ing o indi idual adpoles in pala abili y ials is an
app op ia e app oach, because he e a e no di e ences in he su i al o clawed
og adpoles be ween indi idual s. g oup o e ing o G. holb ooki (Lobos 2020).
Beyond he main esul o his expe imen (assessmen o he pala abili y o di -
e en p ey ypes), we had he oppo uni y o compa e he consump ion o p ey
i ems in he i s and second ounds and con i med no signi ican di e ences in
p ey pala abili y be ween ounds (Suppl. ma e ial 1: ig. S1).
As pa o he abo e-desc ibed se ies o expe imen s, a sepa a e ial was used o
assess possible di e ences in he pala abili y o wo close bu p incipally di e en
s ages o he clawed og: ea ly emb yo (jelly capsule was emo ed mechanically by an
expe imen e ) and ha chling (a e lea ing he capsule on i s own). Fo his pu pose,
a di ec compa ison expe imen was conduc ed: emb yo s. ha chling. In his expe -
imen , 2 indi iduals o chi onomid la ae we e o e ed o he ish jus a e he ial
o moni o he p esence o ood mo i a ion. The p esence o ood mo i a ion was
assumed o be con i med i chi inomidae la ae we e consumed wi hou esidue.
As males o mosqui o ish a e no iceably smalle han emales, his could heo-
e ically a ec hei abili y o consume some ypes o p ey. The sizes o males we e:
TL = 30.1 + 0.6 (25–33) mm; m = 176 + 8 (110–215) mg (80.6 and 38.8% o
emale leng h and mass espec i ely). We used esul s o he abo e-desc ibed se ies
o he expe imen s o compa e consump ion o objec s by males and emales. Fo
s a is ical analysis, males and emales we e coded as 1 and 0 espec i ely.
ii. Pala abili y o mosqui o ish o adul clawed ogs. We also conduc ed ex-
pe imen s o assess he abili y o adul clawed ogs o ca ch and consume mos-
qui o ish. The sizes o he adul ogs a e p esen ed in Table 1. F ogs we e placed
andomly one pe aqua ium wi h 10 L o aged ap wa e . Hyd ochemical pa ame-
e s o wa e on he second day o acclima ion (be o e pa ial wa e change) we e:
ORP = 105.4 ± 1.6 mV; pH 7.28 ± 0.06; DO = 8.61 ± 0.03 mg/L (Aqua TROLL®
600, he USA); < 1.0 NH3/NH4 mg/l (NILPA®, Russia). The expe imen s we e
conduc ed a a wa e empe a u e o 19–21 °C acco ding o p o ocol o he main
expe imen desc ibed abo e, i.e. o e wo days wi h wo ounds pe day. As be o e,
chi onomid la ae we e used as con ol p ey. Fi s , we es ed pala abili y o adul
mosqui o ish o ogs (2 h o e ing o he po en ial p ey).
As consump ion o adul ish p ey was no e ealed in he i s expe imen , we
conduc ed an addi ional expe imen wi h p olonged o e ing du ing 6 h o es i
addi ional ime is impo an o p ey pala abili y.
To con i m he impo ance o ish de ensi e beha iou in escaping og
a acks and exclude e sion o possible as elessness, we conduc ed an addi-
ional expe imen in which adul ogs we e o e ed li e s. dead adul mosqui-
o ish du ing 2 h. A he end o he obse a ion pe iod (2 h) and a e emo al
o he emaining ish indi iduals om he aqua ia, he chi onomidae la ae
we e o e ed o he ogs o con i m hei ood mo i a ion.
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And ey N. Reshe niko e al.: In e ac ions o wo global aqua ic in ade s
We also es ed he assump ion ha ju enile small ish indi iduals migh be less
able o a oid p eda o s han la ge ish adul s. The sizes o he o e ed ju enile ish
we e: TL = 19 ± 0.6 (17–23) mm; m = 70 ± 10 (36–136) mg; N = 20. The ish
ju eniles we e o e ed in compa ison wi h con ol ood.
iii. Pala abili y o mosqui o ish o adul clawed ogs unde low-ligh condi-
ions. Conside ing ha he mosqui o ish a e diu nal and he adul clawed ogs
a e noc u nal, we ha e assumed ha a og p eda o could ha e an ad an age when
hun ing unde low-ligh condi ions. F ogs we e le o acclima e in aqua ia du ing
5 days. We conduc ed an app op ia e ial, o e ing adul mosqui o ish s. con ol
p ey du ing 2 h unde low-ligh condi ions (<0.01 lux). Resul s on p ey consump-
ion we e eco ded a he end o he o e ing pe iod (2 h).
