The genus Ixodes (Acari: Ixodidae) in Mexico: adult identification keys, diagnoses, hosts, and distribution
El género Ixodes (Acari: Ixodidae) en México: claves de identificación para adultos, diagnosis, huéspedes y distribución
Carmen Guzmán–Cornejo1* and Richard G. Robbins2
1 Laboratorio de Acarología, Departamento de Biología Comparada, Facultad de Ciencias, Universidad Nacional Autónoma de México, 04510 México D.F., México.
2 DPMIAC/AFPMB, Walter Reed Army Medical Center, 20307–5001 Washington, D.C., USA.
]]>*Correspondent:
mcgc@fciencias.unam.mx
Recibido: 27 julio 2009
Aceptado: 01 octubre 2009
Abstract
Identification keys, diagnoses, hosts, and distribution data are provided for adults of the 26 species of Ixodes known from Mexico. Data are from specimens deposited in the Colección Nacional de Ácaros (CNAC), Instituto de Biología, Universidad Nacional Autónoma de México, and from the literature.
Key words: Ixodes, Ixodidae, keys, hosts, distribution, Mexico.
]]>Resumen
Se presentan claves de identificación, diagnosis, huéspedes y datos sobre la distribución de 26 especies de Ixodes conocidas para México. La información proviene de especímenes depositados en la Colección Nacional de Ácaros (CNAC), Instituto de Biología, Universidad Nacional Autónoma de México y de la literatura.
Palabras clave: Ixodes, Ixodidae, claves, huéspedes, distribución, México.
Introduction
Ticks of the genus Ixodes Latreille, 1795 are common parasites of reptiles, birds and mammals worldwide. Many Ixodes species are of great medical and veterinary importance, transmitting microorganisms that cause disease in wild and domestic animals, as well as humans. This genus is said to constitute section Prostriata of the family Ixodidae, because the anal groove embraces the anus anteriorly, forming an arch; all other ixodid ticks belong to section Metastriata, in which the anal groove curves posterior to the anus or is absent. Additionally, all Ixodes lack eyes and festoons and possess an inornate scutum. Sexual dimorphism is pronounced in this genus: the male venter is largely covered by 7 sclerotized plates, and the denticles of the female hypostome are well developed, while those of the male are usually few and small, often appearing only as mild crenulations. Most species inhabit the nests or burrows of their hosts, but others occur in wooded or grassy environments (Cooley and Kohls, 1945; Sonenshine, 1991).
Ixodes is the largest genus in the Ixodidae, comprising 243 species (Guglielmone et al., 2003, 2006); 45 of these are known from the Neotropical region (Guglielmone et al., 2003). In Mexico, the distribution and host relationships of Ixodes spp. were recently reviewed by Guzmán–Cornejo et al. (2007), who identified 26 species in this country: I. affinis, I. angustus, I. bequaerti, I. boliviensis, I. brunneus, I. conepati, I. cookei, I. cuernavacensis, I. dampfi, I. dentatus, I. eadsi, I. guatemalensis, I. loricatus, I. luciae, I. mexicanus, I. murreleti, I. pacificus, I. rubidus, I. scapularis, I. sinaloa, I. spinipalpis, I. tamaulipas, I. tancitarius, I. texanus, I. tovari, and I. woodi. All these species are parasites of birds or mammals, and 1 or more of them have been collected in 20 of Mexico's 32 states (Fig. 1). Veracruz possesses the greatest diversity of Ixodes species (6), and I. boliviensis is the most widespread and associated with the greatest number of hosts.
Based on our studies of Ixodes specimens deposited in the Colección Nacional de Ácaros (CNAC), Instituto de Biología, Universidad Nacional Autónoma de México, we herein present identification keys and diagnoses for adults of all Ixodes species currently known to occur in Mexico.
Materials and methods
]]> Morphological characters were compiled for males and females of Ixodes, based on original descriptions and subsequent publications, together with direct observation of specimens housed in CNAC. Separate dichotomous keys were then constructed for males and females. The female stage is known for all 26 species that occur in Mexico, but the male key includes only 17 species (males of I. bequaerti, I. cuernavacensis, I. dampfi, I. mexicanus, I. murreleti, I. rubidus, I. sinaloa, I. tamaulipas and I. tancitarius are unknown). The keys are followed by brief diagnoses that summarize the salient character states of each sex. For the convenience of readers, we have also recapitulated some of the distribution and host data from Guzmán–Cornejo et al. (2007), occasionally referencing new information published afterward. Hosts cited as Muridae in Guzmán–Cornejo et al. (2007) have been changed to Cricetidae, in accordance with Musser and Carleton (2005).
