Neoleptastacus spinicaudatus, NICHOLLS, 1945

Sak, Serdar, Huys, Rony & Karaytuğ, Süphan, 2008, Disentangling the subgeneric division of Arenopontia Kunz, 1937: resurrection of Psammoleptastacus Pennak, 1942, re-examination of Neoleptastacus spinicaudatus Nicholls, 1945, and proposal of two new genera and a new generic classification (Copepoda, Harpacticoida, Arenopontiidae), Zoological Journal of the Linnean Society 152, pp. 409-458 : 435-443

NEOLEPTASTACUS SPINICAUDATUS NICHOLLS, 1945

Original description: Nicholls (1945): pp. 22–23; textfigure 3.

Type locality: Nicholls (1945) collected the species from two sandy beaches some 500 km apart on the coast of Western Australia; the first, Leighton Beach (in the region of Perth), was sampled in October 1939; samples from the second site, locally known as ‘ Back Beach’ at Dongarra , were taken in March 1940. Nicholls did not specify a type locality; however, all NHM syntypes came from sand washings at the Dongarra site, which is regarded here as the locus typicus .

Material examined: Syntype series consisting of: (1) one ♀ dissected on one slide ( NHM reg. no. 1947.10.3.8); (2) one ♂ dissected on one slide ( NHM reg. no. 1947.10.3.9); and (3) one vial containing 25 ♀♀ and one ♂ in alcohol [besides a mixture of Psammopsyllus operculatus Nicholls, 1945 (one ♀ and one ♂), Ectinosomoides longipes Nicholls, 1945 (one ♀), and a new species of arenopontiid described below as Onychopontia nichollsi (ten ♀♀ and one ♂)]; leg. A.G. Nicholls on 25–26 March 1940.

Redescription

Female: Total body length from tip of rostrum to posterior margin of caudal rami: 274–295 M m (mean = 281 M m, N = 15). Maximum width: 33 M m (mean of 15 individuals = 32 M m), measured at posterior margin of cephalothorax. Body: slender and cylindrical, without clear distinction between prosome and urosome ( Fig. 13A, B). Hyaline frills of thoracic somites weakly developed and crenulated; those of genital double-somite and free abdominal somites strongly developed and consisting of rectangular digitate lappets ( Figs 13A, B, 14A, B, E). Genital doublesomite ( Figs 13A, B, 14A) as long as wide; without chitinous ribs marking original segmentation; with one middorsal, two lateral, and six ventral pores ( Fig. 15F). Anal somite ( Fig. 14A, C, E): with two ventral and two lateral pores; ventral posterior margin with medial spinule rows. Anal operculum: smooth ( Fig. 14F). Anus positioned subterminally between caudal rami.

Caudal rami ( Fig. 14C–F): approximately 2.2 times longer than maximum width (measured in dorsal view), tapering posteriorly; with one pore near ventral proximal margin ( Fig. 14E), and two pores laterally near insertion site of seta II, and at base of distal spinous process ( Fig. 14C); outer distal corner produced into posteriorly directed recurved spinous process; mediodorsal surface with small spur-like process at base of seta VII, accompanied by minute accessory process near inner margin ( Fig. 14F). Armature consisting of seven setae: seta I, small; setae II and III, long and naked, the latter displaced dorsally; seta IV, short, sparsely pinnate, located between seta V and spinous process; seta V, long, and with fracture plane; seta VI small, naked, and located at inner distal corner; seta VII, not foliaceous and triarticulate at base.

Rostrum ( Fig. 16B): small, broadly subtriangular, apical part lobate and offset, with two delicate sensillae and one midventral pore.

Antennule ( Fig. 16A): long, six-segmented. Segment 1: with a tiny seta near anterodistal margin. Segment 2: longest, about 2.5 times longer than wide. Segment 4: with long aesthetasc (25- M m long), fused at base with seta. Distal segment: with seven naked setae (two of which are spatulate), and with apical acrothek consisting of short aesthetasc (10- M m long) and two slender setae. Armature formula: 1-[1], 2-[7 + 1 plumose], 3-[4], 4-[(1 + ae)], 5-[1], 6-[7 + acrothek].

