Paranitocrella bastiani, Tang & Knott, 2009

Tang, Danny & Knott, Brenton, 2009, Freshwater cyclopoids and harpacticoids (Crustacea: Copepoda) from the Gnangara Mound region of Western Australia, Zootaxa 2029, pp. 1-70 : 50-59

Paranitocrella bastiani sp. nov.

( Figs 26–31)

Type material. Holotype ♀ ( AM P.78924), allotype ♂ ( AM P.78925) and 22 paratypes (11 ♀, 6 ♂ and 1 copepodid in alcohol; 2 ♀ and 2 ♂ dissected and mounted on one slide each) ( AM P.78926–P.78932), Gilgie Cave ( YN27 ), Yanchep National Park, Western Australia (31°34'07''S, 115°41'18''E), 28 August , 1994.

Other material examined. Boomerang Cave ( YN99 ), Yanchep National Park, Western Australia (31°32'33''S, 115°41'24''E): 1 ♂, 17 July , 1992; Cabaret Cave ( YN30 ), Yanchep National Park , Western Australia (31°32'31''S, 115°41'24''E): 1 ♂, 29 August , 1993; Carpark Cave ( YN18 ), Yanchep National Park , Western Australia (31°33'08''S, 115°41'08''E): 18 ♀ (1 dissected and mounted on slide), 14 ♂ (1 dissected and mounted on slide) and 1 copepodid, 31 October , 1996; Gilgie Cave ( YN27 ), Yanchep National Park , Western Australia (31°34'07''S, 115°41'18''E): 3 ♀, 7 ♂ and 2 copepodids, 17 March , 1993; 5 ♀, 5 ♂ and 1 copepodid ( AM P.78933), 27 November, 1996; Twilight Cave ( YN194 ), Yanchep National Park , Western Australia (31°34'05''S, 115°41'21''E): 2 ♂, 27 August, 1994; 3 ♀ and 1 ♂, 27 November, 1996 .

Description of female. Total body length (measured from tip of rostrum to posterior margin of caudal rami), based on 4 specimens, 425–430 µm, mean 428 µm; largest width (80 µm) measured at posterior end of cephalothorax. Body ( Fig. 26A) cylindrical, without discrete delineation between prosome and urosome. Prosome composed of cephalothorax and 3 free pedigerous somites; all prosomal tergites with sensillae and smooth hyaline frill. Urosome ( Figs 26A–B) comprised of fifth pedigerous somite, genital double-somite and 3 free abdominal somites. Urosomites 1–4 with minutely serrated hyaline frill forming rectangular lappets. Genital double-somite wider (60–65 µm) than long (45–55 µm), with paired anteroventral spinular rows and 2 medioventral spinular rows; original segmentation represented by dorsal line furnished with minutely spinulated frill. Genital field situated anteriorly on genital double-somite, with large median copulatory pore and chitinized copulatory duct leading to pair of lobate seminal receptacles; median genital pore covered by modified sixth legs. Postgenital somites 1–2 with paired ventrolateral spinular rows, numerous medioventral spinular rows and posteroventral spinular row. Anal somite ( Figs 26B, 27A) with paired lateral, anteroventral and anterodorsal spinular rows, spinules along hind margin of anal cleft and spinules at insertion point of each caudal ramus; anal operculum with 7–8 large spinules along slightly convex distal margin.

Caudal ramus ( Figs 26B, 27A) short, about 1.6 times as long as wide, armed with 7 setae. Seta I and II closely set near outer subdistal margin; seta II over 2 times as long as seta I. Setae III and VII longer than caudal ramus, inserted at outer and inner distal angle, respectively. Seta VI about 1.6 times as long as seta I. Spinules present at insertion point of setae III, V and VII. Setae IV and V spinulate, with proximal breaking planes; other setae naked. Seta VII basally tri-articulate.

Rostrum ( Fig. 27B) elongated, demarcated at base, with truncate tip and 2 dorsal sensillae; longer than first antennulary segment.

