37
Di e en ial elemen al accumula ion o he signal c ay ish
(Paci as acus leniusculus) along an in asion g adien
Diana Gonçal es1, Ronaldo Sousa1, Juliana Souza-Kasp zyk2, P zemyslaw Niedzielski2,
Amílca Teixei a3, Janeide de Assis Guilhe me Padilha1
1 CBMA – Cen e o Molecula and En i onmen al Biology/ARNET-Aqua ic Resea ch Ne wo k and IB-S, Ins i u e o Science and Inno a ion o Bio-Sus ainabili y,
Depa men o Biology, Uni e si y o Minho, 8 Campus Gual a , 4710-057 B aga, Po ugal
2 Depa men o Analy icalChemis y,Facul yo Chemis y,AdamMickiewiczUni e si y,Uniwe sy e uPoznańskiegoS ee 8,61-614Poznań,Poland
3 CIMO, LA SusTEC, Ins i u o Poli écnico de B agança, Campus de San a Apolónia, 5300-253 B agança, Po ugal
Co esponding au ho : Janeide de Assis Guilhe me Padilha ([email p o ec ed])
Copy igh : © Diana Gonçal es 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 non-na i e signal c ay ish (Paci as acus leniusculus) can in luence elemen al cycling in aqua ic eco-
sys ems h ough bioaccumula ion and ans e o chemical elemen s, wi h po en ial spa ial a ia ion
along in asion g adien s. In his s udy, we in es iga e he di e ences in elemen al exposu e in signal
c ay ish in he Rabaçal Ri e , Po ugal. We ocus on po en ial in a-popula ion di e ences along a
well-de ined in asion g adien , compa ing indi iduals om he in asion co e (ups eam) and he
downs eam expanding on (n = 30 each). We examined 57 elemen s in he muscle o he signal c ay-
ish, including essen ial elemen s (EEs): Mn, Co, Ni, Cu, Zn, Mg, Ca, Fe, Se, V, S; non-essen ial and
po en ially oxic elemen s (PTEs): Cd, Hg, Pb, U, As, S , Ba, C , Z , Cs, Tl; and echnology-c i ical
elemen s (TCEs): Ti, Rb, La, Ce, P , Gd, Dy, Ho, E , Yb, Ga, Ge, H , Ta, In, Re, Te, P . We explo ed
he ela ionship be ween elemen concen a ions and signal c ay ish ophic ecology, in e ed h ough
s able iso ope analysis (δ13C and δ15N), beha iou , and epibio ic associa e load – ac o s known o
shape in asion success h ough hei e ec s on esou ce acquisi ion, compe i ion, and physiological
s ess. Signi ican di e ences in elemen concen a ions we e ound be ween indi iduals om he co e
and on . Indi iduals om he on showed highe le els (mean µg/kg, d y weigh ) o Co: (476 s.
297), V: (390 s. 262), Mn: (2.6 × 104 s. 1.0 × 104), Hg: (2526 s.1658), and Ta: (21 s. 11). These
pa e ns sugges ha on indi iduals, wi h highe δ15N alues and mo e explo a o y beha iou , eed
a highe ophic le els (e.g., mac oin e eb a es), which may explain he ele a ed concen a ions o
biomagni ying elemen s such as Hg and Ta. On he o he hand, indi iduals om he co e had highe
le els o Pb: (361 s. 234), and S : (39772 s. 20018), likely due o a die based on basal esou ces,
as suppo ed by he s ong nega i e co ela ion be ween Pb and δ13C, indica ing eliance on ben hic
sou ces mo e p one o lead accumula ion. This s udy inc eases ou unde s anding o con aminan ac-
cumula ion along an in asion g adien , o e ing insigh s o managemen p ac ices – such as a ge ed
emo al o highly con amina ed indi iduals, imp o ed moni o ing o me al le els in in aded a eas,
and public awa eness campaigns – o minimise ecological impac s on highe ophic le els.
Key wo ds: Beha iou , die , eshwa e ecosys ems, in asion g adien , non-na i e species, pa asi ic
load, po en ially oxic elemen s, s able iso opes, echnology-c i ical elemen s
Academic edi o : Ped o Anas ácio
Recei ed:
31 Janua y 2025
Accep ed:
24 Ap il 2025
Published:
7 Oc obe 2025
Ci a ion: Gonçal es D, Sousa R, Souza-
Kasp zyk J, Niedzielski P, Teixei a A,
Padilha JdeAG (2025) Di e en ial
elemen al accumula ion o he signal
c ay ish (Paci as acus leniusculus)
along an in asion g adien . In:
Anas ácio P, Ribei o F, Chainho P
(Eds) In asions in Aqua ic Sys ems.
NeoBio a 102: 37–62. h ps://doi.
o g/10.3897/neobio a.102.148414
NeoBio a 102: 37–62 (2025)
DOI: 10.3897/neobio a.102.148414
Ad ancing esea ch on alien species and biological in asions
A pee - e iewed open-access jou nal
NeoBio a
38
NeoBio a 102: 37–62 (2025), DOI: 10.3897/neobio a.102.148414
Diana Gonçal es e al.: Elemen al accumula ion in signal c ay ish along an in asion g adien
In oduc ion
F eshwa e ecosys ems a e c ucial biodi e si y ho spo s, p o iding essen ial eco-
sys em se ices such as wa e pu i ica ion and nu ien cycling (Dudgeon 2019).
Despi e hei ecological signi icance, hese sys ems a e among he mos h ea ened
globally, acing biodi e si y declines a a a e su passing e es ial and ma ine eco-
sys ems (WWF 2024; Saye e al. 2025). Fo example, he abundance o moni-
o ed eshwa e e eb a e popula ions has dec eased by 85% since 1970 (WWF
2024), many imes d i en by he in oduc ion and es ablishmen o non-na i e
species, which can dis up ecological balances, modi y habi a s, and al e ophic
dynamics (Gu e i ch and Padilla 2004; Simbe lo 2010; Vö ösma y e al. 2010;
Gu ié ez e al. 2014; Dudgeon 2019; Li e al. 2023).
The signal c ay ish (Paci as acus leniusculus), na i e o No h Ame ica, is an ex-
ample o a highly in asi e species, as de ined by So o e al. (2024), gi en i s abili y
o es ablish sel -sus aining popula ions, sp ead apidly, and cause ecological, eco-
nomic, and social dis up ions in in aded ecosys ems. I s ecological plas ici y, apid
g ow h, ea ly ma u i y, and high ep oduc i e ou pu u he acili a e i s sp ead
(Capu o e al 2015; Vedia 2018). This species was i s de ec ed in Po ugal in
1997 in he Maçãs Ri e (Be na do e al. 2011), ha ing in aded adjacen i e
basins, such as he Rabaçal Ri e , in 2013 (Sousa e al. 2015, 2019; Ca alho e al.
