Age-specific traits in the black widow spiders Latrodectus tredecimguttatus from Crimea were studied. A post-maturation molt in black widow females was recorded for the first time. The somatic traits (body size and cuticle structure) in some adult females were found to be identical to those of juvenile specimens. Some females in the studied spider population may become mature 1 or 2 instars earlier than others, continue their growth, and molt when mature.
Here we present proteomic analyses of the protein composition of the digestive fluid of two spider species representing different lineages within the spider phylogeny, the mygalomorph species Acanthoscurria geniculata and the araneomorph species Stegodyphus mimosarum (Fig. 2; see also phylogeny in [27]). If EOD has a common origin in spiders we would expect to find a similar protein composition in digestive fluids of both species, and similar to Nephilingis cruentata [15]. However, different prey capture strategies and dietary composition among spider species raises the question of whether adaptation to different dietary niches may lead to fine-tuned differences in protein composition of digestive fluids (see Acanthoscurria: [28]; Stegodyphus: [29, 30]). Our study species A. geniculata hunts without the use of silk, catching and subduing prey only by the use of their strong chelicera and the rapid injection of venom, while S. mimosarum represents a more derived species that uses composite silk threads (cribellate silk) to construct a capture web [31]. Moreover, the latter is also a social species where individuals build communal webs, engage in communal feeding and therefore shared EOD [32, 33]. By contrast, the Nephilingis species studied by Fuzita et al. [15] represents a highly derived, solitary orb weaving spider [31]. In contrast to the study of digestive fluids by Fuzita et al. [15], the novel aspect of our work is a thorough comparison of the compositions of these secretions in species with different dietary niches, distributed across the phylogenetic tree, while thereby particularly focussing on proteins being present in both, digestive fluids and venom. Previous studies only anecdotally reported that some venom proteins are also traceable in digestive fluids [15], yet the extent of the overlap is widely unknown. We systematically explore this issue in our two species, quantify their overlap, and infer functional explanations.
Biology Of Spiders Foelix Pdf 18
We sampled digestive fluids from 9 adult Stegodyphus mimosarum females from nests that have been collected from a population in Kruger National Park, South Africa and brought to the lab at Aarhus University. Nine juvenile Acanthoscurria geniculata spiders (all of the same developmental stage) that were purchased from a pet store were sampled the same way for comparison. Acanthoscurria geniculata spiders were housed in individual plastic containers, and they were fed a cricket and watered once a week. The social S. mimosarum females were kept in their colonies, which were fed a mix of house flies and small crickets once a week. For the sampling one adult female per colony was chosen and taken out for digestive fluid sampling. In both species the sampling was conducted 7 days after the last feeding.
The proteome of the digestive fluid from Stegodyphus mimosarum and Acanthoscurria geniculate were identified and quantified using relative quantification. In total, 527 proteins were identified in Stegodyphus mimosarum and 305 proteins in Acanthoscurria geniculata, out of which 71 and 37 respectively were quantified based on ion intensities (see Additional files 1 and 2). The lower number of detected proteins in A. geniculata may well have a biological basis, but it may alternatively derive from the lower quality of the Acanthoscurria genome assembly and thus suffer from more identification gaps. Apart from the proteins that we discuss in the context of either venom or digestive activities, we also found a number of cellular proteins in low concentrations that most likely derive from gut cells, since the spiders were not physically damaged during the digestive fluid sampling.
Extra-oral digestion means that spiders are able to break down the nutrients of captured prey outside their own body. Accordingly, they can both digest large amounts of tissues and separate indigestible parts, such as the exoskeleton of the prey, before they ingest it. This has the beneficial side effect that EOD also allows for an early immune defence, potentially allowing spiders to reduce the risk of infections by preventing pathogens of entering their body.
