Comprehensive Description

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Description

 Carapace (Fig. 1G–I). Small sized (length = 657–685 μm), with brown surface and sparse setae; surface smooth except for a subtle ventro-lateral ridge on each valve; elliptically elongated in lateral view (length/height=1.96), with greatest height just behind the mid-length; left valve overlapping right valve on all margins, strongly interlocking in antero-ventral, ventral and postero-ventral margins; ventral area flat; dorsal margin arched; posterior and anterior margins rounded, both produced towards the ventral side; oval shaped in ventral and dorsal views, with maximum width behind mid-length; dorsal margin straight in dorsal view; ventral margin sinuous in ventral view with well-marked ridges.   Left valve (Fig. 1A–C). In internal view, anterior and posterior margins rounded, produced towards the ventral side; ventral margin nearly straight; dorsal margin arched; calcified inner lamella well developed anteriorly, with a short line of concrescence near the valve margin leaving a vestibule; vestibule less developed posteriorly, but present; prominent selvage running on all margins except in the middle of dorsal margin; a short flange is formed at the antero-ventral margin; central muscle scars consisting of 4 spots arranged in a vertical row relatively separated from each other and a round small frontal scar.   Right valve (Fig. 1D–F). In internal view, anterior and posterior margins rounded, produced towards the ventral side; ventral margin nearly straight; dorsal margin arched; calcified inner lamella well developed anteriorly, with a short line of concrescence near the valve margin leaving a vestibule; vestibule less developed posteriorly but present; prominent selvage running all around, forming the hinge structures on the dorsal margin; a continuous flange is present, being wide on the antero-ventral margin, very narrow at the mouth region and narrow on the ventral and postero-ventral margins; central muscle scars consisting of 4 spots relatively separated from each other arranged in a vertical row and a round small frontal scar.   Hinge (Fig. 1A–F). A long (c. 3/4 of the valve length) cardinal ridge is present on the right valve, forming at each end, respectively, a small anterior tooth and a large posterior tooth; the ridge is slightly crenulated, especially at the posterior end; RV with complimentary groove and sockets.   Pigmented naupliar eye present; carapace less pigmented at the eye region.  Antennula (Fig. 2A). 5 functional articles; first article relatively large, bearing on the dorsal margin a sub-apical expansion with a tuft of tiny setules; second article the longest with a ventro-proximal long and thick seta; third article small with a short dorso-apical seta; fourth article partially subdivided in two, medially (where the segment is subdivided) with two dorsal and one ventral setae, and apically with a long ventro-apical, two short and one long dorso-apical setae; fifth (terminal) article with two long setae, one short seta and a short aesthetasc (Ya).   Antenna (Fig. 2B). Protopodite 2-segmented, the first one very short and the second one long, wide and curved; endopodite 3-articulated; first segment relatively short, bearing a long ventro-apical seta; second segment very long and narrow, dorsally with two sub-apical setae, one three thirds as long as the other, ventro-medially with a short seta and an aesthetasc (Y), and apically with two setae, one large and one minute; last segment small, with three claws, the ventral one strongly serrated and the other two slender, a minute seta and a tiny lobe (hyaline formation); exopodite with a very small seta and a spinneret seta.   Mandible (Fig. 2D–E). Coxa with 7 strong teeth and 6 setae on inner edge and a seta on outer edge (near the articulation with the palp); palp 4-segmented (basis + 3-segmented endopodite); basis externally with respiratory plate (exopodite) consisting of 3 rays and one reflexed seta, and internally with two setae, one two thirds as long as the other; first endopodal segment with two apical internal setae, one less than half as long as the other; second endopodal segment with an internal apical seta and 4 external apical setae, one short, two long and one intermediate; terminal endopodal segment with 2 setae and one slender claw, all equally long.   Maxillula (Fig. 2F). Internally with three endites, first one with 2 setae, second and third ones each with 3 setae and two claws, the latter with a conspicuous spoon-shaped apex; palp not segmented, tapering, with 2 apical setae; respiratory plate well developed, carrying a reflexed seta (i.e. reversed towards the front) and 16 long rays.   