2022). Beyond i s ecological impac s, he signal c ay ish may also accumula e mac-
oelemen s and ace elemen s in aqua ic ecosys ems (Nędza ek e al. 2020). This
accumula ion may be pa icula ly ele an because c ay ish can ac as bioindica o s
o en i onmen al con amina ion, e lec ing pollu ion le els in he sedimen s and
he wa e column (Nędza ek e al. 2020). Addi ionally, hei abili y o accumula e
bo h essen ial and non-essen ial elemen s aises conce ns abou po en ial ophic
ans e , whe e con aminan s may biomagni y along he ood chain, a ec ing na-
i e p eda o s such as ish, bi ds, and mammals, and posing isks o human con-
sume s (Nędza ek e al. 2020; Li e al. 2023). In his con ex , pollu ion is no only
an en i onmen al conce n bu also a compounding ac o ha can exace ba e he
ecological impac s o biological in asions (Li e al. 2023).
T ace elemen s play dual oles in ecosys ems, wi h essen ial elemen s (EEs)
such as Zn, Cu, and Fe being i al o physiological unc ions a low concen-
a ions bu also oxic a ele a ed le els (Islam e al. 2023). Non-essen ial and
po en ially oxic elemen s (PTEs), such as Pb, Cd, and As, pose addi ional isks
o o ganisms e en a low concen a ions (Saad e al. 2014; Zo oddu e al. 2019).
Technology-c i ical elemen s (TCEs) a e inc easingly gene a ing en i onmen al
conce n due o hei g owing use, especially in echnological indus y, and a e
conside ed eme ging con aminan s (Gwenzi e al. 2018; Bala am 2019). The
ele a ed accumula ion o hese compounds in na u e esul s in nega i e en i on-
men al impac s, especially o aqua ic o ganisms, which abso b and bioaccumu-
la e hem, comp omising he no mal unc ioning o o gans and ep oduc ion
(Picone e al. 2022; Espejo e al. 2023). These elemen s emain la gely unde -
s udied, so hei inc easing use makes hem an unce ain en i onmen al h ea
(Adeel e al. 2019; Malho a e al. 2020). The abili y o P. leniusculus o bioac-
cumula e hese elemen s, pa icula ly in he hepa opanc eas and exoskele on,
highligh s i s ole in bo h ecosys em and human heal h (Nędza ek e al. 2020).
This duali y unde sco es he need o moni o non-na i e species no only o
39
NeoBio a 102: 37–62 (2025), DOI: 10.3897/neobio a.102.148414
Diana Gonçal es e al.: Elemen al accumula ion in signal c ay ish along an in asion g adien
hei ecological impac bu also o human heal h since humans can consume
hem (Nędza ek e al. 2020; Dob zycka-K ahel e al. 2024).
In asion g adien s o e a unique oppo uni y o in es iga e how en i onmen al
p essu es shape he ai s o non-na i e species (Sousa e al. 2024). Theo e ically,
indi iduals a he in asion on ace dis inc selec i e p essu es, such as dis inc
exposu e o p eda o s, enhanced esou ce a ailabili y, and educed in aspeci ic
compe i ion, compa ed o hose in he in asion co e (Sousa e al. 2024; Al es e
al. 2025). These di e ences can d i e pheno ypic and beha iou al adap a ions,
such as heigh ened explo a o y beha iou , agg ession, and isk- aking, which may
enhance he success o indi iduals in colonising new habi a s (Phillips e al. 2010;
G ube e al. 2018; Yagound e al. 2022). Con e sely, indi iduals in he co e o en
expe ience highe in aspeci ic compe i ion, and po en ially mo e signi ican loads
o associa ed o ganisms, such as pa asi es which can in luence hei beha iou and
con aminan accumula ion pa e ns (Reb ina e al. 2015; He se e al. 2018; Sousa
e al. 2024).
Despi e ad ances in unde s anding he ecological impac s o non-na i e spe-
cies, in a-popula ion di e ences along in asion g adien s emain poo ly explo ed,
pa icula ly ega ding ace elemen accumula ion and i s in e ac ions wi h die ,
beha iou , and pa asi ism (Sousa e al. 2024). While p e ious s udies ha e ocused
on species-le el impac s (Nędza ek e al. 2020; Li e al. 2023), ew ha e del ed
in o popula ion-le el dynamics, which a e c i ical o elucida ing he mechanisms
unde lying in asion success and o be e unde s anding en i onmen al con ami-
na ion a meaning ul spa ial scales (Mo ales 2004). Few s udies analysed elemen s
such as a e ea hs, wi h he majo i y ocusing on s udying elemen s such as a se-
nic (As), me cu y (Hg), and lead (Pb) (Suá ez-Se ano e al. 2010; Bellan e e al.
2015; Gedik e al. 2017; Zhang e al. 2023). This gap is c i ical, as in a-popula-
ion a ia ion can e eal how local en i onmen al p essu es, die , beha iou , and
ecological in e ac ions shape con aminan bioaccumula ion and subsequen eco-
logical impac s (He se e al. 2018). Fo example, p e ious esea ch on in asi e ed
swamp c ay ish P ocamba us cla kii has demons a ed popula ion-le el di e ences
in ophic in e ac ions (Li e al. 2023). Howe e , hese s udies o en o e look be-
ha iou al ai s, such as isk- aking and agg ession, which may d i e di e en ial ex-
posu e o con aminan s along in asion g adien s. The e o e, unde s anding hese
accumula ion pa e ns and hei ecological in e ac ions is essen ial o de eloping
a ge ed s a egies o manage non-na i e species (Al es e al. 2025). By conside ing
popula ion-le el dynamics, including beha iou al ai s and ophic di e ences,
mi iga ion app oaches such as selec i e emo al p og ams and long- e m con ami-
nan moni o ing can be mo e e ec i ely designed o educe ecological and ophic
ans e isks (Sousa e al. 2024).
This s udy con ibu es o in es iga ing his gap by analysing elemen al bioac-
cumula ion, he in luence o die h ough s able iso ope analysis (δ15N and δ13C),
and assessing di e ences in beha iou and pa asi ic load in P. leniusculus along an
in asion g adien in he Rabaçal Ri e , Po ugal. We hypo hesize ha indi iduals
a he in asion on will exhibi highe explo a o y beha iou and isk- aking,
co ela ing wi h inc eased accumula ion o elemen s due o highe me abolic a es
associa ed wi h dispe sal and di e ences in o aging s a egies. Unde s anding
hese dynamics p o ides c i ical insigh s in o how in asi e species in e ac wi h
con aminan s, adap o ecological p essu es, and in luence ecosys em heal h.
40
NeoBio a 102: 37–62 (2025), DOI: 10.3897/neobio a.102.148414
Diana Gonçal es e al.: Elemen al accumula ion in signal c ay ish along an in asion g adien
Ma e ial and me hods
S udy a ea and sampling
This s udy was conduc ed on he Rabaçal Ri e (Fig. 1), loca ed in no heas e n
Po ugal, wi h a leng h o 88 km and i s sou ce in Spain (Sousa e al. 2018). The i -
e expe iences low an h opogenic p essu e, and pa o i lies wi hin he Mon esinho
Na u al Pa k, one o Po ugal’s p o ec ed a eas, es ablished in 1979 o p ese e he
ich biodi e si y ac oss an a ea o 748 km2 (Pe ei a e al. 2007; Cas o e al. 2010).
