Caligus dussumieri Rangnekar, 1957

Ismail, Norshida, Nishida, Yusuke, Ohtsuka, Susumu, Boxshall, Geoff & Bernot, James P., 2024, First record of Caligus dussumieri Rangnekar, 1957 (Copepoda, Siphonostomatoida, Caligidae) from Malaysia, with notes on caligids found from Malaysia and on host-specificity of caligids on lutjanid fishes, Biodiversity Data Journal 12, pp. 116598-116598 : 116598

Caligus dussumieri Rangnekar, 1957

Caligus dussumieri Sinocaligus dussumieri (Rangnekar, 1957)

Caligus dussumieri Pseudopetalus dussumieri (Rangnekar, 1957)

Caligus dussumieri Caligus rivulatus (Pilla, Vankara and Chikkam, 2012)

Materials

Type status: Other material. Occurrence: occurrenceID: A71C4FDE-7825-5C4B-9023-C44E1AC10847; Taxon: taxonID: 349612 (urn:lsid:marinespecies.org:taxname:349612); scientificName: Caligus dussumieri Rangnekar, 1957; parentNameUsage: Caligus Müller O.F., 1785; originalNameUsage: Caligus dussumieri Rangnekar, 1957; kingdom: Animalia; phylum: Arthropoda; class: Copepoda; order: Siphonostomatoida; family: Caligidae; genus: Caligus; specificEpithet: dussumieri; scientificNameAuthorship: Rangnekar, 1957; taxonomicStatus: Accepted; Location: higherGeography: South East Asia; continent: Asia; waterBody: South China Sea; country: Malaysia; stateProvince: Terengganu; county: Kuala Terengganu; verbatimLocality: LKIM Pulau Kambing; verbatimCoordinates: 5°19'N 103°7' 43.7"E; verbatimLatitude: 5.321971; verbatimLongitude: 103.1288; Identification: identificationID: urn:lsid:marinespecies.org:taxname:349612; Event: samplingProtocol: Gill wash; year: 2019; month: 10; day: 19 Type status: Other material. Occurrence: occurrenceID: ADE72616-49DB-57BB-89BA-3948143646FA; Taxon: taxonID: 349612 (urn:lsid:marinespecies.org:taxname:349612); scientificName: Caligus dussumieri Rangnekar, 1957; parentNameUsage: Caligus Müller O.F., 1785; originalNameUsage: Caligus dussumieri Rangnekar, 1957; kingdom: Animalia; phylum: Arthropoda; class: Copepoda; order: Siphonostomatoida; family: Caligidae; genus: Caligus; specificEpithet: dussumieri; scientificNameAuthorship: Rangnekar, 1957; taxonomicStatus: Accepted; Location: higherGeography: Australia; continent: Australia; country: Australia; county: Camden Sound; locality: Western Australia ; verbatimCoordinates: 16° 11.52'S 124° 32.52'E; Identification: identificationID: urn:lsid:marinespecies.org:taxname:349612; Event: year: 2013; month: 9; day: 11; Record Level: institutionCode: NHMUK; collectionCode: Reg. Nos. 2022.189-197

Description

Fig. 1

Female. Body (Fig. 1 A) 3.24 mm long, excluding setae on caudal ramus. Dorsal cephalothoracic shield subcircular, slightly longer than wide. 1.31 x 1.12 mm, excluding hyaline membrane along lateral margins. Shield tapering anteriorly; with large, conspicuous lunules. Fourth pediger wider than long, incompletely fused to genital complex. Genital complex about 1.96 times longer than wide with neck-like narrow part anteriorly and barrel-shaped posterior region. Leg 5 (Fig. 1 A) represented by 1 plumose, outer protopodal seta and 2 plumose setae on exopodal papilla located on posterolateral margin of genital complex. Abdomen 1-segmented, about 2.8 times longer than wide. Caudal ramus (Fig. 2 C) oval, 0.10 x 0.07 mm, expanded inwards distally; armed with 3 short and 3 long plumose setae and ornamented with row of setules along distomedial margin.

