Two new marine cyclopinids (Crustacea: Copepoda: Cyclopoida) from interstitial habitats in Korea

Marine cyclopoids, and especially cyclopinids, are poorly studied because their diversity is highest in marginal habitats, such as intertidal interstitial and anchialine caves, or in highly inaccessible abyssal and hadal depths. Two new cyclopinids are described here, both from two different sandy beaches in Korea. Among four species currently recognized in the genus, Heterocyclopina koreaensis sp. nov. is most closely related to H. vietnamensis Pleşa, 1969 from similar habitats in Vietnam. Koreacyclopina wellsi gen. et sp. nov. shares its sexually dimorphic third exopodal segment of the second leg with the Antarctic genus Pseudocyclopina Lang, 1946, but differs from all six known species by numerous features, some of which are observed for the first time within cyclopinids. Both Korean species belong to the family Hemicyclopinidae, but the monophyly of this group has not yet been demonstrated.

Monsters in the dark: systematics and biogeography of the stygobitic genus Godzillius (Crustacea: Remipedia) from the Lucayan Archipelago

Remipedia is a stygobitic group commonly associated with coastal anchialine caves. This class consists of 12 genera, ten of which are found within the Lucayan Archipelago. Herein, we describe a new species within the genus Godzillius from Conch Sound Blue Hole, North Andros Island, Bahamas. Godzillius louriei sp. nov. is the third known remipede observed from a subseafloor marine cave, and the first from the Godzilliidae. Remipedes dwell within notoriously difficult to access cave habitats and thus integrative and comprehensive systematic studies at family or genus level are often absent in the literature. In this study, all species of Godzillius are compared using morphological and molecular approaches. Specifically, the feeding appendages of G. louriei sp. nov., G. fuchsi Gonzalez, Singpiel & Schlagner, 2013 and G. robustus Schram, Yager & Emerson, 1986 were examined using scanning electron microscopy (SEM). Species of Godzillius are identified based on the spines of maxilla 1 segment 4 and by the denticles on the lacinia mobilis of the left mandible. A molecular phylogeny using the mitochondrial 16S rRNA and nuclear histone 3 genes recovered G. louriei sp. nov. within the Godzillius clade and 16S genetic distances revealed a 13–15% difference between species of Godzillius.

Morphological convergence and adaptation in cave and pelagic scale worms (Polynoidae, Annelida)

Across Annelida, accessing the water column drives morphological and lifestyle modifications—yet in the primarily “benthic” scale worms, the ecological significance of swimming has largely been ignored. We investigated genetic, morphological and behavioural adaptations associated with swimming across Polynoidae, using mitogenomics and comparative methods. Mitochondrial genomes from cave and pelagic polynoids were highly similar, with non-significant rearrangements only present in cave Gesiella. Gene orders of the new mitogenomes were highly similar to shallow water species, suggestive of an underlying polynoid ground pattern. Being the first phylogenetic analyses to include the holopelagic Drieschia, we recovered this species nested among shallow water terminals, suggesting a shallow water ancestry. Based on these results, our phylogenetic reconstructions showed that swimming evolved independently three times in Polynoidae, involving convergent adaptations in morphology and motility patterns across the deep sea (Branchipolynoe), midwater (Drieschia) and anchialine caves (Pelagomacellicephala and Gesiella). Phylogenetic generalized least-squares (PGLS) analyses showed that holopelagic and anchialine cave species exhibit hypertrophy of the dorsal cirri, yet, these morphological modifications are achieved along different evolutionary pathways, i.e., elongation of the cirrophore versus style. Together, these findings suggest that a water column lifestyle elicits similar morphological adaptations, favouring bodies designed for drifting and sensing.

Microeukaryotic and Prokaryotic Diversity of Anchialine Caves from Eastern Adriatic Sea Islands

Anchialine ecosystems in the eastern Adriatic Sea are diverse both morphologically and biologically. In this study, for the first time, we explored the microeukaryotic and prokaryotic community of anchialine caves in the Mediterranean region using high-throughput sequencing. Four anchialine caves located on nearby islands with a well-pronounced salinity gradient were sampled at the surface freshwater area, halocline area, and seawater area. Sequencing revealed a surprisingly wide diversity of the microeukaryotic and prokaryotic community with the relative abundance of major phyla differing within the salinity gradient and between the caves. Interestingly, microeukaryotic and prokaryotic communities clustered into four groups based on location, pointing out that sampled anchialine caves have different microbial community patterns and high microbial endemism. Our results indicate that even with the halocline acting as a selecting barrier, the salinity is not the only community structuring factor. Despite the short geographical distance, the isolation of anchialine caves facilitated high microbial community adaptation and endemism. Our study suggests that anchialine caves represent reservoirs of new biodiversity, maintaining unique and complex microbial diversity influenced by biotic interactions and abiotic environmental conditions.

New arietellid copepods (Calanoida, Arietellidae) from anchialine caves in the Eastern Adriatic Sea

Two new species of calanoid copepods are described; Metacalanus adriaticus sp. nov. from an anchialine cave on Vis Island, and Paramisophria tvrtkovici sp. nov. from Orljak Cave, located in the lower part of River Krka estuary, near the town of Šibenik (Croatia). This is the first report of arietellid copepods found in any anchialine cave along the coast of the Adriatic Sea. In M. adriaticus sp. nov. the antennules are asymmetrical in both sexes (the female left antennule is 18-segmented, right 20-segmented; male left 16-segmented and right 20-segmented); the uniramous fifth legs of the female are 2-segmented; the terminal segment of the fifth leg in both sexes is the longest; and in the male the fifth leg exopod is 2-segmented. In P. tvrtkovici sp. nov. the antennules of both sexes are asymmetrical with the left antennule longer than the right, the female antennule is 21-segmented on both sides; the male left antennule is 19-segmented, the right 21-segmented; the armature of the terminal exopod segment of leg 1 is II, 2 ,2; the male fifth legs have a rudimentary endopod on the left leg, the third exopodal segment is smallest and bears three unequal processes on its outer margin, and the terminal spine is completely separated from the segment. On the right leg the third segment carries two short, unequal processes on its outer distal margin, as well as a long sigmoidal spine which is fused to the segment. It is inferred that, after the last glaciation, these new Arietellids moved out from their southern Adriatic refuge, colonizing first the anchialine habitats of the outer eastern Adriatic islands and then spreading along the coast.

