INDIVIDUAL IDENTIFICATION: ARTHROPODS
CRUSTACEANS
Gallardo-Escárate C., Goldstein-Vasquez J., Thiel M. (2007): Individual identification of decapod crustaceans I: Color patterns in rock shrimp (Rhynchocinetes typus). Journal of Crustacean Biology 27: 393-398.
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We examined whether color patterns of a marine crustacean may serve to distinguish between individuals and to successfully identify individuals after one molt. Digital images of the rock shrimp Rhynchocinetes typus were digitally processed in order to obtain their diffraction pattern by means of Fast Fourier Transformation (FFT). All diffraction patterns were correlated with a phase-only filter using images of rock shrimp before and after one molt. To determine the degree of similarity of color patterns among rock shrimps, correlation of diffraction pattern was performed. This approach showed that among shrimps the color pattern of the cephalothorax is mainly homogenous (∼83%) in both distribution and intensity. However, the observed degree of variability (∼17%) was sufficient to distinguish between individuals. Furthermore the general color pattern of each individual persisted after one molt and all 14 individuals could be recognized based on their color pattern. It is concluded that this non-intrusive method for distinguishing among shrimp individuals may be a useful tool that could be developed and used in the future instead of expensive and intrusive tagging techniques.
Gosselin T., Sainte-Marie B., Sévigny J. M. (2007): Individual identification of decapod crustaceans II: Natural and genetic markers in snow crab (Chionoecetes opilio). Journal of Crustacean Biology 27: 399-403.
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Methods for the identification of individual crustaceans are needed in many types of studies. Snow crab (Chionoecetes opilio) individuals have distinctive natural patterns of tubercles and spines on the carapace. The results of a double-marking experiment using these natural markers along with genetic (microsatellite) markers confirm that natural markings are a reliable means of recognizing individuals within groups of tens to hundreds of snow crabs. These natural markings are persistent through at least two molts. They have already demonstrated their usefulness in laboratory studies of molting and mating and could be applied to a wider spectrum of investigations. A cursory examination suggests that similar carapace features could be used to identify individuals in other crustacean species as well.
Oka S. I., Matsuzaki S., Toda M. (2013): Identification of individual coconut crabs, Birgus latro, on the basis of the pattern of grooves on the carapace. Crustacean Research 42: 17-23.
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We identified individual coconut crabs, Birgus latro, on the basis of photographic matching of the grooving patterns on the carapace. The photographic matching was performed using 336 front cephalothorax photographs obtained during night searching (capture and release) from 2006 to 2012 in Ocean Expo Park, southern Japan. Grooving patterns were visually matched on the basis of the distribution, form, and number of grooves. We determined that 99 individuals were captured and photographed twice. The period between release and recapture ranged from 2 to 2224 days. The grooving pattern on the carapace was unchanged, even when there were more than 1500 days between release and capture. In addition, captive crab maintained the same grooving pattern through four molts. Therefore, photographic matching of carapace grooving patterns is a useful technique for long-term individual identification. Crabs identified using this method are safer to consume than those tagged using invasive tagging methods, including passive integrated transponder tags. Photographic matching is also a useful way to identify individuals in the harvested population.
INSECTS
Caci G., Biscaccianti A. B., Cistrone L., Bosso L., Garonna A. P., Russo D. (2013): Spotting the right spot: computer-aided individual identification of the threatened cerambycid beetle Rosalia alpina. Journal of Insect Conservation 17: 787-795.
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Individual identification of animals is of paramount importance to analyze population size, dispersal, habitat preferences or behaviour. Especially for sensitive, threatened species, it is advisable to develop non-invasive recognition methods avoiding direct handling and tagging of the study subjects to be applied to procedures such as marking-recapture. Here we present an application of the I3S software for the individual recognition of the Rosalia longicorn Rosalia alpina based on the contour digitization of the spots present on the beetle’s elytra. Classification performances to individual level tested on an overall sample of 290 images (one per subject) were 94.8 (both elytra), 94.5 (right elytron) and 95.2 % (left elytron). Since I3S leaves the final decision to the operator, such high classification performances may be refined further in the final step leading to a fully reliable identification. We found that the identification performance was statistically supported and that the influence of two main error sources (contour tracing and angle under which the images were taken) was negligible. Our approach minimizes the subjectivity of a qualitative manual comparison of images and greatly reduces the time taken to visually retrieve the image of an individual especially for large photo libraries. It may be successfully used in surveys covering large areas and involving many untrained operators such as volunteers or park rangers. We propose that I3S can be applied to other insect species presenting characteristic spot patterns. To our best knowledge, this is the first study using computer-aided identification of a terrestrial arthropod.
