Vexing question on fisheries research: The study of cephalopods and their parasites

9 Pages·2001·4.5 MB·English

by  Santiago Pascual

©
SociedadEspañola deMalacología Iberus, 19 (2): 87-95, 2001
Vexing question on fisheries research: the study ofcephalo-
pods and their parásitas
Un asunto embarazoso en investigación pesquera: el estudio de los
cefalópodos y sus parásitos
Santiago PASCUAL*^ andÁngel GUERRA**
Recibidoel10-111-2001.Aceptadoel7-IX-2001
ABSTRACT
For the beginning of this century it is evident that support for research will be increasingly
dependent upon the results ofthot research having relevance to society's needs and public
benefits. Within this web and coupled with the transfer of scientific knowledge is the
opportunity to more effectively explain the society the benefits it receives for its investments
in research. This viewpoint paper enlighten the general public on the scientific, industrial
and commercial relevance of the research on cephalopods and their parasites. In a com-
parative analysis with other commercially-important taxa, a historical negligible financial
support for research on diseases in this important animal group was noted. Because of
that policy-makers on Fisheries Research should balance this public debt in the future.
RESUMEN
En el comienzo de este siglo es evidente que el apoyo a la investigación se incrementará
en función de la relevancia que para las necesidades de la sociedad y de los beneficios
públicos se obtenga de los resultados de dicha investigación. En este contexto y paralela-
mente a la transferencia de conocimientos científicos, surge la oportunidad de explicar
más eficazmente a la sociedad los beneficios que recibe de su inversión en investigación.
El punto de vista de este artículo ilustra al público en general sobre la relevancia cientí-
fica, industrial y comercial de la investigación de los cefalópodos y sus parásitos, así
como de la histórica e insignificante financiación destinada a la investigación de las
enfermedades en este importante grupo animal. Un análisis comparativo con otros taxo-
nes comercialmente importantes, sugiere que los gestores de la política de Investigación
Pesquera deberían equilibrar esta deuda pública en el futuro.
KEYWORDS: cephalopod, parasite,fisheriesresearch.
PALABRAS CLAVE: cefalópodo,parásito, investigaciónpesquera.
INTRODUCTION
Cephalopods are fast-growing car- ecosystems (Clarke, 1996). Moreover,
nivorous molluscs that play an impor- cephalopod stocks are of great interna-
tant role in the trophic webs of marine tional importance in commercial fishe-
* Área de Parasitología, Grupo PB2, Facultad de Ciencias del Mar. Universidad deVigo, Apdo. 874, 36200
Vigo. Spain.e-mail: [email protected]
**InstitutodeInvestigacionesMarinas (C.S.I.C.). EduardoCabello6, 36208Vigo. Spain.
'Correspondingauthor
87
Iberus, 19 (2), 2001
Bivalves Cephalopods
%
36.95 17.95%
(1.77) Í0.86)
Seacrustaceans
%
5.85
(0.28)
Marinefishi
%
39.25
(1.88)
Figure 1. Percentagevalúes andratios (in parentheses, ¥10-6) whichrepresenttherelativescientific
effortbynominal catch unit foreachgroup ofspecies. Ratios arecalculated as the total numberof
publications that address parasitology and associated-pathology (mean for the period 1992-98:
source ofinformation in Biological Abstracts) and the nominal catch per group ofspecies (mean
numberfortheperiod 1992-98: sourceofinformationinF.A.O., 2000).
Figura 1. Porcentajesy ratios (enparéntesis ¥10-6) que representan elesfuerzo científico relativopor
unidaddecaptura nominalparacadagrupo deespecies. Losratiossehan calculado como número total
depublicacionessobreparasitologíaypatologíaasociada (mediadelperiodo 1992-98;fuente:Biological
Abstracts)y la captura nominalpara cadagrupo de especies (mediapara elperiodo 1992-98;fuente:
F.A.O., 2000).
ríes (BoYLE, 1990; Guerra, 1992; Josu- how do they find food, escape from
PEIT, 1995). World catch statistics record enemies, migrate, signal to one another
atotal catchof3.5millionmetrictonsin and reproduce, how does theirnervous
1999 (JosuPEiT, 2000), with a rate ofin- system function and what is their fis-
crease significantly greaterthanthatfor hery potential in terms of biomass. By
finfish species for the period 1970-1992 comparison, in the last decade marine
(BoYLE, 1990; Caddy, 1995). For the scientists have devoted very little time
combined marine catch, all categories, and money to the study ofcephalopod
between 1970-1992 there was anincrea- parasites and parasite-induced patho-
se rate of 2%per year. In contrast, for logy in wild and cultivated popula-
cephalopods, the rate of increase over tions.
the same period averaged 8% per year.
