異目魚屬Ipnops屬于異目魚科Ipnopidae，共3種。模式種為Ipnops murrayiGünther, 1878。該屬幼體于海水表層浮游生活，亞成體即沉入深海，成體分布于水深1392~4970米。

Ipnops murrayi/ NOAA Office of Ocean Exploration and Research, Gulf of Mexico 2018, Public domain

Ipnops murrayi/ NOAA Office of Ocean Exploration and Research, Exploring Deep-Sea Habitats off Puerto Rico and the U.S. Virgin Islands, 2018, Public domain

異目魚最顯著的特征即為其頭頂?shù)脑谟补囚~中形狀獨(dú)一無二的器官。該器官曾被認(rèn)為是發(fā)光器或同時(shí)具有眼和發(fā)光功能，后經(jīng)解剖確認(rèn)為高度特化的眼。成年異目魚的眼位于頭頂，表面覆蓋一層薄的透明膜，該膜由左右額骨（frontal bone）和頂骨（parietal bone）融合而成。眼無晶狀體，虹膜退化，視網(wǎng)膜極扁平。眼本身固定，因此眼肌高度退化。這些特征意味著異目魚的眼睛為探測(cè)極微量光線而犧牲了所有成像裝置。

異目魚幼體在海水表層浮游生活，此時(shí)其眼睛較為正常，位于頭部?jī)蓚?cè)。在成長(zhǎng)過程中，異目魚棲息地逐漸變深，雙眼90°轉(zhuǎn)向并移至頭頂，額骨和頂骨逐漸融合，最終形成成年異目魚結(jié)構(gòu)極為特殊的眼。

Ipnops meadi/ Astrid Leitner, NOAA Office of Exploration, Public domain

異目魚骨骼鈣化程度較低，嗅覺器官嚴(yán)重退化，但側(cè)線系統(tǒng)特別是頭部的感覺器官發(fā)達(dá)。鰓蓋膜和鰓蓋結(jié)構(gòu)使得從鰓腔排出的水必須通過鰓蓋角斜向上涌出，這樣可避免身體側(cè)線受到不必要的刺激，也不會(huì)過度攪動(dòng)沉積物。異目魚主要棲息于深淵底部，通過頭頂?shù)母泄馄饔^測(cè)多毛類或小型甲殼類活動(dòng)時(shí)產(chǎn)生的微弱光芒——這些生物可能自身不發(fā)光，但其活動(dòng)時(shí)會(huì)驚擾附近的發(fā)光微生物導(dǎo)致發(fā)光。

Ipnops meadi/ Thiel et al, 2022

異目魚雌雄同體，通常集群出現(xiàn)。其眼部對(duì)光線的獨(dú)特反射使其在深海觀測(cè)中極為顯眼，因此成為克拉里昂-克利帕頓斷裂帶（Clarion-Clipperton Zone，CCZ）最常見的一屬魚類。

參考文獻(xiàn)及部分圖片來源：

Anderson W W, Berry F H, B?hlke J E, et al, 1966. Fishes of the Western North Atlantic: Orders Iniomi and Lyomeri: Part 5[M]. New Haven:Yale University Press: 147.

Marshall N B, Staiger J C, 1975. Biological results of the University of Miami deep-sea expeditions. 110: Aspects of the structure, relationships, and biology of the deep-sea fishIpnops murrayi(Family Bathypteroidae)[J]. Bulletin of Marine Science, 25(1): 101-111.

Munk O, 1959. The eyes ofIpnops murrayiGunther, 1887[J]. Galathea, 3: 79-87.

Okiyama M, 1981. A larval Ipnops and its possible metamorphosing process[J]. Japanese Journal of Ichthyology, 28(3): 247-253.

Okiyama M, 1986. Bathypelagic capture of a metamorphosing juvenile ofIpnops agassizi(Ipnopidae, Myctophiformes)[J]. Japanese Journal of Ichthyology, 32(4): 443-446.

Okiyama M, Ida H, 2010. Record ofIpnopssp. (Ipnopidae: Aulopiformes) from northern Japan[J]. Ichthyological Research, 57(4): 422-423.

Prirodina V P, Neyelov A V, 2020. The osteological features ofIpnops agassiziiGarman, 1899 (Aulopiformes: Ipnopidae) from Bathyal and Ultra-Abyssal Depths of the Australia–New Zealand Region, with remarks on the biogeographical significance of these findings[J]. Russian Journal of Marine Biology, 46(1): 22-28.

Theisen B, 1966. On the cranial morphology ofIpnops murrayiGunther, 1878: With special reference to the relations between the eyes and the skull[J]. Galathea, 28: 7-18.

Thiel R, Christodoulou M, Pogonoski J J, et al, 2022. An application of morphological analysis and DNA barcoding to identifyIpnopsfrom the Clarion-Clipperton Zone (CCZ) as I. meadi Nielsen, 1966 with notes on other species of the genus (Aulopiformes: Ipnopidae)[J]. Marine Biodiversity, 52(6): 68.

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