The results of this extensive sampling effort, published in the journal Zoosystematics and Evolution, describe four species new to science: one species of the genus Leiogalathea and three species of the genus Munidopsis. The collection also comprises one species of Galacantha and six species of Munidopsis in total, three of which are considered new. The use of combined morphological and molecular data confirmed the validity of the new species and documented occurrences of species previously known only from the eastern Indo-West Pacific, the southwestern Pacific, and the northeastern Pacific. For a family with more than 280 species worldwide, the southeastern Pacific had been represented by surprisingly few records, making these discoveries a significant addition to the known biodiversity of the region.

The seamounts of the Salas y Gómez and Nazca ridges are recognized as one of the regions with the highest levels of marine endemism on the planet. In recent years, sampling efforts in these systems have intensified, driven in part by their designation as a priority Ecologically or Biologically Significant Area. As a result of these expeditions, numerous new species have been described, including squat lobsters and other groups of benthic invertebrates. The technological capabilities of the ROV SuBastian, operated by the Schmidt Ocean Institute, enabled the documentation of new species and records, as well as the acquisition of high-definition imagery that provides valuable insights into ecological associations and habitat use of deep-sea benthic fauna.

The molecular analysis followed established protocols for DNA extraction, amplification, and sequencing. DNA was extracted from the fifth pereopod of each specimen using a commercial tissue kit, and integrity was verified on 2 percent agarose gels with purity assessed using the A260/280 ratio. A fragment of the mitochondrial cytochrome c oxidase subunit I gene, the standard COI barcode for animal identification, was amplified using universal primers and sequenced in both directions. Raw sequences were assembled, edited, and aligned in Geneious Prime, and only high-quality sequences without stop codons or indels were retained. Uncorrected p-genetic distances were calculated among species groups using MEGA v. 11, providing quantitative measures of divergence between the new species and their closest relatives.

Phylogenetic analyses were performed using sequences retrieved from previous publications in NCBI, which included morphologically related species to the specimens examined here. Leiogalathea was considered an outgroup for the Munidopsinae. Two approaches were used: Bayesian inference and maximum likelihood. The maximum likelihood tree was inferred using W-IQ-TREE online, with branch support assessed through ultrafast bootstrap approximation using 1,000 pseudoreplicates. Bayesian phylogenies were inferred in MrBayes v. 3.2 on XSEDE, with two runs of four chains, 100 million generations, and sampling every 10,000 generations. Convergence was verified by checking that the average standard deviation of split frequencies remained below 0.01. The resulting trees showed congruent topology, with high support for the placement of the species collected from the seamounts of the Nazca, Salas y Gómez, and Juan Fernández ridges.

The new species of Leiogalathea, named Leiogalathea rosula in reference to the rose-like color of the carapace, was recovered as part of a clade related to species discovered recently in the central and eastern Pacific. This species was previously identified in a phylogenetic study of Leiogalathea from New Caledonia, where two specimens were sequenced. Genetic divergences between L. rosula and related species ranged from 12 to 13 percent for the COI marker, well beyond the boundaries typically considered intraspecific variation. The species is morphologically related to L. anchises from Papua New Guinea and the Solomon Islands and L. creusa from French Polynesia, but can be distinguished by the length of the walking legs, which are clearly longer in the new species, and by differences in the pleonal tergites. The new species was observed in crevices and pores of volcanic bedrock partially covered by a thin sand veneer at depths between 646 and 1,130 meters.

Among the three new species of Munidopsis, Munidopsis amnos, named from the Greek word for sand in reference to the numerous small granules on the body, was collected from Guyot Baral at the intersection of the Nazca and Salas y Gómez ridges at 705 meters. The species is characterized by numerous granules and tubercles on the carapace and pereopods, unarmed lateral margins of the carapace, immovable eyes with globular corneas, and the absence of epipods on the pereopods. The closest species is Munidopsis dispar from the seamounts of the Mariana Trench and Carolina Plate, later recorded in Hawaii and Johnston Atoll. The genetic divergence between M. dispar and M. amnos is 9 percent for COI. The new species is also morphologically and genetically close to M. sonne from the western Pacific and M. granosicorium from California, but both of those species possess epipods on the first three pereopods, whereas they are absent in the new species.

