SPECIES FACT SHEET

Scientific Name: Stygobromus oregonensis (Holsinger 1974)Common Name(s): Oregon Cave Amphipod Phylum: CrustaceaClass: MalacostracaOrder: AmphipodaSuborder: GammarideaFamily: CrangonyctidaeConservation Status:

Global Status: G1G2 (last reviewed 29 June 2004)National Status (United States): N1N2 (21 August 2002)State Statuses: S1S2 (OR)Federal Status (United States): Not listed (NatureServe 2017)IUCN Red List: Not yet assessed (IUCN 2017)Technical Description:

Adult: Amphipods are shrimp-like crustaceans with elongate, laterally compressed bodies and seven (rarely six) pairs of leg-like appendages (Triplehorn and Johnson 2005; Voshell 2002). Amphipods do not have carapaces (i.e., hard thorax coverings), which differentiates them from most other crustaceans. The anterior pairs of legs are directed downward and forward, while the posterior legs are usually turned upward and backward. The abdominal segments are more or less fused with the thoracic segments, and the carapace (hard covering of the thorax common in other crustaceans) is lacking. Each of the six abdominal segments has one pair of short appendages on the underside. The cephalothorax (a fusion of the head and first thoracic segment) has two pairs of antennae.

Species in the Stygobromus genus typically lack eyes and pigmentation (Taylor and Hoslinger 2011). The type-series of S. oregonensis consists of two fully mature females measuring 9.5 mm (0.37 in.) and 11.0 mm (0.43 in.) in body length, excluding appendages. Holsinger (1974) describes this species in great detail, with key identifying features as follows:

Palm of gnathopodal propod 2 convex with double row of 16 spine teeth; pleonal plates with small, subacute posterior corners; telson with 15 or 16 apical spines.

1

This relatively large species (most Stygobromus are under 10 mm (0.39 in.) in length) can be easily distinguished from other species of the hubbsi group by the following traits: numerous long, stiff setae and slender spines on peduncular segments IV and V of the second antennae; proportionately large propod of gnathopod I with very long, heavily spined palm; convex palm of gnathopodal propod II with a double row of 16 spine teeth; gnathopodal propods with doubly and triply inserted superior medial setae; posterior margins of the bases of pereopods V-VII convex; posterior marginal setae of pleonal plates II and III positioned midlaterally; pleonal plates with small, subacute posterior corners; and the comparatively large ramus of uropod III with 5 rather long spines (Holsinger 1974; Wang and Holsinger 2001).

Immature: Immature specimens look similar to adults, are typically smaller, and are not reproductively mature, making identification more difficult.

Life History:

Adults: Stygobromus are within the suborder Gammaridea, which is a diverse grouping whose members occupy many types of habitats. Species in the genus Stygobromus are found in subterranean groundwater habitats, such as cave pools and streams, phreatic water in wells, seeps and springs, and underflow of surface streams (Taylor and Hoslinger 2011). Little is known about the life cycle, development, ecological interactions, or population biology of S. oregonensis. Sexually mature females have been collected in April and January, although this may be more reflective of sampling period than the phenology of the animal.

Gammaridean amphipods are mostly dioecious, and have external fertilization. In general, amphipod eggs are deposited in a brood pouch (i.e., marsupium) on the underside of the adult female. Eggs take 1-3 weeks to hatch, and female gammarideans carry embryos in the pouch. Most species complete their life cycle (egg to adult) in one year or less (Sainte-Marie 1991; Fasulo 2001). Subterranean species appear to have an exceptionally long lifespan and may live for four to six years (Voshell 2002). One of the foods of Stygobromus species is bacteria in the water (Drost and Blinn 1997).

All Stygobromus species exhibit some degree of troglomorphy, typical in cave organisms. These characteristics for subterranean existence in crangonyctid amphipods include loss or reduction of eyes and pigmentation, elongated appendages, lowered metabolic rates, and increased

2

developmental periods (Culver et al. 2010; Ethridge et al. 2013). Additionally, the metabolic rate in members of the Stygobromus genus is lower than that of surface-dwelling amphipods, likely due to reduced food availability and hypoxia (Spicer 1998).

Immature: The eggs hatch in one to three weeks, and the young amphipods remain in the pouch for about one to eight days. They are released the first time their mother sheds her skin after her next mating (Voshell 2002). The immature stages resemble the adults, and undergo successive molts (usually between 8 and 9) until maturity. It is unclear whether sexual maturity is reached after a fixed number of molts or the completion of gonad development, both of which have temperature dependent rates (Highsmith and Coyle 1991).

