Sull' apparato genitale maschile diReticulitermes

Riassunto Si è studiata la struttura dell'apparato genitale maschile negli alati di 5 specie diReticulitermes: lucifugus, flavipes, hageni, tibialis, hesperus.Inlucifugus si è anche considerato il grado di funzionalità dell'apparato genitale in caste diverse.

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Summary Male genital apparatus morphology and functional activity have been studied in winged specimens ofReticulitermes: lucifugus Rossi,flavipes Kollar,hageni Banks,tibialis Banks,hesperus Banks; forlucifugus also specimens of other castes and stages have been considered.

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Résumé La morphologie et la fonction de l'appareil génital masculin ont été étudiées sur des exemplaires ailés deReticulitermes: lucifugus Rossi,flavipes Kollar,hageni Banks,tibialis Banks,hesperus Banks; pourlucifugus, on a considéré aussi des exemplaires d'autres castes stades.

     

Phylogenetic analyses of mtDNA sequences corroborate taxonomic designations based on cuticular hydrocarbons in subterranean termites

Cuticular hydrocarbons (CHCs) are valuable characters for the analysis of cryptic insect species with few discernible morphological characters. Yet, their use in insect systematics, specifically in subterranean termites in the genus Reticulitermes (Isoptera: Rhinotermitidae), remains controversial. In this paper, we show that taxonomic designations in Reticulitermes from California (USA) suggested in light of differences among CHC phenotypes are corroborated by phylogenetic analyses using mtDNA sequences. Analyses based on CHC phenotypes and supported, in part, by behavioral and ecological differences have suggested the presence of more species than the two currently recognized: R. hesperus Banks and R. tibialis Banks. We analyze a 680 base pair fragment of the mitochondrial DNA cytochrome oxidase (COII) gene from 45 new (21 collection localities) and two previously recorded samples of Reticulitermes from California using parsimony and maximum likelihood methods. Both methods result in trees with highly similar topologies. Bootstrapping indicates support for six clades of Reticulitermes, and corroborates groupings based on cuticular hydrocarbons. One of the clades, R. hesperus, is already recognized in California, while four clades appear to be previously undescribed taxa. Although identification of the final clade is inconclusive, it includes a sample putatively identified as R. tibialis. Therefore, using phylogenetic analyses we corroborate chemical characters used to identify taxa, associate a chemical phenotype with a previously described species, and provide additional support for undescribed taxa of Reticulitermes.     

Instar sizes,life cycles,and food habits of five Rhyacophila (Trichoptera: Rhyacophilidae) species from the Appalachian Mountains of South Carolina,U.S.A.

The larval head widths at each instar, life cycles, and food habits of late instars were determined for five species of Rhyacophila from two Appalachian mountain streams in South Carolina, U.S.A. Rhyacophila acutiloba Morse & Ross was univoltine with two cohorts, one emerging in the spring and another presumably emerging in early autumn. Rhyacophila fuscula (Walker), R. nigrita Banks, and R. carolina Banks were apparently multicohort, univoltine species with extended flight periods. Rhyacophila minor Banks was univoltine with a spring emergence. All species were predaceous and consumed mainly Plecoptera nymphs and Trichoptera larvae.     

Agonistic behavior correlated with hydrocarbon phenotypes in dampwood termites,Zootermopsis (Isoptera: Termopsidae)

The dampwood termite genus ZootermopsisEmerson contains three recognized species with four distinct and consistent hydrocarbon phenotypes. Agonistic behaviors among nonreproductive insects from colonies of the same and different hydrocarbon phenotypes were observed in the laboratory. Various combinations of soldier versus nymphs, pseudergate versus pseudergate, and soldier versus soldier encounters were used in experimental trials. Soldiers or pseudergates seldom attack individuals of the same hydrocarbon phenotype. Z. angusticollis(Hagen) (phenotype II) is typically aggressive toward phenotype III of Z. nevadensis(Hagen) but not always aggressive against phenotype I of Z. nevadensis.The variation in response is dependent on which castes are placed in the bioassay arena: soldier versus soldier bouts result in consistent aggression, while pseudergate versus pseudergate or soldier versus nymphs contacts do not. Both pseudergates and soldiers of Z. laticeps(Banks) (phenotype IV) respond agonistically toward the other three phenotypes: Z. angusticollis (II) and Z. nevadensis(I and III). Although hydrocarbon phenotypes I and III, both Z. nevadensis,are morphologically indistinguishable, agonistic behavioral responses between phenotype I and phenotype III are not equivalent to I versus I or III versus III behavioral responses. The I versus III engagements, regardless of the castes involved, display a greater proportion of avoidance and aggressive responses than I or III intraphenotype encounters. We interpret the lack of avoidance or aggressive behavior within each of the two phenotypes of Z. nevadensisand the significant avoidance and aggressive behavior between phenotypes as definite evidence of discrimination between disparate hydrocarbon phenotypes. These agonistic bioassays along with data on distinct hydrocarbon patterns and geographic distributions serve as the basis for creating two subspecies of Z. nevadensis: Z. n. nevadensis(Hagen) and Z. n. nuttingiHaverty and Thorne, ssp. nov.     

