Monolistra (Microlistra) fongi, Prevorčnik & Verovnik & Zagmajster & Sket, 2010

Prevorčnik, Simona, Verovnik, Rudi, Zagmajster, Maja & Sket, Boris, 2010, Biogeography and phylogenetic relations within the Dinaric subgenus Monolistra (Microlistra) (Crustacea: Isopoda: Sphaeromatidae), with a description of two new species, Zoological Journal of the Linnean Society 159 (1), pp. 1-21 : 13-17

MONOLISTRA (MICROLISTRA) FONGI SP. NOV.

( FIGS 6 , 7 )

Holotype: Adult male of 13.5 mm in length, Croatia, Kordun , cave Kuruzovića pećina, Vaganac, near Rakovica; leg. B. Sket. Inv. Collection of OB BF UL, Inv. No. ‘ Malacostraca 2245 ht’, partly dissected, preserved in ethanol.

Paratypes: Same data as for holotype, two adult males (11.2- and 10.9-mm long) and two adult females (nonovigerous, 13.3- and 11.9-mm long), Inv. No. ‘ Malacostraca 2245 pt’. One paratype deposited in the Hrvatskio prirodoslovni muzej (Croatian Natural History Museum), Zagreb, Croatia .

Other material: Croatia, Kordun, spring of the river Slunjčica, Slunj , one ex. leg. B. Jalžic´, deposited in collection of Hrvatski prirodoslovni muzej, Zagreb .

Etymology: The species is named after our colleague Daniel W. Fong, a renowned American speleobiologist. Diagnosis: Microlistra species with pairs of sickleshaped lateral processes on pereonites I, II, IV, and VI, and median sickle-shaped process on pereonites I–VII; lateral processes length shorter than distances between their bases. Epimera apically narrowly rounded to bluntly pointed. Pleotelson with pair of long sickle-shaped lateral processes, a pair of shorter, straight, narrowly pointed terminal caudal processes, and a sickle-shaped median process. Uropod rudiments elevated on small bulges, projecting over pleotelson outline.

Description of holotype and paratype males (data in parentheses): Holotype male 13.5-mm long (paratype males 11.2- and 10.9-mm long). Body width 45% (48– 53%) of body length. Head (cephalothorax) dorsally with two conical nodules. All pereonites with one median sickle-shaped process; pereonites I, II, IV, and VI each with a pair of longer sickle-shaped lateral processes, gradually increasing in size in caudal direction. Pleonite I without dorsal structures. Pleotelson width 140% (150–157%) of pleotelson length, highly vaulted, with pair of sickle-shaped lateral processes and pair of shorter straight terminal processes; lateral process length 152% (160–182%) of terminal process length. Lateral processes followed by two raised socles with uropod rudiments. Pleotelson ventrocaudal border without a groove, comparatively narrow dorsocaudal bulge projecting far beyond it. All processes remarkably shorter than distances between them. Anterior epimera apically narrowly rounded, posterior ones bluntly pointed.

Antenna I length 27% (26–28%) of body length; peduncle article 1 bent perpendicularly; ten (9) flagellar articles, articles 5–7 (3–6 and 8) with single long aestethasc each. Antenna II length about 30% (41%) of body length, seven (13–15) flagellar articles. Length ratio of peduncular articles and flagellum in antenna I 100: 92: 114: 155 (100: 26: 93: 113: 167), in antenna II 100: 110: 113: 233: 453 (100: 114: 140: 211: 703).

Mouth parts as in Monolistra (Microlistra) jalzici sp. nov. Pereopod I propodus (article 6) width 33% (39–42%) of propodus length; merus (article 4) with two serrate spines at anterodistal angle; carpus (article 5) with two biserrate spines on posterodistal margin, and one at posterodistal angle; propodus with seven biserrate spines on posterior margin and 2 (1) at posterodistal angle; setulose fringe near continuous on posterior margin of ischium (article 3) to beginning of dactylus (article 7); setules length on ischium only one third article width, diminishing towards dactylus; setulose fringe also present on anterior margin of basis to merus, setules longest on ischium; secondary unguis finely serrate. Pereopod II basis with two medium long plumose setae on anterior margin; merus with two serrate spines at anterodistal angle; carpus with one serrate spine at posterodistal angle, and one on anterodistal angle; propodus with 4 (3) short serrate spines on posterior margin; setulose fringe present on posterior margin of ischium to beginning of unguis (distal part of article 7, claw), near continuous on anterior margin of ischium to unguis; secondary unguis finely serrate. Pereopod VII basis with one short plumose seta on anterior margin and one at anterodistal angle; ischium with one short plumose seta on anterior margin; merus with one serrate and one biserrate spine at anterodistal, angle and one short plumose seta on posterodistal angle; carpus with two serrate spines on posterior margin, one at posterodistal angle, one biserrate spine at anterodistal angle, and two on distal margin; propodus with three serrate spines on posterior margin, one at posterodistal angle and one short plumose seta at anterodistal angle; setulose fringe present from posterodistal angle of ischium to beginning of unguis, anterior margins mainly without setules, except for distalmost parts of ischium, merus, and carpus, setules extremely short; secondary unguis hidden within thick mat of unresolved structure. Relative length of pereopods I, II, and VII: 29, 40, and 55% (30, 52, and 55%) of body length; length ratio of articles (coxa excluded) in pereopod I 100: 63: 45: 20: 76: 46 (100: 61: 41: 23: 64: 35), in pereopod II 100: 56: 38: 57: 62: 36 (100: 62: 40: 56: 67: 37), in pereopod VII 100: 95: 41: 67: 81: 35 (100: 93: 43: 64: 78: 32).

