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ABNORMAL AMPHIBIAN MONITORING
Abnormality classification SOP
- A. Objective: To classify frog abnormalities for
analysis.
- B. Background: There is variability in what researchers
term "abnormal" when reporting the prevalence of abnormal frogs. Researchers who focus on the prevalence of skeletal and eye abnormalities often exclude traumatic injuries, diseases, and surficial abnormalities or infections from their reports (Eaton et al. 2004; Helgen et al. 2000; Hoppe, 2000; Hoppe, 2005; Johnson et al. 2001; Levey 2003; Ouellet et al. 1997; Schoff et al. 2003, Taylor et al. 2005). Other researchers include abnormalities and diseases but not obvious injuries when reporting the prevalence of abnormal frogs (McCallum and Trauth 2003), and still others report all gross physical abnormalities (Dubois 1979; Johnson et al. 2002; Lannoo et al. 2003). Because of this variability, a decision was made in the USFWS Abnormal Amphibian surveys to categorize frogs with any gross physical abnormality as “abnormal” to ensure consistency in field data collection (USFWS 1999). Consequently, the results from our surveys include more abnormalities than are reported by most researchers studying abnormal frogs. We developed this abnormal classification standard operating procedure (SOP) to enable a more accurate comparison of our field data with published research. Regional amphibian coordinators will utilize this SOP to further refine our “abnormal” category and ensure consistency in our classification of abnormal frogs. The SOP combines abnormalities into categories and subcategories, which may stem from similar causes, and provides us with more power to detect relationships between environmental variables and certain types of abnormalities. The abnormality classification SOP has its origins in the Field Guide to Malformations of Frogs and Toads with Radiographic Interpretations (Meteyer,
2000), which describes malformations in detail with photographs and radiographs, and in the body of literature cited above. Additional support for this SOP comes from knowledge gained from a large subset of newly metamorphosed frogs radiographed and analyzed for parasites and
diseases between 2000 and 2005 for the Abnormal Amphibian surveys. Those analyses provided insight into the gross appearance of certain injuries, malformations, infections, and diseases.
- C. Existing Definitions: We recognize there are different
definitions and classification schemes that have been used in published
literature or by the public when describing the gross physical condition of an
amphibian. For our purposes, we will use the following definitions from Johnson et al. (2001) as they are best suited to the goals of the USFWS Abnormal Amphibian surveys:
- i. Abnormality: Any gross deviation from the normal range in
morphological variation, be it traumatic or developmental.
- ii. Malformation: Permanent structural defect resulting from abnormal development.
- iii. Deformity: Alteration in an organ or structure that originally formed correctly. Deformities result from mechanical factors,
such as amputation.
- D. Existing
Resources: The USGS field guide to
common malformations in frogs and toads:
- Meteyer, C.U. 2000. Field Guide to Malformations of Frogs and
Toads with Radiographic Interpretations, 2000. Biological Science Report
USGS/BRD/BSR-2000-0005.
- E. Further Classification: An analysis of project data from 2000-2006, and of the available literature, suggests that the initial USFWS “Abnormal” classification can be further subdivided into the following categories: Surficial Abnormality, Infectious Disease, Skeletal Abnormality, and Eye Abnormality, according to the flow chart below. Skeletal Abnormality is further divided into 3 subcategories: Skeletal Malformation, Skeletal Abnormality with Unclear Etiology, and Skeletal Injury. The flow chart is not exhaustive for all abnormalities, but rather shows abnormalities commonly encountered by USFWS employees. The text following the diagram has a more extensive list of abnormality types in each category, as does Table 1. The terminology for each abnormality is taken from Meteyer (2000). Photographs of some common abnormalities are included in the text. NOTE: Every USFWS employee using this SOP should first use the Meteyer (2000) guide to identify the type of abnormality (or abnormalities) that a frog has before using this SOP to further classify the abnormal frog.
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- *Although skin webbing is not technically a skeletal malformation, we have decided to include it under the skeletal malformation category for several reasons. First, skin webbing, along with other skeletal malformations such as polymelia, polydactyly, and taumelia, may be diagnostic of Ribeiroia infections. Second, skin webbing restricts the movement of the skeletal system and, as such, could be viewed as a type of skeletal abnormality. Finally, skin webbing has been described in Meteyer (2000) as a malformation. For the purposes of this SOP and the USFWS Abnormal Amphibian surveys, skin webbing will be categorized as a skeletal malformation.
