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Objective—To compare efficacy and safety of paste formulations of firocoxib and phenylbutazone in horses with naturally occurring osteoarthritis. Design—Randomized controlled clinical trial. Animals—253 client-owned horses with naturally occurring osteoarthritis. Procedures—Horses were treated with firocoxib (0.1 mg/kg [0.045 mg/lb], PO, q 24 h) or phenylbutazone (4.4 mg/kg [2 mg/lb], PO, q 24 h) for 14 days. Physical examinations and lameness evaluations were performed prior to treatment and after 7 and 14 days. Clinical improvement was defined as a reduction of at least 1 lameness grade or a combined reduction of at least 3 points in scores for pain during manipulation or palpation, joint swelling, joint circumference, and range of motion. Results—Proportion of horses clinically improved on day 14 for the firocoxib group (104/123 [84.6%]) was not significantly different from the proportion for the phenylbutazone group (103/119 [86.6%]). Proportion of horses that were improved on day 14 was significantly greater for horses treated with firocoxib than for horses treated with phenylbutazone with regard to score for pain on manipulation or palpation (P = 0.028), joint circumference score (P = 0.026), and range of motion score (P = 0.012), but not for overall lameness score or joint swelling score. No direct treatment-related adverse effects were detected during the study. Conclusions and Clinical Relevance—Results suggested that overall clinical efficacy of a paste formulation of firocoxib in horses with naturally occurring osteoarthritis was comparable to efficacy of a paste formulation of phenylbutazone.

Objective—To compare pain responses in stallions undergoing standing laparoscopic cryptorchidectomy following intratesticular or mesorchial infiltration of lidocaine. Design—Clinical trial. Animals—20 stallions with 1 or 2 undescended testes. Procedures—Standing horses were administered a nonsteroidal anti-inflammatory drug and a caudal epidural injection of detomidine hydrochloride and underwent laparoscopic cryptorchidectomy. The undescended testis (1/horse) was grasped to determine the preoperative pain response (present vs absent) and assess severity of pain (by use of a visual analog scale [VAS]). The undescended testis or its mesorchium was injected with 2% lidocaine (10 mL); saline (0.9% NaCl) solution (10 mL) was injected in the untreated structure. Presence and severity of pain was determined by 2 individuals as the testis was grasped following infiltration and at the times of ligature placement and transection of the spermatic cord. Serum cortisol concentration was analyzed preoperatively, after ligation, and after transection. Presence or absence of signs of pain, severity of pain, and serum cortisol concentrations were compared within and between treatment groups. Results—Detection of signs of pain and VAS pain scores did not differ between observers at any time point. Perceived pain responses associated with ligature placement differed significantly from preoperative responses. Pain responses and serum cortisol concentrations after intratesticular and mesorchial infiltration of lidocaine did not differ. Conclusions and Clinical Relevance—Results suggested that intratesticular or mesorchial infiltration of lidocaine combined with administration of a nonsteroidal anti-inflammatory drug and caudal epidural injection of detomidine provides adequate analgesia in standing stallions undergoing laparoscopic cryptorchidectomy.