Because oftheirimportance as ahuman
food resource (Pierce and Guerra, SCIENTIFICPRODUCTIVITY
1994) and because cephalopods have
proved to be valuable as experimental Among 700,000 scientific papers a
animáis forbiomedical andbehavioural year published around the world (see
research (Gilbert, Adelman and Ar- Scientific Citation Index), alm.ost
NOLD, 1990; Abbot, Williamson and nothing is written on cephalopod disea-
Maddick, 1995; Hanlon and Messen- ses (Fig. 1). Based on current trends
GER, 1996), scientists have spent consi- there also appears to be an overall
derable time and money studying cep- decline in the number of recent papers
halopods in the last two decades: how that treat taxonomy and basic research
many species are there, how long do on parasites of other, non-commercial
they live, how fast do they grow, how marine invertebrates. This may be due
do they respond to changes in fishing in part to the loss of parasite workers
intensity andenvironmental conditions. (specially taxonomists) through lack of
Pascualand Guerra: Study ofcephalopods and theirparasites on fisheries research
funding support or redirection of rese- how few researchers there are in the
arch efforts to the study of human pat- field.
hogens or ecological studies. Neverthe-
less, despite the obvious scarcity of THE SPANISHPOLICY
scientific effort, recent world hterature
has stressed the important role of In this context, we may look at the
squids, cuttlefishes and octopuses as Spanish situation which is comparable
reservoirs for all taxa ofmarine eukario- with other fish-catching countries in
tic parasites at both macro- and micro- Europe. Spain is the fifth largest cepha-
geographic sampling levéis (Hochberg, lopod consuming country in the world,
1990; Pascual, Gestal, Estevez, Rodrí- the first in Europe. In Spain cephalo-
guez, Soto, Abollo and Arias, 1996). pods represent animportant component
Most large free-living, mature cephalo- of the diet (4 Kg./inhabitant/per year),
pods carry some microscopic (viruses, yet no financing has been directed at
bacteria, fungi, protists) and macrosco- research on cephalopod parasitic disea-
pic parasites (metazoans) in almost all ses. Although over 4 million US $ per
their tissues and organs (Hochberg, year is assigned by Plan Nacional de
1990). This author, in an extensive Investigación y Desarrollo (Comisión
survey ofthe Hterature, record a total of Interministerialde CienciayTecnología)
225 parasite species in cephalopods to Research and Development (hereafter
world-wide. Since the Hanlon and RandD) to finance research activities
FoRSYTHE (1990) review on diseases and projects on Marine Science and
caused by microorganisms and the Technology, nothingwas assigned to the
Hochberg (1990) contribution on disea- investigation of cephalopod diseases in
ses causedbyprotistans and metazoans, the last decade. In this context, itis rele-
only 32 scientificpapershave dealtwith vant that cephalopod landings in Spain
cephalopod pathology. Ofthese, only 16 (averaging 110,000 metric tons per year
papers have been published in interna- for that period) contributed 308,000,000
tional scientificjournals, 4ofthesebeing US $ per year to our domestic economy.
chapter reviews within a zoological It seems quite remarkable that at least a
and/or fisheries biology context. small portion of the money derived
Despite the fact that cephalopod lan- from the fishery and manufacture pro-
dings have increased over the period cesses profits should be returned to
1992-1998, the number of people invol- support research on diseases of wild
ved in this field and the number of and cultured cephalopods. The absence
papers on cephalopod pathology is still of support for a technology transfer
remarkably low. In fact, the scientific mechanismclearlyindicatesthattheres-
effortdealingwithcephalopod parasites ponsibilities of the Spanish research
and associated pathologyrelatedtorela- fundingagenciesdoesnotcloselyfollow
tive nominal catch by group of species current fishing trends to support both
account less than 54% of that on parasi- established and emerging activities as
tic diseases of other commercially- the management of the ecological
important invertebrates (bivalve impact ofparasitism inwildlife and cul-
molluscs) and marine fish (Fig. 1). Why tured populations are (Grenfell and
isthis so? Gulland, 1995). In other words, this
Diversity of hosts versus number of indicates that in this field the Science-
researchers is a key factor. Thus, there Technology-Industry Spanish System
are approximately 700 species of cepha- (STISS) still has an imbalance between
lopods and veryfewresearchers compa- the scientific andproductive spheres.As
red with about 100,000 species of fishes regards STISS (involving parasitolo-
and numerous researchers. Neverthe- gists), it appears to be particularly sti-
less, the scientific productivity with mulated by the production of scientific
regard to papers on cephalopod parasi- publications and thus, the most impor-
tes actually is not too bad considering tant yardstick to promote researches is
89
Iberus, 19 (2), 2001
the number of publications within the diseases in the 1990's. Such a brief
Scientific Citation Index (SCI). STISS synopsisisurgentlyrequiredinthelight
lacks, however, of sufficient support to of the many advances which have been
employ young trained scientists in rese- madeutilizingnewtechniques.
