The research, published in the journal Coral Reefs, was led by Sergio D. Guendulain-García of the National Autonomous University of Mexico together with colleagues from several Mexican institutions. The team set out to map what they call the morphofunctional space of coral species in the Eastern Tropical Pacific, a region stretching from the Gulf of California to northern Peru where reef-building corals endure some of the most volatile ocean conditions on Earth. El Niño events, seasonal swings, and upwelling drive constant fluctuations in temperature, salinity, pH, and nutrient availability, and in response the region hosts comparatively few coral genera, dominated by Porites, Pavona, Psammocora, and above all Pocillopora, the branching corals that form the backbone of most Eastern Pacific reef frameworks and feature prominently in restoration projects.

That dominance of a single genus posed both a scientific puzzle and an unexpected opportunity. Pocillopora colonies are notoriously plastic, shifting their growth forms in response to their environment, and different species within the genus look maddeningly similar. This overlap has long blurred the connection between colony shape and species identity, making it difficult to quantify what each species contributes to reef function. To cut through the ambiguity, the researchers assembled a dataset of 206 three-dimensional models spanning nine coral species, drawing on curated skeletal collections held at Universidad del Mar in Oaxaca and the Autonomous University of Baja California Sur, along with living colonies from a coral restoration site in Bahía de la Paz run by the local NGO Efecto Arena. The specimens ranged from 3.2 to 54.4 centimeters in maximum diameter, capturing the latitudinal, environmental, and depth gradients across which these species occur.

The digitization itself combined two complementary techniques. Skeletons from the museum collections were scanned with a structured light scanner, the EinScan H2, which resolves surface details to within a tenth of a millimeter; each colony was rotated through eight angular positions on a turntable to build a complete 360-degree model. Living colonies were captured underwater using structure-from-motion photogrammetry, with photographers from an Olympus TG6 camera shooting overlapping photo sets at 50 centimeters for overall shape and 15 centimeters for fine branch detail, then processed in Agisoft Metashape and cleaned, oriented, and reconstructed with standard mesh-repair tools. Previous work by the same group has shown that models from either method can be used interchangeably for colony-level analysis, which gave the team confidence in mixing sources.

From each 3D model, the researchers extracted six morphofunctional traits previously developed for quantifying coral shape. Sphericity and convexity together describe how compact a colony’s volume is, tracing a gradient from solid, boulder-like massive forms to open, airy branching ones; less compact shapes generally offer more habitat and refuge space. Packing and rugosity capture surface complexity, from the smooth faces of encrusting corals to the convoluted tangle of branching species, a property linked to biomass per unit skeleton, light harvesting, and the abundance of microhabitats. Finally, the first moments of area and volume describe top-heaviness, the vertical distribution of a colony’s mass, which influences how colonies compete for light and space, how firmly they anchor the reef framework, and how they withstand physical disturbance. The team also measured shelter capacity, the void space a colony creates beneath and among its branches, and weighed skeletons to estimate calcium carbonate content.

When the trait data were fed into a principal component analysis, the results were emphatic. The analysis recovered 86.5 percent of the total morphofunctional variation, with the first component alone accounting for 60.2 percent, driven overwhelmingly by packing and sphericity. The plots revealed a clean separation between massive corals such as Pavona and Porites and the branching Pocillopora, with only marginal overlap. Perhaps more intriguingly, the Eastern Pacific pattern differed from what studies in the Caribbean and Indo-Pacific have found, where convexity tends to dominate. Lacking the tabular morphologies that create large inter-colonial spaces elsewhere, Eastern Pacific variation appears driven mainly by how biomass is distributed across the colony surface through the dense arrangement of micro-refugia created by branching Pocillopora.

The discriminant analysis then delivered the study’s pivotal insight. While massive and branching groups were statistically distinct, the species within each group were not: Mahalanobis distances revealed no significant differences among the branching Pocillopora species, nor among the massive species, even though all species classifications were significant as groups overall. In other words, the formally recognized Pocillopora species of the Eastern Tropical Pacific occupy almost identical morphofunctional space. This finding echoes genetic studies that have struggled to separate Pocillopora morphospecies, and it carries a consoling ecological implication: if one species declines, others may fill its structural role, a redundancy that could buffer the region’s reefs against the loss of individual taxa.

It is precisely this redundancy that made the toolkit possible. Because all Pocillopora species share essentially the same shape-function relationships, the team pooled them and fit mathematical models relating two easy field measurements, maximum colony diameter and projected planar area, to the harder-to-obtain three-dimensional traits. Power models best described most relationships, with a linear fit for surface area against projected area, and every model explained more than 80 percent of the variance. Practitioners can now measure a colony’s diameter with a tape measure, or derive its planar area from aerial orthomosaics, and immediately estimate its surface area, volume, shelter volume, calcium carbonate content, and moments of area and volume, translating those numbers into assessments of habitat provision, structural complexity, carbonate contribution, and restoration performance.

