Notes on the Ecology of the Oceanic Insect Halobates
Total Page:16
File Type:pdf, Size:1020Kb
MFR PAPER 1032 Lanna ' heng i a rn~lI\hl'r III till' \Iarine Life R ~ 'e ardl Group. cripp" In,litution of (hcan .. ograph), LniHf'oil) of (alilor .. nia. an l)i eJ,!o. La JIIII.!. (' \ Tens of thousands of genera of insects 92037. are known on land: there is only one on the sea-Ha lobates . about 2 month, lor the L'g!! III d,'\elt p into mature ,ldulh. r hc ,~ . c, .1IC 11111 dl,tlngul,hahle unlil Ihe I.I\! Il\ IllI h I Notes on the Ecology of the stage. Oceanic Insect Halobates The,e In,cct, II\e e'\dll'l\ch "ll Ih.: surfacc of the ocean . ..t Ihc\ .IrC \1 I Ill! les) and cannot 11\. Ilhllugh "'\l1' earlier \\llrk~r, ha\c rcr"rtni Ih,1I Halohal{"l can dl\e. I hd\c nUl bccll LANNA CHENG able to induce them III d" ,(I HU\I" eyer. \\hen lhe) arc 1,lrccd 1I1llkr watcr lhc) can ,\llm I,'r ,I, 1'"lg.1 .111 INTRODUCTION Iy rclated to surface properties of the hour or 1\\0. Thl' ahilll\ tIl \\ '11 ocean suc h as temperature. salinit). undcr \\ atcr 1\ rre,umdhh Imr"[(,lnl Members of the genus H alobares surface c urre nts. and winds ( avilov. for the suni\al 01 lhe,e IlhCCh IIll.l (H cteroptcra:Gerridae) are the o nly 1967). in ~torm\ the) arc rr(lhabh "iten known insects found in the oceans, submerged b) \\a\e, llr pr.t\ l t yet they are a m o ng the least studi ed GENERAL BIOLOGY mately the) Illu,l re .. ,url.lcc, he")1 L marine organisms. Althou gh these Our present knowledge of the bi .. the) become \\ atcrl(lgged .lIld dr 1\\ n insects h ave been known to marine o logy of these ocea ni c insects is based For this rea,on lhc) r(""C\\ .t \ ... f\ biologists a nd ocean ographe rs since m ainl y o n casual ob ervations at sea. effecli\'e \\ ater-rercllelll C(I.1111l1! III the earl y 1800's, nothing much was si nce attempts to rear them in the hall', on their hlld\ ,url.lce Ihe ,I added to our knowledge of these la boratOl'y h ave not been successful called "pi a,lron" II h Ich al", he Ip unique insects until the last 20 year so far. them 10 retain a lIprl) III 11\ \ ~Lll III (Cheng, 1972). W e now know t h at The adults a re dark gra) or black. enahle lhcm l" re'rlre \\hcll IIh there are 39 d escribed s pecies found wi th som e pale marki ngs on thc head Illerged (Cheng. I 97..1dl. In the world's oceans, seas, a nd a nd prothorax. a lmost 5 mm in bod} The adulh arc allr,lcled III light .tnd lagoons (H erring, 196 1, 1964). le n gth , with a leg spread of about 15 ma) be dlp .. netted ca,," h\ 1I Illg .1 DISTRIBUTION mm (Figure 2). The eggs are laid on light lurc When a Ilghl tr;l!' 1I.t 11 cd a ny sui table or a \ a i lable ftoati ng on a raft .11 the Hallall In,llIlIle 01 Five H alobares species are com m o n object. the commonest substrate :\Ianne BIOiL1g). (,'cllnut hl.llld. II ly found in the o pen ocean (Figure I). bei ng piece of \\ ood, seabird feathers. Janu..tr) 197,. thc Ilr,t rCLlI11~1l ..til All fi\'c-H . III i(,(11 IS. H . S('I'iUIIS, H . a nd tar lumps. They are about I mm adull male,. carnc III Ihc h:,!ill . flcr ge/'ll/(/lIl1s. H . splellilells, and H. in le n gth and look rather like minia about IOmlnulc, The lir,t 11\ mph \\.1 IOhrilllls-are found in the P acific ture rice grains. The ne\\I) hatched caughl ..tl lhe Ilghl ,lllll''''1 ~ Illur Ocean, but only the first two occur n) mphs, \\ hich are a lso about I mm in after the trar \\.1 ,cl ur \dull 1111 also in the India n Ocean , a nd only H . bod) length. are light hro\\ n in color hUIt'1 cllntlnllcd tel C,)IllL 1,1 II ~hl lIIic(/IIS is kno\\ n from the tlantic \\ ith characteristic dark brO\\n pattern .. lhrllllghllut thL I1lght. bd I(,n I'J (I Ocean (Cheng, I 973a1. In general the) ing. There are fi\e n) mphal ,tage" and 064..- h,'ur . .11 \1 hlLh lillie It u I are found in tro pica l and subtropical before the insects become ,c'\uall) beg.ln tel gel II:,!hl \\ a te rs, the ir ranges e'\tending from mature. 