Ameira longispina, Gee, 2009

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 : 2834-2845

Ameira longispina sp. nov

( Figures 13–18 )

Material examined

Holotype. An adult Ƌ dissected onto three slides NHM reg. no. 2009.190.

Paratypes. Eight ♀♀ (2 each dissected onto 3 slides, 2 each dissected onto 1 slide and 4 whole specimens spirit preserved); 13 long morph ƋƋ (2 each dissected onto 3 slides, 1 dissected onto 1 slide and 10 whole specimens spirit preserved) and 36 short morph ƋƋ (2 each dissected onto 3 slides, 1 dissected onto 1 slide and 33 whole specimens spirit preserved) NHM reg. nos. 2009.191–202; 2009.203–212. Unfortunately about 16 adult females were accidentally lost.

Description of male

Body. See Figure 13 . Small, length 0.360 –0.404 mm (mean = 0.388 mm, n = 23), semicylindrical, tapering slightly posteriorly from posterior border of cephalothorax, without clear distinction between prosome and urosome. Cephalothorax rounded anteriorly bearing minute, fused rostrum also rounded anteriorly bearing a pair of sensilla. Cephalothorax and free prosomites unadorned except for sensilla, distributed as in Figure 13A , and with plain hyaline frills. Urosomites with minutely dentate hyaline frills, sensilla and pores distributed as in Figure 13A–C . Urosomite-2 with small dorso-lateral row of minute spinules, urosomites -3 and -4 with complete ventral row of spinules; preanal somite with short median-ventral row of spinules. Anal somite with dorsal semicircular operculum between a pair of sensilla ( Figure 1E ), ventrally with faint row of minute spinules anteriorly and small spinules at base of caudal rami. Caudal rami very slightly longer than wide, with pore on dorsal surface and a few setules on inner margin; armed with seven setae arranged as in Figure 1E .

Antennule. See Figure 14A–B . Nine-segmented, segment-4 minute, segments -4 to -7 forming swollen portion, major articulation between segments -7 and -8 all setae smooth except for one slightly plumose seta on segments -1, -2 and -5 and a modified “pineapple” seta with a terminal flagellum on segments -5 and -7, aesthetascs on segments -5 and -9. Setal formula as follows 1-(1), 2-(10), 3-(8), 4-(2), 5-(4+1modified + (1+a)), 6-(1), 7-(2 + 1 modified + 1 spine), 8-(1 + 3 spines?), 9-(9 + (2+a)).

Antenna. See Figure 15A . Basis and enp-1 not completely separate forming indistinct allobasis, basal portion bearing a few setules on abexopodal margin and a small row of spinules near base of exopod, endopodal portion of allobasis unadorned. Distal endopod segment with widely spaced spinules on outer margin and two strong spines subdistally on same margin, with row of spinules medially on posterior face and on distal margin, latter also armed with five geniculate setae and a naked spine fused to base of inner seta. Exopod one-segmented with two or three strong spinules on inner margin, a row of minute spinules around inner distal corner and distal margin armed with three setae.

Mandible. See Figure 15B . Coxal gnathobase well developed, cutting edge with large bicuspid tooth at outer corner, a large triangular unicuspid tooth medially, an array of small multicuspid teeth and a plumose seta at inner distal corner. Basis wider distally than proximally bearing one large pectinate spine on distal margin and possibly a very delicate plumose element covered in small spherical particles. These are present in the position shown in Figure 15B in all the dissected specimens of both sexes but are often diffuse as in Figure 15B but occasionally seen as in Figure 15F for

one dissected female. Endopod well developed bearing one lateral and four terminal setae. Exopod absent.

Maxillule. See Figure 15C . Praecoxal arthrite with two setae distally on inner margin; dorsal surface with two setae; distal margin with two pairs of pectinate curved spines. Coxal endite with one naked and one distally ringed and spinulose seta. Armature of basis uncertain but probably with two or three setae on distal margin, possibly with a delicate structure (as described for mandibular basis) subdistally, endopod and exopod absorbed into basis represented by one seta each.

Maxilla. See Figure 15D . Syncoxa with two endites on distal margin; inner endite broad with one weakly-chitinized, fused seta with spinulose crown and possibly one delicate plumose seta similar to that described for mandibular basis; outer endite slender with two naked setae and a spine with a trifid tip. Allobasal endite with a fused claw and an articulating spine both bifid at tip. Endopod with two naked setae.

Maxilliped. See Figure 15E . Syncoxa with rows of spinules proximally and one plumose setae on distal margin. Basis oval, unarmed but ornamented with row of spinules on palmar margin and distally on outer margin. Endopod represented by a well-developed claw slightly longer than basis, with one accessory seta proximally.

