Speleophria nullarborensis, Karanovic, Tomislav & Eberhard, Stefan M., 2009

Karanovic, Tomislav & Eberhard, Stefan M., 2009, Second representative of the order Misophrioida (Crustacea, Copepoda) from Australia challenges the hypothesis of the Tethyan origin of some anchialine faunas, Zootaxa 2059, pp. 51-68 : 53-58

Speleophria nullarborensis sp. nov.

( Figs 1 – 21 )

Material examined. Holotype: adult female dissected on one slide ( WAM C37311). Paratypes: two females dissected on one slide each ( WAM C37312 & C37313); four females and six copepodids in 70% ethanol ( WAM C37314). Australia, Western Australia, Nullarbor region, Roe Plains, Nurina Cave (32°00’28”S 127°00’58”E), 1– 9 November, 2002, leg. S. Eberhard.

Description. HOLOTYPE FEMALE. Body length, excluding caudal setae, 0.493 mm. Habitus ( Figs 1–2 ) cyclopiform, relatively slender, with prosome/urosome ratio 1.7 and greatest width between first and second free prosomites. Body length/width ratio about 3.4 (dorsal view); cephalothorax about 2.1 times as wide as genital double-somite. Posterior corners of cephalothorax and free prosomites without pronounced lateral expansions, except those of fourth free prosomite, latter somewhat expanded posterolaterally but not pointed. Urosome narrow, with fifth prosomite narrower than genital double-somite. Preserved specimen colourless, nauplius eye absent. Rostrum sickle-shaped from lateral aspect ( Fig. 2 ), much longer than first antennular segment, triangular with rounded tip in frontal aspect.

Prosome ( Fig. 1 ) comprising cephalothorax and 4 free prosomites (first pedigerous somite not incorporated into cephalothorax), ovoid, about twice as long as wide (dorsal view); length ratio of prosomal somites, beginning with cephalothorax, 100: 27: 18: 20: 4. Cephalothorax 1.2 times longer than its greatest width, representing 34% of total body length; surface of cephalic shield, as well as those of free prosomites, without any sensilla or pores visible. Hyaline fringe of prosomites narrow and smooth.

Urosome ( Fig. 1 ) 5-segmented, with genital and first abdominal somites completely fused to form doublesomite. First urosomite ornamented with 2 large dorsal sensilla and smooth fringe dorsally and ventrally. Sclerotized joint between first urosomite and genital double-somite well developed, almost as pseudosomite ( Figs 7 – 9 ), but weakly sclerotized dorsally.

Genital double-somite ( Figs 7 – 9 ) with anterior part slightly inflated laterally, about 1.5 times as long as wide (dorsal view), ornamented with 2 lateral and 2 dorsal sensilla at first third and four posterolateral sensilla (two on each side). Single midventral copulatory pore relatively large, almost triangular when closed, situated at 3/5 of double-somite’s length; copulatory duct wide, short and rigidly sclerotized, directed dorsally and then anteriorly and attached to posterior part of seminal receptacle. Seminal receptacle small, rounded, representing only 30% of double-somite's width and 22% of its length. Paired ovipores located ventrolaterally as narrow slits at each side of copulatory pore, covered by reduced sixth legs and connected to receptacle via weakly sclerotized, narrow receptacle ducts.

Third urosomite ( Figs 7 – 9 ) ornamented with 2 posterolateral sensilla (one on each side), while fourth urosomite (preanal somite) unornamented. Preanal somite very short and narrow, only about 0.3 times as long as third urosomite and also much narrower than anal somite, acting like a clear urosomal constriction. Hyaline fringe of second to fourth urosomites narrow, not frilled and completely smooth. Anal somite with smooth, broad and convex anal operculum, representing 67% of somite's width and reaching its posterior margin; ornamented with 2 large dorsal sensilla and 2 posteroventral rows of minute spinules at base of each ramus.

Caudal rami ( Figs 7 – 9 ) subcylindrical, about as long as wide and somewhat shorter than anal somite, almost parallel, with very small space between them; representing only about 3.5% of total body length. Distal margin dorsally smooth and convex, ventrally straight and ornamented with small spinules, without cuticular pores visible. Only additional ornamentation consisting of several minute spinules posteriorly at base of distolateral seta. Armature consisting of 7 setae: 1 dorsal, 2 lateral and 4 apical. Dorsal seta short and smooth, 1.3 times as long as ramus, inserted close to posteromedial margin, uniarticulate at base and arising from small setophore. Proximolateral seta minute, smooth, positioned ventrolaterally at 1/4 of ramus’ length. Midlateral seta strong and bipinnate, twice as long as ramus and inserted laterally at 2/5 of ramus’ length. Innermost apical seta strong and bipinnate, nearly twice as long as outermost apical one (also bipinnate) and 3.6 times as long as ramus. Principal apical setae broken at breaking planes.

