Hatschekia cernae Goggio, 1905

Hatschekia cernae Goggio, 1905 View in CoL

Material examined: 2 ♀♀ from gills of Epinephelus coioides (Hamilton, 1822) ( TC17614 ) collected at Chain Banks , Moreton Bay on 26 June 2016 ; 1 ♀ QM Reg. No. W55132 View Materials , and 1 ♀ dissected, NMHUK Reg. No. 2022.213 .

Supplementary description of female

Total body length excluding caudal rami 1.10 and 1.26 mm (n = 2). Body ( Fig. 5A View FIGURE 5 ) dorsoventrally flattened, comprising anterior cephalothorax merging imperceptibly with posterior trunk; cephalothorax/trunk boundary not defined; entire body encased in transparent cuticle separated from underlying tissues by distinct gap. Cephalothorax longer than wide, apparently lacking defined dorsal shield, but retaining subsurface chitinous frame ( Fig. 5A View FIGURE 5 ) comprising long median longitudinal bar running almost entire length of cephalothorax, with 4 transverse cross bars; anteriormost running along frontal margin of cephalothorax and then turning towards posterior and joining second cross bar, third cross bar located about in middle of cephalothorax (each divided at tip), and fourth bar located posteriorly. Trunk as wide as cephalothorax anteriorly, gradually becoming wider posteriorly with maximum width just anterior to level of fourth legs; posterior margin of trunk rounded with raised collar-like ridge around genitoabdomen, appearing like small processes either side ( Fig. 5B View FIGURE 5 ). Genitoabdomen extremely short; about 3.3 times wider than long; bearing paired genital apertures dorsally. Caudal rami posterolaterally-directed, about 2.4 times longer than wide (57 x 24 μm); each ramus with distinct swollen proximal part ( Fig. 5B View FIGURE 5 ); armed with 6 slender naked setae of different lengths; lateral seta located about at 54% of lateral margin. Egg sac containing 15 eggs (n = 1).

Rostrum lacking lateral processes. Antennule ( Fig. 5C View FIGURE 5 ) indistinctly 5-segmented: segmental setation pattern 7, 5, 4, 1, 13 + ae; apparently lacking setae on antero-dorsal surface of first segment. Antenna ( Fig. 5D View FIGURE 5 ) 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. Mandible stylet-like ( Fig. 5E View FIGURE 5 ), bearing row of 6 minute marginal teeth subapically. Maxillule bilobed ( Fig. 5F View FIGURE 5 ): both lobes armed with 2 setae; setae on outer lobe more robust and longer than on inner lobe. Maxilla ( Fig. 5G View FIGURE 5 ) 2-segmented, armed with single inner seta proximally on basal segment; 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 first leg pair joined by slender interpodal bar ( Fig. 5H View FIGURE 5 ); second legs displaced laterally, interpodal bar modified to form box-like framework of sclerotized cuticle. Leg 1 ( Fig. 5H View FIGURE 5 ) 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 1 shorter seta distally on inner margin: endopod indistinctly segmented; bearing 2 subequal apical setae. Leg ornamented with curved rows of minute spinules: 3 on sympod, 2 each on exopodal segments, and 1 on endopod. Leg 2 ( Fig. 5H View FIGURE 5 ) with fused sympod bearing outer seta; exopod 2-segmented; proximal segment armed with outer spine; distal segment bearing 3 long setae around apex and 1 well developed seta near middle of inner margin: endopod indistinctly 2-segmented; proximal segment armed with well-developed inner seta; distal segment armed with 1 long and 2 shorter setae on apical margin. Leg ornamented with curved rows of minute spinules: 1 on sympod, 2 each on exopodal segments, 1 on endopodal segment 1, and 4 on endopodal segment 2. Leg 3 located laterally on trunk at 23% of length, represented by distinct lobe armed with 2 hirsute setae ( Fig. 5A View FIGURE 5 ; inset). Leg 4 located laterally on trunk at 74% of length, represented by single unilaterally pinnate seta originating on slender lobe ( Fig. 5A View FIGURE 5 , inset).

