Anchialine Research Articles

Arthropods host intracellular chemosynthetic symbionts, too: cave study reveals an unusual form of symbiosis

Mutualisms with chemosynthetic microbes are surprisingly rare in arthropods and their relatives. Despite the evolutionary benefit assumed in retaining symbionts through growth cycles, this molting group also lacks intracellular mutualisms. The current study provides evidence of the first chemosynthetic intracellular symbiosis in Arthropoda (Crustacea), discovered in extreme anchialine cave. These unusual groundwater systems enclose a landlocked marine layer, are typified by sharp salinity and oxygen gradients and are analogous to better studied extreme environments (hydrothermal vents, methane seeps). Our investigations via electron microscopy, stable isotope analysis and an enrichment experiment reveal that shrimp harbor endosymbiotic mutualistic bacteria. As intracellular mutualisms require more morphological and genetic adaptations than their extracellular counterparts, our findings shed light on the selective pressures towards endosymbiosis in extreme ecosystems. Intracellular symbiosis may serve as an innovation for maintenance of mutualistic bacteria through molt cycles in systems that are sparsely populated with low concentrations of chemosynthetic substrates.

Molecular analyses of microbial abundance and diversity in the water column of anchialine caves in Mallorca, Spain

Water column samples from the island of Mallorca, Spain were collected from one site in Cova des Pas de Vallgornera (Vallgornera) and three sites (Llac Martel, Llac Negre, and Llac de les Delícies) in Coves del Drac (Drac). Vallgornera is located on the southern coast of Mallorca approximately 57 km southwest of Coves del Drac. Drac is Europe's most visited tourist cave, whereas Vallgornera is closed to the public. Water samples were analyzed for water chemistry using spectrophotometric methods, by quantitative PCR for estimated total abundance of microbial communities, and by length heterogeneity PCR for species richness and relative species abundance of Archaea, Bacteria, and microbial eukaryotes. Estimated total abundance was multiplied by relative species abundance to determine the absolute species abundance. All sites were compared to determine spatial distributions of the microbial communities and to determine water column physical and chemical gradients. Water quality and community structure data indicate that both Drac Delícies and Drac Negre have distinct biogeochemical gradients. These sites have communities that are similar to Vallgornera but distinct from Drac Martel, only a few hundred meters away. Drac Martel is accessible to the general public and had the most dissimilar microbial community of all the sites. Similarities among communities at sites in Drac and Vallgornera suggest that these two spatially separated systems are operating under similar ecological constraints.

Anchialine crustaceans (Crustacea: Decapoda) from Siquijor Island, Philippines

Crustaceans occurring in the anchialine ponds of Siquijor Island are reported for the first time. The crustacean fauna in anchialine habitats consist of two species of shrimps and four species of crabs. Physico-chemical parameters measured in situ during the survey show typical characteristics of tropical anchialine habitats, i.e., subsurface temperatures ranged from 25°C to 29.6°C (mean ± standard deviation, throughout = 28.26 ± 1.87°C); pH of about 7.0; low dissolved oxygen (DO) level from 4.5 mg/L to 6.63 mg/L (5.93 ± 0.87 mg/L); and higher salinity in an open anchialine pool (21.7‰, Cambakjaw) than in anchialine caves, from 5.5‰ to 13.3‰ (12.18 ± 6.21‰). Degradation of anchialine habitats were observed as a result of agriculture run-off, human utilization (e.g., bathing and laundry) and, in one case, introduction of Tilapia Oreochromis niloticus.

How might sea level change affect arthropod biodiversity in anchialine caves: a comparison of Remipedia and Atyidae taxa (Arthropoda: Altocrustacea)

Sea level change influences biodiversity of endemic cave fauna to varying degrees. In anchialine systems, a marine layer flows under less saline layers, each with differing associated fauna. We assess the role of present and historic (last glacial maximum – 18,000 years ago) distance from the ocean in determining species richness and phylogenetic diversity patterns for two groups of anchialine crustaceans: the marine-restricted Remipedia and a subset of groundwater-inhabiting atyid shrimp with greater tolerance for salinity variation. We calculated species richness and phylogenetic diversity per cave based on records of remipede and atyid diversity at 137 locations in the Yucatan Peninsula, Caribbean, Australia, and the Canary Islands. After calculating the distance of each cave’s surface opening from the past and present shoreline, we evaluated how species richness and phylogenetic diversity change with distance from the present and historic ocean. Remipede species richness and phylogenetic diversity declined rapidly with distance from the ocean. Ninety-five percent of the remipedes surveyed were located within 7 km of the present ocean and 18 km of the historic ocean. Atyid species richness and phylogenetic diversity declined more slowly with distance from the ocean than that of remipedes. Atyid shrimp were also distributed over a broader range: 95 % were located within 100 km of the present ocean and 240 km of the historic ocean. Our findings indicate that coastal geomorphology and salinity tolerance influence a clade’s distribution with respect to its distance from the ocean. We also report a possible latent response to sea level change.

