Sarsameira perezi Bodin 1970

Gee, J. Michael, 2009, Some new and rare species of Ameiridae (Copepoda: Harpacticoida) from the Isles of Scilly, UK, Journal of Natural History 43 (45 - 46), pp. 2809-2851 : 2829-2833

Sarsameira perezi Bodin 1970

( Figures 11–12 )

Material examined

Twelve ♀♀ (1 dissected onto 3 slides, 1 dissected onto 1 slide, 10 spirit preserved). Five ƋƋ (one dissected onto three slides, one dissected onto one slide, three spirit preserved). NHM Reg nos 2009.176–179; 2009.180–189.

Description of female

The species was originally described by Bodin (1970) from a single female of total body length 1.02 mm, found in fine sands around La Rochelle. Here I make a few additions and alterations to that description.

Body. Length of females (from base of rostrum to posterior border of anal somite) 0.695 –1.025 mm (mean = 0.877 mm, n = 8). Genital double somite completely fused with only small lateral subcuticular rib marking line of fusion. Genital apparatus with small copulatory pore only just posterior to genital slit, with reduced P6s forming small plates covering genital apertures, each armed with one large plumose seta. Posterior border of genital and two succeeding somites ornamented with row of minute spinules dorsally and laterally, slightly larger spinules laterally and a well-developed spinule row ventrally on urosomites -4 and -5. Anal somite ( Figure 11D–F ) wider dorsally than ventrally to accommodate dorsal flange to caudal rami which extends from triangular tapering body of ramus which is displaced laterally from ventral to dorsal so that inner margin is concave and outer margin convex, very deeply triangular in lateral view.

Antennule. As in Bodin (1970) with the following setal formula: 1-(1), 2-(10), 3-(8), 4-(3+(1+A)), 5 -(2), 6-(2), 7-(2), 8-(2), 9-(5+(2+A)).

Antenna. With basis. Exopod as in Bodin (1970); basis and enp-1 without setae on abexopodal margin; enp-2 with two spines and one seta subdistally on outer margin, distal margin with five geniculate setae and one spine.

Mouthparts. As in Bodin (1970) except I interpret basis of the maxillule as bearing one subdistal plumose seta and one naked and two plumose setae on the distal margin, endopod fused to basis and bearing one seta, exopod also fused to basis bearing one plumose and two naked setae. The endopodal claw of the maxilliped carries two accessory setae.

P1–P5. As in Bodin (1970).

Description of male

Differs from female in urosome, caudal ramus, antennule, P1 basis, P5 and P6.

Body. See Figure 11A–C . Length 0.687 –0.773 mm (mean = 0.723 mm, n = 4). Urosomites -2 and -3 completely separate. P6s two unequal plates each bearing three setae. Urosomite-3 with short lateral row of fine spinules and ventral row of larger spinules. Urosomites -4 and -5 with dorsal and lateral row of minute spinules and complete ventral row of larger spinules. Anal somite with short row of minute spinules on each side of ventral posterior margin. Caudal rami without dorsal flange, triangular, tapering posteriorly and not offset dorsal to ventral.

Rostrum. See Figure 12A . Small, only reaching half way up proximal segment of antennule, triangular, not defined at base, bearing two sensilla.

Antennule. Figure 12A–B . Subchirocer, 11-segmented, segments -6 to -9 somewhat swollen, major articulation between segments -9 and -10. Segment-1 with row of spinules on inner margin and tube pore near outer margin. Segments -9 and -10 with surface protrusions covered with minute spinules and with modified spines. Setal formula tentatively as follows: 1-(1), 2-(1), 3-(10), 4-(8), 5-(2), 6-(5 + (1+A)), 7-(2), 8-(2), 9-(3+1 spines), 10-(1+3 spines), 11-(9 + (2+A)).

P1 basis. See Figure 12D . Inner spine modified, stouter than in female and with a claw-like terminal structure surrounded by spinules on the posterior surface.

P5. Figure 12C . Baseoendopods of each side fused proximally, endopodal lobe not as developed as in female, bearing a surface pore and armed with five minutely pinnate spines, shorter and more robust than in female. Exopod oval, about twice as long as wide with a tube pore and a few spines on outer margin and bearing six setae, three on outer margin slender and naked, terminal seta long and minutely pinnate, two on inner margin minutely pinnate and less that half length of terminal seta.