Antenna ( Fig. 17D): coxa, small and bare. Basis and proximal endopod segment incompletely separated by surface suture, without armature or ornamentation. Exopod: minute, one-segmented, with one long bare seta. Free endopod: with distal hyaline frill; abexopodal margin with two spinular rows and two bare, curved spines; apical margin with two geniculate setae, two bare spines and one composite element consisting of spinulose, geniculate seta and small, basally fused seta.

Labrum ( Fig. 16C): sclerotized and wide; with blunt spinules bilaterally around distal margin.

Mandible ( Fig. 17E): gnathobase elongate, about as long as palp; with several curved, minute teeth and one tiny recurved seta at dorsal corner. Palp consisting of elongate, unisetose basis and one-segmented endopod with one inner, two outer, and two apical setae.

Maxillule ( Fig. 16D): praecoxal arthrite with one surface seta; distal margin with five spines and two setae. Coxal endite: cylindrical, with two recurved spines. Basis: elongate, with rami completely incorporated; basal armature consisting of three apical setae. Exopod and endopod: represented by one and three setae, respectively.

Maxilla ( Fig. 17F): syncoxa with two cylindrical endites; proximal endite with three setae (one fused at base); distal endite with two setae (one fused at base). Allobasis: drawn out into long claw with one accessory seta. Endopod: one-segmented; with three setae. All elements are naked.

Maxilliped ( Fig. 16E): syncoxa longer than wide, unarmed, with few spinules. Basis: elongate and unarmed. Endopod: with small accessory seta and slightly curved claw, bearing strong, subterminal spinule.

P1 ( Fig. 15A): intercoxal sclerite long and rectangular. Praecoxa: triangular and naked. Coxa: with few spinules on posterior surface. Basis: with spinules around base of endopod, and at inner and outer distal corners; anterior surface with a pore and a small inner seta. Exopod: three-segmented; exp-1 and exp-2 with spinules around outer margin; exp-1 longest, with short, bare outer spine; exp-2 without outer element; exp-3 with short, bare outer spine, a curved unipinnate spine, and two geniculate setae distally. Endopod: two-segmented, not prehensile, as long as exopod; enp-1 with a serrate inner seta at about halfway along the segment length, and coarse spinules along outer margin; enp-2 slightly shorter than enp-1, with a short bare outer spine and a geniculate inner seta.

P2–P4 ( Fig. 15B–D): intercoxal sclerites naked. Praecoxae: very small and bare. Coxae: squarish and without ornamentation. Bases: smaller than coxae, with a spinular row near base of endopod, and a few spinules around outer corner in P2 and P4; anterior surface with a pore in P2 and P4; outer basal seta absent in P2, but present and bare in P3–P4. Exopods: three-segmented; segments with coarse spinular ornamentation, as illustrated; inner distal seta of exp-3 sparsely bipinnate, all other elements unipinnate or bare, except for inner seta of P4 exp-3 being serrate. Endopods: two-segmented; P2–P4 enp-1 about 1.1, 2.3, and 3.8 times longer than their respective distal segments, with coarse spinules along outer margin, and a few tiny spinules near inner distal corner. P2 enp-2: with a long, apically serrate, backwardly directed seta near proximal margin. P3 enp-2: with a short bipinnate spine apically and outer distal spine fused to segment forming bare spinous process. P4 enp-2: with large apically serrate seta, fused at base, and short unipinnate seta at outer distal corner. Spine and seta formula as follows:

Exopod Endopod P2 0.0.021 0.120

P3 0.0.021 0.020

P4 0.0.121 0.020

Fifth legs ( Fig. 15E): closely set together, but not touching in ventral midline. Baseoendopod and exopod fused, forming a rectangular plate; anterior surface with two pores. Inner distal corner: with strong spinous process (homologous to inner spine); process minutely bipinnate, with subapical flagella, and delimited at base on posterior surface. Distal margin with plumose outer basal seta, one naked seta, and two short, equally long, bipinnate spines.

Genital field positioned centrally on ventral surface of genital double-somite ( Fig. 14A). Genital apertures ( Fig. 15F) fused, forming median common slit; closed off by fused P6 forming operculum with two minute spinous processes on either side; copulatory pore large (arrowed in Fig. 15F), leading to short copulatory duct, and surrounded by three pairs of pores; seminal receptacles difficult to discern.

