Hatschekia, Boxshall & Bernot, 2025

Hatschekia shari Uyeno & Ali, 2013 View in CoL

Syn. Hatschekia n. sp. 15 of Justine et al., 2010b

Material examined

23 ♀♀ from gills of Lethrinus nebulosus (Forsskål, 1775) ( TC17111 ) collected off Peel Island , Moreton Bay on 13 January 2016 , 21 ♀♀ QM Reg. Nos. W55142 View Materials , 2 ♀♀ NHMUK 2025.1459 About NHMUK - 1460 About NHMUK ; 6 ♀♀ from gills of Lethrinus laticaudis Alleyne & MacCleay, 1877 ( TC16992 ) collected off Green Island , Moreton Bay on 11 January 2016 , QM Reg. Nos. W55144 View Materials ; 10 ♀♀ from gills of L. laticaudis ( TC17193 ) collected off Dunwich , North Stradbroke Is, Moreton Bay on 16 January 2016 ; 9 ♀♀ from gills of L. laticaudis ( TC17026 ) collected in Moreton Bay on 12 January 2016 ; 2 ♀♀ from gills of L. laticaudis ( TC17334 ) collected off Green Island , Moreton Bay on 12 January 2016 ; 2 ♀♀ from gills of L. laticaudis ( TC17411 ) collected off Green Island , Moreton Bay on 22 January 2016 , NHMUK Reg. Nos. 2025.1430-1458 .

Comparative material from New Caledonia

2♀♀ from gills of L. nebulosus ( JNC238 ) collected at Grand Rade ( 22° 13.69’S, 66° 23.7’E), Nouméa, New Caledonia on 04 March 2003 by Jean-Lou Justine, NHMUK Reg. Nos. 2025.1461-1462 GoogleMaps .

Supplementary description of female

Total body length excluding caudal rami ranging from 1.39 to 1.78 mm, with a mean of 1.64 mm (n = 17). Body ( Figs. 17A View FIGURE 17 , 18A–C View FIGURE 18 ) comprising anterior cephalothorax and long cylindrical trunk bearing minute conical genitoabdomen posteriorly. Cephalothorax subrectangular with protruding frontal margin; just wider than long (210 x 220 μm), with weakly convex lateral margins. Dorsal cephalothoracic shield supported by complex m-shaped subsurface chitinous frame with median and paired lateral longitudinal bars, anterior transverse thickening along frontal margin and additional transverse bar located just posterior to frontal margin; chitinous frame contained within anterior half of dorsal cephalothoracic shield. Trunk about 5.3 times longer than wide (1.47 x 0.27 mm); with maximum width about in middle, with rounded posterolateral corners ( Figs. 18A, B View FIGURE 18 ). Second pedigerous somite weakly defined anteriorly on trunk by constrictions in trunk ( Fig. 18C View FIGURE 18 ). Genitoabdomen wider than long ( Fig. 17B View FIGURE 17 ) comprising fused genital and abdominal somites; bearing paired genital apertures dorsally. Caudal rami about 1.6 times longer than wide (30 x 19 μm); armed with 6 naked setae of different lengths; lateral seta located about at middle of lateral margin. Mean number of eggs per egg sac = 26 (range 24 to 31, n = 6).

Rostrum with evenly rounded posterior margin; lacking lateral processes ( Fig. 17C View FIGURE 17 ). Antennule ( Fig. 17C View FIGURE 17 ) short, indistinctly 5-segmented: segmental setation pattern 10, 5, 4, 1, 11 + ae; 2 unequal setae located on antero-dorsal surface of first segment. Antenna ( Fig. 17D View FIGURE 17 ) 3-segmented, comprising short unarmed coxa, robust tapering basis, and distal subchela: surface of basis ornamented with minute pits; subchela with swollen and thickened base plus curved distal claw. Parabasal papilla ( Fig. 17D View FIGURE 17 ) irregularly lobate with broad base, located lateral to insertion of antenna. Mandible ( Fig. 17E View FIGURE 17 ) stylet-like, bearing 2 marginal teeth subapically. Maxillule bilobed ( Fig. 17F View FIGURE 17 ): both lobes armed with 2 unequal setae. Maxilla ( Fig. 17G View FIGURE 17 ) with posteriorly-directed digitiform process on pedestal at base, coxobasis armed with single inner seta proximally; subchela comprising long segment armed with slender seta at inner extremity and distal claw with bifid tip.

Swimming legs 1 and 2 biramous; members of each leg pair joined by short slender interpodal bars ( Figs. 17H View FIGURE 17 , 18A View FIGURE 18 ). Leg 1 ( Fig. 17I View FIGURE 17 ) with fused sympod armed with outer and inner setae: exopod distinctly 2-segmented; proximal segment with outer distal spine; distal segment bearing 3 long setal elements around apex and 2 slightly shorter setae along inner margin: endopod 2-segmented; proximal segment with inner seta; distal segment armed with 3 long setae around apex plus 1 long and 1 short seta on inner margin. Leg ornamented with curved rows of minute spinules on exopodal segments: one on first segment and two on second. Leg 2 ( Fig. 17J View FIGURE 17 ) with fused sympod bearing outer seta; exopod 2-segmented; proximal segment longer than distal, armed with short outer spine; distal segment bearing 3 setae around apex: endopod 2-segmented; proximal segment with inner seta; distal segment armed with 3 setae around apex and 1 inner seta. Leg ornamented with curved rows of minute spinules on both rami: 2 each on exopodal segments 1 and 2 and endopodal segment 2, and 1 row on endopodal segment 1. Leg 3 located laterally on trunk at 30% of length ( Fig. 17A View FIGURE 17 ), represented by 2 setae arising directly from trunk surface. Leg 4 located laterally on trunk at 70% of length ( Fig. 17A View FIGURE 17 ), represented by single seta originating directly on trunk surface.

