Table 1.
Tobrilidae (order Triplonchida) of North America (Holovachov and Shoshin, 2014)
| Sub-family | Tribe | Species |
|---|---|---|
| Neotobrilinae Tsalolikhin, 2001 | Neotobrilini Tsalolikhin, 1981 | Neotobrilus longus (Leidy, 1852) Tsalolikhin, 1981 |
| Neotobrilinae Tsalolikhin, 2001 | Neotobrilini Tsalolikhin, 1981 | Neotobrilus nicsmolae Abebe, Ferebee, Taylor, Mundo-Ocampo, Mekete & De Ley, 2013 |
| Neotobrilinae Tsalolikhin, 2001 | Neotobrilini Tsalolikhin, 1981 | Neotobrilus filipjevi (Ebsary, 1982) Tsalolikhin and Shoshin, 2009 |
| Neotobrilinae Tsalolikhin, 2001 | Neotobrilini Tsalolikhin, 1981 | Neotobrilus hopei (Loof and Riemann, 1976) Tsalolikhin, 1981 |
| Neotobrilinae Tsalolikhin, 2001 | Neotobrilini Tsalolikhin, 1981 | Semitobrilus pellucidus Bastian, 1865 |
| Neotobrilinae Tsalolikhin, 2001 | Neotobrilini Tsalolikhin, 1981 | Semitobrilus ebsaryi Tsalolikhin, 2000 |
| Neotobrilinae Tsalolikhin, 2001 | Epitobrilini Tsalolikhin, 2001 | Epitobrilus sablensis (Ebsary, 1982) Tsalolikhin, 2001 |
| Tobrilinae Tsalolikhin, 2001 | Tobrilini Filipjev, 1918 | Tobrilus gracilis Bastian, 1865 |
| Tobrilinae Tsalolikhin, 2001 | Tobrilini Filipjev, 1918 | Tobrilus aberrans (Schneider, 1925) Andrassy, 1959 |
| Tobrilinae Tsalolikhin, 2001 | Tobrilini Filipjev, 1918 | Tobrilus affinis Gagarin, 1996 |
| Tobrilinae Tsalolikhin, 2001 | Tobrilini Filipjev, 1918 | Eutobrilus graciliformis (Altherr and Delamare Deboutteville, 1972) Tsalolikhin, 1981 |
| Tobrilinae Tsalolikhin, 2001 | Tobrilini Filipjev, 1918 | Eutobrilus steineri (Micoletzky, 1925) Zullini, 2006 |
Table 2.
Tobrilidae specimen information by Nematode Identification (NID) number, and molecular grouping by COI marker.
| County in NE | Site | Latitude; Longitude | Marker- 18S | Marker- COI | ||||
|---|---|---|---|---|---|---|---|---|
| 7157 | NA | Neotobrilus sp. | Female | Lancaster | Lincoln landfill | 40.871597; −96.654336 | PP854262 | |
| 11092 | NA | Neotobrilus sp. | Juvenile | Garden | Kokjohn Lake | 41.78259; −102.52226 | PP854263 | |
| 11093 | 2 | Neotobrilus sp. | Female | Garden | Kokjohn Lake | 41.78259; −102.52226 | PP855138 | |
| 11096 | NA | Neotobrilus sp. | Juvenile | Garden | Kokjohn Lake | 41.78259; −102.52226 | PP854264 | |
| 11097 | NA | Neotobrilus sp. | Juvenile | Garden | Kokjohn Lake | 41.78259; −102.52226 | PP854265 | |
| 11105 | NA | Neotobrilinae | Intersex | Garden | Gimlet Lake | 41.758702; −102.438185 | PP854246 | |
| 11890 | 2 | Neotobrilus sp. | Female | Garden | Bean Lake | 41.77776; −102.53009 | PP855143 | |
| 12093 | Singleton 1 | Neotobrilinae | Female | Garden | Border Lake | 41.79170; −102.53385 | PP854247 | PP855091 |
| 12103 | NA | Neotobrilinae | Female | Garden | Border Lake | 41.79170; −102.53385 | PP854248 | |
| 12127 | 1 | Tobrilus sp. | Female | Garden | Gimlet Lake | 41.75911; −102.43817 | PP854219 | PP855098 |
| 12129 | NA | Tobrilus sp. | Female | Garden | Gimlet Lake | 41.759109; −102.438171 | PP854227 | |
| 12138 | 1 | Tobrilus sp. | Female | Garden | Gimlet Lake | 41.75911; −102.43817 | PP854220 | PP855097 |
| 12141 | NA | Neotobrilus sp. | Female | Garden | Kokjohn Lake | 41.782081; −102.522884 | PP854266 | |
| 12144 | 2 | Neotobrilus sp. | Male | Garden | Kokjohn Lake | 41.78208; −102.52288 | PP854267 | PP855137 |
| 12168 | NA | Tobrilus sp. | Female | Garden | Island Lake | 41.733602; −102.410585 | PP854218 | |
| 12193 | 3 | Brevitobrilus sp. | Male | Garden | Island Lake | 41.73466; −102.41114 | PP854261 | PP855127 |
| 12194 | NA | Brevitobrilus sp. | Female | Garden | Island Lake | 41.734664; −102.411136 | PP854260 | |
| 12195 | NA | Tobrilus sp. | Female | Garden | Island Lake | 41.734664; −102.411136 | PP854208 | |
| 12204 | Singleton 2 | Neotobrilinae | Juvenile | Garden | Island Lake | 41.73466; −102.41114 | PP854243 | PP855101 |
| 12397 | NA | Brevitobrilus sp. | Male | Garden | Island Lake | 41.73481; −102.41120 | PP854259 | |
| 12400 | NA | Tobrilinae | Female | Garden | Island Lake | 41.73481; −102.41120 | PP854244 | |
