Conico-cylindrical Tail Research Articles

Two new species of the order Monhysterida (Nematoda) from the sea of China.

Two new marine nematode species belonging to the order Monhysterida are described from the sea of China. Halomonhysterazhangisp. nov. is characterized by its relatively small body size; short anterior sensory setae; small, circular amphidial fovea located at the level of buccal cavity base; funnel-shaped buccal cavity; an excretory-secretory system with a large ventral gland and opening as a very narrow canal just posterior to the level of cephalic setae; slightly curved slender spicules with cephalated proximal end and tapered distal end; rod-like gubernaculum without apophysis; two papilliform precloacal supplements just in front of the cloaca; conico-cylindrical tail with two ventral papillae, each with a seta; and distance between the vulva and anus slightly longer than the tail length. This is the first new species of epiphytic nematode reported in China. The second new species, Stylotheristusflagellicaudatussp. nov., has a relatively shorter body and longer tail; striated cuticle; The anterior sensilla arranged in two circles, the first circle consisting of six inner labial setiform papillae (3-4 µm) and the second circle consisting of 16 long setae (12-19 µm); a transversely oval amphideal fovea; a well-developed muscle around the funnel-shaped buccal cavity; short spicules and a gubernaculum composed of a single piece; and precloacal supplements absent. An updated key to all species of Halomonhystera and pictorial key to all species of Stylotheristus are also given.

Two new species of Promonhystera Wieser, 1956 (Nematoda: Monhysterida: Xyalidae) from the South China Sea.

Two new species of free-living marine nematodes from the littoral sediment of the South China Sea are described as Promonhystera papilla sp. nov. and Promonhystera fluctispicula sp. nov. Both new species are characterized by striated cuticle; circular amphideal fovea; anterior sensilla in two circles, inner labial sensilla setiform; funnel-shaped buccal cavity; elongated spicules and conico-cylindrical tail. P. papilla sp. nov. is different from all known species of the genus by longer body length (more than 2.1mm versus less than 1.5 mm in other species), longer spicules (sp/a.b.d. = 4.14.6 versus 2.7) and males with three papilliform precloacal supplements and one small postcloacal papilla (versus absence) and gubernaculum boot-shaped. P. fluctispicula sp. nov. is similar to P. tricuspidata Wieser, 1956 in having similar waved spicules but differs from the latter species by tail conico-cylindrical (versus conical) and simple plate-like gubernaculum without tooth (versus gubernaculum with four distal teeth).

Two new species of Xyalidae Chitwood, 1951 (Nematoda, Monhysterida) from Chinese Sea Area.

Two new nematode species of the family Xyalidae were found in the intertidal zone of the Chinese coast, and they are described here as Daptonema sinica sp. nov. and Metadesmolaimus bulbosus sp. nov. Daptonema sinica sp. nov. is characterised by a relatively large body with a broad funnel-shaped buccal cavity; relatively long cephalic setae; a circular amphidial fovea posterior to the buccal cavity; slender spicules bending into a hook shape in the posterior half; a small plate-like gubernaculum without apophysis; and a conico-cylindrical slender tail with terminal setae. Metadesmolaimus bulbosus sp. nov. can be identified by its large buccal cavity, long cervical setae, multiple bulb-like pharyngeal muscular swellings, conico-cylindrical tail narrowing abruptly immediately posterior to the cloaca, straight clavated spicules with a broad proximal end and hooked distal end, and gubernaculum absent. An updated dichotomous key to the species of Metadesmolaimus is given.

A new species of free-living marine nematode, Fotolaimus cavus sp. nov. (Nematoda, Oncholaimida, Oncholaimidae), isolated from a submarine anchialine cave in the Ryukyu Islands, southwestern Japan

Fotolaimus cavussp. nov. was described from a submarine anchialine cave called Akuma-no-yakata on the Shimoji Island, Miyako Island Group, Ryukyu Islands, southwestern Japan. This is the first free-living marine nematode isolated from a submarine cave in Japan, and the third species of the genus Fotolaimus. This new species differs from its congeners by its small body size, wide amphids, long buccal cavity, long conico-cylindrical tail, and proximally curved gubernaculum. We provide amended dichotomous keys to genera in the subfamily Oncholaiminae and species in Fotolaimus. We also analyzed partial DNA sequences encoding ribosomal small subunit RNA and cytochrome c oxidase subunit I from Fotolaimus cavussp. nov. and six other species of Oncholaimidae collected from Japanese waters. The phylogenetic tree based on the ribosomal small subunit RNA sequences using maximum likelihood analysis suggested a close relationship between Fotolaimus and Wiesoncholaimus as well as Oncholaimus. The topology of the tree was similar to those from previous studies; however, it suggested a new phylogenetic position of Adoncholaimus as a sister clade for Viscosia and Oncholaimus.

