Proameira cf. simplex ( Norman & Scott, 1905 )

Karanovic, Tomislav & Cho, Joo-Lae, 2012, Three new ameirid harpacticoids from Korea and first record of Proameira simplex (Crustacea: Copepoda: Ameiridae) *, Zootaxa 3368, pp. 91-127 : 117-124

Proameira cf. simplex ( Norman & Scott, 1905)

( Figs. 10–12 )

Material examined. South Korea, South Sea, Memuld Island, littoral, depth 33 m, 18 December 2010, temperature 15.1 °C, salinity 33.84 psu, pH 7.54, leg. W. Lee, 34.654683°N 128.593633°E: single damaged female dissected on one slide (collection number NIBRIV0000232641).

Redescription of female. Based on single damaged specimen habitus not drawn and body length not measured, as prosome almost completely squashed. Preserved specimen colourless. Nauplius eye absent. Body segmentation as in previous three species. Most somite ornamentation also similar to previous species, and presumably homologous pore and sensilla also indicated with same Arabic and Roman numerals and Greek letters (see Figs. 10 A, B, C, D, E, F, 11A) to allow easier comparison. Free pedigerous somites without lateral or dorsal expansions, pleural plates well developed but only partly covering coxae of swimming legs in lateral view. Integument relatively strongly chitinized and without cuticular windows or pits. Surface ornamentation of somites consisting of pores, sensilla, and several rows of spinules (latter on urosomites only); exact number of pores and sensilla unknown, but those homologous with previous three species indicated with Arabic and Roman numerals and Greek letters; those not present in previous species indicated with currency symbols (only five).

Surface of cephalic shield ( Fig. 10 A, B) ornamented with at least one unpaired pore (no. IV), four pairs of pores (nos. 11, 14, I, III), and 20 pairs of long sensilla (nos. 4, 6–8, 10, 12, 13, 15, 16, 18–20, 23–26, α, γ, $, £). Second pedigerous somite ( Fig. 10 D) with pair of pores antero-laterally (no. 28), and with nine pairs of long sensilla (nos. 27, 29–35, VII). Third pedigerous somite ( Fig. 10 E) also with antero-lateral pair of pores (no. 37), and with nine pairs of long sensilla (nos. 36, 38–45). Fourth and fifth pedigerous somites mostly missing. Hyaline fringes of cephalothorax and first two free prosomites braod and smooth.

Genital double-somite ( Fig. 10 F, 11A) flattened during dissection (as well as rest of urosome) about as long as wide; internal suture (remnant of segmental fusion) strongly sclerotised, visible dorsolaterally at midlength of somite, furnished with two parallel short rows of four to six strong spinules dorsolaterally, and four pairs of sensilla (nos. 59–62), anterior part of genital double-somite also ornamented with two lateral pairs of cuticular pores (nos. 63, VIII); posterior part of genital double-somite with single pair of lateral pores (no. 64), ornamented additionally with posterior row of large spinules (narrowly interrupted dorsally and in two places ventrally), and four pairs of posterior sensilla (nos. 67–70); hyaline fringe finely serrated. Genital complex ( Fig. 11 A) with single large copulatory pore, strongly sclerotized and wide copulatory duct and two small ovoid seminal receptacles. Single median genital aperture covered by fused reduced sixth legs, represents 51 % of somite’s width. Third urosomite ornamented with posterior row of spinules (interrupted dorsally), two unpaired dorsal cuticular pores (nos. 71, 74), two pairs of cuticular pores (no. 73,) ventrally and laterally respectively, and three pairs of posterior sensilla (nos. 75–77); unpaired dorsal pore no. 74 homologous to unpaired sensillum no. 74 in previous three species; hyaline fringe finely serrated. Fourth urosomite ornamented with single pair of lateral cuticular pores (no. 78), and short posterior row of slender spinules ventrally; hyaline fringe finely serrated. Anal somite ( Figs. 10 F, 11A) deeply clefted medially (especially ventrally, cleft reaching midlength of somite), with short remnants of transverse internal sclerotised ridge in anterior half, ornamented with pair of large dorsal sensilla (no. 81), six pairs of cuticular pores (nos. 80, 84–86, ¥, Ŧ), and ventro-lateral posterior row of spinules at base of each caudal ramus; anal operculum slightly convex, narrow, short, reaching 3/5 of anal somite and covering anterior half of anal sinus, represents 37% of somite's width, ornamented with posterior row of 22 small spinules along posterior margin on outer surface; anal sinus ornamented with two parallel diagonal rows of hair-like spinules on each side of median cleft, widely open, with strongly sclerotised walls, and without any chitinous projections.