Lacantunia enigmatica n. sp. Rodiles-Hernández, Hendrickson & Lundberg Table 1 Holotype. ECO-SC 3859 (Fig. 1), male, 427 mm SL, México, Chiapas, Río Usumacinta basin, Río Lacantún, Selva Lacandona, Reserva de la Biosfera Montes Azules, 16°08.083' N, 90°55.317' W (Fig. 3), Rodiles-Hernández, 8 November 2002. Paratypes. All Chiapas, México, Río Usumacinta basin. Museum code (following Leviton et al. (1985) but adding here ECO-SC [ECOSUR San Cristóbal, address as for first author] and ENCB-IPN [Escuela Nacional de Ciencias Biológicas - Instituto Politéc- nico Nacional - address as for IPN in Leviton et al.]) and number is followed when data are available by sex, SL mm, collection date, Reserve (Reserva de la Biosfera Montes Azules = RIBMA; Selva Lacandona = SLac [Río Lacantún basin]), Municipio (Benemerito de las Américas [BA], Marqués de Comillas [MdC]), specific locality, Lat. N, Long. W, collector (CCS=Celedonio Chan-Salas; EVV=Ernesto Velázquez-Velázquez; SDC=Sara Domínguez-Cisneros; RRH= Rocío Rodiles-Hernández). * indicates articulated and disarticulated material; ** cleared and stained preparation; *** HRXCT data examined: ANSP 178696**, female, 280 mm, 14 May 1996, RIBMA, Río Lacanjá, 16° 25.92’ N, 90° 51.8’ W, RRH; ANSP 178697, female, 280 mm, 19 May 1997, RIBMA, Río Lacanjá, 16° 26.75’ N, 90° 51.63’ W, CCS; ANSP 178698*, male, 318 mm, 20 May 1997, SLac, MdC, Zamora Pico de Oro, 16° 20.10’ N, 90° 50.58’ W, RRH; ECO-SC 1166, female, 406 mm, 01 Mar. 1997, SLac, MdC, Zamora Pico de Oro, 16° 22.8’ N, 90° 44.99’ W, RRH; ECO-SC 3856, female, 384 mm, 20 May 2001, SLac, MdC, entre Reforma Agraria y Zamora Pico de Oro, 16° 20.10’ N, 90° 50.58’ W, RRH; ECO-SC 3858, male, 320 mm, 3 May 2002, SLac, MdC, Reforma Agraria, 16° 15.31’ N, 90° 51.99’ W, RRH; ENCB-IPN 5787, male, 353 mm, 20 May 1997, SLac, MdC, Zamora Pico de Oro, 16° 20.10’ N, 90° 50.58’ W, RRH; IBUNAM 12739, female, 282 mm, 20 May 2001, SLac, MdC, entre Reforma Agraria y Zamora Pico de Oro, 16° 15.31’ N, 90° 51.99’ W, RRH; TNHC 29071***, female, 347 mm, 5 Dec. 1998, SLac, BA, Puente Lacantún, 16° 32.45’ N, 90° 41.7’ W, EVV; TNHC 29072***, female, 223 mm, 20 May 1997, SLac, MdC, Zamora Pico de Oro, 16° 20.10’ N, 90° 50.58’ W, RRH; UANL 15259, female, 351 mm, 21 Aug. 1998, SLac, MdC, Río Chajulillo, 16° 5.57’ N, 90° 57.47’ W, EVV; UMMZ 243699, female, 295 mm, 20 Mar. 1997, RIBMA, Río Lacanjá, 16° 24.45’ N, 90° 49.46’ W, CCS; USNM 378035, male, 354 mm, 11 Dec. 1997, RIBMA, Río Lacanjá, 16° 25.525’ N, 90° 50.986’ W, EVV. Non-type specimens of Lacantunia enigmatica. ANSP 178695, female, 330 mm, 21 Aug. 1998, SLac, MdC, Río Chajulillo, 16° 5.57’ N, 90° 57.47’ W, EVV; CAS220134, female, 290 mm, 21 Sep. 1997, SLac, MdC, Ejido Reforma Agraria, 16° 15.31’ N, 90° 51.99’ W, CCS; ECO-SC 1239-2, male, 314 mm, 21 Sep. 1997, SLac, MdC, Ejido Reforma Agraria, 16° 15.31’ N, 90° 51.99’ W, CCS; ECO-SC 1363-3, female, 308 mm, 20 May 1997, SLac, MdC, Ejido Zamora Pico de Oro, 16° 20.10’ N, 90° 50.58’ W, RRH; ECO-SC 1368-2, 274 mm, 19 May 1997, RIBMA, Río Lacanjá, 16° 26.75’ N, 90° 51.63’ W, CCS; ECO-SC 1426, female, 319 mm, 19 May 1997, RIBMA, Río Lacanjá, 16° 26.94’ N, 90° 51.84’ W, EVV; ECO-SC 1511-2, female, 302 mm, 11 Dec. 1997, RIBMA, Río Lacanjá, 16° 25.525’ N, 90° 50.986’ W, EVV; ECO-SC 2138, male, 356 mm, 21 Mar. 1998, RIBMA, Río Lacanjá, 16° 24.581’ N, 90° 49.502’ W, EVV; ECO-SC 2582-1, male, 384 mm, 9 Sep. 1998, SLac, MdC, Arroyo Caribe, 16° 34.577’ N, 90° 42.342’ W, EVV; ECO-SC 2582-2, female, 344 mm, 9 Sep. 1998, SLac, MdC, Arroyo Caribe, 16° 34.577’ N, 90° 42.342’ W, EVV; ECO-SC 4005, 360 mm, 7 Feb. 2003, SLac, MdC, Reforma Agraria, 16° 15.31’ N, 90° 51.99’ W, CCS; ECO-SC 4006**, male, 370 mm, 15 May 2003, SLac, MdC, Reforma Agraria, 16° 15.31’ N, 90° 51.99’ W, CCS; ECO-SC 4008, female, 340 mm, 15 Jun. 1997, RIBMA, Río Tzendales, CCS; ECO-SC 4009**, female, 322 mm, 12 Jun. 1977, SLac, MdC, not specified, CCS; ECO-SC 4125, female, 340 mm, 24 Nov. 2003, SLac, MdC, Reforma Agraria, 16° 15.31’ N, 90° 51.99’ W, CCS; ECO-SC 4126, male, 330 mm, 30 Jan. 2004, SLac, MdC, Reforma Agraria, 16° 15.31’ N, 90° 51.99’ W, CCS. Diagnosis: Same as genus. Description: Maximum size exceeding 400 mm SL. Proportional measurements are given in Table 1. Body moderately elongate, markedly depressed anteriorly, strongly compressed posteriorly. Dorsal profile rises vertically from nearly terminal mouth on snout, then in a sharply convex curve from snout to above orbit, then straight and rising gently to occiput; most specimens with low nuchal hump before dorsal-fin origin; profile continuing horizontally below and behind dorsal fin to adipose-fin origin; falling gently below adipose to caudal-fin base. Ventral profile abruptly convex downward from mandible tip to mental barbels; gently convex or straight along head, pectoral girdle and abdomen to pelvic girdle; straight to anal-fin origin, finally rising in straight line to slightly concave curve to caudal-fin base. Cross-sectional shape flattened oval at vertical through middle of eye; head depth at mid-eye much less than head width at same level, about equal to distance between posterior nares, and contained 3 times in bony HL. Maximum body width across cleithra at pectoral spine insertions always greater than body depth, about 3.6-4.6 times in SL. Cross sectional shape becoming sub-quadrangular and deeper behind eye to pelvic-fin insertions, body depth about equal to width near posterior insertion of dorsal fin, increasingly compressed posteriorly onto laterally-flattened caudal peduncle and fin. In dorsal and ventral views, snout very broad and bluntly rounded, projecting slightly beyond mandibular symphysis. Mouth scarcely subterminal, opening anteriorly; margins of closed mouth smoothly curved; no teeth exposed when mouth closed; rictus below eye; gape width about 1.3-1.6 in membranous HL; 1.8-2.1 in predorsal distance. Lips moderately papillate, more so in larger fish; lips set off by grooves from bands of jaw teeth and without accessory folds parallel to tooth rows. Fleshy rictal fold in a shallow pocket behind corner of mouth, protruding a little above general surface of head below maxillary barbel; ventral to rictal fold, a thin submandibular groove extends less than 1/2 distance to symphysis; dorsal to rictal fold a shallow groove extends anteriorly to terminate at insertion of maxillary barbel. Each premaxillary tooth patch broad, its width about 3 times its symphyseal length; premaxillary teeth very fine, needle-like, tall and gently curved inward, especially the inner teeth; teeth arranged in irregular rows, about18 teeth along transect near symphysis in specimens about 30 cm SL. Dentary teeth like those on premaxillary; tooth band broadest near symphysis, tapering laterally onto coronoid process. No teeth on palate. Head skin thick, concealing skull roofing bones and narrowly open cranial fontanelles, yet skull roof near midline not buried by masses of jaw musculature dorsolaterally and laterally on head and masses of epaxial muscle on nape. Supraoccipital process not evident on surface behind occiput; process very short and remote from dorsal fin base. Four pairs of proximally flattened barbels. Maxillary barbels inserted above lip midway between verticals through posterior nostril and eye; reaching to below dorsal fin. Maxillary barbels free from upper lip, laterally compressed basally, lying in shallow groove below eye and on cheek. Nasal barbel arises from anterior rim of posterior nostril; reaching a point 3-4 times eye diameter behind eye and about equal to distance between posterior nares. Inner mental barbels closer to margin of lower jaw than to gular fold apex, not reaching edge of gill membrane and about equal to or a little greater in length than distance between their bases. Outer mental barbels inserted at level of gular fold apex; tips of outer mental barbels reach onto depressed pectoral fin to a point slightly less than length of inner fin ray. Gular fold defining a deep groove in front of hyoid arch, its sides meeting apex at less than right angle. Gill membranes anteriorly united to each other, then diverging without overlap, supported by 11-12 branchiostegal rays (two on posterior ceratohyal, 1 or 2 on joint between ceratohyals, 8 on anterior ceratohyal). Gill rakers stiffly-ossified, sharp and slender; rakers on first branchial arch 14-15, (4 upper, 10-11 lower); first, second and fifth branchial arches with single anterior rows of gill rakers, third and fourth arches with anterior and posterior rows. Anterior nostril tubular, located dorsally on snout, remote from snout tip by about 3 times its own diameter, anterior to a line between anterior edges of maxillary barbel bases. Posterior nostril as close to anterior nostril as to eye (ca. twice its own diameter in front of eye); medially offset from a line between midpoint of anterior border of eye and anterior nostril; nostril rim a thin, hyaline membrane low or incomplete posteriorly and produced anteriorly as thick nasal barbel; aperture ovoid with its long axis parallel to longitudinal body axis. Eye dorsolateral, centered on a vertical at about first third of bony HL, without a free orbital rim, clear corneal skin defines ocular surface and shape of eye. Ocular surface ovoid to nearly circular; pupil less than 50% of ocular surface. Eye relatively small: horizontal ocular diameter 11.2-14.2 in HL, 5.6-7.5 in interocular, 4-6.3 in snout. Cephalic sensory canals thin; supratemporal, supraorbital, infraorbital, and preopercular canals lead to short, multiple-branched cutaneous canals and clusters of small pores on sides and top of head; cutaneous canal branches of mandibular and nasal canals not dendritic on chin and snout, respectively. Lateral line canal straight and superficial with simple, short tubes and pores, ending over hypurals. Dorsal fin inserted a little anterior of first third of SL; its origin near a vertical at tip of inner pectoral-fin rays. 10-12 dorsal-fin rays: spinelet, spine, and 8-10 soft, branched rays; 9-11 pterygiophores. Dorsal-fin base embedded in thick tissue especially at its anterior insertion. Spinelet small, with a shallow anteromedial cavity and its limbs widely diverging at ca. 60° angle. Dorsal spine short, slender, straight, not denticulate; ossified for about half its length, otherwise segmented. Distal margin of dorsal fin rounded, secondfourth soft rays longest, last dorsal-fin ray more than 2/3 length of second soft ray. Adipose fin large, thick; its anterior insertion at about 70% of SL, remote from dorsal fin base, by about 1.1-1.8 times dorsal base. Adipose-fin margin gently rounded, its apex at a vertical just behind middle of anal fin, ending without a short, free lobe at a weak notch in front of upper caudal fin lobe. Adipose-fin length 2.7-3.8 in SL, about 0.8-1 in HL, 2.2-2.7 in length of dorsal-fin base and 1.3-1.8 in length of anal-fin base; adipose-fin height 6-12 times in adipose fin length, 1.7-4.5 in least caudal peduncle depth. Caudal fin slightly rounded to truncate with rounded corners. Principal caudal rays 1,7,9,1; 10-12 upper and 11-13 lower procurrent caudal-fin rays. Anal fin inserted a little behind a vertical at adipose fin origin; fin margin rounded; middle rays the longest. Anal-fin rays 22-26 (9-10 simple). Last two anal-fin rays closely separate; 22-25 anal-fin pterygiophores. Anal-fin base embedded in thick tissue especially at its anterior insertion. Pectoral fin with a spine and 10-11 branched rays; its margin gently rounded, third soft ray longest; no fleshy membrane along medial edge of inner ray; depressed pectoral fin reaches to a vertical between second and third dorsal -fin soft rays. Pectoral spine formed from basal half of first lepidotrich; distal half filamentous and segmented. Pectoral spine articulating base with typical siluriform dorsal, anterior and ventral processes. Shaft of spine without dentations or serrae, and terminating bluntly at transition to segmented ray. Posterior cleithral process narrow, short and moderately sharp; surface buried in skin and weakly ornamented with few subparallel ridges. Axillary pore below postcleithral process. Pelvic fin inserted a little behind a vertical at middle body and below midpoint of depressed last dorsal-fin ray; containing 6 rays, first simple, third longest; no fleshy membrane along medial edge of inner ray; pelvic-fin margin gently rounded; pelvic-fin length contained 6-8 times in SL and separated from anal-fin origin by half its length. Pelvic splint absent. Total vertebrae 55-57, 22-25 precaudals and 31-33 caudals. Weberian complex including 6 vertebrae, first rib on sixth vertebra. Urogenital papilla located in a shallow depression immediately behind anus between pelvic fins about midway along length of inner fin rays. No apparent sexual dimorphism. Distance from anus to anal fin origin about equal to length of inner pelvic ray. Pigmentation. Back, upper sides, nape, and tympanic area laterally over swim bladder medium to dark brown in life and in alcohol pale to dark gray or grayish blue. Upper sides with small dark and irregularly scattered freckles or spots that fade in larger fish; no stripes. Lower sides and venter much lighter, cream to white anteriorly changing to light to medium gray posterior to anus and urogenital papilla or at anal-fin origin. Dorsal fin with or without dark margin, and darker pigment concentrated in membranes between fin rays. Caudal and anal fins with broad dark margins. Adipose pigmentation like that of adjacent back and sides, with vague freckles or spots. Pectoral and pelvic fins with dorsal surfaces mostly pigmented brown to gray proximally; anterior and distal margins pallid, often strikingly so; ventral surfaces of both paired fins lighter; some individuals with evenly dark pectoral and pelvic fins. Dorsum of head and opercles (except for light membranous margin) nearly uniform brown in life or dark gray in alcohol; no light spots over cranial fontanelles. Maxillary barbels dusky gray dorsally; often much lighter anteriorly and ventrally; increasingly lighter distally. Nasal barbels gray proximally grading to lighter tips. Membranous rim of posterior naris and tubular rim of anterior naris white. Lower sides and venter of head and inner mental barbels light cream to white. Outer mental barbels proximally with dark posterior edge, lighter distally. Additional descriptive information on L. enigmatica, including video animations from high-resolution X-ray computed tomography (HRXCT) is available at http://www.digimorph.org and http://clade.acnatsci.org/catfishbone/. Distribution and habitat. Lacantunia enigmatica occurs in the Ríos Lacantún and Lacanjá, tributaries of Río Usumacinta basin, Chiapas, México, inhabiting deep (to 18 m) river channels and pools with rocks and strong eddy currents. Few specimens were taken in stream mouths. Specimens were collected in both high and low water seasons, and generally during the night. Gut contents include fishes, crabs, prawns and large, tough seeds. Etymology. The name enigmatica is Latin for baffling or inexplicable in reference to the unexpected discovery, obscure relationships and origin of the new catfish. We suggest the common name “Chiapas Catfish” (= “Bagre de Chiapas”) for L. enigmatica. Discussion The major phylogenetic lines of Siluriformes are unevenly resolved. South American Diplomystidae are the sister-group to all other catfishes or Siluroidei (Grande 1987, Arratia1987). The North American fossil Hypsidoridae (Grande 1987) are a deep clade subtending the remaining extant siluroid catfishes. The Neotropical extant Cetopsidae may also be among the most basal catfish lines (de Pinna & Vari 1995). The many remaining catfishes are placed in 31 well-supported, monophyletic families, yet few multi-family groups (Arratia et al. 2003). Phylogenetic resolution is high within many families (de Pinna 1993, Arratia et al. 2003), whereas most family interrelationships remain to be determined. Lacantunia is not a basal catfish within or below Diplomystidae. Instead, the new catfish shares derived characters uniting all non-diplomystid catfishes into the Siluroidei (Grande 1987). These synapomorphies are: 8 upper principal caudal-fin rays (cf. primitively9 in diplomystids); barbels on the chin (cf. no mental barbels); fifth vertebra sutured to compound second-fourth (Weberian) fused vertebrae and partly covered by lamellar bone (cf. fifth vertebra with non-sutural joints and lacking covering of lamellar bone). In Siluroidei, Lacantunia and non-hypsidorid catfishes share a reduced distal maxillary arm and short medial maxillary process (cf. in diplomystids and hypsidorids maxillary arm primitively expanded and maxillary process elongated), loss of maxillary teeth (cf. teeth present), and sutures uniting anterior and posterior ceratohyals (cf. synchondral joint between ceratohyals (Grande 1987, de Pinna 1993)). Also among Siluroidei, the development of interdigitating coracoid symphyseal sutures places Lacantunia with non-cetopsid as well as non-diplomystid catfishes (cf. primitively in diplomystids and cetopsids coracoid symphyseal sutures not present; although the sutures secondarily lost in Siluridae and some Trichomycteridae) (de Pinna 1993, de Pinna & Vari 1995). Other Río Usumacinta basin catfishes belong to three families: Ictaluridae, Heptapteridae and Ariidae. Discovery of a new catfish belonging to any of these families would be unsurprising, but such is not the case. Lacantunia resembles ictalurids more than it does heptapterids or ariids, however, Lacantunia lacks the synapomorphies uniting crown group Ictaluridae (Lundberg 1982, Lundberg 1992, Grande & de Pinna 1998): skull roof covered by jaw adductor muscles attached to prominent sagittal crest (cf. primitively, as in Lacantunia, muscles not on skull roof and sagittal crest not developed); infraorbital canal exits frontal bone (cf. canal exits sphenotic); supracleithrum with subpterotic process (cf. process absent). Lacantunia also lacks synapomorphies that place the fossil genus Astephus, an early Tertiary North American catfish, as the sister lineage to crown group Ictaluridae(Lundberg 1992, Grande & de Pinna 1998): loss of bony posterior process on pelvic girdle (cf. primitively ossified posterior process present as in Lacantunia); continuous cartilage along posterior edge of pelvic girdle (cf. cartilage in two parts interrupted by bone); pelvic-fin rays 7 or more and intraspecifically variable (cf. pelvic-fin rays invariably 6). We found no characters suggesting a deeper sister group relationship between Lacantunia and all Ictaluridae. Lacantunia also lacks synapomorphies of Heptapteridae a