| 12406 | 3 | Brevitobrilus sp. | Female | Garden | Island Lake | 41.73481; −102.41120 | PP854258 | PP855126 |
| 12408 | 3 | Brevitobrilus sp. | Female | Garden | Island Lake | 41.73481; −102.41120 | PP854257 | PP855124 |
| 12417 | 3 | Brevitobrilus sp. | Male | Garden | Island Lake | 41.73481; −102.41120 | PP854255 | PP855125 |
| 12420 | NA | Brevitobrilus sp. | Female | Garden | Island Lake | 41.73481; −102.41120 | PP854256 | |
| 12422 | NA | Neotobrilus sp. | Female | Garden | Border Lake | 41.79230; −102.53349 | PP854268 | |
| 12423 | NA | Neotobrilus sp. | Juvenile | Garden | Border Lake | 41.79230; −102.53349 | PP854269 | |
| 12424 | NA | Neotobrilus sp. | Female | Garden | Border Lake | 41.79230; −102.53349 | PP854270 | |
| 12425 | NA | Neotobrilus sp. | Juvenile | Garden | Border Lake | 41.79230; −102.53349 | PP854271 | |
| 12426 | 2 | Neotobrilus sp. | Juvenile | Garden | Border Lake | 41.79230; −102.53349 | PP854272 | PP855128 |
| 12427 | NA | Neotobrilus sp. | Male | Garden | Border Lake | 41.79230; −102.53349 | PP854273 | |
| 12428 | NA | Neotobrilus sp. | Juvenile | Garden | Border Lake | 41.79230; −102.53349 | PP854274 | |
| 12429 | NA | Neotobrilus sp. | Male | Garden | Border Lake | 41.79230; −102.53349 | PP854275 | |
| 12431 | NA | Neotobrilus sp. | Juvenile | Garden | Border Lake | 41.79230; −102.53349 | PP854276 | |
| 12432 | NA | Neotobrilus sp. | Juvenile | Garden | Border Lake | 41.79230; −102.53349 | PP854277 | |
| 12433 | NA | Neotobrilus sp. | Juvenile | Garden | Border Lake | 41.79230; −102.53349 | PP854278 | |
| 12434 | NA | Neotobrilus sp. | Juvenile | Garden | Border Lake | 41.79230; −102.53349 | PP854279 | |
| 12435 | NA | Neotobrilus sp. | Juvenile | Garden | Border Lake | 41.79230; −102.53349 | PP854280 | |
| 12442 | 2 | Neotobrilus sp. | Male | Garden | Border Lake | 41.79230; −102.53349 | PP854281 | PP855130 |
| 12444 | NA | Neotobrilus sp. | Male | Garden | Border Lake | 41.79230; −102.53349 | PP854282 | |
| 12522 | Singleton 3 | Neotobrilinae | Juvenile | Garden | Border Lake | 41.757717; −102.434 | PP854283 | PP855120 |
| 12523 | 2 | Neotobrilus sp. | Female | Garden | Border Lake | 41.757717; −102.434 | PP854284 | PP855136 |
| 12524 | 2 | Neotobrilus sp. | Juvenile | Garden | Border Lake | 41.757717; −102.434 | PP855133 | |
| 12525 | 2 | Neotobrilus sp. | Juvenile | Garden | Border Lake | 41.757717; −102.434 | PP854285 | PP855131 |
| 12528 | 2 | Neotobrilus sp. | Female | Garden | Border Lake | 41.79212; −102.53420 | PP854286 | PP855134 |
| 12533 | 2 | Neotobrilus sp. | Male | Garden | Border Lake | 41.79212; −102.53420 | PP854291 | PP855140 |
| 12537 | 2 | Neotobrilus sp. | Male | Garden | Border Lake | 41.79212; −102.53420 | PP854292 | PP855139 |
| 12538 | 2 | Neotobrilus sp. | Female | Garden | Border Lake | 41.79212; −102.53420 | PP854251 | PP855141 |
| 12539 | 2 | Neotobrilus sp. | Female | Garden | Border Lake | 41.79212; −102.53420 | PP854287 | PP855142 |
| 12540 | 2 | Neotobrilus sp. | Female | Garden | Border Lake | 41.79212; −102.53420 | PP854288 | PP855135 |
| 12554 | 4 | Neotobrilinae | Male | Garden | Gimlet Lake | 41.75543; −102.43447 | PP855086 | |
| 12556 | 1 | Tobrilinae | Female | Garden | Gimlet Lake | 41.75543; −102.43447 | PP855099 | |
| 12559 | 4 | Semitobrilus sp. | Juvenile | Garden | Gimlet Lake | 41.75543; −102.43447 | PP855059 | |
| 12561 | 4 | Semitobrilus sp. | Juvenile | Garden | Gimlet Lake | 41.75632; −102.43877 | PP855083 | |
| 12563 | 2 | Neotobrilus sp. | Juvenile | Garden | Bean Lake | 41.77068; −102.52883 | PP854250 | PP855144 |
| 12574 | 4 | Semitobrilus sp. | Female | Garden | Bean Lake | 41.77068; −102.52883 | PP854289 | PP855082 |
| 12575 | 2 | Neotobrilus sp. | Female | Garden | Bean Lake | 41.77068; −102.52883 | PP854254 | PP855132 |
| 12577 | NA | Neotobrilus sp. | Juvenile | Garden | Bean Lake | 41.77068; −102.52883 | PP854290 | |
| 12582 | 2 | Neotobrilus sp. | Immature Female | Garden | Bean Lake | 41.77068; −102.52883 | PP855129 | |
