Bulbamphiascus scilloniensis, Gee, 2005

Gee, J. Michael, 2005, Two new species of Bulbamphiascus Lang (Copepoda: Harpacticoida: Diosaccidae) from Scotland and the Isles of Scilly, with additional observations on B. denticulatus (Thompson), Journal of Natural History 39 (22), pp. 1961-1979 : 1973-1975

Bulbamphiascus scilloniensis sp. nov.

( Figure 7 )

Bulbamphiascus imus (Brady) Wells (1961, 1970 ).

Material examined

Holotype: adult „ (dissected on to four slides) from intertidal sandflat on St Martin’s, Isles of Scilly, NHM Reg. No. 2004.4174. Paratypes: two adult ♀♀ (one dissected on to four slides) and three adult „„ from the same locality, spirit preserved, NHM Reg. Nos 2004.4175–4179; one ♀ and one „ spirit preserved, collected by the University of London Sub-Aqua Club ( USLAC) from sandy substrate, 20–30 m depth from Deep Point, Peninnis Head and Darrity’s Hole, St Mary’s, Isles of Scilly, NHM Reg. No. 1967.10.31.48.361.6.

Description of female

As in B. incus except as follows: body length 0.625 –0.785 mm (mean 50.648 mm, n 53). Urosome ornamentation ( Figure 7A, B ) consisting of a short row of strong spinules on ventral posterior margin of urosomite 4. Caudal ramus seta V without swelling at base .

Description of male

As in B. incus except as follows: body length 0.48–0.67 mm (mean 50.562 mm, n 55). Urosome ornamentation ( Figure 7C, D ) consisting of short row of strong spinules on ventral posterior border of urosomites 3 and 4.

Etymology

The species name refers to the Isles of Scilly.

Remarks

In the above material, all the males have the principal characteristics of B. incus , namely the anvil-shaped semi-hyaline structure on the basis of P2 (arrowed in Figure 7G ) and the outer chitinous apophysis and vestigial (or absent) distal outer seta of the male P5 exopod ( Figure 7F ). Although Wells (1961) described this seta as absent and the chitinous apophysis as a seta, an examination under ×100 oil immersion objective of his ULSAC material ( Wells 1970) indicated a P5 exopod exactly as drawn in Figure 7F .

The singular difference between the Scottish and Scilly Isles material is in the ornamentation of the urosome. No specimens from the Scilly Isles have any spinules on urosomite 5 and the spinules on the other somites are much coarser than in all the Scottish material. Indeed the body ornamentation of the Scilly Isles specimens is much more akin to that of B. imus as shown in Mu and Gee (2000, Figure 11B, C) than it is to the Scottish B. incus . In fact there is no difference between the two species in body ornamentation in the male and the only difference in the female is that the small ventro-lateral group of two to three spinules on urosomite 3 in most B. imus is absent in the Scilly Isles material, a very minor difference making a distinction between the Scilly Isles females and those of B. imus very uncertain.

The other difference between the Scottish and Scilly Isles material is in their habitats. The former was found in soft muddy sediments, high in organic material and probably with high levels of bacteria, judging by the number of filamentous bacteria attached to the specimens. The latter was recovered from clean, coarse sand, in an area completely free of organic or chemical pollutants.

That the Scilly Isles material is more closely related to B. incus as described above than to B. imus is clear from the structure of the male P2 endopod and P5 exopod. However, whether the differences in abdominal ornamentation are sufficient to accord the Scilly Isles material specific status, or are merely an expression of sub-specific population variation is more difficult to ascertain until more populations of Bulbamphiascus from a variety of habitats have been critically examined. However, I have decided to accord the Scilly Isles material specific status based on: (1) the fact that Mu and Gee (2000) found no difference in the abdominal ornamentation of two populations of B. imus down the east coast of England, or in populations of two closely related species of Bulbamphiascus they described from all over the Bohai Sea in China; (2) whilst, in my experience, it can be quite common for different species of a genus to have the same or very similar ornamentation patterns, I have not come across another case of the same species having significantly different ornamentation patterns on the urosome.

It is almost certain that all the records of B. imus from the Scilly Isles can be referred to this species ( Brady 1880; Wells 1961, 1970) and other records of B. imus , particularly from coarse clean sand and shell gravels, should be viewed with caution, e.g. Roe (1958) from Dublin Bay, Wells (1963) from Strangford Lough, and Geddes (1972) from Anglesey.

Figures

Figure 7. Bulbamphiascus scilloniensis sp. nov. ♀: (A) urosome (excluding urosomite 1), lateral; (B) urosome (excluding urosomite 1), ventral. „: (C) urosome (excluding urosomite 1), lateral; (D) urosome (excluding urosomite 1), ventral; (E) antennule segments 5 and 6; (F) P5; (G) P2 protopod (anvil-shaped hyaline structure arrowed).