Invertebrate Biology最新文献

Mucus is applied to substrates as snails move and when they rest. Beyond the use of mucus in movement and adhesion, the wide array of chemicals in mucus allows for supplemental use in communication. This communication is apparent in trail-following behavior. This study addresses the potential communication via mucus in selecting resting sites in a laboratory assay. In a series of six experiments, individuals of Cornu aspersum (which often rest on above-ground surfaces) were placed into lidded plastic containers with three or four sections swabbed with water (the control) or mucus, which included the test snail's own mucus, mucus from conspecifics from the same or a different container holding snails from the same lab colony, or from a different colony, and mucus from three additional snail species. The resting location was recorded on the following day. In two additional experiments, the facultative predator Rumina decollata was tested against conspecific and other snails' mucus. Individuals of C. aspersum preferentially rested in areas with the mucus of familiar conspecifics over mucus of unfamiliar conspecifics, a behavior that may contribute to homing and aggregation behaviors. There was evidence that juveniles may be less selective than adults. The mucus of only one of the three other species was avoided by individuals of C. aspersum. Unlike individuals of C. aspersum, individuals of the predator R. decollata avoided the mucus of conspecifics, which may be associated with less need for mate-finding in this self-fertilizing species. Individuals of R. decollata did not select among potential prey species.

Sexual reproduction data are important to understand how organisms can replenish their populations and proliferate on coral reefs. Despite the importance of such data, the reproductive characteristics of most soft coral species are still unknown. Here, we examined the reproductive strategies of a species from the often-dominant genus Sclerophytum in a coral reef on subtropical Okinawa Island, Japan. DNA barcoding and histological examinations of the tissues were conducted to confirm colony conspecificity and identify reproductive characteristics, respectively, between March 2020 and March 2021. Results indicated that the studied species, identified as Sclerophytum cf. heterospiculatum, exhibits gonochorism with longer oogenesis and shorter spermatogenesis. Female colonies produced immature oocytes throughout the year, with mature oocytes observed from late July to early September, and thus, extended spawning is likely characteristic of this species. In male colonies, spermatogenesis took place over ~5 months, with spermaries present from April through August. Mature spermaries were noted beginning in July and the inferred peak of sperm release was between late August and early September, which suggests that spermatogenesis duration was ~5 months. The largest mean oocyte and spermary sizes (628.45 ± 61.36 and 240.04 ± 49.49 μm, respectively) were both recorded in August. Gamete spawning presumably occurred during the summer season, which suggests seasonality in reproduction as influenced by changes in seawater temperature. However, the proximate cue for exact dates of spawning could be the lunar period because the inferred release of spawning materials seemed to occur between full moon and last-quarter moon phases in both the months of August and September. The results of this study represent the first detailed report of reproductive characteristics of the genus Sclerophytum in Japan.

Hairworms (Nematomorpha) have indirect life cycles that require a terrestrial arthropod definitive host and an aquatic arthropod host that serves as a paratenic host, transferring the hairworm from the aquatic to the terrestrial environment. The life cycles for most hairworms remain unknown, especially the paratenic host. The hairworm Chordodes morgani lays its eggs on sticks, which are susceptible to the activity of aquatic insects such as larvae of the flatheaded mayfly (Heptageniidae), which feed by scraping algae and detritus. To test the likelihood that scrapers serve as the paratenic host for C. morgani, we collected sticks and their accompanying invertebrates from three sites near Lincoln, NE. We noted the presence of eggs of C. morgani on each stick, placed them in labeled resealable bags, and examined the invertebrates microscopically for the presence of hairworm cysts. We predicted that scrapers found on sticks with eggs of C. morgani will harbor the highest number of cysts. To confirm that larvae of the flatheaded mayfly serve as the aquatic host, we fed field-collected specimens to three captive-reared wood roaches (Parcoblatta pensylvanica). Of the three exposed roaches, one yielded nine individuals of C. morgani 63 days after exposure. Understanding the life cycle of this horsehair worm will allow researchers to rear the species in the lab, which could become a model for parasite research.