Range, Distribution, and Abundance:

Type Locality: Small unnamed cave near Roseburg, Douglas County, Oregon (Holsinger 1974).

Range: Stygobromus is a relatively large genus, consisting of approximately 135 described species, most of which are from the United States (Holsinger 1974). Stygobromus oregonensis is known from the Klamath Mountains Ecoregion in southwest Oregon (ORBIC 2016). Although many caves appear to be physically isolated from other caves, there are potentially numerous interconnecting cracks and crevices for amphipod distribution between larger, explorable caves, particularly in areas with fractured bedrock (Holsinger 2008, pers. comm.).

Distribution: This species is currently known from a single small cave on private land near Roseburg, Douglas County, Oregon (Holsinger 1974; ORBIC 2016), where it was collected by Jim Riggs on two occasions: in April, 1967, and in January, 1983 (Holsinger 2008, pers. comm.). The presence of subterranean groundwater, such as in small pools at the bottom of caves and crevices, is probably the limiting factor in the distribution of this species (Holsinger 2008, pers. comm.). However, this species may be found in similar groundwater habitat in Oregon and even into California (Holsinger 2008, pers. comm.).

BLM/Forest Service Land:

Documented: There are no records of S. oregonensis on federal lands.

3

Suspected: This species is suspected from similar groundwater habitat on the Umpqua National Forest due to close proximity of the current record, and presence of potential habitat. Roseburg BLM District personnel have determined that although there is Roseburg BLM land nearby the current record, the District does not have suitable habitat for the species. However, this species may have a wider range in Oregon occurring on additional federal lands in southwest Oregon.

Abundance: Two individuals of this species were collected on both sample occasions, but no abundance estimates of this species have been made. Stygobromus species occur in low abundance wherever they are found (Drost and Blinn 1997).

Habitat Associations:

Species in the genus Stygobromus are found in subterranean groundwater habitats, such as cave pools and streams, phreatic water in wells, seeps and springs, and underflow of surface streams (Holsinger 1974; Taylor and Hoslinger 2011). The small cave where this species was found is a crevice in Lower Eocene basalt with water sometimes occurring about 9.1m (30 feet) below the entrance (Holsinger 1974). Stygobromus oregonensis are obligate aquatic subterranean (i.e., stygobiont) amphipods. The collected specimens on the 1983 sample occasion were from a small pool at the bottom of the cave where the water temperature was around 50 degrees Fahrenheit (Holsinger 2008, pers. comm.). The presence of subterranean groundwater, such as in small pools at the bottom of caves and crevices, is probably the limiting factor in the distribution of this freshwater species (Holsinger 2008, pers. comm.).

Threats:

Disturbance and habitat alteration can be the most significant threats to cavern wildlife. Cave habitats are sensitive to disturbance caused by humans, including vandalism and recreation, from tourism to spelunking. These activities can negatively impact cave habitats by altering temperature, disturbing wildlife, and introducing pollutants. Additionally, changing climate, increased human consumption, and irrigation practices are leading to declines in groundwater and groundwater-dependent habitats (Kløve et al. 2014). In the West, groundwater sources are being depleted and over-pumped (Aeschbach-Hertig and Gleeson 2012).

4

The restricted, subterranean habitat of this species subjects it to a wide variety of freshwater disturbances. Since caves are underground drainage conduits for surface runoff, their biological communities are often subjected to significant quantities of nutrients and contaminants (Lewis 2001). Potential groundwater contaminants include:

Herbicides and insecticides applied to crops, lawns, and roadsides Fertilizers applied to crops and lawns Human and livestock fecal waste, including sewage plant effluent, septic

field waste, campground outhouses, feedlots, and grazing pastures Hazardous materials from accidental spills or deliberate dumping,

including road salting

(Panno et al. 1998; Harvey and Skeleton 1968; Lewis 1996, reviewed in Lewis 2001).

Changes in water-table hydrology due to human development (withdrawal of excessive amounts of water from wells) and global climate change (particularly climatic variations in the amount of precipitation and rate of uptake by plants) may also impact this species. Additionally, the loss of vegetation aboveground can affect cave habitats and the wildlife that depends on it by increasing erosion and polluting runoff.

Conservation Considerations:

Research: The development of a threats analysis and a conservation assessment would assist in the conservation of S. oregonensis populations, and other Stygobromus spp. (Taylor 2018). Research to better understand the origin, interspecific relationships, and biogeography of Stygobromus spp. is needed (Taylor and Holsinger 2011; Taylor 2018). Unfortunately, cryptic subterranean groundwater habitats suitable for Stygobromus spp. are often not easily accessible, therefore remaining under-surveyed (Taylor and Holsinger 2011). In the West, additional taxonomic study, including molecular analyses and environmental DNA (eDNA), will assist in the conservation of these species by advancing our understanding in taxonomic and biogeographic relationships (Taylor and Holsinger 2011; Taylor 2018).

