Laboratory Observations of Reproduction in the Deep-Water Zoarcids Lycodes cortezianus and Lycodapus mandibularis (Teleostei: Zoarcidae).

v. ill. 23 cm.QuarterlyThe first observations of reproduction and associated behaviors in captive bigfin eelpout, Lycodes cortezianus, and pallid eelpout, Lycodapus mandibularis, are reported here. One Lycodes cortezianus pair produced 13 transparent and negatively buoyant eggs that were approximately 6 mm in diameter. These were laid on a hydroid-covered rock. The development period was about 7 months, and the young that emerged were approximately 2 cm in total length. An additional captive pair also exhibited mating behavior as the male repeatedly nudged the female and the pair produced a burrow under a sponge; however the male died before any mating. Two gravid female Lycodapus mandibularis were captured and laid between 23 and 46 eggs that were about 4 mm in diameter. These were released on the sandy substrate after the females moved the sand about the tank, and the eggs were negatively buoyant. These eggs were all unfertilized. Additional burrowing behavior was observed from other captive individuals, but no eggs were subsequently produced. Taken together, our observations suggest that burrowing or use of other protective structures is a reproductive behavior of central importance to zoarcids. Contrary to some earlier hypotheses, even midwater species likely return to the sediment to burrow and/or deposit eggs. This behavior means that field data regarding reproduction in this family will continue to be difficult to obtain, and the contribution of further study in laboratory situations should not be underestimated

Prey capture in long-jawed butterflyfishes (Chaetodontidae): the functional basis of novel feeding habits

Several species of butterflyfishes (Chaetodontidae) possess extremely elongate jaws, and feed mostly by probing the benthos and biting off pieces of attached invertebrates. In contrast, Forcipiger longirostris, the longest-jawed chaetodontid, exhibits a novel pattern of prey use, feeding almost exclusively on small caridean shrimp, a mobile and highly elusive prey type that lives within the structure of coral reefs. We explored the functional basis of this novel pattern of prey use by comparing prey capture kinematics in this and four other butterflyfish species, including two other species that possess elongate jaws. High speed video recordings of feeding events on live adult brine shrimp were analyzed from individuals of five species: Forcipiger longirostris, F. flavissimus, Chelmon rostratus, Heniochus acuminatus, and Chaetodon xanthurus. We focused on a comparison among species of the relative contribution of “suction”, measured as the amount of movement of the prey toward the predator’s mouth, and “ram”, measured as the distance moved by the predator toward the prey during the strike. All five species utilized a combination of suction and ram while feeding on brine shrimp. The contribution of suction did not differ significantly among species. However, F. longirostris exhibited a ram contribution to the strike that was more than twice that seen in any of the other species, permitting this species to initiate strikes from the greatest initial predator-prey distance. F. longirostris is known to possess a major structural novelty in the feeding mechanism that permits anterior movement of the entire jaw apparatus. The ability of this species to feed successfully on elusive prey appears to be related to exceptional jaw protrusion, resulting in greater use of ram during prey capture. This ability to protrude long, slender jaws toward the prey may allow it to move the jaws without detection within close enough proximity of the prey to then permit the effective use of suction. The use of extensive ram in this manner by small-mouthed fishes may be more widespread than previously thought

Modulation of prey capture kinematics in the cheeklined wrasse Oxycheilinus digrammus (Teleostei: Labridae)

The ability to modulate prey capture behaviors is of interest to organismal biologists as it suggests that predators can perceive features of the prey and select suitable behaviors from an available repertoire to successfully capture the item. Thus, behavior may be as important a trait as morphology in determining an organism’s diet. Using high-speed video, we measured prey capture kinematics in three cheeklined wrasse, Oxycheilinus digrammus. We studied the effects of three experimental prey treatments: live fish, dead prawn suspended in the water column, and dead prawn pieces anchored to the substrate in a clip. Live prey elicited significantly more rapid strikes than dead prey suspended in the water column, and the head of the predator was expanded to significantly larger maxima. These changes in prey capture kinematics suggest the generation of more inertial suction. With greater expansion of the head, more water can be accelerated into the buccal cavity. The attached prey treatment elicited strikes as rapid as those on live prey. We suggest that the kinematics of rapid strikes on attached prey are indicative of attempts to use suction to detach the prey item. More rapid expansion of the buccal or mouth cavity should lead to higher velocities of water entering the mouth and therefore to enhanced suction. Further modulation in response to the attached prey item, such as clipping or wrenching behaviors, was not observed

Evolution and mechanics of long jaws in butterflyfishes (Family Chaetodontidae)

