Crenoicus buntiae, Wilson & Ho, 1996

Wilson, George D. F. & Ho, L. E., 1996, Crenoicus Nicholls, 1944 (Crustacea, Isopoda, Phreactoicidea): Systematics and biology of a new species from New South Wales, Records of the Australian Museum 48 (1), pp. 7-32 : 15-27

Crenoicus buntiae n.sp.

Type material. HOLOTYPE. P44348, adult male, bl 10.76 mm; NSW 758, Mumbedah Swamps , Kanangra-Boyd National Park , NSW, Australia; Sphagnum swamp at head of Mumbedah Creek, Boyd Plateau: NSW 758, 33°53.73'S, 15004.05'E, 1200 m, 2/411992, collected by G. Wilson and party . PARATYPES from NSW 758: P44349, adult male, body length 10.8 mm, dissected ; P44350, preparatory female, bl 8.25 mm, intact ; P44351, preparatory female, bl 8.5 mm ; P44352, brooding female, bl 6.35 mm, partially dissected ; P44353, preparatory 2 females, bl 7.7 mm, intact ; P44354, brooding female, bl 6.7 mm, intact ; P44355, adult male, bl 10.4 mm, intact ; P44356, adult male, cephalon only ; P44394, preparatory female, bl 5.2 mm, partially dissected ; P44359, adult male, bl 9.7 mm, partially dissected ; P44395, adult male, bl 6.5 mm, partially dissected ; P44396, brooding female, bl 6.2 mm, partially dissected ; P44457, 303 specimens used for measurements . PARATYPES from NSW 485, 33°53.76'S, 15003.92'E, 1200 m, 1811111992, collected by G.Wilson and party: P44463, 197 specimens used for measurements; NMV J40520 male, 2 females ; USNM 253241 , male, 2 females ; ZMUC CRUI774 , male, 2 females .

Other material: Kanangra·Boyd National Park, NSW. P44458, NSW 757: Luther's Creek near road, Sphagnum & sedge spring in old paddock, 33°52.78'S, 15002.72'E, 1215 m, 2/411992. P44480, NSW 486: Luther's Creek near road, spring-fed swamp of Sphagnum and gelatinous algae in fresh water over silt, 33°52.82'S, 15002.62'E, 1225 m, 1911111992. P44474, NSW 487: Roly Whalen Swamp, Sphagnum moss & mixed aquatic vegetation in fresh water 33°58.55'S, 15003.30'E, 1180 m, 1711111992. P44475, NSW 478: Jensen's Swamp, Sphagnum moss & mixed aquatic vegetation in fresh water, 33°58.65'S, 15002.76'E 1175 m, 1711111992. P44476, NSW 479: Jensen's Swamp, Sphagnum moss & mixed aquatic vegetation in fresh water, 33°58.59'S, l5002.78'E 1175 m, 171 1111992. P44460, NSW 480: Dingo Swamp, mixed sedge Sphagnum and sawgrass in fresh water, 33°59.34'S, 15002.39'E 1180 m, 17/1111992. P44477, NSW 482: Boyd Hill Swamp, downstream from clumps of Sphagnum & sedge in fresh water, 33°56.97'S, l 50°1.44'E, 1225 m, 1811111992. P44478, NSW 483: "Oldmeadow Swamp," Sphagnum and mixed water plants in spring fed fresh water, 33°56.56'S, l5002.48'E, 1211 m, 18/1111992. P44479, NSW 484: Belarah Swamp, amongst Sphagnum , sticks & roots submerged in fresh water stream, 33°54.31'S, 15004.65'E, 1185 m, 1811111992. All material collected by G. Wilson and party.

Other material, Council Creek population ( Crenoicus sp. cf. buntiae ). P44481, NSW 487: Swamp near road outside of Kanangra-Boyd National Park boundary, NSW, eastern headwaters of Council Creek, in Sphagnum & gelatinous algae over gravelly substrate, 33°50.51'S, 15000.80'E, 1180 m, 191 1111992, collected by G. Wilson and party.

Etymology. This species is named after Ms Bunty Oldmeadow, who accompanied us on a November 1992 field trip to collect isopods on the Boyd Plateau. Bunty aided our collecting effort and maintained a cheerful demeanour despite chilling rain and countless leeches. Ms Oldmeadow also suggested "friartuck" as a "common" name for phreatoicideans.