The practical implications extend well beyond academic curiosity. Most coral restoration programs still gauge success by counting transplants and tracking survival and growth, metrics that quantify effort but say little about how colonies actually function on the reef. Three-dimensional photogrammetry offers a richer picture but remains costly and time-consuming for many groups. By eliminating the need for specialized scanning equipment and avoiding the handling of living colonies, the predictive equations remove the main barriers to routine functional monitoring across large restoration programs in the Eastern Pacific, where Pocillopora is the workhorse genus of most interventions.

The authors are careful to note the limits of their approach. Colony-scale metrics should not be assumed to scale linearly to whole reefscapes, because neighboring colonies interact in ways that generate emergent properties, from branch interlocking and fused shelter spaces to collective refuge generation and altered local turbulence, that individual models cannot capture. Dense aggregations of Pocillopora frequently form structurally interconnected patches across the region, and future research, the team argues, should incorporate colony interactions and spatial arrangement into multi-scale 3D frameworks linking individual morphology to ecosystem-level function. Even so, the toolkit marks a meaningful step toward making functional assessment of coral reefs as routine as measuring coral cover, offering scientists and restoration practitioners a faster, cheaper, and less invasive window into the hidden architecture of reef life.

Subject of Research: Three-dimensional morphometric analysis and predictive trait modeling of Eastern Tropical Pacific reef corals

Article Title: Tropical Eastern Pacific coral morphometrics: a toolkit for coral studies

Article References: Tropical Eastern Pacific coral morphometrics: a toolkit for coral studies. (n.d.). https://doi.org/10.1007/s00338-026-02939-3

Image Credits: AI Generated

DOI: 10.1007/s00338-026-02939-3

Keywords: coral reefs, Pocillopora, Eastern Tropical Pacific, morphometrics, 3D photogrammetry, morphofunctional traits, structural complexity, coral restoration, functional redundancy, habitat provision, calcium carbonate, reef ecology

The three-spot gourami is easy to recognize. Its laterally compressed body carries two distinct black spots along the flanks, adults display faint vertical stripes, and its dorsal fin, shorter than the anal fin, bears both spines and soft rays. Individuals typically reach about ten centimeters in length. The species thrives in ponds, swamps, canals, and floodplains throughout the Mekong River basin, where submerged vegetation offers both shelter and feeding grounds in water temperatures between 24 and 30 degrees Celsius. Beyond its role in local food webs, where it serves as prey for larger carnivores such as the snakehead Channa striata and the striped catfish Pangasianodon hypophthalmus, the gourami is prized in the ornamental fish trade, making its biology relevant to both ecologists and aquaculturists.

To build their dataset, the researchers collected 32 specimens from Tra Su in March 2025 using hand nets with a 2.5 centimeter mesh, preserving the fish in 4 percent formalin before laboratory analysis. In the lab, they recorded total length, standard length, body weight, eye diameter, interorbital distance, body depth, head length, and mouth width, along with fin ray counts for the pectoral, pelvic, dorsal, anal, and caudal fins. The fish sampled ranged from 6.70 to 9.00 centimeters in total length, averaging 7.76 centimeters, and weighed between 4.10 and 10.30 grams with a mean of 6.50 grams. This meticulous measurement campaign provides a baseline against which future populations can be compared, a critical tool in a region where freshwater ecosystems are under mounting pressure.

The meristic counts revealed a remarkably stable anatomical blueprint. Caudal fins carried 14 to 16 rays, with 16 the most frequent. Each pelvic fin consistently bore a single ray, while the pectoral fins consisted of two elongated filaments positioned anterior to the anal fin. Dorsal fins held 5 to 7 spines, most commonly 7, and 6 to 10 soft rays, typically 8 or 9. The anal fin showed a fixed count of 11 spines with 30 to 35 soft rays, most often 32 or 33, and pectoral fins carried 8 to 12 rays, usually 9 or 10. These figures align closely with earlier descriptions from the Mekong Delta and Cambodia, reinforcing the view that the species maintains morphological stability across varied environmental conditions and strengthening the taxonomic foundation for identifying T. trichopterus in the region.

Growth analysis delivered one of the study’s most consequential findings. Using the classic length-weight relationship, in which body weight scales with total length raised to an exponent b, the team estimated a growth coefficient of 2.98 plus or minus 0.16, statistically indistinguishable from 3, the hallmark of isometric growth. In practical terms, the fish gains weight in proportion to its length, reflecting balanced somatic development. The coefficient of determination exceeded 0.93, meaning more than 93 percent of the variation in body weight was explained by length alone. Comparable near-isometric patterns have been reported for the species in the Ogan Ilir peat swamp of South Sumatra, Indonesia, and for other Mekong Delta fishes such as the tank goby Glossogobius giuris, though the exponent is known to shift with environmental conditions.

