IQBAL ET AL.
Bio Palembanica 2.
: 116-122 .
This journal is available online at: https://ejournal.
Missing Web: Reporting a Gap in Fish Predation by Spiders (Arachnida: Aranea.
in Indonesia MUHAMMAD IQBAL1*.
RIZA MARLON2.
AKHMAD JUNAEDI SIREGAR3 & SWARLANDA4
Department of Biology.
Universitas Indo Global Mandiri.
Jalan Jend.
Sudirman No.
Palembang 30129.
South Sumatra.
Indonesia *Corresponding Author.
E-mail: miqbal@uigm.
https://orcid.
org/0000-0002-6657-0183 Riza Marlon Indonesia Wildlife.
Bogor.
Indonesia E-mail: rizamarlon@gmail.
Bumilan Istiqo Inno.
Jalan Kelambir Lima Kebun.
Gang Bunga No.
Hamparan Perak.
Deli Serdang 20374.
Sumatera Utara.
E-mail: juned_sir@yahoo.
https://orcid.
org/0009-0004-5713-9967 Yayasan Ikan Endemik Bangka Belitung.
Tua Tunu.
Gerunggang.
Pangkal Pinang 33172.
Provinsi Kepulauan Bangka Belitung.
Indonesia E-mail: swarlanda@gmail.
https://orcid.
org/0009-0001-3897-6389 Received 18 August 2025iCAccepted by I.
Aprillia: 10 November 2025iCPublished online 27 December 2025.
Abstract Indonesia, one of the worldAos most biodiverse countries, hosts a staggering array of ecosystems and species, many of which remain undocumented, particularly spider (Arachnida: Aranea.
While spiders are widely recognized for preying on insects and small animals, fish predation by spiders is a rare behavior predominantly associated with semi-aquatic species such as Dolomedes.
This study reports three instances of fish predation by spiders in Indonesia, observed across North Sumatra Province.
Bangka Belitung Islands Province and East Kalimantan Province during biodiversity fieldwork in 2004, 2022 and 2024.
Spider and fish species involved were identified using taxonomic keys and photographic documentation, revealing interactions between Dolomedes sp.
and fish from taxa such as Cyprinid.
Common Snakehead Channa striata and Licorice Gourami Parosphromenus sp.
These findings provide valuable insights into this understudied phenomenon and highlight the need for further research into spider predation in IndonesiaAos freshwater habitats.
Keywords: Arachnida.
Araneae, fish predation.
Indonesia, semi-aquatic spider.
Introduction Indonesia is one of the most biodiverse countries in the world, boasting a staggering variety of ecosystems that range from mangroves, coastal forests, lowland forests and montane forests (Iqbal et 2020, 2023.
Arifah et al.
This biodiversity hotspot is home to thousands of unique species, many of which are endemic to the region (Setiawan et al.
2018, 2020.
Setiawan et al.
Among its extraordinary wildlife.
Indonesia harbors an impressive diversity of arachnids and insects, with many species yet to be discovered and documented, making it a crucial area for arachnological and entomological research (Pashkevich et al.
Aprillia et al.
One of the most overlooked aspects of IndonesiaAos incredible biodiversity is its spiders (Rachman et al.
Dhiya'ulhaq et al.
IndonesiaAos spiders are astonishingly diverse, ranging from strikingly colorful jumping spiders (Salticida.
, which exhibit complex hunting behaviors, to orbweaving spiders (Araneida.
that create intricate webs to trap prey (Dhiya'ulhaq et al.
2023, 2.
Despite being critical components of ecosystems, spiders often get overshadowed by larger, more charismatic fauna like Sumatran Tiger Panthera tigris sondaica.
Orangutans Pongo spp.
or Komodo Dragons Varanus komodoensis (Ysnel et al.
Milano et al.
Across its lush rainforests, winding mangroves, and diverse freshwater systems.
Indonesia hosts a myriad of species engaged in remarkable predator-prey dynamics (Iqbal et al.
2025a, 2025.
Among these, spiders have long been recognized as formidable hunters, preying on insects and small animals (Ratz et al.
Saksongmuang et al.
Fish predation by spiders is a rare but remarkable Missing Web: Reporting a Gap phenomenon, primarily associated with semi-aquatic spider species like those in the genus Dolomedes (Bleckmann & Lotz 1987.
Figiel & Miller 1.
In this paper, we address the previously undocumented occurrence of fish predation by spiders in Indonesia, reporting a significant gap in knowledge regarding this behavior and its ecological implications in the region.
Methods To investigate the gap in fish predation by spiders in Indonesia, field observations were conducted across three distinct regions: East Kalimantan Province.
North Sumatra Province and Bangka Belitung Islands Province (Fig.
All observations are based on incidental observations of fish predation by spiders across three locations in Indonesia.
These observations occurred during biodiversity fieldwork, where instances of spider behavior targeting fish were unexpectedly recorded.
While the observations were not part of a structured study, they provide valuable insight into a rarely documented predator-prey Spider species were identified based on taxonomic keys and descriptions provided by Koh & Ming .
Koh & Bay .
and Koh et al.
while fish species were identified following Sumatran fish references (Iqbal et al.
2018, 2020.
Arifah et al.
Figure 1.
The map displays the distribution of incidental observations of fish predation by spiders across three sites in Indonesia during the years 2004, 2022, and 2024.