Antennule ( Figs 27C–E) 8-segmented, with armature as follows: 1, 8, 6, 4+ae, 2, 2, 4, and 7. Segment 1 with spinular row, large tubular pore and distal spiniform seta. Segments 2–8 without surface ornamentation and armed with naked elements. Segment 8 with 2 apical setae fused at base.

Antenna ( Fig. 27F) 4-segmented, comprising coxa, basis and 2-segmented endopod. Coxa naked and unarmed; basis with 2 large medial spinules and inner oblique spinular row. Exopod 1-segmented, cylindrical, armed with distal pinnate seta. Proximal endopodal segment naked and unarmed. Distal endopodal segment as long as proximal segment; furnished with 2 lateral hyaline frills and large spinules along medial margin; armed medially with 2 spines and naked seta and apically with 1 pilose, 1 naked and 5 geniculate setae (lateralmost geniculate seta fused basally with pilose seta).

Labrum ( Fig. 27G) subtriangular, with denticulate membrane on distal margin.

Mandible ( Fig. 28A) composed of coxa and 2-segmented palp. Coxal gnathobase with numerous unicuspidate teeth along distal margin and unilaterally denticulate seta on inner distal angle. Proximal and distal segments of palp equal in length; proximal segment unarmed and naked; distal segment armed with 2 pairs of basally fused setae.

Maxillule ( Fig. 28B) composed of praecoxa and 3-segmented palp. Praecoxal arthrite bears proximal spinules near inner margin, 2 medial setae, 2 anterior surface setae and 6 apical elements (1 unipinnate; 3 naked; 2 highly chitinized, with minute spinules along distal half of inner margin). Coxal endite elongated, with anterior surface spinules and 3 apical setae. Basis ¾ length of coxa, bears subapical naked seta and 4 apical naked setae. Endopod 1-segmented, small, armed with 2 unequal naked setae. Exopod absent.

Maxilla ( Fig. 28C) 3-segmented, composed of syncoxa, allobasis and 1-segmented endopod. Syncoxa unornamented, with proximal endite represented by pilose seta; distal endite bears 1 pectinate and 2 naked apical setae. Allobasis drawn out into long claw furnished with spinules along distal half of inner margin; with proximal pectinate seta on posterior surface. Endopod 1-segmented, inserted on anterior surface of allobasal claw and armed with 2 long distal setae.

Maxilliped ( Fig. 28D) 3-segmented, comprising syncoxa, basis and 1-segmented endopod. Syncoxa stout, with proximal spinules on posterior surface and distal naked seta. Basis equal in length to endopod, with few apical spinules along outer margin. Endopod drawn out into long claw furnished with denticles along distal half of inner margin; bears proximal naked seta.

Legs 1–4 biramous ( Figs 28E–F, 29A–B); leg 1 with trimerous rami; legs 2–4 with trimerous exopod and bimerous endopod. Armature on rami of legs 1 to 4 as follows (Roman numerals = spines; Arabic numerals = setae):

Leg 1 ( Fig. 28E) intercoxal sclerite slightly wider than long, without surface ornamentation. Coxa with 3 spinular rows (2 with long spinules; 1 with minute spinules) on anterior surface. Basis with 3 groups of long spinules on anterior surface; outer spine with subapical flagellate element; inner spine short, furnished with few denticles. Outer distal angle of proximal and middle exopodal segments produced forming rounded spinulose protuberance. Setae on terminal exopodal segment geniculate. Inner seta on proximal endopodal segment highly chitinized, furnished with spinules distally. Middle seta on terminal endopodal segment geniculate. All spines on rami denticulate. Proximal and distal exopodal segments and middle endopodal segment with naked inner margin.

Leg 2 ( Fig. 28F) intercoxal sclerite about 1.6 times as long as wide, without surface ornamentation. Coxa with 3 spinular rows (2 contains minute spinules; 1 with long spinules) on anterior surface. Basis similar to that of leg 1, except without spinules and spine on inner margin. Exopod ornamented as in leg 1, except with additional spinular row on inner distal angle of proximal and middle segments; inner apical seta on terminal segment naked, reduced, about 0.35 times as long as adjacent spine. Distal endopodal segment with large spinules flanking insertion point of apical spine.