The pharaoh cuttlefish, Sepia pharaonis, has become a commercially cultured cephalopod in coastal southeast China. However, information on the reproductive histology of this species remains limited. To describe its reproductive development, this study investigated the ovarian structure and oogenesis of S. pharaonis from hatchlings to the postbreeding stage using anatomical methods and histological techniques. The results showed that oogenesis in the ovary was asynchronous and morphologically variable, with immature oocytes attached to the gonadal cord and encircling the ovarian stroma in sequence. After maturation, the egg was free in the ovarian cavity and was discharged through the fallopian tube to combine with the sperm. Furthermore, serial histological dissections of the ovaries demonstrated that oocyte development was asynchronous. Based on egg size and morphology, follicular cell morphology, and yolk formation, oogenesis in S. pharaonis was divided into five distinct stages: The oogonia stage, protoplasm growth stage, follicular penetration stage, vitellogenesis stage, and resorbing stage. Moreover, based on the appearance of follicular cells in the protoplasm growth stage and their disintegration and disappearance in the vitellogenesis stage, it can be inferred that follicular cells secrete yolk substances and participate in the formation of egg membranes. Through the dynamic observation and description of the ovary development and oogenesis, these results provide an important foundation for studies of the regulatory mechanisms of oogenesis in this species, enriching the theory of cephalopod reproductive biology and improving artificial reproduction technology.

Defecation in the lobate ctenophore Mnemiopsis leidyi was recently shown to occur periodically with an ultradian rhythm through a single transient anal pore which suddenly appeared, expelled waste, and disappeared afterward. To discover whether this novel method of defecation occurs in other kinds of ctenophores, I examined individuals of Pleurobrachia pileus and Beroe cucumis. Both ctenophores were found to have two identical and permanent anal pores as described in the scientific literature and textbooks. In P. pileus, both anal pores commonly participated in a defecation, but they did so asynchronously with independent and irregular opening and closing kinetics. Individuals of P. pileus defecated with an ultradian rhythm. Closed anal pores in P. pileus and B. cucumis consisted of a continuous ectodermal epithelium overlying a continuous endodermal epithelium with a cup-shaped group of thickened endodermal cells bearing a tuft of cilia which beats into the anal cavity. The rims of opening or closing pores were smooth and uniform without encircling muscles or fibers. This morphology and the continuity of the epithelial layers between defecations suggest that anal pores may not operate by a contractile sphincter, but by a reversible ring of tissue fusion between apposed ectodermal and endodermal epithelia to create an adjustable hole to expel waste.

Cryptic species of coquina clams Donax fossor and D. variabilis carry the hydroid epibiont Lovenella gracilis and are infected with metacercariae of the monorchiid parasites Lasiotocus trachinoti and L. choanura. The associations among this host–epibiont–parasite system were investigated. Fifty clams were collected at low tide over 3 days in June 2020 in South Carolina from each of three groups: clams with no hydroid from the upper intertidal zone and clams with and without hydroids from the swash zone. Clams were measured, identified using a newly developed PCR-RFLP, and examined for infection by metacercariae. Parasites were identified based on cercarial morphology and on metacercariae habitat in the clams. D. fossor was most often found in the swash zone and D. variabilis in the upper intertidal zone. The hydroid was most often associated with D. fossor, which was more infected by both digeneans than D. variabilis. Mean abundance of metacercariae of L. choanura was higher than that of L. trachinoti in both clams and increased over time for both parasites, because higher infection was correlated with larger clams. Greater time spent in the water by individuals of D. fossor appears to best explain these results, with the presence of the hydroids also being associated with higher infection by metacercariae in this coquina. Integration of D. variabilis in both digenean life cycles appears to lead to a positive outcome for the parasites as prevalence and abundance of infection were high; however, because D. variabilis is most frequent in the upper intertidal, more emersed, zone, it is likely deleterious to the epibiont to establish on this clam.

The search for alternative live feed for aquaculture stocks has inspired research into marine amphipods. In this study, the life history of Ceradocus mizani was evaluated to better understand how this amphipod might be used in aquaculture as an alternative feed. The amphipods did not display copulatory behavior during the study period. The females were multivoltine and attained sexual maturity on average in 23.6 days at a mean length of 4.64 mm. The incubation period lasted 8.8 days, and the mean number of juveniles produced per brood during that incubation period was relatively low (7.58). Females produced a mean of 5.2 consecutive broods and 39.4 total juveniles over the life span. (i.e., 0.33 juveniles/day). Sex ratio was female skewed (1.55:1). Female size and the number of juveniles produced per brood were positively correlated (R² = 0.63). The mean life span for females and males was 119.4 and 91.2 days, respectively. Mean maximum length was 9.26 mm for males and 8.18 mm for females. This is the first account of the life history of C. mizani and forms the basis for future studies of this marine amphipod.

