Stygobromus stellmacki - (Holsinger, 1967)
Stellmack Cave Stygobromid
Other English Common Names: Stellmack's Cave Amphipod
Taxonomic Status: Accepted
Related ITIS Name(s): Stygobromus stellmacki (Holsinger, 1967) (TSN 93929)
Unique Identifier: ELEMENT_GLOBAL.2.114506
Element Code: ICMAL05320
Informal Taxonomy: Animals, Invertebrates - Crustaceans - Amphipods
 
Kingdom Phylum Class Order Family Genus
Animalia Crustacea Malacostraca Amphipoda Crangonyctidae Stygobromus
Genus Size: D - Medium to large genus (21+ species)
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Concept Reference
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Concept Reference: Fitzpatrick, J.F., Jr. 1983. How to Know the Freshwater Crustacea. Wm. C. Brown Co. Publishers. Dubuque, Iowa. 277 pp.
Concept Reference Code: B83FIT01EHUS
Name Used in Concept Reference: Stygobromus stellmacki
Conservation Status
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NatureServe Status

Global Status: G1G2
Global Status Last Reviewed: 21Aug2002
Global Status Last Changed: 21Aug2002
Rounded Global Status: G1 - Critically Imperiled
Reasons: Only two populations are known. While other populations might be present, a large range is not expected. Aquifers supporting this species are both under threats of encroaching development and intensive agricultural land use. Demographic data is also very limited. Species has recently been confirmed extant (1992), although data does not exist to evaluate population trends.
Nation: United States
National Status: N1N2 (21Aug2002)

U.S. & Canada State/Province Status
Due to latency between updates made in state, provincial or other NatureServe Network databases and when they appear on NatureServe Explorer, for state or provincial information you may wish to contact the data steward in your jurisdiction to obtain the most current data. Please refer to our Distribution Data Sources to find contact information for your jurisdiction.
United States Pennsylvania (S1)

Other Statuses

IUCN Red List Category: VU - Vulnerable

NatureServe Global Conservation Status Factors

Range Extent: <100-250 square km (less than about 40-100 square miles)
Range Extent Comments: Endemic to two headwaters aquifers in nearby but different watersheds in Centre County, Pennsylvania. Limited information indicates that it inhabits aquifers at the headwaters of two adjacent Susquehanna River system watersheds: Spruce Creek and Spring Creek. One collection point for each watershed. The extent of distribution in these aquifers is unknown.

Number of Occurrences: 1 - 5
Number of Occurrences Comments: Known definitely from only 2 sites.

Population Size: 1 - 1000 individuals
Population Size Comments: Only 4 individuals have been collected from Millers Cave and 2 from Thompsons Meadow Spring aquifer. Large populations are probably not present.

Overall Threat Impact Comments: Region where population(s) is located is both agricultural and rapidly developing (urban, industrial). Potential threats to groundwater quality and quantity include: pollution by agricultural fertilizers and pesticides, siltation, pumping of water from aquifer for domestic/industrial supplies, industrial chemical spills. Some potential exists for pollution from forestry practices upslope of aquifer. An intermittent stream flows into the cave's sinkhole and entrance at one site. Capture of surface run-off in basins upslope of aquifer might limit water reaching subterranean habitat; presently this is probably an insignificant amount. Limestone mining near cave and/or aquifer would be a serious threat.

Intrinsic Vulnerability Comments: Troglobitic species, highly specialized.

Other NatureServe Conservation Status Information

Inventory Needs: Look for other populations in the Nittany Valley vicinity.

Protection Needs: Protect the two aquifers supporting EOs.

Distribution
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Global Range: (<100-250 square km (less than about 40-100 square miles)) Endemic to two headwaters aquifers in nearby but different watersheds in Centre County, Pennsylvania. Limited information indicates that it inhabits aquifers at the headwaters of two adjacent Susquehanna River system watersheds: Spruce Creek and Spring Creek. One collection point for each watershed. The extent of distribution in these aquifers is unknown.

