A new subterranean Maraenobiotus (Crustacea: Copepoda) from Slovenia challenges the concept of polymorphic and widely distributed harpacticoids

Maraenobiotus slovenicus sp. nov. is described from subterranean waters of a very cold, temporary karstic spring in the vicinity of Velika Pasica cave, central Slovenia. A detailed examination of numerous specimens reveals a low level of morphological variability in this population. Morphological characters traditionally used in the genus Maraenobiotus Mrázek, 1893 would identify our population as a subspecies of the polymorphic and widely distributed M. vejdovskyi Mrázek, 1893. This species was reported from the Palearctic, with at least six accepted subspecies, some of which have been reported in sympatry or parapatry, sometimes even without any apparent niche partitioning. One of these subspecies, M. vejdovskyi truncatus Gurney, 1932, originally described from the UK and later on also reported from Italy and Japan, shares with our population the extremely reduced female principal caudal setae. However, a closer examination of the caudal armature and other characters reveals significant differences between these disjunct populations. We propose a hypothesis of distinct species within the M. vejdovskyi-complex, and critically review all recognized and some unrecognized morphotypes and subspecies. As a result, three new species names are proposed for previously reported populations from Italy and Japan: Maraenobiotus galassiae sp. nov.; M. isidai sp. nov.; and M. pescei sp. nov. Four subspecies of M. vejdovskyi are now elevated to the full specific rank: M. anglicus Gurney, 1932; M. arctica Löffler; M. tenuispina Roy; and M. truncatus Gurney, 1932. This hypothesis remains to be tested using molecular (and other) tools, but can serve as a viable alternative to the concept of polymorphic and widely distributed freshwater harpacticoids. http://zoobank.org/urn:lsid:zoobank.org:pub:92302CF9-21BA-4454-A3DD-337BB7152DCE


Introduction
The genus Maraenobiotus was established by Mrázek (1893) for the newly described subterranean species from the Czech Republic, M. vejdovskyi Mrázek, 1893(see Huys 2009). This species was afterwards found in Scotland different caudal rami shape are in fact two distinct (but closely related) species. Kim et al. (2014) provided molecular evidence for the variability in the caudal rami shape between disjunct (Korean and Russian) populations of the marine littoral Enhydrosoma intermedia Chislenko, but these are only minor in nature and congruent with their geographic variation in body size.
In this paper we describe a new subterranean harpacticoid from Slovenia (Europe) that has female caudal rami with truncated principal caudal setae, like those of M. veydovskyi truncatus from Great Britain and some specimens of M. veydovskyi from Japan and Italy reported by Ishida (1987) and Pesce et al. (1994) respectively. We also critically review recognized and unrecognized morphotypes and subspecies within the M. vejdovskyi-complex, and propose a hypothesis of distinct species for at least some of them.

