Paul Sikkel - Academia.edu (original) (raw)

Papers by Paul Sikkel

Coral Reefs, 2024

highlight the importance of both dedicated and facultative cleaners as consumers of ectoparasites... more highlight the importance of both dedicated and facultative cleaners as consumers of ectoparasites and show that their role is unlikely to be supplanted by non-cleaner consumers. Furthermore, we suggest that different cleaner species act as complementary rather than redundant specialists.

Acanthurids (surgeonfishes) are an abundant and diverse group of herbivorous fishes on coral reef... more Acanthurids (surgeonfishes) are an abundant and diverse group of herbivorous fishes on coral reefs. While their contribution to trophic linkages and dynamics in coral reef systems has received considerable attention, the role of linkages involving their parasites has not. As both consumers of fish tissue and prey to microcarnivores, external parasites may play a significant role in trophic transfer between primary consumers (and hence their predominantly algae-based diet) and the broader coral reef community. Stable isotope analysis is a common tool for studying trophic linkages which can be used for studies involving parasites. We examined the stable isotope ecology (13C and 15N) of copepod (Caligus atromaculatus) and monogenean (Neobenedenia sp.) ectoparasites collected from two species of Caribbean acanthurids (Acanthurus coeruleus and Acanthurus bahianus). There were significant intraspecific differences in isotope discrimination factors between parasites collected from the two ...

Parasites are an integral part of coral reef ecosystems due to their influences on population dyn... more Parasites are an integral part of coral reef ecosystems due to their influences on population dynamics, biodiversity, community structure, and food web connectivity. The Phylum Apicomplexa contains ubiquitous animal associates including the causative agents of globally important human diseases such as malaria and cryptosporidiosis. Despite their ubiquity, little is known about the biology, ecology, or distribution of these microorganisms in natural animal populations. In the US Virgin Islands, the dusky damselfish (Stegastes adustus) had a high but variable incidence of a Haemohormidium-like blood apicomplexan among 30 sites sampled. Microscopic analyses of blood smears allowed us to group these fish as infected, having low intensity infections, or uninfected. Regression analyses detected no significant differences in the condition indices (expressed as length–mass ratio). However, infection was clearly associated with potentially extremely high leukocyte counts among infected S. ad...

Copula sivickisi is a small cubozoan most noted for its sexual dimorphism, courtship behavior, an... more Copula sivickisi is a small cubozoan most noted for its sexual dimorphism, courtship behavior, and the presence of adhesive pads on its exumbrellar surface, all of which are unique to the family. This species has only been previously document-ed from the Indo West-Pacific tropical region. We report the first occurrence of C. sivickisi from the tropical Western Atlantic Ocean. Two males were collected by night lighting in near shore wa-ters in Graham's Harbor, adjacent to the Gerace Research Centre on San Salvador Island, Bahamas in June 2010. The presence of this species in the Western Atlantic poses the following ques-tions: Does this occurrence indicate a historically isolated cryptogenic population, a truly circum-tropical distribution, or is this a result of a recent anthropogenic introduction? INTRODUCTION

Oceans

Extreme warming events that contribute to mass coral bleaching are occurring with increasing regu... more Extreme warming events that contribute to mass coral bleaching are occurring with increasing regularity, raising questions about their effect on coral reef ecological interactions. However, the effects of such events on parasite-host interactions are largely ignored. Gnathiid isopods are common, highly mobile, external parasites of coral reef fishes, that feed on blood during the juvenile stage. They have direct and indirect impacts on their fish hosts, and are the major food source for cleaner fishes. However, how these interactions might be impacted by increased temperatures is unknown. We examined the effects of acute temperature increases, similar to those observed during mass bleaching events, on survivorship of gnathiid isopod juveniles. Laboratory experiments were conducted using individuals from one species (Gnathia aureamaculosa) from the Great Barrier Reef (GBR), and multiple unknown species from the central Philippines. Fed and unfed GBR gnathiids were held in temperature...