Theosbaena loko sp. n. a new stygobiotic microshrimp (Thermosbaenacea: Halosbaenidae) from southern Thailand

Thermosbaenaceans are subterranean crustaceans, widespread and occur in freshwater, oligohaline or anchialine caves or thermal springs. Currently, four families, seven genera,and 45 species are recognised worldwide. During our studies of the isolated karst, Tham Loko (Loko Cave) in Khao Chiason District, Phatthalung Province, we found an undescribed thermosbanacean species in the genus Theosbaena. Theosbaena is the only genus reported from freshwater in the Oriental Region. Previously, there were only two known species, Theosbaena cambodjiana Cals & Boutin, 1985 from Kampot Province, southern Cambodia and Khon Kaen, Thailand and T. kiatwongchai Rogers & Sanoamuang, 2016 discovered in a cave of Takhli District, Nakhon Sawan, central Thailand. Our new species is the third species recorded in the Oriental Region. Theosbaena loko sp. n. differs from its congeners by having a telson 1.8x longer than its breadth, maxilla 1 palp distal segment 4x longer than the proximal palpomere and the maxillopodal exopod twice as long as its basal width. This microshrimp is the third described species of the genus. A key to the species is given and suggestions for the conservation status of the new species are discussed.

A new species of the cave-fish genus Lucifuga (Ophidiiformes, Bythitidae), from eastern Cuba

Recently, a barcoding study and a molecular phylogenetic analysis of the Cuban species of the cave-fish genus Lucifuga Poey, 1858 revealed the existence of different evolutionary lineages that were previously unknown or passed unnoticed by morphological scrutiny (i.e., cryptic candidate species). In the present study, Lucifuga gibarensis is described as a new species restricted to anchialine caves in the northeastern karst region of the main island. The species was earlier described as a variety of Lucifuga dentata, but since the name was introduced as a variety after 1960, it is deemed to be infrasubspecific and unavailable according to the International Code of Zoological Nomenclature Art. 15.2. The new species differs from L. dentata by pigmented eyes vs. eyes absent and lack of palatine teeth vs. present. Lucifuga gibarensis seems to be most similar to the Bahamian species L. lucayana by showing pigmented eyes, 13 or 14 precaudal vertebrae and ten caudal fin rays. However, differs from it by a larger size of the pigmented eye (1.1–1.9 vs. 0.9–1.0% SL) and number of posterior lateral line neuromasts (30–33 vs. 34–35).

Anchialine cave-dwelling sponge fauna (Porifera) from La Quebrada, Mexico, with the description of the first Mexican stygobiont sponges

Porifera has been relatively well studied from underwater caves worldwide. However, sponges in Mexico are only known from two anchialine caves: La Quebrada and El Aerolito, both in Cozumel Island. An ecological study found that sponges have the second highest species richness and density in La Quebrada. The aim of the present work is to describe the sponge biodiversity inhabiting the dark zone of La Quebrada anchialine cave. A total of ten species were found and are described herein, six are new species to science vis. Calyx maya n. sp. a thinly branched sponge; Haliclona (Reniera) stygobia n. sp. globe-shaped with the thinnest diameter of oxeas in its group; Haliclona (Halichoclona) chankanaabiis n. sp. tubular habit with the smallest oxeas in its group; Neosiphonia microtriaeneae n. sp. characterized by very small dichotriaenes; Svenzea germanyanezi n. sp. a lone conical shape; and Diplastrella cozumella n. sp. for its tri to multilobed tylostyles. The other four species are previously known from open reefs or deep-sea: Discodermia adhaerens, Siphonidium ramosum, Cinachyrella kuekenthali, and Plakinastrella onkodes. This is the only inventory of Porifera in Mexican caves up to now, thus the species here described are the first stygobiont sponges from Mexico with an endemism rate of Porifera in this anchialine cave of 60%. Conservation programs are needed to preserve this unique and special ecosystem.

Larval development of the stygobitic shrimp Creaseria morleyi (Creaser, 1936) (Decapoda: Caridea: Palaemonidae) from the Yucatán Peninsula, Mexico

Although the larval development of epigean palaemonid shrimps has been studied extensively, only a few investigations deal with stygobitic species. We present the larval development of the cave-adapted Creaseria morleyi (Creaser, 1936) from anchialine caves in the Tulum area, Quintana Roo, Yucatán Peninsula, Mexico. Through the discovery of a series of larvae at different stages of development, we constructed a sequence extending through the juvenile stage. The larvae (41) were captured in plankton tows above the halocline at depths ranging between 11 and 15 m during eight surveys conducted between 2013 and 2016. Six larval stages and the first juvenile were identified; however, it is clear from the gradual modification of structures and appendages that more stages exist. The first larvae have a large quantity of vitellum and do not feed, since they have only rudimentary, and possibly non-functional, mouthparts. In the sixth stage and the juvenile, when the stages have no vitellum left, the mouthparts, chelae, and pleopods develop entirely. A comparison with other palaemonid shrimps suggests that C. morleyi has a greater affinity with those palaemonid species possessing extended larval development as is seen in species of MacrobrachiumSpence Bate, 1868.