Caudal rami ( Figs. 10 F, 11A) short, about half as long as anal somite in dorsal view, as long as wide (ventral view), slightly divergent and cylindrical (posterior part only slightly narrowing), with space between them about 1.7 times one ramus width, without dorsal diagonal suture in anterior half; with seven elements (three lateral, one dorsal and three apical); ornamentation consists of three spinules at base of large lateral setae, two spinules on posterior margin ventrally (at base of inner apical seta), single spinule at base of dorsal seta, and two pairs of pores (nos. 87, 88). Dorsal seta relatively short and slender, smooth, inserted on postero-median corner, about 1.4 times as long as caudal ramus, triarticulate at base. Lateral setae all smooth and slender; distalmost seta longest, inserted closer to ventral side and very close to posterior margin, five times as long as smaller proximal seta, twice as long as larger proximal seta, and three times as long as caudal ramus; proximal lateral setae inserted very close to each other in cuticular depressions similar to those of typical sensilla, inserted very close to dorsal side at about 3/4 of ramus length. Inner apical seta smooth, about 0.7 times as long as ventralmost lateral seta. Middle apical seta strongest, with breaking plane, finely bipinnate at middle third of its length, about as long as urosome and 1.5 times as long as outer apical seta. Outer apical seta also with breaking plane and strong, unipinnate along outer margin.

Antennula ( Fig. 10 G) eight-segmented, joined to cephalotholax with large triangular pseudosegment laterally, approximately half as long as cephalothorax, ornamented with two parallel short rows of spinules on first segment. Long aesthetasc on fourth segment slender, fused basally with adjacent much shorter seta, and reaching beyond tip of appendage for length of last seven segments combined; more slender apical aesthetasc on eighth segment fused basally with two much longer apical setae, forming apical acrothek. Setal formula: 1.9.8.4.2.3.4.7. Only one seta on second segment unipinnate, all other setae smooth. Two lateral setae on seventh segment and four lateral setae on eighth segment biarticulated at base, all other setae uniarticulated and without breaking planes. Length ratio of antennular segments, from proximal end and along caudal margin, 1: 1.4: 0.7: 0.5: 0.5: 0.6: 0.3: 0.6.

Antenna ( Fig. 11 B) composed of coxa, allobasis (fused basis and first endopodal segment), one-segmented endopod, and one-segmented exopod, although ancestral suture between basis and first endopodal segment visible in several places. Coxa very short, unarmed and unornamented, about twice as wide as long. Allobasis more than five times as long as coxa and about 2.6 times as long as wide, ornamented with several large spinules along inner margin proximally, unarmed. Endopod 3.7 times as long as wide and nearly 1.2 times as long as allobasis, with two surface frills subdistally, armed laterally with two strongly pinnate spines flanking thin seta; apical armature consisting of five geniculate setae, longest one fused basally to additional smaller seta; smallest seta bearing proximal tuft of fine setules; longest seta bipinnate, others finely unipinnate; ornamentation consisting of seven extremely large spinules on ventral surface, in groups of two, two, and three. Exopod more than twice as long as coxa, with narrow basal part and somewhat wider distal part; unornamented; with one lateral and two apical strong and unipinnate setae; dorsal (outer) apical seta longest, 1.1 times as long as ventral apical seta, about 1.4 times as long as lateral seta, and 1.7 times as long as exopod.

