Itunella arenaria, Lee & Chang, 2008
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publication ID |
https://doi.org/ 10.1080/00222930802130302 |
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persistent identifier |
https://treatment.plazi.org/id/03FD3942-FFE5-B411-9705-FB93FC0F9A65 |
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treatment provided by |
Felipe |
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scientific name |
Itunella arenaria |
| status |
sp. nov. |
Itunella arenaria sp. nov.
( Figures 2–6 View Figure 2 View Figure 3 View Figure 4 View Figure 5 View Figure 6 )
Type material
Holotype ♀ (DB20014), allotype „ (DB20015), dissected in lactophenol, estuary of Daejongcheon Stream, Gyeongju (35 ° 449370N, 129 ° 299020E), 15 May 1996 (leg. C.Y. Chang and H.S. Rho). Paratypes: three ♀♀, two „„, collection details same as in holotype, including three undissected (♀, NHM reg. no. 2008. 960; „, NHM reg. no. 2008. 961; ♀, NIBRIV0000100514) and two dissected paratypes (♀, DB20016; „, DB20017).
Additional material examined
Two ♀♀, Wolpo Beach (estuary of Seojeongricheon Stream), Pohang, 3 February 2007 (C.Y. Chang, J.M. Lee and S.W. Lee) ; eight ♀♀, five „„, coastal well at Balsanri village , Youngil Bay, Pohang, 29 April 2007 (C.Y. Chang, J.M. Lee and H.J. Yoon) ; three ♀♀, estuary of Daejongcheon Stream , Gyeongju, 15 May 1996 (C.Y. Chang and H.S. Rho) .
Description
Female. Body ( Figure 2A View Figure 2 ) slender, elongate, 460¡30 Mm (n 59) in length, cylindrical, tapering posteriorly from genital double-somite, without clear distinction between prosome and urosome. All prosomites and urosomites except cephalosome and anal somite ornamented with hyaline frill. Distolateral margin of each prosomite a little protruded. Rostrum protruding with round apex, bearing two sensillae, defined at base. Cephalothorax bell-shaped, a little shorter than sum of next three prosomites; numerous integumental pores dispersed throughout whole surface, with eight or nine short hairs scattered, as in Figure 2A View Figure 2 ; four to six papillary sensillae along posterior margin; integumental depression (nuchal organ) not clear. Genital double-somite completely fused, with subcuticular ridge only laterally marking line of fusion. Genital apparatus comprising genital apertures medially fused to form a large elliptical gonopore ( Figure 6B View Figure 6 ); median copulatory pore close to gonopore, partly covered with paired oblique opercula. Anal somite a little longer than preceding abdominal somites; anal operculum not convex, its posterior margin rather straight, serrated; both posterolateral sides of anal somite protruded as triangular projections, serrated longitudinally ( Figures 2B,C View Figure 2 and 5B View Figure 5 , arrows).
Caudal rami ellipsoidal in dorsal view, 1.65–1.86 times (mean 1.76, n 59) longer than wide, a little divergent posteriorly. Dorsal keel apparent, running longitudinally nearly throughout dorsal surface. One oblique spinule row present dorsomedially; spinules patched at distal part of dorsal face ( Figure 2B,C View Figure 2 ); two oblique spinule rows laterally ( Figure 2C View Figure 2 ). Lateral caudal setae (caudal setae I and II) locating near proximal quarter of lateral margin; caudal setae II vestigial. Outer caudal seta (caudal seta III) slender, situated at proximal third of lateral margin of caudal rami. Outer terminal caudal seta (caudal seta IV) short, plumose, a little shorter than inner caudal seta (caudal seta VI). Inner terminal caudal seta (caudal seta V) bare, a little more than three times as long as caudal rami. Inner caudal seta (caudal seta VI) swollen at its base, with secondary setules inwardly. Dorsal caudal seta (caudal seta VII) situated a little posterior to middle of caudal ramus, between dorsal keel and medial spinule row.
