Introduction 1996 1997 1997 2000 2001 2001 2001 2001 2002 2003 2004 1995 1996 1998a 2000 2006 2007 Distal-less 1995 1996 1998 1998 1998 2008 2002 Ultrabithorax AbdominalA 1995 1997 Extradenticle 1996 2000 Pdm Apterous 1997 Sex combs reduced 1999 Wingless 1999 1995 1996 1997 2002 2004 hox 1996 1998b 1996 2005 2006 1993 2007 1993 2002 2007 1982 1989 1995 1999 1999 1999 2002 Porcellio scaber 1 Idotea balthica 1 1997 1998 1998 1999a b 1999 Fig. 1 A I. balthica B P. scaber right C P. scaber left letters in the upper right corners  Materials and methods Animals I. balthica 1 1999 Eriphia spinifrons Idotea emarginata P. scaber 1 Generation and characterisation of the antibody 016C6 1979 1979 E. spinifrons I. emarginata Whole mount immunohistochemistry Embryos were fixed for 4 h in 4% paraformaldehyde in 0.1 M phosphate buffer (pH 7.4) at room temperature. Whole mounts of the embryos were incubated in 1 mg/ml collagenase/dispase (Sigma) for 20 min at room temperature or pretreated with short ultrasonic pulses to increase penetration of the antibodies then washed in several changes of 0.1 M phosphate-buffered saline (PBS) for 4 h and afterwards pre-incubated in PBS containing 1% normal goat serum and 0.3% Triton X-100 (PBS-TX) for 2 h at room temperature. Specimens were then incubated overnight at 4°C in supernatants of the monoclonal antibody 016C6 diluted 1:10 in PBS-TX. The omission of the primary antibody resulted in a complete absence of specific labelling. The embryos were then incubated in a biotinylated secondary antibody for 3 h (Jackson) and subsequently for another 3 h in peroxidase-conjugated streptavidin (Dianova). After washing for 4 h in PBS, the tissues were reacted with 0.013% diaminobenzidine and a reagent containing hydrogen peroxide, cobalt chloride and nickel chloride (Amersham, RPN 20) for 7–9 min to reveal the peroxidase label. Finally, whole-mount preparations were dehydrated and mounted in Eukitt (Riedel-de Haen). Preparations were observed with a Zeiss Axioskop and labelled structures drawn using a camera-lucida apparatus. The slides were also photographed on 35-mm colour slide film, the images transferred onto Kodak Photo CD and processed in Picture Publisher. Alternatively, specimens were photographed with the Polaroid DMC10 digital camera. HOECHST stain To reveal the morphology of the early embryos, specimens were dissected out of the chorion and the yolk was removed. Specimens were then fixed in 4% paraformaldehyde in 0.1 M phosphate buffer (1 h, room temperature) and stained with the nuclear dye bisbenzimide (0.1%, 15 min at room temperature; Hoechst H 33258), washed in buffer overnight and mounted in Flouromount (Sigma). Specimens were viewed with a fluorescent microscope (Axioskop) and documented as described above. Results Characterisation of monoclonal antibody 016C6 Locusta migratoria I. emarginata E. spinifrons 2 2 Fig. 2 A Numbers at the left MW 2 4 E. spinifrons I. emarginata L. migratoria 5 7 B  1993 2 Development of the embryos Idotea 1965 P. scaber 1993 1999 2005 2006 P. scaber 1993 I. balthica 3 I. balthica P. scaber Stage 1 (I. balthica E70%, P. scaber E40%; the percentage values indicate embryonic development in a percentage staging system based on developmental time): The germ band is not completely elongated, and mitotic cells in the posterior growth zone are still visible; in the more anterior thoracomeres, distinct limb anlagen can be distinguished. Stage 2 (I. balthica E80%, P. scaber E60%): All segments are formed, the embryo is not closed dorsally, and the limb anlagen are subdivided into distinct podomeres. Stage 3 (I. balthica E85%, P. scaber E80%): Red pigments is visible throughout the entire embryo, the first