U.S. States and Canadian Provinces

Due to latency between updates made in state, provincial or other NatureServe Network databases and when they appear on NatureServe Explorer, for state or provincial information you may wish to contact the data steward in your jurisdiction to obtain the most current data. Please refer to our Distribution Data Sources to find contact information for your jurisdiction.
Color legend for Distribution Map
Endemism: endemic to a single state or province

U.S. & Canada State/Province Distribution
United States PA

Range Map
No map available.


U.S. Distribution by County Help
State County Name (FIPS Code)
PA Centre (42027), Mifflin (42087)
* Extirpated/possibly extirpated
U.S. Distribution by Watershed Help
Watershed Region Help Watershed Name (Watershed Code)
02 Upper Juniata (02050302)+, Lower Juniata (02050304)+
+ Natural heritage record(s) exist for this watershed
* Extirpated/possibly extirpated
Ecology & Life History
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Basic Description: A cave amphipod.
General Description: MALE (holotype): Antenna 1, 50% as long as body, about 40% longer than antenna 2; primary flagellum with 28 segments; accessory flagellum reaching about 1/2 the length of 2nd primary flagellar segment. Antenna 2: peduncular segments 4 and 5 setose, ventral margin of 4 with a number of long, bristle-like setae; flagellum with 7 segments. Mandibular palpal segment 3 with 11 long setae; segment 2 with 10 to 13 setae. Maxilla 1, inner plate with 6 plumose setae apically. Maxilla 2, inner plate with 8 long, obliquely placed, plumose setae. Maxilliped, outer plate not extending as far as apex of 1st palpal segment. Lower lip, inner lobes distinct but small. Gnathopod 1: propod palmar margin long, convex, armed with a double row of about 15 rather irregular-sized spine teeth; posterior angle with 2 large spines, 3 or 4 smaller spines and 2 setae on outside, 7 small spines on inside; posterior margin convex, distally with 2 or 3 sets of setae, proximally without setae; superior lateral setae in 2 sets, inferior lateral setae double inserted; nail of dactyl very short; segment 5 with 2 rastellate setae on posterior margin. Gnathopod 2: propod palmar margin convex, armed with a double row of about 18 irregular sized spine teeth; posterior angle with 1 large spine, 2 smaller spines and several long setae on outside, 7 smaller spines on inside; posterior margin with 4 sets of setae on outside edge, 1 set of 3 small setae on inside edge; superior lateral setae triply and doubly inserted, inferior lateral setae mostly doubly inserted; dactyl claw very short; segment 5 with 3 rastellate setae on posterior margin coxal plate with 8 marginal setae. Coxal plates of pereopods 3 and 4 with 11 marginal setae each. Pereopod 7 between 55 and 60% as long as body, about equal in length to pereopod 6 and 30% longer than pereopod 5. Bases of pereopods 5-7 not broadly expanded, about as broad distally as proximally; posterior margins moderately convex; distoposterior lobes distinct but not much produced ventrally. Dactyl of pereopod 5 about 1/3 as long as corresponding propod; those of pereopods 6 and 7 about 1/4 as long as corresponding propods. Sternal gills absent on 1st pleonite; coxal gills large. Abdominal side plates: posterior margins with 1 setae each, gently rounded and incurving to small, well-defined, subacute corners; ventral margin of plate 2 with 4 spines, that of 3 with 2 spines. Pleopod 1, inner ramus about 30% longer than peduncle. Uropod 1: outer ramus equal in length to inner ramus, with 13 spines; inner ramus with 13 spines; peduncle without distal process, armed with 18 spines. Uropod 2: outer ramus about equal to inner ramus in length, about 80% as long as peduncle, armed with 10 spines; inner ramus with 13 spines; peduncle with 8 spines. Uropod 3: outer ramus about 40% as long as peduncle, armed apically with 4 or 5 spines. Telson subrectangular, about 25% longer than broad; apical margin with shallow excavation, armed on either lobe with 8 to 10 rather slender, unequal spines (Holsinger, 1967). NOTE: Above description is based upon a single male specimen, 14.2 mm long. FEMALE: Antenna 1, 55-62 % length of body, 50-55% longer than antenna 2; primary flagellum with 25-26 segments. Flagellum of antenna 2 with 8-10 segments. Gnathopod 1: propod a little larger than 2nd propod; segment 5 with 2 rastellate setae. Gnathopod 2: propod with 3 or 4 sets setae on posterior margin; segment 5 with 2-5 rastellate setae. Coxal gill on pereopod 7. Three, rather small median sternal gills on pereonites 2-4; 2 pairs bifurcate lateral sternal gills on pereonites 6 and 7; sternal gills absent from pleonite 1. Ramus of uropod 3 with 4 apical spines. Aprical margin of telson with or without small notch, armed with 16 spines (Holsinger, 1978). NOTE: Above description is based upon only two female specimens; largest: 16.5 mm long.