Material and methods
The type locality for our new species is a temporary spring Močilo, 45. 551464°N , 14.293337°E, 647 m above sea level. It is on the western side of the village Gornji Ig (c.20 km south of Ljubljana, capitol of Slovenia) and about 200 m north-west from the entrance of Velika Pasica cave (Brancelj 2000(Brancelj , 2002(Brancelj , 2009. Part of the water in the spring originates from the cave and part from an undefined catchment area (c.0.5 km 2 ). The spring is at the base of c.10 m steep cliff and about 25 m below the Velika Pasica cave entrance. The mouth of the spring Močilo is triangular in shape, about 20 cm wide at the base and about 30 cm high, descending at an angle of 45°into the rock. The geology is thinly bended Norian-Retian dolomite from the Upper Triassic period (Pleničar 1970). The spring is usually active between 48 and 72 h, and only after heavy rain or snow melt, with a maximum discharge of about 10 l s −1 . It is surrounded by a forest of the Abieti fagetum dinaricum-type and small patches of meadows.
Basic physical parameters of water quality (cave water mixed with melted snow water) during our sampling period were: water temperature, average 4.4°C, (range:  Pesce et al. (1994).
Sampling of the spring Močilo took place three times in the beginning of 2014 (20 January, and 8 and 22 February). A drift-net (mouth diameter 30 cm, length of the filtering cone 1.5 m, mesh size 60 µm, fitted at the end with a special filtering bottle ;Brancelj 2004) was inserted at the mouth of the spring for 24 h on each sampling occasion. The majority of filtered water was collected from the mouth of the spring, but part of it originated from slopes surrounding the spring (area of about 10 m 2 ). Slopes at the mouth of the spring were covered with litter; the main source was beech leaves (Fagus sylvatica L.). Collected material from the drift net was transferred into 750 ml plastic bottle and fixed in c.60% ethanol. Water temperature, electric conductivity and oxygen concentration were measured on-the-spot with a Multi 340i instrument (WTW Company, Oberbayern, Germany). Samples for water chemistry analyses (major ions: Ca 2+ , Mg 2+ , K + , Na + , SO 4 2-, Cland NO 3 -) were collected into 50 ml plastic bottles. They were transferred in the laboratory, into a cold box, stored in a refrigerator at +4°C, and analysed within 48 h using an ion chromatograph (761 Compact IC, Methrom, Herisau, Switzerland).
Biological samples were checked several hours after sampling and specimens of different animal groups were picked out and stored in 70% ethanol in plastic vials (details of the accompanying fauna are listed in the Discussion).
Before dissection, specimens were placed in a mixture of glycerol and 70% alcohol (ratio~1:10 v/v), which was replaced within half an hour by pure glycerol. They were dissected at 100× magnification under an Olympus SZH 2 stereomicroscope (Olympus, Tokyo, Japan). Examination of all appendages and body ornamentation was done under a magnification of 1000×. Drawings were made at a magnification of 1000× with a drawing tube mounted on an Olympus microscope (BHS 40), except for the female/male habitus (400× magnification). The final version of the drawings was made using the CorelDRAW ® 12 graphic program (www.corel.com). For permanent slides all body parts were placed in a drop of glycerol on a microscope slide, covered by a cover glass, and sealed with nail polish.
Specimens for scanning electron micrography (SEM) were dehydrated in progressive ethanol concentrations, transferred into pure isoamyl-acetate, criticalpoint dried, mounted on stubs, coated in gold, and observed under a Hitachi S-4700 scanning microscope (Hitachi, Japan) on the in-lens detector, with an accelerating voltage of 10 kV and working distances between 12.3 and 13.4 mm; micrographs were taken with a digital camera.
Short row of spinules laterally on fourth urosomal somite; fifth urosomal somite dorsolaterally and ventrally with continuous row of spinules, smallest in ventromedial part ( Figures 1A, G, 2D, 7B, C). Anal somite laterally with short row of strong        Anal operculum large, rounded, overreaching distal end of anal somite, with some 20 well developed spinules along distal margin (Figures 1A, G, 7B, C). Ventral side with additional row of minute spinules. Anal operculum about 58% of total anal somite width.