This chapter discusses the physical and biological features of five major Mexican rivers—the Rio Panuco, Usumacinta–Grijalva rivers, Rio Candelaria, the Yaqui, and the Rio Conchos. Five additional rivers—the Chihuahuan Desert's Rio Salado; the Rio Tamesi, which joins the Rio Panuco near its mouth; the Rio Fuerte, which flows through some of the continent's largest canyons in the Sierra Madre Occidental to the Gulf of California south of the Yaqui and Mayo rivers; the Ayuquila–Armeria river system, which empties into the Pacific Ocean; and the Rio Lacanja, a small mountainous tributary of the Usumacinta—are also briefly reviewed. The history of human impacts on Mexico's rivers includes many groups of prehistoric inhabitants. Mexico's major rivers are highly exploited. Construction of dams, primarily for crop irrigation in otherwise desert environments, is one of the major factors. Water pollution from discharge of domestic wastes, high salinity, and nutrients from irrigation returns, mining, and industrial wastes is widespread throughout Mexico. With the increase in population and associated land-use change and generally limited resources available for conservation of natural resources the scenario of the rivers are becoming much worse.

A method for performing laparoscopic ovariectomy with high-power ultrasonic shears in mares is described, along with results in 10 mares. Briefly, after epidural administration of detomidine and local anesthesia with mepivacaine, 3 cannulas were placed in each paralumbar fossa. A laparoscope was placed through the most dorsal cannula, and a grasping forceps was placed through the most ventral cannula and used to grasp and manipulate the ovary. The ultrasonic shears was then placed through the middle cannula. The jaws of the ultrasonic shears were closed across a portion of the ovarian pedicle, and the instrument was discharged until tissue within the jaws was transected; the process was repeated until the entire ovarian pedicle was transected. Following removal of the right ovary, it was passed to the left side of the abdomen and both ovaries were removed through an incision in the left paralumbar fossa. No major complications were identified in any of the 10 mares. However, excessive bleeding necessitating reapplication of the ultrasonic shears (2 ovaries) or application of ligating clips (8) was encountered with 10 of the 20 ovaries. Laparoscopic ovariectomy with a high-power ultrasonic shears appears to be safe in mares.