Male: Total body length from tip of rostrum to posterior margin of caudal rami: 272–277 M m (N = 2). Maximum width: 30–31 M m (N = 2), measured at cephalothorax. Body ornamentation ( Fig. 14B): essentially as in female. Sexual dimorphism: in antennule, genital segmentation, P5 (weak), and P6. Spermatophore length: approximately 30 M m.

Antennule ( Fig. 17A–C): nine-segmented, haplocer; geniculation between segments 7 and 8. Segment 1 with few spinules on anterior surface; segment 2 longest and about 1.9 times longer than wide; segment 4 an incomplete sclerite with one tiny element; segment 5 with two setae, plus long aesthetasc (43- M m long), fused basally to a slender seta; segment 6 with two short setae; segment 7 with two modified spines and a seta; segment 8 with three modified spines and posterior corner produced into lobate extension; distal segment with seven naked setae (two of which spatulate) and apical acrothek. Setal formula: 1-[1], 2-[6 + 1 plumose], 3-[4 + 2 pinnate spines], 4-[1], 5-[2 + (1 + ae)], 6-[2], 7-[1 + 2 modified], 8-[1 + 3 modified], 9-[7 + acrothek]. Acrothek consisting of short aesthetasc (15- M m long) fused basally to two slender setae.

P5 ( Fig. 16F): with armature as in female; inner spinous process, without subapical flagella and leg slightly more slender than in female.

Sixth legs ( Fig. 16F) asymmetrical, with smallest P6 closing off functional gonopore; each with a long, plumose, outer seta and a short, naked, inner spine.

Remarks: Nicholls (1945) overlooked the inner seta on P4 exp-3, an error that perpetuated in various comparative analyses ( Noodt, 1955b; Bodiou & Colomines, 1986) and species keys ( Lang, 1965; Karanovic, 2000). Within the genus, N. spinicaudatus belongs to a lineage that is characterized by: (1) anal somite without paired dorsolateral processes; (2) anal operculum weakly developed, without rounded medial extension; (3) P1 exp-1 with outer spine, exp-3 with four setae/spines; (4) P1 enp-2 with outer spine and inner geniculate seta distally; (5) P2 exp-2 with outer spine of normal length (not extending far beyond distal margin of exp-3); (6) endopod P2–P3, twosegmented; (7) P2 enp-2 with inner seta and two distal spines; (8) P3 enp-2 with two distal spines KEY TO SPECIES OF SPINICAUDATUS LINEAGE

1. P4 exp-3: without inner seta ................................................................................................. N. pacificus . P4 exp-3: with inner seta ................................................................................................................... 2.

2. Urosome (except anal somite): with distinct surface ornamentation consisting of elongate rectangular plates ...... ......................................................................................................................................... N. clasingi . Urosome: without conspicuous surface ornamentation ............................................................................. 3.

3. Caudal ramus: with dorsolateral spur near base of seta VII.....................................................................4. Caudal ramus: without dorsolateral spur near base of seta VII.............................................. N. ishikarianus .

4. Lappets of abdominal hyaline frills semi-incised obtusidigitate; inner seta of P2–P3 enp-2 longer than endopod; P5 3.0 times as long as wide, with naked spinous process............................................................... N. spicatus . Lappets of abdominal hyaline frills denticulate; inner seta of P2–P3 enp-2 shorter than endopod; P5 about 2.5 times as long as wide, with pinnate spinous process .................................................................. N. spinicaudatus .

(outer one fused to segment); and (9) P4 enp-2 outer seta normally developed. In addition to the type species, this spinicaudatus lineage includes N. ishikarianus , N. clasingi , N. pacificus and N. spicatus , all of which assume a Pacific distribution. Neoleptastacus spinicaudatus is very similar to the Chilean N. spicatus , but differs from it in the form of the abdominal hyaline frills (lappets denticulate vs. semi-incised obtusidigitate in N. spicatus ), the relative lengths of the inner distal seta on P2–P3 enp-2, and the shape and ornamentation of the spinous process on P5 (which is still delimited at base on the posterior surface).

The linear egg sac contains between two and four large eggs; occasionally six eggs are found, in which case they overlap. Nicholls (1945) also collected the species from Leighton Beach (in the region of Perth). Chappuis’ (1958) record from Puget Sound almost certainly pertains to Mesopontia dillonbeachia (see below). Chappuis (1954b: 269) claimed to have found one female and one male in Annaba (= Bône), Algeria, which closely resembled N. spinicaudatus .