Leg 3 ( Fig. 29A) identical to leg 2, except basis with outer setulate seta.

Leg 4 ( Fig. 29B) similar to leg 3, except basis with outer naked seta and terminal exopodal segment bears 2 more elements.

Leg 5 ( Fig. 29C) biramous. Basoendopod with setophore bearing outer basal seta; endopodal lobe with median pore, few lateral spinules, 3 distal setae (2 spinulate, 1 spiniform) and inner spiniform seta. Exopod about 1.9 times as long as wide, with 3 lateral naked setae, weakly spinulate apical seta and inner cuticular pore (position of pore opening indicated by arrowhead in Fig. 29C).

Legs 6 ( Fig. 26B) reduced, completely fused, forming genital operculum armed with 1 pinnate seta on either side.

Male. Total body length (measured from tip of rostrum to posterior margin of caudal rami), based on 4 specimens, 395–420 µm, mean 407.5 µm; largest width (75 µm) measured at posterior end of cephalothorax. Prosome composed of cephalothorax and 3 free pedigerous somites; ornamented as in female. Urosome comprised of fifth pedigerous somite, genital somite and 4 free abdominal somites. Genital somite ( Fig. 30A) wider than long, with minutely serrated hyaline frill. Postgenital somites ( Fig. 30A) ornamented as those of female, except without paired lateral spinular rows on first and second somites. Caudal ramus ( Fig. 30A) about 1.7 times as long as wide; armed and ornamented as in female.

Antennule ( Figs 30B–D) 10-segmented, haplocerate, with geniculation between segments 7 and 8. Armature as follows: 1, 9, 7, 2, 9+ae, 2, 3, 4, 4, and 8. Segment 1 with spiniform seta, spinular row and tubular pore as in female. Short spiniform seta present on segment 4. Short spinulate seta(e) present on segments 5–7. Aesthetasc and adjacent seta on segment 5 fused basally. One small and 2 large spines present on inner margin of segment 8. Two apical setae on segment 10 fused basally.

Inner basal spine of leg 1 ( Fig. 30E) modified into stout, apically barbed spine.

Terminal endopodal segment of leg 2 ( Fig. 30F) without large spinules near insertion point of apical spine.

Terminal endopodal segment of leg 3 ( Fig. 30G) with apical fringe of minute spinules and extra naked seta; apical spine slightly deflected outward and lacks large spinules at insertion point.

Leg 5 ( Fig. 31A) biramous, with basoendopods fused medially. Basoendopod with setophore bearing outer basal seta; endopodal lobe with median pore and 2 apical elements. One dissected paratype with abnormal basoendopod ( Fig. 31B). Exopod about 1.9 times as long as wide, with 3 lateral naked setae, weakly spinulate apical seta, distomedial cuticular pore (position of pore opening indicated by arrowhead in Fig. 31A) and proximomedial spinulate seta.

Leg 6 ( Figs 30A, 31C) asymmetrical (both sinistral and dextral formations present) and unornamented; each side represented by articulating operculum armed with 2 setae on genital somite.

Etymology. This species is named for Mr. Lex Bastian, in recognition of his speleological contributions to Western Australia and long-term involvement with the Yanchep Caves invertebrate monitoring program.