Objective— To compare the peak force required for failure of hand-tied laparoscopic slipknot ligatures. Study Design— In vitro mechanical evaluation of suture material/knot combinations. Sample Population— Four hand-tied laparoscopic slipknots were studied. Three suture materials and 2 suture sizes were evaluated. Twenty samples of each group were tested, for a total of 400 samples. Methods— The 4S modified Roeder, modified Roeder, and Weston and Brooks laparoscopic slipknots using 0 polyglyconate, 0 polyglycolic acid, 1 polyglyconate, and 1 polydioxanone (PDS) were tested. A vertical distracting force (5 mm/s) was applied until failure. Mean peak force to failure was obtained for each suture material, size, and knot combination. Results— Mean (±SEM) peak force to failure of hand-tied ligatures ranged from 156.8±9.1 N to 4.8±.4 N. The 4S-modified Roeder had the highest mean peak force to failure. Ligatures tied with polyglyconate and size 1 suture had the highest mean peak force to failure. Conclusions— The 4S-modified Roeder was significantly and consistently stronger than the other slipknots. Polyglyconate was superior to other suture materials. The 1 polyglyconate had the highest mean peak force to failure followed by 0 polyglyconate that exceeded the 1PDS. Clinical Relevance— The 4S-modified Roeder slipknot using 1 polyglyconate has the greatest breaking strength of sutures tested and should be considered when performing laparoscopic ligatures.

Standing female urogenital endoscopic surgery is facilitated by the more dorsal location of the organs of the female reproduction tract. The most common reason for laparoscopic surgery on the female urogenital system is ovariectomy; however, the technique has been used to diagnose periparturient or reproductive diseases and to perform surgical embryo transfer. Standing surgical approaches avoid the risk and expense of general anesthesia, but these techniques are limited by the temperament and size of the patient and the availability of facilities for restraint. Owner acceptance of laparoscopic procedures is excellent. It is anticipated that standing endoscopic surgery may become the preferred technique for applicable procedures.

Standing female urogenital endoscopic surgery is facilitated by the more dorsal location of the organs of the female reproduction tract. The most common reason for laparoscopic surgery on the female urogenital system is ovariectomy; however, the technique has been used to diagnose periparturient or reproductive diseases and to perform surgical embryo transfer. Standing surgical approaches avoid the risk and expense of general anesthesia, but these techniques are limited by the temperament and size of the patient and the availability of facilities for restraint. Owner acceptance of laparoscopic procedures is excellent. It is anticipated that standing endoscopic surgery may become the preferred technique for applicable procedures.