| 12586 | 1 | Tobrilus sp. | Female | Garden | Gimlet Lake | 41.75792; −102.43418 | PP854228 | PP855092 |
| 12587 | 1 | Tobrilus sp. | Male | Garden | Gimlet Lake | 41.75792; −102.43418 | PP854221 | PP855096 |
| 12588 | 1 | Tobrilus sp. | Male | Garden | Gimlet Lake | 41.75792; −102.43418 | PP854217 | PP855095 |
| 12591 | 1 | Tobrilus sp. | Female | Garden | Gimlet Lake | 41.75792; −102.43418 | PP854229 | PP855093 |
| 12592 | 4 | Semitobrilus sp. | Male | Garden | Gimlet Lake | 41.75792; −102.43418 | PP855081 | |
| 12593 | 4 | Semitobrilus sp. | Female | Garden | Gimlet Lake | 41.75792; −102.43418 | PP854234 | PP855084 |
| 12595 | 4 | Semitobrilus sp. | Male | Garden | Gimlet Lake | 41.75792; −102.43418 | PP854206 | PP855080 |
| 12596 | 4 | Semitobrilus sp. | Male | Garden | Gimlet Lake | 41.75792; −102.43418 | PP854207 | PP855079 |
| 12597 | NA | Semitobrilus sp. | Female | Garden | Gimlet Lake | 41.75792; −102.43418 | PP854235 | |
| 12598 | NA | Semitobrilus sp. | Male | Garden | Gimlet Lake | 41.75792; −102.43418 | PP854241 | |
| 12599 | 4 | Semitobrilus sp. | Male | Garden | Gimlet Lake | 41.75792; −102.43418 | PP855078 | |
| 12601 | 4 | Semitobrilus sp. | Male | Garden | Gimlet Lake | 41.75792; −102.43418 | PP855085 | |
| 12602 | 4 | Semitobrilus sp. | Female | Garden | Gimlet Lake | 41.75792; −102.43418 | PP855077 | |
| 12605 | 4 | Semitobrilus sp. | Female | Garden | Gimlet Lake | 41.75792; −102.43418 | PP854249 | PP855076 |
| 12606 | 1 | Tobrilus sp. | Juvenile | Garden | Gimlet Lake | 41.75792; −102.43418 | PP855094 | |
| 12607 | 1 | Tobrilus sp. | Female | Garden | Gimlet Lake | 41.75792; −102.43418 | PP854222 | PP855100 |
| 12613 | 4 | Semitobrilus sp. | Juvenile | Garden | Island Lake | 41.73257; −102.40362 | PP854240 | PP855075 |
| 12614 | 4 | Semitobrilus sp. | Juvenile | Garden | Island Lake | 41.73257; −102.40362 | PP854236 | PP855074 |
| 12615 | 4 | Semitobrilus sp. | Juvenile | Garden | Island Lake | 41.73257; −102.40362 | PP854237 | PP855073 |
| 12616 | 4 | Semitobrilus sp. | Juvenile | Garden | Island Lake | 41.73257; −102.40362 | PP854238 | PP855089 |
| 12617 | 4 | Semitobrilus sp. | Juvenile | Garden | Island Lake | 41.73257; −102.40362 | PP854242 | PP855072 |
| 12622 | NA | Neotobrilinae | Juvenile | Garden | Island Lake | 41.73257; −102.40362 | PP854245 | |
| 12623 | NA | Semitobrilus sp. | Juvenile | Garden | Island Lake | 41.73257; −102.40362 | PP854239 | |
| 12624 | 4 | Semitobrilus sp. | Juvenile | Garden | Island Lake | 41.73257; −102.40362 | PP855071 | |
| 12765 | 4 | Semitobrilus sp. | Juvenile | Garden | Island Lake | 41.73849; −102.40540 | PP855070 | |
| 12769 | 4 | Semitobrilus sp. | Female | Garden | Island Lake | 41.73849; −102.40540 | PP855069 | |
| 12770 | 4 | Semitobrilus sp. | Immature Female | Garden | Island Lake | 41.73849; −102.40540 | PP855068 | |
| 12773 | 4 | Semitobrilus sp. | Immature Female | Garden | Island Lake | 41.73849; −102.40540 | PP855067 | |
| 12774 | 4 | Semitobrilus sp. | Female | Garden | Island Lake | 41.73849; −102.40540 | PP855087 | |
| 12775 | 4 | Semitobrilus sp. | Male | Garden | Island Lake | 41.73849; −102.40540 | PP855066 | |
| 12776 | 4 | Semitobrilus sp. | Juvenile | Garden | Island Lake | 41.73849; −102.40540 | PP855065 | |
| 12778 | 4 | Semitobrilus sp. | Female | Garden | Island Lake | 41.73849; −102.40540 | PP855090 | |
| 12779 | 4 | Semitobrilus sp. | Female | Garden | Island Lake | 41.73849; −102.40540 | PP855064 | |
| 12780 | 4 | Semitobrilus sp. | Female | Garden | Island Lake | 41.73849; −102.40540 | PP855063 | |
| 12782 | 4 | Semitobrilus sp. | Female | Garden | Island Lake | 41.73849; −102.40540 | PP855062 | |
| 12786 | 4 | Semitobrilus sp. | Immature Female | Garden | Island Lake | 41.73849; −102.40540 | PP855061 | |
| 12827 | 4 | Semitobrilus sp. | Female | Garden | Gimlet Lake | 41.75767; −102.43452 | PP855060 | |
| 12836 | 4 | Semitobrilus sp. | Female | Garden | Gimlet Lake | 41.75767; −102.43452 | PP855088 | |