arch activities and seems to be insuffi- Although older reports of infectious
ciently motivated by the food technolo- diseases emphasized description and
gical and sanitary aspects that imply a systematic classification of cephalopod
suitable development of the research on parasites, considerable confusión exists.
parasitic-caused cephalopod patholo- The identifications of the parasites and
gies. In the case of Food technology, sometimes even the hosts are often in
STISS have an important drawback doubt, with high synonymy rates (cióse
which is the low level of interest of to 70%) for numerous parasitic nominal
many prívate companies to deal with species identified by light microscopy
the necessary innovation of its products (Pascual, Arias and Guerra, 1995;
or processes. Consequently financial Mattiucci, Nascetti, Cianchi, Paggi,
and human resources being assigned by Arduino, Margolis, Brattey, Webb,
public policy and the prívate sector to Dámelio, OrecchiaandBullini, 1997).
develop research activities aimed at a Researchers trained in modern techni-
scientific assessment of the impact of ques, new trends in systematic, and
infectious processes in cephalopod improved technologies for detecting
stocks are patently insufficient. This and defining species have allowed us to
situation is made worse when public elucídate and re-evaluate the taxonomic
organizations or businessmen have to status and the host-parasite relations-
solveseriousproblemsrelatedtothetre- hips of many already described species.
atment and control ofcephalopod disea- For example, recent papers dealingwith
ses at present day in industrial proces- scanning and transmission electrón
ses. And the situation will be still worse microscopy (SEM and TEM) and atomic
if, following the successful results in forcé microscopy (AFM) studies have
experimental rearing of planktonic showed how much a combination of
common octopus from hatching to set- increased depth of field, resolution and
tlement (Villanueva, 1995) and on magnification is needed in the Identifi-
growing of this species in floating cages cation and examination of the morpho-
(Hebberecht, 1996; Moral-Rama, 1996; logy microtopography, topometry and
Guerra, unp. data), the industrial cellbiology ofcephalopod parasites and
culture of the octopuses become a busi- the host-parasite interface (Gestal,
ness that rent good profits. In this Pascual, CorralandAzevedo, 1999).
regard, a recent study by the Industrial Additionally, our understanding of
Research and Development Advisory theepizootiology (whichinvolvesinves-
Committee of the European Commis- tigations on the demographic infection
sion (1994) warns ofthe obvious danger valúes, patterns of transmission, and
ofeconomic stagnation, unless there is a disease control) of many parasitic
greater coordination between the pro- species in cephalopods is severely ham-
ductive system (extraction or produc- pered by morphological characters of
tion, processing and marketing of the difficult interpretation The existence of
resource) and the much-needed scienti- morphologically identical cryptic
fic environment (comprising the RandD species and parasitic races or morphoty-
groups). pes which can reflect selection pressure
rather than taxonomic affiliation are
problems faced by all taxonomists, but
FUTURE RESEARCHDIRECTIONS present particular difficulties because of
theplasticityofbody structures inendo-
In this article we should not forget parasites. Moreover, when histological,
some of the general trends emerging isolation and purification processes and
from the study of cephalopod parasitic parasitic dissection techniques are all
90
Pascualand Guerra: Studyofcephalopods and their parasites on fisheries research
needed to reveal diagnostic characters since it agrees with demographic para-
of some protozoan and metazoan ecto- meters observed duringspecial cephalo-
parasites, respectiyely, a high degree of pod disease surveys in the same área
skill (and training) is required. A (Pascual, 1996).
number of molecular techniques should Although an extensive literature
be developed to overeóme these pro- dealing with diseases and defence
blems and shouldbeappliedworldwide mechanisms is available for other com-
as useful taxonomic tools for parasite mercially-important moUuscs, little
detection andtheir speciesIdentification emphasis has been placed on the
incephalopods. defence mechanisms of cephalopods.