Effect of different isolates of Beauveria bassiana on field populations of Lygus hesperus

Lygus hesperus (Knight) (Hemiptera: Miridae) is a particularly damaging pest of many crops in the Western United States. Current control tactics are chemically based and there is some concern over resistance building up in populations. Based on previous laboratory studies conducted in California and Mississippi, USA, two new isolates of the entomopathogenic fungus Beauveria bassiana (Balsamo) Vuillemin (Deuteromycotina: Hyphomycetes) were selected for field-testing against L. hesperus in California. Alfalfa plots were treated with one of three isolates of B. bassiana (a commercial isolate, an isolate from CA (WTPB2) or an isolate from MS (TPB3)) or the chemical pesticide Warrior T. More than 75% of the adults collected from plots 3 days after application with B. bassiana were infected but no differences in percentage infection occurred among fungal treatments. In addition, approximately 30% of the insects collected from control plots or plots treated with Warrior T were also infected. PCR analysis using SSR markers revealed that the isolate causing most of the infections in fungus treated plots was the isolate applied. A mix of infections was found in control plots and plots treated with Warrior T. Despite high levels of infection, no significant reductions of adult populations occurred until 10–14 days after application when plots treated with Warrior T or B. bassiana had about half the numbers of adult L. hesperus as the control plots.     

Phylogenetic identification of symbiotic protists of five Chinese Reticulitermes species indicates a cospeciation of gut microfauna with host termites

Symbiotic protists play important roles in the wood digestion of lower termites. Previous studies showed that termites generally possess host-specific flagellate communities. The genus Reticulitermes is particularly interesting because its unique assemblage of gut flagellates bears evidence for transfaunation. The gut fauna of Reticulitermes species in Japan, Europe, and North America had been investigated, but data on species in China are scarce. For the first time, we analyzed the phylogeny of protists in the hindgut of five Reticulitermes species in China. A total of 22 protist phylotypes were affiliated with the family Trichonymphidae, Teranymphidae, Trichomonadidae, and Holomastigotoididae (Phylum Parabasalia), and 45 protist phylotypes were affiliated with the family Pyrsonymphidae (Phylum Preaxostyla). The protist fauna of these five Reticulitermes species is similar to those of Reticulitermes species in other geographical regions. The topology of Trichonymphidae subtree was similar to that of Reticulitermes tree. All Preaxostyla clones were affiliated with the genera Pyrsonympha and Dinenympha (Order Oxymonadida) as in the other Reticulitermes species. The results of this study not only add to the existing information on the flagellates present in other Reticulitermes species but also offer the opportunity to test the hypotheses for the coevolution of symbiotic protists with their host termites.     

Identification ofMuscidifuraxspp., Parasitoids of Muscoid Flies, by Composition Patterns of Cuticular Hydrocarbons

Gas chromatographic analysis of cuticular hydrocarbons ofMuscidifuraxspp. adult females revealed species-specific patterns of composition that allowed identification ofMuscidifurax raptorGirault and Sanders,Muscidifurax zaraptorKogan and Legner, andMuscidifurax raptorellusKogan and Legner. A total of 18 components, all C29–C37 alkanes and methylalkanes, accounted for over 90% of the total cuticular hydrocarbons for all three species.Muscidifurax zaraptorwas characterized by a high ratio (11.9) of 3-MeC₃₁:internal Me₂C₃₅'s, whereas this ratio was <3 for the other species.Muscidifurax raptorelluswas characterized by a low (<1) 3-MeC₃₁:3,7,15-Me₃C₃₇ratio compared with ratios of 3.1 and 6.3 for these components inM. raptorandM. zaraptor, respectively. Three populations ofM. raptorelluscould be distinguished from one another based on two other component ratios (5- and 7-MeC31:3MeC32, 5- and 7-MeC31:3,7- to 3,15-Me₂C₃₃) with either 100% (Nebraska population) or 90% (Chilean and Peruvian populations) certainty. Comparison ofM. raptorcolonies established from five different locations (Florida, France, Germany, Brazil, Hungary) indicated that the hydrocarbon pattern was highly conserved in this species. A dichotomous key to species based on ratios of cuticular hydrocarbon components unambiguously classified the 50 samples ofMuscidifuraxspp. used to construct the key, plus five additional samples from different geographic locations.     