Pleopod I protopodite with many fine long setules along external margin, fewer and shorter setules along internal margin, and and two strong spines at internal angle; exopodite elliptical, with six (7) plumose setae along terminal margin, scarce slender short spines on upper surface, and setules at proximo-external angle; endopodite about half as wide and nearly as long as exopodite, proximally almost parallel sided, distally slightly tapering, with three plumose setae on rounded terminal margin, without setules at proximo-internal angle. Pleopod II similar to I, but with more numerous plumose setae; endopodite as wide as exopodite, slightly widened distally, with 29 (28) plumose setae on terminal margin; appendix masculina distally sicle-shaped, apically pointed, its length 120% (116–119%) of endopodite length; exopodite with 15 (13) plumose setae on terminal margin, and slender short spines on the upper distal surface. Pleopod III exopodite elongate subovoid, without respiratory area, with long transverse suture at its external margin and short suture at the internal margin. Pleopod IV of similar shape, transverse suture at the lateral margin almost reaching respiratory area; area length 71% (76%) of exopodite length, surface 50% (54%) exopodite surface. Pleopod V exopodite irregularly elliptical without thick sclerotized ridge, but with three slender spines along proximal half of external margin; three sclerotized patches on mediodistal half differently shaped and less densely scaled than in M. (Microlistra) jalzici sp. nov.; respiratory area on interoproximal half, its length 39% (48%) of exopodite length, surface 30% (36%) of exopodite surface. Vestigial uropods as in M. (Microlistra) jalzici sp. nov.

Description of paratype females: Females of 11.9 and 13.3 mm in length; larger than males; body width 43–44% of body length. Pleotelson width 126–128% of pleotelson length, dorsocaudal vault surpassing pleotelson ventrocaudal border to greater extent than in males.

Antenna I length 25% of body length; of ten flagellar articles, articles 3–6 and 8, each with single long aestethasc. Antenna II length 34–38% of body length, flagellum of 14 or 15 articles. Pereopod I spines and setulose fringe as in males, but carpus with two biserrate spines at posterodistal angle; propodus with four biserrate spines on posterior margin and one or two at posterodistal angle. Pereopod II spines and setulose fringe as in males, but merus with one or two serrate spine at anterodistal angle. Pereopod VII spines and setulose fringe as in males, but merus with one serrate spine at anterodistal angle; carpus with one serrate spine at posterodistal angle and two biserrate spines at anterodistal angle; propodus with between one and three serrate spines on posterior margin, none or one at posterodistal angle, and one short plumose seta at anterodistal angle. Relative length of pereopods I, II, and VII 27–29, 38–41, and 50–54% of body length, respectively; length ratio of their articles (coxa excluded) in pereopod I 100: 45: 35: 17: 61: 35/100: 52: 34: 17: 58: 35, in pereopod II 100: 57: 34: 51: 62: 35/100: 58: 37: 53: 64: 34 in pereopod VII 100: 77: 35: 57: 73: 30/100: 90: 42: 64: 83: 32.

Pleopod I and II as in males, but pleopod II with 24 (25) plumose setae along distal endopodite margin. Pleopods III and IV shapes as in males. Pleopods IV and V respiratory area length 71 and 28% of exopodite length, respectively; pleopods IV and V respiratory area surface 42 and 40% of exopodite surface, respectively.

Distribution and ecology: Specimens were found scarcely in the residual pools in deeper parts of the cave Kuruzovića pećina (= Kukuruzovićeva pećina, K. špilja), functioning periodically as a boiling spring, near Vaganac, Kordun, Croatia. They were accompanied by a few specimens of two additional species, M. (Monolistra) caeca and M. ( Monolistrella ) sp., some shrimps ( Troglocaris sp. , Decapoda ), slightly troglomorphic specimens of Synurella ambulans O.F. Müller (Amphipoda) , more numerous unidentified Cyclopoidea (Copepoda), and single specimens of troglobiotic Proasellus sp. (Isopoda) and Niphargus steueri Schellenberg (Amphipoda) . Besides crustaceans, numerous snails, Hydrobioidea (Gastropoda), few Oligochaeta and Nematoda, and only three specimens of certainly trogloxene Chironomidae larvae ( Diptera ) were present in the pools. The other locality is the big karst spring of Slunjčica, ~ 20 km in the north-western, i.e. ‘Dinaric’, direction.

Remarks: The anterior and the posterior margins of the pereopod articles are covered with an unidentified layer of varying thickness, considerably hindering the observation and illustration of the pereopods; the lining may represent an extremely dense crust of the interlaced short setulae, and/or mats of bacteria attached to setae, or of something else.

Monolistra (Microlistra) fongi sp. nov. is most similar to the related type species Monolistra (Microlistra) spinosa by its appearance: its dorsal processes are similarly arranged, but remarkably shorter. Its epimera are apically blunt, whereas they are sharply pointed in Monolistra spinosa and some other species with long processes. The huge respiratory areas on exopodites of pleopods IV and V are even larger than in Monolistra (Microlistra) spinosa , Monolistra (Microlistra) spinosissima , and Monolistra (Microlistra) sketi .

Figures

Figure 6. Monolistra (Microlistra) fongi sp. nov., cave Koruzovića pećina, Croatia, holotype male, 13.5 mm: A I, II, antennae I and II; B, body oblique-lateral view; E, epimera; F, frons: with ep, epistome and la, labrum; Pe VII, pereomere VII; Plp I–II, pleopods I–II; Plt(1), pleotelson, lateral view; Plt(v), pleotelson, ventral view: with U, uropod rudiment.

Figure 7. Monolistra (Microlistra) fongi sp. nov., cave Koruzovića pećina, Croatia, holotype male, 13.5 mm: Plp III–V, pleopods III–V; Pp I, II, VII, pereopods I, II, VII.