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Species range evolution of the rocky intertidal leaf oyster Isognomon nucleus (Lamarck, 1819) in the Indo-Pacific
(2026-08-01)
Mahyotsanun, Patteera
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Shahdadi, Adnan
;
Ganmanee, Monthon
;
Chan, Benny K.K.
The small-sized leaf oyster, Isognomon nucleus, inhabits intertidal rock crevices across the tropical and subtropical Indo-Pacific (IP). This study examines the phylogeography of I. nucleus across the IP and the evolution of its distribution range using three mitochondrial markers, COX1, 12S, and 16S, and the nuclear ITS1 marker. Our phylogenetic analyses revealed a widely distributed Indo-Pacific lineage of I. nucleus from the Andaman Sea to Hawaii, and two further deeply diverged but morphologically cryptic lineages: Isognomon cf. nucleus 1, restricted to Taiwan, and Isognomon cf. nucleus 2, occurring in Taiwan and Hainan (China). Phylogeographic analyses revealed extensive gene flow within I. nucleus, spanning from the Andaman Sea in the Indian Ocean through the Philippines and Taiwan in the western Pacific to Hawaii in the Central Pacific. This high dispersal capacity is likely facilitated by west–east flowing equatorial currents and the species’ strong environmental tolerance. Higher pairwise Φst values between Hawaii and other localities indicate reduced gene flow between Hawaii and the Indo–West Pacific, consistent with Hawaii's geographic isolation. The Hawaiian endemic Isognomon californicus is closely related to I. cf. nucleus 1, suggesting that both evolved from a common ancestor and diverged as a result of limited dispersal between Taiwan and Hawaii. Demographic analyses detected clear signals of population expansion in I. nucleus coinciding with the sea level changes in the Last Glacial Maximum.
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Utilization of micro-snail Stenothyra species as a co-feed for giant tiger prawn
(2026-06-01)
Aue-umneoy, Dusit
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Pinphoo, Piyarat
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Thuamsuwan, Worachet
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Janeauksorn, Kittipong
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Meethong, Grissada
Giant tiger prawn (Penaeus monodon) is one of the most commercially important species in global intensive shrimp aquaculture. However, rising fishmeal prices have driven increases in feed costs, prompting some farmers to use lower-quality feeds, which can negatively affect shrimp growth performance. Natural micro-snails, such as Stenothyra sp., have been identified as potential co-feeds for P. monodon. Therefore, this study aimed to investigate the effects of Stenothyra sp. as a co-feed on the growth performance and feed efficiency of P. monodon. Juvenile shrimp were assigned to two treatment groups (n = 20 per group): control (fed artificial pellets) and co-feed (fed artificial pellets supplemented with live micro-snails). The specific growth rate was higher in the co-feed group (8.4 ± 0.11% per day) than that in the control group (7.2 ± 0.34% per day). The final body weight was approximately 61% higher in the co-feed group than that in the control group. Similarly, feed efficiency (119.6 ± 2.73% vs. 77.5 ± 2.90%) and total protein intake (6.8 ± 0.17 g vs. 1.7 ± 0.06 g) were significantly higher in the co-feed group than those in the control group, indicating better feed and nutrient utilization following Stenothyra sp. supplementation. In conclusion, under the tested conditions, providing Stenothyra sp. as a co-feed improved growth performance and feed efficiency in juvenile P. monodon, possibly due to increased total protein intake. Overall, this study presents an innovative co-feeding strategy with potential benefits; however, its broader practical and economic implications require further evaluation.