P1. See Figures 16A and 19A . Intercoxal sclerite small, u-shaped and unadorned. Praecoxa small, triangular with row of spinules on distal margin. Coxa broader than long, with row of spinules proximally and distally on anterior face and a row of longer spinules near outer margin. Basis with small row of spinules on distal margin and at base of inner spine and outer seta. Inner spine sexually dimorphic, extremely enlarged, reaching to distal margin of enp- 1 in the long morph specimens ( Figure 16A ) or at least half length of enp- 1 in the short morph specimens ( Figure 19A ), slightly curved with a small cusp-like hook distally. Exopod three-segmented, segments about equal in length with row of spinules on outer margin and setules on inner margin; exp-2 without inner seta; exp-3 with two geniculate setae on distal margin and three spines on outer margin. Endopod three-segmented, enp-1 elongate, about equal in length to enp-2 and enp-3 combined and reaching distal margin of exp-3, inner margin with short stout plumose seta inserted at 75% of segment length; enp-2 only half length of enp-3, with row of spinules on outer margin and one seta on inner margin; enp-3 with one naked seta, one geniculate seta and one spine on distal margin.

P2–P4. See Figures 16B and 17A–B . Intercoxal sclerites bilobate. Praecoxa and coxa as in P1. Basis with row of long setules in P2 and short spinules in P3–P4 on inner distal margin and spinules on distal margin and at base of outer seta. All rami threesegmented and all segments with row of spinules on outer margin. P2 and P3 exp-2 and enp-2 with attenuated outer distal corner; enp-3 reaching to proximal part of exp-3. P4 exopod segments slightly more elongate than in P2 and P3; exp-2 without attenuated distal outer corner; exp-3 with three inner setae, middle one very well developed and spinulose, distal inner seta extremely fine, articulating on posterior face of segment; enp-2 without attenuated inner distal corner and enp-3 only reaching to distal margin of exp-2. Setal formula of swimming legs is presented in Table 3.

P5. See Figure 14C . Baseoendopod of each side fused medially, endopodal lobe well developed with pore on anterior face and distal inner margin projecting slightly, outer portion bearing two armature elements, an inner stout spine with pectinate tip and an outer close set small naked spine. Exopod oval with five armature elements, an inner small naked seta, a distal large minutely pinnate seta and three naked setae on outer margin, middle one (arrowed in Figure 14C ) extremely small and often only visible under ×100 oil immersion objective.

P6. See Figure 13C . One fixed and one articulating plate on posterior border of urosomite-2 each bearing three setae, inner and outer short, median seta long, reaching to posterior border of urosomite-4.

Description of female

As in male except for urosome, genital field, antennule P1 basis and P5.

Body. See Figure 18A–C . Slightly larger than in male, length 0.45–0.56 mm (mean = 0.512 mm, n = 5). Prosome as in male, urosome with segments -2 and -3 completely fused, line of separation marked only by very short lateral sub-cuticular rib ( Figure 18B ). Urosomites unadorned dorsally, posterior margin of genital double somite and following somite with short ventro-lateral row of spinules, pre-anal and anal somites as in male. Genital field ( Figure 18E ) with copulatory pore unusually far posterior, situated medially in posterior part of double somite, long copulatory duct leads to small paired seminal receptacles, genital slit connects paired genital pores, each covered by vestigial P6 bearing one short plumose seta, one long naked seta and a minute spinous process.

Antennule. See Figure 15G . Eight-segmented, segments -2 and -3 longest, aesthetascs on segments -4 and -8, all setae naked except for a plumose seta on segments -1 and -2. Setal formula as follows: 1-(1), 2-(9), 3-(8), 4-(3 + (1 + a)), 5-(1), 6-(3), 7-(4), 8-(5 + (2 + a).

P1 basis. See Figure 16C . Ornamented as in male but inner spine short, pointed, with a small setule near tip.

P5. See Figure 18D . Baseoendopod of each side separate with pore at base of peduncle bearing outer seta and near apex of endopodal lobe. Latter well developed bearing four armature elements, two inner spines with pinnate crowns and two pinnate setae, inner over twice as long as outer. Exopod semi-oval with a few spinules on inner margin and bearing five setae, inner seta pinnate, distal seta longest and middle outer seta very small (but more obvious than in male).

Etymology

The name refers to the long inner basal spine on the male P1.

