Snails: A freshwater snail (Juga newberryi)

(Gastropoda: Neotaenioglossa: Semisulcospiridae)

Profile prepared by Sarah Foltz Jordan and Julia Janicki, The Xerces Society for Invertebrate Conservation.

Juga newberryi is a species of medium-sized, aquatic, gilled snail with its shell typically exhibiting a color pattern consisting of three yellow bands separated by three almost black bands (Lea 1860, 1862, 1863; Strong and Frest 2007). Occasionally, the lower band may be divided into two or more bands (Burch 1989: fig. 452) or the dark bands may be tan in color (Strong & Frest 2007).  It is a asper-grazers, feeding on both algae and detritus and is found primarily in gravel-boulder riffles and rapids edges in moderately swift current (Frest and Johannes 1995). This large-river species is known only from the Deschutes River where it is found in cold, clear water at depths of 0-16 inches (Frest and Johannes 1995; Deixis MolluscDB 2009). Though J. newberryi was originally distributed in the Deschutes River, Oregon, it is now known only from the lower 90 miles of the Deschutes River drainage where it occurs very sporadically below Pelton Dam, Wasco and Sherman counties.  Increasing recreational usage of the Deschutes Wild and Scenic River is a major concern for J. newberryi (Frest and Johannes 1995).  It occurs only in the most undisturbed portions of the river, and seems to be sensitive to physical disturbance.  Further surveys and management of sites and its associate watersheds are necessary for conserving this particular species.

conservation status
Global Status (2006): G1
State Status: Oregon (SNR-State Not Ranked)
(NatureServe 2009)
description

Adult: Juga is a genus of medium-sized, aquatic, gilled snail traditionally treated as part of the subfamily Semisulcospirinae within the Pleuroceridae family, although the Semisulcospirinae subfamily was recently elevated to family level based on morphological and molecular evidence (Strong & Köhler 2009). The Pleuroceridae and Semisulcospiridae families both differ from the Hydrobiidae family in that the males lack a verge (male copulatory organ). The genus Juga is distinct from related pleurocerid snails based on reproductive anatomy and egg mass characters (Taylor 1966), as well as features of the ovipositor pore, radula, midgut, kidney, and pallial gonoduct (Strong and Frest 2007). Members of this genus have a tall, conic shell-shape and thick, heavy shells which are commonly decollate (early whorls lost). The operculum is present and they are gill breathing and dioecious (separate sexes).

Juga newberryi shells typically exhibit a color pattern consisting of three yellow bands separated by three almost black bands (Lea 1860, 1862, 1863; Strong and Frest 2007). Occasionally, the lower band may be divided into two or more bands (Burch 1989: fig. 452) or the dark bands may be tan in color (Strong & Frest 2007). Alternatively, the shell may be bandless, in which case the color varies from yellowish-tan to dark tan (Strong & Frest 2007). Recent field surveys have not revealed any “pure” populations of the bandless form, although large populations will probably have some bandless individuals (Strong & Frest 2007; Frest, unpublished data).

The external anatomy of J. newberryi is described as follows (Strong and Frest 2007): Operculum ovate, with angular tip; nucleus comprising about one third of total length. Rather shallow ovipositor pore with shallow, grooved tract extending to edge of foot, a slight distance back from the anterior pedal gland. Ctenidium extending from posterior end of mantle cavity to mantle edge. Hypobranchial gland moderately well developed with warty texture, particularly at posterior end of mantle cavity.

The external anatomy of J. newberryi is almost identical to that of J. silicula and J. acutifilosa, differing in that the operculum of J. newberryi is more angular in shape and the nucleus is considerably smaller and more basal than eccentric (Strong and Frest 2007). The hypobranchial gland of J. newberryi is unique in having a warty texture (Strong and Frest 2007). Further anatomical descriptions of this species, including figures of the alimentary, reno-pericardial, nervous, and reproductive systems, are provided in Strong and Frest (2007).

Egg mass: The Juga egg mass generally consists of thick finger-like, elongate, rather weakly coherent gelatinous aggregations, often several cm in length and 2-4 cm in width, with hundreds to thousands of moderately loosely packed, quite small (< 1 mm) eggs, with individual egg boundaries not very apparent, and without regular arrangement of eggs. The fresh egg mass deteriorates roughly a month after deposition, when the embryos begin to acquire shells and hatch (Frest and Johannes 2006). There is no veliger stage.

taxonomic status

Although Juga newberryi was once synonymized with J. bulbosa, a recent review of literature and type material has removed the synonymy, treating them as two separate species (Strong and Frest 2007). Much of the existing literature and records for Juga newberryi (particularly in documents by T. Frest and E. Johannes) is documented under the name of Juga bulbosa (Johannes 2009, pers. comm.). Both species belong to the Oreobasis subgenus, a small group of Juga characterized by having the whorls smooth throughout ontogeny (Strong & Frest 2007).

