A new species of Odaginiceps Fiers, 1995 (Copepoda, Harpacticoida, Tetragonicipitidae) from the Mediterranean coast of Turkey

Abstract Male and female of Odaginiceps korykosensis sp. n. (Copepoda, Harpacticoida, Tetragonicipitidae), collected in the intertidal zone of Kızkalesi beach along the Mediterranean coast of Turkey (Mersin Province), are described. The new species is the fifth member of the genus and can easily be distinguished from the other species by the presence of four setae/spines on the second endopodal segment of P4 and by the structure of the caudal rami. Previously, representatives of the genus Odaginiceps have been reported from Gulf of Mexico, off Bermuda and Kenya. Odaginiceps korykosensis sp. n. is the first record of the genus in the Mediterranean Sea.


Introduction
Th e genus Odaginiceps Fiers, 1995 is one of the 12 genera currently recognized in the family Tetragonicipitidae and now comprises four species (Wells 2007). Th e genus was fi rst created by Fiers (1995) in one of his comprehensive and excellent papers on the Tetragonicipitidae from the Yucatecan continental shelf (Mexico). In this paper, Fiers (1995) described O. clarkae Fiers, 1995 from the West Central Atlantic (Quintana Roo State, Nichupte Lagoon, Cancun, Mexico) and designated it as the type species of the genus. In the same paper Fiers (1995) also described O. xamaneki Fiers, 1995 from the Western Central Atlantic (western region of Yucatecan continental shelf, Mexico). Th e third species (O. elegantissima Fiers, 1995) was also described and allocated to the genus by Fiers (1995) after reexamining the material previously identifi ed by Coull (1970) as Diagoniceps laevis Willey, 1930 from Castle Harbour (Bermuda). Fiers and De Troch (2000) later described the fourth species, O. immanis Fiers and De Troch, 2000, from the Indo-Pacifi c (Gazi Bay, Kenya). No other report of Odaginiceps has appeared in the literature since then. But the intensive investigation (carried out between 2000-2010) of over 500 phytal and interstitial harpacticoid samples taken from nearly 200 diff erent stations along the mediolittoral zone of rocky shores and sandy beaches of almost all Turkish coasts (unpublished data) revealed a new species of Odaginiceps which was found only in a single locality. Both sexes of this new species were described in detail below.

Material and methods
Samples were collected using the Karaman-Chappuis method (Delamare Deboutteville 1953) from the type locality on three diff erent dates (Table 1) but only one male and one female were obtained at the fi rst sampling (April 09, 2007). Prior to dissection, the habitus was drawn from whole specimens temporarily mounted in lactophenol. Specimens were dissected in lactic acid and the dissected parts were mounted in lactophenol mounting medium. Broken glass fi bres were added to prevent the animal and appendages from being compressed by the coverslip and to facilitate rotation and manipulation, allowing observation from all angles. Preparations were subsequently sealed with Entellan® (Merck). All drawings were prepared using a camera lucida on Olympus BX-51 diff erential interference contrast microscope. Total body length was measured from the anterior margin of the rostrum to the posterior margin of the caudal rami. Measurements were made with an ocular micrometer. Scale bars in illustrations are in μm. Th e descriptive terminology is adopted from Huys et al. (1996). Abbreviations used in the text are: ae, aesthetasc; P1-P6, for swimming legs 1-6; exp Description . Female (Fig. 1A, B). Total body length 770 μm, with largest width measured at cephalothorax. Integument of cephalic shield smooth, of all other somites ornamented with irregular pattern of hardly visible spinules. Body surface with sensilla pattern as fi gured. Posterior margin of the body somites with serrate hyaline frills. Rostrum ( Fig. 1A) large, widest at base, extending halfway along second antennular segment; with two delicate sensillae and a mid-dorsal pore.
Urosome (Figs 1A,B) 5-segmented, comprising P5-bearing somite, genital double somite and three free abdominal somites. Genital double-somite longer than wide; with transverse surface ridge dorsally and laterally (  present on ventral surface near the base of seta III ( Fig. 2A); with seven setae (Fig. 3D, E), seta I minute located near the base of seta II; setae II-III bare; setae IV-V strongly developed and bipinnate; seta V with swollen sinuate base; seta VI short and as long as seta III; seta VII tri-articulated.