Diagnostic Characteristics: Moderately large, rather aberrant troglobitic species differing significantly from all other species of STYGOBROMUS by the absence of distal peduncular process on uropod 1. Distinguished from other species of the "emarginatus" group by the more setose 4th peduncular segment of antenna 2, presence of setae on posterior margin of propod of gnathopod 1, small spines on outside margin of posterior angle of 2nd gnathopod propod, shorter dactyl claws of gnathopods, presence of rastellate setae on segment 5 of both gnathopods, and larger coxal gills. Further differentiated from other species of the "emarginatus" subgroup by having up to 18 apical spines on telson (Holsinger, 1967).
Reproduction Comments: No information specifically describing the reproduction of S. STELLMACKI is known. Two ovigerous female S. ALLEGHENIENSIS, one at parturition, were collected with an adult female S. STELLMACKI on May 2 (Charles Bier, 1992, field survey forms, Pennsylvania Natural Diversity Inventory).
Ecology Comments: Little ecological information is available and only limited assumptions can be made. Population density at Miller Cave is apparently much lower than other pericaridans or STYGOBROMUS in this system. For example, during field surveys the ratio of collections of S. ALLEGHENIENSIS, which occupies the same habitat, to S. STELLMACKI is approximately 20/1 (Charles Bier, Pennsylvania Natural Diversity Inventory). The specific micro-habitat and niche occupied by S. STELLMACKI in aquatic cave and aquifer sites is not known. Use of habitats by immature individuals or by adults during reproduction is unknown.
Non-Migrant: N
Locally Migrant: N
Long Distance Migrant: N
Mobility and Migration Comments: Mobility within or between subterranean habitats is unknown, but is probably similar to that of other STYGOBROMUS and is probably very slow and limited. S. STELLMACKI was once captured in Sept. at a drift net in a spring run a short distance downstream from a large spring head where it is assumed to have emerged. However, once in surface stream, viability is doubtful.
Subterranean Habitat(s): Subaquatic
Special Habitat Factors: Subterranean obligate
Habitat Comments: Inhabits small streams and seepage-pools in one small limestone (Ordovician) solution cave (Holsinger, 1978): Wide, shallow mud-bottom pool on upper level of cave (Charles Bier, 1992, field survey forms, Pennsylvania Natural Diversity Inventory): Lower end of small medium-gradient stream, a tributary to main stream in cave. Shallow runs and light riffles, 1-6 cm deep, with some of flow deeper through substrate. Substrate: gravel, sand with stones and cobbles, and some organic detritus (specimen collected by Miller in 1983, in collection of John Holsinger): Apparently also inhabits smaller aquatic subterranean systems as suggested by the presence of two specimens at a rising spring. This is probably an aquifer that can not be entered for survey.
Adult Food Habits: Detritivore, Scavenger
Immature Food Habits: Detritivore, Scavenger
Food Comments: Diet and foraging assumed to be basically similar to other amphipods and peracaridians, yet modified by the subterranean environment. Food items probably include bacteria, detritus and carrion (Thorp and Covich, 1991). Foraging might also include coprophagous feeding, although could be drawn all, or in part, to increased bacteria populations rather than directly to dung. Genus does respond as a scavenger to bait left in cave, e.g., shrimp tails or crayfish flesh (Holsinger, pers. comm.). Feeding apparently takes place on surface of stream bed, or within substrate of stream (e.g., in gravel, under rocks) or aquifer.
Adult Phenology: Circadian
Immature Phenology: Circadian
Phenology Comments: No specific information is available. Daily activity is believed to be carried out equally around the clock given the subterranean environment. Seasonality of behavior or life-cycle, if present, might be based upon slight water temperature fluctuations. Apparently both of the S. STELLMACKI collected in a drift net at the outflow Thompsons Meadow Spring were captured in Sept. (specimen collect by Miller in 1983, in collection of John Holsinger). Additional information is needed to determine if this collection represents dispersal.
Length: 1.4 centimeters
Economic Attributes
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Economic Comments: No identified economic value. Species might function as a groundwater quality indicator. This is an unique species that is important for taxonomic and evolutionary science.
Management Summary
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Biological Research Needs: Information detailing real threats and levels of sensitivity to pollutants.
Population/Occurrence Delineation Not yet assessed
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Population/Occurrence Viability
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U.S. Invasive Species Impact Rank (I-Rank) Not yet assessed
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Authors/Contributors
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NatureServe Conservation Status Factors Edition Date: 15Jun1992
NatureServe Conservation Status Factors Author: Bier, Charles W.
Element Ecology & Life History Edition Date: 15Jun1992
Element Ecology & Life History Author(s): Bier, Charles W.