Ixodes affinis Neumann, 1899
Ixodes affinis Neumann, 1899: 120, original description
Synonym of I. ricinus var. scapularis (Say, 1821): Nuttall and Warburton, 1911: 156, 281.
Ixodes ricinus aragaoi Fonseca, 1935
Ixodes aragãoi Fonseca, in Aragao and Fonseca, 1952
Diagnosis. Female: Cornua absent, auriculae as lateral saliences or ridges; dental formula 4/4 apically, then 3/3 to near base; scutum circular, with conspicuous deep punctations near posterior margin; internal spur of coxa I long, thin, and pointed, overlapping two thirds of coxa II; small external spurs on coxae I–IV. Male: Cornua absent; scutum with large, deep, conspicuous punctations in posteromedian area; similar large, deep punctations on median plate; hypostome long and heavy, with large lateral and posterior denticles in addition to transverse rows of crenulations; internal spur of coxa I very long, overlapping most of coxa II.
Distribution in Mexico. Chiapas and Yucatán.
]]> Hosts in Mexico. Bovidae, Cervidae, and Procyonidae (Mammalia).Ixodes angustus Neumann, 1899
Ixodes angustus Neumann, 1899: 136, original description
Ixodes angustus Neumann, 1901, sp. near loricatus Neumann, 1899, redescribed in error; see Nuttall and Warburton, 1911: 195.
Diagnosis. Female: Cornua and auriculae absent; hypostome Christmas tree–shaped, dentition 3/3; coxa I with internal and external spurs about equal in length; coxae II–IV with small external spurs, decreasing in size. Male: Cornua absent or minute; auriculae as short, rounded lateral ridges; punctations fine in median area of scutum, generally larger laterally; dental formula 3/3, hypostomal crenulations large and arranged in overlapping rows; internal and external spurs of coxa I short and about equal in length; coxae II–IV each with a short but distinct external spur.
Distribution in Mexico. Coahuila.
Hosts in Mexico. Cricetidae (Mammalia).
Ixodes bequaerti Cooley and Kohls, 1945
Ixodes bequaerti Cooley and Kohls, 1945: 173–174, original description
Diagnosis. Female: Cornua distinct, about as wide as long; auriculae as large pointed horns directed posteriorly; hypostome long, narrow and pointed, dentition 3/3; scutal punctations numerous and distinct, those in posteromedian area more numerous, large, circular and deep, those in anteromedian and anterolateral areas smaller and less definite; lateral carinae prominent; coxa I with small internal and external spurs; coxae II–IV with distinct external spurs, smaller on IV. Male: Unknown.
]]> Distribution in Mexico. Chiapas (Cooley and Kohls, 1945; Hoffmann and López–Campos, 2000).Hosts in Mexico. Trogonidae (Trogon sp.) (Aves) (Hoffmann and López–Campos, 2000).
Ixodes boliviensis Neumann, 1904
Ixodes boliviensis Neumann, 1904: 457–458, original description
Ixodes bicornis Neumann, 1906
Ixodes boliviensis may prove to be a junior synonym of
Ixodes diversifossus Neumann, 1899: Guglielmone et al., 2009: 320
Diagnosis. Female: Cornua present; auriculae well developed and curved; dental formula 4/4, then 3/3 and 2/2 to near base; scutal punctations sparse and small over most of scutum, but with few to several large deep ones near posterior margin; coxa I with internal spur very long, almost completely overlapping coxa II; coxae I–IV with progressively shorter external spurs, very small or absent on IV. Male: Cornua absent; auriculae as low, sharp ridges; large, deep punctations posterior to pseudoscutum; similar large, deep punctations on median plate; hypostome broad and heavy but without large lateral denticles; internal spur of coxa I long, extending over most of coxa II.
Distribution in Mexico. Chiapas, Guerrero, Nayarit, Oaxaca, Quintana Roo, and Veracruz.
Hosts in Mexico. "Pheasant" (Galliformes) (Aves), Cervidae, Canidae, Felidae, Procyonidae, Hominidae, and Sciuridae (Mammalia).