Munidopsis molinai, dedicated to Abate G.I. Molina, who published the first contribution to Chilean carcinology in 1782, was recorded at the intersection of the Nazca and Salas y Gómez ridges within the Nazca-Desventuradas Marine Park between 687 and 748 meters. The species belongs to a group with well-exposed corneas, an eyespine at the dorsomedian end of the eyestalk, and first pereopods usually twice or more the carapace length. The closest relatives are M. scabra, from Oregon to Peru, and M. tanneri, from Panama to Chile, but the new species can be distinguished by the presence of epipods on the first pereopods, a rostrum that is 1.7 to 2.0 times as long as wide rather than approximately 2.5 times, less prominent granules on the dorsal surface of the carapace, and the absence of numerous spines on the extensor margins of the walking legs. The analyses of the new species together with specimens identified as M. scabra from the northeastern Pacific confirmed the existence of hidden diversity and a species complex, as already suggested by previous authors.

Munidopsis oryza, named from the Greek word for rice in reference to the granules of the body, was described from a single female specimen collected at 2,092 meters on an unnamed seamount in the Nazca Ridge. The species belongs to a group with epipods on the first three pereopods, unarmed and immovable eyes, and a telson with seven to eight plates. The closest species is M. hawaii, from a seamount off Hawaii, and the two can be distinguished by the rostrum, which is 2.8 times as long as broad and directed upward in the new species compared with 1.6 times and horizontal in M. hawaii, by the size of the dorsolateral process of the antennular article, and by the proportions of the walking legs. The genetic divergence between the two species is 5.2 percent for COI. The new species was recorded solitarily in a vertical position on volcanic bedrock microhabitats characterized by a granular substrate with high rugosity and small vesicles or cavities that form sand-filled pockets.

Beyond the new species, the expeditions documented significant range extensions. Munidopsis tiburon, previously known only from off Oregon and in the Monterey Bay Canyon, was recorded at Dragon Back seamount in the Nazca Ridge at 2,253 meters, extending its distribution to the southeastern Pacific. Munidopsis comarge, originally described from southeastern and southwestern Australia and New Zealand and later collected in southern Java and American Samoa, was found to be the most abundant species across the studied seamounts. This species occurs in groups on coral colonies from different families, including Anthothelidae, Madreporidae, and Muriceidae, as well as on solitary hard corals, but was also observed solitarily on volcanic rock within crevices, indicating that association with habitat-forming organisms is facultative rather than obligate. Coloration appears to vary according to the host coral, with a paler form associated with white corals and an orange form associated with darker-colored corals. The species was recorded between 509 and 817 meters depth, at temperatures ranging from 4.9 to 5.9 degrees Celsius and under oxygen conditions above 2 milliliters per liter.

These findings suggest a closer relation of the fauna of the central and western Pacific with the fauna of the Nazca and Salas y Gómez area, as other authors have observed in fish and echinoderms. This would confirm the extreme faunal isolation between the eastern Pacific and the central-western Pacific, due to the great distance between both basins, approximately 5,000 to 8,000 kilometers, considered the world’s most effective barrier to larval dispersal. With the exception of Galacantha rostrata, none of the species found in the seamounts of the Nazca and Salas y Gómez ridges had been recorded on the continental shelf and slope of Chilean waters east of the Juan Fernández Archipelago. Three species are also found in the Indian Ocean and western Pacific, and M. tiburon is also found in California waters. Overall, the discovery of new species and the extension of distributional ranges for deep-sea taxa such as Munidopsidae are critical for advancing the understanding of biodiversity patterns in the southeastern Pacific. This knowledge is particularly relevant in the context of Areas Beyond National Jurisdiction, where baseline data remain scarce but are essential to inform conservation and management efforts under the framework of the BBNJ Agreement.