Remarks

In their partial revision of the genus Ameira, Conroy-Dalton and Huys (1996, 1998 ) erected two new genera Filexilia Conroy-Dalton and Huys, 1996 and Glabrameira Conroy-Dalton and Huys, 1996 and reinstated the genus Psammameira Noodt, 1952 . Filexilia contains the following species previously allocated to Ameira in Lang (1948) and Bodin (1997): A. longicaudata Nicholls, 1939 , A. attenuata Thompson, 1893 , A. brevipes Kunz, 1954 , A. pestae Petkovski, 1955 , A. longifurca Bodin, 1964 , A. gravellicola Guille and Soyer, 1966 , A. intermedia Galhano, 1970 , A. brevipes pestae Marinov, 1971 , A. tenella Sars sensu Kunz (1983) . Filexilia is characterized by: (1) a slender elongate body and elongate caudal rami; (2) anal operculum bearing fine spinules; (3) female genital somite completely fused without internal rib; (4) female copulatory duct strongly chitinized and P6 with one pinnate seta and two spinous processes; (5) antennule elongate with very long setae on distal segments; (6) antennary exopod two-segmented, distal minute, proximal tapering towards base, convex outer margin with fine spinule rows and a distinctly recurved lateral seta; (7) male P1 inner basal spine recurved and unipinnate; (8) P2–P3 exp-2 and P2–P4 enp-1 without inner seta; (9) male P6 with three setae, middle one longest; (10) female P5 exopod elongate. According to Conroy-Dalton and Huys (1996) Filexilia is most closely related to Sicameira Klie, 1950 as they are the only two genera of Ameiridae to share the same elongate setae on the antennule and detailed structure of the antennary exopod.

The same authors erected the genus Glabrameira to accommodate Ameira bengalensis Rao and Ganapati, 1969 as it was intermediate between Filexilia and Sicameira because it had lost the inner seta on P2–P4 exp-2 (as in Filexilia ), had an elongate caudal ramus (as in both genera) and had only two spines on the female P5 benp (as in Sicameira ).

Conroy-Dalton and Huys (1998) reinstated the genus Psammameira to accommodate A. hyalina (Noodt, 1952) and A. parasimulans Lang, 1965 . A. simulans Scott, 1894 is maintained as incertae sedis in this genus. This genus belongs to a lineage of small interstitial ameirids which also includes A. listensis Mielke, 1973 , A atlantica Noodt, 1958 , A. atlantica mediterranea Kunz, 1974 and A. reducta Petkovski, 1954 . This lineage is characterized by: (1) a two-segmented antennary exopod bearing groups of spinules and a minute surface frill on exp-1; (2) maxillulary coxal endite with only one well-developed element; (3) a short P1 endopod with the proximal segment at most as long as the exopod; (4) a typical shape to the endopodal lobe of the male P 5 in which the inner distal margin is extended; (5) a 1:1:121 P4 endopodal setal formula; (6) denticulate or incized hyaline frills on the urosomites. According to these authors a unique apomorphy for Psammameira is the posteriorly-displaced copulatory pore and the long copulatory duct. This is found in a genital somite, which is almost completely fused only showing a short lateral subcuticular ridge and a P6 bearing a short plumose outer seta and an inner short spine.

The other species group within Ameira with which Conroy-Dalton and Huys (1996, 1998) compare their new genera is that of the type species A. longipes Boeck 1865 and includes A. minuta Boeck, 1865 , A. parvula (Claus, 1866) , A. Scotti Sars, 1911, A. parvuloides Lang, 1965 (and possibly A. tenuicornis Scott, 1902 , A. parascotti Chislenko, 1977 , A. usitata Klie, 1950 , A. bathyalis Becker, 1979 and A. faroensis Schriever, 1982 ). This group is characterized by: (1) a more robust body with some dorsal ornamentation, a naked operculum and short caudal rami; (2) a female antennule with the proximal segments short and stout; (3) an antennal exopod which is either one-segmented (e.g. Sars [1911] for A. longipes ) or two-segmented (e.g. Mielke [1974] for A. longipes and Moore [1976] for A parvula ) with straight sides tapering only slightly posteriorly, the outer margin bearing one or two stout spinules (as in Figure 19C ) and possibly a row of minute spinules on the anterior face; (4) mandibular basis with a pectinate spine, a normal spine and a flexible pinnate seta; (5) a maxillulary coxal endite with two elements and a basis with a minute, discrete, endopodal segment ( Figure 19D ); (6) a maxilla with only one syncoxal endite(?); (7) a P1 endopod with enp-1 at least as long as exopod; inner basal spine in male without spinules; (8) P2–P4 exp-2 with inner seta; enp-1 and enp-2 with inner seta and enp-3 with 1, 2, 2 inner setae on P2–P4 respectively; (9) P 5 female with 4:5 and male with 2:5 setae on baseoendopod and exopod respectively, exopod not elongate and male endopod without extended endopodal lobe; (10) female genital double somite with complete or almost complete subcuticular rib; (11) copulatory pore in anterior half of anterior portion of double segment and short copulatory duct weakly chitinized ( Figure 19B ); (12) female P6 with minute outer seta recurved anteriorly and two inner chitinous projections (see figure 189d in Lang [1965] and Figure 19B ); male P6 symmetrical with three elements, inner element spinous.