Labrum ( Fig. 11 C) large compared with cephalothorax, trapezoidal, rigidly sclerotized, with narrow and straight cutting edge, ornamented subapically with two rows of 12 strong spinules each, and apically with numerous minute spinules.

Paragnaths not mounted in satisfactory position to allow independent drawing or proper observation.

Mandibula ( Fig. 11 D) with narrow cutting edge on elongated coxa, with two tricuspidate strong ventral teeth, three bicuspidate strong teeth in dorsal half, single spinule at middle, and single dorsal unipinnate seta. Coxa ornamented with transverse row of six slender spinules on outer margin. Palp uniramous, comprising basis and one-segmented endopod. Basis with slightly inflated distal part, about 1.6 times as long as wide, with single strong and distally unipinnate inner seta, ornamented with three long and slender spinules along dorsal margin distally. Endopod small, unornamented, about 0.4 times as long as basis and 0.9 times as long as wide; with five slender and smooth apical setae, and one unipinnate inner seta.

Maxillula ( Fig. 11 E) with large praecoxa, ornamented with three parallel rows of spinules on outer margin; arthrite rectangular, square, with two long anterior surface setae, two lateral, and four apical elements (probably three spines and one seta); dorsalmost two apical elements strong and curved, with apical crown of slender spinules; third element from dorsal side most slender and smooth; ventralmost element extremely strong tooth, with wide and serrated distal margin. Coxal endite much shorter than praecoxal arthrite or basis, armed apically (on inner margin) with one stout and curved element, and another smooth and slender seta. Basis significantly shorter than praecoxal arthrite but more than twice as long as coxal endite,ornamented with arched row of spinules on posterior surface, with four smooth setae apically and subapically; dorsalmost seta strong, others slender. Endopod almost completely fused to basis, with single bipinnate slender seta apically.

Maxilla ( Fig. 11 F) ornamented with three transverse rows of long spinules along outer margin of syncoxa; opening of maxillary gland clearly visible on posterior surface. Proximal endite of syncoxa well developed, although not strongly sclerotized, with characteristically inflated ventral part; unornamented; with single apical setae, which fused at base to endite, slender, soft, and distally bipinnate. Distal endite of syncoxa cylindrical, well sclerotised and highly mobile, armed apically with one strong bipinnate seta, and two smooth and slender setae; smooth setae of subequal length, 1.5 times as long as pinnate seta, and 2.5 times as long as endite. Basis drawn out into long and strong claw, with shorter spiniform and curved seta at base, ornamented with minute pore on anterior surface, at base of seta. Endopod represented by minute but distinct square segment, with two long and smooth apical setae of subequal length; endopodal setae about 1.4 times as long as basal seta, not reaching distal tip of basal claw.

Maxilliped ( Fig. 11 G) with relatively long and stout syncoxa, ornamented with long arched row of spinules on inner margin, and with two subapical bipinnate setae of subequal length; syncoxal setae about 0.8 times as long as syncoxa. Basis 2.4 times as long as wide and 1.4 times as long as syncoxa, unarmed, ornamented with long and slender spinules along outer margin. Endopod represented by long curved claw, about 1.2 times as long as basis, ornamented with row of spinules along concave margin distally, accompanied at base by minute smooth seta.

All swimming legs ( Fig. 12 A, B, C, D, E, F) of similar size, long in comparison to body length, composed of small triangular and unarmed praecoxa, large rectangular and unarmed coxa, shorter and nearly pentagonal basis, slender three-segmented exopod, also slender and three-segmented endopod; each leg joined to their pair on opposite side of body by simple quadriform intercoxal sclerite.

