Lernaeenicus stromatei Gnanamuthu, 1953

Aneesh, Panakkool Thamban, Helna, Ameri Kottarathil, Kumar, Appukuttan Biju & Maran, Balu Alagar Venmathi, 2018, Redescription of Lernaeenicus stromatei Gnanamuthu, 1953 (Copepoda: Siphonostomatoida: Pennellidae) infesting the Black Pomfret Parastromateus niger (Bloch) from Indian waters, Zootaxa 4482 (2), pp. 375-382 : 377-378

Lernaeenicus stromatei Gnanamuthu, 1953

( Figs 1–4 )

Lernaeenicus stromatei Gnanamuthu, 1953 , p. 3, figs. 17–22; Pillai, 1985, p, 722; Aneesh, 2014, p.168, fig. 2.14g, Raja, Saravanakumar, Gopalakrishnan, Vijayakumar, Hwang & Venmathi Maran, 2016, p. 192–211, fig. 7.

Material examined. 23 ♀♀

Type material. Neotype —here designated, ♀ (70 mm), Marina Beach fish landing centre, Chennai, India (13.0500° N, 80.2824° E, Bay of Bengal) Reg. No. C-7146/2 from Parastromateus niger (Bloch) , coll. P.T. Aneesh.

Non type material. All from Parastromateus niger (Bloch) coll. Aneesh and Helna, 1♀ (66 mm), Bekal fish landing centre (12° 25' 14 N'', 75° 1' 23 E″, Malabar Coast) Reg. No C-7162/2 ; 1♀ (69 mm), Ayyikkara fish landing centre (11 0 51′33″ N, 75 0 22′ 30 E″, Malabar Coast, India) Reg. No C - 7163/2 ; 1♀ (47 mm), Marina Beach fish landing centre (13.0500° N, 80.2824° E, Bay of Bengal ) Reg. No C-7164/2.

Description. Female. Body (41–79 mm), long and slender; Cephalon attached at right angles to neck, anteriorly rounded and somewhat dorso-ventrally flattened and 1.5–1.6 mm longer than wide, with three posterior horns, one median directed backwards and two lateral directed outwards and backwards, all sub-similar and apically rounded. Elongated, tubular neck, gradually enlarging into the trunk, about 3.6–5.4 mm. Anterior neck with indistinct partition on dorsal side, indicating thoracic segments. Abdomen very narrow, 0.27–0.36 mm as the length of neck. Genital part of trunk (8–11 mm) forming a step-like projection from which the egg strings are attached.

Egg string longer than abdomen; eggs uniserriate. Caudal rami absent. Number of eggs per string ranged from 110 to 160, dependent on length of the string.

Antennule slender, 3- segmented; all segments with many setae. Article 2 with a cluster of long setae. Antenna stouter than antennule, 3- articled, terminal segment chelate, with sharp and strongly curved claw. Oral appendages situated in the proboscis. Proboscis a retractile, chitinous tube, situated at the ventral side of the cephalon, armed with an outer saclike plate and an inner ring like cephalosome bearing a single row of recurved spines. In the upper part of the proboscis a fork like buccal style is present. Mandibles within the oral tube. Maxillules, small and situated on side of the proboscis, inner lobes with few long setae, outer lobe with one short seta. Maxillae 3- articled, third article narrow, as long as second, ventral border of article 2 and 3 denticulated.

Swimming Legs, 4 pairs, located just behind the head, successively decreasing in size from L1–L4. L1 and L2 biramous, 3–4 uniramous. Rami of all legs 2- articled, setose. L1 almost on the head, L2–L4 on the neck.

Size. Ovigerous female: 41–79 mm (total length excluding egg strings)

Colour. Live specimens are translucent with light red colour anteriorly.

Host. Reported only from Parastromateus niger (Bloch) ( Gnanamuthu 1953; Pillai 1985; Aneesh 2014; Raja et al. 2016)

Distribution. Chennai (type locality) ( Gnanamuthu, 1953; present study), Malabar Coast ( Aneesh 2014; present study), West Bengal (present study), South east coast ( Raja et al. 2016).

Remarks. Lernaeenicus stromatei is one of ten species of Lernaeenicus known from India ( Pillai 1985; Raja et al. 2016) and is very distinct within the genus. Lernaeenicus stromatei can be identified by the following characteristic features: (1) long and slender body; (2) head anteriorly rounded, dorso-ventrally flattened and slightly longer than broad; (3) presence of three posterior horns on the head, one median and two lateral, all subsimilar and apically rounded; and (4) anterior part of neck with indistinct partition on dorsal side, indicating thoracic segments, and a three-jointed antennule. Lernaeenicus stromatei closely resembles L. hemirhamphi Kirtisinghe, 1932 , but the head is asymmetrical in L. stromatei ( Pillai 1985) . Lernaeenicus stromatei has so far been reported only from black pomfret of the family Carangidae , however, L. hemirhamphi is apparently restricted to hosts in the family Hemirhamphidae ( Pillai 1985; Aneesh 2014; Raja et al. 2016). Till date most of the studies including the present work is based only on morphological data and the molecular analysis (ex: DNA profiling) may show different species distinctness amongst Lernaeenicus . Recently Hogans (2018) documented the functional morphology and structural variations among the three species of Lernaeenicus infesting the fishes from Atlantic Coast of North America. Akin to that of recent study by Hogans (2018), the functional morphology of the anchoring appendages of L. stromatei was influenced by site of attachment and feeding. Except few recent studies (for instance Hogans 2018), most of the species of Lernaeenicus need to be clarified with its detailed redescription, since many of them are not adequately documented.

Figures

FIGURE 1. Lernaeenicus stromatei Gnanamuthu, 1953 ovigerous female ex Parastromateus niger (Bloch): A–B. sites of infestation (arrow); C. habitus dorsal.

FIGURE 2. Lernaeenicus stromatei Gnanamuthu, 1953 ovigerous female ex Parastromateus niger (Bloch): A. ventral view of head and neck; B–C. lateral view of head and neck; D. neck region showing legs 1–4; E. trunk with egg sacs and hind end; F. head with antenna; G–H. head dorsal view. P—proboscis, L 1 –L 4 —legs 1–4, F—furrows in the dorsal thorax, N—neck, LHlateral horn, MH—median horn, A—abdomen, T—trunk, ES—egg sacs.

FIGURE 3. Lernaeenicus stromatei Gnanamuthu, 1953 ovigerous female ex Parastromateus niger (Bloch) Neotype (Reg. No. C-7146/2): A. habitus dorsal; B–C. head dorsal view; D. head dorso-lateral view; E. antennule; F. antenna; G. maxilla; H–K. leg 1–4.

FIGURE 4. Scanning electron micrographs of Lernaeenicus stromatei Gnanamuthu, 1953 ovigerous female ex Parastromateus niger (Bloch), A–E: A. leg 1–4; B–C. head dorsal view showing antennule and antenna; D–E. proboscis; F. light microscopic view of proboscis; P—proboscis, L 1 –L 4 —legs 1–4, A 1 —antennule, A 2 —antenna, S—spines on ventral surface of cephalosome, Md—mandible, SP—sac like plate, IS—intrabuccal style.