]]> Ixodes brunneus Koch, 1844Ixodes brunneus Koch, 1844: 232, original description Ixodes californicus Banks, 1904 Ixodes kelloggi Nuttall and Warburton, 1908
Diagnosis. Female: Cornua short or absent; auriculae large, sharp–edged lateral extensions; dental formula 4/4, then 3/3, and 2/2 to near base; scutum suboval, much longer than wide; coxa I with 2 short spurs, the internal slightly larger and longer than the external; coxae II–IV with short external spurs; trochanters I–III with small but distinct ventral spurs. Male: Cornua absent; dental formula 3/3 and crenulate; pseudoscutum accentuated by scutal depressions posterolaterally; coxa I with internal and external spurs short and about equal in length; trochanters I–III with small but distinct ventral spurs.
Distribution in Mexico. México D.F.
Hosts in Mexico. Unknown.
Ixodes conepati Cooley and Kohls, 1943
Ixodes conepati Cooley and Kohls, 1943: 144–147, original description
Diagnosis. Female: Cornua present and distinct; auriculae absent; dental formula 3/3, then 2/2 to base; scutum with distinct lateral carinae; internal spur of coxa I long, thin, overlapping half or more of coxa II; coxae I–IV with short rounded external spurs, about equal in size. Male: Cornua absent; auriculae present as long lateral ridges; pseudoscutum present, its posterior margin indicated by an area devoid of punctations; surface of scutum smooth except for indented punctate region in scapular areas; coxa I with very short internal spur, external spur faint or absent; coxae II–IV without internal spurs, but each with a short, blunt external spur, largest on coxa IV.
Distribution in Mexico. Coahuila.
Hosts in Mexico. Unknown.
]]> Ixodes cookei Packard, 1869Ixodes cookei Packard, 1869: 67, original description
Ixodes cruciarius Fitch, 1872
Ixodes hexagonus var. longispinosus Neumann, 1901
Ixodes hexagonus var. cookei Nuttall and Warburton, 1911
Diagnosis. Female: Cornua short; auriculae faint as small lateral ridges; dental formula 3/3 apically, then 2/2; scutum with prominent lateral carinae; cervical grooves narrow and shallow but long, approaching posterolateral margins of scutum; internal spur of coxa I long and slim; external spurs of coxae I–IV small, rounded, decreasing in size posteriorly. Male: Cornua absent; auriculae as mild lateral extensions; scutal punctations numerous, moderately large and deep; punctations of median plate numerous but small; hypostome broad and thick, rounded apically; coxa I with long, thin internal spur, overlapping anterior third to half of coxa II; short external spurs on all coxae, about equal in size.
Distribution in Mexico. Nuevo León and Veracruz.
Hosts in Mexico. Canidae, Cricetidae, and Procyonidae (Mammalia).
Ixodes cuernavacensis Kohls and Clifford, 1966
Ixodes cuernavacensis Kohls and Clifford, 1966: 810–811, original description
]]> Diagnosis. Female: Cornua faint; auriculae as large, curved, pointed horns; lateral carinae distinct; coxa I with moderate internal spur; coxae I–IV each with short external spur. Note: Ixodes cuernavacensis is known from a single female that is missing the distal portion of its hypostome. In our key (couplet 14), we assume that the dental formula of this specimen is less than 5/5, basing this assessment on the relative narrowness of the surviving proximal portion and the reduced dentition of the hypostomal base. Male: Unknown.Distribution in Mexico. Morelos.
Hosts in Mexico. Apodidae (Aves).
Ixodes dampfi Cooley, 1943
Ixodes dampfi Cooley, 1943: 21–24, original description
Diagnosis. Female: Cornua present and distinct; posterior margin of basis capituli sinuous; dental formula 3/3 apically, then 2/2 to base; scutum with pronounced lateral carinae; internal spur of coxa I long and thin; external spurs of coxae I–IV small and about equal in size. Male: Unknown.
Distribution in Mexico. Estado de México.
Hosts in Mexico. Geomyidae (Mammalia).
Ixodes dentatus Marx, 1899
Ixodes dentatus Marx, 1899: 19, original description
]]> Diagnosis. Female: Cornua distinct, rounded; auriculae nearly straight retrograde horns; dental formula 6/6 apically, then 5/5 and 4/4, and 3/3 to base; internal spur of coxa I long and pointed; external spurs of coxae I–IV small and about equal in size. Male: Cornua small; auriculae as mild lobes; scutum with punctations in median area somewhat larger and deeper than those elsewhere; hypostome long, crenulations arranged diagonally.Distribution in Mexico. Nuevo León.
