Abstract The Crustacea Collection of the Museu Nacional/UFRJ is one of the most relevant and representative of the Brazilian crustacean fauna. Currently, it comprises around 31,000 registered lots, of which 5,435 lots belong to the order Isopoda. This paper provides an illustrated catalog of two topotype species and 34 type species of marine isopods deposited at the Crustacea Collection of Museu Nacional/UFRJ, distributed in 22 genera, 12 families and six suborders. This collection is represented by 27 lots of holotypes, 81 lots of paratypes (15 named as allotypes), and two topotypes, published mainly by authors such as Alceu Lemos de Castro and Idalina Brasil-Lima, former researchers of Museu Nacional in the 20th century. The two topotypes species were included in the catalog as they came from the same collection event as the holotype and have been historically kept as type material within the museum collection. In general, the type materials are in good condition, however, the holotype of Robustura parvula (Albuquerque, 1978) and all type material of Pseudione serejoae Brito, Cardoso and Boyko, 2018 have been lost and await the designation of neotypes. Furthermore, this catalog is part of a larger project, in an effort to improve the curation and digitization of the museum´s type collection data. By photographing the specimens and digitizing the collection specimens´ labels, we expect to improve internal management and offer free access to the data, so as to preserve and promote the museum´s collections, which guard important and unique information on world biodiversity.

Abstract The present study reports the first zoogeographical record of the squat lobster Munidopsis lauensis Baba and de Saint Laurent, 1992 from a cold-seep site in the Krishna-Godavari Basin (Bay of Bengal), Northern Indian Ocean. Molecular analysis of the partial mitochondrial gene coding for cytochrome C oxidase subunit I (COI mtDNA), and mitochondrial 16S ribosomal RNA (16S rRNA) validated its identity. The present observation extends its geographical distribution to the Northern Indian Ocean. Additionally, molecular barcodes (COI) were generated for Munidopsis scobina Alcock, 1894, Munidopsis wardeni Anderson, 1896, and Shinkaia crosnieri Baba and Williams, 1998 collected from the Indian Exclusive Economic Zone.

Abstract Lobed tegumental glands are found only in terrestrial isopods and are thought to have evolved in response to challenges associated with life on land. By examining 30 terrestrial isopod species, we aimed to determine the factors that influence the structure and distribution of the lobed glands. We discovered that lobed glands are found not only in the lateral plates and the uropods but also in the cephalothorax, the antennae, the tergites, and the pereopods of some species. The structure of the lobed glands is influenced by the phylogenetic position of an isopod. Namely, species of Diplocheta, Microcheta, and Synocheta have only one nucleus in the secretory cell, while two nuclei occur in the secretory cells of Crinocheta. By contrast, the distribution of the lobed glands in the body is influenced by the eco-morphotype of a species. Clingers and runners have numerous large lobed glands throughout the body. Creepers possess well-developed uropod glands, while lobed glands are absent or small and few in number in their pereon. Rollers have fewer lobed glands and some species apparently lack them. We also showed that several species possess several types of lobed glands. The correlation of lobed gland distribution with the eco-morphotype speaks in favor of the proposed defensive function of lobed glands.

Abstract An analysis of reproductive potential can elucidate significant aspects of the population biology and evolution of brachyuran crabs, providing a crucial baseline for conservation efforts concerning endangered species. Johngarthia lagostoma is an endemic species to Atlantic Oceanic islands (Rocas Atoll, Fernando de Noronha, Ascension, and Trindade), and it is classified as endangered (EN) in Brazilian territory according to IUCN criteria. Until now, the reproductive potential of this species has only been described for the Ascension Island population. Therefore, we assessed the reproductive effort and fecundity of J. lagostoma on Trindade Island. A total of 43 ovigerous females in the final stage of embryonic development were analyzed. Their egg masses were removed, weighed, and counted using a volumetric method. The carapace width ranged from 55.3 to 100.1 mm (mean ± standard deviation: 75.2 ± 13.1 mm). It exhibited a good fit and positive correlation with the egg weight and fecundity data but a poor fit and negative correlation with reproductive effort. The contrasting results of fecundity (82,938 ± 43,673 eggs) and reproductive effort (10.5 ± 1.5 %) recorded for J. lagostoma reveal a well-established population on Trindade Island compared to Ascension Island. These observations provide valuable information for proposing more effective management strategies for this endangered species across these Atlantic oceanic islands.

