Luetkenia elongata Shiino, 1963

Uyeno, Daisuke, Senou, Hiroshi & Sakiyama, Tadao, 2016, Redescription of Luetkenia elongata (Copepoda: Siphonostomatoida: Pandaridae), an Ectoparasite of Luvarus imperialis (Actinopterygii: Perciformes: Luvaridae), with a New Record from Japanese Waters, Species Diversity 21, pp. 135-142 : 135-140

publication ID	https://doi.org/ 10.12782/sd.21.2.135
DOI	https://doi.org/10.5281/zenodo.5737806
persistent identifier	https://treatment.plazi.org/id/E87787BA-FFA6-FFF9-39EA-EA9DFBC1F806
treatment provided by	Felipe
scientific name	Luetkenia elongata Shiino, 1963
status

Treatment

Luetkenia elongata Shiino, 1963 ( Figs 1–5 View Fig View Fig View Fig View Fig View Fig )

Lütkenia elongata Shiino, 1963: 349–356 , figs 1, 2.

Type material. Lectotype: adult female (NSMT-Cr 20757), ex Luvarus imperialis Rafinesque ( Perciformes : Luvaridae ), 98.156km (as 35 miles) from the coast of California (32°38′N, 117°57′E), eastern North Pacific Ocean, 21 October 1962. Paralectotype: adult male (NSMT-Cr 24638), collection data same as for lectotype.

Other material examined. 1 adult female and 1 adult male (NSMT-Cr 24637), ex L. imperialis [ KPM-NI 39783 About KPM-NI : 1520 mm fork length (FL)] stranded in the surf zone of Enoshima island GoogleMaps (35°18′9.858″N, 139°28′56.094″E), Sagami Bay, western North Pacific Ocean, Kanagawa prefecture, Japan, 8 October 2015, leg. T. Sakiyama; 9 adult females and 8 adult males (KPM-NH 1772), collection data same for NSMT-Cr 24637 .

Adult female. Body ( Fig. 2A View Fig ) 14.19–20.97 (16.45±1.78) long (n =10). Prosome comprising cephalothorax and free thoracic somite. Cephalothorax ( Fig. 2A View Fig ) round, flattened dorsoventrally, with indented mid-lateral margin, wider than long, 4.56–5.48 (4.87±0.31)×5.22–5.94 (5.61±0.24), with pair of adhesion pads on each anterolateral corner ( Fig. 2F View Fig ), pair of longitudinal suture lines, and paired posterolateral lobes; frontal plates ( Fig. 2A, F View Fig ) without lunules. Free thoracic somite ( Fig. 2A View Fig ) wider than long, 1.40–1.72 (1.55±0.10)×2.98–3.38 (3.15±0.11), composed of fused second and third pedigerous somites, bearing pair of welldeveloped lateral plates with adhesion pad on anterolateral corner; sternite 1 ( Fig. 4A View Fig ) with posterior margin indented at middle. Urosome comprising fourth pedigerous somite, genital complex, and abdominal somite. Fourth pedigerous somite longer than wide, 5.38–6.42 (6.05±0.39)×3.16– 3.80 (3.52±0.20), with pair of elongate posterolateral lobes. Genital complex longer than wide, 8.27–10.32 (9.43±0.71)×4.09–4.44 (4.26±0.13), bearing elongate posterolateral lobes each with conical protuberance ( Fig. 2A, B View Fig ); genital apertures ( Fig. 2B, C View Fig ) situated adjacent surface of abdomen. Abdomen ( Fig. 2B View Fig ) teardrop-shaped, longer than wide, 3.30–3.99 (3.70±0.18)×2.44–2.97 (2.74±0.21), with indented lateral margin at posterior 3/4. Caudal ramus ( Fig. 2B, D, E View Fig ) longer than wide, 2.15–2.74 (2.49±0.20)×0.82– 1.22 (0.95±0.12), with six simple setae on distal tip. Egg sacs ( Fig. 1C View Fig ) uniseriate, straight.