A1 ( Figure 2D View Figure 2 ) seven-segmented; segment 1 armed with spinules proximally and distally; segment 2 slightly swollen, with convex anterior margin; segment 4 bearing one long aesthetasc, its tip nearly reaching to the end of last segment; last segment with one aesthetasc apically. Setal formula: 1-[1 pinnate], 2-[7], 3-[5], 4-[2+aesthetasc], 5-[1], 6-[2], 7-[6+(2+aesthetasc)]. A2 ( Figure 3A View Figure 3 ), allobasis bearing one naked seta proximally, with one spinule row near middle of medial margin; endopod bearing three outer or outer distal spines, four terminal geniculate setae and one small inner distal seta; exopod one-segmented, about 2.5–3 times longer than broad, with four setae in total. Mandible ( Figure 3B View Figure 3 ) with well-developed coxal gnathobase bearing six teeth along distal margin and one seta at dorsal corner; palp onesegmented with both rami fused to basis, tapering distally, armed with four setae in total and one setule row inner distally. Maxillule ( Figure 3C View Figure 3 ) with praecoxal arthrite bearing seven elements with two setae on frontal surface and one plumose seta posteriorly; coxal endite cylindrical, bearing one large spine with both margins serrated distally and one plumose seta proximally; exopod and endopod fused to basis, bearing in total six setae and one apical spine with two accessory setae at its distal third. Maxilla ( Figure 3D View Figure 3 ) armed with two syncoxal endites, each endite bearing three setal elements; allobasis forming one strong pectinate claw, flanked by two setae; endopod represented by small protuberance bearing two long setae. Maxilliped ( Figure 3E View Figure 3 ) subchelate; syncoxa protruded distomedially with one pinnate seta; basis pectinate with 10–12 spinules along inner margin; endopod represented by one strong and curved claw, bearing two minute setae proximally as accessory armature.
P1 ( Figure 4A View Figure 4 ), exopod three-segmented; endopod two-segmented; endopod much shorter than exopod; coxa armed with one row of sharp spinules at outer distal corner, with one row of minute spinules medially; basis with one spiniform seta inner distally, its tip reaching to two-thirds of enp 1; enp 1 a little elongate, without inner seta; enp 2 with one plumose inner seta and two long terminally pinnate setae apically; exp 1 without inner seta; exp 2 with one short inner proximal seta; exp 3 with one outer spine and three long terminally pinnate setae. P2–P4 ( Figure 4B–D View Figure 4 ), exopods three-segmented; endopods one-segmented; enp 1 small, bearing one spine and two setae, with spinules along lateral margin; exp 1 and exp 2 ornamented with two to four spinule rows near lateral margin of posterior face. Seta/spine armature of P1–P4 as follows (Arabic numerals representing setae, while Roman numerals indicating spines):
P1 basis I-I exp I-0; I-1; I,1,2 enp 0-0; 0,1,2
P2 basis 1-0 exp I-0; I-1; II,1,2 enp I,1,1
P3 basis 1-0 exp I-0; I-1; II,1,2 enp I,1,1
P4 basis 1-0 exp I-0; I-1; II,1,2 enp I,1,1
P5 ( Figure 2E View Figure 2 ) baseoendopod not protruded, bearing four spiniform setae; exopod nearly as long as wide, bearing two stout apical and three slender outer setae, with spinules inner distally.
Male. Body 378¡20 Mm (n 55) in length. Sexual dimorphism shown in caudal ramus, A1, endopods of P2–P4, P5 and P6. Caudal rami ( Figure 2F View Figure 2 ) spindle-shaped; relatively a little longer than in female, 2.1 times as long as wide; lacking spinule patch posterior to dorsal caudal seta.
A1 ( Figure 3F,G View Figure 3 ) subchirocerate, eight-segmented; geniculate between segments 6 and 7; segment 1 with one row of spinules and one pinnate seta; segment 2 with nine setae (eight naked and one plumose); segment 3 incompletely fused, with two or three surface sutures dorsally, bearing seven naked setae; segment 4 bulbous ventrally, with seven naked setae and one long aesthetasc; segment 5 narrow, with three pinnate and one naked setae; segment 6 enlarged, with one row of denticles on dorsal surface, bearing one pinnate and one naked setae; segment 7 elongate, with one naked seta and two rows of denticles on dorsal surface; last segment projected apically, with six bare setae and one distal trithek.
P2 endopod ( Figure 4E View Figure 4 ) one-segmented, bearing three plumose setae inner distally with spinule row at outer distal margin. P3 endopod ( Figure 4F View Figure 4 ) twosegmented; enp 1 lacking seta or spine; enp 2 elongate, outer distal margin attenuated into slender apophysis with its posterior margin minutely serrate, armed with one proximal and two distal setae. P4 endopod ( Figure 4G View Figure 4 ) three-segmented; enp 1 without inner seta; enp 2 with one plumose seta and three tooth-like projections; enp 3 conical, with one long seta apically.