Romiti F., Bissattini A. M., Buono V., Cifarelli C., Della Rocca F., Eniang E. A., Akani G. C., Luiselli L., Superti V., Carpaneto G. M., Vignoli L. (2017): Photographic identification method (PIM) using natural body marks: A simple tool to make a long story short. Zoologischer Anzeiger 266: 136-147.
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Individual marking allows researchers to collect important data using mark-recapture method. Photographic Identification Method (PIM) has obtained favorable opinions, being effective and less intrusive with respect to traditional marking procedures. Here, we developed and tested the efficacy of a software-aided PIM based on different characteristics, which act as natural marks. Target species were the northern spectacled salamander (Salamandrina perspicillata, Amphibia: Urodela) and the stag beetle (Lucanus cervus, Coleoptera: Lucanidae). We considered as natural mark the ventral pattern of S. perspicillata and, for the first time in L. cervus, the presence/number of small denticles on male mandibles. We selected 4 independent characteristics, each one with several states, for each species. We asked participants, with different degree of familiarity with the species, to identify recaptured individuals through manual PIM. To assess the advantages of the software, we compared the time spent by experts of the species to identify an individual through manual PIM and software-aided PIM. We further compared our semi-automated method with a fully automated one. The software efficiency was calculated by increasing the number of characteristics used to filter individuals from the database (from 1 to 4). The chosen characteristics proved their reliability for individual identification and can be used as natural marks. The proposed software-aided PIM shorten the identification time, does not led to mismatching errors and proved its efficacy regardless of the taxa/characteristic used. Thus, this tool can be consider a more practical alternative to conventional marking techniques, in particular for sensitive and threatened species that need quick and effective monitoring programs carried out with non-invasive sampling methods.
Rossi de Gasperis S., Carpaneto G. M., Nigro G., Antonini G., Chiari S., Cini A., Mancini E., Mason F., Mosconi F., Redolfi De Zan L, Roversi P. F. (2017): Computer‐aided photographic identification of Rosalia alpina (Coleoptera: Cerambycidae) applied to a mark‐recapture study. Insect Conservation and Diversity 10: 54-63.
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Assessing the conservation status of protected species needs quantitative population data, generally obtained using Capture‐Mark‐Recapture methods (CMR). The exploitation of natural marking (e.g. individual morphological traits) offers an interesting alternative, based on image analyses, which may result in a less manipulation of protected species compared to the typical artificial marking method. In our 2‐year CMR study, we tested for the first time in the natural setting the feasibility and the application of the computer‐aided photographic identification method of Rosalia alpina using the individual elytral spots as the natural marking. The I3SC software was used for the photographic analysis. Data were collected from populations of two National Parks of central Italy during July–August in 2014 and 2015. We developed a standard procedure in order to optimise the image acquisition in the field and to acquire clear and comparable images, facilitating the I3SC screening process. The results demonstrated that the computer‐aided photographic identification of natural markings can be implemented in a CMR population study of R. alpina. Our image processing approach showed that using only the elytral central spot contours made the tracing contour process less time‐consuming obtaining reliable results. Furthermore, I3SC output scores were used to identify a threshold value for the identification of new individuals or recaptures, facilitating the final identification proposed by operators. Finally, we assessed the possibility of performing the methodology using a Citizen Science approach.
