Subterranean movement inferred by temporary emigration in Barton Springs salamanders (Eurycea sosorum)

Movement behavior is an important aspect of animal ecology but is challenging to study in species that are unobservable for some portion of their lives, such as those inhabiting subterranean environments. Using four years of robust-design capture-recapture data, we examined the probability of movement into subterranean habitat by a population of endangered Barton Springs salamanders (Eurycea sosorum), a species that inhabits both surface and subterranean groundwater habitats. We tested the effects of environmental variables and body size on survival and temporary emigration, using the latter as a measure of subterranean habitat use. Based on 2,046 observations of 1,578 individuals, we found that temporary emigration was higher for larger salamanders, 79% of which temporarily emigrated into subterranean habitat between primary sampling intervals, on average. Body size was a better predictor of temporary emigration and survival compared to environmental covariates, although coefficients from lower ranked models suggested turbidity and dissolved oxygen may influence salamander movement between the surface and subsurface. Surface population dynamics are partly driven by movement below ground and therefore surface abundance estimates represent a fraction of the superpopulation. As such, while surface habitat management remains an important conservation strategy for this species, periodic declines in apparent surface abundance do not necessarily indicate declines of the superpopulation associated with the spring habitat.

Subterranean and Anchialine Waters

Crustaceans have successfully colonized the subterranean habitat, and many have become obligate inhabitants, occurring virtually everywhere there are interconnected voids underground. With the exception of most oniscidean isopods and a few talitrid amphipods, subterranean crustaceans inhabit water (stygobionts), where they dominate the stygofauna both in biomass and diversity of species. Four major taxonomic groups predominate: amphipods, isopods, copepods, and ostracods. Although most higher crustacean taxa have representatives in both epigean and subterranean habitats, some groups such as remipedes, thermosbaenaceans, spelaeogriphaceans, bathynellaceans, mystacocarids, and gelyelloid copepods are known only from the subterranean environment. Subterranean habitats vary physically and range from organically rich shallow habitats around seeps to cave systems more than a kilometer deep. Water quality, which can range from fresh to marine to hypersaline, static to flowing, and oxic to suboxic, impacts species distribution. Dispersal patterns in subterranean crustaceans are also diverse. Freshwater stygobiont crustaceans have narrow endemic ranges, and their dispersal is limited by saltwater. The distribution of several freshwater taxa might reflect the movement of tectonic plates. The extraordinarily diverse anchialine fauna, initially distributed along the Tethyan coast, was likely spread by vicariance due to movement of tectonic plates. Originating from epigean ancestors, many stygobionts have a marine origin. While the existence of preadaptations does not necessarily guarantee successful colonization of the subterranean habitat, a suite of characteristics is frequently observed in subterranean crustaceans, with most being weakly chitinized, lacking or with reduced eyes and pigments, and enhanced non-optic sense organs. Metabolic rates tend to be lower than in epigean crustaceans. Limited evidence indicates subterranean crustaceans are longer lived with lower reproductive potential. These adaptations make subterranean crustacean populations particularly vulnerable to anthropogenic impacts. The morphological, physiological, and life history adaptations to a subterranean existence are most likely common responses to the physical environment of each subterranean ecosystem. Extensive biodiversity and phylogeography studies are still required, and there is a pressing need to comprehend the functional role of stygofauna in subterranean waters.

Three new cave-dwelling Eukoenenia (Palpigradi: Eukoeneniidae) from limestone caves in Northern Minas Gerais state, Brazil

In this paper, we describe three new Eukoenenia species from specimens collected in limestone caves in the northern region of the Minas Gerais state, Brazil. These species present different degrees of adaptation to the subterranean habitat, with Eukoenenia magna sp. nov., with 6 blades on lateral organs and body ratios very close to other troglobitic species, being the most troglomorphic among them. This species is morphologically very similar to the Brazilian troglobites E. navi, E. eywa and E. neytiri. Eukoenenia lundi sp. nov. and Eukoenenia jequitai sp. nov. are probably closely related species due to their substantial morphological resemblance. These two species are closer to E. virgemdalapa among the Brazilian species described to date. We provide a table summarizing the main diagnostic characters of the three species herein described and those of the Brazilian congeners to facilitate morphological comparisons.

