Porcelloides scutatus ( Claus, 1889 ) 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 : 98-104

publication ID	https://doi.org/ 10.3853/j.2201-4349.66.2014.1594
persistent identifier	https://treatment.plazi.org/id/03AF87A1-850E-FF82-4405-5ED9FD81D334
treatment provided by	Carolina
scientific name	Porcelloides scutatus ( Claus, 1889 )
status	comb. nov.

Treatment

Porcelloides scutatus ( Claus, 1889) comb. nov.

Figs 21–24 View Figure 21 View Figure 22 View Figure 23 View Figure 24

Porcellidium scutatum Claus, 1889: 34 , taf., VIII, abb., 9–18.

Porcellidium ovatum .— Lang, 1948: 442; Geddes, 1968: 14; Holmes & O’Conner, 1990: 66; HuYs et al., 1996: 307, 123; Wells (2007): 79.

Material examined. Spirit material and prepared slides in NMI, Dublin, collected bY D. Minchin and J.M.C. Holmes from Loch HYne (Ine), Co. Cork, Ireland (9°15'W 51°30'N), (see Appendix 2). Living material, used for measurements and the following description, was collected from red alga (? Gelidium sp.) Loch HYne, Co. Cork, Ireland and identified from species specific characters in Claus’ 1889 description of Porcellidium scutatum .

Specimens of Porcelloides scutatus (4 ♀♀, 5 ♂♂ and five dissections mounted on slides) have been deposited at NHM, London, V. A. Harris, 1997 .

Diagnosis. HYaline border appears striated; about 1/ 2 female caudal ramus lies in arch of genital double-somite; female caudal ramus trapezoid, apical angle 50°, bevelled edge almost equal in length to lateral edge, T1 and γ setae at lateral corner of bevelled edge, T2 normal, T3 very thin, inconspicuous, no setules along medial edge ( Fig. 22H View Figure 22 ); female P4 with massive serrated spinous setae on segments 2 and 3 of endopod ( Fig. 23B View Figure 23 ); ventral falciform ridge on female P5 undulating (wavy), apical seta pinnate ( Fig. 22D, E View Figure 22 ); terminal setae on male P5 exopod long (>1/2 length of lateral edge) .

Biometric data. Females (N = 11): maximum length (Lmax) 0.84 mm, body length (Lurs) 0.78 mm (range 0.74–0.83 mm) [female body length from literature 0.75–0.80 mm, Claus (1889)]; cephalosome width (W) 0.56 mm; rostrum width (R) 0.11 mm; genital double-somite width 0.38 mm, length 24.5 mm; caudal ramus length 0.135 mm, width 0.075 mm; apical angle of ramus 50°.

Ratios: Lmax / W 1.52, Lurs / W 1.4; W/ R 5.1 ; genital doublesomite width 68% of cephalosome width, w/l 1.54, length of posterior lobe 30% of lateral border, arch 40% of genital double-somite length; caudal ramus 17% of Lurs, l/ w 1.8, Hicks’ index for α seta 88%, for β seta 72 %.

Males (N = 8): maximum length (Lmax) 0.78 mm, body length (Lurs) 0.70 mm; cephalosome width (W) 0.53 mm; apical angle of caudal ramus 70°; antennule fullY extended 0.23 mm; spermatophore 0.25 × 0.087 mm (measured on female P5).

Ratios: Lmax / W 1.47, Lurs / W 1.3; antennule 43% of cephalosome width, segment 2 26%, segment 3+4 39%, dactYlus 28% of antennule length; spermatophore 36% of body length (Lurs).

