Keysercythere reticulata, Tanaka & Yoo & Pham & Karanovic, 2021

Tanaka, Hayato, Yoo, Hyunsu, Pham, Huyen Thi Minh & Karanovic, Ivana, 2021, Two new xylophile cytheroid ostracods (Crustacea) from Kuril-Kamchatka Trench, with remarks on the systematics and phylogeny of the family Keysercytheridae, Limnocytheridae, and Paradoxostomatidae, Arthropod Systematics & amp; Phylogeny 79, pp. 171-188 : 171

publication ID	https://dx.doi.org/10.3897/asp.79.e62282
publication LSID	lsid:zoobank.org:pub:E29CD94D-AF08-45D2-A319-674F8282D7F2
persistent identifier	https://treatment.plazi.org/id/D8A5E8AE-C17D-4A2F-B762-F51E3CBFCA70
taxon LSID	lsid:zoobank.org:act:D8A5E8AE-C17D-4A2F-B762-F51E3CBFCA70
treatment provided by	Arthropod Systematics & Phylogeny by Pensoft
scientific name	Keysercythere reticulata
status	sp. nov.

Treatment

Keysercythere reticulata View in CoL sp. nov. Figs 3 View Figure 3 , 4 View Figure 4 , 5 View Figure 5 , 6 View Figure 6 , 7 View Figure 7

Material examined.

Holotype: adult male ( SMF 57053 View Materials ), RV L 0.38 mm, H 0.18 mm; LV L 0.38 mm, H 0.16 mm; dissected, soft parts mounted on two glass slide and valves on cardboard cell slide . Paratypes: 1 adult female ( SMF 57054 View Materials ); dissected, soft parts mounted on a glass slide and valves on a cardboard cell slide : 1 juvenile ( SMF 57055 View Materials ) in 80% ethanol .

Type locality.

Kuril-Kamchatka Trench region, the sampling station SO250_9 of KuramBio II expedition (RV Sonne, 250th Expedition), trawled from 43°48.43'N, 151°44.35'E, 5134 m to 43°47.64'N 151°44.51'E, 5101 m by AGT on 19th August, 2016.

Diagnosis.

Shell trapezoidal in lateral view, with inflated medial portion of the shell. L around 0.38 mm. External surface of carapace reticulated characterized by polygonal muri and pitted secondary reticulation within the fossae. Sensilla long existing non-collar pores surrounded with distorted shaped sieve pores (Type C pore; see review by Danielopol et al. 2018). Hp: ejaculatory duct coiled many times; hook-like process rectangular shape with round corners and a concave along distal margin; distal lobe broad sub-triangular shape.

