Jim Bourdon, Scott Greenwald and Henry Mollet
Illustrated by Jim Bourdon, Copyright © 1997
|DATE||SEX||QTY||Disc Width||WEIGHT||FILE COUNT||COMMENTS|
|Dec. 96||Male||2||53, 57 cm.||4.6, 6.9 kg||.||.|
|.||Female||4||69, 70, 75, 83 cm||13.0-22.7 kg||.||.|
|Mar. 97||Male||2||55, 59 cm||5.8, 8.2||.||.|
|.||Female||4||73, 73, 79, 84 cm||16-25 kg||.||.|
Tooth Marking. In this method, various teeth are marked (burr or drill marks left on selected teeth) and the progression of each series can be periodically checked. This approach would require biweekly removal of the rays for study and dental work. It is uncertain what the impact of a years' worth of this repeated handling may have on the rays and if the trauma itself may alter the results.
Collecting and counting shed teeth. The alternate method is to collect and count the teeth shed by the rays. This method presents a number of challanges (collecting, identifying, etc.) but would prove harmless to the rays. It was decide to pursue this second method.
The early samples provided source material for Jim Bourdon to commence study of the teeth themselves. The teeth were grouped by type as a first step in identifying them as to sex and dental position. To prevent the study from becoming side tracked by details, two parallel studies were initiated.
THE MACRO TRACK
The first would take a broad approach, determining a blended shed rate for the species. This is being done by the weekly collecting and counting of the teeth (and denticles) by Scott and Henry Mollet. The teeth are differentiated only as being high or low-cusped. The results of those efforts is summarized in the first table below. The "Shed Rate" as noted in the table is the number of series (one tooth from each file) shed per week. At the time of this wiritng, the total number of files in the studied rays is not known. For interim purposes, the basis employed will be 35 files per dental band. This number is the median tooth count provided by Nishida & Nakaya (1990) for six males and two females.
THE MICRO TRACK
The secondary course (micro approach) is a monthly effort based on the mid-month sample. It will attempt to group the teeth into the twenty-or-so tooth-types which have been assigned. As greater knowledge is achieved, these counts should be convertible into sex and tooth position.
|Jan 17||52||78||7||1||138||.33 series||22||.||.|
|Jan 24||?||?||?||?||?||?||?||?||may be in 2-14|
|Jan 31||n/a||n/a||n/a||n/a||n/a||n/a||n/a||n/a||included in 2-14|
|Feb 7||n/a||n/a||n/a||n/a||n/a||n/a||n/a||n/a||included in 2-14|
|Feb 14||230||208||33||11||482||.38 series||30||1||3 or 4 week sample|
|Feb 21||84||104||22||2||212||.50 series||54||.||.|
|Feb 28||50||54||11||2||117||.28 series||15||5||.|
|Mar 7||67||75||6||4||152||.36 series||23||15||.|
|Mar 14||60||63||13||4||140||.33 series||28||5||.|
|Mar 21||51||81||13||5||150||.36 series||54||.||.|
|Mar 28||43||57||9||1||110||.26 series||18||.||.|
|Apr 4||57||72||17||0||146||.35 series||27||.||.|
|Apr 11||70||73||12||4||159||.38 series||22||.||.|
|Apr 18||61||68||9||1||139||.33 series||39||.||2nd syphon|
|Apr 25||75||74||17||3||169||.40 series||60||.||2nd syphon|
|May 2||49||73||10||5||137||.33 series||31||.||2nd syphon|
|May 9||65||67||7||1||140||.33 series||65||.||2nd syphon|
|May 17||62||97||5||1||165||.34 series||45||.||8 day sample, rate adjstd|
|May 23||51||51||12||1||115||.32 series||28||.||6 day sample, rate adjstd|
The following table reflects the results of a particular sample and the month it was taken. Noted parenthetically is the number of bicusped teeth within a particular group count. Pathological teeth have not been included in the total, but their number is shown at the end of each month.
|Go to:||Pelagic Stingray Home Page,||Dentition,||Shed Teeth,|
Page revised July 31, 1997