Spinoncaea ivlevi Böttger-Schnack 2003

SPINONCAEA IVLEVI (SHMELEVA, 1966) COMB. NOV. Synonymy Oncaea ivlevi Shmeleva, 1966 Original description Shmeleva (1966): 932–933, Fig. 1.1–1.9 (♀), 1.10–1.11 (♂) Other descriptions Shmeleva (1969): 5–8, 27, Fig. 3a–i (♀), Fig. 4a–h (♂); Malt (1982): 186–187, 193, Fig. 3a–k (♀), 4a–d (♂) Type locality Southern Adriatic Sea, Stn. 46: 40∞40.8¢N, 18∞50¢E; Stn: 47: 40∞57.6¢N, 18∞48.3¢E; 0– 500 m. Material examined See Table 3 (a). Preliminary note In the following, the typical, ‘robust’ form of S. ivlevi from the Red Sea main basin is described in detail. Morphological differences of a more elongate female form variant occurring in the southern Red Sea will be given below under ‘ Variability ’. The taxonomic identity of the 2 forms will be discussed by detailed comparison with specimens of S. ivlevi (Shmeleva) from the type locality in the Adriatic Sea, comparing and discussing also the taxonomic status of specimens from various other geographical locations. Description of female Body length (measured in lateral aspect; from anterior margin of rostral area to posterior margin of caudal rami, calculated as sum of individual somites): 400 Mm [traditional method: 338 Mm, range: 330–340 Mm, based on 5 specimens from the Red Sea]. Exoskeleton well chitinized. Prosome 2.4 times length of urosome, excluding caudal rami, 2.0 times urosome length including caudal rami. P2-bearing somite without dorso-posterior projection in lateral aspect (Fig. 2B). Integumental pores on prosome as indicated in Fig. 2 (A,B). Pleural areas of P4-bearing somite with rounded posterolateral corners. Proportional lengths (%) of urosomites are 8.8: 54.2: 8.8: 9.5: 18.7. Proportional lengths (%) of urosomites and caudal rami are 7.4: 46.0: 7.4: 8.1: 15.9: 15.2. P5-bearing somite with 2 paired midventral spinous processes (Fig. 2E). Posterior margin of genital double-somite and postgenital somites with lobate hyaline frill (Fig. 2C,D). Genital double-somite 1.8 times as long as maximum width (measured in dorsal aspect) and 1.4 times as long as postgenital somites combined; variation in length to width ratio as shown in Table 4; lateral margins rounded, largest width measured at halfway the distance between anterior and posterior margin, posterior part tapering slightly. Pore pattern and ornamentation on dorsal surface as in Figure 2 (C); ventral surface with numerous rows of minute spinules (Fig. 2E). Paired genital apertures located dorsally at about 2/5 distance from anterior margin of genital double-somite; armature represented by 1 diminutive spinule (Fig. 2J). 1 Beside several females of the intermediate ivlevi -form this sample also contained 1 ♀ ivlevi - type, which was similar to the elongate form, but differed in the form of the genital double-somite, with lateral margins more rounded than in typical S. ivlevi; the specimen is regarded as ‘ ivlevi of uncertain taxonomic status’ here. 2 Morphological characters intermediate between S. tenuis and the elongate form of S. ivlevi (CR length to width ratio and size of spine III; see text). 3 For details of morphological characters see text. Anal somite about as wide as long; slightly shorter than CR (measured along outer margin), or about as long as CR (measured along inner margin) (Fig. 2C), variation in length to width ratio as shown in Table 4. Paired dorsal sensillae anterior to anal operculum not found. Two pairs of secretory pores present dorsally near posterior margin. Anterior margin of anal opening (vestigial anal opening) with minute spinules. Posterior margin of somite finely serrate ventrally and laterally (Fig. 2C,D). Caudal ramus (Fig. 2F) 1.8 times longer than wide measured along inner margin and 2.3 times longer than wide measured along outer margin; variation in length to width ratio as shown in Table 4. Armature consisting of 6 elements (for numbering of elements cf. Fig. 12F): seta II small, spiniform, and unornamented; seta III very strong, spiniform and ornamented with few minute spinules along medial margin, base of seta laterally concealed by serrate margin of CR (Fig. 2D,F); seta IV less than 1.5 times as long as seta III, bipinnate; seta V longest, lanceolate, naked at anterior half, with short pinnules bilaterally at posterior half; this seta easily gets lost during handling; seta VI short, about as long as seta III, bipinnate; seta VII long, about 2/3 length of seta V, bipinnate and biarticulate at base. Inner margin of CR with row of setules. Dorsal anterior surface (Fig. 2F) with secretory pore near insertion of seta II. Antennule 6-segmented (Fig. 2G), weakly chitinized, relative lengths (%) of segments measured along posterior nonsetiferous margin 13.2: 12.7: 40.4: 13.2: 6.6: 13.9. Armature formula: 1-[3], 2-[8], 3-[5], 4-[2+ae], 5-[2 (ae not discernible)], 6-[5 + (1+ae)]. Aesthetasc on segment 4 very slender, aesthetasc