'We do not kno\\ hll\\ long Dunng a recellt " r~dltl n Il Ihe lat. .. +0 0 N . to .. +0 0 in thc Atlantic each stage take,. but laborator) data nllrth Lenlral P;,tcII·l. f') )(Ilh I HI I (Chcn g. 1973b) and thc Pacific (Cheng. from reari ng clo,e1) related fre,h\\ ater ne 1973a, 1973c) but being morc re .. gerrids ( heng. 1966a) and a near .. ,tricted in the Indian Occan (Ch cng. shorc "pccie" H ./llIl1uii,l/Iil. (H erring. llgr.lrh\ L ~.HLh flu;! 19711. Ithough the e,\act factor, 1961) ,ugge't thaI 10 .. 12 da), I a found lh I fit I limiling the di~lribulion llf each rca on able perll1d for each lage II Ithln ,pecies are nlll kno\\ n. thc) are certain .. H ence it \\ould require a pen'ld III .lrn\ cd n Halobar es were observed to feed on Island , together with o ne ample consist of about 90 percent seawater. one another when numbe rs were kept of Gygis alha which contained no On a recent expedition to the orth without food in an aquarium on board recognizable Halo/wles remain . Two Paci fic o va ri ous organ isms collected in the R/V Thomas Washingron . of these stomachs contai ned onl y well the neuston tows or di p-netted from The only definitive published record digested Halobclles remains, but the the surface water were offered to the of predato rs of Halobates is one by heavily cuticularized legs are easi ly Haloholes kept in an aquarium on Ashmole and Ashmole (1967), who recogni zable by their black colo r. In board the ship. These insects were carried out a very detailed study on two other samples. the in sect' bodies. never seen to feed on Phy\(//ia, Velello, the feeding ecology of seabirds of too. were still recognizable. while in or Po rpila. They were, however, Christmas Island (a small tropical is the fifth sample some o f the Halobale.1 observed to feed on pontellid copepods. land in the central Pacific). and re specimens were still intact. (S ince the hyperiid am phipods, euphausiid . and corded these insects in the stomach sample size was so small no attempt myctophid larvae trapped on the sur contents of two (out of eight examined) was made to estimate the pro po rtion face fi lm . H ow often such animals be species of surface-feedi ng seabi rds. al volume of insects in the food of come caught in this way is not known, the blue-grey noddy. Procelslerna th ese seabi rds.) but I found many mall animals could cemlea, and the Phoenix petrel , Pl ero Di ssecti o ns of adult Halob({[es, be caught by simply pouring the con droma alba. Although fish and squid collected ali ve. have shown th at th eir tents of a plankton haul from one formed the mai n bulk of their food, body cavity i often filled with orange beaker to another. and presumably Halobates was found to be quite an colored lipids. suggesting th at they surf a nd spray could have the same important component of their diet. In may be a rich source o f food for u r effect in nature. It is also very likely a total of 95 a mples of regurgi tated face-feeding fi hes. H owever. the that Holohates could feed o n fioating food from Pt. alba, Halobates was stomachs of several fishes (Celllro fish eggs. which. duri ng some seasons. found in II sampl es. th ough it con brachlls brel'iroSlris, C. choerocepha a re fo und in great abundance in tropi stituted less than 0.5 percent of the IllS, and CYll1bolophol'lls sp.). caught cal and subtropica l waters. nfor total volume of food. Among 34 P. in neuston nets together with Halo tunately, suitable fish eggs were not eerulea samples studied. 23 contained bales in the N orth Paci fic Gyre (Iat. available for feeding experiments dur remains of Halobales. which in this 28 ° N. long. 155 ° W ). contained no ing the recent expedition. The insects case constituted as much as 7 percent insect remains. Halobales remains Table 1.-Collecting data on seabird stomach by volume. have been found in a young Pacific samples. anchovy (Dr. A. S. Loukashkin. Cal I recently obtai ned from the Smith Species sonian Institution 20 samples of ifornia Academy of Sciences, San Field Ha/o- Number stomachs belongi ng to three species of Francisco: per onal communicatio n) Date Locality bates surface-feeding seabirds. the white and al 0 in the stomach of a SCII'CIiI1- Gygls alba 5872 18 Feb 66 l1 ° 03 ' S 171 °06'W tern Gygis alba. Procelslerna cerulea, ella siill1 collected in J akarta Bay (Dr.