Abstract

We describe for the first time reproductive behaviors in the Pirate Perch (Aphredoderus sayanus), a secretive nocturnal fish whose urogenital opening is positioned far anteriorally, under its throat. Some naturalists had speculated that this peculiar morphological condition might serve to promote egg transfer to the fish's branchial chamber for gill-brooding; others hypothesized that Pirate Perch spawn in the substrate of streams but offered no adaptive rationale for the odd placement of the fish's urogenital pore. Here we solve the conundrum through a combination of intensive field investigations, underwater filming, and molecular parentage analyses. We show that Pirate Perch spawn in underwater root masses, the first documentation of such nesting behavior in any species of North American fish. Female Pirate Perch thrust their heads and release their eggs into sheltered canals of these masses. Males congregate at these sites and likewise enter the narrow canals headfirst, to release sperm. Thus, the forward-shifted urogenital pore may facilitate spawning under this special nesting circumstance. We found no evidence of extended parental care. Fish formed their own canals or used burrows made by aquatic macro-invertebrates and salamanders. Genetic analyses based on three polymorphic microsatellite loci demonstrate that a total of at least five to 11 sires and dams were the parents of embryos within each of three assayed root-mass nests (of a total of 23 nests found). Males defended the oviposition sites by body-plugging canal entrances after spawning. This and more direct aggressive behaviors by males probably relate to selection pressures imposed by intense competition for fertilization success under these group-spawning conditions.

Abstract

Introduced American Bullfrogs (Rana catesbeiana) have become widely established in the Pacific Northwest over the last century and are thought to be an important predator of native amphibians throughout the western United States. The Northern Red-Legged Frog (Rana aurora aurora) and Oregon Spotted Frog (Rana pretiosa) historically coexisted in portions of the Pacific Northwest now invaded by R. catesbeiana, but R. pretiosa has declined more severely than R. a. aurora. We investigated whether microhabitat and behavioral differences that facilitate sympatric coexistence of the natives predict which species is more susceptible to predation by introduced R. catesbeiana. Our laboratory experiments demonstrate that R. catesbeiana adults prefer aquatic microhabitats, that R. pretiosa juveniles are more aquatic than R. a. aurora, and that adult R. catesbeiana consume more R. pretiosa than R. a. aurora juveniles. Mean and maximum jump distances of R. pretiosa were shorter than equally sized R. a. aurora, and the difference between these two species increased with larger frog sizes. Our examination of field survey data indicates that R. pretiosa coexist with R. catesbeiana less frequently than R. a. aurora. We conclude that R. catesbeiana is a greater threat to survival of R. pretiosa than to R. a. aurora and suggest that microhabitat use and escape abilities of native ranid frogs may be linked to this asymmetrical effect. Analysis of behavioral and microhabitat differences among related native species may be a useful tool in predicting the effects of introduced predators on amphibians and can assist in developing conservation priorities for these species.

Abstract

This study provides the first detailed description of the events at hatching for an anamniotic vertebrate egg. California Grunion are ideally suited for this study, because these fish eggs incubate fully terrestrially and delay hatching until presented with an environmental trigger. Grunion eggs can be induced to hatch on demand within a few minutes, by mechanical agitation in seawater. We suggest that the process of hatching in grunion involves an enzymatic weakening of the chorion followed by the embryo's active efforts to escape. Using a dissecting microscope, microscope camera, and digital video camera, we compared embryonic movements within the chorion prior to hatching. Then, we recorded the exact moment of hatching with digital video to identify events that occur consistently. Prior to exposure to the hatching trigger, Grunion embryos move minimally within the egg. After the hatching trigger, embryos significantly increase the amount and types of movements within the egg. The chorion distorts in a location superior to the caudal region, and fluid escapes from the egg. Embryonic activity usually culminates in a vigorous tail lash that splits the chorion open. Ultimately, usually within two minutes, the Grunion larva emerges from the chorion into its new aquatic environment.

ESTADIOS TEMPRANOS DE PECES DEL PACIFICO COLOMBIANO. Beatriz Susana Beltran-Leon and Raul Rios Herrrera. 2000. In Spanish. Instituto Nacional de Pesca y Acuicultura–INPA, Buenaventura, Colombia. ISBN Tomo I 958-9356-04-4, Tomo II 958-9356-05-2. Two volumes, consecutively paged 1–358 and 359–727. $70.00 (paperback). (Further information: B. Beltran, P.O. Box 10742, Buenaventura, Colombia;bbeltranleon@yahoo.com or on the web www.inpa.goc.co).—This book, with a title that translates into English as Early Life-History Stages of Fishes of the Colombian Pacific, is a top-quality regional larval-fish guide and an excellent contribution to the larval taxonomy and ecology of the Colombian Pacific. The region addressed

SHOREFISHES OF THE TROPICAL EASTERN PACIFIC/PECES COSTEROS DEL PACÍFICO ORIENTAL TROPICAL. D. Ross Robertson and Gerald R. Allen. 2002. Version 1. Smithsonian Tropical Research Institute, Balboa, Panama. ISBN 9962614-02-3. CD-ROM. $10.00.—This pioneering marriage of ichthyological knowledge with the rapidly evolving technology of data storage and retrieval has provided a remarkable opportunity for field and laboratory researchers. The authors, both experienced field biologists, systematists, photographers, and prolific researchers, have transformed their experience into the equivalent of a suitcase full of references and papers concerning tropical eastern Pacific shorefishes. But it is the interactive nature of data retrieval and analysis that is

Pietschichthys horridus Kharin, 1989: A Junior Synonym of Dermatias platynogaster Smith and Radcliffe, in Radcliffe, 1912 (Lophiiformes: Oneirodidae), with a Revised Key to Oneirodid Genera