The minimally invasive nature of laparoscopic techniques and shorter convalescent periods have made these techniques increasingly popular for use in New World camelids (llamas and alpacas). This article outlines the instruments and steps needed to perform laparoscopic surgery on the female reproductive tract in llamas and alpacas.

Convergence has long been of interest to evolutionary biologists. Cave organisms appear to be ideal candidates for studying convergence in morphological, physiological, and developmental traits. Here we report apparent convergence in two cave-catfishes that were described on morphological grounds as congeners: Prietella phreatophila and Prietella lundbergi. We collected mitochondrial DNA sequence data from 10 species of catfishes, representing five of the seven genera in Ictaluridae, as well as seven species from a broad range of siluriform outgroups. Analysis of the sequence data under parsimony supports a monophyletic Prietella. However, both maximum-likelihood and Bayesian analyses support polyphyly of the genus, with P. lundbergi sister to Ictalurus and P. phreatophila sister to Ameiurus. The topological difference between parsimony and the other methods appears to result from long-branch attraction between the Prietella species. Similarly, the sequence data do not support several other relationships within Ictaluridae supported by morphology. We develop a new Bayesian method for examining variation in molecular rates of evolution across a phylogeny.

Objective— To evaluate the effects of ethylene oxide and gas-plasma sterilization on the failure strength and failure mode of pre-tied monofilament ligature loops. Study design— A randomized block design was used by blocking for suture (size 1 polyglyconate, size 2 polydioxanone) and sterilization technique (control, ethylene oxide, gas plasma). Sample population— Twenty replicates of each suture-sterilization technique combination. Methods— Ligature loops were pre-tied using a 4S-modified Roeder knot then exposed to 1 of 3 treatments (control, ethylene oxide, or gas-plasma sterilization). Ligature loops were mounted onto a mechanical testing machine to evaluate the effects of sterilization on failure strength and failure mode (disruption, untying). Results— There were no differences between polydioxanone and polyglyconate suture materials in failure strength or mode within sterilization methods. Both sterilization methods significantly increased the likelihood that suture loops would untie compared with controls subjects. Ligature loops that disrupted had a greater breaking strength than those that untied, regardless of sterilization method or suture type. Conclusions/clinical relevance— Sterilization with either ethylene oxide or gas plasma of pre-tied, polyglyconate, or polydioxanone ligature loops significantly increases the in vitro likelihood of a modified Roeder knot untying. Further studies need to be conducted to determine the in vivo requirements for ligature loops.

Tumours of the small colon and rectum of horses are rare and not well described in the current literature. Most available case reports regarding descending colon abnormalities focus on rectal tears and include descriptions of direct, blind suturing of the defect, rectal prolapse, ventral celiotomy and flank laparoscopy to correct the defects. The case report by Salazar et al. (2010) in this issue describes the use of endoscopy and simultaneous laparoscopic assistance to remove a hamartoma from the mucosal surface of the rectum in a foal, a unique combination not previously documented. Although lymphoma is considered the most common intestinal neoplasia in the horse (Taylor et al. 2006; Zimmel 2010), documented tumours of the small colon and rectum also include lipomas, leiomyomas, leiomyosarcomas, polyps, ganglioneuromas and hamartomas (Porter et al. 2007; Salazar et al. 2010; Zimmel 2010). Leiomyomas and leiomyosarcomas originate from the smooth muscle lining the gastrointestinal tract, while ganglioneuromas are made up of neurons and their processes, Schwann cells and supporting cells. Polyps are often histologically categorised as benign fibromas (DeBowes 1991) and are clinically inconsequential until their size causes blockage or decreases the size of the intestinal lumen to the point of obstruction. Hamartomas, such as that described by Salazar et al. (2010), are defined as an overgrowth of normal tissue in a normal location (Cullen et al. 2002). It is believed that hamartomas occur due to an embryological defect and their growth often ceases once the surrounding tissue has reached maturity. These masses are well differentiated on histological examination, which distinguishes them from malignant neoplasms and there is no evidence to suggest that they are prone to becoming malignant with time. Much like polyps, it is only when their growth causes stricture, obstruction, or impedance on other structures in the body that hamartomas become problematic for the horse. The small colon, more correctly referred to as the descending colon, begins to the left of the root of the mesentery and lies caudodorsally in the left abdomen. It has a length of approximately 3.5 m and is 7–10 cm in width (Rakestraw and Hardy 2006). At the pelvic inlet, the small colon transitions into the rectum, which is 30 cm in length in mature horses then transitions into the anus (Freeman 2006). Surgically, the majority of the small colon can be exteriorised via ventral celiotomy, with only the most proximal and distal portions being difficult to access. The rectum generally can not be exteriorised except by using a very caudal surgical approach. Current literature predominantly includes descriptions of rectal and mesenteric tears and a variety of approaches to the affected areas. Ventral celiotomy was used by Dart et al. (1992) to perform resection and anastomosis on portions of the small colon in 4 cases: small colon strangulation by lipoma, enterolith, fibrous stricture and subserosal haematoma. All 4 horses had portions of the small colon successfully resected, although the authors did acknowledge that had the lesions been more proximal or distal, near the transverse colon or pelvic inlet, respectively, resection may have proved more challenging. Direct, nonvisual suturing of rectal tears is possible with the use of specialised, long-handled instruments (Freeman 2006); however, there is a steep learning curve for this technique. It is possible that masses with large, easily palpable stalks or pedicles may be resected in this manner, although there are currently no case reports or descriptions of such a procedure. Kay et al. (2008) describe a technique for rectal prolapse to allow for direct visualisation of rectal tears that could also be used for exteriorisation of a rectal mass. Stay sutures are placed through the external anal sphincter, traction applied and the sphincter transected along its dorsal vertical border. With the traction maintained, the mass can be manipulated more caudally and into a more advantageous surgical field. Once all surgical manipulations are complete, the incision in the sphincter may be closed with absorbable suture, or left open to heal by second intention. Six mares with rectal tears 20–50 cm proximal to the rectal sphincter were *Corresponding author email: dean.hendrickson@colostate.edu 62 EQUINE VETERINARY EDUCATION Equine vet. Educ. (2011) 23 (2) 62-63 doi: 10.1111/j.2042-3292.2010.00162.x

