Porcellidium rastellum, Harris, 2014

Harris, Vernon A., 2014, Porcellidiidae of Australia (Harpacticoida, Copepoda). I. A Reassessment of the European Species of Porcellidium, Records of the Australian Museum 66 (2), pp. 63-110 : 71-74

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https://doi.org/ 10.3853/j.2201-4349.66.2014.1594

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scientific name

Porcellidium rastellum

sp. nov.

Porcellidium rastellum sp. nov.

Figs 1 View Figure 1 –3

Type material. HOLOTYPE adult male, length 0.55 mm, P81207 ; ALLOTYPE adult female, length 0.80 mm, P81208, collected from Sargassum sp., sublittoral, Pontoon Rocks , Ballina, NSW, Australia, (28°52'S 153°36'E), V. A. Harris, 1982 GoogleMaps . PARATYPE specimens P81209 (20 ♀♀, 10 ♂♂, 10 ♂♂ + juvenile) and paratYpes P88552, P88553, P88554, all deposited at AM, Sydney. Specimens from the type series and Cronulla, SYdneY (50 ♀♀, 30 ♂♂ + 50 ♂♂ coupled to juv. ♀), deposited at NHM, London .

Diagnosis. Female rostrum horizontal bar, (in ventral view not V-shaped ( Fig. 1I View Figure 1 ), anterior edge of cephalosome folded ventrallY ( Fig. 1D View Figure 1 ), hYaline border not modified; maxilla with conspicuous rake-like claw ( Fig. 2G View Figure 2 ); P1 exopod segment 1 with conspicuous crescent of denticulate setules, endopod with extensive lateral and medial peg areas consisting of minute denticles arranged in rows ( Fig. 2E View Figure 2 ); male antennule first seta on segment 2 same length as second seta, no plumulose setae on segment 2, segment 3 without ventral process, three denticles on segment 4 none are denticulate pads; female P5 with broad medial dorsal expansion ( Fig. 1C View Figure 1 ). Spermatophore elongate, ephemeral on female.

Biometric data. Females (N = 15): maximum length (Lmax) 0.79 mm, range 0.76–0.81 mm, body length to end of genital double-somite (Lurs) 0.77 mm, range 0.74–0.81 mm; cephalosome width (W) 0.55 mm, range 0.54–0.56 mm; rostrum width (R) 0.12 mm; genital double-somite width 0.28 mm, length 0.19 mm, arch 0.9 mm; caudal ramus length 0.12 mm, width 0.05 mm.

Ratios: Lurs / W 1.41; W/R 4.6; genital double-somite w/l 1.5; caudal ramus 15% of Lurs, ramus, l/ w 2.4, Hicks’ index for α 72%, for β 14%.

Males (N = 9): maximum length (Lmax) 0.55 mm, body length (Lurs) 0.54 mm; cephalosome width 0.45 mm; antennule length 0.135 mm.

Ratios: Lurs / W 1.2; antennule 30% of Lurs; segment 2 30%, segment 3+4 46% and dactYlus 23% of antennule length.

