Halicoides Walker 1896
Creators: name: Do Nascimento, Priscila S.
name: Serejo, Cristiana S.
Publisher: name: Zenodo
Year: 2024
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Malacostraca
Amphipoda
Pardaliscidae
Halicoides

description: Genus Halicoides Walker, 1896
Halicoides Walker, 1896: 344.— Stebbing, 1906: 221.— Karaman, 1974: 19.— Thurston, 1976: 148.— Barnard & Karaman, 1991: 577.
Pardisynopia J.L. Bamard, 1961: 78 (Pardisynopia tambiella J.L. Barnard, 1961, original designation).
Type species. Halicoides anomalus Walker, 1896
Diagnosis. Rostrum well developed, reaching half-length of article 1 of peduncle of antenna 1. Eyes absent. Antennae 1–2 with long flagellum. Antenna 1, peduncle short, article 1 a little longer than articles 2 and 3; accessory flagellum present. In males, article 1 of primary flagellum with callynophore; article 1 of primary and accessory flagellum fused. Mouthparts forming quadrate bundle. Mandibles, incisors weakly toothed on both sides, palp fully developed, article 3 size variable, but shorter the article 2. Lower lip, inner lobes coalesced. Maxilla l, palp not expanded apically. Maxilla 2 well developed, slender plates, about 3x longer than wide, inner margin of inner plate setose. Coxae 1–7 short, wider than long. Gnathopods 1–2 simple, slender, carpus not lobate, dactylus claw-shaped, without inner teeth. Pereopods 3–4, merus and carpus moderately to strongly robust. Pereopods 5–7 elongated, propodus at least 10x longer than wide. Urosomites 1–2 with teeth vestigial or absent; urosomite 2 with long seta on posterodorsal angle. Uropods 1–2 well developed, setose, ramus apically rounded with robust seta; uropod 3 lanceolate, setose. Telson at least 2x longer than wide, deeply cleft (more than 70%).
Included 14 species. H. anacantha (K.H. Barnard, 1925); H. anomalus Walker, 1896; H. borealis Johansen & Vader, 2018; H. campensis sp. nov.; H. discoveryi Thurston, 1976; H. iemanja sp. nov.; H. indica Birstein & M. Vinogradov, 1964; H. latilobata Ren, 2012; H. lolo (J.L. Barnard, 1971); H. nana Birstein & M. Vinogradov, 1960; H. synopiae (J.L. Barnard, 1962); H. tambiella (J.L. Barnard, 1961); H. tertia (Stephensen, 1931); H. walkeri (Ledoyer, 1973).
Remarks: The scale-like structure in the second article of the peduncle of antenna 1, and the absence of accessory flagellum in the H. anomalus type material, caused confusions and conflict in the status of Halicoides. The structure was understood by Walker (1896) as a scale-like accessory flagellum dislocated to the second article of the peduncle, rather than on the third, which would be a unique character among all Amphipoda. The question remained until Halicoides borealis was described by Johansen & Vader (2018). In this species, an oval structure at the end of article 2 was found in male antenna 1, in addition to a well-developed accessory flagellum. Johansen & Vader (2018) had access to the unpublished holotype-drawings of H. anomalus, re-examined by Thurston (1976), and considered that the structures of H. anomalus and H. borealis are the same, which may have a sensory function to male sexual behavior.
Taking these into account, we assume that H. anomalus possess accessory flagellum together with the sensory oval structure, but this flagellum was missing accidentaly in the type material, as suggested by Thurston (1976). Thus, since every other Halicoides species has a well-developed accessory flagellum in antenna 1, we consider it as a diagnostic character of Halicoides. Further on, Halicoides can be defined by a combination of characters, initially defined by Thurston (1976), that will be compared with the closer genus Halice (in parentheses): 1) absence or vestigial teeth on urosomites 1 and 2 (versus long teeth); pereopods 3 and 4 moderately to strongly robust (versus thin and not expanded); presence of a single seta on the posterior margin of urosomite 2 (versus absent).
The presence of a seta on urosomite 2 has not been originally described for some species, but a re-examination of type material of H. anacantha, H. anomalus, H. synopiae and H. tambiella by Thurston (1976) has shown that a seta is present on urosomite 2. Thurston (1976) suggested that this seta may be presented in all species of Halicoides and thus constitutes a character of generic value. The presence of this characteristic seta was also noticed by the first author in H. lolo and H. synopiae when re-examining material of both species at the Smithsonian Institution (2019). On the other hand, H. indica, H. latilobata and H. nana have no mention of the presence of the seta in their descriptions, and it was not possible to verify material of these species. Nevertheless, we agree with Thurston (1976) that it is probable that all Halicoides species have the seta, being an important diagnostic character to be examined.
Distribution and habitat. Marine, cosmopolitan. H. latilobata from East China Sea (Ren 2012). H. indica, H. tambiella, H. synopiae, H. nana and H. lolo from Indian Ocean, Tasmanian Sea, Southern California, Eastern Pacific, respectively (Birstein & Vinogradov, 1964; J.L. Barnard 1961; J.L. Barnard 1962; Birstein & Vinogradov, 1960; Barnard, 1971). H. anacantha from South Africa (K.H. Barnard 1925) and H. walkeri from Mediterranean Sea (Ledoyer, 1973). North Atlantic Ocean, H. discoveryi from the Canary Islands (Thurston, 1976), H. anomala from Bay of Biscay, Isle de Yeu (Walker, 1896), H. tertia from West of Greenland (Stephensen, 1931). H. borealis from Northern North Sea (Johansen & Vader, 2018), H. campensis sp. nov and H. iemanja sp. nov from Southwestern Atlantic (present study, Figure 1).
The genus seems to be more dominant in shallow waters (Barnard & Karaman, 1991), but showed a wide bathymetric range 29–3084 m, based on data of the present study. The present work brings the first record of Halicoides for the Southwest Atlantic Ocean in addition to expand the bathymetry of the genus, which was previously known from 31 to 1720 m.
description: Published as part of Do Nascimento, Priscila S. & Serejo, Cristiana S., 2024, New findings of the family Pardaliscidae from the southwestern Atlantic: the genus Halicoides Walker, 1896, pp. 501-519 in Zootaxa 5481 (5) on pages 505-506, DOI: 10.11646/zootaxa.5481.5.1, http://zenodo.org/record/12782969