Subject of Research: Taxonomy and biogeography of deep-sea squat lobsters from Southeast Pacific seamounts

Article Title: Squat lobsters of the family Munidopsidae Ortmann, 1898 ( Decapoda , Galatheoidea ) from the seamounts of the Southeast Pacific Ocean ridges

Article References: Gallardo-Salamanca, M. D. L. A., Rodríguez-Flores, P. C., & Macpherson, E. (2026). Squat lobsters of the family Munidopsidae Ortmann, 1898 (Decapoda, Galatheoidea) from the seamounts of the Southeast Pacific Ocean ridges. Zoosystematics and Evolution, 102(4), 949-972. https://doi.org/10.3897/zse.102.196673

Image Credits: AI Generated

DOI: 10.3897/zse.102.196673

Keywords: squat lobsters, Munidopsidae, seamounts, Nazca Ridge, Salas y Gómez Ridge, new species, deep-sea biodiversity, Schmidt Ocean Institute, Squat, lobsters, family, Ortmann

Squat lobsters are not lobsters in the culinary sense. They are decapod crustaceans of the infraorder Anomura, the same group that includes hermit crabs and king crabs, and most species are small, laterally compressed animals that shelter in crevices or perch on hard substrates, waving their elongated claws in the current to feed. The family Munidopsidae, to which the new species belongs, is dominated by deep-water lineages, many of which are associated with seamounts, canyons, and other hard-bottom habitats far below the reach of sunlight-driven photosynthesis. Because these environments are geographically isolated from continental shelves and exhibit complex topographic and oceanographic patterns, they often harbor distinctive benthic communities, including endemic species found nowhere else.

The specimens that led to the new species were collected in late March 2024, during FORV Sagar Sampada cruise 404, using a chain bag dredge deployed at a station located at 8.54 degrees North, 73.26 degrees East, on what the team designated seamount 4 off Minicoy. Four individuals were recovered: an ovigerous female designated as the holotype, one male and two females designated as paratypes. All four came from the same dredge haul at 360 meters depth, collected by R. Ravinesh and his shipboard colleagues. The animals are small even by squat lobster standards, with postorbital carapace lengths ranging from about 4.5 to 5.2 millimeters and carapace widths between 3.7 and 4.4 millimeters.

Back in the laboratory, the team cleaned, photographed, and examined the specimens under a Leica M80 stereo-zoom microscope fitted with a high-definition camera, taking measurements with calibrated imaging software. The morphological analysis followed the descriptive terminology established in a 2019 revision of the genus by Rodríguez-Flores, Macpherson, and Machordom, which had itself described fifteen new species and remains the taxonomic backbone for Leiogalathea. Every appendage was scrutinized: the spination of the third maxillipeds, the proportions of the first pereopods, the armature of the walking legs, the shape of the rostrum, and the pattern of ridges sculpting the carapace, the armored plate that covers the head and thorax.

That ridge pattern proved decisive. Leiogalathea samudragiri shares with three of its closest relatives, L. achates, L. evander, and L. laevirostris, an unarmed hepatic margin on the carapace, a feature that initially groups them together. But the new species stands apart in two consistent characters: its mesogastric and mid-transverse ridges on the carapace are uninterrupted, running continuously across the midline, and the posterior half of the carapace bears six transverse ridges. In the three related species, the mid-transverse ridge is interrupted medially or submedially, and only four or five ridges follow it. Additional differences reinforce the split. Unlike L. achates, the new species lacks a spine on the posterior branchial margin and has subequal rather than unequal distal spines on the second antennal article. Unlike L. evander, it carries three well-developed rostral teeth rather than four to six rudimentary ones, and its abdominal tergite 3 bears a single elevated ridge rather than two. Unlike L. laevirostris, the basal antennular article is unarmed at its distomesial corner, and the mesial margin of the first pereopod’s carpus carries one spine rather than three.

The detailed anatomy is a study in miniature engineering. The rostrum, the pointed projection between the eyes, is slightly downturned and flattened dorsally, about 1.5 times as long as broad, with serrated lateral margins bearing three small teeth and three progressively smaller rudimentary teeth. The first pereopods, the elongated claws that give squat lobsters their characteristic silhouette, extend to nearly three times the carapace length and are clothed in uniramous stiff setae, with the merus segment alone slightly exceeding the carapace length and bristling with strong spines arranged along its mesial, dorsal, lateral, and ventral surfaces. The walking legs are moderately slender and laterally compressed, with propodi more than five times as long as broad and dactyli armed with rows of small, proximally diminishing teeth, each tipped with a slender movable spinule. The third maxilliped’s ischium terminates in a strong spine on its flexor margin and carries a crista dentata of twenty-two corneous denticles.