Description of adult male

(based on holotype SMF 57053). Carapace (Figs 3 View Figure 3 , 4A-D, G View Figure 4 ) trapezoidal in lateral view, with inflated medial portion of the shell (Fig. 3 View Figure 3 ). L around 0.38 mm. Greatest H situated behind middle L, equaling 35% of total L. Dorsal margin somewhat roughly rounded, dorso-anterior margin converge rapidly anteriorly to a pointed tip located near the ventral margin, ventro-anterior margin relatively gently converge comparing with dorso-anterior margin, ventral margin concave immediately situated in front of middle L. Posterior margin slightly broader than anterior margin. Both valves bearing one protrusion on posterior end. External surface reticulated characterized by polygonal muri and pitted secondary reticulation within the fossae (Fig. 4A, D, G View Figure 4 ). Sensilla long existing non-collar pores surrounded with distorted shaped sieve pores (Fig. 4G View Figure 4 ); sieve pores clearly arranged in clusters, visible as pockmarks on the inside of the shell; approximate length major axis 6-30 μm and minor axis 6-12 μm (Fig. 4B, D View Figure 4 ). Some simple pores (Type A sensu Puri and Dickau, 1969) existing on rim (Fig. 4H View Figure 4 ). Inner calcified lamella broadly developed anteriorly and posteriorly in both valves (Fig. 3 View Figure 3 ). Four adductor muscle scars form a vertical row (Fig. 3 View Figure 3 ). Hingement merodont: LV carrying dents in medial element, posterior element with several sockets, anterior element with several shallow sockets (Fig. 4D View Figure 4 ); RV with corresponding grooves in medial element, anterior and posterior elements elongated knob with shallow dents (Fig. 4B View Figure 4 ). A1 (Fig. 5A View Figure 5 ) six podomeres [four and five podomeres divided by suture, same as defined 4a and 4b by Smith and Tsukagoshi (2005) and Boxshall et al. (2010)]. First podomere bare. Second podomere 1.5 times as long as first podomere, with one lateral distal seta. Third podomere one-third as long as first podomere, with one long antero-distal seta. Fourth to sixth podomeres same length as third podomere. Fourth podomere with one long antero-distal seta and one long lateral distal seta. Fifth podomere with three long antero-distal setae and one long postero-distal seta. Sixth podomere with two long distal setae and one long blunt tipped distal seta. A2 (Fig. 5B View Figure 5 ) five articulated podomeres. First podomere (basis) parallelogram-shaped, with setulae on antero-distal margin and one long six-annulated exopodite (spinneret seta) on antero-distal end. Second (first endopodal) podomere four-fifths as long as first podomere, with one short postero-distal spine. Third (second endopodal) podomere two-thirds as long as first podomere, with one short antero-distal seta. Fourth (third endopodal) podomere four-fifths as long as first podomere, with one stout postero-distal claw with curved tip and a row of setulae on posterior margin. Fifth (fourth endopodal) podomere small, with one stout distal claw with a row of setulae on postero-distal margin. Md (Fig. 5C, D View Figure 5 ) coxa with one dorsal seta. Coxal endite consisting of eight teeth. Palp consisting of four podomeres. First podomere (basis) with one finger-like shaped sheet (exopodite) near proximal end, one short seta on dorsal margin, two short setae on ventral margin, and four long setulous setae on ventral side of distal margin. Second podomere with one setulous ventro-distal seta, one simple and setulous dorso-distal setae. Third podomere with one stout lateral distal claw. Fourth podomere with one broad and one slender distal claws each curved distally and with a row of setae on ventral margin. Mxl (Fig. 5F View Figure 5 ) branchial plate (exopodite) with 11 plumose setae. Basal podomere with one palp (lost) and three endites. Endites: dorsal one with four simple distal setae; middle one with three simple distal setae; ventral one with three simple distal setae and one setulous distal seta. L5 (Fig. 6A View Figure 6 ) four articulated podomeres. First podomere with two plumose antero-lateral setae, one plumose antero-distal seta, and one plumose dorso-proximal seta. Second podomere half as long as first podomere, with one plumose antero-distal seta. Third podomere one-third as long as first podomere, bare. Fourth podomere half as long as first podomere, with one stout sclerotized distal claw with a few sharp spines on antero-distal margin. L6 (Fig. 6B View Figure 6 ) four articulated podomeres. First podomere with one plumose antero-lateral seta, one plumose antero-distal seta, and one plumose dorso-proximal seta. Second podomere half as long as first podomere, with one long simple antero-distal seta. Third podomere one-fourth as long as first podomere, bare. Fourth podomere three-eighths as long as first podomere, with one stout sclerotized distal claw with a few sharp spines on antero-distal margin. L7 (Fig. 6C View Figure 6 ) four articulated podomeres. First podomere with two simple antero-lateral setae and one plumose antero-distal seta. Second podomere three-fourths as long as first podomere, with one plumose antero-distal seta. Third podomere one-fourth as long as first podomere with a row of setulae on distal margin. Fourth podomere half as long as first podomere, with one stout sclerotized distal claw with a few sharp spines on antero-distal margin. Brush-shaped organ absent. Hp and posterior body (Fig. 6E, F View Figure 6 ) symmetrical. Ejaculatory duct coiled many times. Hook-like process rectangular shape with round corners and a concave along distal margin. Distal lobe broad sub-triangular shape. Posterior body left and right sides bearing two setulous furcal setae.

Description of adult female

(based on paratype SMF 57054). Carapace (Fig. 4E, F, H View Figure 4 ) trapezoidal in lateral view, with inflated medial portion of the shell. LV, L 0.43 mm, H 0.17 mm. Dorsal and ventral margins almost flat. Both valves bearing one protrusion on posterior end. Muri of surface reticulation thicker than that of male. Mxl (Fig. 5E View Figure 5 ) branchial plate (exopodite) with 13 plumose setae. Basal podomere with one palp (endopodite) and three endites. Palp consisting of one podomere, with three simple distal setae. Endites: dorsal one with four simple distal setae; middle one with four simple distal setae; ventral one with three simple distal setae and one setulous distal seta. L5 (Fig. 6D View Figure 6 ) small difference against male’s L5: one plumose antero-distal seta shorter rather than that of male. Copulatory organ and posterior body (Fig. 6G View Figure 6 ) female genital opening paired. Sclerotized framework of genital opening roughly circular. Spermathecal duct long connecting with genital opening. Genital lobe paired with each two setulous furcal setae.

Etymology.

Named after reticulated surface ornamentation of the carapace.

Distribution.

Only recorded from the type locality.

Remarks.

Keysercythere reticulata can be easily distinguished from the only other species of the genus, Keysercythere enricoi , by the carapace surface ornamentation: the former has a strongly reticulated, while the latter has smooth surface. Ventral margin of valves is concave in the new species versus convex in K. enricoi . The morphology of Hp is also different: the hook-like process is rectangular and the distal lobe is broad sub-triangular in the new species, while the hook-like process is semi-circular and the distal lobe is acute sub-triangular with sharply bended tip in K. enricoi .