Tuesday, January 15, 2019

[Crustacea • 2019] Lacunicambarus chimera • A New Species of Burrowing Crayfish (Decapoda: Cambaridae) from Illinois, Indiana, Kentucky, and Tennessee

Lacunicambarus chimera Glon & Thoma,

in Glon, Thoma, Daly & Freudenstein, 2019. 
Crawzilla Crawdad  ||  DOI:  10.11646/zootaxa.4544.4.1
Photo by Guenter Schuster.

Lacunicambarus diogenes (Girard 1852) was, until recently, considered to be one of the most widely distributed North American crayfish species, occurring in 31 U.S. States and one Canadian province east of the North American Rocky Mountains. Glon et al. (2018) investigated this claim and found that L. diogenes sensu lato was actually a species complex. The authors redescribed L. diogenes and restricted its range to the Atlantic Coastal Plain and Piedmont ecoregions of eastern North America. In doing so, they also revealed the existence of several probable undescribed species of Lacunicambarus that were previously considered to be L. diogenes. Here, we use morphological and molecular techniques to distinguish and describe one of these species: Lacunicambarus chimera sp. nov., a large primary burrowing crayfish found in parts of the Lower Mississippi, Ohio, Tennessee and Upper Mississippi River Basins. Lacunicambarus chimera is morphologically similar to L. diogenes, from which it can be distinguished by the greater number of spines on the ventrolateral margin of its merus, its wider antennal scale terminating in a short spine, and the presence of a single longitudinal stripe on the dorsal side of its abdomen. We also provide an updated key to Lacunicambarus.

Keywords: Crustacea, burrowing crayfish, systematics, taxonomy, revision, North America, freshwater, Old Ohio River

FIGURE 6. Dorsal view of Form I holotypic male of Lacunicambarus chimera (OSUMC 10650).
Photo by Guenter Schuster.

Family Cambaridae Hobbs 1942 
Genus Lacunicambarus (Hobbs 1969) 

Lacunicambarus chimera Glon & Thoma sp. nov.

Cambarus obesus Forbes 1876:6 [in part]. 
Cambarus diogenes Hay 1895:478 [in part]. Ortmann 1905:123 [in part]. Rhoades 1944:111 [in part]. Eberly 1954:283 [in part]. Brown 1955:62 [in part]. Marlow 1960:229 [in part]. Page 1985:433 [in part]. Page & Mottesi 1995:23 [in part]. Taylor et al. 1996:29 [in part]. Simon 2001:104 [in part]. Taylor et al. 2007:382 [in part]. Taylor & Schuster 2004:80 [in part]. Taylor Schuster & Wylie 2015:66 [in part]. 
Cambarus diogenes diogenes Marlow 1960:233 [in part]. 
Cambarus (Lacunicambarus) diogenes diogenes Hobbs 1969:110 [in part]; 1974:20 [in part]. Bouchard 1972:56 [in part]; 1974:595 [in part]. 
Cambarus (Lacunicambarus) diogenes Hobbs 1989: 24 [in part]. Thoma et al. 2005:334 [in part]. Thoma & Armitage 2008:iii [in part]. 
Cambarus cf. diogenes Glon 2017:55.
 Lacunicambarus aff. diogenes Glon et al. 2018:604 [in part].