| 13994 | 6 | Neotobrilus sp. | Female | Saunders | Johnson Creek 1 | 41.23383; −96.46355 | PP855121 | |
| 14003 | 6 | Neotobrilus sp. | Male | Saunders | Johnson Creek 1 | 41.23383; −96.46355 | PP854252 | PP855122 |
| 14023 | 6 | Neotobrilus sp. | Female | Saunders | Johnson Creek 2 | 41.204850; −96.44180 | PP854253 | PP855123 |
| 14034 | 5 | Tobrilus sp. | Female | Saunders | Johnson Creek 3 | 41.19345; −96.42583 | PP854216 | PP855114 |
| 14036 | 5 | Tobrilus sp. | Male | Saunders | Johnson Creek 3 | 41.19345; −96.42583 | PP854230 | PP855109 |
| 14041 | 5 | Tobrilus sp. | Male | Saunders | Johnson Creek 3 | 41.19345; −96.42583 | PP854223 | PP855108 |
| 14042 | 5 | Tobrilus sp. | Female | Saunders | Johnson Creek 3 | 41.19345; −96.42583 | PP855112 | |
| 14044 | 5 | Tobrilus sp. | Male | Saunders | Johnson Creek 3 | 41.19345; −96.42583 | PP854215 | PP855110 |
| 14045 | 5 | Tobrilus sp. | Female | Saunders | Johnson Creek 3 | 41.19345; −96.42583 | PP854231 | PP855107 |
| 14047 | 5 | Tobrilus sp. | Female | Saunders | Johnson Creek 3 | 41.19345; −96.42583 | PP854224 | PP855115 |
| 14053 | 5 | Tobrilus sp. | Female | Saunders | Johnson Creek 3 | 41.19345; −96.42583 | PP854214 | PP855106 |
| 14054 | 5 | Tobrilus sp. | Male | Saunders | Johnson Creek 3 | 41.19345; −96.42583 | PP854232 | PP855105 |
| 14059 | 5 | Tobrilus sp. | Male | Saunders | Johnson Creek 4 | 41.19048; −96.42437 | PP854225 | PP855116 |
| 14061 | 5 | Tobrilus sp. | Male | Saunders | Johnson Creek 4 | 41.19048; −96.42437 | PP854213 | PP855117 |
| 14063 | 5 | Tobrilus sp. | Female | Saunders | Johnson Creek 4 | 41.19048; −96.42437 | PP854233 | PP855102 |
| 14065 | 5 | Tobrilus sp. | Female | Saunders | Johnson Creek 4 | 41.19048; −96.42437 | PP854226 | PP855103 |
| 14067 | 5 | Tobrilus sp. | Female | Saunders | Johnson Creek 4 | 41.19048; −96.42437 | PP854209 | PP855104 |
| 14071 | 5 | Tobrilus sp. | Male | Saunders | Johnson Creek 4 | 41.19048; −96.42437 | PP855113 | |
| 14072 | 5 | Tobrilus sp. | Male | Saunders | Johnson Creek 4 | 41.19048; −96.42437 | PP854212 | PP855118 |
| 14080 | 5 | Tobrilus sp. | Male | Saunders | Johnson Creek 5 | 41.17043; −96.40668 | PP854211 | PP855111 |
| 14081 | 5 | Tobrilus sp. | Female | Saunders | Johnson Creek 5 | 41.17043; −96.40668 | PP854210 | PP855119 |
Figure 1.
Map of Nebraska with the Sandhills region outlined. Area of research on the alkaline lakes in this region is indicated in an enlarged map inset. A second enlarged map inset shows the area of research in eastern Nebraska on an agrichemical contamination site. Red circles indicate the location of sample collections from the stream sediment.
Table 3a.
Standard morphological measurements, abbreviations, and definitions.
| Gender | Character | Description (all measurements in μm) | |
|---|---|---|---|
| Females | Vulva | Length from anterior to vulva | |
| Females | Males | L | Overall body length |
| Females | Males | Tail | Portion of body from anus or cloaca to posterior terminus |
| Females | Males | a | Body length/greatest body diameter |
| Females | Males | b | Body length/distance from anterior to pharyngo-intestinal valve |
| Females | Males | c | Body length/tail Length |
| Females | Males | c′ | Tail length/body diameter at anus or cloaca |
| Females | V | % Vulva position/body length | |
| Females | VA/T | Distance from vulva to anus/tail length | |
| Females | Males | Tail % | % Tail length/body length |
| Females | Males | C set/lrw | Cephalic seta length/lip region width |
| Females | Males | L set/lrw | Labial seta length/lip region width |
| Females | Males | StomaL | Length of sclerotized portion of stoma (buccal cavity) |
| Females | Males | Dist | Distance between teeth |
| Males | Spic | Spicule length | |
| Males | Spic/L | % Spicule length/body length | |
| Males | Gub | Gubernaculum length | |
| Males | Cl-III | Distance between supplement III and cloaca | |
| Males | SR | Length of supplement row (I–VI) | |
| Males | SR/L | % Length of supplement row/total body length | |
Figure 2.
