Expression Levels of the Immune-Related p38 Mitogen-Activated Protein Kinase Transcript in Response to Environmental Pollutants on Macrophthalmus japonicus Crab

Environmental pollution in the aquatic environment poses a threat to the immune system of benthic organisms. The Macrophthalmus japonicus crab, which inhabits tidal flat sediments, is a marine invertebrate that provides nutrient and organic matter cycling as a means of purification. Here, we characterized the M. japonicus p38 mitogen-activated protein kinase (MAPK) gene, which plays key roles in the regulation of cellular immune and apoptosis responses. M. japonicusp38 MAPK displayed the characteristics of the conserved MAPK family with Thr-Gly-Tyr (TGY) motif and substrate-binding site Ala-Thr-Arg-Trp (ATRW). The amino acid sequence of the M. japonicus p38 MAPK showed a close phylogenetic relationship to Eriocheir sinensis MAPK14 and Scylla paramamosainp38 MAPK. The phylogenetic tree displayed two origins of p38 MAPK: crustacean and insect. The tissue distribution patterns showed the highest expression in the gills and hepatopancreas of M. japonicus crab. In addition, p38 MAPK expression in M. japonicus gills and hepatopancreas was evaluated after exposure to environmental pollutants such as perfluorooctane sulfonate (PFOS), irgarol, di(2-ethylhexyl) phthalate (DEHP), and bisphenol A (BPA). In the gills, p38 MAPK expression significantly increased after exposure to all concentrations of the chemicals on day 7. However, on day 1, there were increased p38 MAPK responses observed after PFOS and irgarol exposure, whereas decreased p38 MAPK responses were observed after DEHP and BPA exposure. The upregulation of p38 MAPK gene also significantly led to M. japonicus hepatopancreas being undertested in all environmental pollutants. The findings in this study supported that anti-stress responses against exposure to environmental pollutants were reflected in changes in expression levels in M. japonicusp38 MAPK signaling regulation as a cellular defense mechanism.

Effects of di-(2-ethylhexyl) phthalate on Transcriptional Expression of Cellular Protection-Related HSP60 and HSP67B2 Genes in the Mud Crab Macrophthalmus japonicus

Di-2-ethylhexyl phthalate (DEHP) has attracted attention as an emerging dominant phthalate contaminant in marine sediments. Macrophthalmus japonicus, an intertidal mud crab, is capable of tolerating variations in water temperature and sudden exposure to toxic substances. To evaluate the potential effects of DEHP toxicity on cellular protection, we characterized the partial open reading frames of the stress-related heat shock protein 60 (HSP60) and small heat shock protein 67B2 (HSP67B2) genes of M. japonicus and further investigated the molecular effects on their expression levels after exposure to DEHP. Putative HSP60 and small HSP67B2 proteins had conserved HSP-family protein sequences with different C-terminus motifs. Phylogenetic analysis indicated that M. japonicus HSP60 (Mj-HSP60) and M. Japonicus HSP67B2 (Mj-HSP67B2) clustered closely with Eriocheir sinensis HSP60 and Penaeus vannamei HSP67B2, respectively. The tissue distribution of Heat shock proteins (HSPs) was the highest in the gonad for Mj-HSP60 and in the hepatopancreas for Mj-HSP67B2. The expression of Mj-HSP60 Messenger Ribonucleic Acid (mRNA) increased significantly at day 1 after exposure to all doses of DEHP, and then decreased in a dose-dependent and exposure time-dependent manner in the gills and hepatopancreas. Mj-HSP67B2 transcripts were significantly upregulated in both tissues at all doses of DEHP and at all exposure times. These results suggest that cellular immune protection could be disrupted by DEHP toxicity through transcriptional changes to HSPs in crustaceans. Small and large HSPs might be differentially involved in responses against environmental stressors and in detoxification in M. japonicus crabs.

