Nitocra elegans (T. Scott, 1905 )

Gee, J. Michael, 2009, Some new and rare species of Ameiridae (Copepoda: Harpacticoida) from the Isles of Scilly, UK, Journal of Natural History 43 (45 - 46), pp. 2809-2851 : 2846-2850

Nitocra elegans (T. Scott, 1905)

( Figures 20–21 )

Material examined

Ten ♀♀ (one dissected onto one slide, nine spirit preserved). Nine ƋƋ (one dissected onto one slide, one onto three slides, seven spirit preserved). NHM reg. nos 2009.213–214; 2009.215–224.

Description of female

The female of this species has been described by Scott (1905) as Ameira elegans from the east coast of Scotland and by Monard (1935) from Roscoff. It has been recorded from intertidal rock pools on the Norfolk coast (Hamond pers. comm.) and in the Scilly Isles by Wells (1970) from gravel and filamentous algae in low water rock pools at Porth Hellick on St. Mary’s. The male was unknown to these authors.

Description of male

As in female except for urosome, antennule, P1 basis, P4 exp-3, P5, P6.

Body. See Figure 20A–C . Length 0.482 –0.688 mm (mean = 0.577 mm, n = 8). Genital somites completely separate. P6s forming two equal plates on posterior margin of urosomite-2, each bearing three setae. All urosomites with prominent, dentate hyaline frills. Ornamentation moderately complex, as figured. Operculum semi-circular, ornamented with 10–12 strong spines. Caudal rami about as broad as long in ventral view, with lateral and ventral row of spinules near distal margin and seven setae normally placed

Antennule. See Figure 21B–C . Ten-segmented, haplocer, segments -5 to -8 slightly swollen, major articulation between segments -7 and -8. Segment-1 with row of spinules, segment-5 with a closely set group of small setae and a large aesthetasc, segments -6 and -7 with a modified pinnate spine, segment-10 with terminal trithek of two setae and a slender aesthetasc. Setal formula as follows: 1-(1), 2-(11), 3-(8), 4-(2), 5-(14? + 2 spines + (1+a)), 6-(1+1 modified spine), 7-(1+1 modified spine), 8-(1+3 spines), 9-(4), 10-(5+(2+a)).

Antenna. Partial basis with no abexopodal setae on basis or enp-1; enp-2 with two spines and two setae subdistally on outer margin, distal margin with five geniculate and one normal setae. Exopod one-segmented with three setae, not four as shown in Scott (1905).

Mandible. As shown in Scott (1905) except that large plumose basal seta very flimsy and poorly chitinized and endopod bears one plumose seta on lateral margin and five naked setae, three fused at base, on distal margin.

Maxillule. See Figure 20D . Praecoxal arthrite with two surface setae, two plumose setae on inner margin and six recurved spines on distal margin. Coxal endite with one pectinate spine and two setae. Basis with five naked setae on distal margin and two sub-distal, poorly chitinized, highly plumose setae (one missing in Figure 20D ). Endopod with two naked setae.

Maxilla. See Figure 20E . Syncoxa with small row of spinules and two endites. inner endite poorly chitinized, with bulbous base extending into a tridentate projection. Outer endite cylindrical with two naked setae. Allobasal endite bearing only a large, fused, pectinate spine. Endopod with two naked setae.

Maxilliped. See Figure 20F . Syncoxa with three rows of spinules and, at outer corner, a chitinous knob and one pinnate seta. Basis with row of spinules on palmar margin and small row of spinules on outer margin. Endopodal claw with one accessory seta.

P1–P4. See Figure 21A and E. P 1 basis inner spine modified into a stout terminally hooked structure with a hyaline swelling just below hook. Otherwise as for female with enp-1 equal in length to exopod. P2 and P3 as in female. P4 exp-3 proximal inner seta (arrowed in Figure 21E ) much weaker than in female (arrowed in Figure 21F ) and only minutely pinnate; distal inner seta somewhat stronger than in female.

P5. Figure 21D . Baseoendopod of each side fused medially, exopods separate. Endopodal lobe of baseoendopod only reaching one-third way up exopod and bearing four minutely pinnate spines. Exopod more elongate than in female with row of spinules and a tube pore on outer margin and spinules on inner margin; bearing six setae, three outer setae similar to female, fourth (distal) seta longest, fifth situated on distal inner margin, spine-like and spinulose, sixth, one-third way down inner margin, swollen at base and pinnate distally.

Additional observation on female

Body. Length 0.541 –0.815 mm, (mean = 0.705 mm, n = 9). Genital double somite completely fused with no indication of line of fusion. Genital field as in Figure 21G with copulatory pore a small slit posterior to genital slit which joins the paired gonopores covered by vestigial P6s bearing one pinnate and two naked setae. Ornamentation of urosome as in male.

Antennule. Eight-segmented, segments as shown by Scott (1905). Setal formula as follows: 1-(1), 2-(8), 3-(9), 4-(3+(1+a)), 5-(2), 6-(3), 7-(4), 8-(5+(2+a)).

Mouthparts. As described for male.

P1–P5. As described by Scott (1905) except that P4 exp-3 has three inner setae, the proximal two setae are very robust but the distal seta is very slender and relatively short as shown in Figure 21F .

Figures

Figure 1. Ameiropsis martinis sp. nov., female, urosomites 2–6. (A) Dorsal; (B) lateral; (C) ventral; (D) genital field; (E) rostrum and proximal segment of antennule; (F) segmentation of antennule; (G) P5.

Figure 20. Nitocra elegans, male urosome. (A) Dorsal; (B) lateral; (C) ventral; (D) maxillule; (E) maxilla; (F) maxilliped.

Figure 21. Nitocra elegans. (A–E) Male: (A) P1 basis; (B) antennular segmentation; (C) antennular setation; (D) P5; (E) P4 exp-3; (F–G) female: (F) P4 exp-3; (G) genital field.