Objective—To evaluate μ-opioid receptors in synovial membranes of horses and determine whether these receptors are up-regulated in nerve endings during inflammation. Sample Population—Synovial tissue obtained from 39 client-owned horses during arthroscopy and 14 research horses during necropsy; brain and synovial tissues were obtained during necropsy from 1 horse, and control tissues were obtained from a mouse. Procedure—Horses were classified into 7 groups on the basis of histologically determined degree of inflammation. Binding of primary rabbit antibody developed against μ-opioid receptors in equine synovial tissue was studied, using western blot analysis. Synovial membranes were tested for μ-opioid receptors by immunohistochemical staining, using a diaminobenzidine-cobalt chloride chromogen. Homogenates of synovial membranes were evaluated by use of radioligand binding. Results—Examination of western blots of equine thalamus revealed that rabbit antibody developed against μ-opioid receptors yielded a band (molecular weight, 55 kd) that corresponded with that of other opioid receptors. Use of immunohistochemical staining of synovial tissue revealed considerable staining in the proliferative lining layer and in regions surrounding vascular structures. Specific radioligand binding of tissue homogenates was found in all groups. We did not detect significant differences in binding between horses with inflammation and horses without inflammation. Conclusions and Clinical Relevance—Results of immunohistochemical analysis and radioligand binding of tissue homogenates suggest that there are opioid receptors in synovial membranes of horses. Our results support the practice of intra-articular administration of opioids to relieve pain after arthroscopic surgery in horses. (Am J Vet Res 2001;62:1408–1412).

The ictalurid genus Prietella was described from a single locality in northern Mexico (Coahuila) in 1954, and until very recently went largely unstudied. Cave explorers have recently uncovered new localities and a second species much farther to the south (Mexico: Tamaulipas). Our team visited over 50 sites, including all of the previously known sites possible, and explored many new sites, expanding the known range of Prietella and describing their habitat. We identified geological units and mapped caves, identified associated troglobitic invertebrates, estimated population sizes and measured water chemistry parameters. We also comment on laboratory diet, parasites, sensory biology, behavior (such as jaw locking and periods of inactivity), reproduction and systematics based on preliminary genetic data. Prietella phreatophila is listed as endangered, and due to the recent discovery of many more sites (formerly documented from three localities, now known from twelve sites, though some are hydrologically connected) we recommend threatened status, with careful attention to growing threats such as over pumping and contamination of the aquifer it lives in. Should these patterns continue unchecked, re-listing this species as endangered may be called for. Prietella lundbergi was also described from one site but is now known from two, though it is quite rare at both (only five specimens have ever been seen). P. lundbergi was described after the most recent revision of the Mexican endangered species list and should probably be considered as endangered.

Objective— To develop a technique for laparoscopic tubal (oviductal) ligation and to evaluate pregnancy rates for mares that ovulated ipsilateral or contralateral to the ligated oviduct. Study Design— Randomized prospective clinical trial comparing pregnancy rates after unilateral laparoscopic tubal ligation. Animals— Twelve mares of light horse breeds. Methods— One oviduct in each of 6 mares was surgically ligated with a laparoscopic technique; 6 other mares served as nonligated controls. Mares with unilateral tubal ligations (UTL) were inseminated with 500 million progressively motile sperm during 1 cycle when the dominant follicle was ipsilateral to the ligation site and 1 cycle when the dominant follicle was contralateral to the ligation site. Control mares were bred during 2 cycles regardless of the side of the dominant follicle. Pregnancy examinations were performed on days 12, 14, and 16 after ovulation by transrectal ultrasonography. Results— None of the mares became pregnant when ovulations occurred from the ovary adjacent to the ligated oviduct. All 6 mares became pregnant on the first cycle when an ovulation occurred from the opposite ovary. Control mares became pregnant on 10 of 12 cycles (83.3 %). Conclusions— UTL was completely effective in preventing pregnancy when ovulation occurred ipsilateral to the ligation site. The surgical procedure did not interfere with the establishment of pregnancy when ovulation occurred from the contralateral ovary. Clinical Relevance— UTL may be a clinically useful procedure for preparing a recipient mare for gamete intrafallopian transfer. The recipient mare could be allowed to ovulate and UTL would prevent fertilization of her oocyte but would not interfere with normal corpus luteum formation. The donor oocyte could be placed into the oviduct contralateral to the UTL site.

Tumors of the musculoskeletal system are rare in horses; however, they must be taken seriously. Diagnosis requires observation of clinical signs, radiographic findings, and histological examination. Veterinarians must realize prognosis is not favorable for most tumors; however, some of these tumors can be treated or at least ameliorated. Tumors discussed in this article include: osteoma and osteosarcoma; osteoblastoma; chondrosarcoma; fibroma and fibrosarcoma; plasma cell myeloma; synovioma; rhabdomyosarcoma and tumors metastatic to the musculoskeletal system.