Taxonomic revision of the subterranean genus Virpazaria Gittenberger, 1969 (Gastropoda, Spelaeodiscidae)

Virpazaria Gittenberger, 1969 is distributed in the Balkan Peninsula (Albania, Montenegro and Croatia) and inhabits the shallow subterranean habitat (MSS) on limestone base rock. Reviewing historical and recently collected material, two species, Virpazaria (Virpazaria) gittenbergeri Fehér & Erőss sp. nov. and Virpazaria (Virpazaria) pesici Fehér & Deli sp. nov., are introduced as new to science. The conservation status of the new species are assessed using IUCN criteria. Two taxa, Virpazaria (Virpazaria) pageti alexanderi Reischütz & Subai, 2012 and Virpazaria (Aemiliella) ripkeni pastorpueri Reischütz et al., 2011, are synonymized with their nominate subspecies. Some new distribution records, as well as geological and geomorphological data about the known locations for Virpazaria, are presented.

On the ecology and biology of two endogean millipedes (Diplopoda: Julida: Julidae) endemic to the Western Rhodope Mtn., Bulgaria

Mountain slopes covered with stone debris have been of special interest for zoologists since the pioneer work of Juberthie et al. (1980) who defined and described the Milieu Souterrain Superficiel, most popularly referred to in English as the Mesovoid Shallow Substratum (MSS). Today this particular habitat is classified as one of the several types of MSS, namely the colluvial MSS. In a number of recent publications, the MSS is considered as one of the Superficial Subterranean Habitats (SSHs) within a broader concept of the subterranean domain. According to a widely accepted idea, the SSHs are different in their nature but are all characterized by the absence of light which is regarded as the main factor responsible for the occurrence of troglomorphic fauna in these habitats, along with epigean species that are able to live in such conditions. The present study focuses on two julid millipedes — Typhloiulus orpheus Vagalinski, Stoev & Enghoff, 2015 and a yet undescribed genus and species of the tribe Typhloiulini — occurring in the transitional layer of fine rubble between the soil stratum and the MSS in limestone taluses in the Western Rhodope Mtn. It was revealed that the spatial distributions of the two species in the studied sites were remarkably confined and follow the same pattern, which is suggested to reflect narrow microhabitat specialization. This assumption is further supported by certain traits in the morphology and biology of the two diplopods. It can be concluded that both T. orpheus and the new genus and species are essentially stenotopic endogean elements with strict requirements for an aphotic, mesophilous, limestone environment. Given the specific ecological conditions, which differ from both the overlying soil layer and the underlying colluvial MSS, together with the existence of certain narrowly adapted species, it is worth considering the recognition of the intermediate “microvoid” breakstone layer as a separate shallow subterranean habitat.

Description of the first larval instar of Broscus crassimargo Wollaston, 1865 (Carabidae: Broscini) and notes about the presence of the species in the mesovoid shallow substratum of La Gomera (Canary Islands, Spain)

The first larval instar of the ground beetle Broscus crassimargoWollaston, 1865 endemic to La Gomera (Canary Islands, Spain) is described. This is the first comprehensive study of the primary chaetotaxy of the three tagmata ever carried out in larvae of Broscini, being also accompanied by a detailed iconography. The implications of the results of this chaetotaxy analysis are discussed in relation to the possible origin of Broscini within Carabidae. Comments on the ecological determinants for its remarkable presence in the mesovoid shallow substratum are given, analysing the differences between La Gomera and other Canary islands where samplings in the same subterranean habitat have been carried out.

New species of the genus Megalothorax Willem, 1900 (Collembola: Neelipleona) from a superficial subterranean habitat at Dobšinská Ice Cave, Slovakia

New species of Megalothorax Willem, 1900 from Dobšinská Ice Cave, Slovakia, M. dobsinensis sp. n., is described and illustrated. New species inhabits a cold habitat along an inversed temperature gradient at the cave entrance. M. dobsinensis sp. n. differs from other species of the genus by the lack of chaeta X on Ant. IV and by T-shaped inner chaetae of thoracic and abdominal sensory fields. Only two other species, M. tuberculatus Deharveng & Beruete, 1993 and M. sanctistephani Christian, 1998 lack chaeta X on Ant. IV. M. dobsinensis sp. n. differs from both species by chaetotaxy of antennae and abdomen. Summary tables of antennae and legs chaetotaxy and dichotomous identification key for species with smooth mucro are provided.

Out of the dark void: Ommatoiulus longicornis n. sp., a new julid from Spain (Diplopoda, Julida) with notes on some troglobiomorphic traits in millipedes

A new millipede species, Ommatoiulus longicornis n. sp. is described from the subterranean habitat in eastern Spain, and the elongation of its antennae is discussed in relation to the habitat where it dwells. We take the occasion to discuss the elongation of appendages as a troglobiomorphic character in millipedes and shed the light on the various, sometimes controversial, hypotheses that could have led to these modifications in millipedes and other subterranean arthropods.