Necturus beyeri beyeri Hecht 1958

Guyer, Craig, Murray, Christopher, Bart, Henry L., Crother, Brian I., Chabarria, Ryan E., Bailey, Mark A. & Dunn, Khorizon, 2020, Colour and size reveal hidden diversity of Necturus (Caudata: Proteidae) from the Gulf Coastal Plain of the United States, Journal of Natural History (J. Nat. Hist.) 54 (1 - 4), pp. 15-41 : 28-33

Necturus beyeri beyeri Hecht 1958

Necturus punctatus beyeri Brode, 1969 , in part Necturus (Parvurus) beyeri Dubois and Raffaëlli, 2012

Holotype. USNM 102674 ( Figure 11 (a,b)), an adult female from the Upper Calcasieu River at Oakdale (no exact locality given), Allen Parish, LA. This locality is within the range of the Western lineage of Chabarria et al. (2017).

Paratypes. USNM 102676 ; MCZ 17732, 17733 are listed in the original species description ( Viosca 1937) . To these we add representatives from within the ranges of the Mobile ( AUM

40150), Pearl ( MMNS 1288, LSUMZ 62933, SLU 744), and Pontchartrain ( LSUMZ 99424, SLU 6211, 6213) lineages ( Figure 11 (c–h))

Diagnosis. Membership of this species in the genus Necturus is demonstrated by retention of external gills in adults, presence of pigmented skin, and reduction of digits on hind limbs to four toes. Our concept of N. beyeri contains specimens of the Gulf Coastal Plain possessing a larva with numerous small white spots and lacking dark stripes ( Figure 2 (b)).

Comparisons. Juveniles of N. beyeri have small white punctations, an apparent autapomorphy that distinguishes this species from N. alabamensis and N. maculosus (larvae with two light dorsolateral stripes), N. lewisi (larvae with light middorsal stripe), and N. punctatus and the Apalachicola and Escambia lineages (larvae lacking stripes and white spots). Adults of N. beyeri typically possess large, bold, dark dorsal and lateral spots and retain the white punctations of the juveniles, creating a particularly colourful phenotype that distinguishes N. beyeri from N. punctatus and the Escambia and Apalachicola lineages. Along with N. maculosus , the Western lineage of N. beyeri has 6 pairs of telocentric chromosomes and an increased level of heterochromatin in the Y chromosome of males that differentiate these taxa from N. lewisi and N. punctatus (reduced heterochromatin, no telocentric chromosomes), and from the Apalachicola lineage (4 pairs of telocentric chromosomes, intermediate levels of heterochromatin in Y chromosome; Sessions and Wiley 1985). Additional sampling of the Escambia, Mobile, Pearl, and Pontchartrain lineages are needed to demonstrate the complete distribution of these character states.

Emended description of holotype. In preservation, the type specimen is 211 mm TOT, 144 mm SVL, and 67 mm TL; number of costal grooves is 16. The dorsal ground colour in preservation is slate brown with numerous white punctations across the entire body. The head has round dark-brown spots that are small anteriorly (about the same size as eye) and enlarged and bolder posteriorly (starting at insertion of gills). The head lacks a dark stripe from the nostril through the eye. The enlarged, bold, dark brown spots continue along the dorsum and sides of body to the tip of the tail. The ground colour of the venter is uniform tan, lacking the white punctations along the mid-venter but with such punctations gradually appearing ventrolaterally. The chin has small brown spots on skin covering the mandibles; spots are absent from the midventral skin of the chin. The venter has small brown spots midventrally, becoming enlarged laterally. The holotype has the following values for measured morphological features described above – ED: 2.9 mm; EL: 1.8 mm; GD: 4.7 mm; GEL: 20.6 mm; GL: 26.1 mm; HWE: 18.8 mm; HWG: 28.2 mm; POL: 21.1 mm; REW: 3.4 mm; SL: 8.1 mm; SRE: 10.4 mm; SW: 6.5 mm; WBW: 21.8 mm.

Variation. Necturus beyeri achieves relatively large adult sizes, with a maximum male size of 184.0 mm SVL (+ 68 mm TL) and a maximum female size of 177.0 mm SVL (+ 66 mm TL). Mean male size is 134.2 mm SVL (n = 53) and mean female size is 120.8 mm SVL (n = 94). In dorsal aspect, the modal adult lacks snout spotting (73% of specimens), has large dorsal (66% of specimens) and lateral (74% of specimens) spotting, and lacks chin (61% of specimens) and ventral (45% of specimens) spotting. The Pearl lineage diverges from this modal pattern in having a high percentage of snout (63%), chin (54%) and ventral (56%) spotting, and the Mobile lineage diverges from the mode in having a high percentage of small dorsal (54%) spotting and no chin (93%) or ventral (84%) spotting. The modal value for costal grooves is 17 (n = 147), with 35% of specimens possessing 16 grooves, and 2% possessing 18.

Adult males (n = 53) have the following mean (and range) values for measured morphological features – ED: 1.2 mm (0.1–5.3); EL: 1.8 mm (0.1–3.8); GD: 3.3 mm (0.9–6.2); GEL: 16.1 mm (10.4–2.2); GL: 21.1 mm (13.1–34.1); HWE: 12.6 (8.0–23.7); HWG: 19.5 (12.- 8–36.1); POL: 16.5 mm (10.6–26.6); REW: 2.4 mm (1.5–4.2); SL: 6.9 mm (3.2–12.0); SRE: 8.7 mm (4.9–14.7); SW: 5.2 mm (2.0–9.7); WBW: 19.0 (12.0–37.4).

