Horton H. Hobbs

A Reassessment of the Conservation Status of Crayfishes of the United States and Canada after 10+ Years of Increased Awareness

Abstract The American Fisheries Society Endangered Species Committee herein provides a list of all crayfishes (families Astacidae and Cambaridae) in the United States and Canada that includes common names; state and provincial distributions; a comprehensive review of the conservation status of all taxa; and references on biology, conservation, and distribution. The list includes 363 native crayfishes, of which 2 (⟨ 1%) taxa are listed as Endangered, Possibly Extinct, 66 (18.2%) are Endangered, 52 (14.3%) are Threatened, 54 (14–9%) are Vulnerable, and 189 (52.1%) are Currently Stable. Limited natural range continues to be the primary factor responsible for the noted imperilment of crayfishes; other threats include the introduction of nonindigenous crayfishes and habitat alteration. While progress has been made in recognizing the plight of crayfishes, much work is still needed.

Conservation Status of Crayfishes of the United States and Canada

Abstract The American Fisheries Society (AFS) Endangered Species Committee herein provides a list of all crayfishes (families Astacidae and Cambaridae) in the United States and Canada that includes state and provincial distributions; a comprehensive review of the conservation status of all taxa; and references on biology, conservation, and distribution of crayfishes. The list contains 338 native crayfishes, of which 2 (< 1%) taxa are listed as endangered, possibly extinct; 65 (19.2%) as endangered; 45 (13.3%) as threatened; 50 (14.8%) as special concern; and 176 (52.0%) as currently stable. Limited natural range is implicated as the primary factor responsible for the noted imperilment of crayfishes; other threats include habitat alteration and the introduction of nonindigenous crayfishes. Using the best available information, we estimate that almost 50% of crayfishes in United States and Canada are in need of conservation recognition. We hope that this report spurs increased research efforts from aquatic ...

ON THE DISTRIBUTION OF THE CRAYFISH GENUS PROCAMBARUS (DECAPODA: CAMBARIDAE)

ABSTRACT The ranges of the 17 subgenera of the genus Procambarus, comprising 152 species and subspecies occurring in North America and Middle America, are illustrated and briefly outlined. A graphical compilation of the distribution of these crayfishes is presented showing that the greatest number of species and subspecies occur in the southeastern United States, with a decline in numbers centrifugally to Mexico where two centers of concentration occur on the eastern versant: one north and the other south of the Cordillera Volcanica Transversal. Evidence is presented for a postulated Procambarus track extending from the eastern part of the United States southwestward through Mexico, and thence northeastward to Cuba.

A Generic Revision of the Crayfishes of the Subfamily Cambarinae (Decapoda, Astacidae) with the Description of a New Genus and Species

Recent students of the crayfishes are finding the conservative treatment given by Ortmann and Faxon to the species comprising the genus Cambarus less and less satisfactory in the light of increasing knowledge of the group. Ortmann and Faxon divided this genus into a number of subgenera, sections and groups, some of which, because of their distinctiveness, seem to deserve the status of higher categories. As long as Cambarus was small and the available information scanty, the conservative classification was not only logical but definitely practical. Now, with more accurate knowledge of specific ranges, and with the finding of many new species, new relationships have been discovered which are not adequately expressed by Ortmanns and Faxons treatments. The splitting of the old genus Cambarus into two genera by Creaser (1933) has done little to relieve the congestion.

Mycoflora of a Trogloxenic Cave Cricket, Hadenoecus cumberlandicus (Orthoptera: Rhaphidophoridae), from Two Small Caves in Northeastern Kentucky

Abstract External and internal mycoflora of the cave cricket Hadenoecus cumberlandicus Hubbell were examined and consisted of eight deuteromycetes (Aspergillus niger, Beauveria sp., Colletotrichum acutatum, Geotrichum candidum, Penicillium sp., Pestalotia sp., Trichoderma sp., and Mycelia sterilia), five zygomycetes (Absidia corymbifera, Cunninghamella sp., Mucor racemosus, Phycomyces sp., and Rhizopus sp.), and one ascomycete (Thielavia terrestris). Most are soil saprophytes and typical in a cave setting. Internal isolates included Colletotrichum acutatum and Pestalotia sp., plant pathogens that were probably acquired during foraging. Noteworthy among external fungi was Beauveria sp., a genus of entomopathogens, revealing that fungi may have the potential to impact the cave ecosystem by reducing cave cricket populations.

The Origins and Affinities of the Troglobitic Crayfishes of North America (Decapoda, Astacidae). I. The Genus Cambarus