That flexibility was underscored by aquaculture experiments elsewhere, in which probiotic-supplemented diets containing Bacillus subtilis and B. circulans pushed the growth exponent to 3.28, indicating positive allometric growth, while control groups ranged from 2.41 to 2.93. The Tra Su result, sitting almost exactly at isometry, suggests the wetland provides a stable and adequate natural food supply for the gourami, a positive indicator of habitat quality. The regression equation derived from the study can now serve as a practical tool for estimating biomass, monitoring growth, and managing resources in both wild and cultured populations, reinforcing the ecological case for continued conservation of the Tra Su landscape.

The study’s anatomical detective work focused on the digestive system, where the evidence pointed firmly toward an omnivorous lifestyle. The gourami possesses a terminal, slightly upward-facing mouth with a subtly protruding lower jaw, an arrangement suited to surface feeding. Its jaws are lined with numerous small, conical teeth arranged in continuous rows, an adaptation for grasping and scraping soft-bodied prey rather than tearing flesh. The tongue is elongated, flattened, and studded with a row of small V-shaped spots, a region rich in taste receptors that supports sophisticated orosensory food testing. The gill arches carry thin, elongated, closely spaced rakers, a fine filtration apparatus adapted for capturing plankton, in sharp contrast to the shorter, thicker rakers of sympatric predatory gobies.

Further down the tract, the anatomy tells the same story. A short esophagus leads to a sac-like stomach with thickened walls, followed by an extended, tightly coiled intestine ranging from 9.0 to 26.0 centimeters, averaging 17.04 centimeters, a length adapted to processing a mixed diet of plant and animal material. The relative gut length, the ratio of gut length to total body length, averaged 2.19 plus or minus 0.09, squarely within the 1 to 3 range that defines omnivores. This finding revises earlier classifications that labeled the species carnivorous, and it contrasts instructively with relatives: the congeneric Trichogaster fasciata shows a much higher relative gut length of 5.12, consistent with herbivory, while carnivorous Mekong gobies possess markedly shorter intestines.

Stomach content analysis confirmed the omnivorous verdict and revealed a striking dietary hierarchy. Fish eggs appeared in 45 percent of gut samples and dominated by biovolume at 38.02 percent, followed by zooplankton at 33.99 percent and Chlorophyta green algae at 16.98 percent. Euglenophyta, Cyanophyta, and Bacillariophyta contributed smaller shares between 1.37 and 6.15 percent. A modified Costello diagram, plotting frequency of occurrence against volumetric contribution, identified fish eggs as the primary food resource, with zooplankton and Chlorophyta serving as important supplemental items and the remaining algal groups likely ingested incidentally. The pattern reveals an opportunistic omnivore with a pronounced preference for high-protein prey, consistent with reports from Indian coastal wetlands where the species consumed detritus, algae, zooplankton, and even plastic debris.

The implications ripple outward from Tra Su. Freshwater habitats cover only 0.1 percent of the Earth’s water surface yet harbor roughly 40 percent of known fish species, and freshwater fishes rank as the second most threatened vertebrate group after amphibians, with about 20 percent of species projected to face extinction within the next 25 to 50 years. Tra Su itself presents harsh conditions, with water pH as low as 2.75, dissolved oxygen frequently below 5 milligrams per liter, and elevated ammonium and total iron concentrations, making the gourami’s success there a testament to its adaptability. By documenting stable morphology, isometric growth, and a flexible omnivorous diet, the study establishes the foundational knowledge needed for taxonomic work, ecological monitoring, artificial breeding programs, and sustainable fisheries management. The authors point toward ecological aquaculture as a promising avenue, urging further research into reproductive biology, population genetics, and adaptive capacity under culture conditions, work that could help safeguard both the species and the livelihoods that depend on the Mekong Delta’s vanishing wetlands.

Subject of Research: Morphometrics, growth pattern, and feeding ecology of the three-spot gourami Trichopodus trichopterus in the Tra Su wetlands of the Vietnamese Mekong Delta

Article Title: First report on morphometrics, length–weight relationship, feeding habit, and diet composition of Trichopodus trichopterus from Tra Su, An Giang, Vietnam

Article References: Nguyen, V. Q., Van Ly, V., Vo, L. T. T., Nguyen, H. T. K., & Dinh, Q. M. (2026). First report on morphometrics, length–weight relationship, feeding habit, and diet composition of Trichopodus trichopterus from Tra Su, An Giang, Vietnam. Discover Animals, 3(1), Article 87. https://doi.org/10.1007/s44338-025-00130-6

Image Credits: AI Generated

DOI: 10.1007/s44338-025-00130-6

Keywords: Trichopodus trichopterus, three-spot gourami, Mekong Delta, Tra Su, morphometrics, length-weight relationship, isometric growth, omnivorous diet, fish eggs, zooplankton, freshwater conservation, Vietnam