on segment 5 not discernible, possibly absent [but see male, Fig. 5 (G)]; apical aesthetasc well developed and fused basally to adjacent seta. Segments 2 and 3 ornamented with short pinnules along nonsetiferous margin. Antenna 3-segmented, distinctly reflexed (Fig. 3A). Coxobasis with row of long spinules along outer margin and few spinules of varying length along inner margin; with very long seta at inner distal corner, ornamented with strong spinules of decreasing length bilaterally. Endopod segments about equal in length; proximal endopod segment elongate-oval, expanded outer margin bearing spinular row(s) and 1 strong spine; posterior surface with row of short, strong denticles along inner margin; 2 strong denticles on anterior surface. Distal endopod segment about 3 times longer than wide, with narrow cylindrical base articulating with the proximal endopod segment; posterior surface with row of short spinules along outer margin; lateral armature consisting of 2 bare setae, with seta II shorter than seta I, and 1 long spiniform seta (III), ornamented with strong spinules bilaterally at distal half and unilaterally at proximal part, seta IV absent; distal armature consisting of 4 long spiniform setae (A–D), ornamented with spinules bilaterally at distal part and sometimes unilaterally along entire length (A), 3 naked setae (E–G) of varying length, posterior seta (G) extremely small. Labrum (Fig. 3B,C) distinctly bilobed. Distal (ventral) margin of each lobe with 3 marginal teeth medially, differing slightly in size, long row of small spinules at outer ventral margin and row of small spinules or denticles along inner margin. Median concavity covered anteriorly by overlapping rows of fine spinules. Anterior surface (Fig. 3B) with paired row of long setules; median swelling weakly developed, with large secretory pore proximally. Posterior wall of medial concavity with two chitinized spinous teeth, flanked by row of minute denticles or spinules (Fig. 3C). Posterior face with 4 secretory pores located distally on lobe. Mandible (Fig. 3D) gnathobase with 5 elements: 3 setae and 2 blades. Ventral element (A) as long as ventral blade (B), with long, fine setules along dorsal side; ventral blade strong and spiniform, unornamented; dorsal blade (C) strong and broad, spinulose along entire dorsal margin; dorsal elements (D,E) setiform and bipinnate, element D very short and inserting near base of seta E, difficult to discern in some specimens. Maxillule (Fig. 3E) indistinctly bilobed, surface ornamentation not discernible. Inner lobe (praecoxal arthrite) with 3 elements: outermost element spiniform, swollen at base, ornamented with row of spinules and 1 coarse spinule, tip with tubular extension; middle element setiform and bare; innermost element smallest located along concave inner margin close to other elements, swollen at base and ornamented with 2 spinules. Outer lobe with 3 elements [innermost element absent]; outermost element curved and bare, similar in length to the following; element next innermost with long spinules unilaterally; innermost seta longest and bare. Maxilla (Fig. 3F) 2-segmented, allobasis nearly as long as syncoxa. Syncoxa unarmed, surface ornamented with1 large secretory pore. Allobasis produced distally into slightly curved claw bearing 2 small spinules on outer margin and 2 rows of strong spinules along medial margin; spinules of inner row shorter, proximal group of 3 spinules on outer row longer, small gap between proximal and distal group; outer margin with strong seta extending to tip of allobasal claw, ornamented with long spinules bilaterally at distal part; inner margin with slender naked seta and strong basally swollen spine with double row of long spinules along the medial margin and few spinules along outer margin (Fig. 3F). Maxilliped (Fig. 3G) 4-segmented, comprised of syncoxa, basis and 2-segmented endopod. Syncoxa unarmed, surface ornamentation not discerned. Basis elongate, palmar margin with 2 spiniform bipinnate elements, proximal element about half the length of distal one; fringe of short spatulated spinules between proximal seta and articulation with endopod; anterior surface with row of broad spatulated pinnules and short spinules of varying length along palmar margin as illustrated in Fig. 3 (G). Proximal endopod segment unarmed. Distal endopod segment drawn out into long curved claw, with pinnules along entire concave margin; accessory armature consisting of minute, naked seta on outer proximal margin and unipectinate spine fused basally to inner proximal corner of claw. Swimming legs 1–4 biramous (Fig. 4A–D), with 3- segmented rami. Spine and setae formula as shown in Table 5. Intercoxal sclerites well developed, without ornamentation. Coxae and bases with sparse surface ornamentation as figured. Bases with plumose (P1) or naked (P2–P4) outer seta, arising