Hosts in Mexico. Leporidae (Mammalia).
Ixodes eadsi Kohls and Clifford, 1964
Ixodes eadsi Kohls and Clifford, 1964: 466–470, original description
Diagnosis. Female: Cornua present; auriculae as fine, curved, pointed horns; dental formula 3/3 in anterior two thirds, then 2/2 to base; scutum widest just anterior to midlength, narrowing posteriorly, and with distinct lateral carinae; coxa I with long internal spur; moderate external spurs on coxae I–IV, smallest on IV. Male: Apex of hypostome notched; scutal punctations small except in the median and lateral areas, where they are much larger; coxa I with long, sharp internal spur; coxa II with a small internal spur; all coxae with moderate external spurs.
Distribution in Mexico. Puebla.
Hosts in Mexico. Heteromyidae (Mammalia).
Ixodes guatemalensis Kohls, 1956
Ixodes guatemalensis Kohls, 1956: 636, original description
]]> Diagnosis. Female: Cornua short, pointed; auriculae distinct as large rounded projections; dental formula 4/4 apically, then 3/3, and 2/2 to base; scutal punctations larger and more numerous in lateral fields and posteriorly; coxa I with long, thin internal spur but no external spur; coxa II without spurs; coxae III–IV each with a faint external spur. Male: Basis capituli dorsally with 8–9 deep punctations in lateral fields, suggesting porose areas; coxa I with long, narrow internal spur but no external spur; coxa II without spurs; coxae III–IV each with a small triangular external spur.Distribution in Mexico. Guerrero and Veracruz.
Hosts in Mexico. Sciuridae (Mammalia).
Ixodes loricatus Neumann, 1899
Ixodes loricatus Neumann, 1899: 139, original description
Ixodes coxaefurcatus Neumann, 1899
Ixodes angustus Neumann, 1901; see synonymy for I. angustus Neumann, 1899
Ixodes didelphidis Fonseca and Aragão, 1952
Diagnosis. Female: Cornua and auriculae absent; basis capituli flared laterally; dental formula 2/2; coxa I robust and bifid, internal and external spurs about equal in length; coxae II–IV with large external spurs. Male: Cornua and auriculae absent; basis capituli flared laterally; hypostome similar to female but smaller; coxae as in female.
Distribution in Mexico. Tabasco.
]]> Hosts in Mexico. Atelidae (Mammalia).Ixodes luciae Sénevet, 1940
Ixodes loricatus var. spinosus Nuttall, 1910
Ixodes luciae Sénevet, 1940: 896–898, original description
Ixodes scuticrenatus Vazquez, 1946
Ixodes loricatus vogelsangi Santos Dias, 1954
Diagnosis. Female: Cornua and auriculae absent; basis capituli flared laterally; dental formula 2/2; coxa I robust and bifid, external spur slightly curved, sharp, and much longer than internal spur; coxae II–IV with large external spurs, rounded apically. Male: Cornua and auriculae absent; basis capituli flared laterally; hypostome similar to female but smaller; coxa I robust and bifid, external spur sharp and much longer than internal spur; coxae II–IV essentially as in female.
Distribution in Mexico. Chiapas, Colima, Tabasco, and Veracruz.
Hosts in Mexico. Didelphidae (Mammalia).
Ixodes mexicanus Cooley and Kohls, 1942
]]> Ixodes mexicanus Cooley and Kohls, 1942: 149–152, original descriptionDiagnosis. Female: Cornua absent; auriculae as short, curved horns; hypostome Christmas tree–shaped, attenuated and sharp, dental formula 3/3; scutal punctations distinct, moderate in number, and more or less evenly distributed; coxa I with short internal spur; coxae I–IV with very short external spurs. Male: Unknown.
Distribution in Mexico. Michoacán.
Hosts in Mexico. Emberizidae and Troglodytidae (Aves).
Ixodes murreleti Cooley and Kohls, 1945
Ixodes murreleti Cooley and Kohls, 1945: 213–214, original description
Diagnosis. Female: Cornua very short; auriculae distinct lateral rounded extensions; hypostome large, broad, dental formula 6/6 apically, then 5/5, 4/4, and 3/3 to base; coxa I with 2 short spurs, internal as a projected corner; coxae II–IV with small external spurs. Male: Unknown.