llustration of selected characters in Tobrilidae. A) Female heads (NID 12586, 13994) with teeth and tooth distance annotated. B) Female heads with differing tooth pocket arrangements. C) Male (NID 12533) posterior illustrating the numbering of supplements from the cloacal opening forward, with I designating the most posterior supplement and VII the most anterior.
Figure 3.
A maximum likelihood COI phylogenetic tree of 90 Nebraska specimens and 21 GenBank accessions. Highlighting in labels indicates lake pH. Green equals neutral, orange equals pH >8.5. Blue boxes around labels identify three specimens that display incongruence between COI and 18S trees. Nematode Identification numbers (NID) start with the prefix N followed by the number of the specimen.
Table 3b.
Soil sample chemistry analyses, abbreviations, and definitions.
| Parameter | Methodology |
|---|---|
| Soil pH | Soil pH-soil pH 1:1 (1 volume of soil in 1 volume of water) |
| % OM | % Organic Matter-Measure of organic matter in soil by % LOI |
| NO3 | Nitrate ppm-Nitrate, KCl extractable |
| K | Potassium ppm-extracted by ammonium acetate |
| SO4 | Sulfate ppm-extracted by Mehlich S-III |
| Zn | Zinc ppm-DTPA (diethylenetriaminepentaacetic acid) micronutrient extraction method |
| Fe | Iron ppm-DTPA (diethylenetriaminepentaacetic acid) micronutrient extraction method |
| Mn | Manganese ppm-DTPA (diethylenetriaminepentaacetic acid) micronutrient extraction method |
| Cu | Copper ppm-DTPA (diethylenetriaminepentaacetic acid) micronutrient extraction method |
| Ca | Calcium ppm-extracted by ammonium acetate |
| Mg | Magnesium ppm-extracted by ammonium acetate |
| Na | Sodium ppm-extracted by ammonium acetate |
| B | Boron ppm-hot water extracted |
| CEC | CEC (meq/100g)-Cation Exchange Capacity: Sum (in meq) of the 4 cations(K+Ca+Mg+Na+)/100g soil |
| % H | %H Sat-%Base Saturation |
| % K | %K Sat-%Base Saturation |
| % Ca | %Ca Sat-%Base Saturation |
| % Mg | %Mg Sat-%Base Saturation |
| % Na | %Na Sat-%Base Saturation |
| Cl- | Chloride ppm-Chloride |
| P | Phosphorus ppm-Phosphorus, extracted by Mehlich P-III |
Table 4.
Within- and between-group mean distances of 9 tobrilid COI groups. Within-group distance is shown in bold type.
| Group 4 | Group 1 | Group 5 | Group 6 | Group 3 | Group 2 | Group 7 | Group 9 | Group 8 | |
|---|---|---|---|---|---|---|---|---|---|
| Group 4 | 0.000639 | ||||||||
| Group 1 | 0.159155 | 0.000651 | |||||||
| Group 5 | 0.165664 | 0.060499 | 0.002543 | ||||||
| Group 6 | 0.157512 | 0.126478 | 0.111416 | 0.001826 | |||||
| Group 3 | 0.158968 | 0.123860 | 0.124103 | 0.096937 | 0 | ||||
| Group 2 | 0.164354 | 0.131401 | 0.133042 | 0.094518 | 0.093262 | 0.005378 | |||
| Group 7 | 0.141845 | 0.141270 | 0.126408 | 0.131963 | 0.140716 | 0.151729 | 0.027397 | ||
| Group 9 | 0.141204 | 0.110544 | 0.107067 | 0.117939 | 0.117579 | 0.124228 | 0.130528 | 0.007567 | |
| Group 8 | 0.173377 | 0.128000 | 0.145053 | 0.158447 | 0.133743 | 0.144301 | 0.183562 | 0.117613 | 0.004566 |
Figure 4.
Comparison of the heads of specimens from each of the six Haplotype Groups, with their identification number and lake from which they were collected. Stoma shape, pockets, and tooth distance are featured. Blue box indicates incongruent specimen between COI and 18S trees.
Figure 5.
Comparison of male spicules and supplements from haplotype groups one through six. The nematode identification (NID) number and collection location are shown for each. Groups 1, 4, and 5 have supplements that do not conspicuously protrude from the cuticle surface. Groups 2, 3, and 6 have protruding supplements. Group 4 has notably long spicules compared to other groups. The blue box around the label for NID 12595 denotes a specimen incongruent for COI and 18S trees.
Figure 6.
Scanning electron micrographs of the male posterior region showing the intersupplementary structures known as micropapillae. A, B) NID 4829 from Border Lake, micropapillae in ventral view appear as four ridges between supplements; C) NID 4841 from Border Lake, micropapillae in lateral view appear as small bumps or papillae.
Figure 7.
Scanning electron micrographs of Group 4 male spicules, all from Gimlet Lake, displaying possible pores at the tip. A) NID 4913 tail and close-up of spicules; B) NID 4926 posterior and close-up of spicules; C) NID 4899 spicules.
