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Short Communication
Concerning Predation on Small Vertebrates by Alien Gold Morph Midas
cichlid, Amphilophus citrinellus (Cichlidae)
Authors:
Mohamad Aqmal-Naser and Amirrudin B. Ahmad*
*Correspondence: amirrudin@umt.edu.my
Submitted: 21 June 2023; Accepted: 30 January 2024; Published: 31 July 2024
To cite this article: Mohamad Aqmal-Naser and Amirrudin Ahmad. (2024).
Concerning predation on small vertebrates by alien gold morph Midas cichlid,
Amphilophus citrinellus (Cichlidae). Tropical Life Sciences Research 35(2):
309–317. https://doi.org/10.21315/tlsr2024.35.2.15
To link to this article: https://doi.org/10.21315/tlsr2024.35.2.15
Highlights
•Midas cichlid feed on a wide array of preys including sh, amphibian and
gastropod.
•Midas cichlid in the rice agroecosystem have negative allometric growth
(b = 2.60) and the relative condition factor, Kn is 1.04.
•New information on the feeding ecology of Midas cichlid in their introduced
range.
TLSR, 35(2), 2024
© Penerbit Universiti Sains Malaysia, 2024
© Penerbit Universiti Sains Malaysia, 2024. This work is licensed under the terms of the Creative
Commons Attribution (CC BY) (http://creativecommons.org/licenses/by/4.0/).
Tropical Life Sciences Research, 35(2), 309–317, 2024
Short Communication
Concerning Predation on Small Vertebrates by Alien Gold Morph
Midas cichlid, Amphilophus citrinellus (Cichlidae)
1Mohamad Aqmal-Naser and 1, 2 Amirrudin B. Ahmad*
1Terrestrial Ecology, Biodiversity and Aquatic Research (TEBAR), Institute of Tropical
Biodiversity and Sustainable Development, Universiti Malaysia Terengganu, 21030 Kuala
Nerus, Terengganu, Malaysia
2Biodiversity and Ecology Research (BERes), Faculty of Science and Marine Environment,
Universiti Malaysia Terengganu, 21030 Kuala Nerus, Terengganu, Malaysia
Submitted: 21 June 2023; Accepted: 30 January 2024; Published: 31 July 2024
To cite this article: Mohamad Aqmal-Naser and Amirrudin Ahmad. (2024). Concerning
predation on small vertebrates by alien gold morph Midas cichlid, Amphilophus
citrinellus (Cichlidae). Tropical Life Sciences Research 35(2): 309–317. https://
doi.org/10.21315/tlsr2024.35.2.12
To link to this article: https://doi.org/10.21315/tlsr2024.35.2.12
Abstract: Neotropical cichlid possesses territorial aggression which explains their success
as alien species that pose threats to local fauna. The feeding ecology of Midas cichlid,
Amphilophus citrinellus species outside its native range had never been fully understood.
We aim to determine the stomach content, length-weight relationship and condition factor
of this non-native species in one of the agroecosystems in Malaysia. The sh was collected
using a cast net, and the guts were dissected. The stomach content (n = 35) revealed Midas
cichlids feed on a wide array of preys including sh, amphibian and gastropod. The b-value
is 2.60 (negative allometric growth) and the relative condition factor, Kn is 1.04. This result
represents an initial study on the feeding aspect of this cichlid. Subsequent and continued
researches are needed to evaluate the feeding behaviour and prey preferences of this
species in its introduced range.
Keywords: Biodiversity, Introduced Species, Invasiveness, Peninsular Malaysia, Rice
Agro-Ecosystem
Abstrak: Cichlid neotropika mempunyai pencerobohan wilayah yang menjelaskan
kejayaan mereka sebagai spesies asing yang menimbulkan ancaman kepada fauna
tempatan. Ekologi pemakanan Midas cichlid, spesies Amphilophus citrinellus di luar julat
asalnya tidak pernah difahami sepenuhnya. Kami berhasrat untuk menentukan kandungan
perut, hubungan panjang-berat dan faktor keadaan spesies bukan asli ini dalam salah
satu agroekosistem di Malaysia. Ikan dikumpul menggunakan jaring tuang dan ususnya
dibedah. Kandungan perut (n = 35) mendedahkan Midas cichlids memakan pelbagai jenis
mangsa termasuk ikan, ambia dan gastropod. Nilai b ialah 2.60 (pertumbuhan alometrik
* Corresponding author: amirrudin@umt.edu.my
Mohamad Aqmal-Naser and Amirrudin B. Ahmad
310
negatif) dan faktor keadaan relatif, Kn ialah 1.04. Keputusan ini mewakili kajian awal
tentang aspek pemakanan cichlid ini. Penyelidikan seterusnya dan berterusan diperlukan
untuk menilai tingkah laku pemakanan dan keutamaan mangsa spesies ini dalam julat yang
diperkenalkan.