Remarks

This species was established to accommodate material collected from the gills of Lethrinus nebulosus caught off Khor Al-Ummia, Iraq, in the northwestern Arabian Gulf ( Uyeno & Ali, 2013). Close examination of the Australian material revealed numerous similarities with the excellent description of H. shari , and the host of H. shari in the Arabian Gulf is the same species as in Moreton Bay, on the coast of Queensland. The similarities include: the shape of the cephalothorax which is widest near the posterior margin, the complexity of the supporting chitinous frame, the elongate trunk, the tapering shape of the genitoabdomen and posterolaterally directed caudal rami, the possession of 6 caudal setae, the presence of only 2 teeth on the tip of the mandibular stylet, the presence of one broad and one slender seta on each lobe of the maxillule, and the setation of the endopod of leg 2. Despite these similarities and the shared host species, there are numerous small differences between the Australian material and H. shari as described by Uyeno & Ali (2013). The most obvious differences are: the setal formula of the antennule, the presence of a posteriorly-directed digitiform process on the basal pedestal of the maxilla, and the setal formula of both rami of leg 1 and the exopod of leg 2. The setal formula of the antennule of H. shari is 9, 4, 4, 1, 13 + ae, whereas in the Australian material it was 10, 5, 4, 1, 11 + ae. The Australian material has a well defined digitiform process on the basal pedestal of the maxilla, but no process is shown by Uyeno & Ali (2013) in their illustration of the maxilla on its pedestal. Leg 1 bears 6 setae on the distal exopodal segment in H. shari compared to only 5 in the Australian material, and the endopod has a 0 – 0, 6 formula compared with 0 – 1, 5 in the Australian material. The distal exopodal segment of leg 2 carries 4 setae in H. shari but only 3 in the Australian material. The setation differences in both the antennule and the legs appear minor and Kabata (1991) was of the opinion that such minor differences in leg setation patterns are unreliable as taxonomic characters in Hatschekia . The presence of this species on Lethrinus laticaudis in Moreton Bay constitutes a new host record.

The presence of the posteriorly-directed digitiform process on the pedestal at the base of the maxilla is a distinctive feature. It was not observed in H. shari by Uyeno & Ali (2013) but could have been overlooked. Interestingly, a similar posteriorly-directed digitiform process on the maxilla is present in H. pagrosomi Yamaguti, 1939 , according to the recent redescription by Izawa (2018). Neither the original description of H. pagrosomi by Yamaguti (1939) nor the redescription based on Australian material ( Roubal et al., 1983) noted the presence of this feature, so it appears to be often overlooked. The Australian material from Moreton Bay is tentatively identified as H. shari , but comparisons also need to made between H. shari and two closely related species, H. pagrosomi and H. gracilis Yamaguti, 1954 . Hatschekia shari and H. pagrosomi share numerous character states, in particular, the elongate body of the female, the reduced semi-circular genitoabdomen bearing posterolaterally-directed caudal rami and the 2-segmented rami in legs 1 and 2 with their very similar setation formula. These two species can be readily distinguished by the extent of the subsurface chitinous frame supporting the dorsal cephalothoracic shield: in H. pagrosomi the m-shaped frame extends the entire length of the shield ( Yamaguti, 1939; Izawa, 2018) whereas in H. shari the frame is more complex (including an additional transverse bar anteriorly), and the frame only extends over the anterior 50 to 60% of the length of the shield.

Hatschekia gracilis View in CoL was established by Yamaguti (1954) to accommodate female specimens obtained from the gills of an unidentified species of Lethrinus View in CoL caught off Macassar, Sulawesi ( Indonesia). This is another elongate species, with the female very similar in shape and body proportions to H. shari View in CoL and H. pagrosomi View in CoL . Yamaguti’s original description was supported by only four illustrations, the dorsal view of the female, the antenna and legs 1 and 2, but he noted the unusual form of the chitinous frame supporting the dorsal cephalothoracic shield (Yamaguti, 1954). In his landmark review of the genus Hatschekia, Jones (1985) View in CoL considered that the form of this chitinous frame was a unique feature. The chitinous frame of H. gracilis View in CoL resembles that of H. shari View in CoL in its complexity but it extends about 75% of the length of the cephalothoracic shield compared to only 50 to 60% in H. shari View in CoL . It seems possible that this difference might reflect a slightly different viewing angle, and that H. shari View in CoL might be a junior synonym of H. gracilis View in CoL but more evidence is needed before this can be proposed.

Justine et al. (2010b) analysed the metazoan parasites present on lethrinids from New Caledonia. They reported multiple undescribed new species of Hatschekia View in CoL including two species from L. nebulosus View in CoL . One of these, designated Hatschekia View in CoL n. sp. 15 by Justine et al. (2010b, Fig. 1G View FIGURE 1 ), shares the same shape of cephalothorax and exhibits a similar shape of trunk to L. shari View in CoL . Examination of the original material collected from L. nebulosus View in CoL in New Caledonia confirms that Hatschekia View in CoL n. sp. 15 of Justine et al. (2010b) is conspecific with the Australian material identified here as H. shari View in CoL . Justine et al. (2010b) also reported the presence of the same copepod on Lethrinus harak (Forsskål, 1775) View in CoL but, after re-examination of their single specimen, we cannot confirm that it is H. shari View in CoL .