ABSTRACT Apocyclops spartinus is a subtropical resilient copepod from impacted Peruvian wetlands, widely used for marine fish larviculture and conserved as a strain at Instituto del Mar del Peru - IMARPE. This study was conducted to test the effects of three thermal conditions (16, 20 and 24 ºC) on the individual growth of conditioned nauplii. Sub-stage growth rates, three growth models and three growth rate-dependent models were evaluated. Considering these previous experiments, naupliar growth retardation and mortality were evaluated for cold shock stress (8 ºC lower). Results indicated a progressive increase in development time by reducing temperature from 24 to 20 ºC (1.75 times) and 20 to 16 ºC (4 times). Growth rates showed a tendency to decrease, prior to metamorphosis and independent of temperature. Gompertz was the best growth model by describing sigmoidal tendency of naupliar development. Arrhenius was the best growth rate-dependent model but slightly better supported than a simple allometric model. Naupliar growth retardation was noted in nauplii that were initially hatched at 24 ºC and then swiftly transferred to a culture at 16 ºC. This cold shock stress resulted in high mortality from day four onwards. In summary, A. spartinus nauplii exhibit potential as a live food source and it is recommended that targeted thermal treatments be employed to extend the time of optimal nauplii size and thereby enhance culture techniques of this species.

Abstract A simple, cheap, and yet effective technique to allow easy mounting and imaging of small crustacean (or arthropod) limbs or appendages under the scanning electron microscope using custom-made aluminum mounts, cut from commercial aluminum cans, is explained and illustrated.

Abstract It is known that several animals are sensitive to magnetic fields. Magnetoreception in animals is the ability to sense the geomagnetic field of the Earth and to use their vectorial properties for navigation and terrestrial location. Animals can also show magneto-sensitivity, unrelated to navigation and show changes in behavior during the application of magnetic fields. The aim of the present study was to analyze the behavior of the shrimp Litopennaeus vannamei under the presence of artificial magnetic fields of different intensities under laboratory conditions. Shrimps were chosen because of their economic importance and because they have been neglected in the study of magneto-sensitivity in animals. The laboratory experiments were performed with the use of a pair of circular coils and four aquariums (three treatments and a control, with 20 shrimps each). Our results show for the first time that L. vannamei shrimps are magneto-sensitive, showing a preference to swim against the magnetic field lines direction as is done by magnetotactic bacteria from the Southern Hemisphere. Also, it was observed that the shrimps remain still after the application of magnetic field intensities from 44 to 237 µT, which could be useful for maintaining shrimps in their captive areas.

Abstract Procambarus montebelloensis, new species, is described from Montebello lake district in Chiapas, Mexico. The new species can be distinguished from P. mirandai by a gonopod with shorter and more slender mesial process apically directed, a less pronounced cephalic shoulder and a shorter central projection. Regarding the external morphology, in the new species the anterior portion of the head is notably directed downwards, and it has a more elongated chela with a distinct dentition.

Abstract Isopods of the suborder Cymothoida include ectoparasite species that cause physical damage and affect the development of the host by feeding on blood and tissues. On fishes, these parasites attach themselves to the skin, fins, gills, and oral cavity using claws on articulated legs. The ability to remain hidden in cavities even after the fish is caught enables isopods to be transported to new areas along with the host, making these parasites potential co-invaders. Understanding the role and environmental impact of parasites is essential, although research on parasitism in the context of biological invasions lags in comparison to general research on such invasions. Previous records indicate only two species of parasitic isopods in the São Francisco River basin. However, the present study reports the first record of two other species (Braga patagonica and Braga nasuta) on Pygocentrus piraya and in the basin itself. This demonstrates a lack of knowledge regarding fish parasites in the region, despite the presence of other parasites. Collaborations with research groups conducting fish sampling in the basin can contribute to expanding knowledge on these parasites and the training of human resources in fish parasitology. The present study provides important information on the presence of unidentified parasitic isopods on fishes in the São Francisco River basin, underscoring the need for further studies and expanding the geographic distribution of these parasites, as well as the host list for these isopods.

Abstract Intermediate metabolism and oxidative balance markers help to better understand environmental dynamics and how they influence the physiological patterns of organisms. Procambarus clarkii (Girard, 1852), a crayfish native to the United States of America and Mexico, represents an appealing case study for understanding invasive species’ metabolic dynamics. This species has sexual dimorphism and two male morphotypes: reproductive (M1) and non-reproductive (M2). We evaluated the seasonal variations of biomarkers in M1 and M2 males, collected in each season of 2016 at Parque Alfredo Volpi (São Paulo, Brazil). Hemolymph, hepatopancreas and abdominal muscle samples were extracted to determine markers of intermediate metabolism, oxidative balance, the hepatosomatic index and the stomach repletion degree. The results showed differences between the two male morphotypes. M1 showed a predominance of medium to full stomachs throughout the year, with an allocation of energetic substrates mainly used in reproduction (gametogenesis and reproductive behaviors). They also presented increased lipoperoxidation, SOD and GST activities. M2, on the other hand, had a lower capacity to allocate energy reserves in the period leading up to and during reproduction, which may be associated with a lower degree of gastric repletion. However, M2 maintained alternating antioxidant strategies that helped preserve low levels of lipoperoxidation in the hepatopancreas throughout the year. This pattern observed for the degree of gastric repletion indicates an intraspecific competition between the categories of males, which, together with the profile of energy reserve usage, seems decisive for M2 to reproduce.