Cuticular profiles and mating preference in a slave-making ant

The remarkable ability of slave-making ants to integrate chemically in the colonies of their host species makes them useful model systems for investigating the role of cuticular hydrocarbons in chemical recognition. The purpose of our study was to examine the influence of the rearing host species on the cuticular hydrocarbon profile and on the mating behaviour of sexuals of the slave-making ant Chalepoxenus muellerianus. Sexuals from a population parasitizing exclusively the host species Temnothorax unifasciatus were reared in the laboratory either with their natural host or another potential host species, Temnothorax recedens. C. muellerianus males reared with T. unifasciatus investigated and mounted female sexuals reared with the same host significantly more often than female sexuals reared with T. recedens. Similarly, C. muellerianus males reared with T. unifasciatus discriminated against female sexuals from natural T. recedens colonies. Males experimentally or naturally reared with T. recedens did not clearly discriminate between female sexuals reared by the two host species and only rarely engaged in mating attempts with either type of female sexuals. Chemical analyses showed that host species affect the chemical profile of C. muellerianus sexuals and vice versa. Our findings indicate that cuticular hydrocarbons might be important in the mating success of this ant species. Received 21 June 2006; revised 20 February 2007; accepted 1 March 2007.     

Taxonomy and phylogeny of north mediterranean <Emphasis Type="Italic">Reticulitermes</Emphasis> termites (Isoptera,Rhinotermitidae): a new insight

Summary The molecular characterisation of 18 new populations of Reticulitermes is here presented for COII and 16S genes; results are elaborated and compared to all available ones, at distances and gene trees (Maximum Parsimony, Maximum likelihood, Bayesian analysis) levels. Within the R. lucifugus complex, a subspecific rank of differentiation appears tenable for Italian (R. lucifugus lucifugus, R. lucifugus corsicus) and European (R. lucifugus banyulensis, R. lucifugus grassei) taxa; a subspecific differentiation emerges also for the Sicilian samples. The existence of two different entities in the area formerly defined as inhabited by R. balkanensis is demonstrated; The north-eastern Italian Reticulitermes sp. is found to be more widely distributed in northern and south-eastern Italy and shows a close relationship to the sample from Peloponnese; the GenBank sample from continental Greece, on the contrary, appears more related to other eastern taxa such as R. lucifugus from Turkey and R. clypeatus from Israel; the distribution and differentiation of eastern Reticulitermes taxa are explained through the role that southern Balkans should have played as glacial refuge. Present data also evidences instances of anthropic involvement in taxa distribution; for one of these, the importation of at least a family group is taken into account.Received 8 May 2003; revised 1 July and 28 August 2003; accepted 24 September 2003.     

GENETICS OF INCIPIENT SPECIATION IN DROSOPHILA MOJAVENSIS. III. LIFE‐HISTORY DIVERGENCE IN ALLOPATRY AND REPRODUCTIVE ISOLATION

We carried out a three‐tiered genetic analysis of egg‐to‐adult development time and viability in ancestral and derived populations of cactophilic Drosophila mojavensis to test the hypothesis that evolution of these life‐history characters has shaped premating reproductive isolation in this species. First, a common garden experiment with 11 populations from Baja California and mainland Mexico and Arizona reared on two host species revealed significant host plant X region and population interactions for viability and development time, evidence for host plant adaptation. Second, replicated line crosses with flies reared on both hosts revealed autosomal, X chromosome, cytoplasmic, and autosome X cactus influences on development time. Viability differences were influenced by host plants, autosomal dominance, and X chromosomal effects. Many of the F₁, F₂, and backcross generations showed evidence of heterosis for viability. Third, a QTL analysis of male courtship song and epicuticular hydrocarbon variation based on 1688 Baja × mainland F₂ males also revealed eight QTL influencing development time differences. Mainland alleles at six of these loci were associated with longer development times, consistent with population‐level differences. Eight G × E interactions were also detected caused by longer development times of mainland alleles expressed on a mainland host with smaller differences among Baja genotypes reared on the Baja host plant. Four QTL influenced both development time and epicuticular hydrocarbon differences associated with courtship success, and there was a significant QTL‐based correlation between development time and cuticular hydrocarbon variation. Thus, the regional shifts in life histories that evolved once D. mojavensis invaded mainland Mexico from Baja California by shifting host plants were genetically correlated with variation in cuticular hydrocarbon‐based mate preferences.     