Antennule (Fig. 3A) 9-segmented; segment 1 with a long plumose seta at anterodistal margin, a spinular row on anterior surface, long spinules along inner margin, small tube-pore on dorsal surface near inner margin. Segment 2 with long spinules on caudal margin. Segment 4 with long aesthetasc fused basally to seta. Segment 9 Antenna (Fig. 3B). Coxa small and smooth. Basis with 2 long spinules at outer margin. Exopod 1-segmented with one lateral pinnate seta, apical armature consists of one pinnate seta and one pinnate spine; a few spinules present around outer distal corner and midway along outer margin. Endopod 2-segmented; fi rst endopod segment with one plumose seta at proximal third of outer margin. Distal endopod segment with various spinular rows as fi gured and with two abexopodal unipinnate spines laterally (both spines with subapical tubular extension). Apical armature of enp-2 consisting of two pinnate setae, and fi ve geniculate setae; longest geniculate seta with large spinules and fused at base to long pinnate seta. Labrum (Fig. 4D). Free margin straight, with spinular row at distal corners and fi ne spinular row subdistally on ventral surface. Mandible (Fig. 4A, B). Coxa robust, gnathobase with one pinnate seta at dorsal corner and several blunt multicuspidate teeth along distal margin. Palp biramous; basis strong, with three plumose setae along inner margin, ornamented with a group of long spinules proximally. Exopod 3-segmented, fi rst segment with two plumose setae, sec- ond segment with two bare setae and third segment with two bare setae fused at base. Endopod 1-segmented with two lateral and six distal bare setae (two inner distal setae and two outer distal setae fused at base).
Maxillule (Fig. 4E). Praecoxal arthrite with seven spines around distal margin, with spinules as fi gured; anterior surface with two bare setae; posterior surface with three plumose and one pinnate setae. Coxal endite with two smooth and four plumose setae. Basis with seven bare and one unipinnate setae. Long endopod segment and square exopod segment each with three plumose setae. Endopod and exopod with a row of fi ne marginal setules.  (Fig. 4C). Syncoxa ornamented with spinules as fi gured; with three endites. Proximal endite with one plumose and three unipinnate setae; middle endite with three unipinnate setae; distal endite with two unipinnate and one plumose setae. Allobasis drawn out into pinnate claw; accessory armature consisting of two bare setae and one curved spine. Endopod 2-segmented; proximal segment with one bare seta, distal segment with one geniculate and two bare setae. Maxilliped (Fig. 4F). Subchelate and ornamented with spinular rows as fi gured. Syncoxa with three inner bare setae subdistally. Basis with two bare setae along inner margin. Endopod with one small accessory seta, one bare and two plumose setae.  (Fig. 5A). Intercoxal sclerite rectangular and smooth. Small praecoxa triangular and bare. Coxa with complex spinular ornamentation anteriorly as fi gured. Basis narrower than coxa; anterior surface with pore near the base of outer bipinnate spine; inner side with long slender spinules. Exopod 3-segmented, segments with spinular rows along inner and outer margins. Endopod 2-segmented; enp-1 reaching almost middle of exp-3, with spinular row along inner and outer margins; long inner seta plumose and located subdistally; enp-2 slightly shorter than enp-1, with spinules along inner and outer margins and with two long articulated setae and one small inner apical seta. P2-P4 (Fig. 5B-D). Intercoxal sclerite unornamented. Coxa and basis with complex spinular ornamentation as fi gured. Exopod 3-segmented. Endopod 2-segmented. Endopodal and exopodal segments with spinular rows along inner and outer margins. Exp-1 of P2-P3 without spinules along inner margin. Enp-1 of P2 without inner seta. Terminal outer seta of P2 enp-2 bare. P4 exp-2 with one plumose inner seta. With a pore on anterior surface of enp-2 and anterior surface of exp-2 and -3. Exp-1 and -2 (and -3 in P4) with a posterior spinule patches. Enp-2 with a posterior spinular row subdistally.
Armature formula of swimming legs:  (Fig. 3C). Baseoendopod and exopod covered with fi ne spinules on anterior surface, with long slender spinules along inner and outer margins. Exopod 3.6 times longer than wide, with 6 setae; seta 1 longest and plumose; seta 3 smallest and bare. Baseoendopod longer than wide; with 2 unipinnate and 3 plumose setae. P6 ( Fig. 2A) represented by a small segment with one outer plumose seta and two slender bare setae.
