Laophontodes norvegicus George, 2018

Karanovic, Tomislav, 2019, Three new harpacticoid copepods for Korea from marine interstitial habitats, Journal of Species Research 8 (3), pp. 268-282 : 274-278

Laophontodes norvegicus George, 2018

( Figs. 4 & 5 )

Specimen examined. Adult male on one SEM stub from Korea, South Sea, Goseong, Dongdong, Bongam-ri, tiny gravel beach next to a fishing harbor, 34°59.629 ʹ N 128° 26.201 ʹ E, 4 April 2012, collected by T. Karanovic .

Supplementary description. Male. Body length, measured from tip of rostrum to posterior margin of caudal rami (excluding caudal seate and appendages) about 360 μm. Habitus ( Fig. 4A, B ) relatively slender, nearly four times as long as wide, tapering posteriorly, slightly dorsoventrally compressed. Cephalothorax slightly longer than wide, representing about 25% of body length. Free prosomites and all urosomites with distal margin extend- ed laterally, forming a wavy line from ventral (or dorsal) view. Hyaline fringes of free prosomites and all urosomites (except anal one) serrated ( Fig. 5D ). Anal somite ( Fig. 5E, F ) with ventral row of large spinules at base of caudal rami.

Caudal rami ( Fig. 5E- H ) cylindrical, very slender, 2.2 times as long as anal somite, and 7.4 times as long as wide; with several spinules at base of lateral setae, one tubular pore ventro-laterally near anterior end and two tubular pores ventrally in posterior part. Proximal lateral setae inserted at about 3/5 of ramus length, dorsal one twice as long as ventral one. Distal lateral seta inserted close to posterior end, in level with larger ventral tubular pore. Dorsal seta inserted close to outer margin in level with distal lateral seta, but triarticulate at base (i.e., inserted on two pseudojoints; distal margin of second pseudojoint reaching distal margin of ramus). Inner apical seta about as long as ventral proximal lateral seta. Outer apical seta about as long as distal lateral seta. Central (principal) apical seta longest and strongest, half as wide as ramus and about five times as long, without breaking planes, pinnate distally.

Antennula ( Fig. 4C- F ) strong, chirocer, with strongly swollen fourth segment and tuft of spinules between setae on second segment.

Labrum ( Fig. 4G ) large, with narrow cutting edge and no ornamentation on anterior surface.

Maxilliped ( Fig. 5A ) with small seta at base of distal claw.

First swimming leg ( Fig. 4H ) with first endopodal segment about twice as long as entire exopod, nearly five times as long as wide, and 3.7 times as long as second endopodal segment.

Second swimming leg ( Fig. 5B, D ) with tubular pore on second exopodal segment and smooth inner margin of third exopodal segment (i.e. no inner seta); third exopodal segment slender, about 3.7 times as long as wide, and twice as long as second exopodal segment.

Discussion. Laophontodes norvegicus belongs to the Laophontodes typicus Scott T., 1894 complex, which was recently revised and split into six species by George (2018). Laophontodes typicus was described originally from Scotland ( UK) by Scott (1894). Subsequently, it was found in many locations along the European coast ( Scott, 1903; 1907; Norman and Scott, 1906; Sars, 1908; Jakubisiak 1933; 1936; Monard, 1935; Lang, 1948; Klie, 1950; Roe 1958; Ventham 2011), in the Arctic ( Scott, 1899; Chislenko, 1967; 1977; Kornev and Chertoprud, 2008), but also it was reported from very disjunct locations, such as the Chilean Magellan Region ( George, 1999; 2005) and the Great Meteor Seamount ( George and Schminke 2002). Not surprisingly, as it is often the case with widely distributed harpacticoids, a great range of intraspecific morphological variability was discovered, which enabled George (2018) to describe some new species even without studying any material. Laophontodes norvegicus was one of those, proposed as a new name for specimens studied and illustrated by Sars (1908) from Norway. Unfortunately, Sars (1908) did not illustrate male habitus but only provided illustrations of the male caudal ramus, antennula, fourth leg, and fifth leg (in addition to many female characters), so many details cannot be compared with the Korean male. However, the Norwegian and Korean populations share the very slender caudal rami, slender third exopodal segment of the second leg without inner seta, robust first endopodal segment of the first leg that is about twice as long as the entire exopod, and the habitus shape of the Korean male is not much dissimilar from that of the Norwegian female.

As for other species from this complex, they can be easily distinguished from Laophontodes norvegicus by some of the following characters: third exopodal segment of the second leg with inner seta ( L. typicus and L. monsmaris George, 2018 ), wide habitus ( L. scottorum George, 2018 ), or short caudal rami ( L. sarsi George, 2018 and L. gertraude George, 2018 ).

This record in Korea extends the species range (and the range of the entire complex) into the Pacific Ocean. It remains to be discovered if the species has a disjunct distribution, or if some of the Arctic populations from the L. typicus complex belong to it. George (2018) refrained from studying and discussing the Arctic populations, justifying that by the lack of characters provided in some redescriptions ( Chislenko, 1977) and some possible errors of observation ( Kornev and Chertoprud, 2008). However, this question would be difficult to answer without molecular data, which are still lacking for this complex.

Kim (2014) reported L. psammophilus Soyer, 1975 from Korea, but without any illustrations. This species also has long caudal rami, but it differs from L. norvegicus by much longer second endopodal segment of the first leg (see Soyer, 1975), and also by the insertion of the lateral seta on the caudal ramus (in anterior third in L. psammophilus vs. in posterior half in L. norvegicus ), so there is little possibility for confusion. However, Kim’s (2014) record would have to be checked and verified by an expert.

Figures

Fig. 4. Laophontodes norvegicus George, 2018, male 1, ventral view; A, CLM photograph; B-H, SEM photographs; A, habitus; B, habitus; C, antennula; D, detail of armature and ornamentation of proximal part of antennula; E, detail of armature and ornamentation of central part of antennula; F, detail of armature and ornamentation of distal part of antennula; G, labrum and mouth appendages; H, first swimming leg.

Fig. 5. Laophontodes norvegicus George, 2018, male 1, ventral view, SEM photographs; A, distal part of maxilliped and basis of first swim- ming leg; B, third exopodal segment of second swimming leg; C, tubular pore on second exopodal segment of second swimming leg; D, distal frill of fourth urosomite; E, caudal ramus; F, detail of ornamentation of proximal part of caudal ramus; G, lateral setae on caudal ramus; H, distal part of caudal ramus.