Abstract
Common cuttlefish (Sepia officinalis), along with other cephalopods (squid, octopus), are frequently kept and bred in captivity. Cephalopods are commonly used in research, and information regarding their basic biology and husbandry can be found in references intended for the aquaculture industry.1,2,4,5,7-9,11,14,16,18 Published information addressing the diseases and treatment of cuttlefish is limited, however, and no reports currently exist on the mortality of this species in zoos and aquaria.6,7,10,15-18 Unlike a laboratory or propagation facility, zoos typically display a group of fewer than a dozen cuttlefish in tanks designed for exhibition and education.12 It is important to recognize potential disadvantages of a small-scale, captive environment for cuttlefish, particularly with respect to their health and longevity.
Seven hatchling cuttlefish, approximately 1 month of age, were acquired in early July 1998 from the National Resource Center for Cephalopods of the Marine Biomedical Institute (Galveston, TX, USA). At various times between August 1998 and January 1999, these cuttlefish were presented to the Department of Animal Health at the National Zoological Park (NZP) with different degrees of mantle ulceration. Three of the cuttlefish seemed to respond to changes in husbandry and oral chloramphenicol therapy (40 mg/kg PO daily) injected into bits of food, but all seven ultimately died by the end of January 1999. Prior attempts to manage clinically abnormal cuttlefish at NZP using a variety of parenteral antibiotics have had limited success, with anorexia and mantle ulceration commonly reported as problems preceding death. Based upon clinical and pathologic information from NZP, literature review, and communication with experts in cuttlefish husbandry, recommendations for future clinical management of zoo-captive cuttlefish were formulated.
The NZP pathology database was utilized to obtain the causes of mortality determined over a 12-year period, during which 160 of 180 common cuttlefish were completely necropsied. Recorded lifespans ranged from 1–14 months of age. In cases of known sex, age, and weight at postmortem (n=133), 33 cuttlefish were between 7–9 months old and weighed an average of 376.2 g (males, n=18) and 299.0 g (females, n=15). Six carcasses were not retrieved, and 14 were in an advanced state of autolysis. Many cuttlefish had multiple pathologic diagnoses. The most frequent conditions identified were: inanition (n=38); mantle lesions (erosion/abrasion, ulceration, abscess, granuloma, necrosis, dermatitis, cellulitis) (n=97); cuttlebone lesions (fracture, erosion, abscess, deformity) (n=28); septicemia due to Vibrio spp. (n=11) or other bacteria (n=28); and secondary bacterial infections, especially of the cardiovascular (n=51), respiratory (n=52), renal (n=14), ophthalmic (n=38), gastrointestinal (n=60), and reproductive (n=36) systems.
As reported by their keepers, most of these cuttlefish developed anorexia (n=58) and exhibited signs of secondary infection such as cloudy eyes (n=25) prior to death. Other recurrent clinical signs were slow growth or failure to thrive (n=13), depression and lethargy (n=15), and agitation (n=13), as indicated by dark coloration, erratic swim patterns, and/or swift propulsion against tank walls. Trauma to self or to others was commonly mentioned in keeper reports. In some cases, cuttlebone fractures were directly associated with a history of self-trauma (n=4). Sexually developing male cuttlefish were observed to sustain mantle injuries during intraspecific aggression (n=5) that quickly progressed to ulcerative and granulomatous mantle lesions, ultimately leading to sepsis associated with gram-negative bacteria. Postmortem findings correlated with clinical signs such that most cuttlefish had mantle lesions, evidence of sepsis or secondary bacterial infections, and no body stores of fat.
Early detection of illness in this species is critical. Once anorexia develops, medical intervention is unlikely to be successful. Whenever feasible, mantle lesions should be prevented. If cuttlefish are exhibiting behaviors that put them at risk for development of mantle lesions, prophylactic, long-term antibiotics effective against gram-negative bacteria (such as Vibrio spp.) may delay disease progression. Strategies for preventing mantle ulcers include strict attention to tank design (smooth-sided walls), substrate (non-abrasive), population density (one male per small tank), nutrition, water quality, and temperature.16 In addition, environmental stressors, especially lack of hiding places, excessive activity near the tank, overcrowding, and poor water quality should be avoided.11,16 Monitoring cuttlefish sizes and rates of growth can be helpful in assessing their health and nutritional status.3,13,16 The growth rate of cuttlefish is rapid, resulting in a lifespan that rarely exceeds 1 year in a captive laboratory setting.16
The successful display of these unique aquatic invertebrates requires a substantial investment in proper exhibit design, husbandry, and staffing that must be considered by zoos wishing to acquire common cuttlefish. It is hoped that a description of previous NZP cases will help improve clinical management of cuttlefish in zoos and emphasize that husbandry limitations directly affect occurrence of disease conditions and mortality events in this species.
Acknowledgments
The authors are grateful to Dr. J.M. Scimeca for advice and consultations. Special thanks to Ms. Nancy Spangler and Mr. B. Roffey for assistance in compiling data from necropsy reports. We thank the staff of the Invertebrate Department of the National Zoological Park devoted to the husbandry of cuttlefish included in this report, and the Friends of the National Zoo (FONZ) for financial support.
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