Antennule ( Fig. 2F, G View Fig ) 2-segmented; proximal segment slightly shorter than terminal segment, bearing 16 spinulate setae and small, sharp process; distal segment bearing median seta in addition to aesthetasc and 11 setae on distal tip. Antenna ( Fig. 2H View Fig ) 3-segmented; basal (coxa) and middle (basis) segment unarmed; terminal claw (endopod) bearing single basal and single median elements. Postantennal process ( Fig. 2I View Fig ) represented by round process with three setulate papillae located on adjacent surface. Oral cone elongate. Mandible ( Fig. 3A, B View Fig ) represented by elongate, sharp stylet bearing single distal and 11 inner teeth. Maxillule ( Fig. 3C View Fig ) represented by rod-shaped lobe bearing three median, single small subterminal, and single long distal elements. Maxilla ( Fig. 3D View Fig ) 2-segmented; syncoxa rod-shaped, unarmed; basis slender, curved, ornamented with spinules, bearing blunt element, long calamus, and short canna; calamus and canna ornamented with serrate hyaline membranes. Sclerotized process ( Fig. 3E View Fig ) located on body surface adjacent to base of maxilla. Maxilliped ( Fig. 3F View Fig ) 2-segmented, subchelate; proximal segment (corpus) unarmed; terminal segment (shaft and claw) bearing tiny element.

Legs 1 to 4 biramous ( Figs 3G, H View Fig , 4B–E View Fig ); legs 1 to 3 bearing 2-segmented rami; leg 4 bearing unsegmented rami. Armature of legs 1 to 4 shown in Table 1. Leg 1 ( Fig. 3G, H View Fig ) bearing plumose setae on coxa and basis and simple setae on rami; intercoxal sclerite elongate, unarmed; endopod with row of spinules on terminal segment. Leg 2 ( Fig. 4B View Fig ) with intercoxal sclerite bearing row of hairs on posterior margin; protopod bearing five adhesion pads and two processes with conical tips on anterior surface and row of hairs on inner margin; basal segment of exopod bearing spinules on outer margin; terminal segment of exopod with serrate outer margin; endopod bearing row of hairs on outer margin. Leg 3 ( Fig. 4C, D View Fig ) with intercoxal sclerite bearing row of hairs on posterior margin; protopod bearing three adhesion pads and process with conical tip on anterior surface and spinules on outer margin; exopod with serrate outer margin; basal segment of endopod bearing rows of hairs on outer and inner margins; terminal segment of endopod bearing row of serrate teeth on anterior half and row of hairs on posterior half of outer margin and row of hairs on inner margin. Leg 4 ( Fig. 4E View Fig ) lacking intercoxal sclerite; protopod bearing spinules on distal tip; exopod bearing row of serrate teeth on outer margin and row of hairs on inner margin; endopod with row of hairs on outer margin and distal process ( Fig. 4F View Fig ). Leg 5 ( Fig. 4G, H View Fig ) located on distal part of ventral surface of posterolateral lobes of genital complex ( Fig. 2B View Fig ), represented by small lobe with outer conical spine and seta; seta of left leg 5 ( Fig. 4H View Fig ) distinctly swollen proximally.

Adult male. Body ( Fig. 5A View Fig ) 7.87–8.29 (8.10±0.15) long (n =9). Prosome comprising cephalothorax and free thoracic somite composed of fused second and third pedigerous somites as in female. Cephalothorax ( Fig. 5A View Fig ) round, flattened dorsoventrally, with indented mid-lateral margin, and longer than wide, 4.46–5.24 (4.83±0.22)×4.11–4.77 (4.53±0.24), with pair of longitudinal suture lines, and paired posterolateral lobes; pair of frontal plates ( Fig. 5A View Fig ) without lunules. Free thoracic somite ( Fig. 5A View Fig ) wider than long, 1.32–1.41 (1.35±0.04)×2.29–2.51 (2.41±0.08), with pair of well-developed lateral plates each with adhesion pad on anterolateral corner. Urosome comprising fourth pedigerous somite, genital complex, and abdominal somite. Fourth pedigerous somite wider than long, 0.91–1.05 (0.98±0.05)×1.53–1.64 (1.59±0.04), with pair of short, round posterolateral lobes. Genital complex, 1.50–2.53 (1.93±0.28)×1.44–1.71 (1.54±0.08), bearing round posterolateral lobes ( Fig. 5A, B View Fig ); genital apertures situated on ventral surface. Abdomen ( Fig. 5A View Fig ) pentagonal, 0.64–0.86 (0.72±0.07)×0.66–0.89 (0.81±0.07). Caudal ramus ( Fig. 5A, C View Fig ) longer than wide, 0.47–0.69 (0.62±0.06)×0.32–0.40 (0.37±0.04), with six simple setae on distal tip.

