Surgery of Exotic Animals. Группа авторов

ambitious technical work, Weissburg et al. (2001) transplanted fiddler crab (Uca pugilator) limbs in order to study the well‐known differences between male and female behavior in this species and the neurosensory basis of these behaviors. Fiddler crabs will autotomize limbs when stressed or traumatized. The researchers would apply pressure to a portion (merus) of the feeding appendages in order to induce autotomy. The animals were then maintained through molting stages until a 2.0 mm limb bud appeared. At this time, the animals were placed in 25 ppt artificial seawater with 30 mg/L gentamicin and 4.0 ml/L Fungizone^® for three days before surgery. Host crabs were similarly prepared and another surgeon‐induced autotomy of the major claw, and a donor bud was secured to the empty socket with cyanoacrylate adhesive. Over a three‐year period the authors transplanted over 680 claws with 101 developing into functioning feeding claws by the second postsurgical molt. For a thorough review of autotomy among the invertebrates, please refer to Fleming et al. (2007).

Arachnids

      The Class Arachnida is a huge group of animals (over 100,000 species) that includes over 30,000 spiders, and less conspicuous groups such as the harvestmen, mites, ticks, and scorpions. Tarantulas (actually not true spiders) represent an important taxon of commonly kept arachnids that commonly require medical care. Scorpions also appear with some frequency in the pet trade and are common display animals in zoos and museums.

Surgical repair of the fractured exoskeleton can be accomplished with surgical adhesives like methylmethacrylate or cyanoacrylate (Wolff 1993). A fractured abdomen in a tarantula carries a grave prognosis, but if the hemolymph hemorrhage can be contained with the use of a topical adhesive, the animal can survive. Another common problem that may require intervention is dysecdysis (difficulty shedding). A tarantula or other arachnid that experiences this life‐threatening problem can be either anesthetized or manually restrained while forceps or other appropriate instruments are used to gently extract the animal from the adhered exoskeleton (Figure 4.8).

      Like many arthropods, scorpions can display autotomy (Pizzi 2002), but in the case of some species belonging to the genus Ananteris, they can autotomize their tail (metastoma), including a portion of the gastrointestinal (GI) tract, and survive for up to eight months (Mattoni et al. 2015). Virtually all other arthropods that practice autotomy drop (and can redevelop) limbs. In the case of the Ananteris scorpions, tail autotomy appears to be a defense or escape response practiced most commonly by males. While survivors can no longer defecate or sting, they can live long enough to consume small meals and mate (Mattoni et al. 2015). According to one study, sutures are of little use on spiders (Pizzi and Ezendam 2002). Autotomy can be induced in tarantulas by using forceps to grasp the injured appendage by the most proximal segment (femur) and quickly pulling upward (Zachariah and Mitchell 2008). Another small surgical procedure involves inserting microchips (passive integrated transponder [PIT] tags) into manually restrained tarantulas. To do this, an area on the opisthosoma between the heart and intestines was prepared by gently removing the setae from a 1.5 × 1.5 mm area with a 20‐gauge needle. The needle tip was then used like a scalpel to open the exoskeleton allowing for insertion of the PIT tag with fine sterile forceps. The wound was then dabbed dry and sealed with cyanoacrylate to minimize hemolymph loss (Reichling and Tabaka 2001).

Figure 4.8 This image shows the careful removal of a retained exoskeleton from a tarantula.

      Source: Courtesy of Dan Johnson.

Limulus

      Limulus polyphemus, the American horseshoe crab, is actually not a crab at all but a member of the Class Merostomata in the Phylum Chelicerata. Horseshoe crabs are more closely related to arachnids than crustaceans. Limulus is a very important animal for biomedical research, is used as bait and fertilizer, and is an important display and “touch tank” animal in public aquaria (Smith and Berkson 2005; Smith 2012). The anatomy and physiology of these animals have been thoroughly researched, and they are easy to handle and work with. Investigators examining vision and communication of the numerous ommatidia in the Limulus lateral eye were awarded the Nobel Prize for medicine or physiology in 1967 (Hartline and Ratliff 1958).

Trauma to the exoskeleton can be stabilized using epoxy. In the case of a fractured carapace, prepare the exoskeletal area where the epoxy will be affixed with an abrasive material like sandpaper. Manually reduce the fracture and stabilize it with the epoxy using digital pressure (Figure 4.9). The epoxy braces can be left in place as long as needed, but healing should occur within three to four months (Smith 2012).

Figure 4.9 These images illustrate fracture repair of a horseshoe crab (Limulus polyphemus) prosoma caused by a fall from a raised, shallow tank. (a) The fracture is located on the animal's right side and extends from an area rostral and medial to the compound eye caudally through the arthrodial ligament. (b) A sandpaper wheel is used to freshen areas of the prosoma for better epoxy adherence. (c) The fracture was manually reduced and stabilized, while a suite of four epoxy bridges were placed. (d) The animal responded well to the procedure and can be seen in its tank several weeks later.

      Healing is initiated by amoebocytes, which initially form a clot, and progresses to scab formation and tissue healing. There are several kinds of cells involved in the process (Bursey 1977; Clare et al. 1990). Pluripotent cells called plasmatocytes appear to be responsible for the regeneration of tissues, like telsons, in very young animals (Clare et al. 1990).

      Krasner et al. examined various suture materials (nylon, polyglecaprone, polydioxanone, polyglycolic acid, and silk) in the telson ligament of horseshoe crabs and found that monofilament nylon produced the least amount of tissue reaction, but none of the materials were superior with regards to holding, and none of the wounds dehisced.

Insects

This is by far the largest group of invertebrates at nearly 1 million described species and possibly the most economically important. Insects are loved and despised worldwide and occupy nearly all niches, except the marine environment. They are important as a human food source in parts of the world and both sustain and destroy agricultural crops, depending on the species of insect and plant. For these reasons, they have been well studied with regards to diseases and pathology (Boucias and Pendland 1999; Cooper 2012). Probably no species has been more thoroughly studied than the domestic honeybee, Apis mellifera (Vidal‐Naquet 2012, 2015). Despite this, virtually nothing traditionally considered surgery, has been published for insects. As with other invertebrates, a fair amount of literature exists describing techniques and procedures where insects are utilized for research and modeling purposes. A 1985 study (Endo et al. 1985) describes “etherized larvae fixed on wooden beds with threads” followed by bisection of the brain and removal of the right lobe. This technique was part of a photoperiod study.

      For microsurgery, vibrating glass stylets have been used with insects (Gödde 1989). This technique is primarily used to produce very small lesions