Description. Adult females ( Fig. 21A View Figure 21 ; Plate 1F, p. 67): central area of cephalosome and metasome reddish-brown, rest of body colourless. Body ovoid in outline, dorsoventrally depressed, anterior slightly truncated, rostrum prominent with hyaline border, not obscured by anterior bulge of cephalosome. Animals do not conglobate. Dorsal pits conspicuous, 3–5 µm, area round pits slightly thickened to form cuticular network ( Fig. 21I View Figure 21 ), very few dorsal sensilla. HYaline border appears to have striations perpendicular to edge ( Fig. 21G View Figure 21 ). Striations due to network of ridges expanding out above hyaline border ( Fig. 21F View Figure 21 2 View Figure 2 , H), hYaline border itself is without striations ( Fig. 21F View Figure 21 1 View Figure 1 ). Cuticular striations 7–9 µm wide, hyaline border 11–13 µm wide ( Fig. 21F View Figure 21 2 View Figure 2 ). Labrum with central patch of very short setules plus group of about eight setules on either side of posterior edge ( Fig. 22G View Figure 22 ). Sternum of metasome segment 4 with fimbriate setules along posterior border. Genital double-somite short, broad ( Fig. 21B View Figure 21 ), small lateral notch and area devoid of pits or setules marks boundary between anterior and posterior lobes, posterior lobe short (1/3 of lateral edge), both lobes fringed with fine setules. Posterior arch almost half length of genital double-somite, accommodates anal segment and 2/3 of caudal rami (as far as lateral corner of the bevelled edge). Genital opening ( Fig. 21C, D View Figure 21 ). Caudal ramus trapezoid ( Fig. 21E View Figure 21 ), widens slightlY posteriorlY (maximum width 2/3 down ramus where bevelled edge starts), medial edge without setules, T1 pinnate close to γ at lateral corner of bevelled edge, T2 tends to lie almost parallel to bevelled edge, T3 very thin, inconspicuous, about 3 × length of terminal setules (difficult to see on some animals, Fig. 22H View Figure 22 ), T4 pinnate at apex of ramus, fine setules along bevelled edge between T3 and T4. Dorsal surface of ramus with network of ridges. Seta on first segment of antennule pinnate. Setation of mouthparts and ambulatory limbs typical of family. Antenna ( Fig. 22A View Figure 22 ) with filiform setules on basis and segment 1 of endopod, exopod with five plumulose setae and one spinous seta, segment 2 of endopod with proximal setules, one small and two larger lateral setae, one plain and one annulate terminal seta, three geniculate setae with plain distal portion, terminal claw with blunt serrations. Mandible without setules on anterior lobe of palp. Maxillule similar to P. tenuicaudus , maxilla ( Fig. 22B View Figure 22 ), maxilliped ( Fig. 22F View Figure 22 ). P1 ( Fig. 22C View Figure 22 ) exopod segment 1 with single crescentic row of denticles parallel to border, endopod with small triangular area of denticles at lateral end of fimbriate crescent, endopod l/w = 1.25. Serrulate spinous seta on segment 2 of P3 endopod thin, almost equal to length of endopod, large, serrate, spinous seta on segment 3 longer than endopod (1.5:1), ( Fig. 23C View Figure 23 ). P4 endopod with massive, short, serrate, spinous seta on segment 2 and a similar serrate seta on segment 3 ( Fig. 23B View Figure 23 ). P5 ( Fig. 22D, E View Figure 22 ), dorsal (external) seta on baseoendopod long (40 µm), exopod lanceolate with blunt apex (w/l = 0.26 at level of lateral seta), ventral falciform ridge undulating, two pinnate dorsal setae, seta at apex pinnate, border setules filiform, long (25–30 µm), dorsal surface with network of ridges. Females carry 12 eggs in brood chamber (N = 7).