Chemosynthetic ectosymbiosis reported in the predatory anchialine cave endemic, Xibalbanus tulumensis (Yager, 1987) (Remipedia)

Mutualisms between chemosynthetic microbes and invertebrates form the basis of foodwebs in dark, extreme habitats (hydrothermal vents, cold seeps) and have likely facilitated the invasion of extreme underwater caves, as well. Anchialine caves often include distinct water layers of varying concentrations of dissolved oxygen and sulfide and provide an ideal system for the discovery of chemosynthetically based systems and novel symbioses. These caves can be harsh environments for eukaryotes, but they contain gradients favorable for chemosynthetic symbiotic microbes. Here, we provide evidence of chemosynthetic ectosymbiosis in a member of the Remipedia, Xibalbanus tulumensis (Yager, 1987), through electron microscopy and stable isotope analysis. Remipedes are considered to be top predators due to anecdotal observations of feeding in the lab and field, and description of venomous apparati; but they may supplement their diet with microbes. This finding sheds light on opportunistic feeding behaviors that may have evolved to combat resource-limited environments, such as dark, underwater caves.

Diversidad regional de Amphipoda en el Mar Caribe

The order Amphipoda is one of the most diverse within Peracarids, and comprises 6950 described marine species. Amphipod research in the Caribbean Sea began in the late 1800s, but has increased significantly since 1980. In this study, we analized the amphipod biodiversity (Caprellidea, Gammaridea, Hyperiidea, and Ingolfiellidea) of the Caribbean Sea. For this, we compiled available data on species diversity of marine amphipods (data bases: WoRMS and OBIS and published species lists) into a comprehensive taxonomic list by country for the ecoregions of the Caribbean. Additionally, we analized the relative contribution of each country to regional diversity and the rate of discovery of new species. The Caribbean amphipod fauna is composed of 535 species within 236 genera and 73 families for the higher taxon. The Western Caribbean ecoregion holds the largest diversity (282 species), while the Eastern Caribbean recorded the lowest one (73). Mexico and Venezuela recorded the largest number of species with 266 and 206, respectively. Twelve countries had less than 50 species. The richest suborder is the Gammaridea with 381 species followed by the suborder Hyperiidea with 116. From the total of 535 amphipod species reported for the Caribbean region, 218 have the Caribbean as the holotype locality, and 132 are endemic (about 25% of the total). Areas of higher diversity seem to be concentrated along the Mexican Caribbean, Cuba and the Northern coast of South America (Venezuela-Colombia); however, such pattern is most likely reflecting local collection efforts and taxonomic expertise rather than actual distribution. Knowledge of amphipod species is mostly limited to shallow, near-shore waters, with little infonnation available on the deep sea fauna. Regional research priorities for this group should be focused on completing shallow water coastal inventories of species in Central America and the Greater and Lesser Antilles. In addition, sampling the deep sea ecosystems should follow along with other particular habitats such as anchialine cave systems. It is also neccessary to increase ecological research efforts, mainly in some speciose suborders, including the Caprellidea and Hyperiidea, known to exhibit high diversity in other tropical localities.