The main prey of spiders is insects, which are rich in protein and lipids [49], yet carbohydrases that break down polysaccharids are also found in the digestive fluids. For example, in our study an alpha-amylase was quantifiably found in S. mimosarum, while only traces of a similar enzyme were found in A. geniculata (Maltase-Glucoamylase). This enzyme has also been found in Nephilingis [15], and further similarities with digestive fluids of S. mimosarum could be seen in the presence of glucose dehydrogenases, Alpha-mannosidases and Enolases (Table 1). Mommsen [50] did an early biochemical characterisation of alpha-amylases in spiders and a more recent study by Eggs & Sanders [51] suggests that carbohydrases like those may help the spiders to digest pollen that is either caught in the web or attached to insect prey. That may explain the presence of these enzymes in the web building species, N. cruentata and S. mimosarum. In Acanthoscurria, however, only a few carbohydrases were detected, which may reflect the different nutritional content of its main diet, more strongly based on cursorial insects, like cockroaches, beetles and crickets [28, 29]. Yet the main fraction of carbohydrases in all three species consisted of the aforementioned chitinases.
In addition to trypsin-like proteases, we detected astacin-like metalloproteases in large numbers indicating their high importance in EOD. These endopeptidases belong to a large family of zinc-dependent metalloproteases, and several hundreds of these have been identified across the animal kingdom and the bacteria [47, 48, 54]. Apart from digestion, they are also involved in developmental processes and tissue differentiation [55, 56]. Interestingly, especially spider genomes harbour a high number of astacin-like metalloprotease with a highly dynamic evolutionary history of this gene family [10, 15, 57]. Astacin-like metalloproteases were previously shown to be involved in extra-oral digestion [15, 55, 58], a spider key characteristic, and the evolution of this gene family may thus be directly related to the evolutionary success of spiders.
In the genome of S. mimosarum, more than 40 astacin-like metalloproteases have recently been identified [10]. Here we show that at least 33 of them are present in the digestive fluid of this species (9 of those were semi-quantified, to a concentration of 7.2% of the digestive fluid). Similarly, the A. geniculata genome includes a high number of astacin-like metalloproteases, yet their concentration is much lower in the digestive fluid of this species (0.7%). More than 30 astacin-like metalloprotease transcripts were found, however, some redundancy is expected due to the fragmented nature of the A. geniculata genome [10]. All astacin-like metalloprotease sequences found in the S. mimosarum genome contain the HEXXHXXGXXHE motif, a zinc binding motif, consistent with metalloprotease activity (Fig. 3) [56]. In addition, four conserved cysteines were present that have previously been shown to form disulphide bonds. Twelve astacin-like metalloprotease transcripts were also identified in the digestive fluids of A. geniculata, however only 9 of them showed the HEXXHXXGXXHE motif and/or the conserved cysteines included. The high abundance of astacin-like metalloproteases is also confirmed by the study on digestive fluids of Nephilngis cruentata, in which Fuzita et al. [15] detected 26 members of this enzyme family. Looking into more detail, we found that the 33 astacins expressed in the digestive fluids of S. mimosarum are located on 12 scaffolds, with two scaffolds containing 7 and 8 astacin-like metalloprotease loci (Fig. 4). This suggests that the astacin-like metalloprotease gene family evolved by sequential duplications. A phylogenetic analysis of astacin-like metalloproteases from different chelicerate species conducted by Fuzita et al. [15] suggests that the high number of spider astacin-like metalloproteases are a result of both an ancient duplication specific to spiders, and more recent lineage specific duplications. Finally, three of these proteases were also found in the venom of the species [10] (Fig. 5; Additional file 3).
The impressive abundance of astacin-like metalloproteases in digestive fluids of three spider species representing three different phylogenetic groups (A. geniculata - Mygalomorphae; S. mimosarum - Araneomorphae, Eresidae; and N. cruentata - Araneomorphae, Araneoidea, cf. Fig. 2 and [15]), suggest that this protein family is essential for successful extra-oral digestion in spiders and therefore widespread. The finding of Fuzita et al. [15] that it is mainly Ast1-type astacin-like metalloproteases (Ast1a, Ast1b and Ast1c) suggests that this type may be responsible for the success of EOD. However, the specific roles or targets of astacin-like metalloproteases in EOD are still unknown. Members of this protein family lyse the egg chorion in seahorses leading to hatching [57]. In the parasitic nematode Caenorhabditis elegans, astacin-like metalloproteases break down connective tissue of its host species [58]. It is tempting to speculate that such a barrier breaking function may be very similar in digestive fluids of spiders, breaking down connective tissues of prey. 2ff7e9595c
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