Antennula ( Fig. 3 ) short and slender, hardly reaching posterior 3/4 of cephalothorax, implanted on triangular pedestal, unornamented, incompletely 21-segmented. Intersegmental membrane less visible along thinner and highly armed anterior margin. First segment inflated, about as wide as long; twentieth segment 2.4 times as long as wide. Armature as follows: segment 1, 5 setae + aesthetasc; segments 2 – 4, 2 setae each; segment 5, 3 setae + aesthetasc; segment 6, 2 setae; segment 7, 9 setae; segments 8 – 9, 2 setae each; segment 10, 2 setae + aesthetasc; segments 11 – 14, 2 setae each; segment 15, 2 setae + aesthetasc; segments 16 – 17, 1 seta each; segment 18, 1 + 1 setae; segment 19, 1 + 1 setae + aesthetasc; segment 20, 1 + 1 setae; segments 21, 3 + 2 setae + aesthetasc. Aesthetasc hypertrophied on first and fifth segments, but slender on tenth, fifteenth, nineteenth and twenty-first segments. Only anterodistal seta on tenth segment hypertrophied. Setae without breaking planes or basal biarticualtions; most setae smooth.

Antenna ( Fig. 4 ) biramous, comprising coxa, basis, 2-segmented endopod and 6-segmented exopod (although first and second exopodal segments partly fused along anterior surface), with strong geniculation between first and second endopodal segments. Coxa and basis ovoid, unarmed and unornamented. Exopod nearly twice as long as coxa and basis combined, with second and last segments longest; setal formula 1.2.1.1.1.5. Endopod significantly longer than exopod, with both segments of about same length; first segment unornamented and armed with 2 medial setae; second segment ornamented with 4 transverse rows of slender setules, armed with 5 proximomedial and 7 apical setae. First endopodal segment 2.7 times as long as wide; second segment more than 3 times as long as wide.

Labrum ( Fig. 2 ) not mounted satisfactorily to allow detailed examination, but appears large and complex, armed with several short rows of long setules.

Mandibula ( Fig. 5 ) comprising coxa with well developed gnathobase and biramous palp; palp consisting of basis, 2-segmented endopod and indistinctly 4-segmented exopod. Coxal gnathobase cutting edge with isolated large tooth ventrally, plus row of 9 smaller, heterogeneous teeth and 2 dorsal setae. Basis large, 1.6 times as long as wide, unornamented and armed with 1 smooth seta medially. Endopod attached almost apically to basis (as its extension), with proximal segment somewhat shorter and wider than distal one, with setal formula 3.6. Exopod about as long as endopod, but somewhat wider, with setal formula 0.1.1.4.

Maxillula ( Fig.6 ) composed of large praecoxa, smaller coxa, large basis and 1-segmented endopod and exopod. Praecoxa with massive arthrite, armed with 2 slender setae on posterior surface and 12 elements along inner margin (9 spines and 3 setae); dorsalmost marginal seta pinnate, almost 3 times as long as any of the spines and twice as long as other pinnate seta; third marginal seta small. Coxa with well developed endite, bearing 2 spiniform and 3 slender setae; epipodite small, armed with 8 plumose setae. Basis with single slender, smooth outer seta; proximal endite well developed, somewhat longer than coxal endite, armed with 4 setae (3 pinnate, one of which is strong; 1 slender and smooth); distal endite indistinct, armed with 4 smooth setae. Endopod half as long as basis, armed with 5 smooth setae along inner margin and cluster of 6 setae apically. Exopod slightly larger than basis (excluding endites), twice as large as endopod, armed with 2 outer, 4 apical and 3 inner plumose setae. Exopod ornamented with long spinules along both inner and outer margins; basis ornamented only along dorsal side; other segments unornamented.

Maxilla ( Fig. 10 ) 6-segmented, comprising praecoxa, coxa, basis and 3-segmented endopod. Praecoxa quadriform, about as wide as long, unornamented, with 5 setae on proximal and 3 setae on distal endite. Coxa much smaller than praecoxa, also unornamented, armed with 3 setae on each endite. Basis slightly shorter than praecoxa, with strong proximal and small distal endite; distal endite armed with 3 slender setae, proximal one armed with 3 slender setae and 2 claw-like spiniform setae. All setae on praecoxa, coxa and basis pinnate. Endopodal segments very short, each armed with claw-like spiniform seta almost as long as entire maxilla; first and second segment additionally armed with slender smooth seta each, third segment additionally armed with 3 slender setae (2 smooth, 1 unipinnate).