The impact of natural water column mixing on iodine and nutrient speciation in a eutrophic anchialine pond (Rogoznica Lake, Croatia)

The effect of natural water column mixing on the inorganic iodine and nutrient speciation in an intensely eutrophicated anchialine pond has been studied in late seasons of 2003 and 2004. As a result of an extremely warm and very dry European summer of 2003 this system attained isohaline and isothermal conditions in late-summer. Vertical mixing between highly reducing deep water with that in the upper layers produced intermediate redox conditions and homogeneous nutrient distribution within the water column. Nitrogen speciation additionally suggests a pronounced activity of nitrifying bacteria and/or archaea arising from an influx of the ammonium nitrogen. Meanwhile, in 2004 the water column attained nearly isohaline conditions late in November. Partial mixing of the water column resulted in downward transport of dissolved oxygen and moderate upward fluxes of nutrients into the surface layers, whereby the flux of ammonium was sufficiently high to promote nitrification. A response of the inorganic iodine to mixing of the water column was in accord with those of major constituents and nutrients. The results demonstrate that, in spite of marked changes in speciation, total inorganic iodine remained preserved within the system over each survey. Oxic to hypoxic redox conditions formed immediately after the overturn in September 2003 favoured iodate reduction, while slow mixing in November 2004 promoted iodide oxidation. In this system dominated by the sedimentary influence a degree of oxygenation of deep water seems to control the inorganic iodine inventory for the pond.

A new Psammogammarus (Amphipoda: Eriopisidae) from anchialine pools on the Exuma Cays, Bahamas.

Psammogammarus lucayensis sp. nov. is described from anchialine pools on Little Iguana Cay (Exuma Cays, Great Bahama Bank). It can be easily distinguished from the other 14 members of the genus by the combination of: 1) carpus of G2 longer than broad; 2) male G2 palm margin non-excavated, evenly convex and devoid of strong mid-palmar robust setae; 3) basis of P7 with subparallel margins; 4) armature arrangement of ventral margin of epimeral plates as 0-2-3; 5) posteroventral angle of epimeral plate III strongly produced; 6) protopod of U2 with distomedial angle armed with comb of 3-4 robust setae; 7) U3 endopod as long as exp1; and 8) telson with robust setae on tip. The generic diagnosis is amended in order to allow the precise characterization of members of Psammogammarus compared to other eriopisids.

First record of Ophioderma ensiferum (Echinodermata: Ophiuroidea) from the southeastern continental shelf of the Gulf of Mexico and from an anchialine cave

Two specimens of Ophioderma ensiferum Hendler and Miller, 1984 were collected at 2 different localities in the Yucatán Peninsula, Mexico. The first one collected at Alacranes Reef, Yucatán, a transition zone between the Gulf of Mexico and the Caribbean, and the second one in an anchialine cave located in Cozumel Island, Quintana Roo. These records expand the known distribution of the species to the southern part of the continental shelf of the Gulf of Mexico. This finding represents the first record of this ophiuroid on the continental shelf of Mexico, and also the first record of this species in an anchialine cave.

Evolution of cave Axiokebuita and Speleobregma (Scalibregmatidae, Annelida)

The evolutionary history of Axiokebuita and Speleobregma, two poorly known lineages of annelids exclusive from deep‐sea or marine caves but always from crevicular habitats, is explored here. Speleobregma lanzaroteum Bertelsen, 1986, and Axiokebuita cavernicola sp. n. are described from anchialine and marine caves of the Canary Islands using light and electron microscopy. Speleobregma lanzaroteum is previously known only from a single specimen from the water column of an anchialine cave in Lanzarote. Emended diagnosis, details on the ciliary patterns and behavioural observations are provided based on newly collected material and in situ observations. Axiokebuita cavernicola sp. n. is found in Pleistocene gravel deposits in a shallow water marine cave in Tenerife (Canary Islands). The new species is characterized by the presence of dorsal ciliary bands and short knob‐like neuropodial cirri from segment two. The porosity and permeability of the gravelly environment of A. cavernicola sp. n. are shown to be equivalent to the water column or crevices of Speleobregma and other Axiokebuita spp. Phylogenetic analyses of five gene fragments and 44 terminals using maximum‐likelihood and Bayesian methods support a derived position of A. cavernicola sp. n. within Axiokebuita and confirm a sister‐group relationship of Axiokebuita with Speleobregma with high nodal support. The Axiokebuita–Speleobregma clade is morphologically characterized by a globular pygidium with adhesive glands and ventral ungrooved ciliated palps. Our results support two independent cave colonization events, favoured by the preadaptation of the members of Axiokebuita–Speleobregma lineage to crevicular habitats.