Caudal rami conical, slightly diverging, with inner and outer margins slightly convex; ramus as long as wide, with no dorsal keel (Figures 1A, G, H, 2E, 7B, C). Inner distal corner dorsally with 6-10 strong spines, ventrally inner corner with row of long and slightly curved spinules followed by smaller spinules toward outer corner. Anterolateral external accessory seta (I) slightly shorter than furcal ramus, inserted close to base; anterolateral external accessory seta (II) shorter than seta I and thin. Posterolateral seta (III) positioned below insertion of outer terminal seta (IV), shorter than seta II, very thin. Outer terminal seta (IV) reduced to minute knob, heavily chitinized. Inner terminal seta (V) reduced to minute knob, bigger then seta IV, heavily chitinized. Inner accessory seta (VI) reduced, not discernible from nearby spines. Dorsal seta (VII) slightly longer than caudal ramus, inserted on internal side, at about mid length.
Antenna ( Figures 2B, 5B) with allobasis, and robust, one-segmented Exp and Endp. Three strong spines on outer margin of Endp, increasing in length distally; terminal armature consisting of one short spine, one twice as long as short spine, and four geniculate setae. Exp with four spiniform setae, one ornamented with spinules on one margin.
Mandible ( Figure 5C) short and robust, with two strongly chitinized teeth on gnathobase. Dorsal seta near gnathobase. Mandibular palp very short, fused with coxa, with five setae, one of them twice as long as the other.
Maxillule ( Figure 5D) with strong and robust spines on praecoxal arthrite. Coxa with strong, chitinized spine and slim seta. Basis with strong, beak-like outgrowth, with long seta and long setules unilaterally. Exp and Endp reduced, fused with basis; each represented by two weak setae.
Maxilla ( Figure 5E) two-segmented; syncoxa with 2 endites with 3 and 2 elements. Basis with strong spine and long seta. Endp reduced to three setae.
Maxilliped ( Figure 5F) comprising syncoxa, basis, and one-segmented Endp. Syncoxa with seta distally. Basis three times as long as wide, with 8-10 spinules positioned near palmar margin dorsally, equal in length. Endp drawn out into strong, acutely curved claw; as long as basis and armed with several spinules in distal half; additional armature represented by a short seta. P1 ( Figures 3B, 6A) with two-segmented Exp and Endp, equal in length. Basis with strong and robust inner spiniform seta and stout outer basal spine. Exp-1 with strong outer spine; Exp-2 with two strong spines laterally, spine and two long geniculate setae terminally; inner terminal seta longer than Exp. Endp-1 with long seta on inner margin at two thirds length. Endp-2 terminally with three setae; innermost short and soft, terminal seta long and geniculate, outer one spiniform, with spinules on outer margin. P2 ( Figures 3B, 6B) on basis with spiniform outer seta. Three-segmented Exp and two-segmented Endp. Endp as long as Exp-1 and Exp-2 combined. Exp-1 1.3 times as long as wide, with strong spine at distal corner. Exp-2 with strong outer spine. Exp-3 twice as long as wide, with two outer spines, terminal spiniform seta with strong spinules unilaterally and slim and bare seta, as long as spiniform seta. Endp-1 as long as wide, with seta on inner margin, at about two thirds of segment length. Endp-2 twice as long as wide, with seta along inner margin at half length of segment. Terminally two long soft setae, sub-equal in length; robust spiniform outer terminal seta, as long as Endp-2.
P3 ( Figures 2G, 3B, 6C) with long and thin outer basal seta. Three-segmented Exp and two-segmented Endp. Endp slightly shorter as Exp-1 and Exp-2 combined. Exp-1 and Exp-2 similar to that of P2. Exp-3 with relatively weak spine on 2/3 of outer margin, robust spine subterminally and two robust setae terminally. Additional two robust setae on inner margin at 1/3 and 2/3 length of segment, respectively. Endp two-segmented; Endp-1 as in P2. Endp-2 with a row of strong spines on outer margin. Terminally two long soft setae, sub-equal in length; robust spiniform outer terminal seta, as long as Endp-2; two long and weak setae on inner margin at 1/3 and 2/3 length of segment, respectively.
P4 ( Figures 2G, 6D) with outer basal seta long and thin, with additional very long and thin spinules. Three-segmented Exp and two-segmented Endp. Endp reaching about to middle of Exp-2. Exp-1 and Exp-2 similar to those of Pa and P3 but with additional robust seta on inner distal corner of Exp-2. Exp-3 twice as long as wide, with relatively weak spine located subterminally on outer margin. Terminally two long soft setae, sub-equal in length; robust spiniform outer terminal seta, shorter than Exp-3; long seta on inner margin at half length of segment, respectively. Endp-1 as wide as long, smaller as in P2 or P3 respectively. Spine on inner margin with distinct long spinules. Endp-2 with short spine on outer margin, at 2/3 of segment length. Terminally robust spiniform seta on outer position and two setae unequal in length. Seta on inner margin at mid length of segment.