from posterior surface, longest in P4; inner portion of basis slightly produced adaxially into rounded (P1) or pointed (P2–P3) process, bearing short spinule(s) along inner margin in P1–P2 (Fig. 4A,B), pointed process smallest in P4. Inner basal seta on P1 spiniform and naked. Respective legs without distinct length differences between exopod and endopod. Bases of spines on exopodal and endopodal segments anteriorly surrounded by small spinules, hardly discernible in P2–P4. Surface ornamentation of all segments sparse. Exopods. Outer margin of exopod segments with well developed serrated hyaline lamella; inner margin of proximal exopod segments with long setules. Secretory pore present on posterior surface of distal segments, also present on anterior surface of P2. Hyaline lamellae on outer spines well developed; outer and terminal spines of P1 with subapical tubular extension, except for spine on exp-2 and proximalmost spine on exp-3. Spine on middle segment and proximal spine on distal segment of P2 reduced in length. Terminal spine equal in length to (P1) or shorter than (P2–P4) distal exopod segment. Endopods. Outer margin of endopod segments with fringe of long setules, except for first endopod segment of P4. Inner seta of proximal endopod segment short, slightly swollen and ornamented with spinules bilaterally (P1–P3) or spiniform with strong spinules bilaterally (P4). Inner setae of P4 reduced in length, in particular setae on middle segment, with proximal seta reaching little further than insertion of distal seta and distal seta reaching only half length of seta on distal segment. Distal endopod segments with large secretory pore in P1 and P4, located on anterior surface (P1) or on posterior surface (P4). Inner margin of P1 enp-2 ornamented with 2 long spinules (arrowed in Fig. 4A). Distal margin of P1 enp-1- and -2 ornamented with row of denticles or spinules on anterior face; outer margin of enpd-3 terminating in long process obscuring insertion of distalmost inner seta, process ornamented with short spinule. Distal margin of P2–P3 not produced into conical process, but apical pore of reduced process present, located laterally between subdistal and distal spine (Fig. 4B,C). Outer subdistal spine on P3 equal in length to outer distal spine, reaching as far as insertion of this spine. Inner setae of distal endopod segments in P2–4 with spinule comb along proximal inner margin; this comb less obvious in P1; also present on distal inner seta of middle endopod segment in P2–P4. P5 (Fig. 2I,H) comprised of long, naked seta arising from lateral surface of somite, and small free segment representing exopod. Exopod 1.6 times longer than wide, bearing single long, bare seta; posterior margin ornamented with small spinule ventrally (Fig. 2I) and small spinous process dorsally (Fig. 2H). P6 (Fig. 2J) represented by operculum closing off each genital aperture; armed with a short spinule, variable in conspicuousness (e.g. not discerned in specimen from Monterey Bay, cf. Fig. 7A). Egg-sacs paired (Fig. 2K), each sac containing 2 large eggs (diameter 40–50 Mm). Description of male Body length: 369 Mm [traditional method: 313 Mm, range: 310–320 Mm, based on 3 specimens from the Red Sea]. Pore pattern as in Fig. 5 (A). Sexual dimorphism in antennule, maxilliped, P6, and in genital segmentation, slight modification in setal length of P5. Proportional lengths (%) of urosomites (excluding caudal rami) 9.2: 61.3: 4.0: 4.0: 4.8: 16.7; proportional lengths (%) of urosomites (caudal rami included) 7.9: 52.6: 3.4: 3.4: 4.1: 14.3: 14.3. Posterior margin of leg 5-bearing somite with paired row of 2 or 3 midventral spinous processes (Fig. 5E). Caudal rami 1.9 times longer than wide measured along inner margin and 2.5 times longer than wide measured along outer margin, similar to female. Caudal setae with proportional lengths as in female. Dorsal surface of genital somite covered with minute denticles or spinules, arranged in a specific pattern (Fig. 5D) and a paired posterolateral pore. Surface of genital flaps and ventral surface of anal segment ornamented with several rows of strong denticles or spinules and a paired posterolateral pore (Fig. 5E,F). Ventral surface of caudal ramus with secretory pore near posterior margin (Fig. 5E). Antennule (Fig. 5G) 4-segmented; distal segment corresponding to fused segments 4–6 of female; relative lengths (%) of segments measured along posterior nonsetiferous margin 9.0: 19.3: 40.7: 31.0. Armature formula: 1-[3], 2-[8], 3-[4], 4-[9 + 2ae + (1+ae)], aesthetascs very small and slender, small middle aesthetasc close to seta, which is not discernible in the female, shown separately in Fig. 5 (G), apical aesthetasc fused basally to adjacent seta. Antenna as in female. Maxilliped (Fig. 5B,C) 3-segmented, comprising syncoxa, basis and 1-segmented endopod. Syncoxa with single secretory