Revision of the genus Placospongia (Porifera, Demospongiae, Hadromerida, Placospongiidae) in the Indo-West Pacific

Species of the genus Placospongia are common within the tropical Indo-West Pacific, demonstrating a wide variety of colors and either branching or encrusting growth forms. A revision of Indo-West Pacific Placospongia was undertaken based on a redescription of the holotypes of species of Placospongia from the Indian Ocean and Western Pacific and an examination of an additional 103 specimens of Placospongia ssp. collected from Indonesia (including Vosmaer and Vernhout 1902 material), Seychelles, India, Singapore and Micronesia. One mitochondrial (COI) and one nuclear (ITS) marker were subsequently used to differentiate species. All Placospongia species are characterized by selenasters and tylostyles in two size classes. The combination of microsclere diversity and morphology as well as megasclere size were shown to be informative morphometric characters, supported by molecular evidence. Live coloration and growth form is shown to be unreliable for diagnoses. The study of holotypes found that Placospongia mixta is a valid species and that two genus transfers are necessary: Geodinella anthosigma is a Placospongia and Placospongia labyrinthica is a Geodia. A new species is also described from an anchialine pool in Indonesia, Placospongia santodomingoae sp. n.; bringing the total fauna of Placospongia species in the Indo-West Pacific to five: Placospongia anthosigma, Placospongia carinata, Placospongia mixta, Placospongia melobesioides, and Placospongia santodomingoae sp. n. An identification key is given. Two additional species, possibly morphologically cryptic, have been identified by molecular markers.

Identification of echinoderms (Echinodermata) from an anchialine cave in Cozumel Island, Mexico, using DNA barcodes

The echinoderm species richness of the Aerolito de Paraiso anchialine cave, on Cozumel Island, in the Mexican Caribbean, is assessed on the basis of morphological and DNA barcoding data. We included specimens from this cave system and from different open sea areas, and employed two different approaches for species delineation based on DNA barcoding data: a 2% cox1 divergence and the general mixed Yule-coalescent (GMYC) approaches. We subsequently compared the results derived from these approaches with our morphospecies discrimination. A total of 188 cox1 sequences belonging to specimens of four echinoderm classes were examined. The 2% cox1 divergence and GMYC approaches recovered 78 and 70 putative species, respectively, 24 and 22 of which corresponded to specimens from the anchialine system. Of 26 echinoderm species identified in the cave system, seven appear to be endemic to it. Among these are Copidaster carvenicola Solís-Marín & Laguarda-Figueras, 2010, two morphologically distinctive, undescribed species belonging to Asterinides and Ophionereis and four probably cryptic undescribed species originally assigned to Amphipholis squamata (Delle Chiaje, 1839), Astropecten duplicatus Gray, 1840, Copidaster lymani (AH Clark, 1948) and Ophiothrix angulata (Say, 1825). Further research and protection of this particularly fragile ecosystem becomes urgent because construction of tourism developments is planned nearby.

Fluorescence in arthropoda informs ecological studies in anchialine crustaceans, Remipedia, and Atyidae

Autofluorescence is pervasive throughout the natural world and occurs in many animals, plants, and minerals. Fluorescent properties vary predictably over molt cycles of arthropod exoskeletons. This study examines intrinsic fluorescence in scorpions and crustaceans using novel fluorometric analyses and microscopy. Anchialine cave crustaceans, which we report here autofluoresce, are generally sparsely populated, and difficult for researchers to access. Therefore, little is known about the growth, molting, reproduction, and life history of their endemic inhabitants. Methods proposed here for measuring autofluorescence under near-ultraviolet wavelengths are valuable in informing techniques for optimal in situ observation and location of new larval forms, exuviae, spermataphores and eggs. We compare the intensity and emission breadth of fluorescent compounds extracted from California woodland scorpions (Uroctonus mordax) and California bay shrimp (Crangon franciscorum) to determine the effect of preservation duration on autofluorescent properties. Fluorescence data were obtained from anchialine cave crustaceans collected from Cenote Crustacea, Quintana Roo, Mexico and Dan’s Cave, Abaco Island, Bahamas. They exhibit peak emission wavelengths ranging from 429 nm to 515 nm and interspecific variation in emission peaks. Traits relating to emission spectra, such as breadth and intensity, may correlate with a variety of ecological parameters, such as sex, age, and reproductive state, allowing for potential field and laboratory-based applications.

