Pseudoleptomesochrella halophila ( Noodt, 1952 )

Sak, Serdar, Karaytuğ, Süphan & Huys, Rony, 2008, A review of Pseudoleptomesochrella Lang, 1965 (Copepoda, Harpacticoida, Ameiridae), including a redescription of P. halophila (Noodt, 1952) from the Black Sea and a key to species, Zootaxa 1758, pp. 45-60 : 48-54

Pseudoleptomesochrella halophila ( Noodt, 1952)

( Figs 1–4 )

Syn.: Nitocrella halophila Noodt, 1952 ; Nitocrella halophila brevifurca Wells, 1961 ; Pseudoleptomesochrella brevifurca ( Wells, 1961) Lang (1965)

Material examined. 1 Ψ dissected on 8 slides, 2 ΨΨ in alcohol (NHM reg. nos 2008.363–364) and 2 ΨΨ in alcohol ( MUZM), collected from Doġanyurt, Kastamonu Province, Turkey, 0 8 July 2001; 1 Ψ deposited in alcohol ( MUZM), collected from Kurucaşile, Bartın Province, Turkey, 0 8 July 2001; 1 ɗ dissected on 7 slides ( MUZM), 2 ɗɗ in alcohol (NHM reg. nos 2008.365–366) and 1 ɗ in alcohol ( MUZM), collected from Doġanyurt, Kastamonu Province, Turkey, 14 September 2002. All specimens collected by S. Karaytuġ and S. Sak.

Redescription. FEMALE. Body slender and cylindrical ( Fig. 1 A–B), without distinct demarcation between prosome and urosome. Total body length from tip of rostrum to posterior margin of caudal rami 450 μm (mean = 427 μm; n = 6). Sensillar pattern of body as figured ( Fig. 1 A–B). Rostrum ( Fig. 1 B) small, triangular, tapering distally; with two dorsal sensillae. Pleural areas of cephalothorax not well developed so that cephalic appendages are clearly visible in lateral aspect ( Fig. 1 A). Hyaline frills of all somites plain.

Genital double-somite ( Fig. 1 A–B) about 1.5 times longer than wide; original segmentation indicated by paired, chitinous, internal ribs dorsolaterally. Anal somite ( Fig. 1 A–B) slightly longer than wide; anal operculum ( Fig. 1 E) slightly rounded, without ornamentation; anal cleft with incised frill as figured.

Caudal rami ( Figs1 E, 2A–B) about 1.5 times longer than wide, slightly tapering posteriorly; dorsal surface without crest-like bulge. Each ramus with an integumental pore dorsally, laterally and ventrally (tubepore); with seven naked setae (indicated by Roman numerals I–VII in Fig. 2 A–B; seta I not figured in Fig. 1 E); seta I smallest; seta II positioned dorsally to seta I; seta III arising from outer distal corner; seta IV and V located terminally, both with fracture planes; seta V longest; seta VI small and located ventrally, near inner distal corner; seta VII located dorsally, near inner distal corner, tri-articulated at base.

Antennule ( Fig. 2 C) long and slender; 8-segmented. Segment 1 with tiny seta near anterodistal margin. Segment 2 longest, about twice longer than wide with nine naked setae. Segment 4 with long aesthetasc (L: 133 μm) fused at base with a very long seta. Distal segment with 5 naked setae and apical acrothek. Armature formula 1-[1], 2-[9], 3-[5], 4-[2 + (1 + ae)], 5-[1], 6-[2], 7-[4], 8-[5 + acrothek]. Apical acrothek consisting of an aesthetasc (L: 32 μm) and two slender setae.

Antenna ( Fig. 3 B). Basis small and with two slender spinules along inner margin. Exopod 2-segmented; proximal segment with a bipinnate seta at inner distal corner; distal segment with a slender bipinnate seta along inner margin and a strong, bipinnate seta apically. Proximal endopod segment without ornamentation, twice longer than wide. Distal endopod segment with three spinular tufts along abexopodal margin and a hyaline frill on anterior surface; lateral armature consisting of one naked and one unipinnate spine; apical armature consisting of five geniculate setae, largest one of which with spinules around geniculation and fused at base to slender seta.

Mandible ( Fig. 2 D). Gnathobase well developed with series of weakly developed teeth and with a unipinnate seta at dorsal corner. Palp 2-segmented, consisting of basis and 1-segmented endopod. Basis elongate, with two bipinnate (one short, one long) setae and one pectinate seta laterally. Endopod with two lateral and three apical naked setae.

Maxillule ( Fig. 2 E). Praecoxal arthrite with a spinular row along medial margin and with five spines/setae around distal margin; anterior surface with two parallel setae; posterior surface with spinular row. Coxal endite with one strong pinnate, geniculate spine. Segment boundaries between basis and rami not well expressed; basal endite with three apical setae; endopod (and possibly exopod) represented by total of five naked setae.

Maxilla ( Fig. 2 F). Syncoxa with two endites (proximal one smaller) and two surface spinular rows; proximal endite with one plumose seta and one apically serrate, basally fused seta; distal endite with one bipinnate and two naked setae. Allobasis drawn out into a claw-like pinnate endite with one accessory seta. Free endopod represented by minute segment with one slender seta.

Maxilliped ( Fig. 2 G) well developed, subchelate. Syncoxa well developed, with one bipinnate seta. Basis elongate, with two spinular rows along outer distal corner and on anterior surface. Endopod represented by a strong, curved, bare claw accompanied at base by minute naked seta.