ommatidia can be distinguished, and single muscle precursor cells can be labelled immunohistochemically in the limb anlagen. Stage 4 (I. balthica E90%, P. scaber E90%): The growing tergites have dorsally enclosed the yolk. Stage 5 (I. balthica E100%, P. scaber E100%): hatching Fig. 3 A C I. balthica A B C D P. scaber E F P. scaber E F letters in the upper right corners A1-2 GZ LB MD MX1-2 T1-8 P1-5 A F  Development of the thoracic limbs P. scaber 3 4 3 4 4 1 1999 Fig. 4 A P. scaber B P. scaber C E I. balthica C D E letters in the upper right corners Ba Ca CX2-7 Da Is Me P1-5 Pr T8 A B C E  I. balthica P. scaber 4 4 4 5 6 7 Fig. 5 P. scaber A I. balthica B C D I. balthica E F G I. balthica H I I. balthica J I. balthica letters in the upper right corners Ca Da Pr A I B C F  Fig. 6 I. balthica A1, 2 MD MX1, 2 OP P1-3 T1-7 T8 letters in the upper right corners  Fig. 7 A I. balthica B I. balthica A light grey dark gray 1999 2003 2002 red yellow green C letters in the upper right corners Ba Ca Da Is Me Pr  Formation of a single identified muscle in the propodus of the thoracic limbs 5 P. scaber 5 I. balthica 5 5 5 5 5 5 5 Muscle pattern in the thoracic limbs of pre-hatching embryos I. balthica 6 7 7 7 7 P. scaber 1 I. balthica 1 7 1 1972 Table 1 1982 1982 1972 1981 Muscles located in this podomere Crayfish and other Decapoda Idotea Cystisoma Thorax Not shown Not shown Not shown Coxa 2 Depressors of basis 2 Extensor of basis 2 Retractors of basis 2 Levators of basis 2 Flexors of basis 2 Protractors of basis   2 Rotators of basis   adductor of basis Basis  Flexor of ischium 2 Flexors of ischium Basis and ischium are fused in adult Decapoda and contain the reductor of merus 3 Lateral extensors of ischium 2 Extensors of ischium  2 Lateral extensors of ischium  Ischium  2 Flexors of merus Flexor of merus  2 Lateral extensors of merus 2 Extensors of merus  2 medial extensors of merus  Merus Abductor of carpus (extensor) Abductor of carpus 3 Abductors of carpus Adductor of carpus (flexor) Adductor of carpus 2 Adductors of carpus Accessory adductor of carpus   Carpus Reductor of propodus (stretcher) Flexor of propodus 2 Flexors of propodus Productor of propodus (bender) Lateral extensor of propodus 2 Extensors of propodus Adductor of propodus (rotator) Medial extensor of propodus  Propodus Abductor of dactylus (opener) Flexor of dactylus 3 Flexors of dactylus Adductor of dactylus (closer) Lateral extensor of dactylus 1 Extensor of dactylus  medial extensor of dactylus  Dactylus No muscles No muscles No muscles Muscles located within the thorax are not shown. Development of muscles in the body wall 4 1 1 1 1 1 1 1 1 1 2 2 6 2 6 2 2 Discussion Myogenesis in Crustacea 2002 2002 2005 Parhyale hawaiensis 2008 1980 1981 1985 1973 1992 1981 1981 1982 1989 1982 1983 1985 1991 1995 1982 1995 1982 1995 1982 1995 Sicyonia ingentis 2006 2006 S. ingentis 2006 Homarus americanus 1 2006 S. ingentis Artemia salina H. americanus Sicyonia Artemia Comparison of myogenesis in Crustacea and Insecta 1983 1983 1992 1994 1995 1985a b 1985 1997 1997 1997 1998 1998 1999a b 1999 1982 1995 1985 1990 1997 1964 1969 1988 1969 1996 2006 2006 Muscle arrangement in the adult limbs of Isopoda and Decapoda 1961 1982 1982 1986 1989 1990 2002 2001 2002 1961 1982 1982 2001 2002 1974 1997 1937 1954 1972 Cystisoma 1981 1 1981 1937 1981 1982 7 1937 1981 1 1937 1981 Electronic Supplementary Material Below is the link to the electronic supplementary material.
 Supplementary Fig. 1 P. scaber A B C A B A C D D E F arrows E T 1-7 A B C D D E F E High resolution image file (TIF 15.0 MB) Supplementary Fig. 2 I. balthica A C A C asterisks B IE TM A asterisks CX DL IE T7 T8 VL A C High resolution image file (TIF 14.8 MB)