Diagnosis. Eyes pigmented, not reduced. Rostrum curved downwards in lateral view, margins converging, slightly thickened, without marginal spines or tubercles, lacking median carina, shallowly excavated. Acumen distinctly delimited basally by 45° angles. Cephalothorax cylindrical, with 3–10 (mean ± sd: 6 ± 1) small tubercles lining posterior margin of cervical groove. Anteroventral branchiostegal tubercles small, numbering 8–29 (mean ± sd: 18 ± 4). Suborbital angle acute. Postorbital ridges developed, lacking anterior spine or tubercle. Areola obliterated, constituting, in adults, 38–45% (mean ± sd: 42 ± 0 %) of entire length of cephalothorax. Antennal scale 2.41 to 3.35 (mean ± sd: 2.80 ± 0.18) times as long as wide, broadest distal to midlength, terminating in small spine, mesial margin forming straight edge. Dorsomesial margin of palm of chelae with 3 rows of tubercles, mesial-most row normally consisting of 6–10 (mean ± sd: 7 ± 1) probolos tubercles, running parallel to second row with 4–9 (mean ± sd: 6 ± 1) probolos tubercles, third row running diagonally from mesial base of palm to lateral dactyl articulation in the form of 5–8 (mean ± sd: 7 ± 1) subprobolos tubercles located in shallow dimples. No tufts of elongated setae at mesial base of fixed finger. Opposable margin of dactyl weakly concave at base. Ratio of dactyl length to palm length 1.78–2.49 (mean ± sd: 2.10 ± 0.16). Dorsomedian longitudinal ridges of dactyl and fixed finger of propodus weakly developed. Dorsolateral impression at base of propodus moderate. Ventral surface of chelae with 0–5 (mean ± sd: 2 ± 1) subpalmar tubercles. Mesial margin of dactyl with 12–33 (mean ± sd: 22 ± 4) prominent tubercles. Ventral surface of carpus with single spine on mesial articular rim, mesial margin with 4–10 (mean ± sd: 7 ± 1) spines of varying sizes. Merus spines numbering 2–9 (mean: 5 ± 2) on ventrolateral margin and 7–16 (mean ± sd: 11 ± 2) on ventromesial margin. Mesial ramus of uropod with distomedian spine not reaching caudal margin. Gonopods of Form I males contiguous at base, with moderately pronounced umbo near midlength of caudal surface; terminal elements consisting of 1) short, tapering, distally truncate central projection lacking subapical notch, shorter than mesial process, directed caudally at approximately 90°, reaching past margin of umbo, 2) mesial process with conical base tipped with protruding finger, directed caudally at approximately 90° and overreaching umbo by noticeable amount and 3) inconspicuous caudal knob sometimes present at caudolateral base of central projection. Hooks on ischium of third pereiopods only. Female with annulus ventralis subquadrangular or kiteshaped, approximately as long as wide, rather deeply embedded in sternum, flexible, with posterior half sclerotized and anterior half mildly pliable.

Ecological Notes. As mentioned above, Lacunicambarus chimera is a primary burrowing crayfish species. Like other Lacunicambarus species, L. chimera is commonly dug from burrows in fine-grained soils along the floodplains of streams and rivers and in roadside ditches. We have also collected this species in burrows on the banks of manmade ponds and in ditches that were lined with large stones. The chimneys at the mouths of L. chimera burrows are often large and conspicuous, attaining heights of 30 cm or more. These burrows, like those of other primary burrowing crayfishes, provide habitat for many other organisms (e.g., Creaser 1931; Pintor & Soluk 2006; Thoma & Armitage 2008). Glon & Thoma (2017) specifically documented the use of L. chimera burrows as brooding burrows by eastern cicada killer wasps in Pike County, Indiana. 

Little is known about the ecology of L. chimera in situ, but specimens which we have kept in laboratory aquariums have readily consumed a variety of aquarium fish foods, snails, earth worms, and leaf litter from streams, suggesting that this species is an opportunistic omnivore. These specimens were mostly active at night, when they foraged around their enclosures. During the day, they rested inside of artificial burrows made from PVC pipes, occasionally twitching their antennae in response to stimuli. They did not appear to be particularly aggressive, compared to other crayfish species.

Crayfish Associates. We collected the following primary and secondary-burrowing crayfishes from burrows at sites where we found Lacunicambarus chimera: Creaserinus fodiens (Cottle 1863), C. hortoni (Hobbs & Fitzpatrick 1970), Faxonius immunis (Hagen 1870), L. ludovicianus, L. polychromatus, L. aff. polychromatus, Procambarus acutus (Girard 1852), P. clarkii (Girard 1852), P. gracilis (Bundy in Forbes 1876) and P. viaeviridis (Faxon 1914). While sampling for L. chimera, we focused primarily on sampling for burrowing crayfishes and therefore do not have records of the tertiary-burrowing crayfishes that undoubtedly inhabit open water adjacent to L. chimera burrows. 

Etymology. Our choice of the species epithet “chimera” stems from our first encounter with this species. The first specimens that we caught were freshly molted young adults (approximately 30 mm CL). These specimens bore a bright longitudinal gladiate stripe reminiscent of the stripe in L. ludovicianus, L. miltus, and some populations of L. polychromatus. The bright colors on these specimens were similar to those found in L. polychromatus, and the general shape of these specimens was reminiscent of L. diogenes. These features made L. chimera appear to be a chimera of multiple Lacunicambarus species. To honor the nickname given to this species when it was first discovered by Ray Jezerinac and Whitney Stocker, and also as a reference to its impressive size, we suggest the common name “Crawzilla Crawdad.” 

Mael G. Glon, Roger F. Thoma, Marymegan Daly and John V. Freudenstein. 2019.  Lacunicambarus chimera: A New Species of Burrowing Crayfish (Decapoda: Cambaridae) from Illinois, Indiana, Kentucky, and Tennessee. Zootaxa. 4544(4); 451–478.  DOI:  10.11646/zootaxa.4544.4.1