life history

Juga snails are characterized as rasper-grazers, feeding on both algae and detritus, such as dead alder leaves (Furnish 1989, Allan 1995). Individuals in the Juga genus may live for 5-7 years, reaching sexual maturity in 3 years and continuing to grow (Furnish 1990). Adults in this genus are gonochoristic (as opposed to hermaphroditic). Reproduction is iteroparous (individuals are capable of having offspring many times), and most Juga species appear to breed and lay eggs once a year as adults (Frest and Johannes 2006). The same egg-laying localities are utilized year after year if undisturbed. There is no veliger stage, and juvenile snails emerge from eggs (Frest and Johannes 2006).

Collection dates for this species range from late May to October (Deixis MolluscDB 2009).

distribution

J. newberryi was originally distributed in the Deschutes River, Oregon, from at least Bend to the mouth, including Jefferson, Wasco, and Sherman counties. It is now known only from the lower 90 miles of the Deschutes River drainage where it occurs very sporadically below Pelton Dam, Wasco and Sherman counties (Frest and Johannes 1995, Strong and Frest 2007). It is absent from the mouth of the river, and from most Deixis collection sites (Frest and Johannes 1995).

Federal Land: Known sites for this species are on BLM lands in the Deschutes Wild and Scenic River in the Prineville District (Frest and Johannes 1995). Sites may occur on the Warm Springs Reservation (Frest and Johannes 1995).

Abundance: No information regarding the abundance of this species is available, but snails in this family commonly reach high abundances in headwater streams.

threats
Increasing recreational usage of the Deschutes Wild and Scenic River is a major concern for J. newberryi (Frest and Johannes 1995). This species seems to be absent now from the portions of the river above Pelton Dam, which are affected by discharge from Bend. It occurs only in the most undisturbed portions of the river, and seems to be sensitive to physical disturbance. This species is less tolerant of siltation and of slack water than Juga hemphilli maupinensis, J. silicua and J. plicifera (Frest and Johannes 1995). Any factors tending to downgrade water quality, including nutrient enhancement, would negatively impact this taxon.
conservation needs
Inventory: Since there are relatively few records of this species, further surveys at known sites will be valuable in evaluating the current status, range, population characteristics, and conservation needs of this species.

Management: Manage new and known sites and their associated watersheds to reduce the impacts of recreational activity, urban development, water diversions, construction activities, and other practices that may adversely affect water quality. Riparian habitat protection, including maintenance of water quality, substrate conditions, and canopy cover, would likely benefit and help maintain this species.

references

Allan, J. D. 1995. Stream ecology: structure and function of running waters. Chapman & Hall, New York, NY. 388 pp.

Burch, J. B. 1989. North American Freshwater Snails. Malacological
Publications, Hamburg, MI, 365 pp.

Deixis MolluscDB database. 2009. An unpublished collection of mollusk records maintained by Ed Johannes.

Frest, T. J. and E. J. Johannes. 1995. Interior Columbia Basin mollusk species of special concern. Final report: Interior Columbia Basin Ecosystem Management Project, Walla Walla, WA. Contract #43-0E00-4-9112. 274 pp. plus appendices.

Furnish, J. L. 1990. Factors affecting the growth, production and distribution of the stream snail Juga silicula (Gould). Unpublished PhD thesis, Oregon State University, 173 pp.

Lea, I. 1860. Descriptions of four new species of Melanidae of the United States. Proceedings of the academy of Natural Sciences of Philadelphia 12: 93.

Lea, I. 1862. Description of a new genus (Goniobasis) of the family Melanidae and eighty-two new species. Proceedings of the Academy of Natural Sciences of Philadelphia 14: 262–272.

Lea, I. 1863. New Melanidae of the United States. Journal of the Academy of Natural Sciences of Philadelphia (series 2) 5: 217–356.

NatureServe. 2009. “Juga newberryi”. Version 7.1 (2 February 2009). Data last updated: October 2009. Available at: www.natureserve.org/explorer (Accessed 17 May 2010).

Strong E. and F. Köhler. 2009. Morphological and molecular analysis of “Melania” jacqueti Dautzenberg & Fischer, 1906: from anonymous orphan to critical basal offshoot of the Semisulcospiridae (Gastropoda: Cerithioidea). Zoologica Scripta 38(5): 483-502. Available at: doi:10.1111/j.1463-6409.2008.00385.x (Accessed 17 May 2010).

Strong, E. E. and T. J. Frest. 2007. On the anatomy and systematics of Juga from western North America (Gastropoda: Cerithioidea: Pleuroceridae). The Nautilus 121(2): 43-65.
Taylor, D.W. 1966. Summary of North American Blancan Nonmarine Mollusks. Malacologia 4:1-172.

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