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Two Routes to Land: Genomic Underpinnings of Parallel Aerial Egg Deposition in Aquatic Old-World Pila and New-World Pomacea (Ampullariidae)
(2026-01-01)
Zhou, Yufei
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Mu, Huawei
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Nie, Xueying
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Gao, Yue
;
Wang, Hui
The evolution of aerial oviposition in Old-World Pila and New-World Pomacea apple snails—diverged since the Gondwanan breakup—offers a powerful model for probing genomic adaptations underpinning key evolutionary innovations. We generate a chromosomal-level genome for Pila celebensis and a scaffold-level genome for Pila pesmei, revealing a genus-specific doubling in genome size driven by transposable element expansions. Analyses of macrosynteny and topologically associating domains (TAD) identified lineage-specific chromosomal rearrangements associated with positive selection in gene blocks enriched for environmental sensing, metabolism, and stress response. Breakpoints in aerial egg layers preferentially are localized within TADs, suggesting convergent rewiring of gene regulation. Gene family evolution revealed parallel expansions in cellulases, β-D-xylosidases, and immune genes, alongside convergent positive selection in aquaporins critical for aerial osmoregulation. Perivitelline fluid (PVF) proteomics uncovered the central role of PVF1, likely acquired via ancient horizontal gene transfer (HGT) from viruses in the Ampullariidae ancestor in the Jurassic. Subsequent duplications enabled lineage-specific adaptation; PVF1 in aerial eggs shows parallel increases in hydrophobicity and aromatic residues (notably phenylalanine), enhancing desiccation resistance. Collectively, these convergent genomic mechanisms—structural rearrangement, gene family dynamics, and HGT-driven innovation—underpin the independent evolution of aerial oviposition in Pila and Pomacea, providing a multi-layered blueprint for understanding key ecological transitions.
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Thermal fluctuations independently modulate physiological plasticity and the dynamics of the gut microbiome in a tropical rocky shore oyster
(2024-04-01)
Arromrak, Bovern Suchart
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Wong, Adrian Tsz Chun
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Hui, Tin Yan
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Leung, Kin Sum
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Williams, Gray A.
Extreme high thermal conditions on tropical rocky shores are challenging to the survival of intertidal ectotherms. Yet, many species are highly successful in these environments in part due to their ability to regulate intrinsic mechanisms associated with physiological stress and their metabolic demand. More recently, there has been a growing awareness that other extrinsic mechanisms, such as animal-associated microbial communities, can also influence the tolerance and survival of ectotherms under stressful conditions. However, the extent to which the intrinsic and extrinsic mechanisms are functionally linked as part of the overall adaptive response of intertidal animals to temperature change and stress is poorly understood. Here, we examined the dynamics and potential interactions of intrinsic and extrinsic mechanisms in the tropical high-supratidal oyster, Isognomon nucleus. We found that oysters modulate their internal biochemistry (oxidized PUFA products, including 5-F<inf>2t</inf>-IsoP, 10-F<inf>4t</inf>-NeuroP, 13-F<inf>4t</inf>-NeuroP, and 16-F<inf>1t</inf>-PhytoP) as part of their adaptive regulation to cope with physiological stress during periods of extreme high temperatures when emersed. However, while we detected variation in alpha diversity (ASV richness and Shannon diversity index), dominant microbial taxa and microbial functions across time, no association was found with the host biochemical profiles. The findings here suggest that the thermal condition within oysters can independently influence their intrinsic biochemical responses and extrinsic microbiome profiles. Together, these mechanisms may contribute to the thermal tolerance and survival of the oysters in the challenging conditions of the tropical high-supratidal zone.
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Genetic differentiation and host usage of coral and fire coral-associated barnacles (Cirripedia: Pyrgomatinae and Wanellininae) across the Indian and Pacific Oceans
(2023-12-01)
Yu, Meng Chen
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Ganmanee, Monthon
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Tsao, Yao Feng
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Chan, Benny K.K.
Using two molecular markers (COI and 12S) collected from seven genera and 20 species of coral associated and fire coral-associated barnacles, we examined whether genetic differentiation occurs between the Indian (total 261 sequences) and Pacific populations (195 sequences). Molecular phylogenetic analysis revealed pyrgomatinid barnacles formed two major sister-clades: the Cantellius clade and the major clade. Most of the species in the Cantellius clade did not show Indo-Pacific genetic divergence, except Cantellius sextus, which formed sister Indian and Pacific Ocean clades. Within the major clade, Darwiniella angularis, Galkinius maculosus, Nobia grandis, and Hiroa stubbingsi were composed of well-supported clades corresponding to the Indian and Pacific Oceans. The fire coral-associated barnacles Wanella milleporae have molecular clades corresponding to the populations in the Red Sea, Phuket waters, and Pacific Ocean. Species delimitation analyses and haplotype network supported the divergence of sequences in some coral barnacle species and fire coral barnacle between Indian and Pacific populations. Indo-Pacific genetic differentiation in some species appears to have resulted from Pleistocene glaciations. Life-history traits, length of larval development period, and host specificity appear can further affect the differentiation of coral barnacles across the Indian and Pacific Oceans.