Antennule, antenna, mandible, maxillule, and maxilla as in female. Maxilliped ( Fig. 5D View Fig ) 2-segmented, subchelate; basal segment (corpus) bearing conical process and adhesion pad; terminal segment (shaft and claw) bearing element.

Legs 1 and 4 as in female. Leg 2 ( Fig. 5E View Fig ) as in female except protopod without distinct processes, and exopod with basal segment bearing row of spinules on outer margin. Leg 3 ( Figs 4I View Fig , 5F, G View Fig ) as in female, except endopod incompletely 2-segmented and bearing hook-like spine and two thinner spines in depression ( Fig. 5G View Fig ). Leg 5 ( Fig. 5H View Fig ) represented by conical process with scale-like spine and seta, located on posterolateral corner of ventral surface of genital complex. Leg 6 ( Fig. 5I View Fig ) represented by small, conical element situated on genital operculum.

Lectotype female. All characters as in other specimens from Japanese waters, except fourth pedigerous somite with damaged right postolateral lobe. Measurements of body parts as follows: body length 18.53; cephalothorax length 5.34; cephalothorax width 6.04; free thoracic somite length 1.59; free thoracic somite width 3.16; fourth pedigerous somite length 6.48; free thoracic somite width 3.85; genital complex length 11.69; genital complex width 5.66; abdomen length 4.66; abdomen width 3.43; caudal ramus length 2.66; caudal ramus width 1.26.

Paralectotype male. All characters as in other specimens from Japanese waters. Measurements of body parts as follows: body length 7.98; cephalothorax length 4.80; cephalothorax width 5.00; free thoracic somite length 1.29; free thoracic somite width 2.47; fourth pedigerous somite length 1.11; free thoracic somite width 1.55; genital complex length 1.89; genital complex width 1.67; abdomen length 0.81; abdomen width 0.77; caudal ramus length 0.56; caudal ramus width 0.36.

Infection sites. Females attached to the host’s body surface near the anal fin base ( Fig. 1A, B View Fig ). Males attached by antennae and maxillipeds to the urosome of females ( Fig. 1D, E View Fig ).

Infection number. Ten females and nine males from the single Japanese host specimen.

Remarks. Luetkenia elongata was originally described as the second member of the genus based on specimens of both sexes collected in the eastern North Pacific Ocean off California ( Shiino 1963). It differs from its congener, L. asterodermi , by the following characters of the female: fourth pedigerous somite with a pair of elongate posterolateral lobes on the dorsal surface (vs. small lobes); genital complex about twice as long as the cephalothorax and bearing a pair of well-developed posterolateral lobes each with conical protuberance on lateral corner (vs. not markedly longer than cephalothorax and bearing posterolateral lobes without protuberance); abdomen clearly longer than wide, with indented lateral margins (vs. equally wide and long, without indented lateral margins); and caudal rami more than twice as long as wide (vs. round, equally long and wide) (see Claus 1864, figs 10, 12; Kabata 1979, figs 986, 987). Although Shiino (1963) described leg 4 of the female with a total of five distal setae on the endopod, our reexamination of the lectotype showed that it bears only three setae.

Newly established Japanese name. “Mayoi-same-jirami-zoku” for the genus and “Mayoi-same-jirami” for the species. “Same-jirami” is the Japanese name for pandarids, meaning “shark lice”. Since the host of L. elongata is not an elasmobranch, “mayoi”, meaning “strayed” in Japanese is added. “Zoku” means “genus”.