Diagnosis. Posterior robust seta on ventral margin of pleotelson subequal or shorter than more anterior robust seta. Maxillipedal epipod distally rounded. Male pereopod I basis anteroproximal surface with less than 5 setae, lacking dense group of setae. Male pereopod IV propodus not dorsally expanded, distal width less than palm length; ischium posterodistal margin with approximately 3-4 setae. Pleopod I exopod proximal part straight (not concave), widest point approximately midlength. Male pleopod 11 appendix masculina with smooth shaft; distal tip laterally spatulate, medially thickened with 2-3 tiny rounded denticles, distal seta basally narrower than distal tip; endopod distal rounded, lacking indentation; distal segment of exopod longer than wide, lateral margin proximally rounded.

Description. Head (Fig. 5, 6A,E,F). Eye region roughly oval in shape, fully sessile, lacking pigment and ocelli, maximum diameter 0.09 head depth, orientation of longest axis vertical; living specimens with large dendritic subcuticular white patches in eye region. Cuticle of head smooth, tubercles absent, with few long scattered setae. Head shape in dorsal view roughly subcircular, only slightly wider than long, width 0.9 pereonite 1 width. Head lateral profile forming smooth open curve. Cervical groove straight, weakly indented, extending variably above anterolateral margin of pereonite 1. Mandibular groove absent. Mandibular notch present. Clypeal notch present. Antennal notch present. Frontal process above antennule absent. Mouth field adjacent to posterior margin of head, maxillipeds inserting 0.08 head length from posterior margin of head.

Pereon (Fig. 5). Setation on dorsal surface sparse and scattered, seta thin and short. Dorsal surface of pereon smooth. Pereon only 10% wider than head. Pereonites much wider than long. Coxae on pereonites 2-7 with distinct sutures. Sternal processes absent. Gut with Ushaped typhlosole; hindgut caecae absent.

Pleonites (Figs 5, 7). Pleonites with large ventrolateral pleural plates extending well below level of pereonal coxae, basal region of pleopods not visible; pleonite 1 pleurae distinctly shorter than pleurae of pleonites 2- 5. Pleonites 1-5 depth 1.2-1.3, 1.5-1.6, 1.7-1.8, 1.7- 1.8, 1.3-1.4 pereonite 7 tergite depth, respectively. Pleonites 1-4 length subequal, less than half length of pleonite 5, width 0.68 total length in dorsal view.

Pleotelson (Fig. 7A-C,E). Lateral length 0.11-0.17 body length (mean = 0.14, N = 298), dorsal length 1.3 width (N = 2), lateral length 0.8-0.9 depth (N = 2), lateral median lobe length 0.1 pleotelson total length. Telsonic region distinct, trilobed, median lobe length 0.1 pleotelson length, lateral lobes shorter than median lobe in dorsal view. Tailpiece lateral lobe with 1 strong sensillate setae, median lobe with 4 robust sensillate setae. Dorsal uropodal cleft present, with several fine setae. Ventral margin anterior to uropods with 4-5 strong setae.

Antennula (Figs 5, 6A-C). Length 0.1-0.13 body length, with 7-8 articles in adult females, 9-10 articles in largest adult males. Articles 4 distinctly shorter than article 3. Article 6 sometimes dividing into two articles. Single tiny aesthetascs on article 6 to terminal article distally. Terminal article approximately oval, shorter than penultimate article, length 1.2-1.4 width.

Antenna (Figs 5, 6A,D) length 0.46 body length in male, 0.38 in female. Flagellum length 0.70-0.73 antenna length, with 24-25 articles in largest males, 14- 16 in females. Proximal propodal article absent, antennal scale absent on article 3. Article 5 subequal to article 4; article 6 subequal to articles 4 and 5.

Mouthfield (Fig. 6E,F). Clypeus consisting of broad bar, rounded laterally at mandibular fossae, width 0.69 head width. Labrum ventrally semicircular in anterior view, approximately same width as clypeus. Paragnaths (Fig. 8A) with distolaterally rounded lobes having medial setal row and thickened medial base covered with cuticular spinules.

Mandible (Fig. 8B-I). Palp length 0.88 mandibular body length; article 3 with (15-16) setae, setae finely setulate, lacking cuticular hairs or combs; articles 1- 2 with groups of long setae (longer than half article length) on dorsolateral margins. Incisor process with 4 teeth or cusps, 3 distally and one on ventral margin. Left lacinia mobilis with 3 teeth or cusps. Right lacinia mobilis absent. Spine row on projection with 9 bifurcate spines on both sides, distalmost spine distinctly separated from remaining spines. Molar process stout, heavily keratinised, broader than long; triturating surface heavily ridged with single posterior rounded tooth and posterior row of fine simple setae.