Adult females (n = 94) have the following mean (and range) values for measured morphological features – ED: 0.8 mm (0.1–4.3); EL: 1.9 mm (0.1–4.3); GD: 2.9 mm (1.4–6.8); GEL: 14.3 mm (7.1–27.9); GL: 19.1 mm (10.8–34.4); HWE: 11.2 mm (11.2–20.9); HWG: 17.0 mm (8.9–34.5); POL: 14.6 mm (7.3–28.5); REW: 2.3 mm (1.2–4.3); SL: 5.7 mm (2.7–12.4); SRE: 7.6 mm (3.5–14.6); SW: 4.9 mm (2.0–10.2); WBW: 16.7 mm (8.0–36.8).

Etymology. The specific epithet is a patronym for George E. Beyer, a naturalist at Tulane University early in the 1900s who provided summaries of the herpetofauna of the state of Louisiana. The recommended English common name is Western Waterdog.

Distribution and natural history. Our re-description of Necturus beyeri restricts each lineage to the following drainages: Mobile lineage – Mobile (AL) to Biloxi (MS); Pearl lineage – Wolf (MS) to Pearl (LA); Pontchartrain lineage – Bayou Bonfouca to Blind River (LA); Western lineage – Calcasieu (LA) to West Fork of the San Jacinto River (TX; Figure 12 ).

No life history study has been performed on the Mobile lineage. Specimens are known from drainages entering Mobile Bay, where these salamanders can be found in dipnet samples of leaf beds. Farther north, we have sampled them from rocky reaches of the Tallapoosa River and from leaf packs under bridges of the Coosa River. The species is found in the same drainage as N. alabamensis , but with the Mobile lineage occupying slower-moving waters of the Coastal Plain, and N. alabamensis occupying swifter waters of the terminus of the Sand Mountain formation. The two species are both present in the Black Warrior River just east of Northport Lock and Dam, Yellow Creek at Lake Nichol Road crossing, and the North River near Samantha, all in Tuscaloosa County, AL ( Bart et al. 1997). These represent the only cases of sympatry involving Gulf Coast waterdogs. We examined no specimen that appeared to represent a morphological hybrid. Gunter and Brode (1964) collected specimens from the Biloxi and Pascagoula drainages, mostly on hooks baited with earthworms. Undercut banks or overhanging stumps and tree trunks associated with deep pools are key habitat features associated with this lineage ( Gunter and Brode 1964). Use of litter bags might increase detection of the Mobile lineage in occupied streams. From this sampling technique, Eurycea cirrigera , E. quadridigitata , and Desmognathus conanti are known associates ( Lamb and Qualls 2013).

Within the Pearl lineage, males have swollen cloacal openings and motile sperm in December and January, and detection of gravid females increases during November and December, when mating likely occurs ( Shoop 1965). Undercut banks or overhanging stumps and tree trunks associated with deep pools are key habitat features associated with detection of females and nests. Clutch size averages 57 eggs. Eggs are retained by females and clutches are deposited in April or May in deep water under rocks, logs or other sunken objects. Females attend the nests and can store sperm for at least six months after mating ( Sever and Bart 1996). Juveniles and subadults eat isopods, midges, and mayflies while adults feed on mayflies and caddisflies; prey consumption decreases in warm months when leaf litter used by detritivorous prey is decreased ( Bart and Holzenthal 1985). Specimens from coastal areas may occasionally be eaten by blue crabs ( Gunter and Brode 1964). The Pearl lineage often is infested with acanthocephalan parasites, for which waterdogs are a definitive host. These salamander hosts likely become infected via consumption of isopods, the intermediate host ( Bart and Holzenthal 1985).

No life history study has been performed on the Pontchartrain lineage. However, recent study of a dense population in Bayou Lacombe has documented the presence of Batrachochytrium dendrobatidis and B. salamandrivorans in populations of this lineage ( Glorioso et al. 2017).

Brenes and Ford (2006) provide the only published field study of the Western lineage of N. beyeri . They examined the species in Gilley and Hill Creeks of Smith County, TX where minnow traps placed along stream banks were used to capture waterdogs. The lineage was detected more frequently during November through January; none was detected during May, June, July, and August. This pattern was associated with a negative relationship between captures and water temperature, with no captures occurring when water temperatures exceeded 18°C. Reduction of activity at this temperature is similar to that reported for N. lewisi by Braswell and Ashton (1985), suggesting similar thermal tolerance within the entire genus. Recaptured individuals typically were found within 20 m of the initial capture, but distances of up to 230 m were observed between captures. Males retained in aquaria showed behaviours consistent with defence of underwater refugia during January and February, the presumed breeding period for free-ranging individuals. Animals captured in the field were associated with sandy- or gravel-bottom regions, typically with logjams.

Remarks. The collection locality of the holotype likely is where LA highway 10 crosses the Calcasieu River west of Oakdale (30.822529 -92.684595; WGS84).

Figures

Figure 2. Dorsal colour pattern of Necturus juveniles showing unspotted (a) and spotted (numerous white spots; b) character states.

Figure 11. Type specimen of N. beyeri (USNM 102674; Allen Parish, LA) dorsum (a) and venter (b; photos by Jenna L. Welch, Division of Amphibians and Reptiles, National Museum of Natural History, Smithsonian Institution; used with permission); paratype of Mobile lineage (AUM 40150, Covington County, AL) dorsum (c) and venter (d; photos by Craig Guyer); paratype of Pearl lineage (MMNS 1288, Saint Tammany Parish,LA) dorsum (e) and venter (f; photos by Craig Guyer); paratype of Pontchartrain lineage (LSUMZ 99424, Tangipahoa Parish, LA) dorsum (g) and venter (h; photos by Craig Guyer).

Figure 12. Distribution of localities of specimens assigned to N. beyeri. Open circle is approximate location of type specimen.