Remarks

Hatschekia cernae View in CoL is a very distinctive species, recognizable not only by its unusually modified body form in which the cephalothorax and trunk merge without any marked change in width, but also by the lateral displacement of leg 2 relative to leg 1 and the associated modification of the interpodal bar of leg 2. Up until the present, this distinctive species has only had a single synonym: Capart (1959) described a new species, H. epinepheli Capart, 1959 View in CoL , based on females collected from the gills of Epinephelus marginatus (Lowe, 1834) View in CoL (as E. gigas View in CoL ) caught in the South Atlantic off Angola. Capart distinguished his new species from H. cernae View in CoL primarily on the basis of its longer and more slender trunk, but Jones (1985) considered that “the length to width ratio was not a valid criterion for distinguishing species of Hatschekia View in CoL ”, and relegated H. epinepheli View in CoL to synonymy with H. cernae View in CoL . This synonymy is accepted here.A second species, H. flatti Uma Devi & Shyamasundari, 1980 View in CoL , is recognized here as a junior subjective synonym of H. cernae View in CoL . The body shape of H. flatti View in CoL is identical to that of H. cernae View in CoL and Uma Devi & Shyamasundari (1980) even noted the peculiar lobes visible in the denser tissue underlying the cuticle that are readily visible in the Australian material (see Fig. 5H View FIGURE 5 ). There are no significant differences in the appendages that cannot be attributed to the descriptive standards of the day, and the caudal rami exhibit the same unusual proximal swelling as noted in the Australian material.

This species was originally described from the Mediterranean by Goggio (1905) based on material collected from the gills of E. marginatus View in CoL (as Cerna gigas View in CoL ) caught off Palermo, Italy in 1893. Goggio (1905) also mentioned finding a vial of specimens from the gills of Epinephelus aeneus (Geoffroy Saint-Hilaire, 1817) View in CoL (as Cerna aenea ). No locality data were given for these additional specimens by Goggio (1905), but in his monograph Brian (1906) appears to indicate that this material may also have come from the Mediterranean. Rose & Vaissière (1952) produced a catalogue of copepod species recorded from the North African coast which listed H. cernae View in CoL as “assez commun” on the gills of E. marginatus View in CoL (as E. gigas View in CoL ) and E. aeneus View in CoL . In their meta-analysis of parasitic copepods recorded from Mediterranean fishes, Raibaut et al. (1998) listed E. marginatus View in CoL (as Epinephelus guaza ) as the host of H. cernae View in CoL .

The first record of this species from outside the Mediterranean was from Nuñes-Ruivo (1954) who reported a large sample of H. cernae collected from the gills of the type host E. marginatus (as E. gigas ) and a new host, Epinephelus fasciatus (Forsskål, 1775) (as E. alexandrinus ), caught off Gorée Island on the Atlantic coast of Senegal. Capart’s (1959) record from Angola (as H. epinepheli ) was also from E. marginatus (as E. gigas ). Dippenaar’s (2005) inclusion of H. epinepheli in her collated synopsis of siphonostomatoid species from southern African marine fishes is based on Capart’s record.

Shiino (1957) dramatically expanded the known geographical range of H. cernae with his new record from an unidentified Epinephelus species caught at Naha, Okinawa, Japan. The first record from Indian waters is that of Uma Devi & Shyamasundari (1980) as H. flatti . The host reported by Uma Devi & Shyamasundari (1980) was Johnius sp. and this is the only non-serranid ever mentioned as host of H. cernae . We consider that this host record is probably erroneous and should be treated with caution as there is now no way to confirm the host identification. More recently, Ho & Sey (1996) reported H. cernae from Epinephelus tauvina (Forsskål, 1775) caught off Kuwait in the Arabian Gulf, and Justine et al. (2010a) reported it from Epinephelus morrhua (Valenciennes, 1833) caught in waters off New Caledonia. The discovery of H. cernae on E. coioides in Moreton Bay is the first record of this widespread and distinctive parasite from Australian waters and it also constitutes a new host record.

Two closely related species of Hatschekia were described from Epinephelus species collected in New Caledonia ( Lee et al., 2013): H. cyanopodus Lee, Lee & Boxshall, 2013 from Epinephelus cyanopodus (Richardson, 1846) and H. maculatus Lee, Lee & Boxshall, 2013 from Epinephelus maculatus (Bloch, 1790) . These two species share with H. cernae a similarly flattened body in which the cephalothorax and trunk merge without any marked change in width. However, these species can be distinguished by the endopodal setation of legs 1 and 2: in both H. cyanopodus and H. maculatus the endopod of leg 1 is tipped with a single apical seta whereas it bears 2 apical setae in H. cernae , and in both H. cyanopodus and H. maculatus the endopod of leg 2 bears 2 apical setae compared to 1 medial and 3 apical setae in H. cernae . There are other differences including the well defined posterior margin to the dorsal cephalothoracic shield in H. cyanopodus and H. maculatus compared with the lack of a defined margin in H. cernae .