Three new free-living marine nematode species of Subsphaerolaimus Lorenzen, 1978, Halichoanolaimus de Man, 1886 and Belbolla Andrssy, 1973 from mangrove wetlands in Taiwan.

Three new species of free-living marine nematodes belonging to the genera Subsphaerolaimus, Halichoanolaimus and Belbolla are described from the mangrove wetlands of western Taiwan Island. Subsphaerolaimus danshuiensis sp. nov. is characterized by a body length of 13451693 m, subcephalic setae 22.565.0 m long, cervical setae 16.533.0 m long, an L-shaped spicule 66.976.4 m long, and a gubernaculum with a caudally-dorsally directed apophysis 16.423.0 m long. Halichoanolaimus sicaoensis sp. nov. is characterized by an amphidial fovea with 3.53.75 turns, a conico-cylindrical tail with the cylindrical portion approximately 3/4 of the total tail length, and 1314 not equidistant papillose precloacal supplements. Belbolla forkyspicula sp. nov. is characterized by seven oesophageal bulbs, a short tail, a spicule with a proximal fork, and two winged supplements. Differentiating characteristics of the genera Subsphaerolaimus, Halichoanolaimus and Belbolla are provided. Types are deposited in the College of Fisheries, Jimei University.

One new species of Oxyonchus ( ) (Enoplida: Nematoda) from the Yellow Sea of China

During the diversity assessment of marine nematodes in the China seas, a new species of Oxyonchus (Filipjev, 1927) De Coninck & Schuurmans Stekhoven 1933 was discovered from the Yellow Sea of China. O. boucheri sp. nov. is characterized by cuticle smooth; mouth opening surrounded by three lips separated by deep clefts; cephalic region with developed cephalic capsule; mandibles arch-shaped, rods linked with anteriorly transverse bar, two subventral teeth extend to the mandibles' anterior ends; thick outer and inner labial setae; six files of 2–4 cervical setae; conico-cylindrical tail without terminal seta; curved spicules with tapered distal ends; gubernaculum with dorso-caudal apophysis; a ventral tubular and 6–8 pairs subventral spinous precloacal supplements. The new species differs from other 17 congeners mainly in its conical inner and thick outer labial setae (vs. slender labial setae), files of 2–4 cervical setae present (vs. cervical setae absent), slender spicules with tapered distal ends (vs. spicules with capitulum), both ventral tubular and subventral spinous precloacal supplements (vs. only tubular supplement in males). Updated dichotomous key to the genus Oxyonchus were provided.

A New Species of Free-Living Nematode (Enoplida: Enchelidiidae) from the Mangrove Wetlands of China

A new species, Belbolla mangrove sp. nov., isolated from the mangrove wetlands of Fujian and Zhejiang Provinces in China, is described and illustrated. Belbolla mangrove sp. nov. is characterized by a pharynx with four bulbs, a small gubernaculum with a short dorsocaudal apophysis, four weakly developed precloacal supplements, a conico-cylindrical tail with a terminal spinneret, and the absence of terminal setae. This new species differs from B. vietnamica by the absence of ocelli and the blunt and rounded proximal ends of the spicules. The 18S rDNA GenBank accession numbers of B. mangrove sp. nov. are provided.