P5 biramous (Fig. 6B), fused medially. Baseoendopod ornamented with patch of spinules as fi gured; with two pores (one near the base of outer basal seta and the other near the base of inner terminal spine of endopodal lobe); endopodal lobe with one lateral and two distal spines. Exopod with three outer bare setae, 1 terminal bare seta and two inner unipinnate setae; with two pores (one tube pore near the base of outer proximal bare seta and the other near the base of outer median bare seta). P6 vestiges asymmetrical (Fig. 2B); each P6 with one plumose inner seta and two long bare setae.
Etymology . Th e specifi c name refers to "korykos" which is the historical name of Kızkalesi province (Mersin, TURKEY).

Discussion
Th e new species can be attributable to the genus Odaginiceps by the absence of inner seta on the proximal segments of P2-P4 exopod and P2 endopod, the short second antennulary segment, the large prominent rostrum, the presence of pinnate setae on the second and third antennulary segments, and the two-segmented P1 endopod with three armature elements on the second segment (Fiers 1995;Fiers and De Troch 2000). Th us far, four species have been assigned to the genus Odaginiceps: O. clarkae, O. xamaneki, O. elegantissima and O. immanis. Th e new species can easily be distinguished from its congeners by the presence of four setae/spines on the second endopodal segment of P4, by the shape of the caudal rami and by the occurrence of four setae on the proximal endite of maxilla. Th e new species is most closely related to the O. xamaneki. Both species diff er from the 3 other congenerics by the presence of short, and compact caudal rami (long and semi-cylindrical in the other species) and the spinular posterodorsal ornamentation of the urosomites (spinular rows present only ventrally in the 3 other species). O. korykosensis sp. n. (female) diff ers from O. xamaneki by the presence of spinules (interrupted midway) along the posterioventral margin of genital double-somite, by the absence of a central spinular patch on ventral surface of second abdominal somite, by the longer outermost seta of P5 baseoendopod, by the much longer terminal plumose setae of P2-P3 enp-2, by the longer P3 enp-2, as well as other minor diff erences observed on the spinular ornamentations of various appendages. Fiers (1995) assumed that the presence of an inner pectinate element on the P3 enp-1, the presence of an inner seta on P4 exp-2, and the distinctly shorter caudal rami in both sexes could be suffi cient grounds to erect a new genus to accommodate O. xamaneki. Th e above mentioned potential generic characters for O. xamaneki are also observed in O. korykosensis which supports the previously formulated assumption. However, until the specifi c and generic importance of these characteristics are better understood and evaluated, both species are retained in the genus Odaginiceps.
Th e new species lacks a seta (arrowed in the Fig. 5D) on the third exopodal segment of the P4 in the male. Th e absence of this seta in the male supports the assumption of Fiers (1995) that almost all tetragonicipitid males bear one seta less on the third exopodal segment of the P4.
Note on the ecology and distribution. Examination of the extensive interstitial samples taken from almost all sandy beaches along the Turkish coasts revealed that the new species occurs at the type locality only. On the other hand three samples taken from the type locality in diff erent seasons revealed no true interstitial forms. Th e absence of true interstitial forms but the presence of O. korykosensis sp. n. in the type locality can be explained by the very low oxygen levels measured at the type locality (Table 1). Most harpacticoids are sensitive to reduced oxygen supply, which restricts their occurrence to the upper sediment layers and favours epibenthic life. It can be discerned from the general body shape of Odaginiceps spp. (see Fig. 1A , B;Fiers 1995;Fiers and De Troch 2000) that they are not truly interstitial, but are probably epibenthic forms crawling on/in the upper surface of sediment along the shallow/deeper waters, meaning that two specimens of O. korykosensis sp. n. accidentally entered into the interstitial sample. Th e eff ect of the oxygen supply on the horizontal composition of harpacticoid species in the sediment can be supported by the presence of several interstitial forms (such as Arenosetella Wilson, 1932) found in 95 % of stations sampled along the Mediterranean coast of Turkey (unpublished data). Th e oxygen levels in the sediments in these localities were much higher than those observed at the locality of Odaginiceps korykosensis sp. n.