Díaz-Calafat J., Ribas-Marqués E., Jaume-Ramis S., Martínez-Nuñez S., Sharapova A., Pinya S. (2018): Individual unique colour patterns of the pronotum of Rhynchophorus ferrugineus (Coleoptera: Curculionidae) allow for photographic identification methods (PIM). Journal of Asia-Pacific Entomology 21: 519-526.
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Photographic identification methods are of highly importance when it comes to reduce the animal’s stress, pain and possible injuries during or after marking techniques and thus to increase the reliability of demographic parameter estimates. There is plenty of software available for photo-identification, allowing individual identification in capture-mark-recapture (CMR) methods using body patterns, spots and marks unique to each individual. However, these non-invasive methods have hardly ever been used with arthropods. In this study, APHIS (Automated PHoto Identification Suite) has been assessed as a software capable of identifying individuals in different samplings during catch-and-release sessions with dead specimens under laboratory conditions. For this individual identification, SPM (Spot Pattern Matching) and ITM (Image Template Matching) procedures were tested; achieving a success of 100% and 95.35%, respectively. In SPM, the software itself matched the specimens almost automatically in half of the cases. However, it resulted more time-consuming than ITM during the pre-processing of images. On the other hand, ITM saves time during this step and still is able to detect recaptures accurately, yet more time may be needed when selecting the recaptures from the candidate list. Thus, it can be attested that APHIS is a competent and efficient software regarding photo-identification of Rhynchophorus ferrugineus and species with similar and unique individual colour patterns in their pronotum.
Quinby B. M., Creighton J. C., Flaherty E. A. (2021): Estimating population abundance of burying beetles using photo-identification and mark-recapture methods. Environmental Entomology 50: 238-246.
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Successful conservation and management of protected wildlife populations require reliable population abundance data. Traditional capture-mark-recapture methods can be costly, time-consuming, and invasive. Photographic mark-recapture (PMR) is a cost-effective, minimally invasive way to study population dynamics in species with distinct markings or color patterns. We tested the feasibility and the application of PMR using the software Hotspotter to identify Nicrophorus spp. from digital images of naturally occurring spot patterns on their elytra. We conducted a laboratory study evaluating the identification success of Hotspotter on Nicrophorus americanus (Olivier, 1790) and Nicrophorus orbicollis (Say, 1825) before implementation of a mark-recapture study in situ. We compared the performance of Hotspotter using both ‘high-quality’ and ‘low-quality’ photographs. For high-quality photographs, Hotspotter had a false rejection rate of 2.7–3.0% for laboratory-reared individuals and 3.9% for wild-caught individuals. For low-quality photographs, the false rejection rate was much higher, 48.8–53.3% for laboratory-reared individuals and 28.3% for wild-caught individuals. We subsequently analyzed encounter histories of wild-caught individuals with closed population models in Program MARK to estimate population abundance. In our study, we demonstrated the utility of using PMR in estimating population abundance for Nicrophorus spp. based on elytral spot patterns.
Belouard N., Behm J. E. (2023): Spotted! Computer-aided individual photo-identification allows for mark-recapture of invasive spotted lanternfly (Lycorma delicatula). Frontiers in Insect Science 3: 1112551.
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The spotted lanternfly is an invasive pest for which we lack individual movement data due in part to the difficulty posed by individual identification. We developed a computer‐aided method to identify individual adult spotted lanternfly using wing spot patterns from photos processed in the software I3S and demonstrated the method’s accuracy with lab and field validations. Based on 176 individuals in the lab, we showed that digitizing the spots of one wing allowed a 100% reliable individual identification. The errors due to user input and the variation in the angle of the image were largely negligible compared to inter-individual variations. We applied this method in the context of a mark-recapture experiment to assess the feasibility of this method in the field. We initially identified a total of 84 unique spotted lanternflies, 31 of which were recaptured after four hours along with 49 new individuals. We established that the analysis of recaptures can possibly be automated based on scores and may not require systematic visual pairwise comparison. The demonstration of the effectiveness of this method on relatively small sample sizes makes it a promising tool for field experimentation as well as lab manipulations. Once validated on larger datasets and in different contexts, it will provide ample opportunity to collect useful data on spotted lanternfly ecology that can greatly inform management.