The present species always keys out to Ameira in any of the modern keys but from the foregoing it is difficult to place it in any of the groups outlined in the revisions of Conroy-Dalton and Huys (1996, 1998). These authors place great emphasis on the detailed morphology of the antennary exopod in defining their lineages and in this respect my species certainly agrees with the A. longipes lineage in that the proximal segment is adorned with two strong spinules on the outer margin and a row of fine spinules round the distal margin. Similarly, because there is no sexual dimorphism in the swimming legs, the setal arrangement on these limbs has also been used to define lineages and genera and my species again possesses the characteristics of the A. longipes group in this respect, which is the plesiomorphic condition for the whole complex. While my specimens also possess the general body shape, female P5, operculum, caudal rami, and maxillulary coxal endite of the A. longipes group, there are a number of significant differences: (1) there is no dorsal ornamentation on the body and the segments of the female antennule are more slender; (2) the mandibular basis has only one strong pectinate spine (and possibly a very flimsy, pinnate seta); (3) in the maxillule the endopod is completely absorbed into the basis and appears to be represented by one seta; (4) the maxilla has two syncoxal endites, the inner being globose and with two? elements; (5) the female genital double somite is almost completely fused with only a very short lateral subcuticular rib; (6) the copulatory pore in the female is situated in the posterior part of the double somite and connects to the seminal vesicles by a long copulatory duct; (7) the female P6 has two setal elements the inner of which is long and naked; (8) the male P5 endopodal lobe has a small inner extension and the male P6 is asymmetrical with three setae.

In features 1, 3, 4, 5, 6 and 8 our species is very similar to Psammameira and character 6 was given as an autapomorphy for that genus by Conroy-Dalton and Huys (1998). However, my specimens do not possess important features of that genus, namely the vermiform body, a rostrum defined at the base, the structure of the antennal exopod, the setal formula of the swimming legs and female P5 and the armature of the female P6 (in which the inner element is a short spine). This species should probably be placed in a separate genus but, because the revision of Conroy-Dalton and Huys is incomplete, I have decided to maintain it provisionally in the genus Ameira on the basis of the structure of the antenna and the setal formula of the swimming legs and P5.

This species can be distinguished from all others in the Ameira complex by the marked elongation of the inner basal spine of the male P1. In the holotype and 13 other males the spine extends to the distal margin of the elongate proximal segment of the endopod (as in Figure 16A ) whereas in the other 36 males the inner spine is two-thirds the length of the former type and reaches just past the middle of the proximal segment of the endopod (as in Figure 19 ). As there were no specimens with a spine length intermediate between these two conditions it is possible that there are two closely related species represented in this material. However, because I could find no other differences in the fine structure of the males or any character on which to separate the 24 females, I have not created two species but denoted them as a “long” and “short” morph. This course may be supported by the fact that out of 20 samples taken over a 64-m 2 patch of sand (see layout in Warwick et al. [2006]), 68 of a total of 74 specimens recovered were found in one 0.00156-m 2 sample.

Figures

Figure 1. Ameiropsis martinis sp. nov., female, urosomites 2–6. (A) Dorsal; (B) lateral; (C) ventral; (D) genital field; (E) rostrum and proximal segment of antennule; (F) segmentation of antennule; (G) P5.

Figure 13. Ameira longispina sp. nov., male. (A) Habitus, lateral; (B) urosome, dorsal; (C) urosome, ventral; (D) rostrum and proximal segment of antennule; (E) anal somite and caudal ramus, dorsal.

Figure 14. Ameira longispina sp. nov., male. (A) Antennular segmentation; (B) antennular setation; (C) P5.

Figure 15. Ameira longispina sp. nov. (A–E) Male: (A) antenna; (B) mandible; (C) maxillule; (D) maxilla; (E) maxilliped; (F–G) female: (F) mandibular palp; (G) antennule.

Figure 16. Ameira longispina sp. nov. (A–B) Male: (A) P1; (B) P2; (C) female: P1 basis.

Figure 17. Ameira longispina sp. nov., male. (A) P3; (B) P4.

Figure 18. Ameira longispina sp. nov., female, urosomites 2–6. (A) Dorsal; (B) lateral; (C) ventral: (D) P5; (E) genital field.

Figure 19. (A) Ameira longispina sp. nov., male P1 of “short morph”; (B–D) Ameira parvula: (B) female genital field; (C) antennal coxa, allobasis and exopod; (D) maxillule.