First thoracopod (Fig. 3A). 4-segmented; first segment with a long medio-proximal dorsal seta, a medium-sized medio-ventral seta and two stout short ventro-apical setae; second segment quite long, with a strong ventro-apical seta; third segment devoid of setae; terminal segment with an apical claw that bears a minute seta at its base.   Second thoracopod (Fig. 3B). 4-segmented; first segment with a long medio-proximal dorsal seta, a medium-sized medio-ventral seta and a relatively short ventro-apical seta; second segment long, with a strong ventro-apical seta reaching tip of following segment; third segment devoid of setae; terminal segment with an apical claw bearing a minute seta at its base.   Third thoracopod (Fig. 3C). 4-segmented, quite slender; first segment with a medio-proximal dorsal seta, a medio-ventral seta and a ventro-apical seta; second segment quite long, with a slender ventro-apical seta; third segment devoid of setae; terminal segment with a very long and slim apical claw carrying a minute seta at its base.   Hemipenis (Fig. 3D). Consisting of a large rounded muscular body, an articulating distal lobe and a dorsal seta; distal lobe triangular, with a pointed tip and with a finger-like projection at the base of the internal margin, next to the dorsal seta; copulatory process a stiff hook-like structure, thick at the first half of its length and then quickly narrowing to the orifice at the tip; lower ramus (“crochet accessoire”) sinuous and with a rounded tip; caudal ramus a hirsute rounded lobe bearing a pair of setae.  Additional description of female.  Carapace (Fig. 4G–I). Small sized (length = 697–722 μm), with brown surface and sparse setae; surface smooth except for a subtle ventro-lateral ridge on each valve; elliptically elongated in lateral view (length/height=1.96), with greatest height just behind mid-length; left valve overlapping right valve on all margins, strongly interlocking in antero-ventral, ventral and postero-ventral margins; valve overlap very strong at the posterior end of the carapace, producing a conspicuous outgrowth of the outer lamella, apparently without substantial change to the inner marginal structures; ventral area flat; dorsal margin arched; posterior and anterior margins rounded, both margins produced towards the ventral side; valves oval shaped in ventral and dorsal views, with maximum width displaced towards the posterior end in comparison to the male, producing a brooding cavity; up to 10 eggs were observed in a brood (mean egg size = 4.87 ± 4.0 μm, N = 8); dorsal margin straight in dorsal view; ventral margin sinuous in ventral view with well-marked ridges.   Left valve (Fig. 4A–C). In internal view anterior margin rounded, produced towards the ventral side; posterior margin narrowly rounded, produced towards the ventral side, forming a bulge at the postero-ventral area; ventral margin nearly straight; dorsal margin arched; calcified inner lamella well developed anteriorly, with a short line of concrescence near the valve margin leaving a vestibule; vestibule less developed posteriorly, but present; prominent selvage running on all margins except in the middle of dorsal margin; a short flange is formed at the antero-ventral margin; at the postero-ventral region, with outer lamella expanded towards the posterior end; central muscle scars consisting of 4 spots arranged in a vertical row relatively separated from each other and a round small frontal scar.   Antenna (Fig. 2C). As in the male, except for the small terminal segment with three equally slender claws, a minute seta and a tiny lobe (hyaline formation).   Abdomen (Fig. 3E). Genital operculum rounded, internally connected by tubes to a trabecula; caudal rami two hirsute rounded lobes, each with two apical setae in juxtaposition, a medio-external seta and an inconspicuous external seta nearer the base of the caudal ramus; end of body rounded, with a dorsal seta inserted in a strongly chitinized structure.  Measurements.  Male. Holotype: length = 674 µm, height = 347 µm; Paratype MZUSP 29077: length = 685 µm, height = 349 µm; Paratype MZUSP 29078: length = 657 µm, width = 463 µm; Paratype MZUSP 29079: length = 677 µm, width = 461 µm. Female. Paratype MZUSP 29076, LV: length = 721 µm, height = 344 µm; Paratype MZUSP 29080: length = 715 µm, height = 355 µm; Paratype MZUSP 29081: length = 697 µm, width = 513 µm; Paratype MZUSP 29082: length = 722 µm, width = 518 µm.

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Creative Commons Attribution 3.0 (CC BY 3.0)

© Ricardo L. Pinto, Merlijn Jocqué

Source: ZooKeys

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