We analyzed the functional morphology and evolution of the long jaws found in several butterflyfishes. We used a conservative reanalysis of an existing morphological dataset to generate a phylogeny that guided our selection of seven short- and long-jawed taxa in which to investigate the functional anatomy of the head and jaws: Chaetodon xanthurus, Prognathodes falcifer (formerly Chaetodon falcifer), Chelmon rostratus, Heniochus acuminatus, Johnrandallia nigrirostris, Forcipiger flavissimus, and F. longirostris. We used manipulations of fresh, preserved, and cleared and stained specimens to develop mechanical diagrams of how the jaws might be protruded or depressed. Species differed based on the number of joints within the suspensorium. We used high-speed video analysis of five of the seven species (C. xanthurus, Chel. rostratus, H. acuminatus, F. flavissimus, and F. longirostris) to test our predictions based on the mechanical diagrams: two suspensorial joints should facilitate purely anteriorly directed protrusion of the lower jaw, one joint should allow less anterior protrusion and result in more depression of the lower jaw, and no joints in the suspensorium should constrain the lower jaw to simple ventral rotation around the jaw joint, as seen in generalized perciform fishes. We found that the longest-jawed species, F. longirostris, was able to protrude its jaws in a predominantly anterior direction and further than any other species. This was achieved with little input from cranial elevation, the principal input for other known lower jaw protruders, and is hypothesized to be facilitated by separate modifications to the sternohyoideus mechanism and to the adductor arcus palatini muscle. In F. longirostris the adductor arcus palatini muscle has fibers oriented anteroposteriorly rather than medial-laterally, as seen in most other perciforms and in the other butterflyfish studied. These fibers are oriented such that they could rotate the ventral portion of the quadrate anteriorly, thus projecting the lower jaw anteriorly. The intermediate species lack modification of the adductor arcus palatini and do not protrude their jaws as far (in the case of F. flavissimus) or in a purely anterior fashion (in the case of Chel. rostratus). The short-jawed species both exhibit only ventral rotation of the lower jaw, despite the fact that H. acuminatus is closely related to Forcipiger

Prey processing in chimaeroid fishes

Holocephalans are uniquely derived for durophagy: the upper jaw is fused to the neurocranium (holostyly), and all chimaeriform holocephalans, extinct and extant, possess tooth plates. Yet, for the three extant families, authors have posited that there has been a gradual transition away from a reliance on crushing benthic prey. The Callorhynchidae (Callorhynchus) are the most like ancestral chimaeriforms in their morphology. However, the Chimaeridae (Hydrolagus and Chimaera) are described as being less suited for crushing, and more reliant on suction prey capture. We set out to quantify differences in morphology and performance between these two chimaeriform groups, and specifically to test the hypothesis that Callorhynchus is capable of processing harder prey than Hydrolagus or Chimaera. Cranial and muscular data were collected from a size range (~10 individuals) of Callorhynchus callorhynchus, Hydrolagus colliei, and Chimaera monstrosa. A PCA on external head measurements suggested that there are differences in head shape, but contrary to predictions, Chimaera was different from Callorhynchus and Hydrolagus. However, MANCOVA, used to compare estimated bite forces among the three species, with head width as a covariate, revealed that Callorhynchus tended to differ from Hydrolagus and Chimaera. Additional statistical exploration of the cranial and muscular variables used to generate bite force estimates further supported such performance differences. Interestingly, CT scans of Callorhynchus and Hydrolagus revealed only subtle differences in the amount of skeletal calcification (reinforcement), which was slight in both species. Further, Callorhynchus appears to possess some red adductor musculature, which, if confirmed, yields significantly lower bite force estimates. Thusly, it remains unclear if the chimaeroid feeding paradigm is supported

Extremely fast prey capture in pipefish is powered by elastic recoil

The exceptionally high speed at which syngnathid fishes are able to rotate their snout towards prey and capture it by suction is potentially caused by a catapult mechanism in which the energy previously stored in deformed elastic elements is suddenly released. According to this hypothesis, tension is built up in tendons of the post-cranial muscles before prey capture is initiated. Next, an abrupt elastic recoil generates high-speed dorsal rotation of the head and snout, rapidly bringing the mouth close to the prey, thus enabling the pipefish to be close enough to engulf the prey by suction. However, no experimental evidence exists for such a mechanism of mechanical power amplification during feeding in these fishes. To test this hypothesis, inverse dynamical modelling based upon kinematic data from high-speed videos of prey capture in bay pipefish Syngnathus leptorhynchus, as well as electromyography of the muscle responsible for head rotation (the epaxial muscle) was performed. The remarkably high instantaneous muscle-mass-specific power requirement calculated for the initial phase of head rotation (up to 5795 W  kg−1), as well as the early onset times of epaxial muscle activity (often observed more than 300 ms before the first externally discernible prey capture motion), support the elastic power enhancement hypothesis

What Can Professional Scientific Societies Do to Improve Diversity, Equity, and Inclusion: A Case Study of the American Elasmobranch Society

Scientific professional societies are reviewing diversity, equity, and inclusion (DEI) practices and policies in response to recent calls for much-needed change. Organizations like scientific professional societies contribute to establishing disciplinary norms, and can influence the diversity of disciplinary workforces in multiple ways through both action and inaction. This paper examines these issues using the American Elasmobranch Society (AES), a medium-sized professional scientific society, as a case study. It consists of three parts: (1) an analysis of the demographics of AES members, leaders, and award winners; (2) an evaluation of a diversity initiative created by the society which includes a survey of program alumni focusing on potential improvements to the program; and (3) a synthesis of recommendations of steps that AES and similarly sized societies can take to better support DEI goals. AES’s membership in recent years is more than half women, but 71.5% of all leadership positions in the Society’s history (including all but two Presidents) have been held by men since the society was founded in 1983. AES’s membership has significantly fewer Black/African-American members than the United States scientific workforce overall, with just 1 member out of over 400 identifying as Black in 2019, and 86.6% of Society leadership positions have been held by white-presenting members. The Society’s diversity initiative has led to some limited professional benefits for awardees, but could benefit from additional resources and support to enact suggested expansions and improvements. We provide a series of actionable recommendations that will make the annual meetings of societies like AES, and the field of chondrichthyan science, safer and more inclusive