Pemanfaatan dan pusim penangkapan kepiting jangkang (Macrophthalmus japonicus de Haan 1835) di perairan pesisir timur Kota Surabaya

Aktivitas perikanan tangkap di pesisir timur Kota Surabaya menggunakan beragam alat tangkap yang sederhana. Salah satu diantaranya adalah perikanan tangkap dengan cara memungut kepiting jangkang sebagai target tangkapan. Nelayan menggunakan papan untuk meluncur di atas hamparan lumpur guna menangkap target tangkapan berupa kepiting jangkang (Macrophthalmus japonicus) yang kondisi karapasnya masih lunak. Nelayan tidak menangkap kepiting yang kondisi karapasnya keras. Penelitian bertujuan menentukan jenis spesies sumber daya kepiting jangkang target tangkapan, lokasi penangkapan kepiting jangkang serta pola musim penangkapannya. Penelitian menggunakan metode deskriptif yang bersifat survei. Penelitian dilaksanakan pada bulan Februari sampai dengan Juli 2018. Lokasi penelitian di perairan pesisir Kota Surabaya. Responden adalah nelayan penangkap kepiting jangkang dengan lokasi tangkapan di pantai timur Kota Surabaya. Untuk penentuan jenis spesies, dilakukan sepuluh kali sampling terhadap hasil tangkapan, masing-masing sebanyak 25 ekor kepiting dalam kondisi karapas lunak. Lokasi penangkapan ditentukan oleh nelayan, pembuatan peta lokasi dengan menggunakan program Arcview 3.3. Pola musim penangkapan dilakukan dengan penentuan nilai Indeks Musim Penangkapan (IMP). Hasil penelitian sebagai berikut: 1). Jenis kepiting yang menjadi target tangkapan nelayan adalah jenis Macrophthalmus japonicus; 2). Daerah penangkapan kepiting adalah pada hamparan pasut dengan dasar berlumpur di wilayah pesisir timur Kota Surabaya pada koordinat 7014’24”–7015’05” LS dan 112048’09”–112049’04” BT; 3). Pola musim penangkapan kepiting berdasarkan IMP adalah, musim puncak secara berturut berlangsung pada bulan: April (612,96%), dan Mei (164,68%). Musim sedang pada bulan: Juli (77,76%), Maret (68,61%), Februari (64,04%), dan Januari (59,47%). Musim paceklik pada bulan: Juni (42,69%), November (36,59%), Agustus (32,02%), Oktober (18,30%), Desember (18,30%), dan September (4,57%).

Environmental Pollutants Impair Transcriptional Regulation of the Vitellogenin Gene in the Burrowing Mud Crab (Macrophthalmus Japonicus)

Vitellogenesis is a pivotal reproductive process of the yolk formation in crustaceans. Vitellogenin (VTG) is the precursor of main yolk proteins and synthesized by endogenous estrogens. The intertidal mud crab (Macrophthalmus japonicus) inhabits sediment and is a good indicator for assessing polluted benthic environments. The purpose of this study was to identify potential responses of M. japonicus VTG under environmental stresses caused by chemical pollutants, such as 1, 10, and 30 µg L−1 concentrations in di(2-ethylhexyl) phthalate (DEHP), bisphenol A (BPA) and irgarol. We characterized the M. japonicus VTG gene and analyzed the transcriptional expression of VTG mRNA in M. japonicus exposed to various chemicals and exposure periods. A phylogenetic analysis revealed that the M. japonicus VTG clustered closely with Eriocheir sinensis (Chinese mitten crab) VTG, in contrast with another clade that included the VTG ortholog of other crabs. The basal level of VTG expression was the highest in the hepatopancreas and ovaries, and tissues. VTG expression significantly increased in the ovaries and hepatopancreas after 24 h exposure to DEHP. Increased responses of VTG transcripts were found in M. japonicus exposed to DEHP and BPA for 96 h; however, VTG expression decreased in both tissues after irgarol exposure. After an exposure of 7 d, VTG expression significantly increased in the ovaries and hepatopancreas for all concentrations of all chemicals. These results suggest that the crustacean embryogenesis and endocrine processes are impaired by the environmental chemical pollutants DEHP, BPA, and irgarol.