Inventory: The distribution of this species is expected to be much larger than is documented, including much of southern Oregon and possibly south into California (Holsinger 2008, pers. comm.). Searching potential habitats (e.g.

5

caves, seeps, wells, spring flows) is the only way to find out if this species occurs beyond its type-locality (Holsinger 2008, pers. comm.). Considering the potentially numerous interconnecting cracks and crevices in many cave systems (particularly in karst areas with lava flow or fractured bedrock), it is very unlikely that this species is restricted to a single cave (Holsinger 2008, pers. comm.). With diligent search effort, a number of other karst species have been found well beyond their original type-localities (Holsinger 2008, pers. comm.). Survey subterranean groundwater habitat in southern Oregon for new population sites of this species. Address habitat in both unsurveyed and well-studied cave systems. Oregon Caves National Monument (OCNM), for example, has a record of amphipods from ~15 years ago but the specimens (probably Stygobromus mysticus) were not well preserved and are too damaged to be positively identified to species (Roth 2008, 2018 pers. comm.). There have not been recent survey efforts for this taxon at OCNM, however additional survey work may be reveal this (or other) Stygobromus species (Roth 2018, pers. comm.).

A genetic analysis of amphipods identified a high level of genetic diversity, suggesting that the cave and spring faunas of the Great Basin region have not been thoroughly sampled to date (Taylor and Holsinger 2011). Thorough inventories can be challenging due to the physical isolation and often remote location of aquatic habitats where this species may be found. The occurrence of numerous isolated springs associated with the bases of mountain ranges offers the potential of finding additional populations of Stygobromus species within this region. It is likely that further exploration of groundwater habitats will be followed by additional discoveries, such as the discovery of Stygobromus albapinus n. sp. in Nevada (Taylor and Holsinger 2011).

Management: Protect known sites and their watersheds from activities that would damage or alter groundwater quality or hydrology. Managers could also protect native vegetation in the riparian area to further enhance water quality vital to the survival of cave ecosystems. To manage for excessive recreation, close cave entrances and avoid expanding cave openings, which can affect wildlife use as well as air circulation patterns and temperatures. Additional steps to protect cave habitats might include keeping specific cave locations undisclosed to preserve these unique habitats.

Version 2: Prepared by: Katie Hietala-Henschell

6

The Xerces Society for Invertebrate ConservationDate: June 2018

Reviewed by: Candace FallonThe Xerces Society for Invertebrate ConservationDate: June 2018

Version 1: Prepared by: Sarah Foltz JordanThe Xerces Society for Invertebrate ConservationDate: December 2008

Reviewed by: Sarina Jepsen The Xerces Society for Invertebrate ConservationDate: January 2009ATTACHMENTS:

(1)References (2)List of pertinent or knowledgeable contacts (3)Map of known records in Oregon(4)Illustrations of this species(5)Survey protocol, including specifics for this species

ATTACHMENT 1: References

Aeschbach-Hertig, W. and T. Gleeson. 2012. Regional strategies for the accelerating global problem of groundwater depletion. Nature Geoscience 5: 853-861.

Culver, D.C., J.R. Holsinger, M.C. Christman, and T. Pipan. 2010. Morphological differences among eyeless amphipods in the genus Stygobromus dwelling in different subterranean habitats. Journal of Crustacean Biology. 30(1):68-74.

Ethridge, J.Z., J.R. Gibson, and C.C. Nice. 2013. Cryptic diversity within and amongst spring-associated Stygobromus amphipods (Amphipoda: Crangonyctidae). Zoological Journal of the Linnean Society. 167:227-242.

Fasulo, T.R. 2001. “Featured Creatures: common name: terrestrial amphipods or lawn shrimp scientific name: (Crustacea: Amphipoda: Talitridae).” University of Florida Entomology and Nematology. July 2001. Available at: http://entnemdept.ufl.edu/creatures/misc/amphipods.htm

7

Highsmith, R.C. and K.O. Coyle. 1991. Amphipod life histories: community structure, impact of temperature on decoupled growth and maturation rates, productivity, and P:B ratios. American Zoologist. 31:861-873.