To es he assump ion ha ogs will be mo e success ul p eda o s a e p olonged
low-ligh pe iod, we also applied modi ica ion o he expe imen in a sepa a e ial
wi h he 6 h ime o o e ing. Resul s we e eco ded a he end o 6 h o o e ing.
We also hypo hesised ha small-sized ju enile mosqui o ish indi iduals may
ha e been less p o ec ed (compa ing o adul ish) om og p eda ion unde low-
ligh condi ions. To es his hypo hesis, we conduc ed a sepa a e expe imen wi h
2 h o e ing ju enile ish s. con ol p ey unde low-ligh condi ions.
Da a analysis
Non-pa ame ic s a is ic c i e ia we e used. Coch an’s Q es ( o mul iple compa -
isons) and Sign Z es ( o pai wise compa isons) we e applied o assessmen o
compa a i e pala abili y. We used package s a s om base R (R Co e Team 2024)
o Spea man co ela ion es , package coin (Ho ho n e al. 2006) o Sign es
and Coch an’s Q es , package ggplo 2 (Wickham 2016) o plo s. The le el o
signi icance was accep ed as 0.05. We p esen unadjus ed p alues. All conclusions
in he Resul sec ion emain alid a e applying he Holm-Bon e oni co ec ion
o mul iple compa isons, excep whe e speci ically s a ed.
Resul s
Pala abili y o clawed og o mosqui o ish
In all cases, con ol p ey (Chi onomidae) was consumed immedia ely a e he
i s a ack, i.e., du ing he i s ew seconds a e he s a o he ial. Mosqui-
o ish eadily consumed clawed og eggs and ha chlings; he mean numbe o
hese p ey i ems consumed was 1.5 ± 0.1 (0–2) and 1.6 ± 0.1 (0–2) espec i ely.
The adpole was he mos pala able s age; he ish consumed all adpoles o e ed
(Fig. 1). Newly-me amo phosed ogle (me amo ph) was he leas consumed
s age: 0.11 ± 0.06 (0–1). The p ey i em signi ican ly in luenced he deg ee o
pala abili y (Q = 82.5; N = 28; d = 4; p < 0.001). When ans o med o a bi-
na y scale (consumed/no consumed – summa y o wo expe imen al ounds),
he pala abili y le el o he leas edible s age ( ogle ) was signi ican ly di e en
om he pala abili y o he egg (Z = -4.90; N = 28; p < 0.001). The di e ences
in pala abili y be ween newly-me amo phosed ogle s and o he s ages a e e en
g ea e (Fig. 1). Excep o ogle s, di e ences be ween o he s ages a e no sig-
ni ican (Z ≤ 1.5; NS). Fish consumed eggs, ha chlings, and adpoles as a whole.
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And ey N. Reshe niko e al.: In e ac ions o wo global aqua ic in ade s
Unlike o he s ages, ish did no consume whole newly-me amo phosed ogle s,
bu some ogle s we e a ally inju ed by he ish and died. The inju ed ogle s
we e pa ially ea en; hei mass was dec eased on 12–44 mg o 8% o body mass.
I is no ewo hy ha hese newly-me amo phosed ogle s did no a emp o
a ack he adul ish bu ied o escape om he ish p eda o . All ishes ha
consumed amphibians emained ali e wi h no signs o s ess.
Bo h emales and males o mosqui o ish eadily consumed eggs, ha chlings,
and adpoles o he clawed og (Suppl. ma e ial 1: ig. S2), bu emales ended
o consume a sligh ly g ea e numbe o og eggs compa ed o males (Spea -
man co ela ion es : ho = -0.44; N = 28; S = 5273.0; p = 0.02; P2c i = 0.017
ollowing Holm-Bon e oni co ec ion). In ou expe imen , a small numbe o
newly-me amo phosed ogle s we e inju ed (Suppl. ma e ial 1: ig. S2). Fish
males did no inju e his ype o p ey; all ogle s we e inju ed and pa ially
consumed by emales only (Suppl. ma e ial 1: ig. S2).