Australian female observed using CLSM (Fig. 3 A, B) showing differential degree of staining over body surface. Dorsal cephalothoracic shield staining moderately and evenly, with heavier uptake of stain marking sutures anteriorly near origin of antennules, in area near eyes and along lateral edges of central thoracic zone of shield. Ventral curved rib marking boundary of cephalosome and incorporated first pediger strongly stained. Fourth pediger and fourth leg staining evenly. Genital complex and abdomen displaying marked differences in intensity of staining. Staining intense in small ovoid patch on dorsal surface of genital complex towards the posterior end, ventrally around the genital apertures and in the posterior part of the abdomen. Conversely, staining very light in other areas of genital complex and anterior part of abdomen.

Antennule (Fig. 1 B) 2-segmented; proximal segment carrying 27 plumose setae on anterodistal surface, 25 setose plus 2 naked (on dorsal side) setae; distal segment short with 1 subterminal seta on posterior margin and 11 setae plus 2 aesthetascs around apex. Antenna (Fig. 1 C) 3-segmented; proximal segment smallest, with short blunt process on posteromedial corner; middle segment subrectangular, unarmed; distal segment forming long, curved claw armed with stout proximal seta and simple middle seta. Postantennal process (Fig. 1 C) shorter than distal segment, tine curved inwards with blunt tip, ornamented with 2 multisensillate papillae on basal region and another multisensillate papillae present on sternum adjacent to base of process. Additional lobate process present between postantennal process and base of antenna. Mandible (Fig. 1 D) stylet-like, with 4 sections, bearing 12 teeth on medial margin of distal blade. Maxillule (Fig. 1 C) comprising large stout dentiform process and basal papilla with 3 setae (1 short, 1 medium and 1 long). Maxilla (Fig. 1 E) 2-segmented; lacertus large and unarmed; slender distal segment (brachium) bearing rounded membranous subapical flabellum on anterior margin and terminating in 2 subequal claw-like elements (calamus and canna). Calamus longer than canna, ornamented with strips of serrated membrane arranged obliquely around surface; canna ornamented with strips of serrated membrane bilaterally. Maxilliped (Fig. 1 F) 3-segmented; proximal segment (corpus) largest, unarmed, 2 unequal processes along myxal area, longer than next 2 segments combined (subchela); middle segment unarmed; distal claw longer than shaft, sharply pointed with long seta at base of claw. Sternal furca (Fig. 1 G) subrectangular, box with tiny rounded outgrowth anteriorly, tines blunt and weakly divergent.

Leg 1 (Fig. 4 A, Fig. 2 A) with 2 segmented protopod bearing 1 inner and 1 outer small plumose seta plus bifid setule on outer margin. Intercoxal sclerite slender, with 2 papillae each bearing a setule present on sternum posterior to sclerite. Vestigial endopod reduced to tiny, pointed process located near base of exopod. Exopod 2-segmented, first segment with row of fine setules along inner margin and spiniform seta at outer distal corner; second segment with 3 large plumose setae ornamented along outer margin with stout spinules at base becoming finer towards tip and with short plumosities along inner margin; 4 terminal elements, spine 1 simple, spines 2 and 3 each with accessory process (Fig. 4 a), seta 4 longest, stout and pinnate on only one side. Leg 2 (Fig. 4 B, Fig. 2 B) with intercoxal sclerite ornamented with marginal membrane along posterior margin; coxa with large plumose seta at posterior corner and minute setule on anterior surface; basis ornamented with marginal membrane on both inner and medial margins, bearing minute seta at outer distal corner plus setule near mid-point of inner margin. Endopod 3-segmented: first segment armed with inner plumose seta and ornamented with large denticles at outer distal corner; second segment with 2 inner distal setae plus row of robust denticles along outer margin; third segment with 6 plumose setae. Exopod 3-segmented: first segment with reflexed membrane dorsally and with pecten at base of long, stout, outer spine with spatulate tip extending obliquely across surface of second and third segments; second segment with relatively short outer spine, third segment armed with 1 small and 1 medium outer spine (latter ornamented with extensive marginal membrane), longer distal spine ornamented with membrane on outer side and plumosities on inner side, plus 5 plumose setae. Leg 3 (Fig. 5 A) apron (protopod) bearing small, plumose outer seta and long, plumose inner seta and ornamented with membrane along outer and posterior margins, 4 patches of spinules plus 2 setule-bearing papillae on either side of innermost patch, plus 2 relatively long setules near posterior margin. Endopod 2-segmented, proximal segment small, armed with 1 long plumose seta; segment expanded to form velum fringed with setules along free margin; second segment armed with 6 plumose setae. Exopod 3-segmented, proximal segment small, with pecten-like membrane on inner margin of segment and with an expanded outer distal corner ornamented with strip of membrane located lateral to outer spine plus minute setule on outer margin, outer distal spine slightly curved, not reaching distal border of second segment (Fig. 5 a); second segment with inner plumose seta and outer naked spine; third segment with 3 setiform spines increasing in size distally plus 4 inner setae. Leg 4 (Fig. 5 B) plumose seta at outer distal corner of protopodal segment; exopod distinctly 2-segmented, first exopodal segment with long outer spine; second segment with 4 spines along oblique outer distal margin; each spine with pecten at base (Fig. 5 b).