The determination of poor performance in the young or unproven horse can be a difficult experience for the practitioner. This article describes an incremental exercise test that may be helpful in determining the cause of poor performance in horses when a complete physical examination and a lameness examination fail to elucidate the causes of poor performance. Included are values from normal yearling and 2-year-old horses that have undergone the incremental exercise test.

Epidural anesthesia and analgesia are popular regional anesthetic techniques in many animal species. However, we have not found any reports of studies in animals that have investigated the extent of cephalad migration and level of sensory blockade achieved based only on the volume of drug injected into the epidural space. The purpose of this study was to determine if there is a relationship between the volume (mL/kg) of an injectate injected epidurally and the extent of its cephalad migration within the epidural space. Twelve adult goats were randomly assigned to three treatment groups based on the volume of 0.12% New Methylene Blue (NMB), 0.1, 0.2, or 0.3 mL/kg, injected into the epidural space. The site and speed of injection, animal position, and direction of needle bevel were held constant. All injections were performed at the lumbo-sacral space immediately following euthanasia. At necropsy, the vertebral columns were transected longitudinally. The extent of cephalad migration of dye within the epidural space was easily determined by staining of the dura. Measurements were rounded to the nearest intervertebral space to which the dye had migrated. The individual making assessments was blinded to all treatments. In goats treated with 0.1, 0.2, or 0.3 mL/kg NMB, the number of stained spinal segments was 3.5 +/- 0.6, 6.5 +/- 0.9, and 8.8 +/- 0.6, (mean +/- SEM), respectively. Linear regression performed on the data was significant (P < .05) with R2 = 0.86. There was a strong linear relationship between volume (mL/kg) of epidurally injected NMB and cranial migration, with the larger volumes producing more cephalad spread within the epidural space. These results provide evidence for the volume of epidural injectate needed to produce a desired level of sensory blockade in adult goats.

A new family (Lacantuniidae), genus and species of catfish, Lacantunia enigmatica, is described from the Río Usumacinta basin of Chiapas, México. This odd siluriform is diagnosed by five distinctively autapomorphic and anatomically complex structures. The fifth (last) infraorbital bone is relatively large, anteriorly convex and remote from a prominent sphenotic process. The lateral margin of the frontal, lateral ethmoid and sphenotic bones are thick at the origins of much enlarged adductor mandibulae and levator arcus palatini muscles; otherwise the skull roof is constricted and flat. One pair of cone-shaped "pseudo-pharyngobranchial" bones is present at the anterior tips of enlarged cartilages medial to the first epibranchial. A hypertrophied, axe-shaped uncinate process emerges dorsally from the third epibranchial. The gas bladder has paired spherical, unencapsulated diverticulae protruding from its anterodorsal wall. Lacantunia enigmatica cannot be placed within or as a basal sister lineage to any known catfish family or multifamily clade except Siluroidei. This species may represent an ancient group, perhaps of early Tertiary age or older, and it adds another biogeographic puzzle to the historically complex Mesoamerican biota.

The American Fisheries Society herein provides an update of their now decade-old list of rare North American fishes. The 1989 list adds 139 new taxa to the list developed by Deacon et al. (1979) of 251 fishes and removes 26 for a total of 364 fishes in Canada, United States, and Mexico that warrant protection because of their rarity. The 26 taxa removed from the 1979 list include 16 removed because of better information on their taxonomy or status and 10 because they have become extinct. Not a single fish warranted removal from the list because of successful recovery efforts. In addition, 49 fishes have changed in status but remain on the list: 7 have improved in status, 24 have declined, and 18 have been reclassified because new information revealed that they were either more common or rarer than was earlier believed and, therefore, were incorrectly classified in 1979. Comparison of the 1979 and 1989 lists indicates that recovery efforts have been locally effective for some species, but are clea...

The endangered Sonoran topminnow Poeciliopsis occidentalis has steadily declined in distribution and abundance in the past several decades, and currently survives in the United States only in several isolated localities in southern Arizona. This reduction is correlated with, and primarily attributed to, habitat destruction, and introduction and establishment of mosquitofish Gambusia affinis and other exotic fishes. Topminnows have characteristically been reduced in number or replaced within a year or two of introduction of non-native fishes. Other native fishes have experienced similar declines after introduction of exotics, and much of the endemic western ichthyofauna may be vulnerable to extirpation in this manner. Predation by introduced fishes on natives appears to be a likely mechanism of replacement.

A patient with a rare manifestation of phenytoin-induced hyperplasia is reported. Severe maxillary and mandibular gingival hyperplasia occurred prior to the eruption of the dentition and without evidence of any predisposing local irritation factors.

A case of severe infection of the head and neck associated with gas-forming organisms in a patient with fractures of the mandible is presented. Selected aspects of antibiotic therapy are discussed.

A vicariance hypothesis of New World biogeography involving transport of living biota on fragments of an ancestral landmass to present positions ranging from southern Alaska to northern South America is developed. Geological, as well as biogeographical, ecological, and systematic data from plethodontid salamanders provide correlative support for the model. Other groups appear to have similar biogeographic histories and, along with further geological data, could provide means of corroboration of this hypothesis. Active biotic dispersal between the American continents before Pliocene closure of the Panamanian isthmus may have been less prevalent than previously believed, and tectonic transport may have dispersed many organisms. If corroborated, geologists may be provided a new method of analyzing relationships among "suspect terranes" using phylogenetic analyses of living biota, and biologists may be required to reassess previous concepts of New World historical biogeography.