P5 ( Figures 2D, H, 3A, 6E) Exp and baseoendopod not distinctly separated; baseoendopodal lobe well developed, with four strong pinnate spines of unequal length; innermost three increasing in length toward outside; outermost shortest, Exp lobe longer than baseoendopodal, as long as wide, with three apical setae of unequal length; innermost shortest, with strong spinules; medial longest, with strong spinules; outer one bare. Outer lateral seta on baseoendopodal lobe long and bare, but one very long setula. P6 ( Figure 7A) fused, small, forming simple plate; each with thin seta with several long setulae.
Male, body length, measured from tip of rostrum to posterior margin of caudal rami, 524-554 µm; average: 543 µm (n = 4), elongated, widest at distal part of cephalosome, rest of body slightly narrower, evenly tapering toward anal somite, colourless ( Figure 3C, D, E). Naupliar eye not discernible. Rostrum small. Integumental window not discernible. Posterior margins of thoracic and abdominal somites dorsally and ventrally smooth (Figures 3D, E). Short row of small spinules laterally on first urosomal somite; continuous row of small spinules dorsally on second urosomal somite ( Figure 4F); third urosomal somite dorsally with three groups of small spinules; fourth and fifth urosomal somite dorsally with four groups of small spinules, laterally with longer spinules; fourth urosomal somite ventrally with continuous row of spines equal in length; fifth urosomal somite ventrally with continuous row of spinules unequal in length ( Figures 3C, E, 7D). Anal somite laterally with short row of strong spinules; ventrally row of spines between bases of furcal rami (Figures 3E, 4G, 7D). First and second urosomite with cuticular window each; large pore next to cuticular window on first urosomite ( Figures 3D,  4F, H).
Anal operculum well developed, rounded, overreaching distal end of anal somite, with about 10 well-developed spinules along distal margin ( Figure 7D, E).
Caudal rami almost rectangular, slightly longer than wide, diverging; outer margin slightly convex; with no dorsal keel ( Figures 3C, E, 7D, E). Ventrally row of spinules at distal part of ramus ( Figures 3E, 7D). Anterolateral external accessory seta (I) thin, slightly longer than ramus, inserted at 1/3 of ramus length ( Figures 4G,  7D, E); anterolateral external accessory seta (II) as long as seta I, thin; positioned at distal corner of ramus. Posterolateral seta (III) absent. Outer terminal seta (IV) about 4 times as long as seta II, with fracture plane. Inner terminal seta (V) about 2.5 times as long as seta III, straight, robust, with fracture plane. Inner accessory (VI) slightly longer than seta I. Dorsal seta (VII) slightly longer than caudal ramus, inserted on internal side, at about mid length.
Antenna, mandible, maxillule, maxilla, maxilliped, P1 similar to those in female. P2 ( Figure 8B): Exp similar to female. Endp two segmented. Endp as long as Exp-1 and Exp-2 combined. Endp-1 0.75 times as long as wide, with seta on inner distal corner. Endp-2 three times as long as wide, with seta along inner margin at 1/3 length of segment. Terminally two soft setae, sub-equal in length, slightly shorter than segment; well-formed incision present on inner margin subterminally; at half length of segment on inner margin short spine, and at 1/4 two long spinules. P3 ( Figure 8C) with long and thin outer basal seta. Three-segmented Exp and two-segmented Endp. Endp reaching middle point of Exp-2. Exp-1 and Exp-2 similar to that of female. Exp-3 with relatively weak spine on 2/3 of outer margin, robust spine subterminally, long robust outer seta and short inner spiniform seta terminally. Additional two robust bare spiniform setae on inner margin at 1/3 and 2/3 length of segment, respectively. Endp two-segmented; Endp-1 with long spear-like apophysis, reaching tip of Exp-3. Endp-2 with relatively short blunt spine curving outward and spear-shaped seta as long as spear-like apophysis of Endp-1.
P4 ( Figures 3D, 8D) with outer basal seta long and thin, with additional two very long and thin spinules. Three-segmented Exp and two-segmented Endp. Endp extending just beyond Exp-1. Exp armature similar to female but less robust. Endp-1 half as wide as long, with no spine/seta on inner margin. Endp-2 with short spine on outer margin, at 2/3 of segment length. Terminally spiniform seta on outer position and two setae unequal in length. No seta on inner margin. P5 ( Figures 3D, 4F, 8E) Exp and baseoendopod well separated; baseoendopod well developed, with two strong pinnate spines of unequal length; inner longer. Exp longer than baseoendopod, as long as wide, with four elements; inner three setae increasing in size toward outside; innermost seta bare; medial with unilateral spinules, outer with strong spinules bilaterally. Outermost seta as long as second innermost seta, with unilateral spinules. Outer lateral seta long with few long setules unilaterally.