Holsinger, J.R. 1974. Systematics of the subterranean amphipod genus Stygobromus (Gammaridae), Part I: Species of the western United States. Smithsonian Contributions to Zoology. 160:-63.

Holsinger, J. 2008. Personal communication with Sarah Foltz, the Xerces Society. Eminent Scholar Emeritus and Professor Emeritus of Biological Sciences, Department of Biological Sciences, Old Dominion University, Norfolk, Virginia 23529-0266, USA 

[ITIS] Integrated Taxonomic Information System. 2017. [web application]. Available at: https://www.itis.gov

[IUCN] International Union for Conservation of Nature. 2017. The IUCN red list of threatened species. [web application]. Available at: http://www.iucnredlist.org/search

Kløve, B., P. Ala-Aho, G. Bertrand, J.J. Gurdak, H. Kupfersberger, J. Kværner, T. Muotka, H. Mykrä, E. Preda, P. Rossi, C.B. Uvo, E. Velasco, and M. Pulido-Velazquez. 2014. Climate change impacts on groundwater and dependent ecosystems. Journal of Hydrology. 518:250-266.Lewis, J.J. 1996. The devastation and recovery of caves affected by industrialization. Proceedings of the 1995 National Cave Management Symposium, October 25-28, 1995, Spring Mill State Park, Indiana. 214-227.

Lewis, J. 2001. Conservation Assessment for Pocahontas Cave Amphipod (Stygobromus nanus). Report for the USDA Forest Service, Eastern Region. Provided by J. Lewis and Associates, Biological Consulting, Clarksville, IN. 9pp.

NatureServe. 2017. “Stygobromus oregonensis.” NatureServe Explorer: An online encyclopedia of life [web application]. Feb. 2008. Version 7.0. NatureServe, Arlington, Virginia. Available at: http://www.natureserve.org/explorer

[ORBIC] Oregon Biodiversity Information Center. 2016. Rare, threatened and endangered species of Oregon. Institute for Natural Resources, Portland

8

State University, Portland, Oregon. 130 pp. Available at http://inr.oregonstate.edu/sites/inr.oregonstate.edu/files/2016-rte-book.pdf

Panno, S.V., W.R. Kelly, C.P. Weibel, I.G. Krapac, and S.L. Sargent. 1998. The effects of land use on water quality and agrichemical loading in the Fogelpole Cave groundwater basin, southwestern Illinois. Proceedings of the Illinois Groundwater Consortium Eighth Annual Conference, Research on agriculture chemicals in Illinois groundwater, 215-233.

Roth, J. 2008. Personal communication with Sarah Foltz Jordan, the Xerces Society. John Roth, Resource Manager, Oregon Caves National Monument, Cave Junction, OR.

Roth, J. 2018. Personal communication with Katie Hietala-Henschell, the Xerces Society. John Roth, Resource Manager, Oregon Caves National Monument, Cave Junction, OR. June 25.

Sainte-Marie, B. 1991. A review of the bionomics of aquatic gammaridean amphipods: variation on life history traits with latitude, depth, salinity and superfamily. Hydrobiologia. 223:189-227

Spicer, J.R. 1998. Is the reduced metabolism of hypogean amphipods solely a result of food limitation? Hydrobiologia. 377:201-204.Taylor, S.J. and J.R. Holsinger. 2011. A new species of the subterranean amphipod crustacean genus Stygobromus (Crangonyctidae) from a cave in Nevada, USA. Subterranean Biology. 8:39-47.

Taylor, S.J. 2018. The current state of knowledge for the globally, nationally and state imperiled groundwater amphipod, Stygobromus oregonensis Holsinger 1974 (Crustacea: Amphipoda: Crangonyctidae). 5 pp.

Triplehorn, C. and N. Johnson. 2005. Introduction to the Study of Insects. Thomson Brooks/Cole, Belmont, CA. 864pp.

Voshell J.R. 2002. A Guide to Common Freshwater Invertebrates of North America. The McDonald and Woodward Publishing Company, Blacksburg, Virginia. 442pp.

Wang, D. and J.R. Holsinger. 2001. Systematics of the subterranean amphipod genus Stygobromus (Crangonyctidae) in western North America, with emphasis on species of the hubbsi group. Amphipacifica. 3(2):39-147.

9

Map references:

Holsinger, J. 2008. Personal records shared with Sarah Foltz Jordan, the Xerces Society. Eminent Scholar Emeritus and Professor Emeritus of Biological Sciences, Department of Biological Sciences, Norfolk, Virginia. 