On he Rabaçal Ri e , eigh sampling si es (R1–R8) we e selec ed o delinea e he
in asion g adien o he signal c ay ish. R1, loca ed in Ed oso (41.92053, -7.1224),
ep esen s he in asion co e, while R7, in Candedo (41.86436, -7.11961), ma ks he
cu en in asion on . The selec ion o hese si es allowed us o de e mine he ex en
o he in asion and es ablish a e e ence amewo k. Howe e , we ocused on indi id-
uals om he in asion co e and on , as hey bes ep esen di e en in asion s ages.
All signal c ay ish indi iduals we e cap u ed using coa se-mesh ap ne s du ing he
summe o 2023 o elemen al, die , beha iou al, and epibio ic associa e analyses. The
aps we e subme ged o 24-hou pe iods and subsequen ly emo ed om he i e .
All indi iduals we e measu ed (ca apace leng h in cm), and hei sex was eco ded.
En i onmen al cha ac e isa ion
A each sampling si e, we measu ed key abio ic pa ame e s – empe a u e, conduc-
i i y, dissol ed oxygen, and pH – using a YSI EXO 2 mul i-pa ame e p obe. To
assess suspended ma e , 1 L o wa e was il e ed h ough GFC il e s. Fil e s we e
d ied a 60 °C o 48 hou s and hen combus ed a 550 °C o 8 hou s in a mu le
Figu e 1. Co e and on sampled si es along he Rabaçal Ri e . The co e si e is wi hin Mon esinho Na u al Pa k.
41
NeoBio a 102: 37–62 (2025), DOI: 10.3897/neobio a.102.148414
Diana Gonçal es e al.: Elemen al accumula ion in signal c ay ish along an in asion g adien
u nace, allowing us o calcula e o al (TSS) and o ganic suspended solids (OSS)
based on mass di e ences, ollowing Zie i z e al. (2018). These p ocedu es we e
conduc ed nea he mids eam i e bed, du ing la e mo ning pe iods.
To cha ac e ise sedimen , samples we e collec ed wi h a 10 cm-diame e co e
sample placed abou 2 m om he i e ’s le ma gin. G anulome y and o ganic
ma e we e analysed using he me hod desc ibed by Sousa e al. (2007). In addi-
ion, bo h si es we e su eyed using he Ri e Habi a Su ey (RHS) p o ocol o
assess habi a complexi y, ipa ian ege a ion s uc u e, aqua ic plan ypes, and
human-induced al e a ions along he i e channel. Su eys we e conduc ed along
500-me e eaches in he co e and on sampling si es and collec ed in o ma ion
was used o calcula e he Habi a Modi ica ion Sco e (HMS) and Habi a Quali y
Assessmen (HQA) indices (Ra en e al. 1998), p o iding a compa a i e assess-
men o an h opogenic in luence a he sampling si es.
T ace elemen analysis
The ace elemen s a e di ided in o essen ial elemen s (EEs), po en ially oxic
elemen s (PTEs), and echnology-c i ical elemen s (TCEs) (Gwenzi e al. 2018;
Bala am 2019; Zo oddu e al. 2019). Sample p epa a ion began wi h he eezing
sac i ice o 15 males and 15 emales andomly collec ed om each si e (co e s.
on o in asion). Specimens we e s o ed a -20 °C un il analysis a IB-S (Ins i-
u e o Science and Inno a ion o Bio-Sus ainabili y, B aga, Po ugal). The o al
leng hs o he indi iduals, measu ed om he os um o he elson ( ollowing
Sousa e al. 2013), om he co e, anged om 6.5 cm o 10.5 cm, while hose
om he on anged om 7.0 cm o 11.8 cm. Muscle samples we e d ied a 40°C
o 24 hou s in an In o s HT, Mul i on P o, g ound in a mo a o achie e a ho-
mogeneous powde consis ency, and subsequen ly sen o he Depa men o Ana-
ly ical Chemis y in Poznań, Poland. App oxima ely 0.80 ± 0.02 g o each sample
was diges ed wi h 3 mL 65% HNO3 using a mic owa e o en (Ma s 6, CEM
Co po a ion, Aus ia). The samples we e hen made up o 10 mL wi h Milli-Q
wa e (Di ec -Q sys em, Millipo e, Ge many). Immedia ely be o e he elemen al
analysis, he samples we e dilu ed 20 imes wi h HNO3 1%. A o al o 57 elemen s
– including EEs: Mn, Co, Ni, Cu, Zn, Mg, Ca, Fe, Se, V, S, Al, Na, P, K, B, Si,
PTEs: Cd, Hg, Pb, U, As, S , Ba, C , Z , Cs, Tl, Be, Nb, Ru, Pd, W, Os, Au and
TCEs: Ti, Rb, La, Ce, P , Gd, Dy, Ho, E , Yb, Ga, Ge, H , Ta, In, Re, Te, P , Nd,
Sm, Eu, Lu – we e analysed using induc i ely coupled plasma mass spec ome y
(ICP MS, PlasmaQuan ® MS, Analy ik Jena, Ge many).
Fo quali y con ol, analy ical blanks (n = 4) and ce i ied e e ence ma e ials
– DORM 5: ( ish p o ein; n = 3; Na ional Resea ch Council, Canada) and BCR
668 (mussel issue; n = 4; Ins i u e o Re e ence Ma e ials and Measu emen s,
Belgium) we e submi ed o he same p ocedu es as he samples. De ec ion limi s
anged om 0.00017 µg/kg o In o 1203 µg/kg o S (Suppl. ma e ial 1: able
S2). The eco e y a es o ce i ied ma e ials we e acco ding o in e na ional QA/
QC c i e ia being be ween 80 and 120%. Fo non-ce i ied elemen s, accu acy was
moni o ed using a s anda d solu ion. To ensu e op imal p ecision and accu acy in
he analyses, a solu ion con aining – Bi, I , Li, Rh, Sc, and Y – was used as in e nal
s anda ds. Fo mul i-elemen de e mina ion, he ollowing condi ions we e s an-
da dised: nebulise gas low a 1.02 L/min, auxilia y gas low a 1.5 L/min, plasma
gas low a 9.0 L/min, and Radio F equency (RF) powe se o 1.20 kW. Signal
42
NeoBio a 102: 37–62 (2025), DOI: 10.3897/neobio a.102.148414
Diana Gonçal es e al.: Elemen al accumula ion in signal c ay ish along an in asion g adien
measu emen s we e conduc ed o e 20 scans in 5 eplica es, using h ee sequen-
ial modes: wi hou gas addi ion, and wi h he in eg a ed Collision Reac ion Cell
(iCRC), u ilising hyd ogen as he eac ion gas and helium as he collision gas o
minimise mass in e e ence.