Variability
No variability was observed other than minor variation in the number of spinules on the abdominal somites.

Etymology
The new species is named after Slovenia, where the specimens were collected for the first time.

Remarks
This Slovenian new species undoubtedly belongs to the Maraenobiotus vejdovskyi complex, which is mostly defined by the armature formula of its appendages (Lang 1948). Its truncated female principal caudal setae would put it close to Maraenobiotus veydovskyi truncatus Gurney, 1932, but a closer examination of this subspecies (which is elevated to the full specific rank below) and detailed comparison with our population reveals a number of significant differences. For example, M. vejdovskyi truncatus has a much shorter anal operculum than M. slovenicus sp. nov., which is ornamented with minute spinules (versus long spinules in M. slovenicus). Also, M. vejdovskyi truncatus has no distal lateral caudal setae in female (versus well-developed setae in M. slovenicus), and the transformed Endp of the male third leg has but a single apical element (versus two apical elements in M. slovenicus). Unfortunately, many other characters could not be compared because of a limited set of illustrations provided by Gurney (1932) for M. vejdovskyi truncatus. There are three other reported and illustrated populations from this complex with truncated female principal caudal setae, one from Japan (Ishida 1987) and two from Italy (Pesce et al. 1994), which we describe below as new species. However, both M. ishidai sp. nov. from Japan and M. galassiae sp. nov. from Italy (see below) have much longer and cylindrical caudal rami. Maraenobiotus pescei sp. nov. from Italy (see below), however, has caudal rami very similar in shape to those of M. slovenicus, but the two differ in the lateral armature of the caudal rami (lateral setae very reduced or absent in M. pescei versus well developed in M. slovenicus), number and size of spinules on the anal operculum (longer and fewer in M. slovenicus), segmentation of the antennal Exp (two-segmented in M. pescei versus one-segmented in M. slovenicus), number of apical elements on the second Endp segment of the male P3 (one in M. pescei versus two in M. slovenicus), and relative length of Endp spine on the male P5 (the inner one almost twice as long as the outer one in M. pescei versus nearly equal in M. slovenicus). Unfortunately, illustrations and descriptions of other four species are not as complete as those of M. slovenicus, so many morphological characters could not be compared.

Type material
Holotype female illustrated by Ishida (1987) in his figure 14n from the type locality, originally deposited in the author's private collection. Current location unknown.

Etymology
The species name is dedicated to late Dr Terue Ishida, who discovered this specimen from Japan. The name is a noun in the genitive singular.

Remarks
This female specimen has truncated principal caudal setae as in Maraenobiotus veydovskyi truncatus Gurney, 1932, but the caudal rami look very different in shape and size. They are cylindrical in dorsal view and almost twice as long as wide in M. ishidai sp. nov., while the caudal rami in M. vejdovskyi truncatus are almost conical in shape and about as long as wide. Also, in the latter species the distal lateral caudal setae seem to be either much reduced in size or absent, while they are well developed in the former. Finally, the anal operculum is much longer in M. vejdovskyi truncatus than in M. ishidai. There is very little chance that these very disjunct populations, with so vastly different caudal rami and anal operculum, could belong to the same species. In fact, M. ishidai differs so much from the other four species of Maraenobiotus with truncated female caudal setae, which are all European, that we believe there is a strong argument for them to be separate species. Its caudal rami are most similar in shape to those of the Italian M. galassiae sp. nov. (see below) and it may be plausible that the two have shared a recent common ancestor with a wide Holarctic range. Major differences involve the position of the dorsal caudal seta (nearly central in M. galassiae versus close to inner margin in M. ishidai), as well as the shape and inclination of the posterior margin of the ramus itself (convex and perpendicular to the body axis in M. ishidai versus straight and diagonal in M. galassiae). Maraenobiotus ishidai differs from M. slovenicus sp. nov. (see above) and M. pescei sp. nov. (see below) in the much longer and cylindrical caudal rami.
Unfortunately, we do not know which appendages illustrated by Ishida (1987) belong to this species, so they cannot be compared to other species from the M. vejdovskyi complex until the holotype has been found and redescribed.

Etymology
The species name is dedicated to Prof. Giuseppe Lucio Pesce, who discovered these specimens in Italy with his collaborators. The name is a noun in the genitive singular.

Remarks
The female specimen of this Italian population has truncated principal caudal setae as in Maraenobiotus veydovskyi truncatus Gurney, 1932, and the caudal rami look very similar in shape and size, except that the Italian population has slightly smaller caudal rami in proportion to the anal somite. However, M. pescei sp. nov. differs from M. vejdovskyi truncatus by much reduced (or absent) all lateral setae on the caudal rami, as well as by a much longer apophysis on the male Endp P3.
Maraenobiotus pescei differs from M. slovenicus sp. nov. also by very reduced (or absent) all lateral setae on the caudal rami, while the caudal rami of two other species from the M. vejdovskyi complex, M. ishidai sp. nov. (see above) and M. galassiae sp. nov. (see below), are cylindrical and much longer.

Type material
Holotype female illustrated by Pesce et al. (1994)

Etymology
The species name is dedicated to Prof. Diana M. P. Galassi, who discovered these specimens in Italy with her collaborators. The name is a noun in the genitive singular.