First swimming leg ( Fig. 12 A) with smooth and nearly square intercoxal sclerite, its distal margin wide and slightly concave. Praecoxa larger than in previous three species, ornamented with short row of slender spinules on anterior surface along distal margin. Coxa 1.5 times as wide as long, ornamented with long spinules along outer and inner margins, additionally with two short transverse rows of spinules on anterior surface close to outer margin (one proximal and one distal), and one transverse row of four large spinules on anterior surface proximally and close to inner margin; single cuticular pore situated on anterior surface close to inner distal corner. Basis with one long and strong finely bipinnate spine on outer corner, and one even stronger and also finely bipinnate spine on inner distal corner; ornamentation consists of short rows of large spinules at base of each spine, as well as with distal row of spinules between exopod and endopod, several long and slender spinules on inner margin, and cuticular pore on anterior surface close to outer spine. Exopod with all segments of similar length, each about 1.8 times as long as wide and ornamented with spinules along both inner and outer margins (those on outer margin very strong and long); first two segments with single strong and finely bipinnate spine on outer distal corner; third segment with three strong and finely bipinnate spines on outer margin and two bipinnate setae apically (short pinnules along outer margin, long along inner); outer apical seta geniculate, inner seta not. Endopod geniculate and 1.5 times as long as exopod; first endopodal segment about as long as first two exopodal segments combined, 2.5 times as long as wide, ornamented with slender spinules along inner margin and strong and long spinules along outer and distal margins, with single inner seta, which about 1.6 times as long as segment, slender, and bipinnate, but also finely unipinnate along inner distal margin; second segment smallest, about twice as long as wide and only half as long as first segment, ornamented with several long an strong spinules along outer and distal margins, and with single slender and bipinnate inner seta; third segment slender, about six times as long as wide and twice as long as second segment, armed apically with three elements; innermost apical element probably spine, strong and 0.8 times as long as third segment, unipinnate along outer margin; middle element slightly more slender and geniculate seta, twice as long as outer element, unipinnate distally along outer margin; innermost element slender bipinnate seta, 1.7 times as long as outer element.

Second swimming leg ( Fig. 12 B) with intercoxal sclerite ornamented with four strong spinules on anterior surface, its distal margin wide and concave. Praecoxa small and triangular, ornamented with row of long spinules on anterior surface along distal margin. Coxa nearly 1.6 times as wide as long, ornamented with transverse row of small spinules on anterior surface proximally, diagonal row of eigth long spinules on anterior surface distally, and with long spinules along outer margin; single cuticular pore on anterior surface close to inner distal corner. Basis with single finely bipinnate and strong spine on outer corner; ornamented with spinules at base of spine, as well as with distal row of spinules between exopod and endopod, two rows of extremely long and slender spinules on inner margin, and cuticular pore on anterior surface close to outer spine. Exopod with all segments of about same width, third segment almost 1.7 times as long as second segment and 1.5 times as long as first segment; first two segments ornamented with strong spinules along outer margin, slender spinules along inner margin, single pore on anterior surface at base of outer spine, and with inner distall frill, each with outer finely bipinnate spine and inner bipinnate seta; third segment ornamented with pore near outer distal corner and spinules along outer and distal margins, with three strong and finely bipinnate outer spines, two apical bipinnate setae, and one slender and bipinnate inner setae; outer apical seta very strong (spiniform) with spinules along outer margin much shorter than those along inner margin, about 1.6 times as long as segment, and 2.3 times as long as outer spines; inner apical seta slender, with sparse long spinules on both inner and outer margins, as long as outer apical seta; inner seta 1.9 times as long as third segment. Endopod straight (not geniculate) and as long as exopod, progressively narrower from proximal to distal end, each segment with single pore on anterior surface close to outer distal corner, and row of strong spinules along outer margin; third segment about 1.5 times as long as first or second; first two segments additionally ornamented with strong frill on inner distal corner, and with single slender bipinnate inner seta; third segment with one inner seta, two apical setae and one subapical outermost spine; apical setae of equal length, bipinnate, 0.8 times as long as entire endopod, about as long as inner seta, and nearly 2.6 times as long as outer spine; outer apical seta on third segment with short spinules along outer margin and slender long spinules along inner margin; inner setae on second segment with short spinules along inner margin, and long spinules along outer margin.