Molecular Identity of Holomastigotes (Spirotrichonymphea,Parabasalia) with Descriptions of Holomastigotes flavipes n. sp. and Holomastigotes tibialis n. sp.

Holomastigotes is a protist genus (Parabasalia: Spirotrichonymphea) that resides in the hindguts of “lower” termites. It can be distinguished from other parabasalids by spiral flagellar bands that run along the entire length of the cell, an anterior nucleus, a reduced or absent axostyle, the presence of spherical vesicles inside the cells, and the absence of ingested wood particles. Eight species have been described based on their morphology so far, although no molecular data were available prior to this study. We determined the 18S rRNA gene sequences of Holomastigotes from the hindguts of Hodotermopsis sjostedti, Reticulitermes flavipes, Reticulitermes lucifugus, and Reticulitermes tibialis. Phylogenetic analyses placed all sequences in an exclusive and well‐supported clade with the type species, Holomastigotes elongatum from R. lucifugus. However, the phylogenetic position of Holomastigotes within the Spirotrichonymphea was not resolved. We describe two new species, Holomastigotes flavipes n. sp. and Holomastigotes tibialis n. sp., inhabiting the hindguts of R. flavipes and R. tibialis, respectively.     

Endogenous synchronization of the chemical signature of Reticulitermes (Isoptera: Rhinotermitidae) worker termites

Termites of the genus Reticulitermes are characteristic of temperate regions. Their colonies comprise various castes, the most numerous being that of workers which can develop into soldiers or secondary reproductives (neotenics). Each caste has a mixture of hydrocarbons (HCs) on the cuticle forming a chemical signature. The primary aim of this study was to compare the changes in the chemical signature of a population of worker termites fed on paper with juvenile hormone to differentiate them into soldiers with a control population of termites fed only on paper or wood for one month. Gas chromatography was used to analyze the cuticular profiles of Reticulitermes flavipes termites to determine whether they changed, and, if so, when and how. The data collected over one month showed that the workers fed with JH did not differentiate into soldiers but that there were progressive changes in the hydrocarbon profile independent of the treatment. These results indicate that the differentiation of the chemical signature of the worker caste is a dynamic process, depending only on time and not on colony membership, confirming that, for these termites, this signature has a lesser role in colony membership than caste membership, unlike the chemical signatures of other social insects. The temporal process of this cuticular change is also associated with a change in the alkene/methyl-branched alkane ratio.     

Pattern of recovery of species-specific cuticular hydrocarbon mixtures by Reticulitermes santonensis and Reticulitermes lucifugus grassei after being removed from a mixed group. Is the acquisition of allospecific hydrocarbons reversible?

Each of the termite species Reticulitermes santonensis and Reticulitermes lucifugus grassei has its own particular cuticular chemical profile. When members of the two species are placed together to form artificially mixed species groups, their chemical profiles undergo changes: Each species acquires all the hydrocarbons which initially characterized the other species. When the members of a mixed group which had been kept together for 24 h were split into two homospecific groups, the cuticular profiles of the members of both groups immediately showed a sharp drop in both the homospecific and allospecific components. In R. santonensis, the homospecific hydrocarbons subsequently increased in quantity, reaching values which were higher on the 33rd day after the separation than those initially recorded in this species; whereas in R. lucifugus grassei, the homospecific hydrocarbon proportions were still lower on the 33rd day than the initial values. In both species, the allospecific hydrocarbon levels began to increase sharply on the 5th day after separation, and the homospecific products still showed no tendency to return to the initial proportions 33 days after separation. In the light of these results, some hypotheses are put forward as to what mechanisms might posibly regulate the hydrocarbon profiles of these two species. Arch. Insect Biochem. Physiol. 35:237-259, 1997.© 1997 Wiley-Liss, Inc.     

