Porcellidium viride ( Philippi, 1840 )

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 : 75-81

Porcellidium viride ( Philippi, 1840)

Figs 4–8

Thyone viridis Philippi, 1840:190 , pl. IV, fig 2.

Porcellidium subrotundum Norman, 1868 .— BradY, 1880: 169–170.

Porcellidium lecanoides Claus, 1889 .—Holmes & O’Connor, 1990: 66; HuYs et al., 1996: 308; Walker-Smith, 2001: 656; Wells, 2007:79.

Porcellidium viride .— BradY, 1880: 168–169; Lang, 1948: 420–422; Apostanov & Marinov, 1988: 101–102; Harris & Robertson, 1994: 301; Bodin, 1997: 65.

Porcellidium fimbriatum Claus, 1889 .— BradY, 1880 (female): 167; Thompson & Scott, 1903: 227; Sars, 1904: 76–77.

P. fimbriatum var. heraldicum .— Monard, 1928: 324–326; Monard, 1935.

Porcellidium sarsi .— Bocquet, 1948: 237–259; Holmes & O’Connor, 1990: 66–67; Harris & Robertson, 1994: 301; HuYs et al., 1996: 308; Walker-Smith, 2001: 656; Wells, 2007: 79.

Thyone viridis Philippi. —Vervoort, 1964: 119.

Type material. Due to the apparent absence of a type specimen for Philippi’s Thyone viridis , a male specimen, (identified as Porcellidium viride from Brady’s illustration of the antennule) is here designated NEOTYPE to give taxonomic stability to the genus Porcellidium and to allow sufficient definition of the specific characteristics to ensure recognition of Porcellidium viride .

Neotype designation. NEOTYPE adult male with antennules extended, length 0.63 mm, P90778 deposited at theAustralian Museum , SYdneY; collected from Laminaria digitata, Clachan, Seil Sound, Oban , Scotland (56°19'N 5°35'W), V.A. Harris 1997 .

Material examined (specimens here determined to be conspecific with the neotYpe): an adult female with egg mass detached, length 0.92 mm ( AM P90779) and other specimens (20 ♀♀, 8 ♂♂ and coupled ♂ + juv. ♀, AM P89054), deposited at AM, Sydney. Specimens from the same locality and species of seaweed (100 ♀♀, 50 ♂♂ and 6 ♂♂ + juv. ♀, and 4 slide mounted specimens) have been deposited at NHM, London. Slide material in NHM, London ( Porcellidium 339) and NMI, Dublin (see Appendix 1 and 2). Living material, identified as Porcellidium viride from a species specific feature of the male antennule shown in Brady’s (1880) illustration, was collected from Castle Head , Dale , Pembrokeshire (51°42'N 5°10'W), Clachan , Seil Sound , Oban , Scotland (56°19'N 5°35'W) and Loch HYne, Co. Cork, Ireland (51°30'N 9°17'W) and is part of the material examined. The following description is based on the neotype and this material examined .

Diagnosis. Male antennule segment 2 with first (proximal) seta more than twice length of second or third seta, five setae on segment 2 finelY plumulose, segment 3 with ventral process or “peg”, three coupling denticles on segment 4 are conspicuous denticulate pads, dactylus (segment 5) expanded, hooked distallY, segment 6 inconspicuous; ventral surface of male rostrum smooth, no U-shaped wrinkles or ridges, ventral surface of female rostrum V-shape (Fig, 6F); female caudal ramus rectangular, l/w = 2, terminal setae T2 and T3 thin, plain, very close together, posterior border between setae T3 and T4> 1/2 width of ramus, Hicks’ index for β seta 45–50%; boundarY between anterior and posterior lobes of female genital double-somite marked by a clear triangular area without border setules or dorsal pits, border of posterior lobe with three sensilla at edge; male P5 exopod almost rectangular, posterior angle 80°; females carrY 24 eggs. Spermatophore elongate, ephemeral on female.

Biometric data. Females (N = 50): maximum length (Lmax) 0.91 mm, body length to end of genital double-somite (Lurs) 0.89 mm, range 0.83–0.95 mm; cephalosome width (W) 0.60 mm, range 0.56–0.62 mm; rostrum width (R) 0.15 mm; genital double-somite width (N = 5) 0.38 mm, length 0.26 mm; caudal ramus length (N = 15) 0.14 mm [ramus dissected, laid flat], width 0.06 mm.