P1 ( Fig. 1 D). Intercoxal sclerite small and squarish, with concave ventral margin (as in male, see Fig. 4 E). Coxa with an oblique spinular row on anterior surface. Basis narrower than coxa, with spinules around bases of inner spine and outer seta and between bases of rami; with integumental pore on anterior surface; outer seta bipinnate and inner spine unipinnate. Exopod 3-segmented (exp-3 longest); exp-1 and -2 with spinules around bases of outer spines; outer margins of exp-2 and exp-3 with spinular row; inner margins of segments without ornamentation except for single spinule on exp-2; exp-3 with three spines and two geniculate setae. Endopod 3-segmented, longer than exopod; enp-1 3.8 times longer than wide, with three spinules located halfway along inner margin and with a serrate inner seta in distal third; enp-2 smallest, with bipinnate inner seta and spinules along outer margin; enp-3 with spinular row along outer margin and apical armature consisting of outer curved spine, one geniculate seta and one small naked inner seta.

P2–P4 ( Fig. 3 C–D) intercoxal sclerites squarish, with concave ventral margins. Praecoxae small and with a spinular row at outer proximal corner (praecoxa of P3 also with spinular row on anterior surface). Coxae rectangular; without any ornamentation except for spinular row on anterior surface of P2. Bases smaller than coxae; anterior surface with a pore near base of outer seta; spinular patterns as illustrated; outer basal element spiniform and bare in P2, setiform and plumose in P3–P4. Exopods 3-segmented; exp-1 and 2 with outer and inner spine; all exopod segments with spinules along outer margins; inner distal element of exp-3 minute (arrowed in Fig. 3 C–E). Endopods 2-segmented; segments with spinules along outer margin. Spine and seta formula as follows:

P5 ( Fig. 1 C). Baseoendopod with two pores on anterior surface; endopodal lobe rectangular, with one long naked seta and three bipinnate spines; outer basal seta plumose; exopod longer than wide; with four naked setae distally and a tube-pore along outer margin.

Genital field positioned near anterior margin of genital double-somite (position arrowed in Fig. 1 A); gonopores fused medially forming common slit, closed off by vestigial P6 ( Fig. 3 A) with one small plumose spine and one spinous process (internally). Copulatory pore large, leading via copulatory duct to single median receptacle.

MALE. Total body length from tip of rostrum to posterior margin of caudal rami 385 μm (mean=340 μm; n=4). Ornamentation of body ( Fig. 4 A) generally as in female. Sexual dimorphism in antennule, genital segmentation, P1 inner basal spine, P4 endopod, P5 and P6. Spermatophore length 46 μm.

Antennule ( Fig. 4 C–D) haplocer, indistinctly 11-segmented; with geniculation between segments 8 and 9 and aesthetasc on segments 5 and 11. Setal formula: 1-[1], 2-[9], 3-[6], 4-[2], 5-[5 + 1 spine + (1 + ae)], 6-[1], 7-[1], 8-[3 setae + 1 spine], 9-[2 spines], 10-[5], 11-[3 + acrothek). Apical acrothek consisting of aesthetasc fused basally to two setae.

P1 inner basal spine ( Fig. 4 E) transformed as figured.

P4 distal endopod segment ( Fig. 3 F) shorter than in female; inner seta displaced to inner distal corner, shorter than in female and naked instead of bipinnate.

P5 ( Fig. 4 B) biramous, fused medially. Baseoendopod with two pores on anterior surface and with outer basal seta arising from short setophore. Endopodal lobe not extending beyond middle of exopod; distal margin with two minute naked setae and long bipinnate inner seta. Exopod with three setae distally, middle one shortest, and a tube-pore along outer margin.

P6 ( Fig. 4 B) partially fused and slightly asymmetrical; with three naked seta distally, outermost being shortest.

Figures

FIGURE 1. Pseudoleptomesochrella halophila (Noodt, 1952): (A) habitus Ψ, lateral [position of genital field arrowed]; (B) habitus Ψ, dorsal; (C) P 5 Ψ; (D) P 1 Ψ, anterior; (E) anal somite and caudal rami Ψ, dorsal.

FIGURE 2. Pseudoleptomesochrella halophila (Noodt, 1952): (A) anal somite and left caudal ramus Ψ, lateral; (B) anal somite and right caudal ramus Ψ, ventral; (C) antennule Ψ, ventral; (D) mandible Ψ; (E) maxillule Ψ, posterior; (F) maxilla Ψ; (G) maxilliped Ψ, anterior.

FIGURE 3. Pseudoleptomesochrella halophila (Noodt, 1952): (A) genital field Ψ; (B) antenna Ψ; (C) P 2 Ψ, anterior; (D) P 3 Ψ, anterior; (E) P 4 Ψ, anterior; (F) P 4 endopod, distal segment ♂, anterior. [vestigial inner distal element on P 2 – P 4 exp- 3 arrowed in C – E].

FIGURE 4. Pseudoleptomesochrella halophila (Noodt, 1952): (A) habitus ♂, lateral; (B) urosome ♂, ventral; (C) antennule ♂, ventral; (D) antennulary segments 3 – 7 ♂, dorsal; (E) P 1 ♂, anterior [insert showing modified inner basal spine].