Pandarus rhincodonicus, Norman & Newbound & Knott, 2000

Norman, B. M., Newbound, D. R. & Knott, B., 2000, A new species of Pandaridae (Copepoda), from the whale shark Rhincodon typus (Smith), Journal of Natural History 34 (3), pp. 355-366 : 357-364

Pandarus rhincodonicus sp. nov.

(®gures 1±5)

Material

HOLOTYPE: female Western Australian Museum ( WAM) C 23238 ; ALLOTYPE: male WAM C 23239 ; PARATYPES: WAM C 23240. The senior author holds additional specimens and DRN holds the dissected material .

Female (®gures 1±3)

Body form shown in ®gure 1A and B. Length range 7.0±8.0 mm (mean = 7.6 mm, n = 10). Width range 3.83±4.28 mm (mean = 4.1 mm, n =10), with greatest width at cephalon, just anterior to the cephalon/thoracic junction. Height range 1.19±1.58 mm (1.4 mm, n =10). Although dorsal surface of body is smooth, pores are scattered across surface. Lateral margins of carapace are ¯eshy and with frill (®gure 2A).

Frontal plates well developed and narrow mesial extensions meet in midline. First pediger fused with head; hinder margin of cephalon with four or ®ve robust spines (sometimes heavily eroded), with another two on each extension of the cephalon. Dorsal thoracic plates on pedigers 2±4. Pediger 2: plates separate, extending beyond tip of pediger 3 almost to level of posterior limit of plates of pediger 4; straight posterior margin with four sharp spines. Plates of pediger 3 and 4 fused at their bases; posterior margins with shallow sinuses. Plates of pediger 4 extend over base of genital double somite. Genital double somite: almost circular; with well-de®ned posterior projections (separated by a narrow sinus), each bearing an upturned triangular projection dorsally; often with a sub-marginal setospine either side near base of the sinus (but lacking in the holotype). Abdomen onesegmented covered dorsally by plate longer than wide and not extending to level of tips of caudal rami; margins at the greatest width of dorsal plate curved ventrally, giving the appearance, from dorsal aspect, of a slight projection: ventrally, joined broadly to genital double somite and posteriorly terminating in broad plate extending between bases of caudal rami. Caudal rami stout, curved, L-shaped in cross section; lateral surface is oblique proximally and follows line of abdomen to just beyond the widest point of dorsal abdominal plate beyond which level the caudal ramus is deēcted outwards and tapers to a terminal spine which recurves slightly back towards midline of the animal. Upper margin of caudal ramus is sharply de®ned beyond the stout spine, which marks the beginning of the curve outwards and carries a second smaller spine; ventral surface with tubercle near the proximo-lateral corner and with thin seta and small spine on the mesial edge.

Oral area. Adhesion pads present at bases of antennule, antennae and maxillipeds. The surface structure of a pad is illustrated in ®gure 2B and C. Pads also present anteriorly on lateral expansions of thoracomere 2. Antennule (®gure 1C) of two articles: article 1 bearing 27 setospines, 21 stout and six small; article 2 bearing 12 naked, mostly curved, setae. Antenna of three articles (®gure 1D): terminal article bearing large curved terminal spine and two spines marginally; article 2 with two ventral spines, one mid-article on broad base, the other at the distal margin. Mouth tube (®gure 1E): of 10 females measured, oral cones 0.5±1.0 mm long, average 0.7 mm. Labrum ends in complex structure (®gure 2D). Labium with two terminal fringes of backwardly directed denticles (®gure 2D). Mandible (®gure 2D), with slender shaft ¯attened and dentate near the tip. Maxillule (®gure 1F) of two articles: basal article bearing 0 to two short setae; terminal article with large terminal, plus one small spine. Maxilla brachiform (®gure 1G): article 1 (lacertus) unarmed; article 2 (brachium) without ¯abellum, but with two distal spines, longer one fringed, shorter plumose; calamus bearing large claw with rows of spinules and apical patch of spinules. Maxilliped (®gure 1H) of two articles: basal article (corpus maxillipedus) stout with nacreous-like pad; article 2 (subchela) unequally bilobed, with nacreouslike pad, which works against pad of article 1.

Legs 1±4 biramose, each ramus of two articles, with spine and setal formula as follows:

Both rami of legs 1±3 (®gure 3A±C) with two articles. Both rami of leg 4 (®gure 3D) with one article; endopodite lacking spines. Leg 5 (®gure 3E) consisting of outer seta and inner lobe with single terminal spine. Adhesion pads and denticulate areas illustrated in ®gure 3A±D. Figure 2E shows detail of a denticulate region.

Egg strings (®gure 3F) slender, approximately same length as body, slightly curved. Eggs disc shaped.

Adult females vary in the extent of coloration. Colour patches dark chocolate± chestnut brown centrally shading outwards to transparent amber. Three colour patches occur on the cephalon, one anterior and triangular patches posterio-laterally. The considerable variation in the extent of separation to fusion between these three patches, resulting in considerable variation in the extent of amber-coloured areas about the eye spots, may be due to ontogenetic di erences. Colour patches also occur on frontal lobes; separately on segments 2 and 3 and at the bases of genital lobe projections; across most of segment 4 and abdominal segment (®gure 1A).

Male (®gures 4, 5)

Body form as in ®gure 4A and B. Length (not including setae on caudal rami) 5.2 ±7.2 mm (mean = 6.0 mm, n =5), width 2.9±4.3 mm (mean = 3.3 mm, n = 5) and height 0.84±0.94 mm (mean = 0.90, n = 5). Cephalon rounded when viewed dorsally with head and ®rst pediger fused. Segment 2 bears two pairs of dorsal spines; segments 3, 4 and 5 each bear one pair of dorsal spines. Pedigers 2± 4 free, without dorsal plates except for lateral wing-like plates on pediger 2. Genital double somite with posterior corners terminating in prominent triangular projection. Coiled spermatophores visible within genital double somite. Abdomen two-segmented. Caudal ramus bearing four long, plumose setae and series of ®ne setules along inner margin. Oral area as in female except for distribution of adhesion pads. Adhesion pad (®gure 4B) present at base of antennule (®gure 4C) approximatel y half the length, and positioned at greater angle towards centre of the cephalon, than is the case in the female. Small adhesion pad situated on base of antenna (®gure 4D). Absence of adhesion pads at base of maxilliped (®gure 4E) and on lateral projections of pediger 2.

Legs 1±4 biramose, each ramus of two articles, with spine and setal formula as follows:

Legs 1±4, ®gures 5A-D, which show the distribution of adhesion pads and denticulate areas. Leg 5 borne on genital double somite as lateral projection with three setae and one stout terminal spine. Leg 6 consisting of two setospines, outer longer than inner, borne on genital double somite near the origin of the abdomen.

Colour in life is pale pink and devoid of darker pigment.

Etymology

Rhincodonicus refers to the host of the copepods, the whale shark, Rhincodon typus .

Figures

FIG. 2. Scanning electron micrographs showing structures on the ventral surface of the cephalothorax of the female, and areas of the host skin grazed by Pandarus rhincodonicus: (A) lateral margin of carapace, showing`frill’; (B) scanning electron micrograph of the surface structure of an adhesion pad situated on the cephalothorax, the insert shows surface detail at higher magni®cation; (C) magni®cation of (B); (D) scanning electron micrograph of the labrum, labium and mandible; (E) denticulate region on pereopod; (F) photograph of a region of whale shark skin grazed by Pandarus rhincodonicus, black arrow to scar, white arrow to copepod.