Kata kunci: Biodiversiti, Spesies Pengenalan, Invasif, Semenanjung Malaysia, Agro-
Ekosistem Beras
INTRODUCTION
Midas cichlid, Amphilopus citrinellus exhibits polychromatism, with two general colour
morphs throughout its growth induced by breeding mode, location and water depth
(Barlow 1976). The gold morphs A. citrinellus were typically aggressive, possibly as
a response to predation (Barlow & Wallach 1976), and also owing competition over
limited resources in their niche (Oldeld 2011), allowing them to survive outside the
native range. This morph also showing the domination against the normal morph
in term of predation and growth (Barlow et al. 1975). We believe such territorial
aggression may be demonstrated constantly by A. citrinellus gold morph sh and it
is persisting even when found outside their native environment.
A. citrinellus has been reported from outside its native ranges including
Australia (Kroon et al. 2015), Indonesia (Tampubolon et al. 2015), Malaysia (Aqmal-
Naser & Ahmad 2018a; 2020), Philippines (Poniente et al. 2019) and Singapore (Tan
et al. 2020). Established feral populations of A. citrinellus have been reported from
several countries including Singapore (Kwik et al. 2013) and Indonesia (Tampubolon
et al. 2015), which suggest that this species soon could be another cichlid species
invading natural waterbodies after tilapias (Oreochromis spp.). However, the feeding
ecology of A. citrinellus outside its native range, especially in Peninsular Malaysia,
is relatively unknown.
In this study, we examined the stomach contents of A. citrinellus populations
thriving in agro ecosystem to investigate the potential impacts of this alien sh
species to native biota. Since food is one of the keys in determine sh condition,
population, level and growth rate (Begum et al. 2008), the information gathered
on the diet of sh is crucial to understand their behaviour, biology and physiology
(Shalloof et al. 2020). The study on feeding habit also can help to explain the biology
of single species (Graham et al. 2007), and the trophic ow of the ecosystem (Cox
et al. 2023). Our study is important for establishing the fundamental criteria of the
potential invasiveness of the aggressive A. citrinellus in Peninsular Malaysia and
the ndings could be applicable to other places outside its native distribution range.
MATERIALS AND METHODS
The occurrence of A. citrinellus at this study sites has been previously reported
by Aqmal-Naser and Ahmad (2020). The samples of A. citrinellus were collected
Diet of Midas cichlid
311
opportunistically from the rice eld. Samples were collected using cast net with a
dimension of 2.4 m height × 10 m circumference × 2 cm mesh size. All collected
specimens were measured for standard length (SL; tip of the upper jaw to the
base of caudal n to the nearest mm). The gut was removed and dissected for
visual examination of the stomach contents and the occurrence of the eggs in
the abdominal cavity was recorded to indicate their ability to reproduce and to
establish feral population at the study area. Any larger native fauna found in the
stomach were identied using visible characters to the lowest possible taxon. The
identication of sh species was based on Zakaria-Ismail et al. (2019), while the
identication for frog and toad species were based on Grismer (2011). The sh
stomach content analysis was done using Occurrence Method (Frequency of
occurrence; %) as suggested by Hyslop (1980). The number of stomachs contain
one or more individuals for each category of food and expressed as percentage
(Kennedy & Fitzmaurice 1972). All specimens were preserved in 10% formalin
solution and transferred to 75% ethanol after two weeks and deposited in Universiti
Malaysia Terengganu Zoological Collection (UMTZC). The growth condition
(b-value) of the sh were determined following the formula W = aLb (Ricker 1973)
where W = weight of sh in gram; L = Length of sh in cm; a = describe the rate of
change of weight with length (intercept); and b = weight at unit length (slope), while
relative condition factor (Kn) following Le Cren (1951).
RESULTS
From the survey, we collected 35 specimens of gold morphs A. citrinellus (total
length; 3.00 cm–18.50 cm, and weight 1.30 g–254.22 g). The growth condition
(b-value) for the cichlid is 2.60, while the relative condition factor (Kn) is 1.04
(Fig. 1). The stomach content from two individuals contained native fauna; frog
(Family Dicroglossidae), and a native ghting sh species (Betta imbellis). One
individual is a gravid female and the stomach contain the remain of unidentied
gastropod (Fig. 2). Stomach content of 20 individuals contain unidentied sh
scales while the other 12 individuals’ sh had empty stomachs.