GENUS PARARENOPONTIA BODIOU & COLOMINES, 1986

Bodiou & Colomines (1986) established this genus to accommodate two unusual Arenopontia species with a two-segmented P1 exopod, A. breviarticulata Mielke (1975) (type species) and A. trisetosa Mielke (1982a) ; the third species ( Arenopontia biarticulata Wells, 1967 ) displaying this character was placed in the genus Notopontia Bodiou in the Leptopontiidae . Both Pararenopontia species have very few characters in common, casting doubt on the monophyletic status of the genus. Martínez Arbizu & Moura (1994) considered Pararenopontia an amalgam of species sharing reduced leg segmentation, and synonymized it with Arenopontia ; however, some authors have suggested that it should be maintained as a valid genus ( Huys et al., 1996a, b; Bruno et al., 1998; Wells, 2007) or subgenus ( Bodin, 1997).

Pararenopontia breviarticulata is known from a single male collected from the Isle of Sylt ( Germany) ( Mielke, 1975), and exhibits an interesting mosaic of both apomorphic (two-segmented P1 exopod; reduced P5) and plesiomorphic (armature of P2 endopod and P4 exopod) characters. There is, however, some circumstantial evidence that Mielke’s (1975) description is deficient in some aspects. The P3 appears remarkably similar to the P4, including the presence of an inner seta on exp-3 (a feature not reported for any other arenopontiid) and two very long setae on enp-2 (not recorded elsewhere in the family), raising the suspicion that the author has not observed the real P3, but may instead have duplicated observations of P4. The male P5 is unique in possessing only three elements; it is not clear whether the inner spine (or spinous process) was overlooked, or whether the P5 is genuinely underdeveloped as a result of paedomorphosis. Evidence for the latter is found in the congruence between Mielke’s illustration and the condition observed in copepodid IV of N. indicus (cf. Rao, 1967: fig. 3-22), at which stage the P1 exopod in arenopontiids is still two-segmented before adding a final segment at the next moult. Mielke (1975) described the anal operculum with two lateral ‘Zacken’ (prongs, teeth), which are conceivably the positional homologues of the paired lateral spinous processes on the anal somite in the acanthus group of Neoleptastacus . This group includes N. acanthus , N. longiremis , N. secundus , N. indicus , N. gussoae , N. chaufriassei , N. ornamentus , N. reductaspina , and N. huysi . In all these species, the P3 endopod has an inner distal seta; the outer distal spine is either short, and fused to the segment, or completely absent ( longiremis, gussoae, indicus , and reductaspina ), but never setiform, and is virtually as long as the outer distal seta [as illustrated by Mielke (1975) for P. breviarticulata ]. The extreme disparity in the length of the outer basal seta between P3 and P4, and the very long outer spines on P2–P4 exp-2 are additional characters unique to this species. The armature formula of P1 enp-2 (one geniculate seta plus one outer distal spine) indicates a relationship with the Mesopontia – Arenopontia – Neoleptastacus lineage, and the morphology of the anal somite suggests that P. breviarticulata is probably nested within the genus Neoleptastacus . Unfortunately, repeated requests to make the holotype available for re-examination failed, and its relationships necessarily remain unresolved. Pending the collection of topotype material, we propose to regard Pararenopontia as a junior subjective synonym of Neoleptastacus , and A. breviarticulata as a species incertae sedis in Neoleptastacus . Note that Bodin (1979) had already listed it under the subgenus Neoleptastacus .

Pararenopontia trisetosa is clearly closely related to N. africanus and N. angolensis , the only marked difference being the two-segmented P1 exopod in P. trisetosa . All three species differ from other members of Neoleptastacus by the lack of the outer spine on P1 exp-1, the presence of only one outer spine on the distal exopod segment of P1 (= exp- 2 in P. trisetosa ; exp- 3 in N. africanus and N. angolensis ), the onesegmented P2–P3 endopod, and the reduced setal formula on P2 endopod [110]. Based on these apomorphic character states, P. trisetosa is formally transferred to Neoleptastacus as N. trisetosus comb. nov.