Zoological data developed by NatureServe and its network of natural heritage programs (see Local Programs) and other contributors and cooperators (see Sources).

References
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  • Fitzpatrick, J.F., Jr. 1983. How to Know the Freshwater Crustacea. Wm. C. Brown Co. Publishers. Dubuque, Iowa. 277 pp.

  • Holsinger, J.R. 1967. Systematics, speciation, and distribution of the subterranean amphipod genus Stygonectes (Gammaridae). Bulletin of the United States National Museum, 259: 1-176.

  • Holsinger, J.R. 1978. Systematics of the subterranean amphipod genus Stygobromus (Crangonyctidae). Part II: Species of the eastern United States. Smithsonian Contributions to Zoology, 266: 1-144.

  • Holsinger, J.R., 1976. The Cave Fauna of Pennsylvania in Geology and Biology of PA Caves, Edited by W.B. White. PA Geologic Survey, General Geology Report 66.

  • Holsinger, J.R., 1978 SYSTEMATICS OF THE SUBTERRANEAN AMPHIPOD GENUS STYGOBROMUS(CRANGONYCTIDAE), PART 2: SPECIES OF THE EASTERN US. SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY, NUMBER 266

  • McLaughlin, P.A., D.K. Camp, M.V. Angel, E.L. Bousfield, P. Brunel, R.C. Brusca, D. Cadien, A.C. Cohen, K. Conlan, L.G. Eldredge, D.L. Felder, J.W. Goy, T. Haney, B. Hann, R.W. Heard, E.A. Hendrycks, H.H. Hobbs III, J.R. Holsinger, B. Kensley, D.R. Laubitz, S.E. LeCroy, R. Lemaitre, R.F. Maddocks, J.W. Martin, P. Mikkelsen, E. Nelson, W.A. Newman, R.M. Overstreet, W.J. Poly, W.W. Price, J.W. Reid, A. Robertson, D.C. Rogers, A. Ross, M. Schotte, F. Schram, C. Shih, L. Watling, G.D.F. Wilson, and D.D. Turgeon. 2005. Common and scientific names of aquatic invertebrates from the United States and Canada: Crustaceans. American Fisheries Society Special Publication 31: 545 pp.

  • Thorp, J.H. and A.P. Covich (eds). 1991. Ecology and classification of North American freshwater invertebrates. Academic Press, Inc., Boston, MA. 911pp.

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