Diseases and pathology caused by Despite humoral and cellular defence
microparasites on wild and cultured associated responses having been des-
cephalopods have been reportad in a cribed for cephalopods maintained in
few cases (Hanlon and Forsythe, closed sea-water systems forbiomedical
1990; PoYNTON, Reimschuessel and studies or fattening against potential
Stoskoff, 1992;Gestal, 2000). However, bacterial pathogens (Hanlon and
it should be noted that in Spain, during Forsythe, 1990; Ford, 1992), the effects
the massive culture of paralarvae and of other microscopic and macroscopic
juveniles insystem crowding, highmor- parasites on phagocyte capabilities,
talities rates have been assigned to inflammation, wound healing and func-
several environmental factors including tional morphology of cephalopod hae-
diseases by bioagressors (Gestal, mocytes has not been investigated in
Abollo and Pascual, 1998). Further- depth. The study of inmunobiology of
more, despite cephalopod macroparasi- cephalopods is just starting (Malham,
bteisonttyspi(caHlOlCyHhBaEvReG,be1e9n90c)o,nhsiisdteorpaadthsoylmo-- B1E9S9,6;1M99a7)l.hAambe,tDteurnuhnadmerastnadndSiencgomo-f
gical analysis on heavily parasitized host defence reactions in cephalopods
cephalopods revealed the destruction of would also help to avoid or control out-
vital organs and potential loss of their breaks of parasitic diseases in commer-
functionality (Pascual, 1996; Abollo, cial mariculture conditions where
Gestal, López, González, Guerraand animal densities, intensive husbandry
Pascual, 1998). Unfortunately, in the and stress may increase occurrence of
past although attentionhasbeenpaid to parasitic disease. Because cephalopods
thepresenceofparasiticdiseasesinwild are afood source inmany regions ofthe
cephalopods, most of the early studies world, the effects of parasitic infections
can be classified as single or short-time on the biochemical composition and
observations. Seasonal and continuous physiological characteristics including
long-term parasite studies are missing, condition, growth rate, nutrient assimi-
resulting in the current absence of relia- lation and protein/energy ratio of cep-
ble data to be used in comparative halopods in nature and culture systems
analysis. These data will improve our shouldalsobeevaluated.
knowledge about whether present Most wildlife parasitic diseases have
disease prevalence in wild exploited been investigated via pathological post-
cephalopod stocks exceed natural pre- mortem examinations, or by producing
valence, change with abiotic parameters lists of parasites identified in small
and/or are influenced by host exploita- samples of hosts. There have been few
tion rates and discarding practices. attempts to assess the impact of a
These studies will be also very useful disease at the population rather than
for mapping the existence of hot-spot individual level, or to describe the dis-
áreasbyusing the grid systems ofInter- tribution of the disease agent in a
national Fishery Organisations. To manner sufficient to understand its epi-
obtain base-line data, cephalopod demiology. Pascual, Gestal and
disease recording in standard stock- Abollo (1997) considered the statistical
assessment surveys is potentially useful distribution of parasites throughout the
91
Iberus, 19 (2), 2001
host species population, and confirmed but when large-scale culture in high
thenegative effectofgilí macroparasites density groups was initiated, fatal infec-
on the condition of exploited ommas- tious diseases occurred (Hanlon,
trephid stocks. That study clearly sug- Forsythe, Cooper, Dinuzzo, Folse
gests the existence of causal relations- ANDKelly, 1984; Gestaletal., 1998). In
hips, expressed in negative modifica- Spain, where cephalopod mariculture is
tions of ecological potential, between changing from experimental to indus-
parasiticinfection and cephalopod stock trialsphere, implementationofprocedu-
productivity. Finally, aneconomiclossis res for detection and monitoring the
present (Pascual, González and pathology and parasitic diseases on a
Guerra, 1998). Although further bio- widescaleintheongrowingcephalopod
chemical data on infected and parasite- industry should be common, together
free cephalopod tissues should be recor- with other yet established diseases
ded to ascertain the physiological inte- assessment policy (e.g. on cultured
ractionsbetweencephalopods and para- fishes andbivalvemoUuscs).