Ratios: Lurs / W 1.48; W/R 4.0; genital double-somite 63% of cephalosome width, w/l 1.45; caudal ramus 16% of Lurs, l/ w 2.3, Hicks’ index for β seta 50%.

Males (N = 16): maximum length 0.62 mm, body length to end of genital segment 0.49 mm; cephalosome width 0.52 mm; antennule (N = 7, fullY extended) 0.15 mm; apical angle of P5 75–80°; spermatophore length 0.21 mm.

Ratios: male antennule 30% of cephalosome width; antennule segment 2, 33%, segment 3+4 37%, dactYlus 24% of antennule length; first seta on segment 2 of antennule is 2.5–2.8 times length of seta 2; spermatophore 43% of bodY length Lurs.

Description. Adult females ( Fig. 4A ; Plate 1B, p. 67): pale yellow or colourless with variable patches of dark blue/purple on cephalosome and posterior of bodY (see Figs 4A , 8A, F, G, H, I and Remarks below). Cephalosome semicircular, rostrum broad (w/l 4.2), V-shape in ventral view ( Fig. 6F ). HYaline border with eight border sensilla surrounds cephalosome, 10 µm wide. Dorsal surface ornamented with circular pits 4–5 µm, surface ridge near antennule socket ( Fig. 8B, C ), ventral surface of cephalosome smooth (not wrinkled). Labrum with oval patch of minute setules ( Fig. 4F ). Genital double-somite ( Fig. 4C ) broad, semicircular in outline, no cleft or notch but clear triangular area without border setules or dorsal pits marks boundary between anterior and posterior lobes, three very small sensilla at edge of posterior lobe ( Fig. 4D ). Posterior arch deep (1/2 length of genital double-somite), encloses almost whole of caudal rami. Genital opening ( Fig. 4E ). Caudal rami ( Fig. 4B ) long, rectangular, feint ridges on dorsal surface, β seta half waY down ramus, γ seta and pinnate T1 slightlY recessed at lateral corner, T2 and T3 plain, slender, very close together (T2 pinnate on some specimens), space between T3 and T4 greater than half width of ramus, T4 pinnate at medial corner ( Fig. 4G ). Some of the setae on segment 2 of female antennule finelY plumulose ( Fig. 5A ). Structure and setation of mouthparts and ambulatory limbs typical of family. Antenna ( Fig. 5B ), endopod segment 2 with two lateral setae, ends of geniculate setae plain, claw comb-like ( Fig. 5C ). No patch of setules on anterior lobe of mandibular palp ( Fig. 5E ). Maxillule ( Fig. 5G ) with single bulbous seta on exopod, six setae on endopod. Coxae of maxilliped meet in midline ( Fig. 5H ). Limb P1, endopod segment 1 triangular, broad (l/w = 0.95), peg area inconspicuous ( Fig. 5F ). Serrulate spinous seta on segment 2 of P3 endopod ( Fig. 6G ) almost as long as endopod (0.9:1), large serrate spinous terminal seta on segment 3 longer than endopod (1.4:1). Spinous setae on P4 endopod segment 2 and 3 ( Fig. 6C ) longer than endopod (1.3:1). P5 exopod lanceolate with two plain dorsal setae (one sub-terminal and one apical), minute third seta present on some specimens ( Fig. 6H ). Females carrY 24 eggs per brood.