S able iso ope analysis o c ay ish
S able iso ope analysis was pe o med on he abdominal issue o he same c ay ish
indi iduals used o ace elemen analysis, o assess hei ophic posi ion and
po en ial die a y sou ces. The sample p epa a ion p ocedu e was he same as o
analysing ace elemen s. The elemen al and iso opic composi ion analyses we e
ca ied ou on a The mo Scien i ic Flash 2000 o ganic elemen al analyse (EA),
O ganic Elemen al Analyse , connec ed o an iso ope a io mass spec ome e
(IRMS) Del a V Ad an age ia Con lo IV, a Ciima (Cen o In e disciplina de
In es igação Ma inha e Ambien al) in Po o, Po ugal. S able ca bon and ni ogen
iso ope alues we e calcula ed using he ollowing o mula:
δX = (Rsample/Rs anda d - 1) × 1000,
whe e X is he iso ope o ca bon o ni ogen, and R is he a io be ween he hea y
and ligh iso opes o ca bon o ni ogen.
The δ15N and δ13C alues o he samples and s anda ds we e no malised wi h
e e ence ma e ials o each elemen (IAEA-N-1, IAEA-N-2 and IAEA-NO3 o
ni ogen, In e na ional A omic Ene gy Agency, Aus ia; USGS-24 and USGS-40
o ca bon, Uni ed S a es Geological Su ey, USA) wi h a ma gin o analy ical
e o o app oxima ely 0.1‰. Using an in e nal s anda d om he sea bass Dicen-
a chus lab ax ( ead a e 12 analyses o ha e analy ical con ol), he iso opic com-
posi ion o he samples p esen in he ex ac ed abdominal issue was accu a ely
de e mined. Co ec ions we e also made o he δ15N and δ13C alues acco ding o
a calib a ion cu e de i ed om he del a alues o N and C, based on he mass
ampli udes o a ca eine s anda d. The elemen al composi ion was also de e mined
using he Chlo ella K ac o , and he samples we e analysed wice o keep he co-
e icien o a ia ion below 10%.
Beha iou al es s
Th ee beha iou al es s we e conduc ed using indi iduals collec ed om bo h he
co e and on sampling si es o he in asion g adien . Be o e es ing, c ay ish un-
de wen an acclima ion pe iod o h ee days in a enas main ained a 18 °C, wi h-
ou ood. Fo he beha iou al es s, he indi iduals we e placed in a 60-li e a ena
(46 × 63 × 32 cm) made o polye hylene a a con olled labo a o y oom o 18 °C.
We pe o med he Risk- aking and Neophilia Tes s. Neophilia, o no el y-seek-
ing beha iou , is he endency o indi iduals o explo e and in e ac wi h no el ob-
jec s o en i onmen s, which may in luence hei isk- aking beha iou and adap -
abili y in new habi a s. In wo es s, 16 indi iduals (8 emales and 8 males, anging
om 8 o 11 cm in o al leng h) we e andomly selec ed om bo h he co e and
he on o he in asion g adien . These indi iduals we e placed inside a shel e
(17 × 20 × 16cm, polye hene, ec angula shape) wi hin he main expe imen al
43
NeoBio a 102: 37–62 (2025), DOI: 10.3897/neobio a.102.148414
Diana Gonçal es e al.: Elemen al accumula ion in signal c ay ish along an in asion g adien
a ena and gi en 5 minu es o acclima isa ion be o e es ing ( ollowing B own e
al. 2007; Suppl. ma e ial 1: ig. S1) o 15 minu es. The objec i es we e o assess
he indi iduals’ isk- aking abili y (measu ing he ime, in seconds, o lea e he
shel e ) and neophilia (measu ing he ime, in seconds, o lea e he shel e , ap-
p oach he objec , and ouch i ). Fo he neophilia es , a ish bai shaped like an
adul bee le was used as a isual s imulus wi hou any associa ed odou . The objec
was placed in mo ion o encou age in e ac ion.
Agg ession es s we e conduc ed o assess dominance in e ac ions in signal c ay-
ish. Fou comba g oups we e es ablished: (1) co e emale s. on emale, (2)
co e male s. on male, (3) co e emale s. on male, and (4) co e male s. on
emale. Each comba g oup was eplica ed eigh imes (n = 8 pe comba g oup),
o alling 32 igh s, wi h each indi idual pa icipa ing in only one igh o a oid
epea ed exposu e e ec s. In each ial, wo indi iduals o simila size (ca apace
leng h wi hin ± 0.5 cm, Suppl. ma e ial 1: able S3) and wi hou isible mo pho-
logical abno mali ies (e.g., missing o egene a ing chelae o walking legs) we e
andomly selec ed. A s a is ical e alua ion (ANOVA, p > 0.05) con i med ha size
di e ences be ween g oups we e no signi ican . The agg ession es s we e conduc -
ed in he same 60 L expe imen al a ena (46 × 63 × 32 cm) p e iously used o he
isk- aking and neophilia es s.
Fo he agg ession ials, wo indi iduals we e placed on opposi e sides o he
expe imen al a ena wi hou any addi ional acclima iza ion pe iod inside he es
a ena. These indi iduals we e dis inc om hose used in he isk- aking and neo-
philia es s o p e en po en ial ca yo e e ec s om p e ious ials. Addi ionally,
only indi iduals wi hou isible ec obion s (e.g., B anchiobdella as aci) we e selec -
ed o elimina e po en ial con ounding e ec s o pa asi e load on agg ession.
Two ypes o esou ces we e con es ed: ood (i.e., a s anda d piece o ca ood,
posi ioned cen ally be ween he wo indi iduals) and e i o y (i.e., a de ined space
wi hin he a ena). Each ial las ed 15 minu es, du ing which we eco ded agg essi e
in e ac ions ela ed o ood and space compe i ion. The la ency o he i s a ack, he
numbe o agg essi e in e ac ions (including an ennal con ac , chelae displays, and
s ikes), and he o e all igh du a ion we e all eco ded. Vic o y was de e mined by
wo c i e ia: (1) he indi idual who main ained exclusi e con ol o he ood o a
leas 30 seconds wi hou being displaced, and (2) he indi idual who con olled he
designa ed space a he end o he 15 minu es. I no clea dominance was es ablished
wi hin he obse a ion window, he con es was conside ed un esol ed.
P io o all hese es s, signal c ay ish unde wen a h ee-day acclima isa ion
pe iod in indi idual con aine s illed wi h ae a ed wa e and main ained a 18 °C.
This pe iod aimed o educe p io social hie a chies and s anda dise hunge le els,
as ecommended by p e ious s udies on c ay ish agg ession (B ei haup and Ege
2002; Aquiloni and Ghe a di 2010).
Epibio ic associa e analysis
The abundance o ex e nal epibio ic associa e (B anchiobdella as aci) was analysed
in si u in he co e and on sampling si es based on isual assessmen . The indi id-
uals we e assessed o an epibio ic associa e in he claws and classi ied on a 4- alue
quali a i e scale (0- absence; 1- ew; 2- some; 3- many). Rep esen a i e images o
each in es a ion ca ego y a e p o ided in Suppl. ma e ial 1: ig. S1.