Description. Adult females ( Fig. 1A View Figure 1 ; Plate 1A, p. 67): colour pale yellow, rostrum a horizontal bar in ventral view ( Fig. 1I View Figure 1 , not V-shape), wide (W/R = 4.2). The anterolateral edge of the cephalosome and hyaline border is folded ventrally as far as the second border sensillum, but without modification in structure ( Fig. 1D View Figure 1 ), hyaline border 8–10 µm wide, granular in appearance. Dorsal pits are conspicuous, very few dorsal sensilla. Labrum without ridge plates. Genital double-somite ( Fig. 1F View Figure 1 ) bordered with strong setules, dorsal surface pitted, anterior and posterior lobes separated by deep notch, posterior lobe rounded, arch about half length of genital double-somite. Caudal rami rectangular ( Fig. 1E View Figure 1 ), dorsal surface with pits, no setules on medial or lateral edges, terminal setae pinnate, T1 not recessed, T2 and T3 close together, T4 set in from medial corner which is slightly bevelled, β seta close to posterior border, fringe of setules on posterior edge between T3 and medial corner ( Fig. 1H View Figure 1 ). Structure and setation of ambulatory limbs and mouthparts typical of family. Basis of antenna with oblique double row of setules ( Fig. 2A View Figure 2 ), endopod segment 2 with three lateral setae, end part of geniculate setae plain, terminal claw comb-like. Mandible ( Fig. 2F View Figure 2 ) with strong molar process, small group of setules on anterior lobe of palp, maxillule ( Fig. 2C View Figure 2 ), maxilla endopod with conspicuous rake-like or ctenoid claw ( Fig. 2G View Figure 2 ), maxilliped ( Fig. 2B View Figure 2 ) normal. First ambulatory limb P1 with conspicuous crescent of rod-like denticles parallel to edge of exopod segment 1, endopod has broad band of denticles down medial edge and a large latero-central area of denticles which occupies nearlY 1/4 of the area anterior to the fimbriate crescent, denticles are minute and arranged in parallel rows, endopod l/w = 1.35 ( Fig. 2E View Figure 2 ). Serrulate spinous seta on P2 endopod segment 3 almost as long as endopod (Fig. 3A). Serrate spinous seta on P3 endopod segment 2 ( Fig. 2F View Figure 2 ) shorter than endopod (0.8:1), large serrate spinous seta on segment 3 much longer than endopod (1.4:1). P4 endopod segments 2 with straight serrulate spinous seta, serrulate spinous seta on segment 3 J-shape (Fig. 3B). Ventral seta on baseoendopod of P5 reaches back to level of lateral seta on exopod, P5 exopod ( Fig. 1C View Figure 1 ) lanceolate with broad dorsal medial expansion which partly covers genital double-somite ( Fig. 1A, C View Figure 1 ), there are two sub-apical dorsal setae and one short apical seta, dorsal surface of P5 pitted. Females carry eight or 10 eggs in brood chamber.

Adult males ( Fig. 1B View Figure 1 ) colour, dorsal pits and hyaline border as for female. Cephalosome truncated, shoulders smoothly rounded, lateral corner of antennule socket not prominent, anterior edge of cephalosome and hyaline border reflexed ventrallY (as in female) but not modified. Dorsal surface of genital double-somite pitted. Caudal ramus ( Fig. 1G, J View Figure 1 ) with bevelled medial corner makes ramus appear pentagonal, dorsal surface with pits. Setae as for female with β seta close to posterior border, T1 not recessed, T4 set in at base of bevelled medial corner, posterior fringe of setules extends past T4 along bevelled edge. Antennule ( Fig. 2D View Figure 2 ) segment 2 short triangular without plumulose setae, first seta not longer than 1.5 times other setae on segment, no ventral process or blade on segment 3, segment 4 with three coupling denticles, dactylus short, broad, segment 6 very small. Remaining limbs as for female except that P2 endopod has only two terminal setae (Fig. 3D) and setae on P4 endopod segments 2 and 3 are not spinous (Fig. 3E). P5 trapezoid with ventral row of setules to lateral seta but no setules at base of terminal setae, dorsal surface pitted (Fig. 3C).

Etymology. The specific name refers to the rake-like claw on the maxilla, (L. rastellum = a small rake Fig. 2G View Figure 2 ).

Remarks. Porcellidium rastellum differs from most other members of the genus in the large areas of very small denticles that appear to be arranged in rows on the ventral (anterior) surface of the P1 endopod.Another unusual feature is the way in which the anterior part of the cephalosome border is folded ventrally. This results in a portion of the hYaline border lYing in a ventral position. However, this does not correspond to the condition in Tectacingulum because there is no modification of the hYaline border and onlY the anterior part of the border is reflexed.

Figure 3. Porcellidium rastellum sp. nov. Female: (A) P2; (B) P4; (F) P3. Male: (C) P5; (D) P2 endopod; (E) P4 endopod.

Scale bar: A–F = 0.09 mm.

Distribution. The species has been recorded as abundant on several algal species from Nambucca, northern NSW (30°37'S) to Broulee (35°52'S), but not from HerveY BaY, Queensland (25°15'S) or Eden, southern NSW (37°06'S). Collected from Sargassum sp., Ballina, Bal12.11/82, 162 ♀♀, 44 ♂♂ + 90 ♂♂ coupled to juvenile female: Nambucca, Nb6.11/82, 141 ♀♀, 160 ♂♂ mostlY coupled. Rhodymenia ? TYpe series,Ballina, Bal14.11/82, 225 ♀♀, 176 ♂♂. Lobophora sp., Cronulla, Sydney, Cr19.8/75: Cr33.2/77, 100+, V. A. Harris 1975, 1977, 1982.


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