Figure 8.
Comparison of the musculature associated with the vaginal canal in haplotype groups one through six. The Tobrilinae, Groups 1 and 5, display weak or poorly developed vaginal musculature. Group 3 appears to have moderately developed musculature, and Groups 2, 4, and 6 are all characterized by strongly developed muscles arranged in a multi-layered, bulb-like configuration. Blue box around NID 12574 indicates incongruent specimen with respect to the COI and 18S trees and has a strong, bulb-like musculature characteristic of Group 2.
Figure 9.
Scanning electron micrographs of the head, amphid and cephalic setae of selected specimens from alkaline lakes in the Nebraska Sandhills. Amphid shapes were categorized as tiny, oval or slit-like. Slit-like amphids were positioned closest to cephalic setae. Inner labial setae are notably shorter than the outer labial and cephalic setae, which are of similar lengths.
Figure 10.
Entire body images of female and male specimens from each of the six haplotype groups. The nematode identification (NID) number and collection location are shown for each. Blue box indicates incongruent specimen.
Figure 11.
Comparison of female tails from each of the six haplotype groups. The nematode identification (NID) number and collection location is shown for each. Blue box in Group four indicates specimen, NID 12574, considered incongruous between the COI and 18S phylogenies, and which displays differing morphology from the other two individuals.
Table 5.
Comparisons of selected morphological characteristics of the main groups (mean ± standard deviation with range of values)
| Group 1 Tobrilus Female (n=7) | Group 2 Neotobrilus Female (n=9) | Group 3 Brevitobrilus Female (n=4) | Group 4 Semitobrilus Female (n=4) | Group 5 Tobrilus Female (n=17) | Group 6 Neotobrilus Female (n=3) | |
|---|---|---|---|---|---|---|
| L | 2366.7 ± 236.6 (2073–2863) | 1999.3 ± 301.7 (1449–2341) | 2032.8 ± 197.9 (1727–2229) | 2729.6 ± 192.1 (2415–2937) | 2079.3 ± 209.8 (1769–2739) | 1225.4 ± 157.7 (1087–1446) |
| a | 31.2 ± 2.1 (29.7–36.1) | 31.5 ± 5.9 (21.8–41.1) | 35.8 ± 2.3 (32.8–39.0) | 33.7 ± 1.1 (32.4–35.2) | 29.7 ± 2.4 (24.1–33.5) | 26.4 ± 1.9 (24.2–28.8) |
| b | 5.6 ± 0.2 (5.4–6.0) | 5.4 ± 0.5 (4.1–6.0) | 6.4 ± 0.3 (6.1–6.7) | 6.7 ± 0.2 (6.4–6.9) | 5.5 ± 0.4 (4.5–6.0) | 4.9 ± 0.2 (4.6–5.2) |
| c | 8.9 ± 0.7 (7.4–9.6) | 10.6 ±1.0 (8.4–11.6) | 7.9 ± 0.4 (7.1–8.2) | 7.1 ± 0.2 (6.9–7.3) | 10.0 ± 2.5 (8.5–19.8) | 9.5 ± 1.8 (7.7–12.0) |
| c′ | 6.8 ± 0.7 (6.0–8.0) | 4.6 ±0.4 (4.2–5.3) | 7.4 ± 0.5 (6.9–8.1) | 7.8 ± 0.4 (7.2–8.2) | 5.8 ± 0.8 (2.8–6.8) | 5.2 ± 1.2 (3.4–6.1) |
| V | 44.7% ± 2.4% (42.0%–48.5%) | 46.1% ± 3.8% (43.6%–56.4%) | 41.0% ± 1.2% (39.6%–43.0%) | 48.7% ± 1.6% (46.3%–50.6%) | 42.5% ± 3.9% (32.4%–47.1%) | 42.1% ± 1.2% (41.2%–43.8%) |
| Tail | 265.1 ± 19.3 (239–297) | 188.5 ± 17.6 (154 –210) | 257.8 ± 13.5 (242 –275) | 385.7 ± 23.9 (350–414) | 216.2 ± 34.4 (97–264) | 131.4 ± 11.7 (121–148) |