Adult males ( Fig. 24A View Figure 24 ). Colouration, pits, network and striated hyaline border as described for female. Anterior outline of cephalosome rounded, slightly truncated with small convex projection in midline, lateral angle of antennule sockets with conical projection, rostrum V-shaped without ventral keel ( Fig. 24D View Figure 24 ). Caudal ramus trapezoid ( Fig. 23G View Figure 23 ), width greater than length (l/w = 0.9), medial edge straight, lateral edge slightlY convex, posterior 1/3 of both edges with setules, α and β setae long (3/4 width of ramus), terminal setae T1–T4 long, all pinnate, T3 larger than on female ramus, fringe of fine setules between T3 and T4. Antennule 43% of cephalosome width ( Fig. 24A View Figure 24 ), segment 1 with pinnate seta, no ventral process on segment 3, segment 4 with small serrated triangular proximal denticle, medial large denticulate pad, distal denticle with double serrated edge ( Fig. 24E View Figure 24 ), segment 5 of dactYlus slender, cYlindrical, 3/4 length of segment 3+4, hooked distallY ( Fig. 24B View Figure 24 ), segment 6 small and fused with segment 5. Ambulatory limbs as for female except for following. P2 endopod with two plumose setae on terminal segment ( Fig. 23D View Figure 23 ). P4 endopod segments 2 and 3 with long plumose setae ( Fig. 23E View Figure 23 ). P5 acutelY pointed trapezoid, setae long (2/3 length of lateral edge, first (lateral) seta pinnate with row of 7–8 ventral setules, remaining setae with 3–5 ventral setules ( Fig. 23A View Figure 23 ). Spermatophore reinform with recurrent neck ( Fig. 24F View Figure 24 ).

Remarks. The animals from Loch HYne, Ireland, correspond to Claus’ description of Porcellidium scutatum . For example, they are the same size and colour, the caudal rami are the same shape and have the same setation (Claus does not show T2, but as pointed out above this is hard to see on some specimens) and both have a long cylindrical dactylus on the male antennule. But the most compelling reason for regarding the two animals to be the same species is the unique hyaline border to the cephalosome. Claus states “ … surface at the edge of the cephalothorax with a clear outer margin set through with little rods” (taf.VIII, abb.18). Figure 21F, G, H View Figure 21 show the striated border of Porcelloides scutatus . Only two other species are known with a striated hyaline border, Porcellidium akashimum Harris and Iwasaki (1996a) and an undescribed Australian species of Kushia . The false border of Tectacingulum tumidum Harris, (1994) is striated, but the true hyaline border, which lies on the ventral side of the cephalosome, is not striated.

SuperficiallY, the female of Claus’ Porcellidium scutatum looks very different from Porcelloide tenuicaudus . The caudal rami are not acutely pointed or excluded from the arch of the genital double-somite. However, two features show that Claus’ P. scutatum belongs to the genus Porcelloides . The arrangement of denticles on the male antennule closely resembles that of Porcelloides tenuicaudatus , but differs from all other known species in the family. This together with the fact that two females from Loch HYne carrY eggs and an empty spermatophore on their P5 limb shows that Claus’ P. scutatum should be assigned to the new genus as Porcelloides scutatus ( Claus, 1889) , comb. nov.

Distribution. Living specimens of this species were collected from a red alga (? Gelidium ) in shallow water (10 to 40 cm) on the west side of Loch HYne,Co. Cork, Ireland, in deep shade from overhanging trees, LH4.9.97, 11 ♀♀, 12 ♂♂, V. A. Harris 1997.

Claus (1889) collected this species from rocks and Laminaria in Trieste Harbour, Adriatic Sea, but it has not been recorded anywhere else since. It is not found on the coast of Ireland, or the west coast of England and Scotland. Its presence in Loch HYne is surprising for it implies two widely separated isolated occurrences.

Loch HYne (Ine) in CountY Cork, Ireland, is a deep tidal marine loch, about one square kilometre in area, situated about one kilometre inland. It is connected to the sea by a very narrow channel and rapids through which sea water flows at high tide on the coast. Tidal swing in the Loch is only a few centimetres. It supports an extremely rich marine fauna that includes many Mediterranean (Lusitanian) species not found elsewhere round the coast of Ireland, England or Scotland. The inland location of the Loch would protect it from the extreme weather of the open coast and this suggests it may contain a relic fauna from a period when the climate was warmer. The Loch’s origin is uncertain but may represent a glacial lake that was replaced by sea water when sea-levels rose above the level of the rapids, due to changes in land or sea level. It is possible that Porcelloides scutatus represents a relic Lusitanian species that was once more widely distributed.

Animals belonging to Porcelloides have not been recorded from the Pacific region ( Australia or Japan).