Abstract The present paper describes a new species of freshwater crayfish of the genus Parastacus Huxley, 1879 from the municipality of Amaral Ferrador in the state of Rio Grande do Sul, southern Brazil, evaluates its conservation status according to the IUCN Red List Criteria (sub-criterion B1), and updates the identification key for the genus. Parastacus longidactylus sp. n. differs from all analyzed species by the large eyes, the prominent and wide rostral carinae, surpassing the rostral basis and extending to the proximal third of the postorbital carinae, postorbital carinae and rostral carinae prominent and with similar lengths, chelipeds carpus dorsomedial surface not divided longitudinally by groove and long dactylus, surpassing the fixed finger. The possible extent of occurrence was estimated to be 6,968 km² and the species was recorded in only one location in the Camaquã River basin. The main threats to the region are the replacement of native vegetation by crops and livestock, water pollution and soil erosion. However, because there is only one known location where Parastacus longidactylus sp. n. occurs we suggest classifying the species as Data Deficient.

Abstract Heterochely is an important phenomenon in decapod crustaceans. Nevertheless, it was rarely examined in freshwater crayfish. Therefore, the aim of this study was to investigate cheliped loss and abnormalities of the narrow-clawed crayfish, Pontastacus leptodactylus. The crayfish samples were captured using 17 mm mesh-sized fyke-nets from Atikhisar Reservoir in Çanakkale, Turkey between July 2020 and June 2021. The cheliped loss was classified and compared between sexes and length groups. The cheliped surface was calculated for each specimen for both the right and left cheliped. Results of the study indicate that the percentages of the sampled individuals were 5.46% for the right cheliped missing group, 5.23% for the left cheliped missing group, 10.37% for both chelipeds missing group, and 78.94% for both chelipeds present group. There was a statistical difference between cheliped loss and size groups (p < 0.05). Although cheliped loss is almost non-existent in low-size groups (10.0-29.9 mm), it reaches high values in the 40.0-69.9 mm size groups. The most intense loss occurs in the 40.0-49.9 and 50.0-59.9 mm size groups. It was determined that 10.69% of the sampled individuals examined had a single cheliped (10.03% female, 11.14% male). A statistically significant difference was found between cheliped loss and sex (p < 0.05). The percentage of female and male individuals with no chelipeds is 9.83% for females and 10.73% for males, and with both chelipeds it is 80.14% for females and 78.14% for males. While the number of abnormalities observed in chelipeds was higher in males, abnormalities in both chelipeds were higher in females. Moreover, it was found that cheliped loss significantly differed according to the months of collection (p < 0.05). Cheliped losses increased in July, August, and September when feeding was comparatively intense. In conclusion, the fact that the individuals were obtained alive, was an indication that the abnormalities detected did not significantly affect their vital activities directly. However, morphological abnormalities in the appendages, especially in the chelipeds, may impair their functional use compared to a healthy cheliped. This abnormal condition is assumed to share the disadvantageous limitations experienced by the absence of a cheliped.

Abstract Despite the recent increase in knowledge about Brazilian Cladoceromorpha (Cladocera and Cyclestherida), this group of fauna is poorly known in some regions of the country, including Alagoas State. Based on the literature and a few original samples, the present paper reports 35 species of Cladoceromorpha from Alagoas, 18 of which are new records for the state. The observed taxa are illustrated. In addition, distributional and taxonomic comments on selected taxa are provided.

ABSTRACT The calanoid copepod family Epacteriscidae is one of the most representative cave-dwelling copepods worldwide, especially in the Caribbean region. We provide new records of two epacteriscid copepods from anchialine habitats of the Yucatan Peninsula (YP); both were previously known only from their type locality in Jamaica and Caicos Islands. We document the occurrence of Edaxiella rubra Fosshagen, Boxshall and Iliffe, 2001 in Cozumel Island and Bofuriella spinosa Fosshagen and Iliffe, 2007 in Playa del Carmen, the adjacent continental region of the YP. We found slight morphological differences compared to the original descriptions of both species, including some characters not previously described; also, the male of B. spinosa remained unknown and is herein described. These records show the growth of the epacteriscid copepod listings and expand the morphological knowledge of these species in the Yucatan Peninsula into the Western Caribbean, likely harboring one of the most diverse anchialine copepod fauna worldwide and currently going through intense anthropogenic pressure, thus enhancing the intrinsic value of these new findings. It is expected that new samplings will reveal the true diversity and distribution of the Mexican Caribbean anchialine copepod fauna, where knowledge of its biological diversity is still incipient.