Maxilliped ( Figs 11 – 12 ) slender, 8-segmented, composed of syncoxa, basis and 6-segmented endopod. Syncoxa nearly 3 times as long as greatest width, unornamented, with proximal praecoxal endite weakly discernible, distal praecoxal and both coxal endites well developed; armature formula 1.2.3.3. Basis slightly shorter than wide, 0.3 times as long as syncoxa, ornamented with several long spinules on inner margin and armed with 3 pinnate setae. Endopod slender and twice as long as basis; proximalmost segment shortest, distalmost segment longest; armature formula 1.2.2.2.3.5.

All swimming legs ( Figs 13 – 19 ) with 3-segmented exopod and endopod; their armature formula as follows:

Coxa Basis Exopod Endopod

Leg 1 0-1 I-I I-0; I-1; III,I+1,2 0-1; 0-1; 1,2,2

Leg 2 0- 1 I-0 I-1; I-1; II,II,4 0-1; 0-2; 1,2,3

Leg 3 0- 1 I-0 I-1; I-1; II,II,4 0-1; 0-2; 1,2,3

Leg 4 0- 1 I-0 I-1; I-1; II,II,3 0-1; 0-2; 1,2,2

All intercoxal sclerites without surface ornamentation, with slightly concave distal margin. Coxae unornamented, except posterior row of minute spinules on first leg, armed with plumose seta at inner distal corner. Basis of each leg also unornamented, armed with strong spine (first and second legs) or slender seta (other legs) on outer margin; basis of first leg with additional spine on distal inner corner, shorter than first endopodal segment; inner distal corners of second, third and fourth leg pronounced as blunt processes; similar but much sharper process also between exopod and endopod. All exopodal spines serrate on both sides. All exopodal and endopodal setae on first leg slender and plumose, except outer apical seta on third exopodal segment, plumose along inner margin and serrate along outer. Second, third and fourth legs with some setae plumose proximally and serrate distally; number of these setae smallest on second leg, largest on fourth (where 6 out of 8 endopodal setae ornamented like this). All endopodal segments with hair-like spinules along outer margin and all exopodal segments with minute spinules along outer margin. Third endopodal segment of fourth swimming leg about 1.7 times as long as wide; apical elements subequal, 2.2 times as long as segment.

Fifth leg ( Fig. 20 ) with small intercoxal sclerite fused basally to somite, 4-segmented, comprising coxa, basis and 2-segmented exopod. Coxa about 1.5 times as wide as long, unarmed and unornamented. Basis quadriform, somewhat longer than coxa, unornamented, but armed with unipinnate seta on outer distal corner. First exopodal segment narrower proximally and somewhat longer than basis, armed with bipinnate seta. Second exopodal segment longest, about 1.7 times as long as wide, 1.7 times as long as coxa, also unornamented, but armed with 3 setae; innermost subapical seta strongly serrate and spiniform, about as long as segment; inner apical seta plumose, 1.7 times as long as segment; outer apical seta bipinnate and somewhat shorter than segment.

Sixth leg ( Figs 9 and 21 ) not clearly distinct, represented by trapezoidal cuticular plate, armed with inner smooth and minute spine, fused to plate, and 2 bipinnate setae; outermost seta 2.3 times as long as middle seta and 5 times as long as innermost spine.

MALE. Unknown.

Variability. Body length of females ranges between 0.474 mm and 0.496 mm (average = 0.481 mm; n = 7). The third exopodal segment of the first swimming leg in the holotype has the proximal two outer spines spaced very close to each other on one side ( Fig. 13 ), while the opposite leg has a normal appearance ( Fig. 14 ). No other forms of variability or asymmetry were observed.

Etymology. The specific name comes from the Nullarbor region, where the type material was collected. The name is an adjective for place, made with the Latin suffix -ensis.

Affinities. Among the misophrioid genera, the new species fits well into the diagnosis of the genus Speleophria Boxshall & Iliffe 1986 , as emended by Jaume & Boxshall (1996a), by its segmentation and armature of the mouth appendages, as well as by the shape, armature and ornamentation of the majority of body parts, except for the first leg endopod segmentation. A 3-segmented endopod of the first swimming leg is found in, beside our new species, the speleophriid clade (sensu Boxshall & Jaume 2000a) containing the genera Archimisophria Boxshall, 1983 , Boxshallia Huys, 1988 and Expansophria Boxshall & Iliffe, 1987 . Indeed, Boxshall & Halsey (2004) used this character alone in their speleophriid key to separate these three taxa from the other four genera having a 2-segmented leg 1 endopod ( Huysia Jaume, Boxshall & Iliffe, 1998 , Protospeleophria Jaume, Boxshall & Iliffe, 1998 , Speleophria and Speleophriopsis Jaume & Boxshall, 1996 ). The plesiomorphic segmentation of the first leg endopod is, however, not enough to place our new species with the Archimisophria -Boxshallia-Expansophria clade, because our new species: a) differs from the latter three taxa in a number of very important characters that include armature and segmentation of the antenna, mandibula, maxilla, fifth leg, etc.; and b) shares many morphological characters with one of the Speleophria members, that we briefly considered a possibility of its subspecific status. It should be noted that the convenient division of speleophriid genera in Boxshall & Halsey’s (2004) key is not supported by Boxshall & Jaume’s (2000a) cladistic analysis of misophrioid genera, which showed that Speleophriopsis stands as a sister group to all other six speleophriid genera. Also the absence of the intersegmental membrane between the middle and distal endopodal segments of the first leg was not followed by the reduction of armature, as all Speleophria species have seven setae in total on the endopod.