Yellow circles mark the locations, with numbers on the map corresponding to entries in Table 1.
All observations were documented with photographs, and detailed field notes, including information on the location, habitat type, spider behavior, and the size/species of fish involved .
here While the unstructured nature of these observations limits the scope of analysis, they provide a foundation for future investigations into spider predation on fish in Indonesia.
IQBAL ET AL.
Results and Discussion Three instances of fish predation by spiders were recorded in East Kalimantan.
North Sumatra, and Bangka Belitung Islands Province, showcasing the phenomenon in varied locations across Indonesia, as presented in Table 1.
All of spiders are documented as Dolomedes species.
Dolomedes is closely related to Nilus, a genus of waterside fishing spiders.
In the field.
Dolomedes are recognizable by their shorter abdomen and distinctive velvety fringes on the sides of their carapace and abdomen, setting them apart from Nilus (Koh & Ming 2014.
Koh et al.
Dolomedes species from East Kalimantan features a black body adorned with frequent white spots on both its body and legs (Fig.
In contrast, the Dolomedes spider from North Sumatra exhibits a plain yellow coloration without any distinct patterns or spots (Fig.
Meanwhile, the Dolomedes spider from Bangka Island resembles the East Kalimantan variant but lacks the white spots on its body and legs (Fig.
Table 1.
A record of incidental observations of fish predation by spiders at three locations in Indonesia, spanning the years 2004, 2022, and 2024.
East Kalimantan North Sumatra Spider .
Dolomedes sp.
Dolomedes sp.
Fish .
Cyprinid (Cyprinida.
Common Snakehead Channa striata Bangka Island Dolomedes sp.
Gourami Parosphromenus sp.
No.
Date Location/Province Undated, 2004 26 October 2022 8 September 2024 The fish species from the three locations represent distinct taxa.
In East Kalimantan, the fish is an unidentified cyprinid species, whereas the fish from North Sumatra is a juvenile Common Snakehead Channa striata.
On Bangka Island, the fish is identified as a Gourami Parosphromenus sp.
These differences in fish taxa highlight the diverse aquatic ecosystems across Indonesia.
The variation in prey species may also suggest unique hunting adaptations among Dolomedes spiders in different regions.
Figure 2.
The spider Dolomedes sp.
fed a cyprinid fish species in East Kalimantan Province in 2024 (Photograph: Riza Marlo.
Missing Web: Reporting a Gap Figure 3.
A spider Dolomedes sp.
fed on a young Common Snakehead Channa striata on 26 October 2022 in North Sumatra Province (Photograph: Akhmad Junaedi Sirega.
Figure 4.
A spider Dolomedes sp.
fed on a Licorice Gourami Parosphromenus sp.
on 8 September 2024 in Bangka Island.
Bangka Belitung Islands Province.
Sumatra.
" (Photograph: Swarland.
IQBAL ET AL.
The results demonstrate that fish predation by spiders, though incidental and infrequent, does occur in Indonesia's diverse aquatic habitats.
These findings align with global reports of similar behavior in semi-aquatic spiders, such as those in the Dolomedes genus (Nyffeler & Pusey 2.
However, this study provides some of the first documented evidence of such interactions in Indonesian ecosystems, involving known fish species such as cyprinids, snakeheads, and gouramy.
For DolomedesAisemiaquatic spiders known for hunting on water surfacesAiscientists may still face challenges in identifying species, distinguishing them from similar ones, and organizing them into clear categories, likely due to limited studies, overlapping characteristics, or insufficient genetic data, leaving many species within the genus undocumented, poorly described, or even undiscovered (Tanikawa & Miyashita 2008.
Cazanove et al.
The observation from East Kalimantan suggests that peat swamp forests, with their waterlogged habitats and dense vegetation, may provide an ideal environment for spider predation on cyprinids.
Cyprinids are often abundant in these slow-moving waters (Iqbal et al.
2017a, 2017.
, making them accessible prey for spiders.
Similarly, the rainforest riverbank in North Sumatra revealed predation on snakeheads, which are air-breathing fish commonly found in shallow water (Qin & Fast 1.
This suggests that spiders may exploit the snakehead's surface activity for successful predation.
In Bangka Belitung, the predation of gouramy in heat forest .
or peatswamp forest highlights the adaptability of spiders to nutrient-poor and acidic environments, where juvenile gouramy are often found navigating the roots and shallow waters (Iqbal 2.
The scarcity of such observations may be attributed to several factors.
First, fish predation by spiders is likely a rare or opportunistic behavior, making it difficult to observe during structured studies.
Second, the behavior may occur more frequently in remote or underexplored habitats, which are challenging to access.
Finally, ecological pressures such as habitat degradation or pollution could be reducing the prevalence of such interactions in certain regions.
These findings open up opportunities for further research.
Structured studies focusing on semi-aquatic spiders in Indonesia could provide more comprehensive data on the frequency, prey preference, and ecological significance of fish predation.
Additionally, understanding how environmental factors like water quality or vegetation density influence this behavior could enhance our knowledge of predator-prey dynamics in aquatic ecosystems.
Acknowledgments We thank Riza Marlon Indonesia Wildlife.
Herpetologer Mania.
Tanggoker and Universitas Indo Global Mandiri (UIGM) for facilitating us to study fish predation by spiders in Indonesia.
References