A Parabathynellid Crustacean - Pacificabathynella ruthae
[From Camacho et al. 2009; Camacho et al. 2016] Genus Pacificabathynella: Male body length 0.53-2.07 mm, female body length 0.51-1.78 mm; antennule with 7 segments, antenna with 7-8 segments; mandible with 2 teeth on incisor process (pars incisiva), pars molaris with 2 bidentated structures; labrum with a small central protuberance at distal edge; epipod of thoracopod I absent, epipod of thoracopod II absent or present; exopod of thoracopods I-VII with 5-6 setae; thoracopods VI and VIII sexually dimorphic. Thoracopod VI of male with 3-segmented endopod, thoracopod VIII of male with 3 lobes around genital opening, basipod prominence present, exopod 1-segmented, endopod 1-segmented; thoracopod VI of female with 4-segmented endopod, thoracopod VIII of female with 1-2 plumose setae on coxa, 1-2 setae on basipod, epipod is present, exopod and endopod 1-segmented, 2 apical setae on exopod, 1-2 apical setae on endopod; sympod of uropod with 6-8 spines, endopod of uropod with 4-8 strong spines along inner margin; furcal rami with 5 spines.
P. ruthae: Male body length 1.57-2.07 mm, female body length 1.45-1.78 mm; body form not very elongated, almost cylindrical, approximately 13 times long as wide; pleotelson with 1 barbed dorsal seta on either side, and shorter than furcal rami. Antennule and antenna of similar length, each with 7 segments; epipod of thoracopods I-II absent, exopod of thoracopods I-VII with 6 setae; female thoracopod VIII with 1 plumose seta on coxa, 1 smooth seta on basipod, 2 smooth setae on exopod and endopod; male thoracopod VIII with 2 setae on basipod, 1 seta on endopod, crest of basipod pronounced; 1/7 setae on pleopod; endopod of uropod with 6 spines, exopod of uropod with 9 setae; first spines on furca 1.5 times longer than second and 2 times longer than dorsal spines, size of first spines>dorsal spines>second spines=third spines>fourth spines.
Not described. Adult males and females collected in February and November (Camacho et al. 2009; Camacho et al. 2016). Adults probably active throughout the year.
The only species of the genus where the antennule and antenna are of similar length; female thoracopod VIII with the smallest epipod in genus; endopod of uropod with 6 spines (not 4, 5, or 8), exopod of uropod with 9 setae (not 7 or 8).
Montana endemic: reported from one locality (five wells) on the Nyack floodplain (Nyack Aquifer) in Flathead County (Camacho et al. 2009), at about 1030 m elevation. Specific well depths not reported but largely between 1 and 12 m.
Not described. Likely moves through hyporheic groundwater system.
Hyporheic groundwater aquifers and water wells in alluvial flood plains, interstitial (Camacho et al. 2009).
- Literature Cited AboveLegend: View Online Publication
- Camacho, A.I., R.L. Newell and B. Reid. 2009. New records of Bathynellacea (Syncarida, Bathynellidae) in North American: three new species of the genus Pacificabathynella from Montana, USA. Journal of Natural History. 43:29, 1805-1834.
- Camacho, A.I., R.L. Newell, Z. Crete, B.A. Dorda, A. Casado, and I Rey. 2016. Northernmost discovery of Bathynellacea (Syncarida: bathynellidae) with description of a new species of Pacificabathynella from Alaska (USA). Journal of Natural History 50:583-602.
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