Previous research focusing on pelagic gastropods in the open ocean has demonstrated that many morphospecies comprise multiple distinct clades or cryptic species that can be distinguished with DNA sequence data. To date, the genetic diversity of the pelagic gastropod fauna of the tropical East Pacific, especially in shallow coastal waters, remains largely unexplored. To document the diversity of pterotracheoids (formerly heteropods) from the coastal waters of the Bay of Panama, we collected, photographed and sequenced fragments of mitochondrial cytochrome c oxidase subunit I (COI) and 16S ribosomal DNA for 60 atlantids, 3 carinariids and 6 pterotracheids. In addition to the COI barcode, our results include the first published 16S sequences for these groups. We found 11 operational taxonomic units (OTUs): 9 in the genus Atlanta, 1 Carinaria and 1 Firoloida. We report the presence of Atlanta oligogyra (Clades A and B), Atlanta turriculata, Atlanta lesueurii, Atlanta helicinoidea (Clade B), Atlanta plana, Atlanta echinogyra, Atlanta inflata and Atlanta frontieri through comparisons of our sequences with previously published sequences. We did not find Atlanta gaudichaudi, Atlanta inclinata, Atlanta tokiokai, Atlanta gibbosa, Atlanta peronii, or Oxygyrus inflatus, which have previously been reported from the region. Haplotype networks and estimates of Φ_ST illustrate how some species show population differentiation across the tropical Indo-Pacific region, whereas others show little apparent population structure. For example, the most common haplotypes of A. inflata and of A. turriculata occur in the Indian Ocean, the Central and West Pacific and the tropical East Pacific, whereas individuals of A. frontieri from the Indian Ocean do not share haplotypes with individuals of A. frontieri from the Pacific Ocean. Analyses were limited by sample sizes, but these data suggest that population genetics approaches may be useful for reconstructing population histories of these important, but overlooked, components of the plankton.

The retrocerebral organ (RCO) is a complex glandular system that is widely distributed across species of phylum Rotifera (sensu stricto). This system is hypothesized to secrete mucus that aids in benthic locomotion, adhesion, and/or reproduction. Unfortunately, the ultrastructure of the RCO is mostly unknown, having only been partially examined in one species. We used transmission electron microscopy and confocal laser scanning microscopy to describe the RCO in the planktonic freshwater rotifer Trichocerca similis. Results reveal the RCO to be a singular syncytial organ composed of a posterior glandular region, an expansive reservoir, and an anterior duct. The glandular portion has an active synthetic cytoplasm with paired nuclei, abundant rER, ribosomes, Golgi, and mitochondria. Electron-dense secretion granules accumulate at the anterior end of the gland and undergo homotypic fusion to create larger, more electron-lucent granules with numerous mesh-like contents that gradually fuse into tubular secretions that accumulate in the reservoir. Ultrastructure of these secretions suggests they may be hydrated glycoproteins. Cross-striated longitudinal muscles form a partial sleeve around the reservoir and may function to squeeze the secretions through the single cytoplasmic duct that penetrates the cerebral ganglion. A review of the RCOs from other rotifers suggests that further ultrastructural analyses are required before attempting to discern their functions and homologies.

The growing enthusiasm for STEAM (STEM + Arts) initiatives reflects the rich potential for inquiry and integration between arts and sciences. Biologically informed poetry is an active interdisciplinary area of creation and analysis that requires biologically attuned illustration and translation to retain its STEAM effectiveness across linguistic barriers. Pablo Neruda, Chilean poet and Nobel laureate, was a keen observer and informed scholar who wove his scientific knowledge into his poetry. He was particularly obsessed with the sea and featured marine invertebrates in many of his works. The molluscs in his poem “Mollusca Gongorina” are unusual in being specified by their Latin genera. In this zoopoetic analysis, we first ask whether the 11 specimens can be identified to species and find that eight have ready identifications based on morphology in the poem's text, and three have likely identifications based on the poem's themes. We then examine illustrations and translations of the poem, identify where they are consonant or dissonant with the biology of the original, and propose alternative translations informed by the species' identities. Our zoopoetic approach to what could today be considered a STEAMy poem surfaces the beauty of its imagery and narrative, reflects the biological sophistication of the poet, enhances the coherence of its translations making it accessible to a wider audience, and allows it to enhance the biological literacy of the reader.