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Integrative taxonomy, larval biology and functional morphology of the little known gall-forming coral endoparasite Petrarca (Thecostraca: Ascothoracida)
(2023-07-01)
Kolbasov, Gregory A.
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Savchenko, Alexandra S.
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Yu, Meng Chen
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Tsao, Yao Feng
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Ganmanee, Monthon
Petrarca is an ascothoracidan endoparasite in scleratinian dendrophyllid corals. Petrarca can stimulate coral growth, forming a gall chamber to house itself inside the coral skeleton. The diversity, molecular phylogeny and feeding ecology of Petrarca are understudied. This is the first study of Petrarca to be based on light and scanning electron microscopy to document the fine-scale external and functional morphology of its trophi and other structures. A combined molecular and morphological approach revealed at least four closely related species of Petrarca, P. goanna, P. morula, Petrarca nozawai sp. nov. and Petrarca rubus sp. nov. in Turbinaria and Astreopora corals in Asia. Carapace shape and fine morphology, ultrastructure of the antennular aesthetasc, morphological characteristics of the trophi and the shape and size of the penis rami are diagnostic characters. Several morphological characters, which are all probably synapomorphies, have been proposed to distinguish the genus Petrarca from other Ascothoracida. Mouthparts morphology of Petrarca are developed for cutting and chewing, rather than for piercing and sucking as in many other Ascothoracida. The external surface of the carapace of Petrarca is ornamented with densely packed secretory papillae used putatively for the chemical dissolution of the substrate necessary for the formation of the gall chamber.
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Seasonal growth of the purple sea urchin heliocidaris crassispina revealed by sequential fluorochrome tagging
(2021-01-01)
Suarez, Juan Diego Urriago
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Wong, Jane C.Y.
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Lui, Gilbert
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Dumont, Clement P.
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Qiu, Jian Wen
Many studies have applied fluorochrome tagging to examine the growth of animals with calcified skeletons, but most of them have used only a single tag to determine the annual growth rate. We used sequential fluorochrome tagging to study the seasonal growth of the purple sea urchin Heliocidaris crassispina in Hong Kong waters from February 2012 to February 2013. Sea urchins ranging from 18.9 to 42.7 mm in test diameter had a yearly growth from 0.6 to 13.0 mm. During that year, the sea urchins grew from 0.6 to 5.0 mm in test diameter during the first six months, and from 0.4 to 10.2 mm in test diameter in the second six months. The seasonal differences in growth were confirmed using the von Bertalanffy model. The growth was clear for young sea urchins, especially for individuals less than 5 years old, but was not evident for sea urchins older than 7 years. The seasonal differences in growth were probably related to the reproductive cycle and the seasonal differences in environmental conditions. Our empirical results provide the first evidence of seasonal changes in growth for H. crassispina, demonstrating the usefulness of sequential fluorochrome tagging in studying the growth of sea urchins in the field. We also identify the problem of low recovery of tagged individuals and provide recommendations to improve the tagging procedure.
