Nitocra affinis Gurney, 1927

Yildiz, Nuran Oezlem & Karaytug, Suephan, 2024, Taxonomic revision of the Nitocra affinis Gurney, 1927 species complex (Harpacticoida, Ameiridae) with descriptions of four new species and re-evaluation of its subspecies, ZooKeys 1191, pp. 35-74 : 35

Nitocra affinis Gurney, 1927

Figs 1 , 2

Unverified records.

Bermuda ( Willey 1930), Italia ( Chappuis 1938), Sweden ( Lang 1935), England ( Gurney 1932), Federated States of Micronesia ( Vervoort 1964).

Type material.

Lectotype: Egypt • 1 ♀; Ismailia. Mounted on one slide. Damaged. Abdomen lost. Gurney, R leg.; NHMUK reg. no. 1928.4.2.107.

Gurney (1927) recorded N. affinis from both Ismailia and Port Tawfiq and described both sexes based on an undisclosed number of specimens. Since a holotype was not designated by Gurney (1927) all specimens collected from both localities are collectively regarded as the type series. The incomplete female specimen collected and identified by R. Gurney (incorrectly labelled as a co-type) and deposited in the NHMUK under reg. no. 1928.4.2.107 is the only surviving syntype and is here designated as the lectotype of N. affinis . The place of origin of the latter is Lake Timsah, Ismailia which becomes the type locality of N. affinis according to ICZN Art. 76.2.

Redescription

(based on the original description and examination of the lectotype). Prosome slightly tapering proximally with several sensilla as figured (Fig. 1A, B ). First urosomite (P5-bearing somite) with lateral spinule row extending to the dorsal edge of the somite. Abdomen missing.

Antennule (Fig. 1C ) eight-segmented and joined to the cephalothorax with small triangular pseudosegment (arrowed in Fig. 1C ); first segment with spinules at the ventrolateral margin and with a tube pore near the inner dorsal margin, and with row of slender spinules on ventral surface. Long, slender aesthetasc on fourth segment fused basally with adjacent large seta. Two lateral setae on seventh segment and four lateral setae on eighth segment biarticulate at base. Setal formula 1-[1, plumose], 2-[8 +1 plumose], 3-[8], 4-[3 +1 ae], 5-[2], 6-[3], 7-[4], 8-[5 + acrothek)]. Maximum length/maximum width ratio of antennular segments as 1:1.2:1.3:1.8:1.2:1.8:1.3:2.8.

Rostrum (Fig. 1D ). Small with two dorsal sensilla near the base of apical rostral projection, which is ~ half of the rostral length, with an opening (pore) distally.

Antenna (Fig. 1E ). Coxa small, unornamented. Basis and proximal endopodal segment fused forming allobasis (ancestral segmentation between basis and first endopodal segment visible near base of exopod) with a spinule row near the base of exopod. Exopod one-segmented, with two unipinnate spines and one slender naked seta; endopod lost.

Mandible (Fig. 1F ). Gnathobase with coarse teeth ventrally, dorsal unipinnate seta could not be observed due to natural position of structure. Uniramous palp two-segmented comprising basis and one-segmented endopod. Basis armed with a bipinnate spine. Endopod with one plumose lateral seta, and four naked setae (two of them basally fused).

Maxillule not observed. Note: this appendage was impossible to be reliably observed in detail because its position underneath the maxilla. But the structure and setation of the maxillule agrees with the that of N. loweae sp. nov. On the other hand, the lectotype material was too fragile and the mouth parts were too small; therefore, the only specimen was not dissected. The maxillule had better be redescribed based on newly collected materials, preferably from newly collected topotype.

Maxilla (Fig. 1G ) with two well-developed endites on the syncoxa with a robust row of spinules on outer margin; distal endite with a strong unipinnate seta and two naked setae; proximal endite small, with two naked setae. Allobasis transformed into claw, with one naked seta at base. Endopod a reduced segment with one seta. The maxilla should be redescribed based on newly collected topotypes.

Maxilliped (Fig. 1H ) subchelate. Syncoxa unornamented with one subapical plumose seta. Basis ~ 2.4 × as long as maximum width, with row of spinules along inner margin and three small spinules on outer distal corner. Endopod represented by strong claw accompanied at base by a minute naked seta.

Swimming legs (Fig. 2A-D ); P1-P4 with three-segmented exopods and endopods (Fig. 2A-D ). Intercoxal sclerite rectangular and smooth. Praecoxa wide and with a row of spinules on outer margin (P1-P4).

P1 (Fig. 2A ). Coxa rectangular, outer distal margin ornamented with fine setules; anterior surface with a row of spinules. Basis with spinule row at the base of strong pinnate inner spine; with spinule row along distal margin. Inner margin of basis with robust spinules. Exp-1,2 with outer pinnate spine. Exp-2 with an inner plumose seta. Exp-3 with two geniculate apical setae and three outer pinnate spines. Enp-1 longer than exopod, 5 × as long as maximum width and ornamented with row of fine spinules on the middle of the segment along inner margin, with three spinules on distal margin and with a bipinnate spine originating from the distal half of the segment; enp-2 with a plumose seta on inner corner and with spinules on outer margin; enp-3 with one plumose seta and two geniculate setae distally and with few spinules on outer margin.

P2-P4 (Fig. 2B-D ). Coxa rectangular, outer distal margin naked. Inner margin of basis naked (P3, P4) or ornamented with fine setules (P2). Exp-1 without inner seta; (P2-P4) and inner distal margin of exp-1,2 with small spinules (P3, P4). Exp-1,2 with robust spinules and pinnate spine (P2-P4) on outer margin; exp-2 with an inner plumose seta (P2-P4); P2 and P3 exp-3 with seven elements; two inner plumose setae, two apical setae (the outermost being spiniform and unipinnate, the innermost slender and plumose) and three pinnate outer spines. P4 exp-3 with eight elements; two slender inner plumose setae, one well-developed inner pinnate seta, two apical setae, (the outermost being spiniform and unipinnate, the innermost slender and plumose) and three pinnate outer spines. Enp-1, 2 ornamented with robust spinules on outer margin, with small spinules on inner distal margin, and with a plumose inner seta (P2-P4); P2enp-3 with four elements; one proximal inner unipinnate seta, two distal plumose setae and one distal outer spine; P3 and P4enp-3 with five elements; one proximal inner unipinnate seta, one inner subdistal seta, two distal plumose setae and one distal outer spine.

P5 damaged, exopod lost (Fig. 2E ). Distal half of inner margin of baseoendopod with setules; endopodal lobe with five setae (two broken off, but these two missing setae depicted in the original description (see Gurney 1927: fig. 154 D, E) Armature formula of the swimming legs as follows:

Figures

Figure 1. Nitocra affinis female lectotype A habitus, lateral B habitus, dorsal C antennule (arrow pointing pseudosegment) D rostrum E antennary coxa, allobasis, and exopod F mandible G maxilla H maxilliped. Scale bars: 50 μm.

Figure 2. Nitocra affinis female lectotype A P 1, anterior B P 2, anterior C P 3, anterior D P 4, anterior E P 5, anterior. Scale bars: 50 μm.