Adult males ( Fig. 8A ; Plate 1D, p. 67). Dark blue/purple area only on cephalosome, posterior of body colourless. Cephalosome truncated, anterior border straight, shoulder tightlY rounded. HYaline border, dorsal pits and ventral surface of cephalosome as for female, no ridges or wrinkles on ventral surface of rostrum. Caudal ramus sub-quadrate (l/ w 0.75), medial edge straight, lateral edge convex, dorsal surface with feint ridges, β seta 1/2 waY down ramus ( Fig. 8E ). First seta on antennule segment 2 more than twice length of second and third seta ( Figs 7G ), five plumulose setae on segment 2. Segment 3 with knob-like ventral process (no blade). Segment 4 with three conspicuous denticulate coupling denticles, (in some views they may appear as two denticulate pads, compare Figs 7A and 8D ). Aesthetasc short (more than twice length of segment 3+4). Segment 5 of dactYlus broad, 3/4 length of segments 3+4, hooked terminally, segment 6 very small, fused to segment 5 ( Fig. 7F ). Other limbs as for female except for the following: P2 endopod with two plumose terminal setae ( Fig. 6E ), setae on segments 2 and 3 of P4 endopod all plumose ( Fig. 6D ), P5 rhomboid (almost rectangular, Figs 7B, C ), first (lateral) seta longer than other setae, no setules at base of terminal setae, apical angle of P5 80°. Spermatophore 1/3 bodY length.

Remarks. Although Brady’s Porcellidium viride can be identified, the same does not applY to Philippi’s Thyone viridis . The reason Brady thought his animal was the same as Philippi’s Thyone viridis is the similarity of the P5 limbs. He saYs “There seems little reason to doubt the identitY of this species [ P. viride ] with Philippi’s Thyone viridis ; the serration of the lower border of the fifth foot is verY distinctive… ”, but this is a feature of nearly all male members of the Porcellidiidae . It may seem strange that Brady thought his animals the same as Philippi’s, but it is clear from his description and figure that he thought his own copepodid was an adult female. Brady had found P. tenuicauda (which he illustrates), and the adult female of P. viride which he identifies as P. fimbriatum , thus the only other animal he could compare with his (male) copepodid was Thyone viridis . It is important, therefore, to consider whether BradY’s sYnonYmY is justified.

Philippi gave a short (Latin) diagnosis of Thyone and then an extremely brief description of his T. viridis , “Almost 3/4" long, common. Masticatory apparatus extremely complicated”. The only clue to the animal’s identity is a confusing sketch (Fig, 25A). It shows an animal with six segments to its antennule, but they are not transformed like an adult male members of the Porcellidiidae . This tells us that it is not an adult male or male copepodid: it must be an adult female. But the posterior end of the body clearly shows male P5 limbs with six terminal setae and quadrate caudal rami, therefore Philippi’s animal must be a sage IV or V male copepodid. Thus there is a conflict as to the sex of the animal.

The shape of the body is even more confusing (see Fig. 24A ). It is egg-shaped and sharply truncated anteriorly with maximum width 1/3 down bodY. Adult animals of Claus’ P. tenuicauda are egg-shaped, but neither male nor female is truncated anteriorly. The males of both P. viride and P. fimbriatum are truncated anteriorly, but are not egg-shaped nor do they taper posteriorly. The females of these two species are oval and not truncated anteriorly. The copepodid of P. viride illustrated bY BradY (1880) is not egg-shaped; the posterior half is broadly semicircular like other copepodids ( Fig. 25B ). It is clear that Philippi’s animal cannot be identified with anY of the European species nor can BradY be justified in thinking it was the same as his animal. Philippi does not say whether he designated type specimens for his animal and no evidence has been found that suggests he did. Brady would not have provided a type specimen for his Porcellidium viride because he regarded it as a synonym for T. viridis . However, BradY (1880) illustrates the male antennules of P. viride which show the unique long first seta on segment 2. This feature is species specific and has not been found on any other member of the family. It allows the species to be identified with a high degree of certaintY and is the basis on which the present redescription of Porcellidium viride rests. Sars (1904) also shows this long seta in his illustration of Porcellidium fimbriatum which proves that his animals were P. viride .

Specimens from Wales and Scotland have a variable dorsal colour pattern of dark blue or purple on a pale yellow bodY colour ( Figs 4A , 8F,G,H,I and Plate 1B,D, p. 67). The frequency of colour variability found in one sample is shown below ( Table 1). Animals collected from Loch HYne, Ireland, have a single pale pink dorsal patch ( Fig. 4E ).

