177
the penile urethra of a stranded pygmy sperm whale ( Kogia breviceps ) as reported by
Harms and co-workers ( 2004 ). The multinodular structured construct was 16 cm long
and 3.7 cm diameter and weighed 208 g. Intriguingly, the ureasepositive bacterium
Klebsiella oxytoca that is occasionally associated with struvite urolith formation in
domestic animals, was isolated from this pathological biomineral (Harms et al. 2004 ).
There are some postulates reported concerning uroliths formation. Here, I take
the liberty to list them as follow:
“-struvite calculi can form in any portion of the urinary tract: kidney, ureter, urinary
bladder, or urethra:
– Struvite urolith formation requires urine magnesium ammonium phosphate
supersaturation, which is favored by urinary tract infection with ureasepositive bacteria, alkaline urine, genetic predisposition, and high-protein diet;
– Urease produced by bacteria hydrolyzes urea to form two molecules of
ammonia and a molecule of carbon dioxide;
– The ammonia molecules react with water to form ammonium and hydroxyl
ions, alkalinizing the urine;
– Struvite precipitation is promoted both by the increased ammonium ion
concentration and increased pH,” (Harms et al. 2004 ; see also Osborne et al.
1986 ).
Thus, urate nephrolithiasis can be caused by uric acid, ammonium acid urate, or
sodium acid urate calculi. Both uric acid and ammonium acid urate calculi have
been reported in dolphins (Venn-Watson et al. 2010a , b ).
Nephroliths Information about nephroliths in marine mammals is scare. For
example, Dennison et al. ( 2007 ) reported about two structures. The fi rst contains of
ammonium urate and varying in size from 1 to 15 mm in diameter in the California
sea lion ( Zalophus californianus ). The second one, observed in the northern elephant
seal ( Mirounga angustirostris ), contains uric acid and ammonium urate and was
between 1–10 mm in diameter. These authors hypothesized that “unknown
metabolic derangements due to morphologic or physiologic differences may have
played a role in both cases,” (Dennison et al. 2007 ). All nephroliths observed in
bottlenose dolphins T. truncatus were characterized as 100 % ammonium acid urate
(Venn-Watson et al. 2010a ).
Enteroliths These biominerals of pathological origin are usually located in the
intestinal lumen of humans and mammals like dogs, horses, and cats (see for review
Yuki et al. 2006 ). Also some marine mammals possess enterolithic concretions.
From structural view, these formations include a central nidus with concentric layers
of mineral phases deposited around it. According to Burdett and Osborne ( 2010 ):
“the progressive accumulation of the mineral layers results in partial or total obstruction of
the intestinal lumen. Multiple factors lead to these obstructions. Included are diet, genetics,
alkaline intestinal environments, and ingestion of foreign objects that cannot be digested,
such as hairs, nails and other metal objects, as well fragments of stingray spine,” (Burdett
and Osborne 2010 ).
3.7 Pathological Biomineralization in Marine Vertebrates
the penile urethra of a stranded pygmy sperm whale ( Kogia breviceps ) as reported by
Harms and co-workers ( 2004 ). The multinodular structured construct was 16 cm long
and 3.7 cm diameter and weighed 208 g. Intriguingly, the ureasepositive bacterium
Klebsiella oxytoca that is occasionally associated with struvite urolith formation in
domestic animals, was isolated from this pathological biomineral (Harms et al. 2004 ).
There are some postulates reported concerning uroliths formation. Here, I take
the liberty to list them as follow:
“-struvite calculi can form in any portion of the urinary tract: kidney, ureter, urinary
bladder, or urethra:
– Struvite urolith formation requires urine magnesium ammonium phosphate
supersaturation, which is favored by urinary tract infection with ureasepositive bacteria, alkaline urine, genetic predisposition, and high-protein diet;
– Urease produced by bacteria hydrolyzes urea to form two molecules of
ammonia and a molecule of carbon dioxide;
– The ammonia molecules react with water to form ammonium and hydroxyl
ions, alkalinizing the urine;
– Struvite precipitation is promoted both by the increased ammonium ion
concentration and increased pH,” (Harms et al. 2004 ; see also Osborne et al.
1986 ).
Thus, urate nephrolithiasis can be caused by uric acid, ammonium acid urate, or
sodium acid urate calculi. Both uric acid and ammonium acid urate calculi have
been reported in dolphins (Venn-Watson et al. 2010a , b ).
Nephroliths Information about nephroliths in marine mammals is scare. For
example, Dennison et al. ( 2007 ) reported about two structures. The fi rst contains of
ammonium urate and varying in size from 1 to 15 mm in diameter in the California
sea lion ( Zalophus californianus ). The second one, observed in the northern elephant
seal ( Mirounga angustirostris ), contains uric acid and ammonium urate and was
between 1–10 mm in diameter. These authors hypothesized that “unknown
metabolic derangements due to morphologic or physiologic differences may have
played a role in both cases,” (Dennison et al. 2007 ). All nephroliths observed in
bottlenose dolphins T. truncatus were characterized as 100 % ammonium acid urate
(Venn-Watson et al. 2010a ).
Enteroliths These biominerals of pathological origin are usually located in the
intestinal lumen of humans and mammals like dogs, horses, and cats (see for review
Yuki et al. 2006 ). Also some marine mammals possess enterolithic concretions.
From structural view, these formations include a central nidus with concentric layers
of mineral phases deposited around it. According to Burdett and Osborne ( 2010 ):
“the progressive accumulation of the mineral layers results in partial or total obstruction of
the intestinal lumen. Multiple factors lead to these obstructions. Included are diet, genetics,
alkaline intestinal environments, and ingestion of foreign objects that cannot be digested,
such as hairs, nails and other metal objects, as well fragments of stingray spine,” (Burdett
and Osborne 2010 ).
3.7 Pathological Biomineralization in Marine Vertebrates