ATTACHMENT 2: List of pertinent, knowledgeable contacts

John R. Holsinger, Eminent Scholar Emeritus and Professor Emeritus of Biological Sciences, Department of Biological Sciences, Old Dominion University, Norfolk, VA 23529-0266. 

Steve J. Taylor, Associate Research Professor, Colorado College, Colorado Springs, CO 80903. 

10

ATTACHMENT 3: Map of known Stygobromus oregonensis records in Oregon

Known record of Stygobromus oregonensis in Oregon, relative to Forest Service and BLM land. The red polygon is a broad representation of potential distribution for this species. John Holsinger (a Stygobromus expert and the species author) based the polygon on the presence of subterranean

11

groundwater, such as in small pools at the bottom of caves and crevices, based on geological regions (Holsinger 2008, pers. comm.)

12

ATTACHMENT 4: Illustrations of this species

Stygobromus oregonensis, female paratype (USNM Number: 142798). Figure shows gnathopods (a,b), pereopods (c,d), uropod (e), telson (f), and pleonal plates (g). Used under Fair Use Law, information provided by the National Museum of Natural History, Smithsonian Institution (http://www.nmnh.si.edu/), 10th and Constitution Ave. N. W. DC 20560-0193. Drawings can be found in Holsinger (1974).

13

Female Stygobromus oregonensis (USNM Number: 142798). Figure shows pereopod (a), antennae (b,c), and uropods (d). Used under Fair Use Law, information provided by the National Museum of Natural History, Smithsonian Institution (http://www.nmnh.si.edu/), 10th and Constitution Ave. N. W. DC 20560-0193. Drawings can be found in Holsinger (1974).

ATTACHMENT 5: Survey Protocol

Survey Protocol:

Taxonomic group: Stygobromus spp.

Where: Surveys for members in the Stygobromus genus should occur in subterranean groundwater habitats, such as cave pools and streams, phreatic water in wells, seeps and springs, and underflow of surface streams. Surveys for Stygobromus within this region could target isolated springs associated with the bases of mountain ranges. Although many caves appear

14

to be physically isolated from other caves, there are potentially numerous interconnecting cracks and crevices for amphipod distribution between larger, explorable caves, particularly in areas with fractured bedrock (Holsinger 2008, pers. comm.). Collections could occur from small pools at the bottom of the cave where water temperatures are cool (around 50 degrees Fahrenheit).

When: Sampling in subterranean groundwater habitats (e.g., cave pools and streams, phreatic water in wells, seeps and springs, and underflow of surface streams) can be conducted any time.

How to Survey: Accurate yet environmentally sensitive methods to estimate amphipod population sizes in subterranean groundwater systems are not well-developed. Cave-dwelling species collections should be limited to a few specimens. Work slowly and take care where you place your hands and feet, as there are many sensitive features, including fauna and their habitats.

Typically, Stygobromus specimens are collected by sucking them up into a syringe or capturing them in a fine-mesh dip-net (mesh size <2mm). A small jar, baited with fresh shrimp and left in the water for 1 to 2 hours, can also be used to collect specimens (Holsinger 2008, pers. comm.). Freshwater amphipods should be preserved in 70-75% ethanol (Holsinger 1976), and handled and packaged carefully to prevent damage to individuals. Since the species description is based on fully mature female specimens, collection of this sex and life-stage would ease the identification process (Holsinger 2008, pers. comm.). However, identification requires a taxonomic expert.

Collection labels should include the following information: date, time of day, collector, detailed locality (including cave name, geographical coordinates, mileage from named location, elevation, etc.), and detailed cave/waterbody habitat information (including size, substrate characteristics, and water quality, temperature and depth). Complete determination labels include the species name, sex and maturity (if known), determiner name, and date determined.

Species-Specific Survey Details:

Stygobromus oregonensis

Surveys for this species could target caves in Douglas County and adjacent counties in southern Oregon with similar groundwater habitat. When

15

searching for new sites, efforts should be made to cover a range of cave sizes, elevations, and geographic locales. Within cave systems, survey at regular intervals in areas where water or mud occurs. Careful visual searching is the only known method of estimating abundance of this species (Holsinger 2008, pers. comm.).

References (survey protocol only):

Holsinger, J.R. 1976. The Freshwater Amphipod Crustaceans (Gammaridae) of North America. U.S. EPA Water Pollution Control Research Series 18050 ELDO4/72.

Holsinger, J.R. 2008. Personal communication with Sarah Foltz Jordan, the Xerces Society. Eminent Scholar Emeritus and Professor Emeritus of Biological Sciences, Department of Biological Sciences, Old Dominion University, Norfolk, Virginia 23529-0266, USA 

16