In a ial wi h di ec es ing o pala abili y o he clawed og emb yo com-
pa ing wi h he ha chling, ish consumed a high numbe o he o e ed emb yo
(Suppl. ma e ial 1: ig. S3). The le el o pala abili y was simila o ha o he
ha chling and did no di e signi ican ly (Z = -1.41; N = 28; p = 0.50).
Pala abili y o mosqui o ish o adul s o he clawed og
In he expe imen wi h one-yea -old adul ogs (as p eda o ) and adul mosqui-
o ish (o e ed), he ish did no demons a e any p eda o y beha iou . In con as
o he ish, each og pe o med mul iple bu unsuccess ul a emp s o ca ch he
o e ed ish. F ogs a acked po en ial p ey om a sho dis ance o 1–2 cm. Despi e
ob ious ood mo i a ion, no ogs caugh he adul ish du ing 2 h. We epea ed
his expe imen using a longe ime pe iod, 6 h o e ing, and ob ained an iden ical
Figu e 1. Pala abili y (means ± SE) o di e en on ogene ic s ages o he clawed og Xenopus lae is
o he mosqui o ish Gambusia holb ooki.
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And ey N. Reshe niko e al.: In e ac ions o wo global aqua ic in ade s
esul : he ogs ailed o ca ch he ish du ing he p olonged pe iod. The di e ence
in he obse ed pala abili y o he con ol p ey (Chi onomidae) and he adul mos-
qui o ish is signi ican (Z = 5.29; N = 28; p < 0.001).
In an addi ional expe imen , adul ogs we e o e ed li e s. dead adul mosqui-
o ish o a pe iod o 2 h. In his expe imen , ogs did no ea li e adul mosqui o-
ish bu consumed all he dead ish o e ed. The di e ence in pala abili y be ween
li e and dead ish is signi ican (Z = 5.29; N = 28; p < 0.001). The sizes o he
consumed ish we e TL = 33.9 ± 0.6 (27–44) mm, m = 404 ± 27 (142–890) mg,
N = 56. These ish we e 71–123% in leng h and 2–18% in mass o he app op i-
a e og p eda o . The ogs swallowed ish ei he om he head o ail end. Pa s
o la ge ish indi iduals we e seen s icking ou o he og’s mou h. All ogs ha
consumed ish emained ali e wi h no nega i e consequences.
In expe imen s wi h adul ogs and ju enile mosqui o ish, one ou o 20 ogs
consumed wo ish indi iduals and wo ogs consumed one ish each du ing wo
ounds. In all cases, he p ey was consumed whole. One og (L = 32 mm, m = 3.3 g)
consumed ish p ey ep esen ing 53% o i s leng h and 2.3% o i s mass o e wo
days and he o he wo ogs consumed ish indi iduals ep esen ing 58 and 62%
o og’s leng h and 1.6 and 2.2% o i s mass, espec i ely. The di e ence in pala -
abili y o es and con ol p ey is signi ican (Z = 4.12; N = 20; p < 0.001) (Fig. 2b).
Pala abili y o mosqui o ish o adul s o he clawed og unde low-
ligh condi ions
No adul mosqui o ish we e ea en by ogs du ing a 2-hou ial unde low-ligh
condi ions; he di e ence in consump ion o es and con ol p ey is signi ican :
Z = 5.29; N = 28; p < 0.001.
In ano he expe imen , du ing a longe ime pe iod (6 h) unde low-ligh con-
di ions, wo ou o 28 ogs had consumed mosqui o ish: one p ey ish pe am-
phibian indi idual (Fig. 2a). The di e ence be ween he consump ion o es and
con ol p ey is also signi ican : Z = 5.10; N = 28; p < 0.001. In his expe imen ,
he e we e equal numbe s o emales and males. Bo h he consumed ish indi idu-
als we e males. Thei sizes we e 29 mm, 252 mg and 28 mm, 238 mg. Thei leng h
was 72–83% and hei mass 4–5% o a og p eda o .
Con a y o he abo e-desc ibed esul s, he ogs e ec i ely caugh and con-
sumed ju enile mosqui o ish unde low-ligh condi ions: mos o he ish we e
elimina ed du ing 2 h pe iod (Fig. 2c). All adul ogs es ed consumed ju enile
ish (one o wo indi iduals pe og) as well as con ol p ey du ing he wo es
ounds, showing no di e ences in pala abili y be ween hese wo p ey i ems. All
he s udied p eda o y in e ac ions a e summa ised in he Table 2.