Distribution in Mexico. Baja California.
Hosts in Mexico. Alcidae (Aves).
Note. This record was cited by Hoffmann (1962) and Guzmán–Cornejo et al. (2007) from Baja California Sur; however, the locality for this record (Isla Los Coronados) is in Baja California.
]]> Ixodes pacificus Cooley and Kohls, 1943Ixodes californicus Banks, 1908 (non Banks, 1904)
Reduced to subspecies Ixodes ricinus var. californicus (Banks): Nuttall and Warburton, 1911: 159
Ixodes pacificus Cooley and Kohls, 1943: 139–144, original description
Diagnosis. Female: Cornua absent; auriculae mildly developed as low ridges; dental formula 4/4 distally, then 3/3, and 2/2 at base; scutum oval with uniformly small punctations; internal spur of coxa I long, overlapping coxa II; very short external spurs on all coxae. Male: Cornua absent; auriculae as lateral ridges; hypostome with large lateral teeth; coxae as in female but internal spur of coxa I shorter.
Distribution in Mexico. Baja California. Hosts in Mexico. Under the junior synonym I. ricinus californicus Banks, 1908, Bishopp and Trembley (1945) state that this species "is of distinct importance as a pest of man, domestic animals, and deer" in Mexico. Canidae (Canis familiaris Linnaeus, 1758) (Mammalia) (Hoffmann and López–Campos, 2000).
Ixodes rubidus Neumann, 1901
Ixodes rubidus Neumann, 1901: 282, original description
Diagnosis. Female: Cornua and auriculae absent; dental formula 2/2; lateral carinae present; cervical grooves shallow and short, visible only posterior to middle of scutum; internal spur of coxa I long and slender; all coxae with very short external spurs. Male: Unknown. Distribution in Mexico. Guanajuato and Guerrero. Hosts in Mexico. Canidae and Procyonidae (Mammalia).
Ixodes scapularis Say, 1821
]]> Ixodes scapularis Say, 1821: 79, original descriptionIxodes fuscous Say, 1821
Ixodes reduvius Neumann, 1899 (pro parte)
Ixodes pratti Banks, 1908 (pro parte)
Reduced to subspecies Ixodes ricinus var. scapularis (Say, 1821) by Nuttall and Warburton, 1911: 156–158; see synonymy for I. affinis Neumann, 1899
Ixodes ozarkus Cooley and Kohls, 1944
Ixodes dammini Spielman, Clifford, Piesman and Corwin, 1979
Diagnosis. Female: Cornua small but distinct; auriculae as lateral ridges; dental formula 4/4 apically, then 3/3, and 2/2 to base; scutum almost circular, punctations larger peripherally; coxa I with moderately long internal spur, partly overlapping coxa II; all coxae with short external spurs. Male: Cornua absent; auricula as a small prominence, pointing backward; hypostome large and with a few large lateral teeth; coxae as in female.
Distribution in Mexico. Coahuila, Jalisco, Oaxaca, and Tamaulipas. Woodham et al. (1983) described a broader Mexican range, including Baja California, Baja California Sur, Campeche, Coahuila, Colima, Durango, Hidalgo, Jalisco, Nuevo León, Quintana Roo, San Luis Potosí, and Tamaulipas. Since Guzmán–Cornejo et al. (2007), records have been published from Chiapas (Romero–Castañón et al., 2008) and Nuevo León (Gordillo–Pérez et al., 2009).
Hosts in Mexico. Bovidae (Bos taurus Linnaeus, 1758), and Canidae (Mammalia). Since Guzmán–Cornejo et al. (2007), records have been published from Cervidae (Mazama americana Erxleben, 1777 and Odocoileus virginianus Zimmermann, 1780) (Romero–Castañón et al., 2008) and Leporidae (Silvilagusfloridanus J.A. Allen, 1890) (Mammalia) (Gordillo–Pérez et al., 2009).