Taxon discussion

The initial description of C. dussumieri was provided by Rangnekar (1957). It was later transferred by Pillai (1968) to his new genus Pseudopetalus Pillai, 1968, as Pseudopetalus dussumieri , but was subsequently transferred to Sinocaligus Shen 1957 as Sinocaligus dussumieri after Pseudopetalus was recognised as a junior synonym of Sinocaligus ( Boxshall and Montu 1997, Dojiri and Ho 2013). In a recent comprehensive revision by Boxshall and Barton (2023), the complex taxonomic history of C. dussumieri was thoroughly examined. They proposed to recognise Sinocaligus as a junior subjective synonym of Caligus and returned S. dussumieri to its original combination as C. dussumieri . Boxshall and Barton (2023) also recognised Caligus rivulatus Pilla, Vankara and Chikkam, 2012, described from Lutjanus rivulatus Cuvier, 1828 in Indian waters, as a junior subjective synonym of C. dussumieri . The Malaysian specimen was identified as a mature pre-metamorphic female due to the presence of elongated and slender genital complex and abdomen, which corresponds closely with the developmental stage described in the previous studies by Pilla et al. (2012) and Boxshall and Barton (2023). This particular specimen measured 3.24 mm in total length, a measurement consistent with the total length range of C. dussumieri , referred to as C. rivulatus by Pilla et al. (2012), ranging from 2.36 to 3.12 mm. Similarly, it exhibited a comparable total length to the Australian specimens, which measured between 3.05 and 3.65 mm.

In comparison to the recent re-description of C. dussumieri from Australian waters as provided by Boxshall and Barton (2023), the C. dussumieri specimens from Malaysia displayed subtle differences including the presence of a neck-like constriction in the anterior part of the genital complex and the more barrel-shaped genital complex, features also observed in C. dussumieri from Indian waters ( Rangnekar 1957, Pillai 1967, Pilla et al. 2012). As discussed below, we consider these differences can be explained by the pre-metamorphic stage of development of these sets of specimens.

Another minor difference was noted regarding the postantennal process. In the current study, C. dussumieri possessed trisensillate papillae, consistent with the description of Pillai (1985), while the Australian specimens exhibited bisensillate papillae. In addition, a rounded, lobate process was present between the postantennal process and the base of the antenna in the Malaysian female. The female from Malaysia lacked the patch of small setules at the base of the inner protopodal seta of leg 1, present in the other specimens. Furthermore, the tips of spines 2 and 3 on the distal exopodal segment of leg 1 were ornamented with a row of serrations, distinguishing them from previously described specimens from India and Australia.

A pecten-like structure at the outer distal corner of the first exopodal segment of leg 3 was observed in the present specimen, but this feature was not illustrated in previous studies. However, this structure's presence in the Australian material was subsequently confirmed through additional observations of Australian specimens in this study.

Figures

Figure 1. Caligus dussumieri Rangnekar, 1957, adult female. A Habitus, dorsal view; B Antennule; C Antenna; D Mandible; E Maxilla; F Maxilliped; G Sternal furca.

Figure 2. CLSM images of Caligus dussumieri Rangnekar, 1957. A Exopod of leg 1, showing spinular ornamentation on plumose setae along posterior margin; B Rami of leg 2 showing ornamentation on outer margin of endopod and spatulate spine on first exopodal segment.

Figure 3. CLSM images of Caligus dussumieri Rangnekar, 1957. A dorsal view; B ventral view.

Figure 4. Caligus dussumieri Rangnekar, 1957 adult female. A Leg 1, a Four terminal elements of Leg 1; B Leg 2.

Figure 5. Caligus dussumieri Rangnekar, 1957, adult female. A Leg 3, a Proximal segment of leg 3 exopod; B Leg 4, b Distal elements of Leg 4 second segment.