Discussion
In his way, we ha e demons a ed ecip ocal p eda ion o wo s udied aqua ic
in ade s o di e en sys ema ic a ilia ions. The esul s con i m di e ences in pal-
a abili y o a ious on ogene ic s ages o he clawed og o mosqui o ish, as well
as low pala abili y o adul s and high pala abili y o ju eniles o his ish o adul
s age o he og. Vulne abili y o ju enile ish o og p eda ion depends on il-
lumina ion condi ions. These ish-amphibian in e ac ions a e complex and hei
unde s anding equi es mo e de ailed analysis.
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And ey N. Reshe niko e al.: In e ac ions o wo global aqua ic in ade s
Lobos G (2020) Vulne abili y o Xenopus lae is o Gambusia holb ooki: Can he la al phase o he
A ican clawed og be he Achilles heel in i s in asi e po en ial? Aqua ic In asions 15: 529–541.
h ps://doi.o g/10.3391/ai.2020.15.3.11
Man ei el YB, Reshe niko AN (2002) A oidance o noxious adpole p ey by ish and in e eb a e
p eda o s: Adap i i y o a chemical de ence may depend on p eda o eeding habi s. A chi ü
Hyd obiologie 153: 657–668. h ps://doi.o g/10.1127/a chi -hyd obiol/153/2002/657
Measey GJ, Rödde D, G een SL, Kobayashi R, Lillo F, Lobos G, Rebelo R, Thi ion J-M (2012)
Ongoing in asions o he A ican clawed og, Xenopus lae is: A global e iew. Biological In asions
14: 2255–2270. h ps://doi.o g/10.1007/s10530-012-0227-8
Mo ei a FD, Ma ques R, Sousa M, Rebelo R (2017) B eeding in bo h lo ic and len ic habi a s
explains he in asi e po en ial o he A ican clawed og (Xenopus lae is) in Po ugal. Aqua ic
In asions 12: 565–574. h ps://doi.o g/10.3391/ai.2017.12.4.12
Nieuwkoop PD, Fabe J (1994) No mal able o Xenopus Lae is (Daudin). Ga land Publishing Inc,
New Yo k, 252 pp.
Peña iel-Ricau e A, P ice SJ, Leung WTM, Al a ado-Rybak M, Espinoza-Zamb ano A, Valdi ia
C, Aza C (2023) Is Xenopus lae is in oduc ion linked wi h Rana i us incu sion, pe sis ence and
sp ead in Chile? Pee J 11: e14497. h ps://doi.o g/10.7717/pee j.14497
Pepin P, Shea s TH (1995) In luence o body size and al e na e p ey abundance on he isk o p e-
da ion o ish la ae. Ma ine Ecology P og ess Se ies 128: 279–285. h ps://doi.o g/10.3354/
meps128279
Pyke GH (2005) A e iew o he biology o Gambusia a inis and G. holb ooki. Re iews in Fish
Biology and Fishe ies 15: 339–365. h ps://doi.o g/10.1007/s11160-006-6394-x
Pyke GH (2008) Plague minnow o mosqui o ish? A e iew o he biology and impac s o in o-
duced Gambusia species. Annual Re iew o Ecology, E olu ion, and Sys ema ics 39: 171–191.
h ps://doi.o g/10.1146/annu e .ecolsys.39.110707.173451
R Co e Team (2024) R: A language and en i onmen o s a is ical compu ing. Ve sion 4.4.0. R
Founda ion o S a is ical Compu ing. Vienna, Aus ia. h ps://www.R-p ojec .o g/
Reede NMM, Pessie AP, V edenbu g VT (2012) A ese oi species o he eme ging amphibian
pa hogen Ba achochy ium dend oba idis h i es in a landscape decima ed by disease. PLoS ONE
7: e33567. h ps://doi.o g/10.1371/jou nal.pone.0033567
Reshe niko AN (2008) Does o an Pe cco us glenii (Pe ci o mes: Odon obu idae) ea he
eggs o ish and amphibians? Jou nal o Ich hyology 48: 336–344. h ps://doi.o g/10.1134/
S0032945208040061
Reshe niko AN, Zib o a MG, Dgebuadze YY (2018) Gambusia holb ooki (Gi a d, 1859): The Mos
Dange ous In asi e Species o Russia (TOP-100). KMK, Moscow, 538–545.