Stage-dependent feeding behavior by western tarnished plant bugs influences flower bud abscission in cotton

Unexplained variability in the relationship between the number of herbivores in a field and the amount of crop damage can arise if there is a large amount of variation among herbivore individuals in the amount of feeding damage each generates. In California, populations of the western tarnished plant bug, Lygus hesperus Knight (Heteroptera: Miridae), produce highly variable levels of damage to cotton plants (Gossypium hirsutum L.) (Malvaceae), even when found at low densities. Because L. hesperus populations are also highly variable in their overall stage structure, we hypothesize that differences in crop damage might result from varying impact by each L. hesperus stage on cotton flower buds (termed squares). Laboratory measurements of L. hesperus mouth‐parts and distance to anther sacs, a preferred feeding site, revealed that 1st?3rd instar L. hesperus nymphs will not be able to feed on anther sacs of larger squares (over 8 mm in length) but will be able to feed on squares that are most sensitive to L. hesperus damage (<7 mm). Because even the 1st instars can feed on the most sensitive ‘pinhead’ squares, size constraints do not rule out damaging effects from the youngest L. hesperus. Laboratory observations revealed that later developmental stages, and adults, spend more time feeding on cotton squares relative to 2nd and 3rd instars. In addition, a field experiment revealed no effect of 2nd instars on square retention (relative to control cages) but did reveal a significant decrease in square retention generated by adult L. hesperus (4th instar L. hesperus resulted in an intermediate level of square retention). In a final study we sampled L. hesperus stage structure and density across 38 cotton fields. Multiple regression revealed that the densities of 1st?3rd instars of L. hesperus are not correlated with anther sac damage or square retention. However, in 2 years 4th and 5th instars were positively correlated with anther sac damage and negatively correlated with square retention. In the a third year, adult L. hesperus showed correlations in the same direction, across fields and across sites within fields. Overall, these results suggest that the adults and the largest nymphs of L. hesperus (4th and 5th instars) are particularly damaging to cotton squares, with the 1st?3rd instars of L. hesperus causing little damage to plants.     

Alarm Reaction of European Reticulitermes Termites to Soldier Head Capsule Volatiles (Isoptera, Rhinotermitidae)

The alarm behavior of worker and soldier castes of four European subterranean termite species of the genus Reticulitermes (R. santonensis, R. lucifugus, R. grassei, R. banyulensis) is described. In petri dish bioassays we presented filter papers with squashed soldier heads as an odor source to trigger a alarm reaction. Untreated filter papers were used as controls. The behavioral patterns were alike for all four species. In the control situation (no alarm), only occasional workers and few soldiers were seen walking in the petri dish. When the odor source was presented, a general state of alertness was observed, showing as higher activity and presence, zigzag running, antennation of nestmates, jittering and jerking, mandible snapping, head-banging, and attraction to the odor source. Workers were attracted within a few seconds (6.9–13.4 s); soldiers followed much later (18.5–64.6 s). Both workers and soldiers inspected the odor source only briefly (workers for 8.7–12.8 s, soldiers for 10.0–19.5 s), with the exception of R. santonensis, where soldiers stayed an average of 209.8 s. The number of individuals, of 50 workers and 3 soldiers, near the odor source averaged 6.0–9.2 workers and 1.2–2.3 soldiers. The presence of workers is crucial: without workers, a significant alarm reaction in soldiers could not be induced. The roles of soldier and worker castes of Reticulitermes species within alarm communication and the origin and nature of possible alarm signals are discussed.     

Caste differentiation responses of two sympatric <Emphasis Type="Italic">Reticulitermes</Emphasis> termite species to juvenile hormone homologs and synthetic juvenoids in two laboratory assays

Summary We report on our investigations comparing three juvenile hormone (JH) homologs and two synthetic juvenoids to induce caste differentiation in laboratory colonies of Reticulitermes flavipes and R. tibialis. Two laboratory assays were evaluated as model systems for inducing caste differentiation: (1) shorter-term dish assays on groups of 20 individuals and (2) longer-term feeding assays on groups of 500 individuals. Each assay possessed attributes that can be considered advantageous under certain conditions. Specifically, dish assays were most suitable for presoldier and soldier induction, while jar assays provided for the induction of nymphs, presoldiers, soldiers, neotenic reproductives, and intercastes. Differences in response to the JH homologs and synthetic juvenoids were noted between species, suggesting differences in JH physiology may exist between R. flavipes and R. tibialis. Substantial morpholo-gical impacts were noted in association with some treatments, including (1) juvenoid-induced mandibular mal-formation in presoldiers, (2) JH II-induced abdominal elongation in R. flavipes soldiers and workers (associated with a presence of internal reproductive anatomy that is consistent with what would be expected to occur in pseudergates), and (3) JH II-induced soldier-nymph intercastes in R. tibialis that were able to further molt into soldier-alate intercastes. Findings are discussed in relation to the potential differences in JH-related physiology between R. flavipes and R. tibialis, and the use of model systems to induce rare castes and intercastes for molecular investigations of caste differentiation.     