44
NeoBio a 102: 37–62 (2025), DOI: 10.3897/neobio a.102.148414
Diana Gonçal es e al.: Elemen al accumula ion in signal c ay ish along an in asion g adien
Da a analysis
All da a analysis was ca ied ou in he R S udio so wa e (R Co e Team 2022),
using a ious packages such as “ eadxl” (Wickham and B yan 2023), “ggplo 2”
(Wickham 2016), “de ools” (Wickham e al. 2022), “dply ” (Wickham e al.
2023), “ jags” (Plumme 2024), “SIBER” (Jackson and Pa nell 2023), and “mul -
comp” (Ho ho n e al. 2008). The esul s o he 57 ace elemen s we e il e ed
o selec he elemen s ha could be analysed, emo ing hose wi h alue below
de ec ion limi s. A o al o 49 elemen s we e analysed, and he mean and s anda d
de ia ion we e calcula ed o each g oup (co e emale, co e male, on emale, and
on male). The s a is ical analysis consis ed o a wo-way ANOVA, o check o
possible di e ences be ween he ou g oups (co e emale, co e male, on emale,
and on male) and a Tukey es . Boxplo s we e made o all he elemen s whose
esul s we e signi ican in bo h analyses. A Pea son co ela ion analysis was con-
duc ed be ween he concen a ions o 49 ace elemen s and indi idual weigh o
e alua e po en ial ela ionships.
Fo he Pea son co ela ion analysis be ween indi idual weigh and elemen
concen a ions, da a om bo h sexes and in asion loca ions (co e and on ) we e
combined o inc ease s a is ical powe and p o ide a comp ehensi e assessmen
o elemen al accumula ion ends. A Pea son co ela ion was also made be ween
he 49 ace elemen s analysed and he s able iso opes δ15N and δ13C o iden i y
he possible in luence o die on he concen a ion o he ace elemen s analysed.
We conside a weak ela ionship when he co ela ion is up o 0.3, mode a e om
0.3–0.7 and s ong om 0.7–1 ( ollowing Schobe e al. 2018).
Fo he beha iou al es s, he Shapi o-Wilk es indica ed ha he da a did no
ollow a no mal dis ibu ion; he e o e, hey we e log10- ans o med o imp o e
no mali y be o e s a is ical analyses o he isk- aking and neophilia es s. Fo hese
es s, ANOVAs we e used o de e mine he signi icance o he in asion si e and sex.
Fo he agg essi eness es , chi-squa ed es s we e pe o med o assess whe he in-
di iduals a he on we e mo e agg essi e and o e alua e di e ences in beha iou
be ween sexes. This es is app op ia e o ca ego ical da a iden i ying which in-
di idual eached he ood i s o claimed he space. Fishe ’s exac es s we e also
conduc ed due o he small sample size.
To analyze epibio ic associa e da a, a chi-squa e es was ca ied ou o e alua e
he in luence o loca ion and sex on pa asi ism. Pai wise compa isons we e also
explo ed o assess di e ences be ween g oups.
Resul s
En i onmen al cha ac e isa ion
The sampled si es, loca ed 15 km apa , exhibi highly simila en i onmen al
condi ions (Suppl. ma e ial 1: able S1). The s udied i e expe iences minimal
human dis u bance, and he RHS su ey esul s a e nea ly iden ical o bo h sam-
pling si es (Suppl. ma e ial 1: able S1). The e o e, we conside ha he obse ed
a ia ions be ween co e and on sampling si es a e unlikely o be d i en by
en i onmen al di e ences.
45
NeoBio a 102: 37–62 (2025), DOI: 10.3897/neobio a.102.148414
Diana Gonçal es e al.: Elemen al accumula ion in signal c ay ish along an in asion g adien
Table 1. Mean alues ± s anda d de ia ion ob ained o he ace elemen s unde s udy (µg/kg, d y weigh ) and s able iso opes o he
signal c ay ish (Paci as acus leniusculus).
Local F on Co e
Sex Female Male Female Male
n14 17 13 15
Al 104902 ± 73604 129438 ± 55905 51298 ± 69884 42411 ± 28330
V401 ± 298 380 ± 166 268 ± 163 256 ± 102
Mn 17893 ± 11502 35156 ± 44898 7238 ± 5150 13911 ± 12406
Co 489 ± 459 463 ± 373 293 ± 162 301 ± 157
Ni 453 ± 571 397 ± 466 397 ± 300 1162 ± 1989
Cu 78762 ± 65501 63478 ± 28898 64864 ± 28095 81726 ± 43015
Zn 108026 ± 74333 89012 ± 39519 76690 ± 16325 110156 ± 80689
Cd 211 ± 163 171 ± 100 150 ± 72 192 ±129
La 53 ± 108 50 ± 62 28 ± 29 153 ± 273
Ce 115 ± 200 125 ± 122 75 ± 59 123 ± 248
P 16 ± 26 13 ± 15 8.62 ± 8.49 14 ± 36
Nd 62 ± 95 63 ± 58 41 ± 25 68 ± 128
Sm 22 ± 22 26 ± 17 19 ± 8.06 28 ± 24
Eu 1.8 ± 1.3 2.35 ± 2.49 2.75 ± 3.29 2.61 ± 1.66
Gd 11 ± 13 15 ± 11 10 ± 5.02 14 ± 12
Dy 7 ± 6.92 9.32 ± 7.53 7.56 ± 3.82 8.10 ± 3.19
Ho 3.33 ± 3.67 4.16 ± 3.35 2.80 ± 2.56 3.53 ± 3. 86
E 3.67 ± 3.74 5.43 ± 4.27 4.49 ± 3.25 4.38 ± 1.77
Hg 2858 ± 1956 2195 ± 918 1647 ± 942 1670 ± 964
Na 13173834 ± 9124346 9809414 ± 4025267 10650455 ± 4306602 10689730 ± 6460304
Mg 1815545 ± 1243487 1289553 ± 496082 1750486 ±534711 1761397 ± 694511
P13367983 ± 9453734 11581499 ± 5068599 7737853 ± 1327441 9614962 ± 4709918
K22432189 ± 1653791 18189038 ± 8103566 1430104 ± 3945718 20983848 ± 18855258
Ca 6942514 ± 5696204 3432673 ± 1734778 6934692 ± 3239298 11854283 ± 7933547
Fe 157276 ± 106304 156705 ± 88189 153796 ± 172209 133133 ± 52397
B29865 ± 26558 31606 ± 11562 14768 ± 10544 38502 ± 13350
Rb 58228 ± 42622 41813 ± 17649 43008 ± 17426 81837 ± 119259
S 26046 ± 20521 13990 ± 6519 33194 ± 13393 46351 ± 27108
Ba 3839 ± 3028 3087 ± 1842 4948 ± 2480 7320 ± 4001
Pb 411 ± 612 58 ± 52 547 ± 593 176 ± 56
U25 ± 33 16 ± 11 15 ± 11 15 ± 10
C 902 ± 908 814 ± 695 437 ± 201 795 ± 744
As 1190 ± 1174 773 ± 325 1202 ± 1112 814 ± 538
Se 907 ± 638 686 ± 289 670 ± 244 542 ± 436