Remarks. The new species described herein shows a close resemblance to members of the genus Nitocrella Chappuis, 1923 (sensu Petkovski 1976), Novanitocrella Karanovic, 2004 and Abnitocrella Karanovic, 2006 in having a 3-segmented endopod on leg 1, armature of I-0 on the proximal exopodal segment of legs 2 to 4, two outer spines on the distal exopodal segment of legs 1 to 4, bimerous endopod on legs 2 to 4 and sexually dimorphic leg 3. The new species also shares an apomorphic 1-segmented antennal exopod armed with an apical seta with Nitocrella japonica Miura, 1962 and Abnitocrella halsei Karanovic, 2006 , armature of I-0 on the middle exopodal segment of legs 2 to 4 with Nitocrella kunzi Galassi & Pesce, 1997 and both Novanitocrella species , armature of 0-0; I on the endopod of legs 2 to 4 with Nitocrella paceae Pesce, 1980 and N. africana Chappuis, 1955 , a plesiomorphic leg 5 in both sexes with Novanitocrella and some Nitocrella species and sexually dimorphic leg 2 with Nitocrella . Despite these shared features, the new species here attributed to Paranitocrella gen. nov. contains a suite of characters not known to occur in Nitocrella , Novanitocrella and Abnitocrella .

The outer margin of the bases of legs 1 and 2 is armed with a spine in Nitocrella , Novanitocrella , A. halsei (this element is absent in the first two leg pairs of Abnitocrella eberhardi Karanovic, 2006 ) and Paranitocrella gen. nov. This outer element is commonly furnished with minute denticles along the margins in the first three taxa. In Paranitocrella gen. nov., this outer element also bears an accessory flagellate element subapically. This accessory structure is not unique to the new species, as it has evolved independently in unrelated harpacticoid species, such as the mesopsammic latiremid harpacticoid Delamarella obscura Huys, Karaytuǧ & Cottarelli, 2005 (see Huys et al. 2005: figs 5A–B).

The inner apical seta on the distal exopodal segment of legs 2 to 4 is invariably pinnate and as long as the outer apical element in Nitocrella , Novanitocrella and Abnitocrella . This inner element is naked and reduced, being about one-third as along as the outer apical element, in Paranitocrella gen. nov. This apomorphy is, however, not unique to the new species, as it has been documented in members of the ameirid genus Pseudoleptomesochrella Lang, 1965 (see Sak et al. 2008: figs 3C–E).

Sexual dimorphism in the distal endopodal segment of leg 3 is similar between A. halsei (the male has yet to be described for A. eberhardi ) and representatives of Nitocrella in that the length of one of the two apical elements on the distal segment is altered in the male. For example, the inner element is considerably shorter in the male than in the female in some Nitocrella species , such as N. ensifera Cottarelli, Bruno & Berera, 2007 and N. japonica , but conversely, longer in the male than in the female in A. halsei ( Miura 1962a; Karanovic 2006; Cottarelli et al. 2007). Dimorphism in the distal endopodal segment of leg 3 in Novanitocrella aboriginesi Karanovic, 2004 (the male has yet to be described for N. aestuarina Coull & Bell, 1979 ) and Paranitocrella gen. nov. is profoundly different from that of Nitocrella and A. halsei . In male N. aboriginesi , the distal segment is more elongate, and of the three rather than two apical elements, the outer element is modified into a curved spine and the inner seta is considerably reduced as compared to that in the female ( Karanovic 2004a). The distal endopodal segment in male Paranitocrella gen. nov., in contrast, lacks large spinules at the insertion point of the apical spine and bears additional structures, such as an apical fringe of minute spinules and, more significantly, an inner subapical naked seta.

The fundamental differences, as discussed above, between the new species and Nitocrella , Novanitocrella and Abnitocrella are, in our opinion, sufficient to justify the establishment of a new ameirid genus. Paranitocrella gen. nov. can be distinguished from these related genera by the following combination of characters: 1) urosome with well developed hyaline frill forming rectangular lappets; 2) antenna with 1- segmented exopod armed with an apical seta; 3) outer spine on the bases of legs 1 and 2 with accessory flagellate element; 4) legs 1 to 4 without inner seta on proximal and middle exopodal segments; 5) legs 2 to 4 with reduced inner apical seta on the terminal exopodal segment; 6) legs 2 to 4 with 2-segmented endopods, of which the proximal segment is unarmed and the distal segment bears an apical spine; 7) well developed leg 5 in both sexes; and 8) male leg 3 endopod bears an additional apical fringe of minute spinules and inner subapical naked seta on the distal segment.