Reynolds SJ (2009) Impac o he in oduced poeciliid Gambusia holb ooki on amphibians in sou h-
wes e n Aus alia. Copeia 2009: 296–302. h ps://doi.o g/10.1643/CH-08-101
Rödde D, Ihlow F, Cou an J, Secondi J, He el A, Rebelo R, Measey GJ, Lillo F, de Villie s FA, de
Bussche e C (2017) Global ealized niche di e gence in he A ican clawed og Xenopus lae is.
Ecology and E olu ion 7: 4044–4058. h ps://doi.o g/10.1002/ece3.3010
Sege O, Mangel M, Blaus ein L (2009) Dele e ious e ec s by mosqui o ish (Gambusia a inis) on
he endange ed i e salamande (Salamand a in aimmacula a). Animal Conse a ion 12: 29–37.
h ps://doi.o g/10.1111/j.1469-1795.2008.00217.x
Sheppa d CS, Ca boni M, Essl F, Seebens H, Di G ass Conso ium, Thuille W (2018) I akes one
o know one: Simila i y o esiden alien species inc eases es ablishmen success o new in ade s.
Di e si y & Dis ibu ions 24: 680–691. h ps://doi.o g/10.1111/ddi.12708
Wal on WE, Henke JA, Why AM (2012) Gambusia a inis (Bai d and Gi a d) and Gambusia
holb ooki Gi a d (Mosqui o ish): A Handbook o Global F eshwa e In asi e Species. Ea hscan,
London, 261–273.
189
NeoBio a 102: 173–189 (2025), DOI: 10.3897/neobio a.102.145644
And ey N. Reshe niko e al.: In e ac ions o wo global aqua ic in ade s
Weldon C, Villie s ALD, Du P eez LH (2007) Quan i ica ion o he ade in Xenopus lae is om
Sou h A ica, wi h implica ions o biodi e si y conse a ion. A ican Jou nal o He pe ology 56:
77–83. h ps://doi.o g/10.1080/21564574.2007.9635553
Wickham H (2016) Da a analysis. Sp inge , 189–201. h ps://doi.o g/10.1007/978-3-319-24277-4_9
Wilson RS, James RS, Johns on IA (2000) The mal acclima ion o locomo o pe o mance in ad-
poles and adul s o he aqua ic og Xenopus lae is. Jou nal o Compa a i e Physiology. B, Bio-
chemical, Sys emic, and En i onmen al Physiology 170: 117–124. h ps://doi.o g/10.1007/
s003600050266
Woo en MC, Sc ibne KT, Smi h MH (1988) Gene ic a iabili y and sys ema ics o Gambusia in he
sou heas e n Uni ed S a es. Copeia 1988: 283–289. h ps://doi.o g/10.2307/1445867
Supplemen a y ma e ial 1
Addi ional images
Au ho s: And ey N. Reshe niko , A ina O. Raldugina, Dmi iy V. G inchenko, A em A. Kido ,
Niki a G. Pla ono , And ey B. Pe o skiy
Da a ype: pd
Explana ion no e: ig. S1. Compa a i e consump ion (means ± SE) o di e en on ogene ic s ages
o he clawed og Xenopus lae is by Gambusia holb ooki (N = 28) in 1s and 2nd ounds o he ex-
pe imen . ig. S2. Compa a i e consump ion (means ± SE) o di e en on ogene ic s ages o he
clawed og Xenopus lae is by emales (N = 14) and males (N = 14) o he mosqui o ish Gambusia
holb ooki. ig. S3. Compa a i e consump ion (means ± SE) o emb yos and ha chlings (di ec
compa ison) o he clawed og Xenopus lae is o he mosqui o ish Gambusia holb ooki (N = 28).
Copy igh no ice: This da ase is made a ailable unde he Open Da abase License (h p://openda a-
commons.o g/licenses/odbl/1.0/). The Open Da abase License (ODbL) is a license ag eemen
in ended o allow use s o eely sha e, modi y, and use his Da ase while main aining his same
eedom o o he s, p o ided ha he o iginal sou ce and au ho (s) a e c edi ed.
Link: h ps://doi.o g/10.3897/neobio a.102.145644.suppl1