]]> Note. Romero–Castañón et al. (2008) incorrectly state that their specimen of I. scapularis from O. virginianus constitutes a new locality record, when, as we have shown (Guzmán–Cornejo et al., 2007), this tick has long been known from Mexico.Ixodes sinaloa Kohls and Clifford, 1966
Ixodes sinaloa Kohls and Clifford, 1966: 811–813, original description
Diagnosis. Female: Cornua distinct, as long as wide; auriculae as slender, pointed, curved horns; hypostome with dental formula 3/3 for most of its length, 2/2 near base; scutum longer than wide, with distinct lateral carinae; internal spur of coxae I long and pointed; external spurs on all coxae short and progressively smaller from I to IV. Male: Unknown.
Distribution in Mexico. Nayarit, Sinaloa, and also from Jalisco (Keirans and Jones, 1972).
Hosts in Mexico. Cricetidae and Heteromyidae (Liomys pictus plantinarensis Merriam, 1902) (Mammalia) (Keirans and Jones, 1972).
Ixodes spinipalpis Hadwen and Nuttall, 1916
Ixodes diversifossus Neumann, 1911 (non Neumann, 1899)
Ixodes diversifossus Bishopp, 1912 (non Neumann, 1899) Ixodes dentatus var. spinipalpis Hadwen and Nuttall in Nuttall, 1916: 301–304, original description Ixodes neotomae Cooley, 1944
Diagnosis. Female: Cornua present; auriculae as fine, curved pointed horns; dental formula 4/4 apically, then 3/3, and 2/2 to base; lateral carinae as low, rounded ridges; internal spur of coxa I long, thin, and somewhat curved; external spurs on all coxae short and progressively smaller from I to IV. Male: Cornua small but distinct; auriculae as mild rounded lateral extensions; hypostome large and mildly notched apically, lateral teeth large and sharp; pseudoscutum present, somewhat darker in color, and indicated by smaller punctations, larger punctations posteriorly; coxae as in female.
]]> Distribution in Mexico. Morelos, Guerrero, Veracruz, and also from Estado de México as I. neotomae Cooley, 1944 (Hoffmann and López–Campos, 2000).Hosts in Mexico. Cricetidae, Sciuridae, and Leporidae (Romerolagus diazi Fernando Ferrari, 1893) (Mammalia) (Hoffmann and López–Campos, 2000)
Ixodes tamaulipas Kohls and Clifford, 1966
Ixodes tamaulipas Kohls and Clifford, 1966: 813–815, original description
Diagnosis. Female: Cornua present, about as long as wide; auriculae as broad, rounded extensions; hypostome relatively broad, dentition 4/4 apically, then 3/3, and 2/2 to base; scutum longer than wide, with distinct lateral carinae; internal spur of coxa I long and pointed, reaching anterior margin of coxa II; external spurs on all coxae short and about equal in size. Male: Unknown.
Distribution in Mexico. Tamaulipas.
Hosts in Mexico. Sciuridae (Mammalia).
Ixodes tancitarius Cooley and Kohls, 1942
Ixodes tancitarius Cooley and Kohls, 1942: 152–154, original description
Diagnosis. Female: Cornua present and distinct; auriculae as large rounded projections; hypostome relatively narrow, dental formula 3/3 apically, then 2/2 to base; scutum suboval, broadly rounded posteriorly, with distinct lateral carinae; internal spur of coxa I long and narrow, overlapping anterior half of coxa II; short but well–defined external spurs on all coxae. Male: Unknown.
]]> Distribution in Mexico. Michoacán, Veracruz, and also from Estado de México (Hoffmann, 1969).Hosts in Mexico. Cricetidae and Hominidae (Homo sapiens Linnaeus, 1758) (Mammalia) (Hoffmann, 1969).
Note. The tick from Valle de Bravo, Estado de México, was identified as near Ixodes tancitarius, and was implicated in paralysis of a human (Hoffmann, 1969).
Ixodes texanus Banks, 1909
Ixodes pratti Banks, 1908 (pro parte)
Ixodes texanus Banks, 1909: 170–173, original description
Diagnosis. Female: Cornua moderate in size, occasionally absent; basis capituli with prominent rounded hump on either side of hypostome, which is rounded apically, dental formula 2/2; scutum rugose, lateral carinae absent; internal spur on coxae I very short; external spurs on all coxae small or almost absent. Male: Cornua absent; auriculae absent but suggested by lateral pointed extensions; hypostome faintly notched, broad at base, with faint crenulations; scutal punctations numerous, large and deep, scutal surface faintly rugose; internal spur of coxa I very short and rounded; external spurs on all coxae as low ridges. Distribution in Mexico. Guerrero (Guzmán–Cornejo et al., 2007) and Nuevo León (Gordillo–Pérez et al., 2009).