S15811652 ± 10396139 12121667 ± 4554600 12197292 ± 2917404 12678303 ± 5839739
Ti 4893 ± 6529 3635 ± 3917 2134 ± 2553 2084 ± 1308
Ga 158 ± 130 138 ± 78 219 ± 111 311 ± 171
Ge 44 ± 40 58 ± 32 46 ± 17 62 ± 25
Yb 5.33 ± 5.51 7.11 ± 5.19 6.04 ± 3.39 6.75 ± 3.22
H 9.16 ± 7.61 9.35 ± 4.70 6.74 ± 2.05 29 ± 68
Ta 25 ± 22 16 ± 7.24 9.55 ± 2.98 13 ± 4.18
Be 10 ± 7.99 14 ± 7.17 14 ± 11 18 ± 8.25
Z 73 ± 68 49 ± 33 26 ± 10 550 ± 1811
Te 32 ± 22 34 ± 11 29 ± 5.87 51 ± 29
Cs 2361 ± 1586 1852 ± 684 2148 ± 877 3592 ± 4983
W27 ± 24 22 ± 17 8.25 ± 6.79 62 ± 90
P 10 ± 7.94 7.37 ± 2.71 1.42 ± 1.01 4.55 ± 1.79
Tl 34 ± 26 26 ± 12 24 ± 10 30 ± 29
Si 91945 ± 56399 97099 ± 67142 71535 ± 54459 72719 ± 50208
δ15N8.58 ± 0.55 8.56 ± 0.38 8.09 ± 0.32 8.31 ± 0.39
δ13C-23 ± 066 -23 ± 066 -23 ± 0.67 -23 ± 0.55
52
NeoBio a 102: 37–62 (2025), DOI: 10.3897/neobio a.102.148414
Diana Gonçal es e al.: Elemen al accumula ion in signal c ay ish along an in asion g adien
discussion below). Some elemen s, such as TCEs g oup, pose a h ea due o hei
high oxici y, long en i onmen al pe sis ence, and po en ial o bioaccumula ion
and biomagni ica ion in he ood chain (Mis i e al. 2020). TCEs, including
an alum and pla inum, showed highe concen a ions in indi iduals om he
in asion on . These elemen s a e inc easingly used in ad anced echnological ap-
plica ions, such as elec onics, sola panels, and medical de ices, aising conce ns
abou hei po en ial nega i e ecological impac s (Gwenzi e al. 2018; Bala am
2019). Tan alum, o example, may be linked o biomagni ica ion p ocesses, as
his elemen has been epo ed o accumula e in aqua ic ood webs (Espejo e al.
2018). Pla inum, commonly associa ed wi h ca aly ic con e e s and indus ial
emissions, sugges s possible con amina ion om a mosphe ic deposi ion o local
uno sou ces (Picone e al. 2022). The obse ed pa e ns ein o ce he idea ha
non-na i e species can se e as bioindica o s o eme ging con aminan s, highligh -
ing he need o u he esea ch on he ecological and oxicological implica ions
o TCE accumula ion in eshwa e ecosys ems.
When compa ed wi h o he s udies (Suppl. ma e ial 1: able S4), he concen a-
ions o lead, me cu y, and a senic appea o all wi hin alues ound in he li e a-
u e, while he concen a ion o coppe is highe han ha ob ained in o he s udies
wi h c ay ish. The concen a ion o cadmium is simila o ha ob ained in he s udy
by Rowe e al. (2001) bu highe han he alues ob ained in he o he s udies.
The e appea o be some sex- ela ed di e ences in some o he elemen s s udied,
such as B and S . Fo example, in he s udy by Nędza ek (2020), o he elemen s
Se, Ni, Cd, and Pb he e we e signi ican di e ences in he concen a ions p esen
in emales and males. A possible explana ion is ha egg-laying in emale c ay ish
could se e as a means o exc e ing ce ain elemen s, leading o di e en accumula-
ion pa e ns compa ed o males (Güne 2010). Howe e , his emains specula i e,
and only u he s udies can shed some ligh on his opic.
A posi i e co ela ion o he elemen s wi h δ15N indica es ha he e is an inc ease
in he concen a ions o he elemen wi h inc easing posi ion in he ophic chain,
which may sugges biomagni ica ion p ocesses, as highe ophic le els accumula e
mo e o hese elemen s h ough die a y exposu e (Dung e al. 2023). Con e sely, a
nega i e co ela ion indica es a highe concen a ion o he elemen as i mo es down
he ophic chain, which could be indica i e o biodilu ion, whe e lowe ophic le -
els accumula e mo e o he elemen om he en i onmen (Dung e al. 2023). The
esul s showed a s ong posi i e co ela ion wi h he elemen s Si, Z , Ta, Ti, H , Ge,
S , Fe, Nd, P , Ce, La, Dy, Gd, Sm, Cd and Al, which means ha along he ophic
chain, species ha a e highe up he chain, such as in he case o he Eu asian o e
o b own ou may be mo e exposed o a highe concen a ion han species lowe
down he ood chain (Esposi o e al. 2020). On he o he hand, species a he op o
he chain will accumula e a lowe concen a ion o S , as his elemen was nega i ely
co ela ed. In his case, he p ocess o biodilu ion occu s (Dung e al. 2023).
Possible mechanisms explaining di e en elemen al accumula ion
along he in asion g adien
The signal c ay ish’s omni o ous die e lec s high die a y plas ici y, enabling hem
o consume a wide a ie y o ood sou ces such as ish, in e eb a es, aqua ic plan s,
and de i us (Olsson e al. 2009; Jackson and B i on 2014). Food a ailabili y
in luences hei ophic posi ion, and as Al es e al. (2025) obse ed using he
53
NeoBio a 102: 37–62 (2025), DOI: 10.3897/neobio a.102.148414
Diana Gonçal es e al.: Elemen al accumula ion in signal c ay ish along an in asion g adien
SIBER model, indi iduals a he in asion on in he Rabaçal Ri e occupy a di -
e en ophic niche, bene i ing om he highe a ailabili y o highe ophic-le -
el p ey, such as mac oin e eb a es, compa ed o co e indi iduals who ely mo e
on plan s due o inc eased compe i ion and esou ce deple ion gi en hei highe
abundance in his si e (Galib e al. 2022). I is known ha indi iduals eeding on
esou ces a he bo om o he wa e column (e.g. algae, o ganic ma e such as
lea li e ) may ha e highe C13 alues when compa ed o indi iduals eeding on
o ganisms in he wa e column (e.g. mac oin e eb a es and ish) (Pacioglu e al.