Cuticular Extracts of Five Common Mantids (Mantodea: Mantidae) of the Eastern United States

We undertook a preliminary investigation of the cuticular extracts of five common mantid species in the eastern United States: Tenodera sinensis (Saussure), T. angustipennis (Saussure) and Mantis religiosa (Linnaeus) introduced from the Old World and Stagmomantis carolina (Johannson) and Bruneria borealis (Scudder), which are New World species. The major components of these mixtures were normal alkanes, predominately hentriacontane, or in the case of the parthenogenic species B. borealis, tritriacontane. Tricontanal was detected in the extracts of all five species, and smaller amounts of other aldehydes and n-tricontanol were detected in some species. Complex mixtures of methyl and dimethylalkanes also were present in these extracts. The composition of the cuticular hydrocarbons of these mantids may be an adaptation for reduction of evaporative water loss in these insects that inhabit open fields.     

Subspecific relationships and genetic structure in the spotted owl

Hierarchical genetic structure was examined in the three geographically-defined subspecies of spotted owl (Strix occidentalis) to define relationships among subspecies and quantify variation within and among regional and local populations. Sequences (522 bp) from domains I and II of the mitochondrial control region were analyzed for 213 individuals from 30 local breeding areas. Results confirmed significant differences between northern spotted owls and the other traditional geographically defined subspecies but did not provide support for subspecific level differences between California and Mexican spotted owls. Divergence times among subspecies estimated with a 936 bp portion of the cytochrome b gene dated Northern and California/Mexican spotted owl divergence time to 115,000–125,000 years ago, whereas California/Mexican spotted owl divergence was estimated at 15,000 years ago. Nested clade analyses indicated an association between California spotted owl and Mexican spotted owl haplotypes, implying historical contact between the two groups. Results also identified a number of individuals geographically classified as northern spotted owls (S. o. caurina) that contained haplotypes identified as California spotted owls (S. o. caurina). Among all northern spotted owls sampled (n=131), 12.9% contained California spotted owl haplotypes. In the Klamath region, which is the contact zone between the two subspecies, 20.3% (n=59) of owls were classified as California spotted owls. The Klamath region is a zone of hybridization and speciation for many other taxa as well. Analyses of population structure indicated gene flow among regions within geographically defined subspecies although there was significant differentiation among northern and southern regions of Mexican spotted owls. Among all areas examined, genetic diversity was not significantly reduced except in California spotted owls where the southern region consists of one haplotype. Our results indicate a stable contact zone between northern and California spotted owls, maintaining distinct subspecific haplotypes within their traditional ranges. This supports recovery efforts based on the traditional subspecies designation for the northern spotted owl. Further, although little variation was found between California and Mexican spotted owls, we suggest they should be managed separately because of current isolation between groups.     

Food habits of the longnose skate, <Emphasis Type="Italic">Raja rhina</Emphasis> (Jordan and Gilbert, 1880), in central California waters

Feeding studies can provide researchers with important insights towards understanding potential fishery impacts on marine systems. Raja rhina is one of the most common elasmobranch species landed in central and northern California demersal fisheries, yet life history information is extremely limited for this species and aspects of its diet are unknown. Specimens of R. rhina were collected between September, 2002 and August, 2003 from fisheries-independent trawl surveys. Percent Index of Relative Importance values indicated that the five most important prey items in 618 stomachs of R. rhina were unidentified teleosts (31.6% IRI), unidentified shrimps (19.6% IRI), unidentified euphausiids (10.9% IRI), Crangonidae (7.4% IRI), and Neocrangon resima (6.0% IRI). There were significant dietary shifts with increasing skate total length and with increasing depths. Smaller skates ate small crustaceans and larger skates ate larger fishes and cephalopods. With increasing depths, diet included bentho-pelagic teleosts and more cephalopods and euphausiids. The findings of this study are consistent with previous researchers that report similar diet shifts in skate species with size and depth.