Collection data. Porcellidium viride has been collected from the following algae. Himanthalia elongata at Great Castle Rocks, Dale, Pembrokeshire Wales , ( CB7.7 /70, 209 ♀♀, 88 ♂♂, 4 coupled ♂♂ + juvenile), V. A. Harris 1970, 1974. Laminaria saccharina at Clachan, Seil Sound, Oban, Scotland ES 12.9/74, 71 ♀♀ (18 with eggs) , 21 ♂♂, 4 ♂♂ coupled to juveniles; ES14.9/74, 14 ♀♀, 3 ♂♂; ES17.9/74, 85 ♀♀ (7 with eggs), 60 ♂♂, 13 ♂♂ coupled to juveniles; ES18.9/74 (holdfasts), 55 ♀♀, 12 ♂♂, 2 ♂♂ coupled to juveniles. Laminaria digitata at Clachan, Seil Sound, Oban , Scotland ES19.10/74, 55 ♀♀, 12 ♂♂ ; ES20.10/74, 58 ♀♀, 23 ♂♂; ES23.9/97, 41 ♀♀, 9 ♂♂; ES25.9/97, 55 ♀♀ (25 with eggs), 39 ♂♂, 2 ♂♂ coupled to juveniles, V. A. Harris 1970, 1974, 1987, 1997. Ulva lactuca at Loch HYne, near Skibbereen, Co. Cork, Ireland LH3.9/97, 8 ♀♀, 6 ♂♂ , V. A. Harris, 1997.

Samples collected from Laminaria digitata also contain populations of P. fimbriatum .

Figures

Figure 4.Porcellidium viride (Philippi, 1840). Female:(A) adult showing tYpical colour pattern; (B) caudal rami (left ventral, right dorsal); (C) genital double-somite; (D) detail of genital double-somite posterior lobe; (E) genital opening; (F) labrum; (G) caudal ramus, terminal setae. Drawings of specimens from Scotland. Scale bar: A = 0.5 mm. B = 0.15 mm. C = 0.23 mm. E, F = 0.13 mm. G = 0.08 mm.

Figure 5. Porcellidium viride (Philippi, 1840). Female: (A) antennule; (B, C) antenna; (D, E) mandible; (F) P1; (G) maxillule; (H) maxilliped. Scale bar: A, B, G, H = 0.08 mm. E, F = 0.13 mm.

Figure 6. Porcellidium viride (Philippi, 1840). Female:(A) P2; (B,H) P5 (ventral and dorsal); (C) P4; (G) P3; (F) rostrum (ventral). Male: (D) P4 endopod. (E) P2 endopod. Scale bar: A, C, G = 0.18 mm. B, F, H = 0.23 mm. D, E = 0.15 mm.

Figure 7. Porcellidium viride (Philippi, 1840). Male: (A) detail of antennule coupling denticles; (B, C) P5 (ventral); (D) maxilla; (F, G) antennule (* peg or ventral process). Female: (E) showing extent of colour pattern of specimens from Loch HYne, Ireland. Scale bar: A = 0.06 mm. B, D, F, G = 0.08 mm.

Figure 8. Porcellidium viride (Philippi, 1840). Male: (A) adult showing tYpical colour pattern; (B) anterior cephalosome (dorsal); (D) antennule (anterior); (E) caudal ramus. Female: (C) anterior cephalosome (dorsal); (F, G, H, I) colour patterns (see text). Scale bar:A = 0.45 mm. B, C = 0.13 mm. D, E = 0.08 mm.

Figure 24. Porcelloides scutatus (Claus, 1860) comb. nov. Male: (A) adult; (B, C) antennule (ventral, π setae omitted in C); (D) rostrum and anterior border of cephalosome (ventral); (E) detail of coupling denticles on antennule; (F) spermatophore. Scale bar:A = 0.45 mm. B, C = 0.11 mm. D = 0.15 mm. E = 0.06 mm. F = 0.23 mm.

Figure 25. (A) Philippi’s 1840 drawing ofThyone viridis. (B) Male copepodid labelled “femalePorcellidium viride” (incorrectlY identified as an adult female) Brady (1880). (C) Porcellidium viride male antennules (showing verY long first seta on segment 2), BradY (1880). (D) Porcelloides tenuicaudus (Claus, 1860). Adult female with eggs and four spermatophores attached (freehand sketch of specimen in the NHM collection, V. A. Harris). (E) Female lifting body with P1 limbs to irrigate eggs.