Two new species of Chromadorida (Nematoda) from the intertidal zone of the Yellow Sea, China

ABSTRACT Two new species of free-living marine nematodes were discovered off the coast of the Yellow Sea, China, and they are described here as Actinonema diplobulba sp. nov. and Nannolaimoides brevicaudatus sp. nov. Actinonema diplobulba sp. nov. is characterised by amphideal fovea transverse oval-shaped, pharynx with double posterior bulbs, single spicule slender, arcuate with cephalated proximal end, gubernaculum spinous, and extra hammer-shaped lateral pieces (telamon) present. This species is distinguished from its congeners in having double pharyngeal bulbs and both spicule and telamon. Nannolaimoides brevicaudatus sp. nov. is characterised by a slender body with irregular lateral differentiation, multispiral amphideal fovea with five turns and close to anterior end, spicules arcuate with bent proximal end and tapered distal end, gubernaculum expanded distally and tapered proximally, a precloacal papilla and 14 button-shaped precloacal supplements almost equally arranged, and a conico-cylindrical tail 4.3–4.9 times as long as cloacal body diameter. This species differs from its congeners by having a precloacal papilla and 14 button-shaped precloacal supplements, and a comparatively short conico-cylindrical tail. http://www.zoobank.org/urn:lsid:zoobank.org:pub:D74795FE-168E-4F7F-A78C-08EF5B9783A9

Two new species of Xyalidae (Nematoda: Monhysterida) from intertidal zone of the Bohai Sea, China

Two new nematode species are described from the intertidal zone of the Bohai Sea, China. Paramonohystera gracilis sp. nov. is characterized by slender body with a long filiform tail; oval amphidial fovea 6 µm in diameter; spicules slender, 3.4 a.b.d. long; gubernaculum small, plate shaped without apophysis. It differs from the most similar species P. riemanni (Platt, 1973) Lorenzen, 1977 by much slender body and longer filiform tail. Amphimonhystrella boucheri sp. nov. is characterized by short body, deep buccal cavity with funnel shaped anterior portion, circular amphids, conico-cylindrical tail with two thirds conical anterior portion and a third cylindrical posterior portion, small spicules L-shaped and gubernaculum with short apophysis. It is distinguished from the most similar species A. unita Lorenzen, 1977 in buccal cavity funnel shaped, small amphidial fovea circular, spicules short with tapered distal end. Updated keys for valid species of Paramonohystera and Amphimonhystrella are provided.

Three Free-Living Marine Nematodes from Sagami Bay, Japan, with a Description of Wiesoncholaimus jambio sp. nov. (Nematoda: Oncholaimidae).

We describe three free-living marine nematode species from Sagami Bay, Japan. Wiesoncholaimus jambiosp. nov. is the second species of this genus. It differs from the type species, Wiesoncholaimus mawsonae Inglis, 1966, by its dorsal tooth, which is as long as the other two teeth; its conico-cylindrical tail, which is as long as 4.6-4.8 cloacal body diameters; and the absence of the gubernaculum. Thalassironus cf. britannicus de Man, 1889 agrees well with a redescription of Thalassironus britannicus de Man, 1889 based on specimens collected near the type locality. However, as it is possible that T. britannicus sensu lato includes two or more species, our species may not be conspecific to T. britannicus sensu stricto. Vasostoma cf. longispicula Huang and Wu, 2010 closely resembles Vasostoma longispicula Huang and Wu, 2010 originally described from China, but minor differentiations are observed in body diameter, body cuticle thickness, and type of precloacal supplements.

Litinium gludi sp. nov. (Nematoda, Oxystominidae) from Kermadec Trench, Southwest Pacific Ocean

Recent work on the taxonomy of nematodes in Southwest Pacific Ocean trenches has led to the discovery of taxa which so far appear to be restricted to the oceans’ deepest environments. Here, Litinium gludi sp. nov. is described based on specimens obtained from a deep basin within the Kermadec Trench at 9540 m water depth. The new species differs from other species of the genus in having a conico-cylindrical tail, papillose labial sensilla, and heart- or leaf-shaped amphideal fovea. Both SSU and LSU phylogenetic analyses provide strong support for the placement of the new species within a clade containing both Thalassoalaimus and Litinum, and within Oxystomininae, which is consistent with the structure of the female reproductive system with only one posterior ovary in this subfamily. Our molecular analyses also indicate that the new species is most closely related to Thalassoalaimus despite lacking a caudal capsule, the main trait characterizing the latter genus, and despite being most morphologically similar to Litinium, particularly in the unusual shape of the amphideal fovea. However, given the changing definitions of the closely-related genera Thalassoalaimus and Litinium in recent years, available GenBank sequences may have been misidentified, which makes the interpretation of molecular phylogenetic analyses problematic. Given the current morphological definitions of Litinium and Thalassoalaimus, we choose to place the new species within Litinium, despite the apparently contradictory findings of molecular phylogenetic analyses. The placement of Cricohalalaimus in a clade with Thalassoalaimus and Litinium in both SSU and LSU analyses indicates that this genus should be placed within the Oxystomininae and not the Halalaiminae as in the current classification. This new proposed grouping is consistent with variation in the structure of the female reproductive system, a feature which appears more taxonomically informative than amphid shape for subfamily-level classification.