Maxillula (Fig. 9A-C). Medial lobe length 0.75 lateral lobe length; medial lobe 0.77 width lateral lobe width. Medial lobe with 4 plumose seta and 2 distally denticulate "accessory" setae, one on distolateral margin and one between central plumose setae. Lateral lobe with 12 stout denticulate setae, ventral face with three thin distally plumose setae, 2 proximal and one adjacent to stout denticulate setae.

Maxilla (Fig. 9D). Medial lobe width subequal to width of lateral lobes, extending anteriorly approximately same distance as lateral lobes. Lateral lobes with 7-8 setae having two rows of denticles each. Medial lobe with two basal rows of setae separated from single distal row by distinct gap but otherwise smoothly continuous; setae in ventral basal rows with single row of fine setules; setae in dorsal basal row with distinct base and smooth shaft; setae in distal row with row of teeth and row of fine setules.

Maxilliped ( Fig. 10 ). Epipod length 1.5 width, distal tip rounded, ventral surface and margins lacking setae, with lateral group of fine cuticular combs. Endite length 0.36 total basis length; distal tip with 4 subdistal biserrate setae on ventral surface; 3 coupling hooks (receptaculi) on medial margin; dorsal ridge with approximately 14 large, distally denticulate plumose setae. Palp insertion on basis with 1 plumose setae laterally, and 3 simple setae medially. Palp length 0.31 basis length, width (across article 2 & 3) 1.8 endite width; palp article 4 subcircular, length 1.1 width; palp article 5 length 0.87 width, length 0.8 article 4 length. Pereopod I (Fig. 11). Sexually dimorphic, length 0.32 body length in adult male, 0.25 in preparatory female. Pereopod of juvenile males resembling female condition. Dactylus length subequal to palm length in both sexes; row of fine setae along lateral axis; ventral margin with curved setae and distal cuticular fringe; fringe length 0.14 total protopod length in male, 0.20 in female; dactylar distal tip with one large dorsal claw and 1- 2 small accessory setae ventrally. Propodus length 0.24 pereopod length in adult male, 0.20 in female; length 1.0 width in adult male, 1.3 in female, dorsal margin protruding more in male. Propodus dorsal margin in male broadly rounded with proximally protruding section; in female, dorsal margin smoothly curving, not expanded proximally. Propodal palm without elongate spines or projections in both sexes. Propodal palm in male convex with 10-12 stout setae, 4 keratinised tooth-like setae on low humps and fringe of fine setae lateral to stout setae extending from dactylar insertion to ventral angle of palm. Propodal palm in female concave with 12-13 stout setae, no keratinised tooth-like setae and fringe of fine setae lateral to stout setae extending only half length of propodal palm. Basis length 2.5 width in males, 2.5 in females; dorsal margin with 2--4 elongate setae positioned proximally; ventrodistal margin with group of 4-7 elongate setae distinctly shorter than ischium.

Pereopod l/, 1II ( Fig. 12 ). Length 0.32, 0.32 body length. Basis length 0.29, 0.30 pereopod n, III length; length-width ratio 2.5, 2.3; dorsal ridge with 7-9 large simple setae and scattered penicillate setae. Carpus 0.13, 0.13 pereopod length; length-width ratio 1.5, 1.5; margin with 6, 6 broad based setae. Propodus length 0.14, 0.14 pereopod length; length 2.1, 2.1 width; articular plate present on distolateral margin; ventral margin with 2-3, 2 broad based setae. Dactyli distal tip with ventral spine adjacent to claw.

Pereopod IV ( Fig. 13 ). Sexually dimorphic, male pereopod IV subchelate with major hinges dactyluspropodus and propodus-carpus. Length 0.28 body length in male, 0.20 in female. Penicillate setae in male on dorsal margin of basis and anterodorsal margins of propodus, in female on dorsal margin of basis and anterodorsal margins of carpus and propodus. Dactylus in male subequal to propodal palm, with distal accessory spines in both sexes approximately one third length of primary claw in male, one fourth in female. Propodus length 0.14 pereopod length in male, 0.13 in female; articular plate present on posterior side of limb, length subequal to dactylar claw in male, shorter in female; approximately 9 broad based setae on ventral margin in male, two distinctly larger than others; female with only 1 broad based setae on ventral margin. Carpus length 0.13 pereopod length in male, 0.12 in female; approximately 7 broad based setae on ventral margin in male, 4 in female. Basis length 2.8 width in males, 2.6 in females; dorsal ridge rounded in cross section, with 3-5 setae positioned proximally.