sitic infections, parasites may have a Furthermore, parasitoses in cephalo-
considerable effect on infected stocks or pods appears not only as an important
individuáis, as has been recently noted problem in the management of infected
by Gestal (2000). Less obvious to most stocks, but also a zoonotic problem
fisheries scientists is the important role during food-processing. Larval stages of
of parasites in regulating the general macroparasites are found in many
"well-beingor fitness" ofthehostpopu- species of squids, cutlefishes and octo-
lation (i.e. in regulating host abundance puses, which are of commercial impor-
or fecundity). To this end, we should tance. The appearance of parasites
attempt to blend mathematical models makes cephalopods unsightly and
for host-parasite relationships with unappealing to consumers. Moreover,
those used by fisheries biologists to although several species of anisakid
determine how parasites can affect the nematodes and trypanorhynchcestodes,
dynamics of exploited cephalopod at the larval stage, canbe pathogenic if
populations, following the seminal arti- consumed in raw or improperly cooked
cles of Crofton (1971), Anderson and cephalopod dishes, few cases of illness
May (1978, 1979), Sindermann (1987), byhelminths inmanhavebeenreported
DoBSON AND May (1987) and Grenfell inSpain (Abolloetal., 1998).
andGulland (1995). Thecomplications Cephalopod ecologists may also
introduced by the presence of parasitic benefit by applying new ideas such as
disease will in general further increase the study of the host-parasite systems.
the levéis of uncertainty that cephalo- Pascualand Hochberg (1996) revised
pod fisheries managers have to contend the use of parasites as non-intrusive
with (Beddington, 1984), this mostly in natural tags of cephalopod hosts in fis-
relation to cephalopod condition and its heries science. Piotozoan and metazoan
potential fecundity (i.e., its recruitment parasites have been used to assess the
dynamics). status of current stocks of several com-
Roughly 10% of the known species mercially-exploited cephalopod species.
ofliving cephalopods (i.e. over 80 ofthe Few examples of the trophic status of
700 known species) have been either cephalopodswithinfood webs and their
maintained, reared or cultured in capti- parasitecommunitystructureareavaila-
vity (BOLETZSKY AND Hanlon, 1983). ble from the literature. The quantifica-
The vast majority of these 82 species tion of genetic variation obtained from
(representing 30 genera) have mainly allozyme frequencies among or within
been maintained or reared, while 12 populations of larval anisakid nemato-
species (7 genera) have been cultured des (i.e., the parasite most frequently
through their entire life cycle (Hanlon, employed as tags for marine organisms
1987). No signs of diseases were ever and the most commonly encountered
observed during small-scale production. macroparasite in cephalopods) can
92
Pascualand Guerra: Studyofcephalopods and theirparasites on fisheries research
provide valuable data on trophic rela- fits they receive for their investments in
tionships and stock identity of most research (Murrell, 1996). Bearing in
wild cephalopod stocks. mind all the comments above, we feel
Through workshops and symposia that few cephalopod parasitologists
CIAC (Cephalopod International Advi- have succeeded well in communicating
sory Council) aims to present current many aspects of scientific and technical
research and to stimulate and promote knowledge, but they have been less
future research. Among the almost 40 effective in enlightening the general
symposia and workshops on cephalo- public and prívate partnerships on the
pods held by fisheries biologists from societal valué and economic relevance
1973, the 1996 workshop on cephalopod of their research contributions. To over-
parasites developed on behalf of Com- eóme this it is imperative to encourage
mission Internationale pour l'Explora- public and prívate managers, fisheries
tionScientifique dela MerMéditerranée scientists and parasitologists to contact
(CIESM) by Boletzsky and Hochberg each other to go one step further in the
(Laboratory Arago, Banuyls-sur-mer, 2ithcentury.
France) was the first attempt to provide
on the parasite diseases processes of
wild and reared cephalopods. The con- ACKNOWLEDGEMENTS
tents ofthis workshop established itself
as the main introductory handbook of We thank Comisión Interministerial
working techniques on cephalopod de Ciencia y Tecnología (CICYT) for
parasitology. their financial support (CICYTMAR95-
Today is well-established that 1919-C05). Thanks also are extended to
support for research is increasingly an anonymous review and all members
dependent upon the results of that rese- of the research groups University of
arch having relevance to society's needs Vigo-PB2 and Instituto de Investigacio-
and public benefits. Coupled with the nes Marinas (ECOBIOMAR-CSIC) for
transfer of knowledge is the opportu- aid and numerous helpful suggestions
nity to more effectively explain to fishe- for a decade of fruitful joint collabora-
ries managers and companies the bene- tion.
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