P5 ( Figures 4H View Figure 4 , 6D View Figure 6 ) baseoendopod bearing two setae, similar in lengths to each other; exopod with six setae in total, including one brush-like innermost seta ( Figure 6D View Figure 6 , left arrow). P6 represented by single seta on outer distal corner of genital operculum ( Figures 4H View Figure 4 , arrow; 6D, right arrow), with basal socket.
Variability
Individuals from the coastal wells in three localities in South Korea show some variation in two characters. Specimens from the type locality, estuary of Daejongcheon Stream, have the anal operculum with its posterior margin densely serrated (bearing more than 30 teeth), while the specimens from the coastal wells have the anal operculum with 18–20 sharp, triangular teeth, sometimes shown as spinules. Furthermore, in the individuals from the coastal wells, the spinule patch at the outer distal part of the dorsal face of the caudal ramus (cf. Figure 2B View Figure 2 ) is very weak or rather lacking as in male specimens (cf. Figure 2F View Figure 2 ). Other characters, including seta/spine armature of legs, are consistent throughout all the specimens examined. As the coastal well is exposed, and not deep (less than 1.5 m deep) there are no grounds for the specimens to be regarded as genuinely subterranean, with taxonomically significant diversification .
Etymology
The specific name ( arenaria, Latin ) means ‘of sand’ or ‘sandy’, taken from the main habitat (sand dunes of the estuaries), where the new species occurred.
Ecology
Collected from the sand dunes of the estuaries discharging into the southeastern coast of Korea and from a coastal well. This species is supposed to be a meiobenthic one inhabiting coarse to medium sand sediments around the estuary. It co-occurred with Ameira parvula (Claus, 1866) , Nitokra koreanus Chang, 2007 , and a tardigrade species, Pseudobiotus granditintinus (Chang and Rho, 1996) .
Remarks
In the genus Itunella Brady , five species have been recorded so far: I. tenuiremis (Scott, 1893) , I. subsalsa Brady, 1896 , I. muelleri (Gagern, 1922) , I. bacescui (Chappuis and Serban, 1953) , and I. intermedia Apostolov, 1975 . All of them were known from Europe. Among them, I. subsalsa was a junior synonym of I. tenuiremis , and I. bacescui was a junior synonym of I. muelleri , ( Dussart and Defaye 1990; Bodin 1997). Therefore, only three species are currently recognized as valid.
Itunella arenaria n. sp. is characterized by the serrated projections beside the anal operculum with its convex posterior margin serrated as well as some different modification tendencies in the male endopodal armature. Based on the ellipsoidal shape of the caudal ramus in the female, as used in the key by Lang (1948), I. arenaria sp. nov. most resembles I. muelleri . However, I. arenaria differs from it by spine/seta armature on P4 and P 5 in the male: the apical element on P4 enp 3 is a long seta in I. arenaria , but a stout, dagger-like projection in I. muelleri ; and the P5 exopod is armed with six setae including a brush-like innermost seta in I. arenaria , while all the setae are normal in I. muelleri .
Itunella arenaria sp. nov. is also similar to I. intermedia in the appearance of the caudal ramus; however, I. arenaria is clearly distinguished from I. intermedia by the armature of the endopods of male P2–P4, and by the number and shape of the setae on P5 exopod:
(1) P2 endopod bearing three setae in I. arenaria compared with four in I. intermedia ;
(2) P3 enp 2 bearing three setae in I. arenaria compared with only one in I. intermedia ;
(3) P4 endopod three-segmented with two setae and three projections in I. arenaria compared with one-segmented with two setae and serrated apical projection in I. intermedia (cf. Apostolov 1975, Figure 4j View Figure 4 );
(4) P5 exopod bearing six setae including a brush-like innermost seta in I. arenaria , while there are five normal setae in I. intermedia .
Finally, I. arenaria is easily distinguished from I. tenuiremis by the conspicuous anal operculum (compared with an inconspicuous or even absent anal operculum in I. tenuiremis ), ellipsoidal caudal ramus in female (against rather oblong ramus in I. tenuiremis ), and different armature of P2–P4 endopods in the male.
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