2019). These esul s co obo a e ou indings, indica ing ha indi iduals in he
co e ely mo e on ben hic ood sou ces compa ed o hose in he on . P e ious
s udies ha e demons a ed ha ophic niche di e en ia ion occu s be ween co e
and on popula ions, wi h on indi iduals exhibi ing a die iche in highe
ophic-le el p ey, such as mac oin e eb a es, while co e indi iduals ely mo e on
plan de i us and basal esou ces due o highe compe i ion and abundance in he
co e (Pacioglu e al. 2019). These die a y di e ences may con ibu e o a ia ions
in elemen accumula ion be ween g oups.
Many o ganisms apidly adap hei beha iou al ai s o expand hei ange and
make isk- ela ed decisions, d i en by en i onmen al challenges (Bi o and S amps
2008; Yagound e al. 2022). In signal c ay ish, he beha iou al adap a ions ob-
se ed a he in asion on , including highe agg ession and isk- aking, likely
in e ac wi h ophic ecology and elemen al accumula ion. S udies by G oen e
al. (2012) and Myles-Gonzalez e al. (2015) suppo his, showing ha on indi-
iduals ake mo e isks and mo e as e , as obse ed in ou ials whe e hey we e
he i s o each he ood and domina e he space. This g ea e explo a ion and
agg ession, combined wi h hei ele a ed δ15N alues likely con ibu e o highe
bioaccumula ion o elemen s p one o biomagni ica ion, such as cobal , me cu y,
and manganese, in on o indi iduals (Kouba e al. 2010; Johnson e al. 2014).
To ensu e ha obse ed beha iou al di e ences we e no in luenced by po en ial
symbion e ec s (Skel on e al. 2013), only indi iduals wi hou isible epibion s
we e selec ed o beha iou al es s. Thus, he a ia ions in agg ession and isk- ak-
ing beha iou s a e a ibu ed o in asion- ela ed ecological ac o s a he han po-
en ial in e ac ions wi h b anchiobdellid wo ms. The educed agg ession obse ed
in co e indi iduals du ing beha iou al es s u he suppo s he hypo hesis ha
compe i ion may cons ain hei abili y o exploi highe ophic le els, in luenc-
ing elemen al accumula ion (Galib e al. 2022). Howe e , some s udies show he
opposi e. Fo example, Hudina e al. (2015) obse ed ha he signal c ay ish in a
C oa ian popula ion had highe a es o agg ession in he co e, e en hough hey
had be e physical condi ions. One possible explana ion is ha agg ession in he
co e may no necessa ily p o ide an immedia e dispe sal ad an age. S ill, i could
ins ead help main ain dominance in es ablished popula ions whe e compe i ion is
in ense. These a ia ions highligh he impo ance o s udying beha iou al ai s a
he popula ion le el a he han assuming uni o m pa e ns ac oss he species (Sou-
sa e al. 2024). Unde s anding hese beha iou al di e ences is essen ial o p edic -
ing in asion success and de eloping a ge ed managemen s a egies (see below).
In e es ingly, indi iduals om he in asion co e exhibi ed highe loads o epibi-
o ic associa es, possibly due o g ea e c ay ish densi y in his a ea, which may acil-
i a e hei ansmission (DeWi e al. 2013). Al hough b anchiobdellids a e o en
conside ed commensals o mu ualis s – by cleaning gill su aces and consuming
de i us – hei e ec s a e con ex -dependen . High loads, especially in gill cham-
54
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Diana Gonçal es e al.: Elemen al accumula ion in signal c ay ish along an in asion g adien
be s, ha e been associa ed wi h inc eased physiological s ess and educed g ow h
in c ay ish (Lee e al. 2009; Rosewa ne e al. 2012). While we did no assess gill
colonisa ion di ec ly, he g ea e abundance o b anchiobdellids in co e indi iduals
may indi ec ly in luence me abolic demands and eeding beha iou , po en ially
a ec ing elemen al accumula ion pa e ns. These in e ac ions highligh he im-
po ance o conside ing symbio ic loads when e alua ing con aminan dynamics
along in asion g adien s.
Impo an ly, he p esence o B anchiobdella as aci in signal c ay ish popula ions
in Po ugal aises biogeog aphic ques ions. Since he only na i e Eu opean c ay ish
known o hos his symbion , Aus opo amobius pallipes, does no occu in Po ugal,
i is likely ha B. as aci was co-in oduced wi h he signal c ay ish om popula ions
al eady ca ying he symbion , possibly om Spain whe e bo h occu (Le e al.
2023). This highligh s he po en ial o in asi e species o ac as ec o s no only o
con aminan s bu also o symbion s, a ec ing na i e symbion communi ies. Fo
ins ance, Le e al. (2023) ound ha B. pa asi a, a na i e symbion species, quickly
disappea s ollowing signal c ay ish in asion, likely due o p eda ion du ing g oom-
ing o lack o compa ible hos s. The e o e, while in ou s udy he p esence o B.
as aci p o ides a use ul p oxy o hos condi ion, in o he sys ems, he in oduc ion
o signal c ay ish may lead o o e looked biodi e si y losses among symbion s. These
con as ing ou comes unde sco e he need o u he esea ch on he dynamics o
symbion communi ies in in asion con ex s and hei ecological consequences.
O e all, he in e play be ween elemen al accumula ion and ecological ai s such
as die ( ophic posi ion), beha iou , and pa asi ism highligh s he complexi y o
in asion dynamics. Reduced pa asi ism a he in asion on may con e an ad-
an age, allowing indi iduals o alloca e mo e ene gy o beha iou s ha enhance
dispe sal and esou ce acquisi ion. In con as , highe pa asi ic loads a he co e
may cons ain ecological lexibili y, ein o cing he obse ed di e ences in die and
elemen accumula ion be ween sampling si es (Lee e al. 2009; Skel on e al. 2013).
Fu u e s udies should u he explo e hese ela ionships o be e unde s and how
pa asi ism in e ac s wi h elemen al accumula ion in in asi e species. This in o ma-
ion may be c ucial o be e unde s anding he dynamics o in asi e species and
possible impac s on he bioaccumula ion and biomagni ica ion, o biodilu ion o
con aminan s and should be conside ed when designing managemen s a egies.
Managemen implica ions
Managemen s a egies should p ima ily ocus on p e en ing and limi ing con am-
ina ion a i s sou ce, educing he o e all en i onmen al bu den o oxic elemen s
be o e hey en e aqua ic ood webs. This includes s ic e egula ions on indus ial
and ag icul u al emissions, imp o ing was ewa e ea men acili ies, and mon-
i o ing con amina ion ho spo s o mi iga e bioaccumula ion isks in eshwa e
ecosys ems (Nędza ek e al. 2020). In addi ion, a ge ed emo al p og ams could
be conside ed in a eas whe e signal c ay ish ac as bioaccumula o s o haza dous
con aminan s such as me cu y, po en ially educing hei a ailabili y o p eda o s
like he Eu asian o e (Lu a lu a) and b own ou (Salmo u a) (Fice ola e al.