| V-A/T | 3.9 ± 0.4 (3.2–4.4) | 4.7 ± 0.8 (2.7–5.5) | 3.6 ± 0.2 (3.3–3.8) | 2.6 ± 0.1 (2.5–2.8) | 4.7 ± 1.3 (3.7–9.7) | 4.5 ± 1.1 (3.5–6.0) |
| LRW | 30.7 ± 2.7 (28–36) | 28.9 ± 2.9 (24–34) | 24.3 ± 2.6 (21–28) | 28.9 ± 1.7 (27–31) | 26.8 ± 2.9 (22–31) | 15.4 ± 1.3 (14–17) |
| Set L | 5.9 ± 2.4 (2–8) | 6.1 ± 2.3 (4–10) | 4.6 ± 1.1 (3–5) | 8.2 ± 0.7 (8–9) | 6.7 ± 1.2 (5–8) | 4.5 ± 1.2 (3–5) |
| Set L/LRW | 19.5% ± 8.4% (4.9%–28.9%) | 21.6% ± 9.3% (13.8%–38.9%) | 19.0% ± 5.1% (12.5%–25.0%) | 28.4% ± 2.1% (25.2%–30.9%) | 25.0% ± 3.6% (17.6%–31.8%) | 28.7% ± 6.8% (19.6%–36.1%) |
| Stoma L | 12.3 ± 1.2 (10–14) | 9.7 ± 1.2 (8–12) | 8.5 ± 0.5 (8–9) | 7.5 ± 1.5 (6–10) | 13.1 ± 1.2 (10–15) | 8.3 ± 0.7 (7–9) |
| Ant tooth pos | 17.8 ± 4.8 (9–23) | 20.3 ± 4.7 (15–29) | 19.9 ± 4.9 (15–26) | 17.2 ± 2.3 (15–20) | 20.9 ± 1.7 (18–24) | 11.6 ± 1.4 (10–13) |
| Post tooth pos | 24.2 ± 2.4 (19–27) | 32.7 ± 3.8 (25–39) | 29.1 ± 4.6 (24–35) | 24.0 ± 4.9 (19–32) | 23.0 ± 2.2 (20–27) | 22.7 ± 2.3 (19–24) |
| Tooth dist | 6.3 ± 3.8 (2–13) | 12.4 ± 2.7 (8–16) | 11.3 ± 1.2 (10–12) | 6.7 ± 3.2 (5–12) | 2.1 ± 0.8 (1–4) | 11.0 ± 1.0 (10–12) |
| Group 1 Tobrilus Male (n=2) | Group 2 Neotobrilus Male (n=7) | Group 3 Brevitobrilus Male (n=3) | Group 4 Semitobrilus Male (n=4) | Group 5 Tobrilus Male (n=19) | Group 6 Neotobrilus Male (n=1) | |
|---|---|---|---|---|---|---|
| L | 2168.7 ± 54.4 (2114–2223) | 1794.1 ± 152.5 (1579–2026) | 2156.7 ± 183.1 (1899–2307) | 2517.3 ± 161.9 (2244–2663) | 1918.3 ± 142.2 (1623–2146) | 1281.3 ± 0.0 (1281–1281) |
| a | 37.2 ± 3.5 (33.8–40.7) | 35.5 ± 3.3 (30.1–39.1) | 39.4 ± 0.1 (39.3–39.5) | 37.3 ± 3.2 (32.8–41.3) | 34.5 ± 3.3 (26.8–39.4) | 29.6 ± 0.0 (29.6–29.6) |
| b | 5.4 ± 0.3 (5.1–5.6) | 5.3 ± 0.3 (4.8–5.6) | 6.5 ± 0.4 (5.9–6.9) | 6.7 ± 0.3 (6.3–7.0) | 5.5 ± 0.3 (4.3–6.0) | 5.6 ± 0.0 (5.6–5.6) |
| c | 14.0 ± 0.1 (14.0–14.1) | 13.7 ± 3.1 (11.3–20.8) | 11.9 ± 0.6 (11.2–12.6) | 8.9 ± 0.5 (8.5–9.6) | 14.5 ± 1.1 (12.9–16.6) | 10.5 ± 0.0 (10.5–10.5) |
| c′ | 4.2 ± 0.1 (4.1–4.3) | 3.5 ± 0.6 (2.1–4.1) | 4.7 ± 0.1 (4.6–4.8) | 5.3 ± 0.2 (5.1–5.7) | 3.8 ± 0.4 (2.8–4.8) | 3.8 ± 0.0 (3.8–3.8) |
| T | 66.4% ± 2.6% (63.8%–69.0%) | 63.6% ± 2.4% (61.3%–67.8%) | 66.6% ± 0.5% (66.3%–67.3%) | 64.2% ± 1.7% (61.8%–66.3%) | 66.6% ± 3.6% (59.0%–77.0%) | 68.7% ± 0.0% (68.7%–68.7%) |
| Tail | 154.6 ± 4.5 (150–159) | 134.8 ± 20.3 (90–158) | 181.8 ± 11.8 (169 –197) | 281.9 ± 14.9 (264–305) | 132.7 ± 10.9 (100–147) | 122.3 ± 0.0 (122–122) |
| LRW | 26.1 ± 0.7 (25–27) | 25.1 ± 2.9 (22–29) | 20.2 ± 1.5 (18–22) | 26.0 ± 1.2 (25–27) | 22.3 ± 1.8 (18–25) | 13.2 ± 0.0 (13–13) |
| Set L | 8.5 ± 1.0 (7–9) | 6.2 ± 1.6 (3–8) | 3.3 ± 0.3 (3–4) | 6.7 ± 0.8 (5–7) | 7.2 ± 0.9 (5–9) | 4.2 ± 0.0 (4–4) |
| Set L/LRW | 32.5% ± 4.7% (27.8%–37.3%) | 24.2% ± 7.8% (9.4%–31.5%) | 16.4% ± 0.5% (15.9%–17.0%) | 25.8% ± 3.6% (20.2%–30.3%) | 32.6% ± 3.9% (23.9% –39.2%) | 32.1% ± 0.0% (32.1%–32.1%) |
| Stoma L | 12.2 ± 0.2 (12–12) | 8.3 ± 0.5 (8–9) | 9.4 ± 5.3 (5–17) | 7.3 ± 1.4 (5–9) | 12.1 ± 1.4 (9–17) | 8.0 ± 0.0 (8–8) |