Third swimming leg ( Fig. 12 C, D) very similar to second swimming leg, except for slender outer seta on basis, and three inner setae on third endopodal segment, and two inner setae on third exopodal segment.

Fourth swimming leg ( Fig. 12 E, F) similar to third swimming leg, except for length of outer basal seta (shorter on fourth leg) and armature of third exopodal and endopodal segments. Third exopodal segment ornamented with two spinules on posterior surface distally, in addition to outer spinules and anterior pore; with three outer finely bipinnate spines, two apical bipinnate setae, and three inner setae; distal inner seta minute, midlle inner seta very strong and with comb of strong spinules on inner margin distally, while proximal inner seta slender and bipinnate; inner apical seta slender and bipinnate, 1.2 times as long as much stronger outer apical seta, and slightly shorter than middle inner seta. Third endopodal segment with two inner setae.

Fifth leg ( Figs. 12 G) biramous, composed of wide baseoendopod and smaller ovoid exopod, with minute connecting plate and not fused medially. Baseoendopod with outer basal seta slender and unipinnate, arising from short setophore; baseoendopod with one cuticular pore on anterior surface at base of outer seta, and another near distal margin of endopodal lobe. Endopodal lobe relatively wide, trapezoidal, extending slightly beyond half of exopod, with five stout, bipinnate setae, with length ratio (from inner side), 1: 0.8: 1: 2.4: 0.8. Exopod about 1.6 times as long as its maximum width, ornamented with several long and slender spinules along inner margin, two proximal spinules on outer margin, one pore on anterior surface, and one pore on posterior surface; with six setae; innermost and fourth seta from inner side bipinnate, other four setae smooth; fifth seta from inner side minute. Length ratio of six exopodal setae, from inner side, 1: 2.1: 0.6: 0.7: 0.1: 0.5.

Sixth legs ( Fig. 11 A) completely fused together, indistinct, forming simple operculum covering single gonopore, without any ornamentation, each with two bipinnate setae and minute spine; inner seta pointing posterolaterally, about 1.7 times as long as outer seta, which pointing posteriorly.

Variability. Only one specimen was examined and no asymmetric features were observed.

Remarks. There is a limit to what one can do with a single damaged specimen. Comparisons based on a limited set of morphological characters will always be limited in their conclusions as well, even if one succeeds in securing type specimens of all potentially closely related species and comparing them morphologically. That is why we only provisionally identified this specimen as Proameira cf. simplex ( Norman & Scott T., 1905) . The record is significant enough to be worth reporting, as the genus Proameira Lang, 1955 has not been previously recorded in Korea, or indeed anywhere in Asia, or even in the Pacific. Hopefully, continuing sampling in the South Sea will result in more specimens of this population, which can than be studied in more detail and be compared to the types from England. Although the great geographical distance would suggest little chance of these two populations preserving an efficient gene flow naturally (and thus belonging to the same biological species), anthropogenic translocation of the world fauna these days is such that any unusual disjunct pattern cannot be rejected a priori (for a summary regarding copepods see Karanovic & Krajicek 2012).