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Use of a filamentous green alga (Chaetomorpha sp.) and microsnail (Stenothyra sp.) as feed at an early stage of intensive aquaculture promotes growth performance, artificial feed efficiency, and profitability of giant tiger prawn (Penaeus monodon)
(2020-12-01)
Tsutsui, Isao
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Aueumneoy, Dusit
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Pinphoo, Piyarat
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Thuamsuwan, Worachet
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Janeauksorn, Kittipong
With the worldwide demand for tropical penaeid prawn increasing in recent decades, more research on shrimp culture methods is needed to enhance efficiency and profitability for shrimp farmers. The objective of this study was to develop a technique to boost the productivity, feed efficiency, and profitability of the giant tiger prawn (Penaeus monodon). To accomplish this, a novel culture setup was established in which two benthic organisms, a filamentous green alga (Chaetomorpha sp.) and a microsnail (Stenothyra sp.), were propagated together with P. monodon post-larvae during an early culture stage and then offered to shrimp as supplementary live feeds in intensive aquaculture ponds. For the experiment, shrimp post-larvae (density: approximately 33 individuals m<sup>-2</sup>) were cultured in outdoor concrete ponds (9 × 9 × 1.2 m) under either control (fed only artificial feed, n = 3) or experimental (fed artificial feed and benthic organisms, n = 3) conditions until they reached marketable size (15 weeks). Apparent green algae consumption was 6.81 kg (8.4% green alga to total feed consumption), whereas microsnail consumption was 1.96 kg (2.4% microsnail to total feed consumption). Compared with the control group of giant tiger prawn, the experimental group showed significantly higher productivity (total number of shrimp produced: 118%; total shrimp production: 133%), feed efficiency (feed conversion ratio of artificial shrimp feed: 89%), and profitability (shrimp sales: 139%; balance between shrimp sales and costs: 146%), while labor and financial costs were kept minimal. These results can be explained by the enhanced growth of shrimp at the early stages of culture. The techniques developed in this study will help to advance the efficiency of intensive aquaculture operations for giant tiger prawn and also improve profitability for shrimp farmers.
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Biodiversity and host specificity of sponge-associated barnacles (Cirripedia: Thoracica) in Thailand
(2020-11-01)
Yu, Meng Chen
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Chan, Benny K.K.
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Kolbasov, Gregory A.
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Ganmanee, Monthon
We examined the diversity and host use of sponge-associated barnacles of Thailand (Andaman Sea and the Gulf of Thailand) using a combined morphological and molecular approach. Eight barnacle species (including two new species) were collected from 12 host sponges. Host-specific barnacle species includes Acasta lappa sp. nov., which exclusively inhabits the sponge Mycale sp. Acasta milkae sp. nov. was only collected from the sponge Callyspongia cf. diffusa (Ridley, 1884). Multatria filigranus (Broch, 1916) were found in the encrusting soft sponges Monanchora unguiculata (Dendy, 1922) and Clathria sp. Pyrgospongia stellula (Rosell, 1975) inhabits the sponges Spheciospongia vagabunda (Ridley, 1884). Generalist barnacle species includes Euacsta ctenodentia (Rosell, 1972), E. porata (Nilsson-Cantell, 1921), E. zuiho (Hiro, 1936), and Acasta cyathus Darwin, 1854, which inhabit a wide range of sponges with various textures.
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Timing metabolic depression: Predicting thermal stress in extreme intertidal environments
(2020-10-01)
Hui, Tin Yan
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Dong, Yun Wei
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Han, Guo Dong
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Lau, Sarah L.Y.
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Cheng, Martin C.F.
Anticipatory changes in organismal responses, triggered by reliable environmental cues for future conditions, are key to species’ persistence in temporally variable environments. Such responses were tested by measuring the physiological performance of a tropical high-shore oyster in tandem with the temporal predictability of environmental temperature. Heart rate of the oyster increased with environmental temperatures until body temperature reached ∼377C, when a substantial depression occurred (∼60%) before recovery between ∼427 and 477C, after which cardiac function collapsed. The sequential increase, depression, and recovery in cardiac performance aligned with temporal patterns in rock surface temperatures, where the risk of reaching temperatures close to the oysters’ lethal limit accelerates if the rock heats up beyond ∼377C, coinciding closely with the body temperature at which the oysters initiate metabolic depression. The increase in body temperature over a critical threshold serves as an early-warning cue to initiate anticipatory shifts in physiology and energy conservation before severe thermal stress occurs on the shore. Cross-correlating the onset of physiological mechanisms and temporal structures in environmental temperatures, therefore, reveals the potential role of reliable real-time environmental cues for future conditions in driving the evolution of anticipatory responses.

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