Remarks
This female specimen has truncated principal caudal setae as in Maraenobiotus veydovskyi truncatus Gurney, 1932, but the caudal rami look very different in shape and size. They are cylindrical in dorsal view and almost twice as long as wide in M. galassiae sp. nov., while the caudal rami in M. vejdovskyi truncatus are almost conical in shape and about as long as wide. Also, in the latter species the distal lateral caudal setae seem to be either much reduced in size or absent, while they are well developed in the former. The caudal rami of M. galassiae are most similar in shape to those of the Japanese M. ishidai sp. nov. (see above) and it may be plausible that the two have shared a recent common ancestor with a wide Holarctic range (for major differences between them see above). Maraenobiotus galassiae differs from M. slovenicus sp. nov. (see above) and M. pescei sp. nov. (see above) by much longer and cylindrical caudal rami, among other things.

Discussion
As noted above, relationships among species and subspecies of Maraenobiotus are very complicated. In the absence of any fresh material to undertake a molecular study, we have tried to reinterpret some old morphological data in the light of modern studies in other groups of copepods (Karanovic and Cooper 2012). Based on our study of numerous specimens of M. slovenicus sp. nov., we concluded that morphological variability in this population is very low. This especially refers to the truncated nature of the female caudal principal setae. However, this character was reported to be very variable in M. vejdovskyi s.l. (Gurney 1932;Lang 1948;Ishida 1987;Pesce et al. 1994), but the evidence for this was lacking (no sympatric forms with different caudal rami shape, except in one unsubstantiated statement by Ishida 1987). In addition to this, several subspecific categories have been described with parapatric or sympatric ranges (see Introduction), or those were implied by subsequent records, but never in the same locality. A more parsimonious explanation would be that we are actually dealing with a number of closely related but distinct species. Thus we formally elevate here to the full specific rank the following recognized subspecies of M.  (Ishida 1987;Pesce et al. 1994) morphotypes with truncated female principal caudal setae from the M. vejdovskyi s.l. complex, we conclude that they cannot be closely related. Thus we have named three new species here, based on previous illustrations (as their material was not available to us): Maraenobiotus galassiae sp. nov.; M. isidai sp. nov.; and M. pescei sp. nov. (see above). We conclude that this condition originated convergently probably in all cases, but at least in four instances (the Italian M. galassiae and the Japanese M. ishidai may be an exception; see above). Testing this hypothesis using molecular phylogenies (as in Cooper 2011, 2012;Karanovic and Krajicek 2012) or those based on micro-morphological characters (as in Karanovic and Kim 2014) would be a priority for our future studies.
It is, however, unclear why this particular trait would evolve so many times in one species-complex, and why only in females and not in males. Some speculations we can offer would be a conservation of energy in the interstitial/semi-terrestrial environment, where they are not much needed, or, perhaps, to decrease mating pressure from males, because in canthocamptid harpacticoids (and many others) males grab female caudal setae with their antennules in the first act of copulation (Huys and Boxshall 1991). The unusually complicated three-dimensional structure on the male antennule in M. slovenicus ( Figures 3F, G, H, 4C, E) is certainly well adapted for grabbing the reduced caudal rami of their females, which may be indicative of an evolutionary sexual conflict and arms races between the sexes.
Males and females of M. slovenicus, along with a few juveniles, appeared in a drift from a temporary spring, after a very cold and dry period in winter. This probably excludes the possibility that their origin is wet litter just next to the temporary spring. Most of specimens (males and females) were covered with dense colonies of sedentary protozoans (Ciliates), indicating that the population of M. slovenicus probably originated from a permanent water body inside the cave. The same phenomenon, where specimens were covered with dense colonies of epibionts, was observed on specimens of the genera Morariopsis Borutzky and Bryocamptus Chappuis from the epikarstic zone in the nearby cave Velika Pasica (Brancelj 2000;pers. obs.). However, epibionts on M. slovenicus were different from those on Morariopsis dumonti Brancelj, 2000, Bryocamptus pyrenaicus (Chappuis) and B. typhlops (Mrázek 1893), which were exclusively Suctoria. Specific co-occurrence between epibionts and hosts indicates a long-lasting co-habitation rather than an opportunistic co-existence. At the same time, no such epibionts were observed on the accompanying copepod community.
Such composition of the drift fauna indicates that the water from the temporary spring originates both from the epikarstic/vadose zone as well as from the local phreatic zone. The new Maraenobiotus species is probably a member of the phreatic (i.e. saturated) zone, because during our long-lasting sampling of the epikarstic zone in the nearby cave Velika Pasica no specimens of the new species were collected (Brancelj 2000, pers. obs.;Wei Liu and Brancelj Forthcoming 2015).