pore at inner distal margin, unarmed. Basis elongate, moderately inflated in proximal half, forming small bulbous swelling; anterior surface with row of short spinules along palmar margin, developed into small distal flap (Fig. 5B), short row of spinules proximally; posterior surface with 2–3 rows of short spatulated spinules of graduated length along palmar margin (Fig. 5B,C); with 1 long setae within the longitudinal cleft, ornamented with strong spinules bilaterally, corresponding to distal seta in female, proximal seta absent (Fig. 5B). Endopod drawn out into long curved claw, concave margin ornamented with pinnules along entire concave margin as in female; accessory armature consisting of short, unipectinate spine basally fused to inner proximal corner of claw; tip of claw without hyaline apex. P1–P4 with armature as in female; length of inner setae on middle segment of P4 as in robust form of female. P5 (Fig. 5E,F) exopod with general shape and armature as in female; exopodal seta and long seta arising from lateral surface of somite somewhat shorter than in female. P6 (Fig. 5E) represented by posterolateral flap closing off genital aperture on either side; covered by pattern of strong denticles as shown in Fig. 5 (E); posterolateral corners protruding laterally so that they are well discernible in dorsal aspect (Fig. 5D). Spermatophore oval (Fig. 5E), of variable size according to state of maturity; swelling of spermatophore during development not affecting shape and relative size of genital somite. Remarks Taxonomy. Shmeleva (1966) described both sexes of Oncaea ivlevi from the southern Adriatic Sea and figured the female habitus, antennule, antenna, maxilliped and swimming legs, as well as the dorsal aspect of the male. Later, she published a French version of the original Russian description by including material from the equatorial Atlantic and provided figures of the habitus, antenna, maxilliped and swimming legs for both sexes as well as the female antennule (Shmeleva, 1969). The setal count of female P3 differed between the 2 publications: the correct number of 2 setae is figured in the original description (1966: fig. 1.8), whereas only 1 seta was figured in the subsequent account (1969: fig. 3h). In both descriptions the inner seta on the distal endopod segment of P4 is lacking in the female (1966: fig. 1.9; 1969: fig. 3i), whereas in the male P4, the presence of this seta might be deduced from the insertion figured (fig. 4h). The inner seta on P4 can easily be overlooked, because it is located on the posterior surface of the segment (cf. Figs 3D and 5C,G). Shmeleva figured the basis of P2 with a long spine at the adaxially produced inner margin (1966: fig. 1.7; 1969: fig. 3g), which was not confirmed during the present study and is not found in any other oncaeid species known to date. Several other elements are incomplete or missing in Shmeleva’s figures, such as the number of elements on the caudal ramus in both sexes, the lateral and distal armature of the antenna and the armature of the antennule. Also, the level of detail required for taxonomic descriptions of oncaeids is not met by her figures (e.g. the ornamentation of the proximal basal seta and the distal endopod segment (claw) on the maxilliped are missing). Shmeleva erroneously described the exopod of P5 as having 2 setae (1966: p. 933), not just one, and did not mention the seta on the P5- bearing somite near the leg; it might be possible that she mixed up the two elements by mistake. In the male, the sexually dimorphic antennule and the lack of the proximal basal element on the maxilliped was not noted by Shmeleva (1966, 1969). Her description of sexually dimorphic distal endopod spines in P3 and P4, being shorter in the male (1969: fig. 4g,h), was not confirmed upon re-examination of specimens from the Adriatic and/or the Red Sea. Despite the differences between Shmeleva’s description and the present account, specimens from the Red Sea were regarded as conspecific with O. ivlevi on the basis of (1) the leg armature and (2) the possession of a very strong spinous seta III on the caudal ramus. The second character is also found in the closely related Spinoncaea humesi sp. nov., but differences in the leg armature clearly separate the two species (see below). The identification of Red Sea S. ivlevi was furthermore supported by comparison with specimens from the Adriatic Sea, which appeared to be conspecif
Published as part of Böttger-Schnack, Ruth, 2003, Taxonomy of Oncaeidae (Copepoda, Poecilostomatoida) from the Red Sea. V. Three species of Spinoncaea gen. nov. (ivlevi-group), with notes on zoogeographical distribution, pp. 187-226 in Zoological Journal of the Linnean Society 137 (2) on pages 193-207, DOI: 10.1046/j.1096-3642.2003.00056.x, http://zenodo.org/record/4634423
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