Three new species of free-living marine nematodes (Nematoda: Enoplida) from the Clarion-Clipperton Fracture Zone (CCFZ), North Pacific

Three new species of free-living marine nematodes, Phanodermopsis dordi sp. nov., Halalaimus shinkai sp. nov., and Oxystomina hakureiae sp. nov. are described from the abyssal sediments of the Clarion-Clipperton Fracture Zone, North Pacific. Phanodermopsis dordi sp. nov. differs from the congeners by having papilliform anterior sensilla and a long conical tail with an acute tip. Halalaimus shinkai sp. nov., belonging to Keppner's group 2 based on the presence of caudal alae and the absence of precloacal sensillum or pore, can be distinguished from all of the members of this group by the presence of lateral pieces of gubernacula. Oxystomina hakureiae sp. nov. differs from the congeners by the short setiform anterior sensilla, the amphid located posterior to cephalic sensilla, the conico-cylindrical tail in both sexes, the spicules with a velum and a capitulum, the presence of the gubernacula and the precloacal setae, and the diorchic and monodelphic reproductive systems. The amended dichotomous keys to the species of Phanodermopsis, Halalaimus group 2, and Oxystomina are provided. A new combination Nemanema arenaria (Bussau, 1990) comb. nov. transferred from Oxystomina is also provided.

Two species of Thoracostomopsidae (Nematoda: Enoplida) from Jeju Island, South Korea.

During a survey of intertidal zones at beaches on Jeju Island, two species belonging to the family Thoracostomopsidae were discovered. One new species, Enoploides koreanus sp. nov. and one known species, Epacanthion hirsutum Shi & Xu, 2016 are reported. Along with morphological analysis, mitochondrial cytochrome oxidase c subunit 1 (mtCOI) sequences and 18S rRNA sequences of the species were also obtained and used to check relative p-distance and phylogenetic positions. While most species of Enoploides have long spicules, the new species belongs to a group of Enoploides with short spicules < 150 µm). Of the seven species with short spicules, the new species is most closely related to E. disparilis Sergeeva, 1974. They both have similar body length, fairly similar sized and shaped spicules with small gubernaculum running parallel to distal end of spicule, and an index value of b. The new species can be distinguished from E. disparilis by having pre-anal supplementary organ with short conical tail, while E. disparilis lacks pre-anal supplementary organ and has a long conico-cylindrical tail. Along with the description of the new species, the genus Enoploides Ssaweljev, 1912 is bibliographically reviewed and revised. Of 45 species described to date, 27 are now considered valid, 16 species inquirendae due to inadequate descriptions and ambiguity of the material examined, along with two cases of nomen nudum. With this review, we provide an updated diagnosis and list of valid species, a tabular key comparing diagnostic characters of all valid species, and a new complete key to species. One known species, Epacanthion hirsutum Shi & Xu, 2016, is reported in Korea for the first time. The morphology agrees well with the original description provided by Shi & Xu, 2016. As they had already reviewed the genus at the time of reporting four Epacanthion species, we provide only a description, depiction, and measurements for comparison purposes.

A new free-living marine nematode species of the genus &lt;i&gt;Phanoderma&lt;/i&gt; Bastian, 1865 (Enoplida: Phanodermatidae) from the East Sea, Korea

A new species of free-living marine nematode is described from intertidal sediments of the East Sea, Korea. Phanoderma koreense sp. nov. is characterized by the presence of well-developed pharyngeal and cephalic capsule, six inner labial sensilla present as minute papillae around with circular groove, long and slender spicules with 4-5 serrated distal end, located at the base of the precloacal supplement, a series of eight to nine stout and short setae on the ventral cloacal region and conico-cylindrical tail with two pairs of blunt setae. In this study, we provide taxonomic descriptions and illustrations of a new species by differential interference contrast microscope and a pictorial key to the valid species of Phanoderma Bastian, 1865. This is the first record of the genus Phanoderma in the East Sea, Korea.

