340
FINDLAY E. RUSSELL
over 15 fathoms, or more than 2 miles from shore. Myliobatidae are
free swimming rays, and are less likely to be found on the bottom,
although they do sometimes venture into very shallow waters to feed
on bottom invertebrates (Gudger, 1937 ; Russell, 1953a ; Russell, 1955).
The caudal spine, or sting, of the stingray is used by the animal
as a purely defensive weapon, chiefly against those marine creatures
which feed upon it. Stingrays do not ‘‘ attack ” other marine animals,
nor man. The very structure of the venom apparatus including its
innervation, the relationships of the muscles employed in the stinging
act, the nature of the venom, and the rather obvious fact that this
elasmobranch cannot reach its mouth with its sting, would seem to
indicate that this structure is not used as part of the animal’s offensive
armament.
Not all stingrays possess significant amounts of venom within
their caudal spines. In examining over 10,000 of these fish during
the past 15 years we have found that approximately 30% had lost or
torn their integumentary sheath and part of the tissues attached to
the sheath. A number of these fish probably lost these venom containing tissues during the seining operation. However, some stingrays
taken on set-lines had also lost their integumentary sheaths. Thus
it is not difficult to understand why certain discrepancies on the
venom, and on the symptomatology and treatment for stingray
envenomation are found in the literature (Russell et al., 1958a).
1. Venom apparatus
The sting of the stingray is a bilaterally serrated, dentinal caudal
spine located on the dorsum of the animal’s tail. Within this dentinal
structure are numerous canals containing loose reticular connective
tissues and small, thin-walled blood vessels. A thin layer of compact
matrix is seen at the surface of the spine. There may be one or several
of these spines. In adult U. halleri the sting is approximately 4 cm
in length, while in larger species it may reach 30 cm in length. The
sharp serrations are curved cephalically and as such are responsible
for the lacerating effect as the sting is withdrawn from the victim’s
flesh. The spine is encased in an integumentary sheath. The venom is
contained within the ventrolateral grooves. The relationships between
these various structures are shown in Fig. 15.
In U. halleri the integumentary sheath is composed of a variable
layer of loose areolar connective tissue covered by epithelium. The
areolar connective tissue is rich in thin-walled blood vessels. Occasionally, it projects into the epidermis, forming delicate papillae which carry
nutritive blood vessels.
FINDLAY E. RUSSELL
over 15 fathoms, or more than 2 miles from shore. Myliobatidae are
free swimming rays, and are less likely to be found on the bottom,
although they do sometimes venture into very shallow waters to feed
on bottom invertebrates (Gudger, 1937 ; Russell, 1953a ; Russell, 1955).
The caudal spine, or sting, of the stingray is used by the animal
as a purely defensive weapon, chiefly against those marine creatures
which feed upon it. Stingrays do not ‘‘ attack ” other marine animals,
nor man. The very structure of the venom apparatus including its
innervation, the relationships of the muscles employed in the stinging
act, the nature of the venom, and the rather obvious fact that this
elasmobranch cannot reach its mouth with its sting, would seem to
indicate that this structure is not used as part of the animal’s offensive
armament.
Not all stingrays possess significant amounts of venom within
their caudal spines. In examining over 10,000 of these fish during
the past 15 years we have found that approximately 30% had lost or
torn their integumentary sheath and part of the tissues attached to
the sheath. A number of these fish probably lost these venom containing tissues during the seining operation. However, some stingrays
taken on set-lines had also lost their integumentary sheaths. Thus
it is not difficult to understand why certain discrepancies on the
venom, and on the symptomatology and treatment for stingray
envenomation are found in the literature (Russell et al., 1958a).
1. Venom apparatus
The sting of the stingray is a bilaterally serrated, dentinal caudal
spine located on the dorsum of the animal’s tail. Within this dentinal
structure are numerous canals containing loose reticular connective
tissues and small, thin-walled blood vessels. A thin layer of compact
matrix is seen at the surface of the spine. There may be one or several
of these spines. In adult U. halleri the sting is approximately 4 cm
in length, while in larger species it may reach 30 cm in length. The
sharp serrations are curved cephalically and as such are responsible
for the lacerating effect as the sting is withdrawn from the victim’s
flesh. The spine is encased in an integumentary sheath. The venom is
contained within the ventrolateral grooves. The relationships between
these various structures are shown in Fig. 15.
In U. halleri the integumentary sheath is composed of a variable
layer of loose areolar connective tissue covered by epithelium. The
areolar connective tissue is rich in thin-walled blood vessels. Occasionally, it projects into the epidermis, forming delicate papillae which carry
nutritive blood vessels.