So far only four Speleophria species are valid members of the genus, all of them described from anchialine caves: S. bivexilla Boxshall & Iliffe, 1986 from Bermuda, S. gymnesica Jaume & Boxshall, 1996 from the Balearic Islands, S. bunderae Jaume, Boxshall & Humphreys, 2001 from north-western Australia and S. mestrovi Kršinić, 2008 from Croatia (see Boxshall & Iliffe 1986; Huys & Boxshall 1991; Jaume & Boxshall 1996a; Jaume et al. 2001; Kršinić 2008). Two other anchialine species were originally described in this genus ( S. scottodicarloi Boxshall & Iliffe, 1990 from Bermuda and S. campaneri Boxshall & Iliffe, 1990 from Palau Islands), but were later transferred to a newly established genus Speleophriopsis by Jaume & Boxshall (1996a). Speleophria nullarborensis sp. nov. can be easily distinguished from its four congeners by its plesiomorphic 3-segmented endopod of the first swimming leg ( Fig. 13 ), which is 2-segmented in other species, and the unusually long innermost apical seta on its caudal rami ( Fig. 7 ; nearly twice as long as the outermost apical seta). Another character that easily distinguishes our new species, and seems to be an autapomorphic feature, is its constricted preanal somite ( Figs 7 – 9 ). This character was not variable in any of the seven adult females examined. Speleophria bivexilla differs additionally from S. nullarborensis sp. nov. by its lateral armature element on the second exopodal segment of the female fifth leg (absent in the new species, as well as in the other three congeners), as well as by some other characters in the armature of cephalic appendages and the fourth swimming leg. The north-western Australian S. bunderae shares an unusually reduced proximolateral seta on each caudal ramus with the new species, but can be distinguished from it additionally by a number of minor characters, i.e.: antennula with hypertrophied seta also on the 14th segment and the penultimate segment much longer, antenna with only four proximomedial setae on the second endopodal segment (five in the new species), maxillula without outer seta on the basis, maxilla with a minute seta on the first two endopodal segments, more heavily ornamented swimming legs and more pointed posterolateral corners of the fourth free prosomite. The Croatian S. mestrovi can be easily distinguished from its congeners by a bulbous process on the first antennular segment, and differs additionally from S. nullarborensis sp. nov. by the size and ornamentation of anal operculum and genital double-somite. The Mediterranean S. gymnesica shares the greatest number of morphological characters with the new species and can be distinguished from it by the plesiomorphic armature of the third exopodal segment of the fourth leg, in addition to the three previously mentioned unique characters of S. nullarborensis sp. nov. It should be stressed here that morphological differences between Speleophria species, and especially between S. nullarborensis sp. nov. and S. gymnesica , are indeed very small. Unfortunately, males of only two Speleophria species ( S. bunderae and S. mestrovi ) are known, and a meaningful cladistic analysis would be very hard to perform here without male characters. Instead, we present below a key to species.

Figures

FIGURES 1 – 6. Speleophria nullarborensis sp. nov., holotype female: 1, habitus, dorsal view; 2, habitus, lateral view; 3, antennula; 4, antenna; 5, mandibula; 6, maxillula. Scales = 0.1 mm.

FIGURES 7 – 12. Speleophria nullarborensis sp. nov., holotype female: 7, abdomen, ventral view; 8, abdomen, dorsal view; 9, abdomen, lateral view; 10, maxilla; 11, syncoxa and basis of maxilliped; 12, endopod of maxilliped. Scale = 0.1 mm.

FIGURES 13 – 21. Speleophria nullarborensis sp. nov., holotype female: 13, first swimming leg; 14, third exopodal segment of first leg; 15, basis of second swimming leg; 16, third endopodal segment of second swimming leg; 17, third endopodal segment of third swimming leg; 18, third exopodal segment of third swimming leg; 19, fourth swimming leg; 20, fifth leg; 21, sixth leg. Scales = 0.1 mm.