Table 1: The stomach content analysis for Amphilophus citrinellus (n = 35) with the
percentage of occurrence (%FO) of three groups of fauna.
Class Family (% FO) Remarks
Actinopterygii Opshronemidae 2.86 Betta imbellis (n = 1)
Unidentied species 57.14 Unidentied sh scales (n = 20)
Amphibia Dicroglossidae 2.86 Partially digested frog (n = 1)
Gastropoda Ampullariidae 2.86 Unidentied mollusc (n = 1)
Empty stomach - 34.29 n = 12
Mohamad Aqmal-Naser and Amirrudin B. Ahmad
312
Figure 1: Length-weight relationship of Midas cichlid in the study site (n = 35).
Figure 2: The stomach contents of Amphilophus citrinellus containing: (A) partially digested
native frog (Dicroglossidae); (B) native sh, Betta imbellis; (C) the operculum size of the
gastropod; and (D) the remnant of gastropod along with egg cluster.
Diet of Midas cichlid
313
DISCUSSION
Documented evidence of such predation by alien shes in Peninsular Malaysia is
scarce, with the exception of Clarias gariepinus (Aqmal-Naser & Ahmad 2019).
Several small-bodied native sh species had been previously reported at the study
site (Aqmal-Naser & Ahmad 2018b), where some of these native species hold
commercial potential for small-scale ornamental trade [(e.g., Rasbora trilineata,
Oryzias javanicus, Lepidochepalichthys hasselti and Betta imbellis (Aqmal-
Naser & Ahmad 2018b)], but may be threatened by the predation pressure from
A. citrinellus. Given the aggressive behaviour demonstrated by this species
complex, the gold morph of A. citrinellus has been known to attack and eat small
shes (Barlow et al. 1975). Aggression behaviour demonstrated by this Midas
cichlid may be extended to the feeding needs of the sh. The sh not only respond
aggressively towards their own morph as previously reported (Lehtonen 2014)
but may aggressively prey upon the native species. Our study presents the rst
evidence on the predation of native frog and sh species, and also conrming
the predation on snail species by A. citrinellus in Peninsular Malaysia. Since
A. citrinellus has now occurred regularly in human-modied habitats (Kwik et al.
2013; Tampubolon et al. 2015), impacts on native sh community may be amplied
in the near future if precautionary steps are not taken.
Several other predatory sh species can be found in the rice eld (see
Aqmal-Naser & Ahmad 2018a; 2018b). Many of these shes feed on invertebrates,
small shes, and a few species such and the snakehead, Channa striata, the top
predator in this agro ecosystem, feed on vertebrates including frogs. Dicroglossid
frogs are common and widespread in the rice elds in Peninsular Malaysia
(Shahriza & Ibrahim 2017) and are preyed by many species including snakes. With
that being said, predation of a native frog by an alien sh has not been previously
reported. The unexpected nding of A. citrinellus feeding on a native dicroglossid
frog is recorded for the rst time in Peninsular Malaysia. Elsewhere, predation
of native frogs by the alien sh species, Clarias gariepinus has been previously
documented in Cuba (Rodríguez-Machado & Rodríguez-Cabrera 2015), even on
the critically endangered spiny-chest frog (Alsodes pehuenche) by introduced
rainbow trout, Onchorhynchus milkyss (Zarco et al. 2020).
Our nding of A. citrinellus feeding on the native frog not only represents
a threat to native fauna, but also may also imply competition with native predators
for the same food resources. Without appropriate control measures, this may
contribute to the loss of native biodiversity. Eventually, long term eects of alien
sh species in the natural and man-made habitats are proliferated. Thus, a
systematic and urgent plan is required for eradicating the invasive species plus
further study and continued monitoring of this event must be executed immediately.
Both A. citrinellus (in this study) and Clarias gariepinus (of the previous study)
were recorded feeding on the native species within the same study area. Upon
reaching a certain size, both of these alien species have no native predators (with
the possible exception of the water monitor lizard, Varanus salvator). Given that
this man-made ecosystem contains many small-bodied sh species, predation on
Mohamad Aqmal-Naser and Amirrudin B. Ahmad
314
native species likely occurs more frequently. Since both alien sh species feed on
the same resources, competition for food between A. citrinellus, C. gariepinus and
the native Channa striata may nally intensify.
