APPENDIX IDENTIFICATION KEY TO STURGEONS AND PADDLEFISH OF NORTH AMERICA MARTIN HOCHLEITHNER1 AND PAUL VECSEI2 1AquaTech, Unterbrunnweg 3, Kitzbuehel, Austria 6370, E-mail: [email protected] 2Warnell School of Forest Resources, University of Georgia, Athens, Georgia 30602, USA. E- mail: [email protected] Author’s note The dichotomous key is a tool used by ichthyologists, fisheries biologists, and students for identifying unknown specimens to the level of species, genus or family. Constructed from a series of couplets, each consists of two statements describing characteristics of a particular organism or group of organisms. The reader is offered a choice between the two statements that best fits the unidentified specimen in question (Timme 1991) The statements contained in the couplets initially cover broad characteristics and become narrower or more focused as more choices become available. As the reader progresses through the couplets, the key choices are ordered from broad to narrow characteristics until only a single choice remains. If the correct or relevant couplet is applicable and the unknown specimen is included in the key, positive identification is possible. Sturgeon researchers require familiarity with the terminology used to describe sturgeon morphology. A good key should be well designed, and maintain simple but appropriate terminology. This key may be lacking in this respect; several of the rules pertaining to dichotomous keys have been broken during the creation of this key. In reality, no single sturgeon key exists that works: every key concerning Acipenser, whether worldwide or regional, has some major flaw. Our priority was to construct a key that worked, and it proved very difficult. We had to disregard the couplets of equivalent features, and structured the key so that the reader should consider couplets only until they were superseded by a new couplet. In constructing the key, we used the following criteria whenever possible: x Morphological and meristic characters that are constant. x Characteristics that are generally visible on preserved as well as live specimens. x Inclusion of osteological characters (bony plates) whenever possible. They are consistent and easy to observe or count. 315 G.T.O. LeBreton et al. (eds.), Sturgeons and Paddlefish of North America, 315–318. 2004 Kluwer Academic Publishers. Printed in the Netherlands. 316 M. HOCHLEITHNER AND P. VECSEI Skull cartilaginous, but covered by a large number of bony plates. Axial skeleton cartilaginous, vertebrae lacking centra, notochord persistent, extending into upper lobe of caudal fin. Pelvic fins abdominal without true spines. V-shaped fulcrae cover the axis of each unpaired fin: ... …...(Order: Acipenseriformes) Two Families in North America: 1 1 Body without rows of bony scutes, two small barbels (1 pair) on the underside of the rostrum anterior to the mouth, snout long and flattened (more than 70 % of the head length): ... (Family: Polyodontidae) One Species in North America: Polyodon spathula Body with five rows of bony scutes, four barbels (2 pairs) arranged in a single transverse row anterior to the mouth, snout short (less than 70 % of the head length): ... (Family: Acipenseridae) Eight Species in North America: 2 2 Snout conical with rounded edges, spiracle and pseudobranchiae present, caudal peduncle short, partly covered with bony scutes, lower lip interrupted medially and with two lobes, barbels not or slightly fimbriated: ... (Genus: Acipenser) 3 Snout spatulate with sharp edges, spiracle and pseudobranchiae absent, caudal peduncle long, fully covered with bony scutes, lower lip continous and with four lobes, barbels highly fimbriated: ... (Genus: Scaphirhynchus) 7 3 Plates present along both sides of the anal-fin base, 3 or more post-dorsal and post-anal plates (some in pairs), mouth opening usually less than 60 % of interorbital width: ... Acipenser oxyrinchus No plates at the sides of the anal-fin base, 3 or fewer post-dorsal and post-anal plates, mouth opening usually more than 60 % of interorbital width: ... 4 4 An olive-green lateral band along lateroventral surface (between lateral and ventral scutes), barbels closer to mouth and slightly fimbriated, 36 or fewer lateral scutes: ... Acipenser medirostris No olive-green lateral band between scute rows, barbels not fimbriated: ... 5 IDENTIFICATION KEY 317 5 Post-dorsal and post-anal plates absent, 5 or more pre-anal plates, 36 or more lateral scutes, 42 or more dorsal fin rays, barbels closer to the tip of the snout: ... Acipenser transmontanus Post-dorsal and post-anal plates present, 4 or less pre-anal plates: ... 