Chapter 7 Planktonic Crustacea Part VI Euphausiacea Department of Oceanography References ? Baker A de C, Boden B P, Brinton E, 1990. A practical guide to the euphausiids of the world. 96p ? Mauchline J, Fisher L R, 1969. The biology of euphausiids. Advances in Marine Biology, 7, 454p ? Mauchline J, 1980. The biology of mysids and euphausiids. Advances in Marine Biology, 18, 681p Features – a complete carapace covering the entire cephalothorax – complete similarity of all biramous thoracic limbs – podobranchia – Photophores – Indirectly development 1 General morphology 1.1 External features ? cephalothorax ? abdomen ? rostrum ? cervical groove ? Lateral denticles ? dorsal spine ? dorsal keel ? preanal spine Appendages ? A 1 ? A 2 ? M；M 1 ；M 2 ? P 1-8 ? Pl 1-5 ? Up 1.2 Internal morphology ? 1.2.1 Digestive system: mouth – esophagus – stomach – midgut – hindgut - anus ? 1.2.2 Circulation ? 1.2.3 Respiration system: podobrachiae ? 1.2.4 Excretory system: antennal glands ? 1.2.5 Reproductive system: ♀♂dioecious ? 1.2.6 Nervous system and sensory organ：compound eyes ? 1.2.7 Photophores 2 Classification Crustacea Malacostraca Eucarida Euphausiacea (2 families, 11 genera, 87 species) Family Bentheuphausiidae Family Euphausiidae Order Euphausiacea 1a Photophores present only on abdominal segment one ………Stylocheiron手磷虾属 1b Photophores present on abdominal segments one to four ………………………….2 1c No photophores on abdomen or thorax ………………….…… 3 1b 1a 1c 2a Eyes round, thoracic legs of approximately the same length …...………....3 2b Eyes in two parts with a constriction between the lobes, one or two pair of thoracic legs very elongated ………..............8 2a 2b 3a A full complement of eight thoracic legs …………………..……Bentheuphausia amblyops 3b Eight thoracic leg extremely minute. Seventh thoracic leg smaller than sixth but the same shape and with the number of segments (six) …………………………….Thysanopoda樱磷虾 3c Eight thoracic leg extremely minute and seventh thoracic leg with only two segments or reduced to a very small process ……………………….........……..4 3b 3c 3c 4a Anterior margin of frontal plate concave ……………………………...…Pseudeuphausia假磷虾属 4b Anterior margin of frontal plate produced to form a sharp or gently rounded rostrum ……………………..5 4a 4b 4b 5a A denticle at the mid-point or on the posterior half the lateral margin of the carapace. An anterior lateral denticle also may be present …………....…6 5b There is either no lateral denticle or, if one is present, it is well anterior to the mid-point of the lateral margin of the carapace ………………………7 5a 5b 6a Seventh thoracic leg consisting of two elongated joints and the seventh thoracic exopod present. Strong postocular spines and long recurved antennular lappets present ………………........Meganyctiphanes novegica 6b Seventh thoracic leg consisting of only a minute process and seventh thoracic exopod absent ………………………………………..…Euphausia磷虾属 7a A strong recurved lappet on first segment of antennular peduncle …………………...….Nyctiphanes 7b The lappet, if present, is small and not recurved ………………………………….…Thysanoessa 7a 7b 8a Second and third thoracic legs elonged ………..............….Tessarabrachion oculatum 8b Second thoracic leg elongated…………..............…...9 8c Third thoracic leg elongated ………..Nematobrachion臂磷虾属 9a Second thoracic legs very slender and naked with only a tuft of terminal bristles. Terminal segment of first thoracic leg with short, robust comb-like spines ……………………………………….Nematoscelis线脚磷虾属 9b Second thoracic legs rather strong, last two segments armed with spiniform bristles. Terminal segment of first thoracic leg hardly broader than penultimate segment and with only fine terminal setae ……………………………………..….Thysanoessa 9a 9b Bentheuphausia amblyops ?♂Pl 1-2 not modified as petasma, the base of Pl 1 with 1-6 spines ? Up with a transverse suture near the distal end ? without photophores Euphausia pacifica ? length E. pacifica 20-25 mm E. nana 7.3-8.3 mm ? distribution E. pacifica 南黄海，冬春季可达长江以北 E. nana 东海，夏季可达南黄海 E. pacifica E. nana Pseudeuphausia sinica ? Madible P. sinica without palp P. latifrons with a well-developed palp ? Maxillule P. sinica with exopod P. latifrons without exopod ? Distribution P. sinica东海和南黄海近岸低盐水 我国地方种 P. latifrons南海，东海外海 太平洋和印度洋的热带海区 P. sinica P. latifrons 3 Biology and Significance ? 3.1 Biology 3.1.1 Distribution vertical distribution 3.1.2 Feeding habits 3.1.3 Growth and development 3.1.4 Swarming and Bioluminescence sound scattering layer ? 3.2 Euphausiid fishery Development ? nauplii无节 ? calyptopis节胸 ? furcilia带叉 ? cyrtopia节鞭 Bioluminescence Krill fishery BIOMASS: 6.5~10×10 9 tons Max Catch: 7×10 6 tons