| Ant tooth pos | 21.0 ± 0.9 (20–22) | 16.5 ± 1.8 (14–19) | 13.8 ± 1.4 (12–16) | 16.3 ± 2.3 (13–19) | 19.0 ± 1.1 (17–21) | 10.0 ± 0.0 (10–10) |
| Post tooth pos | 24.0 ± 0.9 (23–25) | 28.3 ± 2.1 (25–32) | 23.8 ± 0.6 (23–24) | 22.5 ± 2.9 (18–25) | 21.0 ± 1.4 (18–24) | 24.4 ± 0.0 (24–24) |
| Tooth dist | 3.0 ± 0.0 (3–3) | 11.8 ± 2.2 (7–14) | 9.8 ± 1.1 (9–11) | 6.2 ± 1.9 (5–9) | 2.0 ± 0.8 (1–3) | 14.4 ± 0.0 (14–14) |
| Spicule | 43.3 ± 0.7 (43–44) | 60.6 ± 8.4 (50–74) | 57.2 ± 4.6 (52–63) | 135.8 ± 4.5 (130–143) | 35.4 ± 1.9 (32–40) | 60.3 ± 0.0 (60–60) |
| Gubernaculum | 21.7 ± 1.0 (21–23) | 19.1 ± 4.7 (11–25) | 19.8 ± 1.6 (18–22) | 37.7 ± 5.8 (30–45) | 13.3 ± 2.8 (7–17) | 25.6 ± 0.0 (26–26) |
| Supplement # | 6 | 6 | 6 | 6 | 5–7 | 6 |
| Supp prominence | submerged | protruding | protruding | submerged | submerged | protruding |
| Supp rel size | equal | unequal | unequal | equal | equal | unequal |
| Cl-I | 28.2% ± 0.8% (27.4%–28.9%) | 4.4% ± 0.6% (3.5%–5.5%) | 5.0% ± 0.3% (4.7%–5.3%) | 22.7% ± 1.5% (20.3%–24.4%) | 30.1% ± 4.7% (23.9%–42.0%) | 5.0% ± 0.0 (5.0%–5.0%) |
| I-II | 24.6% ± 4.0% (20.6%–28.6%) | 11.2% ± 1.0% (9.5%–12.6%) | 6.8% ± 1.0% (5.5%–7.9%) | 11.6% ± 1.1% (10.3%–12.9%) | 23.0% ± 2.0% (20.1%–27.4%) | 12.7% ± 0.0% (12.7%–12.7%) |
| II-III | 22.8% ±1.7% (21.1%–24.5%) | 12.2% ± 1.7% (9.8%–15.2%) | 14.5% ± 1.2% (13.5%–16.3%) | 23.8% ± 2.0% (20.5%–25.3%) | 19.9% ± 1.8% (17.3%–24.6%) | 12.0% ± 0.0% (12.0%–12.0%) |
| III-IV | 21.7% ± 3.7% (18.0%–25.4%) | 34.7% ± 5.2% (25.8%–41.2%) | 39.7% ± 4.6% (34.5%–45.6%) | 9.0% ± 0.7% (8.1%–9.8%) | 19.2% ± 2.1% (14.4%–22.3%) | 31.3% ± 0.0% (31.3%–31.3%) |
| IV-V | 14.4% ± 0.9% (13.5%–15.3%) | 17.3% ± 6.5% (0.0%–19.8%) | 17.9% ± 1.0% (16.5%–18.9%) | 18.3% ± 2.1% (15.9%–21.5%) | 14.9% ± 5.2% (8.6%–31.8%) | 19.0% ± 0.0% (19.0%–19.0%) |
| V-VI | 16.5% ± 6.9% (9.5%–23.4%) | 27.0% ± 11.1% (18.6%–46.0%) | 21.0% ± 1.8% (18.5%–22.9%) | 37.2% ± 5.2% (31.0%–45.2%) | 23.4% ± 5.5% (10.0%–30.8%) | 24.9% ± 0.0% (24.9%–24.9%) |
| Cl-III | 156.5 ± 3.9 (153–160) | 77.1 ± 5.1 (70–85) | 67.8 ± 5.7 (62–75) | 181.6 ± 27.0 (150–224) | 143.6 ± 7.1 (131–155) | 65.1 ± 0.0% (65–65 |
| Spic/III | 0.3 ± 0.0 (0.3–0.3) | 0.8 ± 0.1 (0.6–0.9) | 0.9 ± 0.1 (0.7–0.9) | 0.8 ± 0.1 (0.6–0.9) | 0.2 ± 0.0 (0.2–0.3) | 0.9 ± 0.0 (1–1) |
| SR/L | 9.6% ± 0.7% (8.9%–10.3%) | 15.7% ± 2.0% (13.7%–20.0%) | 12.0% ± 0.5% (11.3%–12.5%) | 12.4% ± 1.0% (11.3%–13.8%) | 10.3% ± 0.8% (9.1%–12.1%) | 17.1% ± 0.0 (17.1%–17.1%) |
Figure 12.
Linear discriminant analysis (LDA) of haplotype groupings using combined morphological and ecological attributes for A) females; B) males.
Figure 13.
A maximum likelihood 18S phylogenetic tree of 88 Nebraska specimens and 19 GenBank accessions. Tobrilus Groups 1 and 5 are identical for the 18S barcode, and they are united in a strongly supported clade (99 bootstrap value) with Semitobrilus Group 4 and GenBank accessions identified as Tobrilus and Semitobrilus. Blue boxes identify specimens incongruous between COI and 18S trees.