While there is currently limited evidence of breeding populations (e.g.,
lack of juveniles), their feeding preferences posed a potential threat to the native
biota. The initial discovery on a pair of A. citrinellus which the female is gravid
(Fig. 2) could armed the possibility of establishing the breeding population soon.
In the man-made habitat in Singapore, the species was known to have established
population based on the size range from small to large and the presence of breeding
pit (Kwik et al. 2013). Furthermore, Purnamaningtyas and Tjahjo (2017) reported
that A. citrinellus has high fecundity in the reservoir and can breed throughout the
year given that the water temperature ranging from 24°C–28°C.
Purnamaningtyas and Tjahjo (2017) also reported larger Midas cichlid has
higher fecundity, where each female has about 1,000–3,000 eggs. They usually
lay their eggs on the ceiling of natural caves or hard substrates (Lavery 1991),
which in this study, the pair was collected from the concrete canals. However, the
reproductive aspect of Midas cichlid is complex. The species is monogamous and
spawning selection is complex (Rogers 1987). The female tends to choose normal
and primitive colour male, the largest and the most aggressive male to spawn
(Barlow 1992). Increasing number of male or crowding eect will have inuence
on the mating of Midas cichlid (Rogers 1987). The male is not choosy, but female
will usually have individual selection, where it will choose male with high tendency
to be a good father to the fry (Barlow 1992).
Midas cichlid population in this study shows negative allometric growth
(b < 3.0) where the length increases but the weight did not increase proportionally.
The relative condition factor of 1.04 also shows that the Midas cichlid population
having the borderline growth condition between poor and good. The sh become
slimmer or thinner, as one of the reasons, is the lack of food resources (Jisr et al.
2018). The empty stomach of 34.29% indicated the scarcity of food availability,
hence Midas cichlid could devour any organism available including the frog.
Plus, this agroecosystem is a highly disturbed environment, both temporally and
spatially (Aqmal-Naser et al. 2023). Such factors as habitat and environments, are
among the major factor contributing to the poor growth of sh (Morato et al. 2001).
Compared to the related study, Midas cichlid in Indonesia has isometric growth
(b = 3.5), as they consumed diverse food including insect larvae, insect and plant
matters (Purnamaningtyas & Tjahjo 2017).
We were aware that the sample size of this cichlid in this study can be
considered small (n = 35 individuals). Nevertheless, the veracious feeding behaviour
shown through this observation is a clear indication that once the population of this
alien species established, similar feeding behaviour will be observed and become
more prominent, especially when the competition for food is escalating. Our nding
provides an impetus for further studies on the potential impacts by A. citrinellus in
other human-modied habitats, particularly in the urban areas of the central west
coast (i.e., Selangor) and southern Peninsular Malaysia (e.g., Johor and Negeri
Sembilan), which man-made habitats such as retention ponds, reservoirs and ex-
Diet of Midas cichlid
315
mining pools are abundant that A. citrinellus was thriving well. Additional sampling
on the other states in Peninsular Malaysia may provide ancillary data for better
understanding on the impacts of this sh to the native biota. This data then can
be used to suggest and provide crucial information on the potential “hotspots” of
alien sh species in Peninsular Malaysia, which is important for informing potential
control and/or extermination measures. Another future studies should explore
on the possibility of A. citrinellus demonstrate bias aggression towards their own
morph as this might explain the less numerous individuals collected during the
sampling.
The occurrence of alien sh species with potential to become invasive
in man-made and natural water bodies urgently requires monitoring and control.
Owing to the limited information on their feeding ecology and biology, alien
sh species were not previously regarded as a threat to native fauna and have
hitherto of less interest from the researchers in Peninsular Malaysia. The concrete
eradication measures are urgently needed as the negative ecological impacts of
alien species start to escalate.
ACKNOWLEDGEMENTS
We thank Universiti Malaysia Terengganu for the facilities and equipment used
in the study. We thank Baizul Hafsyam for the identication of the frog. We thank
Dr. Kenny WJ Chua for comments and suggestions to improve the manuscript.
Amirul, Amirah, Aisha and Azira are gratefully acknowledged.
AUTHORS’ CONTRIBUTIONS
Mohamad Aqmal-Naser: Study conception, idea and design; carried out the
sample collection; analyse the result; wrote and approved the nal version of the
manuscript.
Amirrudin B. Ahmad: Study conception, idea and design; wrote and approved the
nal version of the manuscript.
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