Exploring abnormal Cambrian-aged trilobites in the Smithsonian collection

Biomineralised trilobite exoskeletons provide a 250 million year record of abnormalities in one of the most diverse arthropod groups in history. One type of abnormality—repaired injuries—have allowed palaeobiologists to document records of Paleozoic predation, accidental damage, and complications in moulting experienced by the group. Although Cambrian trilobite injuries are fairly well documented, the illustration of new injured specimens will produce a more complete understanding of Cambrian prey items. To align with this perspective, nine new abnormal specimens displaying healed injuries from the Smithsonian National Museum of Natural History collection are documented. The injury pattern conforms to the suggestion of lateralised prey defence or predator preference, but it is highlighted that the root cause for such patterns is obscured by the lumping of data across different palaeoecological and environmental conditions. Further studies of Cambrian trilobites with injuries represent a key direction for uncovering evidence for the Cambrian escalation event.

Prey’s traits mediate a neotropical toad diet

B.ABSTRACTDespite the widespread occurrence of myrmecophagy in anurans it is generally unclear whether ant-specialists feed on ants opportunistically or whether they preferentially select for certain species, potentially favoring specific morphological, ecological, or nutritional traits.We flushed 105 stomachs of a lowland neotropical toad, Rhinella alata, and identified each consumed ant to species level. We used linear selectivity to calculate predator preference by comparing the abundances of consumed species to their abundances in the leaf litter community on Barro Colorado Island, Panama. We conducted multiple regression models to test whether linear selectivity or general predator preference related to seven morphological characteristics and two measurements of nutritional content.Rhinella alata preferentially harvested 24 ant species. Other species were either avoided (n=34) or were eaten opportunistically (n=26). We found that R. alata predominantly preys upon large ants that are textured with hair and/or rugosity and preference for prey did not relate to nutrition content. Rhinella alata avoided small ants even if they were hyper abundant in the environment, and preferentially ate chemically-defended and aggressive ants if they were large enough.We propose that R. alata prefers large ants because they represent a more efficient prey item in terms of predator handling time and because they are easier to see than are smaller ants. Furthermore, we hypothesize that R. alata predation attempts are more successful when prey are textured because microstructures on the tongue and prey surface may increase prey adhesion.The ant specialist R. alata is not specializing on any particular ant species but rather maximizing prey quantity over quality by only eating the largest ants, despite their scarcity in the environment.

The effects of the parasite Probopyrus pandalicola (Packard, 1879) (Isopoda, Bopyridae) on the behavior, transparent camouflage, and predators of Palaemonetes pugio Holthuis, 1949 (Decapoda, Palaemonidae)

The bopyrid isopod Probopyrus pandalicola (Packard, 1879) is a large, noticeable, hematophagous ectoparasite of palaemonid shrimps, including the daggerblade grass shrimp Palaemonetes pugio Holthuis, 1949. Bopyrids affect grass shrimp physiology and may also affect predator-prey dynamics. The purpose of this study was to determine whether the isopod affected the behavior and/or camouflage of grass shrimp, thereby altering the predation preferences of the mummichog Fundulus heteroclitus (Linnaeus, 1766). To determine whether the isopod affected predator preference through behavioral and/or camouflage alterations, paired combinations of unparasitized, parasitized, and marked shrimp were presented to mummichogs. One branchiostegite of some of the unparasitized shrimp was marked with black paint to mimic the bopyrid parasite. Mummichog predation preference and shrimp behavior immediately prior to predation events were recorded. All shrimp behavior was classified as motionless, walking, swimming, or backward thrusting. Immediately prior to predation, parasitized shrimp swam more () and backward thrusted less () than unparasitized shrimp. Mummichogs exhibited a preference for the more active shrimp (80.7% of shrimp; ), and also for the less camouflaged (parasitized or marked) shrimp (81.5% of shrimp; ) if there was no difference in shrimp behavior. Parasitized shrimp were preferentially consumed (51/85 shrimp) when paired with unparasitized shrimp (), but not with marked shrimp (). A 30-min activity budget was created for each type of shrimp both in the presence and absence of predators; neither the parasite nor marking affected their behavior over 30 min (). The major finding of this study was that P. pandalicola affected the predation preferences of F. heteroclitus by altering the behavior and/or camouflage of the grass shrimp. Parasitization alters predator-prey dynamics by decreasing the camouflage and the frequency of backward-thrusting behavior by the host when it is threatened by predation, which thereby decreases the ability of shrimp to escape from predators.

KELIMPAHAN POPULASI, PREFERENSI DAN KARAKTER KEBUGARAN MENOCHILUS SEXMACULATUS (COLEOPTERA: COCCINELLIDAE) PREDATOR KUTUDAUN PADA PERTANAMAN CABAI

This predator is efective to control population of aphids, so the aim of research was to study the field population abundance, predator preference to this prey, and fitness character of M. sexmaculatus as predator. The population fluctuation was observed at conventional and organic farming. The preference test was conducted by choice and no choice test for some types of prey. Fitness test was performed by studying its prey, the number of eggs produced and number of eggs hatched. The results showed that M. sexmaculatus population abundance was fluctuated, the abundance higher in chili cultivated conventionaly than cultivated in organic farming. But in conventional farming decreased with increasing age of chili. Preference test showed that almost all species of aphids preferred by M. sexmaculatus. Some prey species found were aphids, thrips and Neotoxoptera. Predator fitness levels showed by the longevity of females ranged 9-10 days. Oviposition period was on average five days, while the post-oviposition was two days. The number of eggs produced ranged 100-200 eggs with an average of 135.3 eggs.