Proameira is a rather small ameirid genus, with only nine species been described so far ( Walter & Boxshall 2011). Proameira arenicola (Lang, 1935) is known from Sweden, P. dubia (Sars, 1920) from Norway, Sweeden, and Israel, P. echinipes, 1975 from France, P. hiddensoensis (Schäfer, 1936) from Germany, P. phaedra (Monard, 1935) from France, P. psammophila Wells, 1963 from Ireland, P. signata Por, 1964 from Sweden, P. thetiensis Pallares, 1982 from Argentina (see Lang 1948; Klie 1950; Kunz 1954; Wells 1963; Por 1964a, 1964b; Soyer 1974; Pallares 1982). Almost all differ from our specimen by a number of morphological characters, such as the length of the first endopodal segment of the first swimming leg, shape of the fifth leg, and relative length of some elements on the swimming legs. Unfortunately, most descriptions of these species are lacking in detail, so many characters cannot be compared even with our very limited set of characters from a single Korean specimen (mouth appendages, for example, were studied only superficially previously, if at all). Nevertheless, having compared only the drawings and descriptions of these species (without access to types), we conclude that P. signata could possibly be a junior subjective synonym of P. s i m p l e x, as the morphological similarities are compelling, and the latter was recorded not far away from the type locality of the former ( Lang, 1948). Por (1964a) only compares his P. s i g n a t a to the very different P. arenicola , and not at all to P. s i m p l e x, so it is quite possible that he somehow overlooked the existence of P. simplex .

Proameira simplex was described originally from Devon ( England), and was subsequently recorded from Russia (Barents Sea), Norway, Sweden, Germany, France, Algeria, and the United States (see Lang 1948; Soyer 1966; Chislenko 1967; Kornev & Chertoprud 2008). The specific identity of the Algerian and American populations were questioned by Lang (1948). The original description by Norman & Scott (1905) is hardly usable today, as is their redescription ( Norman & Scott 1906). One of the most complete redescriptions so far is that by Sars (1907) (note: almost completely reproduced in Lang 1948), but this was done on Norwegian specimens. We have to concide that the identity of this species will remain problematic until a full redescription is supplied, based on the type material. The Korean specimen shows very few differences from those illustrated by Sars (1907), and most of them could be explained by the quality of microscopes available more than a century ago. For example, Sars (1907) does not illustrate the minute seta on the fifth leg exopod, but this armature element ( Fig. 12 G) could be observed only on the highest of magnifications, as it is smaller and certainly much thiner than most spinules on that segment. We are very confident that the absence of some ornamentation elements on the swimming legs (pores for example, and some rows of spinules) could be explained in the same way. Note that Por (1964a) did illustrate the minute seta on the fifth leg endopod for P. signata . The only difference between the drawings of Sars (1907) and our specimen that can not be explained in this manner is the relative length of the outermost seta on the fifth leg baseoendopod, which calls for caution in positive identification. This can, however, be a variable feature too. Por (1964a) showed that even the armature formula of the swimming legs can be variable in P. signata . We cannot answer these questions until more specimens of the Korean population become available, so that its variability can be studied.

Figures

FIGURE 10. Proameira cf. simplex (Norman & Scott, 1905), female: A, broken right side of cephalic shield; B, broken left side of cephalic shiled; C, broken dorso-posterior side of cephalic shield (drawn from inside); D, pleurotergite of first free thoracic somite; E, broken pleurotergite of second free thoracic somite; F, urosome without fifth pedigerous somite, dorsal view (compressed); G, antennula, ventral view. Arabic and Roman numerals and Greek letters indicating sensilla and pores presumably homologous with those in Ameira zahaae sp. nov., A. kimchi sp. nov. and Pseuameira mago sp. nov. respectively; currency symbols indicating unique sensilla and pores.

FIGURE 11. Proameira cf. simplex (Norman & Scott, 1905), female: A, urosome without fifth pedigerous somite, ventral view (compressed and drawn through dorsal side); B, antenna, anterior view; C, labrum, anterior view; D, mandibula, posterior view; E, maxillula, posterior view; F, maxilla, anterior view; G, maxilliped, anterior view. Arabic numerals and currency symbols indicating sensilla and pores as in previous figure.

FIGURE 12. Proameira cf. simplex (Norman & Scott, 1905), female: A, first swimming leg, anterior view; B, second swimming leg, anterior view; C, third exopodal segment of third swimming leg, anterior view; D, third endopodal segment of third swimming leg, anterior view; E, third exopodal segment of fourth swimming leg, anterior view; F, third endopodal segment of fourth swimming leg, anterior view; G, fifth leg, anterior view.