Phyllopodopsyllus thiebaudi santacruzensis Mielke,

Karanovic, Tomislav, 2019, Three new harpacticoid copepods for Korea from marine interstitial habitats, Journal of Species Research 8 (3), pp. 268-282 : 269-274

publication ID	https://doi.org/ 10.12651/JSR.2019.8.3.268
persistent identifier	https://treatment.plazi.org/id/78366243-B762-FFB6-9CD3-E04A1800FC7F
treatment provided by	Felipe
scientific name	Phyllopodopsyllus thiebaudi santacruzensis Mielke,
status

Treatment

1989 ( Figs. 1-3 View Fig View Fig View Fig )

Specimens examined. Four males and six females together on one SEM stub; one female dissected on one slide; and 25 males, 31 females, and 10 copepodids together in alcohol; all from Korea, South Sea, Goseong, Dongdong, small beach, 34°59.620 ʹ N 128°25.796 ʹ E, 31 March 2013, collected by T. Karanovic GoogleMaps .

Supplementary description. Female. Body length, measured from tip of rostrum to posterior margin of caudal rami (excluding caudal setae and appendages) from 575

to 595 μm (585 μm average, n = 12). Colour of preserved specimens yellowish, nauplius eye not visible. Habitus ( Figs. 1A View Fig , 2A, D View Fig ) cylindrical, slender, without distinct demarcation between prosome and urosome in dorsal view, but with sharp bend in lateral view; prosome/urosome ratio about 0.9 (in dorsal view); greatest width at posteri- or end of cephalothorax; cephalothorax 1.5 times as wide as genital double-somite in dorsal view; body length/ width ratio about 4.2. Free pedigerous somites without pronounced lateral or dorsal expansions. Integument of all somites relatively well sclerotized, generally smooth, covered with numerous shallow cuticular pits (see Fig. 2B View Fig ); several irregular rows of minute spinules present on each somite except cephalothorax, their density and size increasing towards posterior end of body. Hyaline fringes of all somites narrow; that of cephalothorax smooth ( Fig. 1B View Fig ), those of free prosomites coarsely serrated ( Fig. 1C View Fig ), those of urosomites (except anal somite) finely serrated ( Figs. 1D- F View Fig , 2C, E View Fig ). Surface of all somites, except preanal, with large cuticular sensilla, and some also with cuticular pores.

Rostrum ( Fig. 2B View Fig ) small, weakly demarcated at base from cephalothorax, linguiform, about as wide as long, its anterior tip not reaching beyond anterior margin of lateral wings of cephalothoracic shield, with single dorsal pair of anterior sensilla.

Anal somite ( Figs. 1F View Fig , 2C, E View Fig ) narrower and longer than fifth urosomite, almost completely devoid of spinules ventrally and with few minute spinules dorsally and laterally, cleft medially in posterior part, with posterior row of large spinules along ventral margin; anal operculum broad, narrow, and convex, with finely serrated posterior margin, representing about one half of somite’s width; anal sinus widely opened, without any chitinous projections, with weakly sclerotized walls and three rows of long, hair-like spinules boarding anus.

Caudal rami ( Figs. 1F View Fig , 2C, E View Fig ) strongly sclerotized, slightly longer and wider than anal somite, conical but with particularly inflated anterior dorsal region (with semi crescent lateral keel and median dorsal crater), generally smooth, ornamented with strong spinules along ventral posterior margin, and tuft of slender and long spinules in dorsal crater, slightly longer than wide, armed with seven setae (three lateral, one dorsal, and three apical). Dorsal seta slender and smooth, about 0.7 times as long as ramus, inserted close to posterior margin, triarticulate at base (i.e., inserted on two pseudojoints). Proximal lateral setae inserted very close to each other at about 3/5 of ramus length; ventral one minute, shorter than most sensilla; dorsal one slender and unipinnate, 0.8 times as long as ramus. Distal lateral seta also slender and smooth, inserted close to dorsal seta, and 0.4 times as long as ramus. Innermost apical seta smooth, slender, and small, about 0.3 times as long as ramus. Central (principal) apical seta without breaking plane, very strong, distally pinnate, about three times as long as caudal ramus, basally fused to outer apical seta. Outer apical seta also without breaking plane, much slenderer than central apical seta, smooth, nearly as long as caudal ramus.

Antennal exopod ( Fig. 1H View Fig ) slender, one-segmented, ornamented with several small spinules in proximal half and row of large spinules along distal margin, armed with one lateral and two apical setae; lateral seta inserted at about 4/5.

All swimming legs ( Figs. 1A, G View Fig , 2D, F, G View Fig , 3E- H View Fig ) slen- der, short in comparison to body length and width, composed of small unarmed and unornamented triangular praecoxa, large unarmed but ornamented quadrate coxa, smaller armed basis, three-segmented armed and ornamented exopod, and two-segmented armed and ornament- ed endopod. Coxae in all pairs of legs connected by unornamented intercoxal sclerite, each with concave distal end and no spiniform protrusions.

First swimming leg ( Figs. 1G View Fig , 3E View Fig ) with very long first endopodal segment, which about 1.4 times as long as entire exopod, and nearly five times as long as second endopodal segment; second endopodal segment armed with two apical elements, outer strong spine and inner long and geniculate seta; third exopodal segment slightly shorter than second.