Pereopods V, VI, VII ( Fig. 14 ). Length 0.25, 0.34, 0.36 body length. Penicillate setae present on dorsal ridge of basis, dorsodistal carpus, dorsodistal propodus. Dactylar claw length 0.38, 0.33, 0.30 dactylar length, distal accessory spines absent. Propodus length 0.14, 0.16, 0.16 pereopod length, articular plate on posterior side of limb present; distal margins with 2-4 elongate robust setae. Carpus length 0.14, 0.16, 0.16 pereopod length. Basis length 1.8, 1.6, 1.7 width; dorsal ridge not distinctly separated from basis shaft, in cross section rounded, with approximately 5, 10, 15 setae positioned along ridge.

Penes (Fig. 7C-D) strongly curved posteriorly, length 0.4 body width at pereonite 7, extending past midline and onto pleonite 1, shaft smooth, without setae, tapering, distally rounded.

Pleopods I-V (Figs 7C, 15, 16). Pleopods I-V lengths 0.15, 0.15, 0.15, 0.14, 0.13 body length in male; pleopods I-Ill lengths 0.11, 0.12, 0.10 body length in female. Exopods I-V length 2.6-2.7, l.8-2.2, l.5-l.7, l.6, l.6 width; exopod I uniarticulate; exopods 11-V biarticulate, distal articles II-V length 0.36 [n = 2], 0.33-0.35, 0.37, 0.34 exopod length; exopod I with no lateral proximal lobes, exopods 11-V with medial and lateral proximal lobes. Endopods I-V unilobed; length 2.4, l.6-l.8, l.6-l.8, l.8, 1.4 width; length 0.59, 0.58- 0.62, 0.69-0.54, 0.79, 0.60 exopod length; marginal setae absent. Protopods II-V with medial epipods, protopods Ill-V with lateral epipods. Pleopod I exopod in both sexes broadest at mid length, distally pointed, laterally broadly angular. Pleopod 11 endopodal appendix masculina (stylet) of male weakly curved, basal musculature pronounced; distal tip spatulate with 1 distal seta, length 0.38 pleopod 11 length.

Uropod (Fig. 7E-G). Total length l.2 pleotelson length. Protopod length 0.32 width, length 0.47 uropod length; dorsomedial ridge not produced, dorsomedial ridge setae present, dorsolateral margin setae present, 1 robust distally spinose setae on distoventral margin. Rami distal tips pointed and entire (terminal setae absent), cross-sectional shape round; endopod subequal to protopod length, with no robust setae on dorsal margin; exopod 0.76 endopod length, exopod with 1 robust seta on dorsal margin.

Remarks. Crenoicus buntiae differs from C. harrisoni (see diagnosis for details) in the form of the mature male pereopod IV, with C. buntiae having a more typical limb (compare Figs. 4C,D and l 3A,B). The second pleopod endopod also differs in males, and the maxillipedal epipod is also useful for identifying females or juveniles. The maxillipedal and pereopod IV setation can be used to separate C. buntiae from the Victorian species, with C. mixtus having many more setae on the pereopod IV ischium and C. shephardi having an obtusely pointed maxillipedal epipod. Certainty in identifying species of Crenoicus requires the inspection of adult males.

Figures

Fig. 10. Crenoicus buntiae n.sp. maxillipeds. A, D, P44395, adult male, bl 6.5 mm. B, C, AM P44349, adult male, bl 10.8 mm. A, left, ventral view. B, enlargement of endite ventral view. C, right palp, ventral view. D, left, medial view showing pappose denticulate setae on dorsal ridge. Scale bar 0.1 mm.

Fig. 12. Crenoicus buntiae n.sp. anterior pereopods. P44349, adult male, bl 10.8 mm. A, B, pereopods II-I1I, lateral view. Scale bar 0.4 mm.

Fig. 13. Crenoicus buntiae n.sp. pereopods IV, with enlargements of dactylus and propodus, lateral view. A, B, AM P44349, adult male, bl 10.8 mm. C, D, P4435I, preparatory female, bl 8.5 mm. Scale bar 0.2 mm.

Fig. 14. Crenoicus buntiae n.sp. posterior pereopods. P44349, adult male, bl 1O.S mm. A-C, pereopods V-VII, lateral view. Scale bar 0.2 mm.

Fig. 4. Crenoicus harrisoni Nicholls, 1944. Limbs. A-E, AM P4076, adult male, bl 12.7 mm. G, H: AM P44459, adult male neotype, bl 13.1 mm. A, left pereopod I; B, right pereopod n, dactylus and propodus; C, D: right pereopod IV; C, whole limb lateral view; D, palm, medial view. Scale bar 0.1 mm.