Two new and one known deep-sea Comesomatidae Filipjev, 1918 species (Nematoda: Araeolaimida) from New Zealand’s continental margin

One new Sabatieria Rouville, 1903 and one new Hopperia Vitiello, 1969 species are described from Conway Trough off the east coast of New Zealand’s South Island based on light and scanning electron microscope observations and SSU and D2-D3 of LSU molecular sequences. Additional morphological observations and molecular sequence data are also provided for Vasostoma hexodontium Rosli, Leduc & Probert, 2014. Sabatieria articulata sp. nov. belongs to the Praedatrix group and differs from all other species of the genus in having jointed spicules. Hopperia novazelandica sp. nov. is characterized by a relatively stout body, cephalic setae 0.2–0.3 corresponding body diameter long, amphideal fovea with 3.0 turns in males and 2.2–2.5 turns in females, buccal cavity with three teeth, spicules 2.3–2.5 cloacal body diameters long, presence of 19 precloacal supplements, and conico-cylindrical tail with swollen tip and terminal setae. Scanning electron microscopy observations show that the outer cuticle surface of V. hexodontium is smooth and that the inner labial papillae are slightly larger than the outer labial papillae. The SSU consensus tree could not resolve relationships among most Comesomatidae Filipjev, 1918 species and genera included in our analysis. Analyses based on D2-D3 of LSU sequences suggest that Sabatieria, Hopperia, and Dorylaimopsis are not monophyletic; instead, species/genera from the same region tended to cluster together, suggesting that features that characterize the genera Hopperia and Dorylaimopsis, such as a buccal cavity with teeth and an expanded posterior portion, have evolved multiple times independently, possibly from a Sabatieria-like ancestor. This hypothesis, however, will have to be tested using more comprehensive molecular datasets.

Two new species of Xyalidae (Monhysterida, Nematoda) from the East China Sea.

Two new free-living nematode species of the family Xyalidae Chitwood, 1951 found in the East China Sea are described. Daptonema donghaiensis sp. nov. is characterized by epidermal chords of transparent cells present in most parts of the body; amphideal fovea approximately two times head diameter from anterior body end; L-shaped spicules with cephalate proximal end; tubular gubernaculums; and conico-cylindrical tail with long cylindrical portion. Cobbia heterospicula sp. nov. is characterized by slender body, buccal cavity with one dorsal tooth and two small subventral teeth; amphideal fovea far from the anterior body end; spicules that are paired but unequal in size, with right spicule longer and left spicule shorter; gubernaculums with dorsal apophyses; and conico-cylindrical tail with long filiform portion. An identification key to valid species of the genus Cobbia is given.

Two new species of free-living nematodes from the East China Sea

Two new species of free-living marine nematodes of the genera Hopperia and Nemanema are described from the sublittoral sediment of the East China Sea. Hopperia macramphida sp. nov. is characterized by having large amphidial fovea with five turns; arcuate spicules with enlarged proximal end and central internal lamella extending one third of spicule length from proximal end; gubernaculum with bent apophyses, six papilliform precloacal supplements; and conico-cylindrical tail with swollen tip and terminal setae. Nemanema minutum sp. nov. is characterized by relatively smaller body size in the genus; large oval amphidial fovea; conical tail; slender spicules with alae and hooked proximal end; ring-like gubernaculum; and papilliform precloacal supplements with three short setae. An updated dichotomous key is provided for the 17 species of Hopperia.

&lt;i&gt;Oncholaimus langhovdensis&lt;/i&gt; sp. nov. (Nematoda: Enoplea: Oncholaimida), a New Species of Free-living Marine Nematode from Langhovde, Dronning Maud Land, East Antarctica

A new species of free-living marine nematode, Oncholaimus langhovdensis sp. nov., is described from the intertidal zone of Langhovde (near Syowa Station), Dronning Maud Land, East Antarctica. It closely resembles 11 congeners in the conico-cylindrical tail shape present in males and amphid and excretory pore positions, short spicules, and Demanian system structure present in females. However, it mainly differs from these congeners in body size, de Man's ratios, tail length and shape, and Demanian system structure present in females. Oncholaimus langhovdensis sp. nov. also resembles four congeners known only by females, but it can be distinguished from them based on the tail length and uvette position. In addition to O. langhovdensis sp. nov., two undescribed species (Tripyloididae gen. sp. and Axonolaimidae gen. sp.) and four unidentified species (Sphaerolaimus sp., Oncholaimidae gen. sp., Comesomatidae gen. sp., and Chromadorida fam. gen. sp.) were found from the same locality.