Hosts in Mexico. Procyonidae (Guzmán–Cornejo et al., 2007) and Bassariscus astutus (Lichtenstein, 1830) (Procyonidae) (Mammalia) (Gordillo–Pérez et al., 2009).
Ixodes tovari Cooley, 1945
Ixodes tovari Cooley, 1945: 144–148, original description
]]> Diagnosis. Female: Cornua prominent, as long as wide; auriculae as pointed, curved horns; dorsum of basis capituli with lateral margins indented toward porose areas; hypostome pointed, dental formula 3/3, then 2/2 at base; scutum oval, cervical grooves inapparent; internal spur of coxa I long, overlapping anterior margin of coxa II; all coxae with small external spurs, progressively decreasing in size. Male: Cornua prominent, as long as wide; auriculae short and rounded; hypostome elongate and pointed, denticles crenulate and arranged diagonally; coxae as in female, but internal spur on coxa I somewhat longer.Distribution in Mexico. Guanajuato, Nuevo León.
Hosts in Mexico. Leporidae (Mammalia).
Ixodes woodi Bishopp, 1911
Ixodes angustus woodi Bishopp, 1911: 205, original description
Diagnosis. Female: Cornua indistinct or absent; auriculae absent; hypostome apically rounded, dental formula 3/3 apically, then 2/2 to base; scutum with prominent lateral carinae; internal spur of coxa I moderately long, overlapping anterior margin of coxa II; external spurs on all coxae, triangular on I and II, bluntly rounded on III, rounded and reduced on IV. Male: Cornua absent; auriculae broad and laterally salient; hypostome notched apically, dental formula 4/4, crenulations small, arranged in nonoverlapping rows; internal spur of coxa I short and sharp; coxae I–IV each with a short, blunt external spur.
Distribution in Mexico. Coahuila, Morelos, and Tamaulipas.
Hosts in Mexico. Cricetidae (Mammalia).
Discussion
]]> This is the first of a projected series of papers on the ixodid tick genera of Mexico. Tick taxonomists rely on key morphological characters, information concerning host specificity, and distributional data whenever they are confronted with unknown specimens. Summarizing such knowledge facilitates prompt and accurate specimen identification, which is of paramount importance to physicians, veterinarians, public health personnel, and environmental biologists. Our understanding of Mexican Ixodes is still in its infancy, with several species known from only 1 or a few specimens. Males and nymphs are unknown for 9 species, and larvae are unknown for 11 species. Additionally, 11 of the species discussed here (I. angustus, I. bequaerti, I. cuernavacensis, I. dampfi, I. loricatus, I. mexicanus, I. murreleti, I. pacificus, I. sinaloa, I. tamaulipas, and I. tovari) are not even represented in CNAC. These gaps in our knowledge are better comprehended when otherwise diffuse biosystematic data are gathered into single summary reports, such as the one at hand.Studies of Mexican ticks, and of Ixodes species in particular, have been hampered by the tendency of some workers not to cross international borders. Thus, while Cooley and Kohls (1945) and Robbins and Keirans (1992) addressed the Nearctic fauna without regard to national boundaries, Keirans and Clifford (1978) confined their otherwise invaluable synopsis to Ixodes found north of the Río Bravo, even though the Ixodes fauna of the United States includes half the species known from Mexico. Keys to ticks of particular countries, rather than biogeographic regions, face several limitations, including the omission of endemic species with limited ranges or restricted host preferences.
It is hoped that this and forthcoming compilations will stimulate Mexican acarologists and parasitologists to further contribute to our knowledge of tick taxonomy, ecology, biogeography, and host–parasite coevolution. Such subjects are the indispensable underpinnings of research on ticks as disease vectors or reservoirs, and of investigations of local and regional biodiversity.
Acknowledgments
The senior author thanks the Dirección General de Asuntos del Personal Académico (DGAPA), Universidad Nacional Autónoma de México, for the award of a postdoctoral scholarship under the Programa de Formación e Incorporación de Profesores de Carrera en Facultades y Escuelas para el Fortalecimiento de la Investigación (PROFIP). Tila María Pérez, Curator of CNAC, generously granted access to specimens and literature. Thanks also to Griselda Montiel–Parra for her assistance in preparing the Ixodes distribution map.
Literature cited
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