Remarks on Sarsameira

Ameira exilis was first described by Scott and Scott (1894) and in more detail later the same year by Scott (1894) based on specimens of both sexes recovered by washing black sandy mud at low-water mark at Seafield, near Leith, Firth of Forth. Later, Scott (1898) found specimens at Fairlie and Hunterstone in the Firth of Clyde, and Thompson and Scott (1899) recovered specimens from holes dug in soft mud near Piel pier in Liverpool Bay. Sars (1920) figured and gave a more complete description of a single male he found at about 20 m depth at Risør, Oslofjord, and Lang (1948) also found it in Sweden at Väderö Island and in Gullmarfjord. More recently, Wells (1963) reported it as being frequently found at a site on the west side of the lower Exe estuary in Devon, and Hockin (1982) lists the species as a faunal constituent of the Ythan Estuary, Aberdeenshire. According to Scott (1894) this species can be distinguished from all others by its large, slender body (female 1.4 mm in length, male about 1.1 mm); the pyriform shape of the female caudal rami ( Scott 1894, pl. X, Fig. 12 ); the male however, has normal conical rami according to Sars (1920); a 9-segmented female antennule with segments -7 and -8 very small; a 10-segmented male antennule with the two long terminal segments both strongly hinged; a distinctly club-shaped mandibular palp; the segmentation and setation of the swimming legs (the same as shown for S. parexilis , except that Scott [1894] and Sars [1920] only found two inner setae in P4 exp-3 but both authors probably missed the minute distal seta shown here in Figure 9A ); the P 5 in both sexes with five and six setae on the endopodal lobe and the exopod respectively.

Primarily on the basis of the setal formula of this species Lang (1944) removed A. exilis from Ameira and placed it in a new genus Pseudosarsameira Lang, 1944 . However, Lang (1965) felt that in Sarsameira (Parameira) pendula (Shen and Bai, 1956) the armature of the P2 and P4 held such an intermediate position between Sarsameira and Pseudosarsameira that the latter monotypic genus should be incorporated in the former as Sarsameira exilis .

The specimens from the Scilly Isles were originally tentatively identified as S. exilis but on closer examination of both sexes the differences were significant enough to place the Scillies material in a different species. The females of the two species can only be distinguished by two characters: (1) body size – 0.81 mm is the maximum body size found for S. parexilis compared with 1.4 mm as the quoted size for S. exilis . The slight difference in methods of measuring body length and possible differences in methods of preservation are probably not sufficient to account for this large discrepancy. However, body size alone is not sufficient grounds for distinguishing species as different body size morphs are known to occur occasionally in species of harpacticoid, e.g. in Danielssenia typica as discussed by Gee (1988); (2) shape of the caudal rami – for S. exilis these have only been described by Scott and Scott (1894) and Scott (1894) as distinctly pyriform and are figured in both papers as being very wide at the base and narrowing sharply medially to a more slender distal portion, and very reminiscent of S. perezi in dorsal view. In S. parexilis the rami are almost square and taper only slightly proximally to distally.

In the male S. parexilis the maximum body length of 0.77 mm is also much smaller than the 1.1 mm recorded for S. exilis but the caudal ramus is the same as that figured for S. exilis by Sars (1920). However, two features of the male S. parexilis are distinctly different in the two species: (1) Scott (1894) describes and figures the male antennule of S. exilis as 10-segmented, he clearly shows that the second segment is short and bears only 1 seta and that there are only 2 segments distal to the major articulation, the terminal segment being a long slender segment with numerous setae. In Sars’ (1920) drawing (Pl XXXVII) the antennule is clearly 11-segmented, the difference being that the very small segment immediately anterior to the swollen section is clearly identified and there are still only 2 segments distal to the articulation. This antennule structure is exactly the same as that shown in Figure 12 for S. perezi . In S. parexilis the antennule is clearly 12-segmented ( Figure 10 ) there being 3 segments distal to the articulation as a result of the division of a long terminal segment into 2 shorter segments, but with the same total setal count as for S. perezi ; (2) all authors who have found the males of S. exilis agree that the setal counts on the baseoendopod/exopod of the P5 are 5/6, the same as in the female. In S. parexilis however there are only four setae on the baseoendopod and five on the exopod, one less than in the female, on each ramus.

Within Sarsameira the three species S. exilis , S. parexilis and S. perezi are unique in that the female antennule is nine-segmented rather than eight-segmented as in all other species. The position of the male antennule is more difficult to access because, apart from the descriptions for these three species, males are only known for six other species and in only two of these has any description or figure of the antennule been given. Reidenauer and Thistle (1983) describe the antennule of S. knorri Reidenauer and Thistle , as eight-segmented but they appear to figure a short segment-2 with only one seta and three short segments distal to the articulation. Kunz (1975) describes the antennule of S. elegantula Kunz as eight-segmented but figures it as nine-segmented with a very long segment-2, only three segments in the swollen section and three segments distal to the articulation.

Figures

Figure 9. Sarsameira parexilis sp. nov., female. (A) P4 (1–4 denotes continuation of corresponding setae); (B) P5.

Figure 10. Sarsameira parexilis sp. nov., male. (A) Urosomites 2–6, ventral; (B) segmentation of antennule; (C) setation of antennule; (D) P5.

Figure 11. Sarsameira perezi. (A–C) Male, urosomites 2–6: (A) dorsal; (B) lateral; (C) ventral; (D–F) female, anal somite and caudal rami: (D) dorsal; (E) lateral; (F) ventral.

Figure 12. Sarsameira perezi, male. (A) Antennular segmentation (and setation of segments 1 and 2); (B) antennular setation of segments 3–11; (C) P5; (D) P1 basis.