Second swimming leg ( Figs. 2F View Fig , 3F View Fig ) with nearly square intercoxal sclerite and much shorter praecoxa than in first leg. Coxa with spiniform process on outer margin as in first leg. Basis armed only with outer spine. Third exopodal segment slightly longer and slenderer than other two; first exopodal segment armed with inner strong seta and outer strong spine; second exopodal segment armed only with outer spine; third exopodal segment armed with two outer strong spines, strong outer apical seta, slender inner apical seta, and slender inner seta. Endopod less than half as long as exopod, both segments ornamented with long spinules along both inner and outer margins; first segment armed with single short inner seta, second with three long apical elements (outermost one shortest, spiniform, and 1.5 times as long as segment).

Third swimming leg ( Fig. 3G View Fig ) very similar to second, except intercoxal sclerite narrower, basis with slender and long outer seta instead of spine, and third exopodal segment somewhat longer.

Fourth swimming leg ( Figs. 2G View Fig , 3H View Fig ) relatively similar to third leg, but with wider coxa, shorter basal seta, much shorter first endopodal segment armed with inner seta, slenderer seta on first exopodal segment, second exopodal segment armed with inner seta, and third exopodal segment with three strong inner setae; central inner seta on third exopodal segment exceptionally long and strong.

Fifth leg ( Fig. 1A, D, E View Fig ) typically foliaceous, twice as long as wide, with completely fused baseoendopod and exopod, forming brooding chamber with genital double-somite and anterior part of fourth urosomite, ornamented with row of hair-like spinules between base and basal slender seta and two cuticular pores on anterior surface. Former baseoendopod armed with three slender and pinnate setae, distalmost one longest. Former exopod armed with six setae; most proximal and fifth setae smooth and slender and inserted on anterior surface, others short, plumose, and inserted on distal margin; distal margin between second and third setae and between third and fourth setae transformed into bicuspidate chitinous processes, and between fifth and sixth setae transformed into finely serrated wide hyaline fringe.

Male. Body length from 514 to 560 μm (540 μm average, n = 8). Habitus shape ( Fig. 3A, C View Fig ), body proportions, and segmentation as in female, except second and third urosomites not fused, and caudal rami much more elongated. Ornamentation and shape of cephalothorax, all free prosomites, and most urosomites as in female.

Caudal rami ( Fig. 3B View Fig ) much larger in comparison with anal somite than in female, almost cylindrical but with prominent dorsal ridge and tapering towards posterior end, about 3.2 times as long as wide in ventral view and 1.7 times as long as anal somite; ornamentation and all armature as in female, except no dorsal spinules and proximal lateral setae inserted more anteriorly.

Antennula ( Figs. 2H View Fig , 3D View Fig ) strongly chirocer, robust, with almost all segments shorter than in female, with fused segments four and five, as well as seven and eight (resulting in apparent six-segmented state); sixth segment and ancestral segments four and five highly transformed into robust pincers with several chitinous ridges along area of contact; additional armature present on second, third, and ancestral fourth segments, while sixth and ancestral fifth segments with reduced armature (compared to female).

Discussion. Phyllopodopsyllus thiebaudi Petkovski, 1955 was described from interstitial habitats in the Mediterranean Sea (Petkovski, 1955), and soon afterwards discovered in numerous other localities in the Mediterranean, as well as in the Atlantic and Indian Oceans (see Lang, 1965; Karanovic, 2006). It has two accepted subjective synonyms (see Kunz, 1984; Bodin, 1997; Karanovic et al., 2001), one described by Noodt (1955) from the Atlantic coast of France (as P. intermedius ), and another by Apostolov (1969) from Bulgaria (as P. pirgos ). Karanovic (2006) redescribed it from Western Australia.

Mielke (1989) described a new subspecies from the Galapagos Islands, P. thiebaudi santacruzensis Mielke, 1989 , noticing a different number of armature on the male fifth leg exopod (four vs. five in the nominotypical subspecies). Karanovic (2006) added the length of the first endopodal segment of the first swimming leg as an additional distinguishing feature (much longer in the Pacific subspecies). Korean specimens have four setae on the male fifth leg exopod and first endopodal segment of the first leg at least 1.4 times as long as the entire exopod, so there is no doubt that they are more closely related to P. t. santacruzensis than to P. t. thiebaudi (see Fig. 3E View Fig ). This record implies a wide Pacific distribution of this taxon, which was previously considered to be endemic to the Galapagos. This is the third known species from this genus in Korea, after two new endemics were described by Karanovic (2017), both with close relatives in Japan. Today there are 61 valid species and subspecies in this genus globally (Karanovic, 2017; Walter and Boxshall, 2019).

Phyllopodopsyllus t. santacruzensis has a somewhat similar shape of the caudal rami to the Korean P. kitazimai Karanovic, 2017 , but the latter species has a slenderer habitus, smooth hyaline fringes of free prosomites, fewer setae on second to fourth swimming legs, fewer spinules on urosomites, and more cuticular organs on some somites (for example, an additional pair of pores is present on the anterior part of cephalothorax; compare Fig. 2B View Fig here and Karanovic, 2017: fig. 2C).