Molecular characterisation of five nematode species (Chromadorida,Selachinematidae) from shelf and upper slope sediments off New Zealand, with description of three new species.

Limited molecular sequence data are available for selachinematid nematodes, with little or no data from the Southern Hemisphere or habitats beyond the subtidal zone. Here, we provide molecular sequence data for the small subunit (SSU) 18S rDNA gene and D2-D3 region of large subunit (LSU) 28S rDNA gene of three new (Cheironchus haurakiensis n. sp., Halichoanolaimus anisospermus n. sp., and Bendiella longicauda n. sp.) and two known selachinematid species (Pseudocheironchus ingluviosus Leduc, 2013 and Synonchiella rotundicauda Leduc, 2013) from shelf and upper slope environments off northeastern New Zealand. Cheironchus haurakiensis n. sp. is characterised by having a multispiral amphideal fovea with five turns, lateroventral mandibles with central arm curved distally and bearing 4-5 pointed projections, and each palm bearing 4-5 pointed projections, ten precloacal supplements in a 1 + 9 arrangement, spicules 78 µm long, and blunt conical tail with thickened cuticle. Halichoanolaimus anisospermus n. sp. is characterised by having an amphideal fovea with 5-6 turns, anterior portion of buccal cavity with cuticularised rhabdions terminating in three sets of seven pairs of teeth (denticles), with the central pair of each set positioned above the other six, dimorphism in size of sperm cells between anterior and posterior testes, gubernaculum consisting of two detached lateral pieces (crurae) tapering distally, three small precloacal supplements consisting of slightly thickened and raised cuticle, and a conicocylindrical tail with conical portion 32-38% of total tail length. Bendiella longicauda n. sp. is characterised by having two dorsosublateral rows of pores from midbody to level of cloaca, amphideal fovea with 4.5 turns, posterior rhabdions with numerous small denticles, spicules 2.1 cloacal body diameters long, a conicocylindrical tail 13.3 cloacal body diameters long and with conical portion 8% of tail length. Preliminary phylogenetic analyses for the family Selachinematidae do not provide evidence of clustering according to depth (intertidal/subtidal vs shelf/upper slope) or geographical location (New Zealand vs Northern Hemisphere). The number of available Selachinematidae sequences, however, remains limited and comprehensive analyses based on larger number of sequences will be necessary to provide more solid conclusions.

One new genus and three new species of deep-sea nematodes(Nematoda: Microlaimidae) from the Southwest Pacific Ocean and Ross Sea.

New deep-sea nematodes of the family Microlaimidae are described from the Southwest Pacific Ocean and Ross Sea. Microlaimus korari n. sp. is characterised by annulated cuticle with longitudinal bars, round amphideal aperture slightly smaller than the cryptospiral amphideal fovea, spacious and heavily cuticularised buccal cavity with large dorsal tooth and right subventral tooth situated anteriorly relative to left subventral tooth, slender spicules 4.4 cloacal body diameters long, and gubernaculum 1.2 cloacal body diameters long with laterally curved distal end and swollen proximal end. Bolbolaimus tongaensis n. sp. is characterised by annulated cuticle with longitudinal bars, oval amphideal aperture and cryptocircular amphideal fovea situated between cephalic setae and only partially surrounded by cuticle annulations, and short spicules cuticularised along dorsal edge and at proximal end and with swollen portion near proximal end. Maragnopsia n. gen. is characterised by a minute, non-cuticularised mouth cavity without teeth, an elongated posterior pharyngeal bulb more than twice as long as it is wide, a single outstretched testis, and a conico-cylindrical tail 13-16 anal body diameters long. A list of all 83 valid Microlaimus species is provided. The present study provides the first microlaimid species records from deep-sea habitats (&gt; 200 m depth) in the Southwest Pacific and Ross Sea. The presence of M. korari n. sp. on both the continental slope of New Zealand and Ross Sea abyssal plain suggests that this species has a wide geographical and depth distribution. However, molecular analyses will be required to confirm the identity of these two geographically disparate populations.