A new species of smirnovipinid copepod (Copepoda: Cyclopoida: Smirnovipinidae) from an anchialine cave in Italian coastal waters, with a replacement name for the genus Ginesia Jaume and Boxshall, 1997

A new smirnovipinid copepod has been found in a shallow coastal cave located between the villages of Bagnara and Palmi on the Calabria coast. The new species belongs to genus Ginesia Jaume and Boxshall, but this name is already taken by Ginesia Fernández Yépez, a genus of freshwater fish from South America. The name Costanzoia is proposed as replacement and Costanzoia longicaudata, new combination, is the type of species by original designation. The new species Costanzoia longiseta is characterized by the extraordinary length of the apical seta on the fifth leg, which extends as far as the distal margin of third urosomal somite of the female, and by the length of seta II on the caudal rami. C. longiseta sp. nov. is very similar to shallow water hyperbenthic forms such as Cyclopinoides, Oromiina, and Smirnovipina, which also belong to family Smirnovipinidae. The discovery of C. longiseta sp. nov. confirms the presence and spread of this genus in anchialine caves of the Central Mediterranean Sea. In the cave the new species co-occurred with other cyclopoid species such as Euryte longicauda and Eupolymniphilus sp.

Density‐ and trait‐mediated top–down effects modify bottom–up control of a highly endemic tropical aquatic food web

Benthic invertebrates mediate bottom–up and top–down influences in aquatic food webs, and changes in the abundance or traits of invertebrates can alter the strength of top–down effects. Studies assessing the role of invertebrate abundance and behavior as controls on food web structure are rare at the whole ecosystem scale. Here we use a comparative approach to investigate bottom–up and top–down influences on whole anchialine pond ecosystems in coastal Hawai‘i. In these ponds, a single species of endemic atyid shrimp (Halocaridina rubra) is believed to structure epilithon communities. Many Hawaiian anchialine ponds and their endemic fauna, however, have been greatly altered by bottom–up (increased nutrient enrichment) and top–down (introduced fish predators) disturbances from human development. We present the results of a survey of dissolved nutrient concentrations, epilithon biomass and composition, and H. rubra abundance and behavior in anchialine ponds with and without invasive predatory fish along a nutrient concentration gradient on the North Kona coast of Hawai‘i. We use linear models to assess 1) the effects of nutrient loading and fish introductions on pond food web structure and 2) the role of shrimp density and behavior in effecting that change. We find evidence for bottom–up food web control, in that nutrients were associated with increased epilithon biomass, autotrophy and nutrient content as well as increased abundance and size of H. rubra. We also find evidence for top–down control, as ponds with invasive predatory fish had higher epilithon biomass, productivity, and nutrient content. Top–down effects were transmitted by both altered H. rubra abundance, which changed the biomass of epilithon, and H. rubra behavior, which changed the composition of the epilithon. Our study extends experimental findings on bottom–up and top–down control to the whole ecosystem scale and finds evidence for qualitatively different effects of trait‐ and density‐mediated change in top–down influences.

Centropages orsiniiGiesbrecht, 1889 (Copepoda, Calanoida, Centropagidae) from an anchialine cave in Vanuatu

The adult male of Centropages orsinii Giesbrecht, 1889 is redescribed based on a single specimen collected in an anchialine cave on the island of Espiritu Santo in Vanuatu. The mouthparts of this species have never previously been described and figured. Males exhibit a remarkable asymmetry in the form of the basis of leg 4. On the right leg only the basis carries three processes on its posterior surface, a unique asymmetry for the entire Calanoida. Comparison with males from other locations in the Indo-Pacific reveals some variation in the precise form of these processes. Some other species of Centropages exhibit sexually dimorphic asymmetry, with modified setation elements present on the exopod of right leg 4 only in males. It is speculated that this might be correlated with the strong asymmetry exhibited in females of some species within the genus.

Genetic characterization of the endangered and endemic anchialine squat lobster Munidopsis polymorpha from Lanzarote (Canary Islands): management implications