- F. Surficial Abnormalities: Surficial Abnormalities include abnormal pigmentation, wounds, scars, cysts, infections, subcutaneous hemorrhaging, or
edema. Wounds can be caused by predation or other trauma. These may leave hematomas
(bruises) or scars, which disrupt the normal skin pigmentation and appear a different color than the rest of the animal (red, brown, black, or even bluish).
Split or forked tails may be healed injuries and are therefore considered surficial abnormalities. Edema, or fluid-filled swelling under the skin, is considered a surficial abnormality for this SOP. Small, fluid-filled or hardened cysts not affecting the skeletal system also should be included in this category for the purposes of this SOP. Some species of trematodes and nematodes create rather distinctive cysts on the surface of the skin.
- G. Infectious Diseases: Frogs exhibiting disease symptoms that manifest as physical abnormalities should be classified in the disease category. Two diseases encountered and
diagnosed between 2000 and 2005 are a Perkinsus-like protozoan organism and Ichthyophonus. Perkinsus symptoms include severely swollen viscera that lead to a bloated body and an infected, swollen (enlarged) heart. The swollen heart is occasionally displaced to the throat area and is visible through the skin. Ichthyophonus symptoms include a swollen tail resorption site that matches the surrounding skin in color and translucency (i.e., not a cyst).
- H. Skeletal Abnormalities: The Skeletal Abnormality category comprises three subcategories: Skeletal Malformations, Skeletal Abnormalities with Unclear Etiology, and Skeletal Injuries. If a frog has any of the abnormalities in these three subcategories, it should be placed in the Skeletal Abnormality category, and also in the appropriate subcategory.
- i. Skeletal Malformations: Frogs with skeletal
malformations have skeletal systems that have grown in an abnormal way. Examples of skeletal malformations include:
- 1. small head or blunt snout (microcephaly),
- 2. shortened or malformed jaw (brachygnathia),
- 3. curved spine in a lateral direction (scoliosis),
- 4. curved spine in a dorsoventral direction (lordosis),
- 5. completely missing limbs with no stump (amelia),
- 6. shrunken limb (micromelia),
- 7. shrunken limb elements, such as shortened tibiae,
fibulae, or metatarsals (hemimelia),
- 8. extra limb or limbs (polymelia),
- 9. bone bridge (taumelia),
- 10. extra digits (polydactyly),
- 11. fused digits (syndactyly),
- 12. digit bent at right angle to normal trajectory (clinodactyly),
- 13. extra bones in a digit (polyphalangy),
- 14. rotated long bones with reversed digit order (anteversion), or
- 15. skin webbing that restricts skeletal movement (cutaneous fusion).
- ii. Skeletal
Abnormalities of Unclear Etiology: If a frog is missing part of a limb (ectromelia) or has a shortened or missing digit or digits (brachydactyly or ectrodactyly) yet there is no
evidence of trauma (i.e., no blood visible at capture and the bone is contained
within the skin), it should be scored as a skeletal abnormality of unclear
origin. If a leg stump is present, even if very small, the abnormality should be classified as ectromelia.
- iii. Skeletal
Injuries: If a frog has a missing or
broken limb (or part of a limb) where either blood is noted at capture or bone
is protruding through the skin, the abnormality should be classified as a
Skeletal Injury. There must be evidence of trauma (e.g., blood or a broken bone) to
qualify for this category.
- I. Eye
Abnormalities: Any abnormality of
the eye should be classified in this category. The most common eye abnormalities are anophthalmia, abnormal iris coloration, and abnormal eye, iris, or pupil sizes.
- i. Anophthalmia:
The eye is not present, and skin is grown over where the eye should be.
- ii. Abnormal Iris
Coloration: The eye is present, but something is unusual about the
coloration. The most common eye color anomalies are heterochromia (the eyes are two different colors), reduced pigment in one or both eyes, and melanistic or “black” eye, where either one or
both eyes are all black.
