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A Parabathynellid Crustacean - Montanabathynella salish


Global Rank: GNR
State Rank: SNR

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General Description
[From Camacho et al. 2009] Genus Montanabathynella: Antennule with 7 segments and terminal aesthetascs on segments 5-7; antenna with 6 segments, segment 4 without setae. Mandible with protruding pars molaris. Maxillule proximal endite with 4 teeth, distal endite with 9 teeth. Exopods of thoracopods (Th) 1-7 with 3-6 segments; epipod absent on Th1-Th3; segments 1-2 of endopods of Th1-Th7 with plumose dorsal seta. Male Th8: very large, twice as long as wide; small endopod with 2 setae; exopod longer than endopod, longer than wide and recurved anteriorly; trapezoidal basipod with terminal seta; basal region of penial complex supports 4 lobes (inner, outer, dentate, small); rounded inner lobe completely integrated into basal region; small lobe in closest contact with (but independent of) inner lobe, with small dorsal teeth; outer lobe twice as long as wide and covered at the end of the small lobe; dentate lobe smaller than inner lobe. Female Th8 very large, with 2 segments: segment 2 with 3 long terminal setae. No pleopods. Sympod of uropod with subequal spines, the distal spine twice as long as others; endopod with 4 spines and 1 spinous process and 3 apical setae; exopod with 12 setae.

M. salish: Total length of males 2.44-3.01 mm, total length of females 2.44-2.80 mm. Body elongated, segments slightly widening towards posterior end. Length of head greater than width. See above description of genus (which is monotypic) and Camacho et al. (2009) for details of other body regions.

Phenology
Not described. Adults of both sexes present in August (Camacho et al. 2009), and probably present throughout the year. Juveniles possibly present in February, May, and August (not clear from description in Camacho et al. 2009).

Diagnostic Characteristics
The only species in the family Parabathynellidae with 9 claws on distal endite of maxillule I and 2 well-developed segments in the female thoracopod 8 (the distal segment with 3 long barbed setae). Combination of characters of genus unique: antennule 7-segmented; antenna 6 segmented; labrum with 18 teeth (12 main, 3 lateral at either end); mandible of pars incisiva of 6 teeth and pars molaris of 7 teeth; exopod of thoracopods with 3-6 segments; pleopods absent; endopod of male Th 8 with 2 setae, exopod without setae, 4 lobes in basal penial region; 15 spines on sympod, 5 spines on endopod with distal two spines similar to a forceps-like structure, 12 setae on exopod of uropod.

Range Comments
Montana endemic; reported from 3 wells at two localities in the Flathead River system, Flathead and Lake counties (Camacho et al. 2009), at about 775 m elevation. Well depths not reported.

Migration
Not described. Likely moves through hyporheic groundwater system.

Habitat
Hyporheic groundwater aquifers and water wells in alluvial flood plains, interstitial (Camacho et al. 2009).

Food Habits
Not described.

Reproductive Characteristics
Not described.

References
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Citation for data on this website:
A Parabathynellid Crustacean — Montanabathynella salish.  Montana Field Guide.  .  Retrieved on , from