AbstractCabezas, P., Alda, F., Macpherson, E., and Machordom, A. 2012. Genetic characterization of the endangered and endemic anchialine squat lobster Munidopsis polymorpha from Lanzarote (Canary Islands): management implications. – ICES Journal of Marine Science, 69: 1030–1037. Anchialine species show restricted geographic ranges, high habitat specificity, and small population sizes. These factors make them particularly vulnerable to human activities, yet little is known about their ecology and evolutionary history. Munidopsis polymorpha is a decapod endemic to an anchialine cave system of the Corona lava tube in Lanzarote (Canary Islands). The present study, the first genetic survey conducted on this largely unknown species, was designed to characterize its genetic diversity, population structure and recent demographic history, using sequence data for the cytochrome oxidase I gene and eight microsatellites. A single haplotype was identified in the mitochondrial dataset. Nuclear genetic diversity was also low (average = 4.375 ± 1.685). No significant genetic structure was detected between sampling sites and years, either by analysis of molecular variance (FST = 0.006, p = 0.110) or Bayesian clustering analysis (K = 1), indicating this species should be treated as a single management unit. Neither did we find evidence for a recent bottleneck event, and estimates of effective population size were extremely low (∼50). The lack of population structure, low genetic diversity and extremely low effective population size reinforce the high degree of isolation and endemicity of this species, and, consequently, the need to implement appropriate management actions.

Ecological physiology of the anchialine shrimp Barbouria cubensis: a comparison of epigean and hypogean populations

Stygobites have morphological, ethological and physiological adaptations for their subterranean existence. Included in the physiological adaptations of hypogean organisms is a reduced metabolism with respect to related epigean organisms. Our objectives were to examine the physiological adaptations of the shrimp, Barbouria cubensis, to the anchialine environment through the use of energetics. Barbouria cubensis were collected from oxic anchialine pools in the Bahamas and from a dysoxic cave system in the Yucatan Peninsula of Mexico. Metabolism was addressed via direct measurement of oxygen consumption using microcathode oxygen electrodes as well as the activities of three primary metabolic enzymes, citrate synthase (CS), lactate dehydrogenase (LDH), and malate dehydrogenase (MDH). Additionally, protein and lipid content were determined. Respiration rates of the B. cubensis from the oxic environment were lower than reported values for other epigean crustaceans but greater than reported values for stygobitic crayfish. The specimens collected from the dysoxic environment in the Yucatan differed significantly (p < 0.01) from the specimens collected in the oxic environment in oxygen consumption, enzyme activities, and lipid concentration. Enzymes of B. cubensis from both sites were anaerobically poised with LDH activities exceeding those of CS in all organisms. But in the Yucatan B. cubensis, LDH activities exceeded MDH activities. Percent protein did not vary significantly between the two systems. Barbouria cubensis provided us with an opportunity to examine the process of cave colonization by looking at the metabolism of specimens in a dysoxic environment and those residing in oxic, surface pools.

Molecular taxonomy of Speleonectes fuchscockburni, a new pseudocryptic species of Remipedia (Crustacea) from an anchialine cave system on the Yucatán Peninsula, Quintana Roo, Mexico

A new species of Remipedia (Crustacea) is described from a recently discovered section of the anchialine cave systemCenote Crustacea, situated on the northeastern coast of the Yucatán Peninsula. Speleonectes fuchscockburni n. sp. is thesecond remipede species from the Caribbean coast of Mexico. Adult specimens are relatively small and slender, with bodylengths between 12 and 16 mm, and up to 35 trunk segments. The new species can be distinguished morphologically fromS. tulumensis by sparsely setose appendages, a ventral antennular flagellum composed of 5–6 segments, and 10–12 deeplyincised denticles of the terminal maxillary and maxillpedal claws. The status of Speleonectes fuchscockburni as a new spe-cies is validated by a comparison of cytochrome c oxidase subunit I (COI) sequences from selected remipede taxa, includ-ing Speleonectes tulumensis. The uniquely high abundance of S. tulumensis in Cenote Crustacea and the distribution of the two remipedes in this cave are discussed in relation to hydrology and cave morphology.

Two new species of harpacticoid copepods from anchialine caves in karst area of North Vietnam

Two new harpacticoid species belonging to the genera Microarthridion Lang, 1944 (Tachidiidae) and Nitocra Boeck, 1864 (Ameiridae) are recorded from underground caves in the karst area of Ninh Binh Province, North Vietnam. Microarthridion thanhi n. sp. is distinguished from congeneric species by the number of setae on the antennary exopod, the structure of leg 5 in both sexes, and the finger-like process modified from an outer distal pinnate seta of the third endopodal segment of leg 2 in the male. Nitocra vietnamensis n. sp. has the character combination of six setae on the ellipsoidal exopod of leg 5 in both sexes, the first endopodal segment of leg 1 shorter than the whole exopod, the seta/spine armature of an inner seta of P2-P4 enp-1 and four elements on P2 enp-3, and the reduction of the proximal endite to a seta on the maxillary syncoxa.