Journal of Crustacean Biology

Parasites play significant roles in the function of ecosystems and can make up a large proportion... more Parasites play significant roles in the function of ecosystems and can make up a large proportion of overall biomass. Yet, fundamental aspects of their ecology are often understudied relative to other organisms. Gnathiid isopods are the primary ectoparasites of fishes in coral reef ecosystems. While some studies have investigated their host-detection capabilities, the means by which they seek hosts are largely unknown. Gnathiids are benthic and live on the bottom, and all collection efforts involving live hosts have thus far involved traps set at or near the reef substrate. We investigated the distance gnathiids will travel vertically in the water column to attach to a fish host. The majority of gnathiids collected were at or less than 1 m above the reef substrate, and gnathiids were collected in serially diminishing numbers at 2 and 3 m above it. No gnathiids were collected from any fish hosts set more than 3.5 m above the reef substrate. Results suggest that gnathiids will activel...

Scientific Reports

Severe disturbances can substantially alter eco-evolutionary processes and dynamics. While the im... more Severe disturbances can substantially alter eco-evolutionary processes and dynamics. While the impacts of catastrophic events on the biophysical attributes of communities are sometimes assessed, their effects on the genetic patterns of species remain poorly understood. To characterize how severe disturbances impact species at the molecular level, we examined the effects of the most energetic North Atlantic hurricane season in 50 years on the genetic diversity and structure of a dispersal-limited isopod, Gnathia marleyi. We sequenced a portion of the cytochrome oxidase I gene for 432 gnathiids, collected from six localities, ranging from western Puerto Rico to St John, US Virgin Islands. Importantly, multiple years of pre-hurricane sample collection allowed us to characterize temporal genetic patterns under undisturbed conditions and detect the changes subsequent to the 2017 hurricanes. Our results revealed no change to genetic diversity or structure for the years prior to the 2017 h...

Biological and Chemical Oceanography Data Management Office

African Journal of Marine Science

Zootaxa

A new species of gnathiid was collected in June-August 2008 and 2009 from various sites in the Ea... more A new species of gnathiid was collected in June-August 2008 and 2009 from various sites in the Eastern Caribbean. Third stagepranizae taken from fish hosts were maintained in fresh sea water until their moult into males or females. Distinctive features ofthe adult male cephalosome include a produced frontal border with conical superior fronto-lateral processes and a slightly sunkeninferior conical medio-frontal process. The male mandible is 0.8 times the length of cephalosome with 10 to 11 processes ondentate blade. The adult female has a rectangular cephalosome with convex lateral margins, 1.2 times as wide as long with noparaocular ornamentation. The female frontal border is broadly rounded, produced and slightly concave anteriorly. The third stage praniza is characterised by a mandible with 8 large, triangular teeth, directed backwardly and 2 small teeth at the tip.

Journal of the Marine Biological Association of the United Kingdom

Gnathiid isopods are one of the most common fish ectoparasites, and are found in both temperate a... more Gnathiid isopods are one of the most common fish ectoparasites, and are found in both temperate and tropical oceans. On coral reefs, gnathiids are most active at dusk and dawn, and contribute significantly to trophic dynamics, as they are a prey resource for cleaner fish and parasitize numerous fishes. Gnathiids also inhabit temperate intertidal waters, but their activity patterns and contribution to intertidal trophic dynamics remain unstudied. To provide the first ecological data on temperate intertidal gnathiid activity patterns, 172 gnathiid-free Clinus superciliosus were set in an intertidal system in Tsitsikamma National Park, South Africa, during early morning, morning, afternoon, early evening, and evening, high and low tide, and within the inter- and infra-tidal zone to examine gnathiid infestation levels. After exposure, gnathiids from each fish were identified to the species level, counted, and their developmental stage was recorded. All gnathiids were identified as Gnath...

Marine Ecology Progress Series