2012; Johnson e al. 2014). Howe e , we acknowledge ha he dynamic na u e o
in asion on s, cha ac e ised by low densi ies and con inuous spa ial expansion,
p esen s logis ical challenges ha may limi he e ec i eness o la ge-scale emo als.
The e o e, hese p og ams should be in eg a ed in o b oade managemen plans,
55
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Diana Gonçal es e al.: Elemen al accumula ion in signal c ay ish along an in asion g adien
such as localised apping e o s in a eas whe e c ay ish densi ies a e high enough o
make emo al easible o in egions whe e hey pose a di ec h ea o na i e species
and human ac i i ies. Complemen a y s a egies may in ol e he selec i e emo -
al o agg essi e indi iduals a he in asion on , habi a modi ica ions o educe
e uges, ein o cemen o na i e p eda o s, and he use o biological con ol agen s
o limi c ay ish success. These e o s should be in eg a ed wi h public awa eness
campaigns and ci izen science ini ia i es o enhance communi y engagemen and
suppo long- e m managemen goals (Ghe a di e al. 2011; Al es e al. 2025).
Recen s udies highligh he human heal h isks associa ed wi h consuming sig-
nal c ay ish due o hei abili y o bioaccumula e oxic me als. Nędza ek e al.
(2020) demons a ed ha signal c ay ish om he Wiep za Ri e (sou he n Bal ic)
accumula e elemen s such as lead, cadmium, and a senic, which can exceed ac-
cep able die a y in ake limi s in ce ain body pa s. While he abdominal mea o
c ay ish can be a sou ce o essen ial elemen s such as calcium, po assium, and zinc,
consump ion o hepa opanc ea ic issues poses a po en ial heal h isk due o he
high concen a ion o oxic elemen s. This highligh s he need o isk assessmen
be o e p omo ing c ay ish ha es ing o human consump ion.
To make hese s a egies mo e e ec i e, i is c ucial o inco po a e an unde -
s anding o indi idual and popula ion-le el ai s, such as ophic ecology, be-
ha iou , and pa asi ic load, as hese ac o s can in luence con aminan accumula-
ion and dispe sal dynamics (Sousa e al. 2024). These aspec s a e o en neglec ed
in managemen s udies, ye hey may play a key ole in de e mining he success o
mi iga ion s a egies (Haub ock e al. 2024; Sousa e al. 2024). Finally, long- e m
con aminan moni o ing is essen ial o ack bioaccumula ion ends ac oss di e -
en in asion s ages. Howe e , o de elop uly e ec i e and adap i e managemen
s a egies, i is i s necessa y o cha ac e ise he con amina ion p o ile o each si e
– including bo h absolu e concen a ions and ela i e di e ences ac oss loca ions –
o be e unde s and he en i onmen al con ex and he po en ial isks associa ed
wi h ace elemen exposu e (Nędza ek e al. 2020).
Conclusion
This s udy p o ides insigh in o di e en ial elemen accumula ion in he signal
c ay ish along an in asion g adien . Ou indings e eal signi ican in a-popu-
la ion a ia ions in elemen al concen a ions, which appea o be in luenced by
ophic posi ioning, beha iou al ai s, and hos -pa asi e dynamics.
Signal c ay ish om he in asion on exhibi ed highe concen a ions o ce -
ain essen ial and po en ially oxic elemen s, such as cobal , anadium, manganese,
me cu y, and an alum. These di e ences a e likely associa ed wi h dis inc ophic
posi ions, as on indi iduals displayed highe δ15N alues, sugges ing a die ich-
e in mac oin e eb a es and highe me abolic demands. Con e sely, indi iduals
om he co e accumula ed highe le els o elemen s like lead and s on ium. Ra h-
e han solely e lec ing longe exposu e, his pa e n may be in luenced by highe
in aspeci ic compe i ion and eliance on mo e ben hic ood sou ces, such as plan
de i us. Howe e , we acknowledge ha muscle issue is no he p ima y o gan o
me al accumula ion, and u u e s udies should explo e elemen deposi ion in o he
issues such as he hepa opanc eas and gills (Balzani e al. 2021, 2022).
Beha iou al es s con i med ha indi iduals a he in asion on exhibi -
ed g ea e agg ession, ai s ha may acili a e sp ead and esou ce acquisi ion.
56
NeoBio a 102: 37–62 (2025), DOI: 10.3897/neobio a.102.148414
Diana Gonçal es e al.: Elemen al accumula ion in signal c ay ish along an in asion g adien
Addi ionally, he educed pa asi ic load obse ed in he on o he in asion
g adien unde sco es he po en ial adap i e bene i s o lowe hos densi ies and
no el en i onmen s, leading o highe consump ion and po en ially highe ac-
cumula ion o ce ain elemen s.
O e all, hese indings unde sco e he complex in e ac ions be ween in asion
dynamics, en i onmen al con aminan s, and ecological ai s. By combining ele-
men al analysis, s able iso ope da a, and beha iou al obse a ions, his s udy con-
ibu es o a be e unde s anding o he ecology o a highly in asi e species in
eshwa e ecosys ems.
Addi ional in o ma ion
Con lic o in e es
The au ho s ha e decla ed ha no compe ing in e es s exis .
E hical s a emen
No e hical s a emen was epo ed.
Funding
This s udy was suppo ed by he Po uguese Founda ion o Science and Technology (FCT) h ough
na ional unds unde he p ojec MULTI-CRASH: Mul i-dimensional ecological cascades igge ed
by an in asi e species in p is ine habi a s (PTDC/CTA-AMB/0510/2021) (h ps://doi.o g/10.54499/
PTDC/CTA-AMB/0510/2021) and he Scien i ic Employmen S imulus – 6 h Edi ion (2023.07078.
CEECIND) (h ps://doi.o g/10.54499/2023.07078.CEECIND/CP2841/CT0002).
Au ho con ibu ions
Concep ualiza ion: JAGP. Da a cu a ion: JAGP, DG. Fo mal analysis: DG, JAGP. Funding acquisi-
ion: RS, PN. In es iga ion: JSK, RS, DG. Me hodology: JSK, PN, JAGP. P ojec adminis a ion:
RS. Resou ces: PN, JSK, JAGP. Supe ision: JAGP, RS. Valida ion: RS. W i ing – o iginal d a :
JAGP, DG. W i ing – e iew and edi ing: JAGP, DG, RS, JSK, PN.
Au ho ORCIDs
Diana Gonçal es h ps://o cid.o g/0009-0009-5555-6130
Ronaldo Sousa h ps://o cid.o g/0000-0002-5961-5515
Juliana Souza-Kasp zyk h ps://o cid.o g/0000-0003-2307-8006
P zemyslaw Niedzielski h ps://o cid.o g/0000-0002-2787-9057
Amílca Teixei a h ps://o cid.o g/0000-0001-5336-1174
Janeide de Assis Guilhe me Padilha h ps://o cid.o g/0000-0002-1901-5822
Da a a ailabili y
All o he da a ha suppo he indings o his s udy a e a ailable in he main ex o Supplemen a y
In o ma ion.
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