- iii. Abnormal Size
or Shape: One eye, iris, or pupil is a different size or shape than the
other, or both eyes deviate from the normal size range of the rest of the
population.
Table 1. Abnormality descriptions for different
classification categories and subcategories.
CATEGORY and SUBCATEGORY |
ABNORMALITY DESCRIPTION |
SURFICIAL ABNORMALITY |
BLOOD POOLED IN LEGS OR
ELSEWHERE |
CYST OR LUMP UNDER SKIN |
DISCOLORED SKIN - INDICATIVE
OF SCARRING |
EDEMA |
FLESH CUT OR WOUND WITH
BLOOD |
BIFURCATED OR FORKED TAIL |
INTESTINES PROTRUDING |
MISSING TYMPANUM |
OTHER PIGMENT ANOMALY |
SORE OR WOUND BUT NO BROKEN
BONES, AND/OR NO DISLOCATIONS |
INFECTIOUS DISEASE |
ICHTHYOPHONUS SYMPTOMS |
PERKINSUS SYMPTOMS |
SKELETAL ABNORMALITY |
|
Skeletal Malformation |
AMELIA - MISSING LIMB |
ANTEVERSION - TOES CURLED
INTO FIST OR FINGERS/TOES IN REVERSE ORDER WITH NO BLOOD |
BRACHYGNATHIA - SHORTENED OR
MALFORMED JAW |
CLINODACTYLY - DIGIT BENT AT
RIGHT ANGLE TO NORMAL TRAJECTORY |
CUTANEOUS FUSION - SKIN
WEBBING THAT RESTRICTS SKELETAL MOVEMENT |
HEMIMELIA - SHRUNKEN LIMB
ELEMENTS - SOME ELEMENTS ARE SHRUNKEN, BUT NOT ALL |
LORDOSIS - SPINAL CURVATURE
IN A DORSOVENTRAL DIRECTION |
MICROCEPHALY - SMALL HEAD OR
SHORTENED SNOUT |
MICROMELIA - SHRUNKEN
LIMB - ALL LIMB ELEMENTS SHRUNKEN
INCLUDING FOOT |
POLYDACTYLY - EXTRA DIGITS |
POLYMELIA - EXTRA LIMB |
POLYPHALANGY - EXTRA BONES
IN A DIGIT |
SCOLIOSIS - SPINAL CURVATURE
IN A LATERAL DIRECTION |
SYNDACTYLY - DIGITS FUSED
TOGETHER |
TAUMELIA -
BONE BRIDGES
OR BONY TRIANGLES |
Unclear Etiology |
BRACHYDACTYLY - TOES SHORT
OR MISSING PHALANGES WITH NO EVIDENCE OF TRAUMA |
ECTRODACTYLY - DIGIT OR
DIGITS MISSING WITH NO EVIDENCE OF
TRAUMA |
ECTROMELIA - MISSING PART OF
LIMB - NO BLOOD OR BONE PROTRUDING (OR NOT MENTIONED) |
KINKED TAIL |
NON-FLEXIBLE LIMB |
ONE LEG THINNER THAN OTHERS |
Skeletal Injury |
AMELIA - LIMB FULLY REMOVED
WITH BLOOD AT CAPTURE |
APPENDAGE DISLOCATED,
DANGLING, OR HANGING OFF |
BRACHYDACTYLY - TOES MISSING
PHALANGES WITH PROTRUDING BONES OR FLESH WOUND |
ECTRODACTYLY - DIGIT OR
DIGITS MISSING WITH BLOOD OR PROTRUDING BONE |
ECTROMELIA - MISSING PART OF
LIMB - WITH BLOOD OR PROTRUDING BONE |
TOES CURLED OR SMASHED WITH
BLOOD |
EYE ABNORMALITY |
ABNORMAL IRIS COLORATION -
HETEROCHROMIA (EYES TWO DIFFERENT COLORS), REDUCED PIGMENT IN IRIS, OR
UNPIGMENTED IRIS (ONE OR BOTH EYES ALL BLACK) |
ABNORMAL SIZE OR SHAPE OF
EYE, IRIS, OR PUPIL |
ANOPTHALMIA - MISSING EYE |
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