6 6 Fewer than 23 anal fin rays, lateral scutes are lighter than the body background, base of barbels closer to the tip of the snout, 42 or less dorsal fin rays: ... Acipenser brevirostrum More than 23 anal fin rays, lateral scutes almost same color as the body background: ... Acipenser fulvescens 7 Dorsal fin with more than 38 rays and anal fin with more than 24 fin rays, caudal fin with more than 65 fin rays, outer-barbel length more than 1.5 times of inner barbel length, base of outer-barbels well behind inner-barbels: ... Scaphirhynchus albus Dorsal fin with less than 38 rays and anal fin with less than 24 fin rays, caudal fin with less than 65 fin rays, outer-barbel length less than 1.5 times of inner-barbel length, base of barbels nearly in one row: ... 8 8 Belly covered with large exposed bony plates, spines on the tip of the snout and between the small eyes: ... Scaphirhynchus platorhynchus Belly covered with small embedded bony plates, no spines on the tip of the snout and between the large eyes: ... Scaphirhynchus suttkusi 318 M. HOCHLEITHNER AND P. VECSEI Meristic Characters in Sturgeons and Paddlefish of North America Species DF AF DS LS VS GR poD poA prA Acipenser 30-42 19-22 7-13 21-35 6-11 22-29 1-3 1-2 2-3 brevirostrum Acipenser 35-45 25-30 9-17 29-42 7-12 25-40 1-2 1-2 1-2 fulvescens Acipenser 29-44 19-32 7-12 20-36 5-12 15-26 1-2 1-2 1-4 medirostris Acipenser 38-46 23-30 7-16 24-35 6-14 15-27 3-9 3-9 2-6 oxyrinchus Acipenser 42-52 25-32 11-14 36-48 9-12 23-36 0 0 5-9 transmontanus Scaphirhynchus 37-43 23-28 14-18 40-48 9-13 ? 8-9 7-8 4-5 albus Scaphirhynchus 29-39 18-25 13-19 38-50 9-14 ? 8-9 8-9 4-6 platorhynchus Scaphirhynchus 29-34 18-22 15-21 40-49 11-14 ? 7-9 7-8 4-6 suttkusi Polyodon ? ? 0 0 0 ? 0 0 0 spathula Abbreviations: DF = Dorsal fin rays, AF = Anal fin rays, DS = Dorsal scutes, LS = Lateral scutes, VS = Ventral scutes, GR = Gill rakers, poD = Plates between dorsal- and caudal fin, poA = Plates between anal- and caudal fin, prA = Plates between anus and anal fin; References Hochleithner M., Gessner J., 2001: The Sturgeons and Paddlefishes (Acipenseriformes) of the World: Biology and Aquaculture. AquaTech Publications, Kitzbuehel/Austria. 207 pages. Mayden R.L., Kuhajda B.R., 1996: Systematics, Taxonomy, and Conservation Status of the Endangered Alabama Sturgeon, Scaphirhynchus suttkusi Williams and Clemmer (Actinopterygii, Acipenseridae). Copeia, 2: 241-273. North J.A., Farr R.A., Vecsei P., 2002: A comparison of meristic and morphometric characters of green sturgeon Acipenser medirostris. J. Appl. Ichthyol., 18(4-6): 234-239. Scott W.B., Crossman E.J., 1973: Freshwater Fishes of Canada. Fisheries Research Board of Canada. 966 pages. Timme, S.L. 1991. How to construct and use a dichotomous key. Pages 101-110, in Tested studies for laboratory teaching. Volume 12. (C. A. Goldman, Editor). Proceedings of the 12th Workshop/Conference of the Association for Biology Laboratory Education, 218 pp Vecsei P., Charette R., Trukshin I., Maliepaard T., Hochleithner M., Lafleur Y., 2001: CITES Identification Guide - Sturgeons and Paddlefish. Environment Canada. 180 pages. Glossary Acid-base characteristics: acid (H+) and base (OH-) equivalents, often expressed as pH (negative logarithm10 of the hydrogen ion activity, in solutions.) Amphihaline: fish whose life cycle include both a freshwater and marine component. Anadromous: fish ascending rivers from the sea to breed. Anaerobic metabolism: metabolism in the absence of free oxygen. Animal pole/hemisphere: the end/half of the oocyte or early embryo containing relatively more cytoplasm and less yolk. Frequently the location of the mature germinal vesicle, and thus fertilization. The animal-vegetal axis is established maternally during oogenesis. Archenteron: the primitive gut cavity that forms within the embryo as a result of gastrulation. Arterial: P50: half-saturation value of blood, under arterial CO2 and pH conditions. Atresia: the resorption of the ovarian follicles by degenerative processes during late vitellogenesis, or before the female undergoes final maturation and spawning. Blastomeres: individual cells within an early (pre-gastrula) embryo. Blastula: a multicellular embryo that has mostly or entirely completed cleavage, but in which the large-scale movements of gastrulation have not yet begun. Blood O2 affinity: binding affinity of the blood for oxygen, expressed as P50. Breeding interval: time between consecutive breedings of individual. Chloride cells: mitochondria-rich cells (e.g., in gill tissue) that move chloride (and sodium) against their concentration gradients. Chorion: a tough protective extracellular layer surrounding the oocyte and developing embryo. Cortical reaction: the process in which the cortical alveoli fuse to the plasma membrane of the oocyte, and release their contents into the space between the plasma membrane and egg chorion. The cortical vesicles contain enzymes, structural proteins and other glycoproteins. The cortical reaction renders separation of the chorion from the plasma membrane, imparts tonicity and strengthens the chorion (‘water hardening’), and prevents fertilization by multiple sperm (‘block to polyspermy’). 319 320 GLOSSARY Cortisol: glucocorticoid hormone secreted by the interrenal gland and involved in stress response Dimorphism: the appearance of two distinct forms such as size, structure, colour, etc.