SUMMARYMangrove rivulus (Kryptolebias marmoratus) are small fusiform teleosts (Cyprinodontiformes) with the ability to locomote on land, despite lacking apparent morphological adaptations for terrestrial movement. Rivulus will leave their aquatic habitat for moist, terrestrial environments when water conditions are poor, or, as we show here, to capture terrestrial insects. Specimens were conditioned to eat pinhead crickets on one side of their aquaria. After 2weeks of conditioning, a barrier with a slope of 15deg was partially submerged in the middle of the tank, forcing the fish to transition from water to land and back into water in order to feed. Kinematics during the transition were recorded using Fastec high-speed video cameras (125-250framess -1 ). Videos were analyzed using Didge and ImageJ software programs. Transition behaviors were characterized and analyzed according to their specific type. Body oscillation amplitude and wave duration were quantified for movements along the substrate, along with initial velocity for launching behaviors. Kryptolebias marmoratus used a diverse suite of behaviors to transition from water to land. These behaviors can be categorized as launches, squiggles and pounces. Prey were captured terrestrially and brought underwater for consumption. Kryptolebias marmoratus's suite of behaviors represents a novel solution to non-tetrapodal terrestrial transition, which suggests that fishes may have been able to exploit land habitats transiently, without leaving any apparent evidence in the fossil record. Supplementary material available online at

We used 32 polymorphic microsatellite loci to investigate how a mixed-mating system affects population genetic structure in Central American populations (N = 243 individuals) of the killifish Kryptolebias marmoratus (mangrove rivulus), 1 of 2 of the world's only known self-fertilizing vertebrates. Results were also compared with previous microsatellite surveys of Floridian populations of this species. For several populations in Belize and Honduras, population structure and genetic differentiation were pronounced and higher than in Florida, even though the opposite trend was expected because populations in the latter region were presumably smaller and highly selfing. The deduced frequency of selfing (s) ranged from s = 0.39-0.99 across geographic locales in Central America. This heterogeneity in selfing rates was in stark contrast to Florida, where s > 0.9. The frequency of outcrossing in a population (t = 1 - s) was tenuously correlated with local frequencies of males, suggesting that males are one of many factors influencing outcrossing. Observed distributions of individual heterozygosity showed good agreement with expected distributions under an equilibrium mixed-mating model, indicating that rates of selfing remained relatively constant over many generations. Overall, our results demonstrate the profound consequences of a mixed-mating system for the genetic architecture of a hermaphroditic vertebrate.

The goal of the present study was to determine which sensory cues the mangrove rivulus Kryptolebias marmoratus, a quasi‐amphibious, hermaphroditic fish, uses to orient in an unfamiliar terrestrial environment. In a laboratory setting, K. marmoratus were placed on a terrestrial test arena and were provided the opportunity to move toward reflective surfaces, water, dark colours v. light colours, and orange colouration. Compared with hermaphrodites, males moved more often toward an orange section of the test arena, suggesting that the response may be associated with camouflage or male–male competition, since only males display orange colouration. Younger individuals also moved more often toward the orange quadrant than older individuals, suggesting age‐dependent orientation performance or behaviour. Sloped terrain also had a significant effect on orientation, with more movement downhill, suggesting the importance of the otolith‐vestibular system in terrestrial orientation of K. marmoratus. By understanding the orientation of extant amphibious fishes, we may be able to infer how sensory biology and behaviour might have evolved to facilitate invasion of land by amphibious vertebrates millions of years ago.

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Aquatic C-start escape responses in teleost fishes are driven by a wellstudied network of reticulospinal neurons that produce a motor pattern of simultaneous contraction of axial muscle on the side of the body opposite the threatening stimulus, bending the fish into the characteristic C shape, followed by a traveling wave of muscle contraction on the contralateral side that moves the fish away from the threat. Superficially, the kinematics of the terrestrial tail-flip resemble the C-start, with the anterior body rolling up and over the tail into a tight C shape, followed by straightening as the fish launches off of the caudal peduncle into ballistic flight. We asked whether similar motor control is used for both behaviors in the amphibious mangrove rivulus, Kryptolebias marmoratus. Fine-wire bipolar electrodes were percutaneously inserted into repeatable paired axial locations in five individual fish. Electromyograms synchronized with high-speed video were made of aquatic C-starts, immediately followed by terrestrial tail-flips. Tail-flips took longer to complete than aquatic escapes; correspondingly, muscles were activated for longer durations on land. In the tail-flip, activity was seen in contralateral posterior axial muscle for an extended period of time during the formation of the C shape, likely to press the caudal peduncle against the ground in preparation for launch. Tail-flips thus appear to be produced by modification of the motor pattern driving the aquatic C-start, with differences consistent with the additional requirement of overcoming gravity.

Surfperches are marine fishes that occupy nearshore habitats along the California coast. Morphology was analyzed to determine if there were differences among 19 preserved species. Principal components analysis (PCA) was used to reduce the dimensionality of the data. Morphological differences occurred among the 19 species. ANOVA revealed a habitat effect on PC2, which described the angle of attachment of the pectoral fin. Pearson correlation revealed that genetic relatedness decreased with increasing morphological differences on PC1, which described aspect ratio and body ratio. Based on PC2, four species were selected to conduct experiments on their swimming performance. U crit and fin beat frequency were measured in a flume to assess speed; flexibility was assessed via the body bending coefficient and the C-start escape response. Species differences were observed in all swimming performance variables, yet there were no tradeoffs in swimming fast versus maneuverability. Morphology seems to describe only part of the story. v ACKNOWLEDGEMENTS I would like to thank my advisor Dr. Lara Ferry-Graham for her guidance and intellectual support throughout my tenure at Moss Landing Marine Labs. I would also like to thank the rest of my thesis committee, Dr. Gregor Cailliet and Dr. Michael Graham, for their professional assistance regarding field and laboratory work, along with many conversations about statistics, life, or anything else. I especially want to acknowledge the Ecomorphology lab, Ichthyology lab, and BEERPIGs for their tremendous support with field and lab work, listening to practice talks, and always being a great sounding board. Dave Catania at the California Academy of Sciences assisted me with obtaining preserved specimens from the Ichthyology collections and Dr. Giacomo Bernardi shared his phylogenetic data with me. Joe Welsh and Manny Ezcurra from the Monterey Bay Aquarium assisted with field help and husbandry issues for surfperches. Christina Slager from Aquarium of the Bay donated a pile surfperch for the swimming performance experiments. Larry Young of SJSU helped me with the IACUC reports. This study was supported by funds from the Signe Lundstrom Memorial Scholarship, Packard Research and Travel Award, C.F. and L.V. Burmahln Scholarship, and NSF Grant CAA-0641286 to Dr. Lara Ferry-Graham. I would also like to acknowledge the many students who assisted me in the field collecting fishes and in the laboratory. Thanks to my friends and family who supported me throughout my time here at MLML.