One of the most interesting phases of the history of crayfish dispersal and modification is that associated with the origins of troglobites. There are a few generalizations which can be drawn concerning the distributions and the origins of the several stocks which have engendered populations that have been able to meet the demands of a subterranean existence. In order to gain the proper perspective of the distributional relationships of the cavernicolous crayfishes with their epigean relatives, a brief summary of the distributions of the four genera with hypogean representatives is presented. The largest genus in the family Astacidae, Procambarus, comprises more than 100 species and subspecies of which six are true troglobites. The range of the genus extends from Cuba, Guatemala and Honduras northward to Illinois and southern New England. Most of the species are found in the southeastern parts of the United States and Mexico where they are confined largely to the Coastal Plain and Piedmont Provinces. Only in Mexico have representatives been able to cross the divide into the Pacific drainage. The six albinistic species and subspecies are known only from Florida (4), Veracruz, Mexico (1), and Pinar del Rio, Cuba (1); that from the latter has not been described. The monotypic genus Troglocambarus is known only from caves in the Florida peninsula. The genus Orconectes, the second largest in the family, is composed of approximately 60 species and subspecies, and among them five troglobitic taxa have been recognized. The range of this genus is largely confined to the Mississippi and Great Lakes drainage systems, but a few species have reached the extreme southeastern part of the United States, and two occur east of the Appalachian system in an area extending from Maine to Virginia. The hypogean representatives are found in the Interior Low Plateaus of southern Indiana, central Kentucky and Tennessee, and northern Alabama. The genus Cambarus, comprising some 40 species and subspecies, is represented by six troglobitic species within the United States. Its range extends from the Gulf of Mexico (Texas to northern Florida) to Canada; however, most of the species occur in the eastern part of the United States, along the slopes of and in streams arising in the Appalachian Mountains. The present discussion concerns the cavernicoles of this genus.

A SAMPLER FOR SIMULTANEOUSLY MEASURING DRIFT AND UPSTREAM MOVEMENTS OF AQUATIC MACROINVERTEBRATES

ABSTRACT A simple sampler for concurrently collecting drifting as well as upstream-moving organisms is described. It is constructed of inexpensive, readily available material and can be used in high discharge and low flow lotic environments. The five-sectioned trap is designed for equal quantitative sampling of drifting and upstream-moving organisms. Collecting nets can be quickly attached or removed without disturbing the trap or substrate being sampled.

Water exchange pertaining to host attachment sites and stream preference in crayfish-associated branchiobdellids, Cambarincola fallax and Cambarincola ingens (Annelida: Clitellata)

Water balance profiles were constructed for adults of two branchiobdellid species (Cambarincola fallax and Cambarincola ingens) to examine how they are differentially adapted for a freshwater habitat on different crayfish hosts. Both exhibited a high (75%) body water content and high net transpiration rate, reflecting that they are hyperosmotic to freshwater and display a consistent strategy that emphasizes water loss. In contrast to C. ingens, C. fallax was 6× smaller in body size, lost water 2× faster, and had heightened activation energy (Ea) for water permeability. Thus, C. fallax relies on high net transpiration rate with a focus on elimination, whereas the larger C. ingens are modified for water retention and rely on their low activation energy to suppress the amount of water that enters the body. Neither species showed evidence of a critical transition temperature (CTT), as indicated by an uninterrupted Boltzmann temperature function of passive water loss rates. No influence on favoring water balance was apparent in relation to the crayfish host with regard to preferred attachment sites (subrostral or branchial chamber) or preference for occupying different regions (pool vs. riffle) of the stream. Thus, water balance strategies between the two species are complementary, reflecting trade-offs that adjust for body size to promote survival in similar freshwater habitats. The ability of C. ingens and C. fallax to survive with a low water content, down to nearly 1/2 their body mass, however, enables them to cope with the excess water by permitting a high rate of water loss.

Increased cave dwelling reduces the ability of cave crickets to resist dehydration

Differential strategies for maintaining water balance are reported for female adults of three cave crickets Hadenoecuscumberlandicus, H. opilionoides and H. jonesi, a species replacement series along the Cumberland Plateau in the southeastern United States. The distribution of H. cumberlandicus is much broader than the range of H. opilionoides, which is much smaller in body size, and that of H. jonesi, which possesses enhanced troglomorphic (cave dwelling) characteristics. Due to high net transpiration (water loss) rates and increased activation energies, H. jonesi and H. opilionoides are more susceptible to dehydration than H. cumberlandicus. To avoid dehydration, H. opilionoides and H. jonesi require more moisture than H. cumberlandicus to counter their higher rates of water loss. The heightened reliance on moisture likely indicates that the more troglomorphic H. jonesi and smaller H. opilionoides are required to spend more time in the moist cave region. Reliance on the cave for H. cumberlandicus is presumably less, allowing them to function in epigean habitats for longer periods and disperse to nearby caves, likely accounting for the more expansive distribution of this cricket. While in the cave habitat, cave crickets are exposed to water-saturated conditions, reducing the pressure of dehydration stress the longer a species remains in this wet environment. This reduced pressure leads to higher water loss rates as cave confinement increases. We conclude that increasing water loss rates associated with increasing troglomorphic adaptation in cave crickets is a side effect of extended residence in stable moist cave environments.

Diversity Patterns in the United States

Some 45,000+ caves are known from all 50 states and virtually each is populated with some form(s) of life, ranging from various microbes to a variety of small, rare, eyeless invertebrates, to considerably larger vertebrates. This article focuses primarily on troglobionts and stygobionts that are found mainly within nine geologically defined cave regions yet nonobligate species are not ignored. Currently at least 1138 species and subspecies are described and are assigned to approximately 239 genera and 112 families, with the exceedingly mobile troglobionts more than doubling the species richness values of stygobionts. Karst regions with the greatest total biodiversity are the Interior Lowlands, Appalachians, and the Edwards Plateau and Balcones Escarpment, although the aquatic and terrestrial animals do demonstrate somewhat different patterns. Of concern, the obligate cavernicoles make up slightly more than 50% of the imperiled fauna in the U.S. They, as well as the long-term impacts of White Nose Syndrome on bats as well as entire cave ecosystems, need immediate and concentrated investigation in order to protect and conserve karst habitats and their tenuous biodiversity.