Morphology of the megalopa of the mud crab, Rhithropanopeus harrisii (Gould, 1841) (Decapoda, Brachyura, Panopeidae), identified by DNA barcode

Abstract

The morphology of the megalopa stage of the panopeid Rhithropanopeus harrisii is redescribed and illustrated in detail from plankton specimens identified by DNA barcode (16S mtDNA) as previous descriptions do not meet the current standard of brachyuran larval description. Several morphological characters vary widely from those of other panopeid species which could cast some doubt on the species' placement in the same family. Besides, some anomalous megalopae of R. harrisii were found among specimens reared at the laboratory from zoeae collected in the plankton. These anomalous morphological features are discussed in terms of problems associated with laboratory rearing conditions.

DNA barcoding allows identification of undescribed crab megalopas from the open sea

“…For easier observation of larvae structures and setation under microscope, megalopas were first placed for 5–10 min in a watch glass with 2 ml of warm lactic acid before proceeding with the dissection of the body parts 82 .…”

“…Total genomic DNA of the megalopas from MALASPINA Expedition was extracted from muscle tissue from one pereiopod and incubated for 1–24 h in 300 µl lysis buffer (5 ml of 1 M Tris–HCl (pH 8), 1 ml 0.5 M EDTA, and 5 ml of 10% SDS solution to 400 ml of distilled water) at 65º C. Protein was precipitated by addition of 100 µl of 7.5 M ammonium acetate and subsequent centrifugation, and DNA precipitation was obtained by addition of 300 µl of isopropanol and posterior centrifugation. The resulting pellet was washed with ethanol (70%), dried, and finally resuspended in Milli-Q distilled water 82 . In the megalopas from MAF Expedition, total genomic DNA was also extracted from muscle tissue from one pereiopod, but the extraction process followed a modified Chelex 10% protocol by Estoup et al 86 .…”

Morphological Description of Ocean-Collected Portunus sp. First Crab (Crustacea: Brachyura: Portunidae) from the Obhur Creek, Red Sea, Saudi Arabia

“…Plankton-based morphological descriptions of the larvae and post larvae are meagre. In the laboratory reared larvae, physical and biological features are stable but in natural habitats abiotic and biotic factors (such as temperature, salinity and food types) are varying and these variations can impact the larval morphological features (Marco-Herrero et al, 2014). Therefore, plankton-based larvae and post-larvae must be morphologically described for taxonomic studies.…”

Settlement patterns of two sesarmid megalopae in the Sai River Estuary, Ishikawa Prefecture, Japan

“…Because the greatest number of megalopae were collected on August 16 (2-46 versus 0-11 on other days), we randomly selected 10 subsamples from six artificial substrates, onto which more than 10 megalopae had collected on August 16 for genetic analysis. DNA extraction from megalopa samples was carried out using a modification of the method reported by Marco-Herrero et al (2014). Each megalopa sample was placed in a 1.5-mL microtube and homogenized using a pestle to facilitate DNA extraction.…”