Even the coloration, recorded from freshly collected material, is distinctive and unexpectedly vivid for an animal living in near darkness. The rostrum and the anterior two-thirds of the carapace are bright orange, with light yellow patches on the posterior gastric region; the posterior carapace and anterior abdominal segments are pale orange, and the pereopods are bright orange marked with white patches. The species name itself is a nod to its habitat, combining the Sanskrit words samudra, meaning ocean, and giri, meaning mountain, a direct reference to the seamount where the animals were found. The holotype female was ovigerous, carrying eggs, which suggests the population was reproductively active at the time of collection.

The broader context makes the find more significant than a single addition to a checklist. The genus Leiogathea, established by Keiji Baba in 1969, is dominated by the Pacific Ocean, which hosts fourteen of its species, while the Atlantic and Indian Oceans had only two each before this description. The munidopsid fauna of the Northern Indian Ocean, the authors note, remains relatively unexplored compared with neighboring regions. A previous expedition had already yielded an unresolved Leiogalathea specimen from the Andaman Sea, reported as Leiogalathea sp. because it was damaged, hinting that the region harbors more diversity than the formal record reflects. The authors also point out that overlapping morphological characters among congeners probably indicate the existence of pseudocryptic species within the genus, externally near-identical lineages that only careful comparison of fine structural details, or genetic analysis, can separate.

The expedition itself is part of a larger national effort. The samples were gathered under India’s Deep Ocean Mission, specifically the Samudrayaan program, coordinated through the Ministry of Earth Sciences, with CMLRE in Kochi leading the faunal exploration aboard the research vessel Sagar Sampada. Seamounts have been recognized as ecological hotspots since faunal explorations began in the 1940s, yet only a handful of Indian Ocean seamounts have ever been surveyed, leaving vast tracts of undersea topography biologically uncharted. Voucher specimens of the new species, registered under the catalog numbers IO/SS/ANO/00195 through 00197, are deposited in the Bhavasagara Referral Centre at CMLRE, which serves as the regional node of the Ocean Biodiversity Information System for the Indian Ocean, and the associated occurrence data will be made publicly available through the OBIS portal.

For now, Leiogalathea samudragiri is known only from its type locality in the Lakshadweep Sea off Kerala, at 360 meters depth, a single seamount station in an ocean basin where deep-water sampling effort remains sparse. Whether the species is a narrow endemic restricted to one undersea mountain, as many seamount-associated invertebrates appear to be, or simply under-collected across a wider range, will only be resolved by further expeditions. What the discovery does demonstrate is that even a single dredge haul, examined with the right taxonomic expertise, can reveal a lineage new to science in one of the most heavily trafficked yet least explored marine regions on Earth, and that the census of life on the Indian Ocean’s seamounts has barely begun.

Subject of Research: Taxonomic description of a new deep-sea squat lobster species from an Arabian Sea seamount

Article Title: A new deep-sea munidopsid squat lobster of the genus Leiogalathea Baba, 1969 (Decapoda: Anomura) from the southeastern Arabian Sea, India

Article References: Tiwari, S., Padate, V. P., & Cubelio, S. S. (2026). A new deep-sea munidopsid squat lobster of the genus Leiogalathea Baba, 1969 (Decapoda: Anomura) from the southeastern Arabian Sea, India. Discover Oceans, 3(1), Article 6. https://doi.org/10.1007/s44289-026-00117-5

Image Credits: AI Generated

DOI: 10.1007/s44289-026-00117-5

Keywords: squat lobster, Leiogalathea samudragiri, seamount, Arabian Sea, deep sea, taxonomy, new species, Munidopsidae, Decapoda, Anomura, Deep Ocean Mission, marine biodiversity